KiKAD is a very effective tool for the design of Printed Circuit Boards (PCBs). The tool has numerous characteristics along with capability of designing PCB layout such as ability of generating Bill of Materials, Schematics design, and auto conversion of schematics to PCB layout etc. However, this article is comprised of all relevant information required for the acquisition of Bill of Material (BOM) having information of all relevant Component Placement List (CPL). The Component Placement List is also sometimes referred to as Pick and Place or Centroid file when use of the tool KiCAD is considered. The following is detailed method for the generation of Bill of Materials along with Component Placement List.

The Generation of Bill of Material Files

The Bill of Materials is having required information about the entire electronic components which are used in the layout of PCBs. The BOM is also having information of the exact locations where each of the component has been placed. Considering an example of certain PCB having various components at different positions such as T1, R1, and C1 etc. being printed on the layout of PCB, however the manufacturer is not aware of the component being used on these positions. Therefore, BOM list will enable the manufacturer to have an idea of the component being used on these locations being transistor, capacitor, resistor, or inductor etc. The BOM is very important when it comes to the assembly process. However, bear in mind that BOM is a simple excel or text file which has information of all components and its exact location. In case if you don’t like the auto generated format of KiCAD, you can also make the BOM in excel spread sheets yourself with your convenience. The image below is illustrating a simple BOM list extracted from KiCAD.

The image above has a total of four columns i.e. Comment, Designator, Footprint, and LCSC Part Number. The Comment is indicating the parts used in the PCBs with its actual values. It describes each component in detail with exact values such as a capacitors C1, C2, C3, and C4 having same values of 0.1uF. However, some of other information must also be catered such as tolerance and voltage allowing capacity etc. Designator is describing the components which are placed at different points. For example, capacitors of values 22pF are placed at points C5, and C6. PCB Footprint is of great importance because the packages in SMD parts are coming in different sizes, and hence the assembling engineer must be knowing which package is going to be best fit in the Printed Circuit Board.

Therefore, the assembly engineer must be aware of the different sizes SMT which are used in the PCB design such as 0603, 0805, and 1206 etc. LCSC Part Number is the column having information for speeding up the process of assembly of PCBs and getting precise results. Each component of the PCB has a unique number through which it is recognized and there is usually a stock of components with each PCB manufacturer. Therefore, this unique component number is very keen in recognition of the component being used and if still there exist any ambiguity then the component unique number might be searched in the library.

The following image is illustrating the Component number C382097 to be a capacitor having value of 1nF and is to be placed at point C1 on the PCB.

For the purpose of exporting the Bill of Materials from KiCAD tool, you are required to click or go to the script of Arturo’s BOM export. You can easily find it on the web. Download the script which is usually in ZIP form and then unpack it. The image below is illustrating way to acquire the Arturo’s BOM script, downloading, and installation of the script.

After the installation of the script, open it and then click on the option of Export BOM for the specific PCB required. You have to add the BOM script in to the KiCAD PCB file which is opened. From the command window of the KiCAD tool, change the command to %O.csv from the command %O and then click on the generate BOM for its generation. This is going to generate the required BOM which is required for the PCB Assembly process. The figure below is demonstrating the method described above for changing the command and then generation of BOM.

The Generation of Component Placement List from KiCAD Tool

As described earlier that the Component Placement List which is also known as Pick and Place list of the component can also be generated from KiCAD tool. Therefore, for CPL list acquisition, first of all the PCB editor needs to be opened. By clicking on the “File” option in the PCB editor, go to the option “Fabrication Output” and then click on the “Footprint Position”. The footprint position is in .pos format. You have to export the file and then change it with the settings shown in image below.

First of all you need to change the format of the file to “.csv”, change the required units in to “mm”, and “One file per side”. After this, you have to select the footprint selection to “with INSERT attribute set”. At the end you have to click on the all options given at bottom of tab i.e. “all, errors, warnings, infos, and actions”. At the end click on “save report file”, however give proper location where the file has to be saved.

For having a compliance with the RayPCB SMT, you are required to edit the Component Placement List file libreoffice Calc. or excel format. Therefore, for the purpose you are required to do the changes as described below.

First of all you have to ref to the designator of PosX to that fo Mid X PosY to Mid Y Rot to Rotation Side to Layer, before making the export form the KiCAD tool.

After the modification of the header, you will get the file with following format illustrated in image below.

Introduction

KiCAD is a popular open-source Electronics Design Automation (EDA) software suite used for Printed Circuit Board (PCB) design. It provides schematic capture and PCB layout functionality along with various other features for electronics engineers. One of the most useful features of KiCAD is its ability to generate manufacturing output files like centroid files, bill of materials (BOM), Gerber files, etc. These files are essential for PCB fabrication and assembly. In this article, we will focus on the method to generate two key output files from KiCAD – the centroid file and the BOM.

Centroid File

The centroid file provides the center coordinates or centroids of all PCB footprints. It is required by the pick and place machine to accurately place components on the PCB board during assembly. Here are the steps to generate the centroid file in KiCAD:

1. Creating Footprints with 3D Models

The first step is to assign 3D models to all the footprints used in the PCB layout. The centroid data is extracted from these 3D models. KiCAD includes many pre-defined 3D models and you can also create custom models.

2. Enabling 3D Viewer

The 3D viewer must be enabled in PCBNew to render the board with 3D models for generating the centroid file. This can be done by going to Preferences > 3D Viewer and checking Enable 3D Viewer.

3. Running the 3D Generator

Go to Tools > Generate Fabrication Output. This will open up the fabrication output job editor. Under the General Options tab, enable the following:

• Force recreate files
• Use complete suffix
• Use 3D models
• Generate centroid info

This will regenerate all the manufacturing files including the centroid data when the job is run.

4. Executing the Job

Click on the Generate button and the fabrication job will be executed. This will generate centroid info in a file named <filename>_centroid_info.csv along with other fabrication outputs.

The centroid file can be found under the main project folder. It contains a list of all footprints along with their reference designator, center X, Y coordinates and rotation angle. These coordinates should match the 3D models visible when the 3D viewer is enabled.

Bill of Materials (BOM)

The BOM or bill of materials is a list of all the components used in a PCB along with key information like reference designator, description, quantity, etc. The BOM acts as a shopping list for purchasing components for production. The following steps describe how to generate a BOM from KiCAD schematics:

1. Associating Components with Schematic Symbols

For each component in the schematic, make sure to associate it with a schematic symbol and provide a unique reference designator. This information will get populated in the BOM.

2. Including Part Information

Add complete part information like manufacturer name, part number, description, etc. for each component in the schematic. This data can be entered in the component’s properties window.

3. Assigning Field Names

KiCAD allows mapping the part fields like description, part number, etc. to specific column headers in the BOM. This can be configured in the schematic editor preferences.

4. Generating Netlist

Before generating BOM, you need to create a netlist to synchronize the schematic and PCB. Go to Tools > Generate Netlist to create the netlist file.

5. Using Component Class Dialog

The component class dialog in PCBNew is used to classify components into various types like integrated circuits, resistors, capacitors etc. This classification can be used to group components in the BOM.

6. Generating BOM

Finally, go to Tools > Generate Bill of Materials to create the BOM. This will generate a .csv file containing the reference, quantity, description, part number and other fields for all components.

The BOM can be customized further by editing the template or XSLT stylesheet used for BOM generation. Fields can be added, removed or rearranged as per requirements.

Additional Points

Here are some additional points to keep in mind while generating BOM and centroid files:

• The fabrication output generator provides many options to customize the outputs as per board house requirements.
• The Reference Reference column can be used in the BOM to cross-reference components from schematic to PCB.
• The position and rotation column in BOM provides placement info that can be used during assembly in combination with the centroid file.
• Multiple BOMs can be generated with different grouping and filtering criteria.
• The component grouping feature is useful for organizing BOM by component types.
• Scripting can be used to automate running the fabrication output generator for quick BOM/centroid file creation.

Conclusion

Generating manufacturing files like BOM and centroid data is crucial before sending a PCB design for fabrication and assembly. KiCAD’s fabrication output generator provides an efficient one-step solution to create these files from the PCB projects. Configuring the right options and customizing the output templates allows generating high quality BOM and centroid files that can be readily used by PCB manufacturers. This automated documentation saves significant amount of time and effort while also minimizing errors during the manufacturing process.

Frequently Asked Questions

Q1. What is the importance of a centroid file?

A1. The centroid file provides the center point coordinates of all PCB footprints which are required for accurate component placement by pick and place machines during assembly.

Q2. Can BOM be generated without creating a PCB layout?

A2. Yes, BOM can be created directly from the schematics before PCB layout by using the Generate Bill of Materials tool in EESchema.

Q3. What is the use of component grouping in BOM generation?

A3. Component grouping allows classifying components into categories like ICs, resistors, capacitors etc. This groups components in the BOM making it easier to read and analyze.

Q4. How can the BOM be customized in KiCAD?

A4. BOM can be customized by editing the BOM template and XSLT stylesheet used for generation. This allows changing fields, ordering, grouping etc. as per requirements.

Q5. Is it possible to generate multiple centroid files for different PCB assemblies?

A5. Yes, multiple centroid files can be generated by creating assemblies of boards and footprints. The 3D generator can then output separate centroid files for each assembly.

Introduction

Diodes are semiconductor devices that allow current to flow in only one direction. They have unique electrical characteristics that make them useful for a variety of applications such as rectification, switching, clamping, etc. One important parameter that defines the behavior of a diode is its resistance. However, the resistance is not constant and varies with the type of current – Direct Current (DC) or Alternating Current (AC). In this article, we will explore the difference between DC and AC resistance of a diode and the relationship between the two.

DC Resistance

The DC resistance of a diode refers to the resistance offered by the diode to a direct current. It is the ratio of the applied DC voltage across the diode to the resulting DC current through it. Some key points regarding DC resistance:

• DC resistance arises from the bulk resistance of the semiconductor material used to make the diode. It is relatively low, typically just a few ohms.
• DC resistance stays fairly constant until the diode starts conducting current in the forward biased condition.
• Once the diode starts conducting, the DC resistance drops exponentially as the current increases.
• DC resistance is low in forward bias and very high (ideally infinite) in reverse bias.
• DC resistance can be derived from the diode’s I-V curve and is equal to the inverse slope of the curve in the linear region before the diode turns on.

DC Resistance vs Forward Current curve for a diode showing low constant resistance initially followed by exponential decrease upon conduction.

AC Resistance

AC resistance refers to the resistance offered by a diode to alternating current. It arises primarily due to the junction capacitance of a diode and differs significantly from DC resistance. Some key points:

• AC resistance is frequency dependent and varies with the frequency of the AC signal applied.
• At very low frequencies, AC resistance is high and nearly equal to DC resistance in reverse bias.
• As frequency increases, AC resistance starts decreasing due to charging and discharging of junction capacitance.
• The junction capacitance provides a low reactance path for AC at higher frequencies. Hence, AC resistance decreases.
• At very high frequencies, AC resistance approaches a minimum value known as dynamic resistance.

Variation of AC Resistance with frequency for a diode showing decrease with increase in frequency.

Relationship between DC and AC Resistance

From the characteristics described above, we can summarize the relationship between DC and AC resistance as follows:

• At very low frequencies, AC resistance ≈ DC resistance in reverse bias
• As frequency increases, AC resistance decreases while DC resistance remains unchanged
• DC resistance represents a lower limit for AC resistance but AC resistance can never fall below DC resistance
• At very high frequencies, AC resistance approaches dynamic resistance which is higher than DC resistance
• DC resistance is determined by the bulk resistance of the diode material
• AC resistance depends on frequency and junction capacitance along with bulk resistance

Therefore, we can conclude that AC resistance is always greater than or equal to DC resistance for a diode. But the exact relationship varies depending on the frequency. The AC resistance equals the DC value only under static conditions at low frequencies. As frequency increases, the AC resistance starts decreasing due to capacitive effects while the DC resistance remains constant.

What causes the difference between DC and AC resistances?

The key factors that cause the DC and AC resistances to be different are:

1. Junction Capacitance

• Every PN junction has an inherent junction capacitance which depends on the area of the junction, doping levels and voltage applied.
• In reverse bias, the depletion region at the junction acts as the dielectric of a parallel plate capacitor causing capacitance.
• Under AC, this capacitance provides a reactive path for the current to flow by charging and discharging.
• Hence, AC resistance decreases with increase in frequency due to capacitive reactance.

2. Minority Carrier Injection

• Under DC, only majority carriers contribute to conduction which depends on the bulk resistance.
• But in AC, minority carriers also get injected into the junction when it is forward biased during one half cycle.
• These extra carriers increase the conductivity and lower the dynamic resistance under AC conditions.

3. Temperature Effects

• DC resistance has a positive temperature coefficient – increases with temperature due to higher lattice vibrations.
• But AC resistance and capacitance are negatively affected by temperature rise.
• So heating causes DC resistance to increase but AC resistance decreases due to reduced capacitive reactance.

4. Non-linear I-V Characteristics

• The diode does not follow Ohm’s law. Instead it has an exponential I-V relationship in forward bias.
• So AC resistance becomes dependent on the operating point unlike the DC case.
• Significant non-linearity causes DC and AC resistances to diverge.

5. Transit Time Effects

• At high frequencies, the diode’s transit time for carriers starts affecting the AC resistance.
• Transit time acts as a small inductance, thereby increasing impedance.
• Thus transit time effects also contribute to the difference between DC and AC resistances.

How are DC and AC resistances specified in diode datasheets?

Diode datasheets often provide the following resistance specifications:

Additional details provided:

• DC resistances are specified at a particular forward current and reverse voltage.
• Dynamic resistance is specified at a test frequency, usually 1 MHz.
• Junction capacitance values are provided as a function of reverse voltage.
• Forward resistance is represented by slope of forward I-V curve.
• Temperature dependence of resistances is also specified.
• Switching times and transit times indicate high frequency limitations.

By combining the DC resistance, junction capacitance and other parameters, the AC resistance at different frequencies can be estimated.

Applications exploiting the DC and AC resistance properties

The difference between the DC and AC resistances of a diode is useful for the following applications:

Rectification

• Low DC resistance in forward bias allows high DC currents for rectification.
• High AC resistance in reverse bias blocks reverse AC voltages.

Switching and Clamping

• Fast switching between low and high resistance states allows using diode as switch.
• Varying AC resistance helps in waveform clamping and shaping.

Radio Frequency Detection

• Variation of AC resistance with frequency is useful for detection of RF signals.
• Diode resistance matches to load at signal frequency for good impedance matching.

Reverse Leakage Control

• High DC resistance in reverse bias minimizes reverse saturation current.
• This reduces leakage and improves performance.

Temperature Sensing

• DC resistance change with temperature is utilized for sensing.
• AC resistance change is relatively lower, hence does not affect temperature sensitivity.

Conclusion

To summarize, DC and AC resistances are two different diode parameters that are related but not equal in magnitude. DC resistance represents the static bulk resistance while AC resistance is frequency dependent due to capacitive effects. AC resistance equals DC resistance only at very low frequencies and starts decreasing as frequency rises. The difference arises due to factors like junction capacitance, minority carrier injection, temperature effects and transit time. Diode datasheets specify DC resistances along with parameters like capacitance and transit time to allow estimating AC resistance. The variation between DC and AC resistances is exploited in applications like rectification, switching, clamping, RF detection and temperature sensing. Proper understanding of the relationship between the two resistances is therefore important for selecting the right diode for different applications.

Frequently Asked Questions

Q1. Why does AC resistance decrease with increase in frequency?

Ans: AC resistance decreases with increase in frequency because of the junction capacitance of the diode. At higher frequencies, the capacitive reactance XC becomes low, providing an alternate lower resistance path for AC current to flow through capacitance by charging and discharging effect.

Q2. Is AC resistance affected by temperature?

Ans: Yes, AC resistance is affected by temperature. Increase in temperature causes the junction capacitance to decrease due to increase in intrinsic carrier concentration. This causes the AC resistance to increase with temperature.

Q3. Is AC resistance higher or lower than DC resistance?

Ans: AC resistance is always higher than or equal to DC resistance. It equals DC resistance only at very low frequencies when capacitive effects are negligible. At higher frequencies, AC resistance becomes lower than DC resistance due to capacitive reactance but never falls below the DC resistance value.

Q4. Does a diode follow Ohm’s law?

Ans: No, a diode does not follow Ohm’s law. It has an exponential I-V relationship in forward bias due to its PN junction properties. This non-linear V-I curve causes the AC resistance to become dependent on the operating point.

Q5. Why does transit time affect AC resistance?

Ans: At high frequencies, the diode’s transit time for charge carriers starts affecting the AC resistance. Transit time acts as a small inductance that increases impedance and hence increases AC resistance at very high frequencies.

Introduction

Signal reflection occurs when an electrical signal encounters an impedance discontinuity along a transmission line, causing a portion of the signal to be reflected back towards the source. This can lead to interference issues like ringing and noise in high speed PCBs. Properly matching trace impedance and terminating lines helps avoid reflections. This article provides an overview of signal reflection causes, effects, calculations, and design techniques to mitigate reflection problems in circuit boards.

What Causes Signal Reflection?

Reflection arises from an impedance mismatch. Wherever the signal line characteristic impedance Z0 changes along its path, some incident signal energy will reflect while the remainder transmits through.

The most common sources of mismatch and reflection in PCBs include:

• Trace impedance change from differences in width, thickness, or dielectric
• Stub traces that branch off from main signal path
• Components with mismatched terminal impedances
• Improper termination at load end of line
• Vias that transition between layers with different stackup materials
• Discontinuities at connections like connectors or IC pads
• Damage like cracks or cuts in a trace

Minimizing impedance discrepancies along the signal path reduces the likelihood of reflections.

Reflection Effects

When reflections occur on a signal line, several detrimental effects can arise:

Ringing – multiple reflections lead to resonances and ringing artifacts on the signal

Noise – inter-symbol interference from reflected signals appearing at unintended times

Overshoot – excessive peak voltage from constructive interference between incident and reflected waves

Undershoot – sagging voltage dips caused by destructive signal interference

Jitter – timing variations resulting from impedance discontinuities

EMI – radiated interference caused by resonances along the transmission path

Signal Integrity – reflection noise that can degrade receiver performance and contribute to bit errors

Power Integrity – impedance issues that compound power distribution network resonances

Proper impedance control minimizes these reflection issues which are problematic in high speed digital systems.

Transmission Line Theory

To understand and model reflections, we must consider the transmission line model of interconnects:

Where:

• R = Resistance per unit length
• L = Inductance per unit length
• G = Conductance per unit length
• C = Capacitance per unit length

Together R, L, G, and C define the characteristic impedance Z0 of the line:

When Z0 is constant throughout the path, signals propagate without reflection. Wherever Z0 changes, reflection occurs according to the reflection coefficient Γ:

Where Z1 is the load or intermediate impedance causing mismatch. This model allows calculating reflection severity at each impedance discontinuity.

Reflection Calculations

The reflection coefficient quantifies the portion of signal reflecting back at a impedance change.

For example, consider a 50 Ω transmission line terminated into 75 Ω. Applying the reflection coefficient equation:

Γ = (Z2 – Z0) / (Z2 + Z0)

Γ = (75 Ω – 50 Ω) / (75 Ω + 50 Ω)

Γ = 0.2

This indicates 20% of the incident signal reflects back from the impedance mismatch. The remainder transmits through to the load.

Additionally, the voltage reflection coefficient ρ provides the amplitude of the reflected waveform relative to the incident wave:

ρ = (Z2 – Z0) / (Z2 + Z0)

So in this example, the reflected voltage wave will be 20% of the incoming signal amplitude.

These principles allow quantifying reflection severity for any impedance mismatch along a transmission path.

Avoiding Reflections During Routing

Several PCB routing techniques help reduce signal reflections:

Impedance Matching

• Maintain consistent trace width based on stackup dielectric to match target Z0
• Compensate for thickness changes with width tapers
• Use impedance calculators to design trace geometry

Use Ground Planes

• Reference to continuous ground layers stabilizes impedance
• Avoid routing over splits in ground planes

Minimize Trace Stubs

• Route with shortest connections between drivers and loads
• Avoid creating stub traces that branch off of signal lines

Symmetric Routing

• Equal trace lengths for complementary differential pairs
• Match component placements of differential pairs

Termination

• Properly terminate trace ends near load impedance
• Series terminate drivers, parallel terminate loads
• Avoid unterminated transmission line stubs

Careful routing practices eliminate unnecessary impedance discontinuities and reflections.

PCB Layer Stackup Design

In addition to routing, the layered construction of the PCB impacts impedance control:

• Minimize layer changes with vias – use direct routes where possible
• Maximize reference plane layers – avoid splits under critical traces
• Model reference plane interactions – maintain constant line environment
• Watch glassweave effects – model actual weave patterns
• Keep dielectrics consistent – use same materials for core, prepreg, solder mask
• Model various densities – copper fills can change local impedance

Simulating the actual manufactured PCB stackup is key to predicting impedance and reflections.

Via Design to Limit Reflections

Vias that transition between layers introduce impedance discrepancies and reflections:

• Model vias in layout tools and account for pad shapes
• Use smaller drill sizes to reduce Z0 change
• Avoid routing vias near sensitive crossover nodes
• Minimize signal layer changes
• Place ground vias adjacent to signal for shielding
• Backdrill or stub-eliminate unused via portions

Properly designing vias for the signal path impedance mitigates discontinuity effects at layer transitions.

Terminating Traces

Adding termination resistors absorbs incident signals, preventing reflections:

Source Termination

• Called series termination
• Resistor at source isolates driver from reflections

Load Termination

• Called parallel termination
• Resistor at load matches line impedance

Split Termination

• Combination of source and load termination
• Divides termination resistance value

Terminations should match line impedance and be located as physically close to endpoints as possible.

Simulation and Modeling

Validate designs through electromagnetic (EM) analysis of reflection severity:

• Model routed traces with actual geometry in layout tools
• Simulate across frequency range of interest
• Identify resonant ringing and reflection hotspots
• Evaluate effects of layer transitions, vias, stubs
• Verify location and value of terminations
• Tune layout to reduce resonances

Simulation provides insight to refine layouts by minimizing identified impedance mismatches before manufacturing PCBs.

Signal Reflection Mitigation – Frequently Asked Questions

Here are some common questions related to dealing with reflections in high speed board design:

What is the typical PCB trace impedance?

The most common impedance for signals lines is 50 ohms. This matches cable impedance and provides a good tradeoff between conduction losses and reflections.

When do reflections need mitigation?

Reflections must be addressed whenever fast edge rates under 1-2ns rise time are present on unmatched transmission lines longer than 1/10th wavelength.

How can reflections be observed?

An oscilloscope plots signal waveform ringing and noise caused by impedance discontinuities. Time domain reflectometry (TDR) tools also measure reflections.

Where should source termination resistors be placed?

Series resistors should be located as close as possible to the driver output pin or package to prevent resonances on the line prior to damping reflections.

What values are used for termination resistors?

Terminator resistance should match the trace characteristic impedance (typically 50Ω). Lower values attenuate while higher values reflect more energy.

Conclusion

Signal reflections that can arise whenever impedance changes along a PCB trace are a primary concern in high speed digital design. Using controlled geometries, matched layer stacks, symmetric layout, routed line terminations, and simulation minimizes discontinuities that lead to problematic ringing and noise. With care taken to design, analyze, and validate the transmission environment, signal reflections can be effectively avoided ensuring reliable circuit performance.

Printed Circuit Boards (PCBs) have been the focus of scientist and engineers to bring novel ideas on how to improve the quality of end electronic product. As PCBs play the key role in functionality and performance of any electronic product or device so the perfectly designed PCB layout is highly important. There are many factors that a design engineer must consider while designing a PCB layout and these factors are driven by the requirements of end product.

Like number of layers PCB, size and dimensions of PCB, number of electronic components to be soldered upon PCB, types of components, routing techniques and many other PCB design factors. Among them one of the most important aspect is the “Impedance Matching”. The PCB that is dedicated for the electronic product that is to be used for High frequency application like RF or microwave electronics, then the most critical part of the PCB layout design is to control the impedance of the circuit.

What is Signal Reflection.?

As we are familiar with the phenomena of reflection that when a light ray is incident on the mirror then the light is reflected from mirror’s surface. Another example is water, when light enters the water some of the light is refracted while some is reflected. The same phenomena is with electrical signal. The signal reflection is the phenomena where the source transmits the electrical signal in the signal trace to the receiver/sink and some part of the signal is reflected back from receiver/sink back to the source. This reflected signal can cause signal distortion and oscillation in the circuit.

Why the Signal is reflected..?

The reason for the signal reflection from receiver to the transmitter is the transient impedance caused by the discontinuity in characteristic impedance of signal trace. If the characteristic impedance is uniform through starting from source or transmitter to sink or receiver then there will be no signal reflection. The discontinuity in characteristic impedance of signal trace can be caused by variation in signal trace width, thickness, distance between the trace and the corresponding reference plane and dielectric constant of the substrate material of PCB.

Effects of Signal Reflection:  

Oscillation:

Fortunately, the signal reflected from receiver is always less in strength then the main signal, hence the reflected signal is again transmitted and then again reflected with lesser strength, and hence in this way the signal is diminished slowly but will cause a temporary oscillation.

Overshooting and Undershooting:

If the delay time between the signal transmission and reception is short and the signal transmission is faster and if the previous reflected signal was not given time/delay to diminish and next signal is transmitted then this will cause the signal “peaks”  to accumulate and will cause reflected signal overshooting thus complete failure of the circuit will happen. Similarly if the signal “valley” are accumulated this will cause reflected signal undershooting thus weakening the main signal to cause false clocking or misinterpretation of digital data lines like SDI, SDO, SCLK etc. This overshooting or undershooting can completely destroy the protective diodes at the signal ends.

Signal Distortion:

The reflected signals from receiver end if are strong enough then they can possibly change the logic state of digital circuitry hence the circuit will behave in unanticipated manner. Distorted signal are sensitive towards noise.

How is Signal Reflection Calculated.?

As an example scenario refer to the diagrammatic representation of the signal trace between two points A and B on the PCB.

In the above diagram signal (Vi Voltage and Current Ii) Vi incident from source A to sink B. The characteristic impedance from A to B was continuous but from point B the impedance of signal trace changed hence changing the voltage Vo and current Io transmitted onwards. The characteristic impedance from A to B is Zi while from point B it is Zo. Keeping the picture in view above, for point B looking from left, we can write using ohm’s law as

(1)

Now looking at point B from right, line impedance is now Zo then we can write for Vo as

(2)

Now there are two cases

Case-1: The Impedance is not discontinuous and Zi = Zo

In this case if Zi = Zo then we simply get Vo = Vi means the transmitted voltage is same as incident voltage Vi and no signal is reflected.

Case-2: Discontinuous Impedance Zi ≠ Zo

Now here the incident signal is not completely transmitted onwards because of discontinuous non-uniform impedance of signal trace. Hence some part of the incident signal is reflected back as “Vr”.

Hence we can write

(3)

Now since the reflected current flows in opposite direction so it will be minus from the incident current hence

(4)

The reflected signal is travelling along the signal trace part with impedance Zi therefore we can use ohm’s law

(5)

Put equations 1, 2 and 5 in 3 we get

(6)

But

(7)

Therefore

(8)

Or

(9)

This term with the impedance is called the reflection coefficient “Rc”.

The value of Rc can be from -1 to 1. But ideally Rc should be zero

Methods to Reduce Signal Reflection:

• The transmission rate or speed of the signal can be decreased so that the oscillation of reflected signal can be minimized and stabilize the circuit’s signal trace
• The PCB thickness is relatively kept low so as to reduce parasitic capacitances
• Shorten the signal transmission trace length by carefully arranging number of layers in multilayer HDI PCBs. This can effectively decrease the parasitic inductance to reduce cross talk between signals
• The number of turns or bends in the signal trace should be kept as low as possible. The signal trace should be in straight line but if the bend is necessary then the bend arc should be at 45^O. This helps to reduce EMI radiation
• Route all important signal lines on same plane to minimize unwanted through holes.
• The separate ground and power planes should be used for separate regulated power supply for noise reduction in multiple power supply circuit system. This will enhance signal integrity.
• Apply correct routing topology

Routing Topologies:

The Parallel Topology:

In this structure arrangement, the source is simultaneously feeding the signal to more than one sinks or receivers. All the nodes/receivers connected in parallel or star fashion are synchronized with source. However the separate termination resistance is required for each node/branch and must be compatible with characteristic impedance.

The Series Topology:

Here the one transmitter or source is connected in daisy chain or series fashion the output of one is connected to input of other. A simple series resistor can be placed close to the driving/transmitting/source end to make the impedance at the receiver side compatible with characteristic impedance. The daisy chain branch length should be kept as short as possible. However the signals received at different receiving ends are not synchronized with main transmitter.

Signal Trace Termination:

There are two ways to terminate the signal trace. Either from the source end or from the sink end.

A simple series resistor placed between source and load and close to the source will do the job.

There are 4 ways to make signal termination at load / sink end.

Single resistor parallel termination:

RC Termination:

Thevenin Termination:

Diode Termination:

Differential Pair Termination:

Introduction

The Internet of Things (IoT) relies heavily on wireless communication technologies to interconnect smart devices and objects. Wireless provides the flexible, low-cost connectivity fabric that enables the wide range of IoT applications transforming homes, cities, industries, transportation and more. This article explores how various wireless technologies are utilized in IoT systems and the considerations around selecting the best approach.

IoT Wireless Communication Requirements

IoT solutions have diverse connectivity requirements that span long range, high bandwidth, mesh networking, low power, and mobility:

• Range – Connectivity of sensors across a home, factory floor, city grid, agricultural field, etc.
• Bandwidth – Video security cameras require high throughput wireless links.
• Mesh Networking – Extending reach by device-to-device multi-hop routing.
• Low Power – Enabling battery-powered operation for years before maintenance.
• Mobility – Tracking goods in transit or medical assets in a hospital.
• Scale – Potentially thousands of nodes even in a local IoT network.
• Cost – Inexpensive wireless hardware to enable mass deployments.
• Standards – Interoperability across devices from many vendors.

No single wireless technology optimally meets all of these needs. IoT systems utilize multiple wireless protocols combined in a complementary way.

Wireless Communication Protocols for IoT

Several wireless technologies are commonly used for IoT connectivity:

Cellular

• 2G/3G/4G/5G – Provides wide area connectivity using existing cellular infrastructure. IoT-optimized LTE variants called LTE-M and NB-IoT exist.
• Benefits – Ubiquitous coverage, mobility, security, bandwidth
• Limitations – Cost, power consumption

WiFi

• 802.11 – Ubiquitous wireless local area networking technology. IoT uses low power WiFi variants like 802.11ah.
• Benefits – Commonly available, supports IP networking, high bandwidth
• Limitations – Power hungry, limited range

Bluetooth

• Bluetooth LE – Low energy version of Bluetooth ideal for periodic IoT sensor data.
• Benefits – Ubiquitous, very low power, low cost, standards-based
• Limitations – Short range under 100m. Low bandwidth.

LoRaWAN

• LoRaWAN – Long range, low power wireless protocol using LoRa modulation on sub-GHz bands.
• Benefits – Long range (kms), low power, secure, operates below 1 GHz
• Limitations – Lower bandwidth, higher module cost

Proprietary RF

• Proprietary – Custom wireless protocols using freely available ISM bands like 900 MHz or 2.4 GHz.
• Benefits – Optimized for specific application needs around range, power, cost.
• Limitations – Vertical integration required. No interoperability.

LPWAN

• Sigfox, Ingenu – Ultra narrowband, long range technologies for basic IoT data.
• Benefits – Long range, low power, low cost connectivity
• Limitations – Very low bandwidth. Limited data.

This variety of wireless options provides flexibility to match the right connectivity to application requirements.

Key Considerations for Wireless IoT

Key factors to evaluate when selecting wireless technologies for an IoT solution include:

Power Consumption

Battery powered devices may need to operate for years before maintenance. Low power wireless like Bluetooth LE, LoRaWAN, and LPWAN reduce power use.

Range Requirements

Sensors spread across large physical spaces require long range wireless connectivity, even km-scale for rural settings. Cellular, LoRaWAN provide this.

Bandwidth Needs

Video security cameras require WiFi or 4G LTE class bandwidth versus simple temp sensors that just need low bandwidth LoRaWAN uplinks.

Cost Sensitivities

Bluetooth LE provides the most cost efficient wireless modules. LPWAN networks have low subscription costs for massive sensor deployments.

Mobility

Tracking assets in motion requires cellular or WiFi. Fixed assets can use LoRaWAN, Bluetooth LE, or other lower power approaches.

Security Concerns

Public networks require proven secure connectivity like LTE/5G. Private networks on proprietary RF or LoRaWAN also enable encryption.

Interoperability Needs

WiFi, Bluetooth LE, and LoRaWAN are standardized for interoperability. Proprietary RF limits to single vendor deployments.

Combining technologies is common to meet varied connectivity needs. For example, sensors could use Bluetooth LE to a gateway, then LoRaWAN backhaul to the cloud.

Wireless Technologies for Common IoT Applications

Different vertical IoT applications impose unique wireless requirements:

Smart Home – Primarily uses WiFi with supplemental Bluetooth LE, ZigBee, or proprietary mesh networks to link low-bandwidth sensors and smart home devices.

Industrial IoT – Requires multi-km range on private networks with combinations of proprietary wireless, LoRaWAN, and cellular for backhaul. Reliability and security are critical.

Smart Cities – Take advantage of existing infrastructure using 4G/5G networks for connectivity of city assets. LoRaWAN also sees adoption in city-scale deployments.

Agriculture IoT – Connectivity of rural agricultural assets is enabled by LoRaWAN, Sigfox, and proprietary wireless which provide range of up to 10 km or beyond.

Connected Vehicles – Leverage 4G LTE, emerging 5G networks, and on-board WiFi hotspots for vehicles. DSRC provides short range vehicle-to-vehicle links. Bluetooth LE connects in-cabin.

Retail and Inventory – Stores use a combination of WiFi, Bluetooth beacons, RFID, and LPWAN to link devices managing inventory, logistics, and merchandise flow.

Healthcare IoT – Hospitals employ WiFi supplemented by proprietary RF for reliable indoor asset tracking of medical equipment, and Zigbee devices for long battery life.

The diversity of vertical applications demonstrates why IoT takes advantage of nearly the full spectrum of wireless technologies today.

Wireless Communication Protocols for IoT – Comparison

Optimizing Wireless Coexistence

With various wireless technologies potentially deployed in proximity, steps must be taken to minimize interference between protocols sharing frequency bands:

• Proper RF site survey and planning of wireless coverage areas
• Frequency channelization optimization and allocation
• Transmit power level adjustments to minimize overlap
• Scheduling of transmission activity windows
• Prioritizing co-located traffic based on quality of service needs
• Adding physical isolation between nearby wireless infrastructure
• Leveraging directional antennas and spatial separation

Testing and adjustments after deployment can optimize coexistence and performance.

The Role of LP-WAN for IoT Wireless Connectivity

LP-WAN (Low Power Wide Area Network) technologies like LoRaWAN and Sigfox provide a uniquely optimized combination of long-range wireless connectivity and low power operation:

• Enable battery lifetimes up to 10 years from a single AA battery
• Provide wireless coverage across entire cities, agricultural areas, and industrial sites
• Operate in license-free sub-1GHz frequency bands
• Leverage a star network topology with distributed gateways
• Offer strong security and interference resistance
• Support millions of end node devices
• Enable low cost connectivity at approximately $5 per node
• Sustain excellent range even in urban areas and indoor locations
• Provide sufficient thoughput for typical IoT sensor data
• Maintain robustness at very low transmit power levels

LP-WAN fills a technology gap between short range protocols like Bluetooth LE and wide area cellular networks. This drives adoption for water metering, asset tracking, agricultural monitoring, and smart city applications.

Future Outlook for Wireless IoT Connectivity

The landscape of wireless technologies for IoT continues to rapidly evolve:

• 5G will provide higher performance cellular connectivity especially benefiting high bandwidth video and mobile IoT uses
• WiFi 6 increases speed, density, and efficiency of wireless local networking for IoT
• Bluetooth 5 improves range, broadcasting, and mesh capabilities of Bluetooth LE
• Thread and Zigbee will gain adoption in smart home and building automation
• NB-IoT and LTE-M extend cellular capabilities for low power wide area IoT
• Carrier aggregation across multiple wireless protocols to enhance reliability and throughput
• Edge computing will distribute intelligence into the IoT network lowering wireless data needs
• New spectrum like CBRS and 6 GHz bands will expand available wireless capacity

Conclusion

IoT is driving adoption of a diverse palette of wireless technologies to serve the connectivity needs of smart objects. Factors around power, range, bandwidth, mobility, scale, and cost dictate the optimal wireless approach for specific applications. Ongoing enhancement of wireless protocols and spectrum availability will support the growth of IoT innovations transforming our infrastructure, industries, homes and cities. Comprising the communication fabric tying everything together will be standards-based, IP-connected wireless networks enabling the promise of the Internet of Things.

IoT Wireless Communication – Frequently Asked Questions

What is the difference between LPWAN and WAN?

LPWAN refers to Low Power Wide Area Network technologies designed specifically for wireless IoT sensors. This includes LoRaWAN and Sigfox. WAN more broadly means any wide area network including cellular networks.

Which wireless technology has the longest range for IoT?

Sigfox and LoRaWAN can provide wireless connectivity exceeding 50km in rural areas. Proprietary sub-GHz networks can also attain multi-km ranges suitable for wide area IoT.

Do IoT devices support WiFi?

Some do – WiFi provides high bandwidth wireless connectivity suitable for IoT video cameras, gateways, and devices requiring faster data rates. Low power WiFi variants help address high power consumption.

What is 5G NR?

5G NR stands for Fifth Generation New Radio. It defines the global standard for upgraded 5G cellular networks with benefits like multi-Gbps speeds, ultra low latency, and improved support for massive IoT device density.

Which wireless protocol offers the lowest power consumption?

Bluetooth LE currently enables the lowest power wireless communication, allowing IoT sensors to run for years on small batteries. However, new LPWAN technologies like NB-IoT are competitive on power usage.

Introduction

Pulsonix is a printed circuit board (PCB) design software tool from WestDev. It provides an integrated, configurable environment for schematic capture, PCB layout, and manufacturing. Pulsonix is considered an affordable and easy to use option for electronics design teams. This article will provide an overview of Pulsonix and its key capabilities.

Pulsonix Background

Pulsonix was first released in 1991 by a UK-based team that had previously worked on the PADS PCB toolset. It was designed from the ground up to be an integrated, scalable PCB design system that was both powerful and inexpensive compared to competitive tools.

Now on its 11th major version, Pulsonix has grown from its roots to be a full-featured PCB design platform serving over 9000 users worldwide. It combines ease of use with modern features expected in current EDA tools.

Some of the major benefits Pulsonix aims to provide are:

• Low cost of ownership compared to other commercial PCB design tools
• Short learning curve for new users to become productive quickly
• Environment customizable for specific design needs and workflows
• Scalable to handle designs from simple to extremely complex
• Constant enhancement with new features and updates

Pulsonix continues to meet the PCB design needs of small workgroups, startups, makers, and large enterprises alike.

Schematic Capture Overview

Pulsonix provides robust schematic editing capabilities for defining circuit connectivity. Features include:

• Real-time electrical rules checking (ERC)
• Component library with 50,000+ industry standard parts
• Drag-and-drop part placement from library browser
• Spreadsheet-style editing of component properties
• Virtual pin swapping for easy part variants
• Automatic wire routing and cleanup
• Busses for conveying groups of signals
• Hierarchical and multi-channel design re-use
• Multi-level flat or hierarchical netlisting
• Complex equation parsing for parameters
• Import/export of netlists from other EDA tools

These features allow electrical engineers to quickly draft schematics following best practice design rules. Integration with the layout environment enables smooth transfer of the schematic into PCB realization.

PCB Layout Overview

The Pulsonix PCB layout editor contains advanced tools for board design:

• Direct import of netlists from Pulsonix schematic or external tools
• Intelligent component placement with real-time DRC
• High-speed multi-threaded autorouter
• Sketch routing with timing-driven length tuning
• Curved traces and servo traces for control over routing paths
• Dynamic copper fill connected to nets
• Design-for-manufacturing checking integrated into layout
• Automatic backdrilling and via stub management
• Alternating pair routing for differential signals
• Length matching, phase tuning, and delay management
• Real-time 3D clearance checking
• STEP import/export for mechanical integration
• Revision control and design variant management
• Native support for rigid-flex boards
• Full design rules and constraint management

This extensive toolset allows PCB designers to turn schematics into routable board layouts with verification at each step. Integration of schematic and layout in one tool avoids data translation errors.

Library and Supply Chain Features

Pulsonix includes extensive capabilities to leverage component libraries and connect with the manufacturing supply chain:

• Unified library format for symbols, footprints, 3D models
• Drag-and-drop parts from supplier component catalogs
• Library lifecycle workflows with revision history
• Automated BOM generation from layout
• One-click design submission from Pulsonix to PCB fabs
• Model download from Ultra Librarian store of over 500M parts
• Direct library partnership with distributors like DigiKey
• Library 생성/editing tools for custom footprints
• Import libraries from existing CAD systems
• Interfaces with MRP/ERP systems for BOM integration

Using Pulsonix, designers can easily access supplier component data to accelerate design-through-manufacturing handoff.

Design Flow and Environment

Pulsonix provides a streamlined, configurable environment for PCB design:

• Unified single-executable design framework
• Customizable ribbon interface for tool access
• Docking windows and panels for contextual information
• Report generation for BOM, netlist, etc.
• Batch output of manufacturing and documentation files
• Multi-level undo and redo for change history
• 64-bit multi-threaded operation
• Distributed processing across multiple servers
• Scripting and automation using API or Tcl/TK
• Revision control integration with SVN or Git
• Project templating for re-use and standardization
• Drop-in integration with CAM software

The flexible architecture allows large engineering teams to tailor Pulsonix to their specific organizational needs and tool flows.

Add-on Modules and Options

Optional add-ons enhance Pulsonix with specialized functionality:

Analysis Tools – Hyperlynx SI/PI for signal/power integrity analysis and DFM Pro for manufacturability checks

3D PCB Visualization – Micro Magic 3D modeling and visualization

DFM Checks – Automated Test for fabrication shop testing and view simulation

CAM Tool Output – Optimized data handoff to various CAM software

Reverse Engineering – Imports from Gerber and ODB++ data to recover/update existing boards

Motion Control – Advanced interconnect design for electronics in motion systems

FPGA Integration – Native bidirectional interface with FPGA tools like Altera Quartus

These advanced modules customize Pulsonix capabilities for specialized applications beyond standard PCB layout requirements.

Pulsonix PCB Design Features

To understand Pulsonix capabilities in more detail, here are some key features supported in the core platform and add-ons:

Physical PCB Design

• Any layer count and stackup
• Split power planes
• Rigid-flex boards
• Curved and spiral traces
• Blind/buried vias
• Via fencing
• Length tuning
• Automatic backdrilling
• Dynamic copper fill
• Assembly variants

Electronics Data Management

• Unified database repositories
• Lifecycle workflows
• Revision control
• Design reuse
• Batch processing
• Reporting and analysis

Manufacturing Integration

• Bidirectional library linking
• Built-in DFM analysis
• Fabrication documentation
• Tooling generation
• Data export to CAM systems
• Panelization and breakout

High Speed Design

• Differential pairs routing
• Constraint management
• Phase tuning
• Length matching
• IBIS modeling
• SI/PI analysis
• DDRx memory routing

Advanced Technologies

• HDI microvias
• Embedded components
• Flex/rigid-flex
• Chip packaging
• PCB RF designs

This range of advanced to specialized capabilities makes Pulsonix well suited for usage across various industry verticals including telecom, military, industrial, and consumer electronics.

Pulsonix PCB Design Flow

A typical design flow using Pulsonix would involve:

1. Schematic Capture – Draft schematics with electrical connectivity. Run ERC checks.
2. Netlisting – Generate netlist or import netlist from external tools.
3. Library Creation – Build symbol and footprint libraries for components used.
4. Board Layout – Import netlist and place components. Route board.
5. Verification – Run design rule, signal integrity, thermal checks.
6. Documentation – Generate manufacturing and assembly outputs.
7. Fabrication – Submit Gerber, NC drill, and test files to board fabrication.
8. Assembly – Send pick-and-place and test/inspection files to contract assembler.
9. Manufacturing Data Management – Share build data across supply chain.
10. Revision Control – Track layout changes and release new versions.

This process is streamlined in Pulsonix through integration between schematics and PCB layout in one tool. Data can also be imported/exported at various stages to interface with external electronics workflows.

Pulsonix PCB Design – Frequently Asked Questions

Here are some common questions regarding using Pulsonix for PCB design:

How good is the autorouter in Pulsonix?

The multi-threaded autorouter in Pulsonix is quite advanced. It can route even complex designs quickly with tuning of strategy parameters. Manual clean-up is still required but minimized.

What DFM checks are included in Pulsonix?

Pulsonix has real-time DRC during placement and routing along with extensive pre-processing design-for-manufacturing checks through add-on DFM Pro module.

Does Pulsonix include version control?

Yes, native integration with Subversion and Git repositories is provided to enable managed revisions and collaboration across designers.

What manufacturing outputs are generated?

Pulsonix supports generation of all needed fabrication and assembly outputs including Gerbers, NC drill files, IPC-2581, assembly drawings, pick-and-place, and more.

Can Pulsonix import/export data with other EDA tools?

Standard formats like ODB++, IPC-2581, STEP, and IDF can be imported/exported. Native two-way interface with some tools like Mentor Xpedition is also available.

Conclusion

Pulsonix provides a scalable, configurable PCB design solution with capabilities spanning schematic capture, layout, library management, and manufacturing.Integration throughout the tool ensures efficient schematic-to-layout handoff. Ongoing enhancement along with accessible licensing makes Pulsonix an appealing option for organizations with advanced PCB design needs.

The Pulsonix is the classic software available online with free trial version 10.5. This include schematic capture, spice simulator, PCB layout, auto router, chip packaging toolkit, library integration toolkit, embedded components, Micro-Vias, Interactive high speed, Spirals and Database Connection (PDC) Trial. Please visit pulsonix.com to download your own copy.

Software Interface:

As we open the software, it shows the window with Design, Technologies + Profile and Wizard options. Choose File >> New >> Design >> Schematic Diagram Design

You can open the example schematic from

File >> Open >> User >> Documents >> Example.sch

I opened the notch filter schematic and it look like this

Here we can see many tool available.

On the left hand side, there is a vertical tool bar.

This symbol  is the electronic component library placement. Left click on this and library window will appear.

The “Filter” option with asterisk mark gives you flexibility to enter the keyword for the component you are looking for. Click “Apply” to activate the filter. In the “look in”, a drop down menu will show the list of all manufacturers available with their libraries. The manufactures are listed A to Z and in “Generic” you will find generic capacitor, resistors, diodes, transformer, fuse, crystal and zener diodes. The special thing is that the component footprint is also mentioned in the box and component designator and component symbol is also shown.

You can click on the “Preview” check mark to show or hide the component symbol and you can also check mark the Schematic & PCB to hide or show the component footprint. This is very useful to see what footprint will be used in PCB layout design。

Panning / Zooming:

Left click and depressed and move your computer mouse to “Pan”. Scroll Up to zoom in and scroll down to zoom out

Inserting Connector Pin

You can insert the connector pin same as the component. Part number, description, total number of pins, family, footprint, symbol and name are shown in the window. You can use filter to select the connector pin of your choice. You have to click “Add” to place the pin on the schematic sheet.

You can change the pin number from here. The pin placed on the schematic is pin number 5 of the connector part number shown in below diagram. The connector however is 24 pin total.

Insert Document Symbol:

You can insert the page border and symbol with description with various sizes like A, A1, A2, A3 and A4 and B, C and D landscape borders.

Click Add to place the symbol.

Inserting the Signal Reference:

The signal references like +5V, 12V, 15V, Ground, common, earth, box, input, output, pointer, terminal, VCC, VDD and VSS.

These signal reference are very important in any circuit design hence can be placed by clicking here  on left menu.

The symbol in previous section can be placed by clicking here  on left menu

The connector pin can be placed by clicking here  on left menu.

The bus bar can be placed by clicking here  on the left menu

The bus bar is used commonly in microprocessor or memory circuits where I/O s are too many.

Connecting the Components Together:

You can connect your components by clicking here  on the left menu. This is the wiring connection. When you connect the nodes together or connect nets then a confirmation prompt will occur. Click OK to continue.

Place Text:

You can also place text on current sheet by clicking here

Electrical Rule Check: (ERC)

You can run the electrical rule check on the schematic you design and check the following parameters. Pin type rules, busses, hierarchy, unfinished nets and unfinished connections. There are other checks that you can mark according to your requirements

Click on Check to run the ERC. A report file in text document will be generated showing errors and warnings if any.

Test Point:

You can insert the test points Insert >> Test Point

Click on any point/wire/junction in the circuit and a green color line will appear then click anywhere on the schematic to drop the test point.

Page Link:

If your schematics is on more than 1 page, then you can insert page link by Insert >> Page Link

Changing Units:

Setup >> Units >> Imperial or Metric

Grids:

Setup >> Grids >> Basic Step, Multiplier, Divisor, Step and display

Top Menu:

This menus has the new, open, save, print, setup folder, library, technology, colors and options in the sequence from left to right as shown.

Simulation:

As we know that Pulsonix offers schematic capture, simulation and PCB layout. So here we discuss simulation aspect.

Simulation >> Set Netlist Spice Type

Here you can set the netlist spice type form different options Basic Spice, LTSpice, PSpice, Pulsonix Spice and SIMetrix. Select the Pulsonix Spice.

Insert Source:

For simulation we know that the circuit needs inputs source. Go to Simulation >> Insert Source, a drop down menu will show many options like power supply, waveform generator, AC voltage source, DC current source, CCCS, CCVS, VCCS and VCVS.

Insert Part Using Model:

There are parts that do not have spice models and many others have. So you can choose only those components definitely having spice models.

Simulation >> Insert Part using Model

This window will open. You can choose the type of component from left panel and select the part number and component symbol is also shown in bottom.

Insert Probe:

You can insert the fixed probe in your schematic to run the transient or AC analysis parameters. Go to Simulation >> Insert Fixed Probe

A drop down menu will open showing the options shown in this figure. There are various types of probes like voltage probe, differential voltage probe, current probe, bus probe, voltage dB and Voltage phase probes etc.

Simulation Parameters:

You can change the simulation parameters from

Simulation >> Simulation Parameters

This has transient, AC, DC, Noise. Transfer Function (TF), Options and Safe Operating Area (SOA)

Like for AC analysis, you can set the start, stop and points per decade for simulation. Method can be decade or linear. Check mark the simulation type on the right side you want to run. Then press F9 to simulate the circuit

As consumer electronics demand increasingly compact, lightweight designs, PCBs must adapt to support high-density interconnects (HDI) and complex layouts. This miniaturization trend drives semiconductor manufacturers to develop finer-pitch packages like QFNs, BGAs, and flip-chip arrays. To maintain routability and signal integrity in these constrained designs, PCB engineers now strategically combine VIPPO (Via-in-Pad Plated Over) technology with traditional approaches – including dog-bone fanouts, microvias, skip vias, and routed solder pads. This hybrid methodology enables robust PCB layouts that meet modern performance requirements while accommodating shrinking form factors

Understanding Via Types: The Foundation of PCB Interconnects

Before we dive into the specifics of Via in Pad technology, it’s essential to understand the various types of vias used in PCB design. Vias are crucial components in multilayer PCBs, providing electrical connections between different layers of the board.

Through-hole Via

The most common and traditional type of via is the through-hole via. These vias extend through all layers of the PCB, connecting components on the top layer to traces on inner layers or the bottom layer. While simple and reliable, through-hole vias consume significant board space and limit the potential for high-density designs.

Blind Via

Blind vias connect the outer layer of a PCB to one or more inner layers but do not extend through the entire board. These vias are visible on one side of the PCB but not the other, hence the term “blind.” Blind vias allow for higher component density and improved signal integrity compared to through-hole vias.

Buried Via

Buried vias are internal connections between inner layers of a multilayer PCB. They are not visible from either the top or bottom of the board. Buried vias offer excellent signal integrity and allow for even higher component density than blind vias, but they increase manufacturing complexity and cost.

Microvia

Microvias are small-diameter vias, typically less than 150 micrometers, used in high-density interconnect (HDI) PCBs. They can be either blind or buried and are essential for ultra-compact electronic devices like smartphones and wearables.

What is a Via in Pad?

Via in Pad (VIP) technology, also known as Via in Pad Plated Over (VIPPO), is an advanced PCB manufacturing technique where vias are placed directly within the surface mount pads of components. This approach differs from traditional designs where vias are typically placed adjacent to the pads.

In VIP designs, the vias are filled with a conductive or non-conductive material and then plated over, creating a flat surface for component placement. This technique allows for direct connections between the component leads and inner PCB layers without requiring additional routing space around the pad.

Benefits of PCB Via in Pad Technology

The adoption of Via in Pad technology offers several significant advantages:

1. Increased Routing Density: By placing vias directly in the pads, designers can dramatically increase the available routing space on the PCB. This is particularly beneficial for complex, high-density designs.
2. Improved Signal Integrity: Shorter trace lengths between components and inner layers reduce signal degradation, leading to better overall performance, especially in high-speed designs.
3. Enhanced Thermal Management: VIP can improve heat dissipation by providing a more direct path for thermal energy to travel from components to inner layers or heat sinks.
4. Reduced PCB Size: The space-saving nature of VIP allows for smaller overall PCB dimensions, crucial for compact electronic devices.
5. Better EMI Performance: Shorter trace lengths and reduced loop areas contribute to improved electromagnetic interference (EMI) performance.
6. Increased Reliability: Properly implemented VIP can enhance the mechanical strength of solder joints, potentially improving the overall reliability of the PCB.

When to Use Via-in-Pad in Design?

While Via in Pad technology offers numerous benefits, it’s not always the best choice for every PCB design. Here are some scenarios where VIP is particularly advantageous:

1. High-Density Designs: For PCBs with a high component density or complex routing requirements, VIP can provide the necessary space savings and routing flexibility.
2. High-Speed Applications: In designs where signal integrity is critical, such as high-frequency circuits or high-speed digital interfaces, VIP can help maintain signal quality.
3. Ball Grid Array (BGA) Components: VIP is especially useful for routing connections from BGA packages, where space under the component is at a premium.
4. Size-Constrained Designs: When miniaturization is a primary goal, such as in wearable devices or compact consumer electronics, VIP can help achieve the desired form factor.
5. Thermal Management Challenges: In designs where heat dissipation is a concern, VIP can provide improved thermal paths for critical components.

Read more about:

•  BGA Via in Pad
• Via filling
• Annular Ring
• Blind vias
• Half Hole PCB

Design Considerations for Via-in-Pad

Implementing Via in Pad technology requires careful consideration of several factors to ensure successful manufacturing and reliable performance.

Size and Spacing

The size of the via and its placement within the pad are critical considerations. Designers must balance the via size with the pad size to ensure sufficient copper remains for soldering. Additionally, the spacing between vias and pad edges must be carefully controlled to prevent solder wicking and ensure reliable connections.

Material Compatibility

The choice of via fill material is crucial in VIP designs. Conductive and non-conductive materials each have their advantages and challenges. Designers must consider factors such as thermal expansion, adhesion to copper, and compatibility with the soldering process when selecting fill materials.

Drilling Precision

VIP requires extremely precise drilling to ensure vias are correctly positioned within pads. High-quality drilling equipment and processes are essential to maintain the necessary accuracy and consistency across the PCB.

Soldering and Plating

The plating process for VIP is more complex than traditional vias. The via must be filled, planarized, and then plated over to create a flat surface for component placement. This process requires careful control to ensure a smooth, void-free surface that’s suitable for reliable soldering.

Cost Considerations

While VIP technology offers significant benefits, it also comes with increased manufacturing costs. The additional processing steps, specialized materials, and tighter tolerances all contribute to higher production expenses. Designers must weigh these costs against the benefits to determine if VIP is the most cost-effective solution for their specific application.

Traditional Vias vs. Via in Pad: A Comparative Analysis

To fully appreciate the advantages and trade-offs of Via in Pad technology, it’s helpful to compare it directly with traditional via techniques.

Non-conductive Epoxy Via Fill

Traditional vias are often left unfilled or filled with a non-conductive epoxy for structural support. This approach is simpler and less expensive than VIP but has several limitations:

• Requires additional space for via placement adjacent to pads
• Can lead to longer trace lengths and potential signal integrity issues
• May result in larger overall PCB dimensions

In contrast, VIP addresses these issues but requires more complex manufacturing processes.

Via-in-Pad Generation

The process of creating VIP differs significantly from traditional via generation:

1. Traditional Vias:
   • Drilled during the initial PCB fabrication process
   • May be plated or unplated
   • Often left unfilled or filled with non-conductive material
2. Via in Pad:
   • Requires precise drilling within component pads
   • Must be filled with conductive or non-conductive material
   • Requires planarization to ensure a flat surface
   • Plated over to create a solderable surface

The VIP process is more complex and time-consuming but results in a more compact and potentially higher-performing PCB.

Guidelines for Via-in-Pad Routing

Routing guidelines for VIP differ from those for traditional vias:

1. Traditional Vias:
   • Typically placed adjacent to pads
   • Require fanout traces to connect to inner layers
   • May use teardrops for improved mechanical strength
2. Via in Pad:
   • Placed directly within component pads
   • Allow for direct connections to inner layers without fanout
   • Require careful consideration of via size and placement within the pad

VIP routing can significantly simplify PCB layout, especially for complex, high-density designs.

Challenges of PCB Via in Pad Technology

While Via in Pad technology offers numerous benefits, it also presents several challenges that designers and manufacturers must address:

1. Manufacturing Complexity: VIP requires more sophisticated manufacturing processes, including precise drilling, via filling, planarization, and plating. This complexity can lead to longer production times and higher costs.
2. Potential for Voids: If not properly filled and plated, VIP can develop voids or air pockets that may compromise reliability. These voids can lead to issues such as solder joint failures or moisture ingress.
3. Thermal Management: While VIP can improve thermal performance in some cases, the filled vias may not conduct heat as effectively as solid copper. Designers must carefully consider thermal requirements when implementing VIP.
4. Rework Challenges: Reworking components on VIP can be more difficult than with traditional designs. The filled and plated vias may complicate component removal and replacement processes.
5. Increased Inspection Requirements: The complex nature of VIP necessitates more rigorous inspection processes to ensure quality and reliability, potentially increasing production time and costs.
6. Material Selection: Choosing the right via fill and plating materials is crucial for VIP success. Incompatible materials can lead to reliability issues or manufacturing defects.
7. Design Tool Limitations: Some PCB design software may not fully support VIP technology, requiring workarounds or manual adjustments in the design process.

Manufacturing Process for Via-In-Pad

The manufacturing process for Via-In-Pad PCBs involves several specialized steps:

1. Drilling: Precision drilling of via holes within component pads.
2. Plating: Initial plating of the via holes to create an electrically conductive surface.
3. Filling: Filling the vias with conductive or non-conductive material, depending on the design requirements.
4. Planarization: Smoothing the filled vias to create a flat surface flush with the pad.
5. Over-plating: Applying an additional layer of copper over the filled and planarized vias.
6. Surface Finishing: Applying the final surface finish (e.g., ENIG, HASL) to prepare the pads for soldering.

Each of these steps requires careful control and specialized equipment to ensure high-quality results. The complexity of this process contributes to the higher cost of VIP PCBs compared to traditional designs.

Applications of PCB Via in Pad

Via in Pad technology finds applications in various industries and product types, particularly where high performance and compact design are critical:

1. Mobile Devices: Smartphones, tablets, and wearables benefit from the space-saving and signal integrity improvements of VIP.
2. Aerospace and Defense: High-reliability electronics for aerospace applications often utilize VIP for its performance and durability benefits.
3. Medical Devices: Compact medical devices, such as hearing aids or implantable devices, can leverage VIP to achieve miniaturization without compromising functionality.
4. High-Performance Computing: Servers and high-end computing systems use VIP to manage high-speed signals and dense component placement.
5. Automotive Electronics: Advanced driver assistance systems (ADAS) and infotainment systems in modern vehicles often incorporate VIP technology.
6. Telecommunications: 5G infrastructure equipment and high-speed networking devices benefit from the signal integrity improvements offered by VIP.
7. Consumer Electronics: High-end audio/video equipment and gaming consoles use VIP to manage complex routing in compact form factors.

Conclusion: The Future of Via in Pad Technology

As electronic devices continue to demand higher performance in smaller form factors, Via in Pad technology is likely to become increasingly prevalent in PCB design and manufacturing. While it presents certain challenges in terms of manufacturing complexity and cost, the benefits of increased routing density, improved signal integrity, and enhanced thermal management make it an attractive option for many applications.

The future of VIP technology will likely see advancements in materials and manufacturing processes to address current limitations. Innovations in via fill materials, plating techniques, and inspection methods will contribute to improved reliability and potentially lower production costs.

For PCB designers and manufacturers, staying abreast of developments in Via in Pad technology and building expertise in its implementation will be crucial for remaining competitive in the rapidly evolving electronics industry. As with any advanced technology, successful adoption of VIP requires a thorough understanding of its benefits, limitations, and best practices to ensure optimal performance and reliability in the final product.

By carefully considering the trade-offs and applying VIP technology where it offers the most significant advantages, designers can create more compact, higher-performing electronic devices that meet the demanding requirements of modern applications.