What is PADS Layout?

This article is for those new in the design of printed circuit boards that hope to finish a board making use of the PADS layout. Note that this was formerly referred to as the PADS PowerPCB tool.

Anyone who  has already had some experience regarding the use of at least one PCB design tool shouldn’t skip this article, as you may have one or two things to learn here. For those new to the process, you will surely get the best view of the entire design process.

What is PADS Layout?

PADS is known as a package for PCB design. Mentor Graphics was responsible for its development. The PADS Layout appears in three different trim levels. From the highest to the lowest level they are: Professional, Standard Plus, and Standard.

PADS is widely regarded as a commercial-grade high-end software package. Furthermore, it includes some high-end features. These include functions like analysis of signal integrity, advanced auto-router, analysis of thermal design, and support for different functions for project management.

PADS comes in three versions, and all three possess different capabilities and are created for different users.

How to Use the PADS Layout?

Below are simple steps to follow when using the PADS layout. This is as follows:

First, choose the components you’ll be making use of on the board, which includes sockets, capacitors, etc. Immediately this list is ready, get the datasheets and then check the footprints, which include the pads or hole sizes in all those datasheets.

Furthermore, in true practice, the components’ major categories used include:

• Capacitors, Resistors, Ferrite beads, and Inductors
• LEDs, FETS, Transistors, Diodes
• Headers, Connectors
• BGA ICs, ICs
• Others

Importantly, you must be extremely careful when it comes to the connectors, which are seen as the component that is electrically simplest. Furthermore, make sure that the physical part is obtained in hand. This will help in verifying the pin number dimensions and orientations.

Footprint creation

Furthermore, for every component, make sure that a footprint is created. If you don’t know what footprint is, it is the components’ physical view, which includes the presence of holes via your pads or board for components of the surface mount. Also, note that you can reuse footprints in one board more than once (at least a few times).

Practically, you’ll have the majority of your footprints available. To create a brand new design, you may only need to create a few more footprints. Also, you’ll have to be very careful, ensuring that the current footprint present in the design library has a match with the component’s mechanical dimension, in line with the datasheet.

Reference designs are available from different companies such as Texas Instruments. It is possible to get the company’s pads design, then export their footprints, which you can make use of after making no or minimal changes.

Schematic View of the Board

Next, there is a need to create your board’s schematic view. What this means is the addition of different board components and then making use of wires to connect them. The creation of Schematics will be achieved making use of Orcad. However, you may need to take some tutorial on Orcad if you’ve never used this before or you have just little knowledge on it.

As soon as the schematic is ready, then you should create the netlist and then import it into the PADS. With the aid of this tool, you will be able to define ground and power planes, place components, as well as route the physical wires. In the end, the board has to be properly verified for any possible errors.

Immediately the board layout is ready, then some files have to be generated, which we refer to as Gerber or artwork. PCB manufacturers make use of these Gerber files to manufacture or produce the board.

Color Settings for the PADS Layout Design

When making use of PADS layout for your PCB design, you should set different colors for every layer to ensure easy viewing.

In PADS, note that the top (bottom) has its default as blue while for the bottom (bottom), it has a red default. Furthermore, this contrasts the color found in the default of the Altium Designer. Every layer is made up of many traces, devices, copper foil, and more.

Also, note that you can decide to set the colors for all these elements in a separate way. This makes it very easy for you to distinguish.

Setting the Colors

For the layout design, just click “settings, then click “display color”. You can also make use of the shortcut Ctrl Alt C. The window for the color setting will come up.

Check the section “selected colors”, where you can select different colors. However, if you cannot find your desired color, you can select Palette, or customize the color you want in the palette.

After you modify the color making use of the “Color Palette” you can easily restore it back to the initial default color by clicking on “Default color palette”.

Next, click on “Assign All”. This will give different colors automatically to each type or layer. Furthermore, in the center or middle, you will find the section “color allocation matrix.” The rows help in indicating the specific layer, while columns on the other hand, tell the objects that are present in every layer.

If you want to assign some colors, all you need to do is select a specific color in the “selected colors” section. Other options, which are seen in the left corner, is the default black color that forms the background. When you select, the color is default white, while when you highlight, the color becomes default yellow. Also, the frame’s color is default gray, while the flying line’s color is default gray as well.

PADS PCB Design Tutorial

Introduction

Printed circuit board (PCB) design involves converting electrical schematics into physical board layouts that route connections between components. PADS is a popular PCB design tool suite from Mentor Graphics that includes schematic capture, layout, and analysis capabilities.

This PADS tutorial introduces the workflow and key features for creating a simple PCB from schematic entry through board routing. We’ll explore the interface, libraries, part creation, netlist generation, layout tools, and output. Following this guide provides an overview of harnessing PADS to take a design from concept through fabrication-ready output.

Installing and Opening PADS

Various options exist for installing and launching PADS:

Standalone – Install the PADS software suite natively on Windows or Linux workstations. Launch the desired application – schematic, layout, library tools, etc.

Cloud Hosted – Access PADS applications through cloud-based virtual desktops from providers like CADMATIC. No local installation needed.

Evaluation – Free trial versions allow evaluating PADS with full functionality for a limited period.

Once launched, the main areas of the PADS graphical interface include the menu toolbar, design workspace, property panels, message log, and navigation sidebar:

This layout remains consistent across the schematic and PCB editors with context-sensitive tools, settings and shortcuts.

Creating a PADS Schematic

The first step is capturing the electrical relationships between circuit components in a schematic using PADS Logic:

1. Create a blank schematic page. Set size, portrait/landscape orientation.
2. Place parts from the component library onto the sheet – microcontroller, connectors, etc.
3. Draw wires to connect part pins together as needed for circuit operation.
4. Set component properties like reference designators, part codes, values.
5. Add text, annotation and graphical objects to document design intent.
6. Connect schematic pages together into a hierarchy.
7. Run electrical rules check to detect any missing connections.
8. Generate netlist and pin report files defining connectivity.

This schematic provides the source connectivity data to drive PCB layout.

PADS Part Creation

Placing parts on a PADS schematic requires symbol and simulation component models defined in libraries:

Symbols – Graphical schematic symbols depict part pins and functions. Created with PADS Symbol Editor. Standard templates exist.

Simulation Models – Attach SPICE simulation models to symbols. Defines electrical behavior for circuit analysis.

Footprint Assignments – Link symbols to PCB footprints for physical mounting. Defined in PADS Layout.

Generating Symbols

1. Open Symbol Editor and select wizard or blank page.
2. Draw box to dimensions representing part package size.
3. Add pin lines for each terminal. Set pin names and numbers.
4. Add other required gates, graphic pins, polygons to illustrate function.
5. Assign simulation model and PCB footprint.
6. Save completed component to library.

This process creates schematic symbols associated with packages for PCB implementation.

Generating PADS Netlists

With the schematic complete, connectivity information is extracted into the PCB netlist:

Netlist Extraction

1. Open schematic in Logic and select Netlist > Extract Netlist
2. Specify filename and output directory to save
3. Choose report options like pin report, connection cross reference
4. Select pages to include, output format (ASCII/binary), and run

Importing the Netlist into Layout

1. Open the target PCB file in Layout
2. Select Netlist > Import
3. Choose previously extracted netlist
4. Map pads to footprint packages
5. Select pages to import
6. Review unmapped parts list and resolve issues
7. Finalize import

This transfers connectivity established in schematic into the PCB layout tool for board routing.

Routing a PADS PCB

With netlist imported, we can route component connections in the PADS PCB editor:

1. Place footprints onto the blank PCB canvas for each part in schematic. Arrange components for ease of routing.
2. Route traces point-to-point between pads to connect the nets. Assign trace widths based on current.
3. Add line, arc, curve segments. Use grid snap for alignment. Tuned routing settings speed work.
4. Assign net names to traces as they are routed using the Net Tuner panel.
5. Add vias to transit between layers. Connect signal vias by name.
6. Fanout controlling traces to destination pads. Minimize crossings.
7. Run design rule check and Net Tuner analysis to detect spacing violations or unrouted nets.
8. Iterate on layout as needed until design rules pass and all required connections are made.

The resulting routed board maps out circuit implementation from concept schematic through physical PCB layout.

Additional PADS Features

Beyond basic schematic and layout, the PADS toolset delivers advanced productivity features:

Rules Driven Environment – Constraint rules govern placement, routing, manufacture. Speeds layout by preventing improper conditions.

True 3D Visualization – Real-time 3D rendering of board with components. Detect collisions and fit.

Signal Integrity – Simulate impedance, crosstalk, timing to ensure signal quality before manufacturing.

DFM Analysis – Identify issues like insufficient thermal relief, chamfering, etc. early.

Library Management – Organization tools for parts, footprints, symbols, and models.

Team Collaboration – Multi-user access with revision control. Release managed workflows.

Manufacturing Outputs – Generate drill, Gerber, and other standard fabrication files.

PADS provides a feature-rich environment encompassing the entire PCB development cycle.

Conclusion

This tutorial introduced key steps in harnessing the PADS software suite for schematic capture, PCB layout, and analysis along with component library generation. PADS enables professional grade printed circuit board implementation following structured design flows.

By leveraging the unified schematic-PCB environment, productivity speedups, rule checks, and analysis utilities in PADS, engineers can transform concepts into manufacturing-ready board designs smoothly. The array of features makes PADS a scalable solution as design complexity increases across single layered circuits to intricate multi-board systems.

Frequently Asked Questions

What are the main differences between PADS and Altium?

PADS uses an integrated schematic/PCB toolset and rules-driven methodology while Altium has separate schematic and PCB editors with more flexibility. Both support advanced capabilities like DFM analysis, version control, and scripting.

Does PADS include auto-routing features?

Yes, the PADS Router provides both interactive and batch automated routing with customizable algorithms, strategies, and completion criteria to augment manual routing.

Can PADS import designs from other EDA tools?

PADS has import utilities to bring in netlists, layouts, and libraries from various third party tools. This helps with conversion and collaboration across mixed EDA environments.

What manufacturing outputs does PADS support?

PADS can generate comprehensive fabrication and assembly files including Gerbers, NC drill, pick and place, assembly drawings, BOMs, and more.

Does PADS integrate with MCAD and simulation tools?

Yes, PADS links with MCAD tools like Solidworks for enclosure design integration and co-simulation. PADS models also transfer to external analysis tools like Ansys SIwave for signal integrity verification.