Surface mount devices (SMD components) are the main electronic function parts that are soldered onto the circuit board using the surface mount technology. They are not that different from the through-hole electronic components so far we are talking about the electrical function.
However, due to the smaller size, the surface mount components offer a much better electrical performance. Note that, not all of the smd components present in the surface mount is for the PCB assembly process of electronics.
This is why the benefits of PCB surface mounting aren’t available. Also, we are limited to the mix and match surface mount type of assemblies. Using the through hole components like pin grid array (PGA) and ball grid array (BGA) for large connectors and high end processors help in keeping the industry in the mixed assembly mode for the future.
What are the Types of SMD Components?
While there are just a few DIP packages, which meet the packaging requirements, the surface mount packages world is widely more complex.
Note that the types of packages, as well as the lead and package configurations are numerous. Furthermore, the requirements of the SMD components and electronic components are much more demanding. The SMCs or SMD components have to withstand the higher temperatures for soldering. Also, selecting, placing, and soldering them have to be done very carefully so as to achieve an acceptable yield in manufacturing.
Also available are scores of different electronic components present for electrical requirements. This causes a major issue or problem, when it comes to component proliferation. Also, some smd components have good standards, whereas others are nonexistent or inadequate.
Though the SMT (surface mount technology) has matured, it evolves constantly coupled with introducing new packages. Every day, the electronics industry keeps making progress in resolving the standardization, technical, and economic problems with the SMD components. The surface mount components and SMD components come in both passive and active electronic components.
What are the Passive SMD Components?
Thick film resistors, tantalum capacitors, monolithic ceramic capacitors form the main group of the passive smd components. Generally, the shapes are cylindrical and rectangular. The mass of the electronic components’ mass is usually 10 times lower when compared than the through hole.
Furthermore, the surface mount capacitors and resistors are in different case sizes. This is to meet the requirements and needs of the different applications used in the electronics industry. Though a trend falls towards the shrinking sizes of the case, there are larger case sizes as well if there are large capacitance requirements. These electronic components and surface mount devices are also available in both tubular and rectangular shapes.
These come in two types, namely thin film and thick film. The thick film type is constructed using a screening resistive film on a high purity flat alumina substrate surface. You can get the resistance value by varying the resistive paste’s composition before the laser trimming after screening and before screening.
Resistor Networks for SMT
The resistor networks of the surface mounts, also known as R-packs, are usually used in replacing discrete resistors. This helps in saving placement time and real estate. The styles currently available are usually based on the well-known Small Outline Integrated Circuits (SOIC). However there may be variations in the dimensions of the body. Generally, they come in about 16 – 20 pins having a power of 0.5 – 2 watts for each package.
SMT Ceramic Capacitors
The surface mount capacitors are great for circuit applications of high-frequency due to the fact that it doesn’t have any leads. Also, you can place it under the package, which is the PCB Assembly’s opposite side. The reel and 8 mm tape is the most used when packaging the ceramic capacitors.
Also, the SMT ceramic capacitors are useful for frequency control and decoupling applications. There have been improvements in the volumetric capacity of the monolithic multilayer ceramic capacitors. This is one of the smd components that are very reliable and are useful in very high volumes in under the hood aerospace applications, military equipment, and automotive applications.
Tantalum Capacitors for SMT (surface mount technology)
This is another of the smd components that provide a very high reliability, capacitance-voltage product for each unit volume. Furthermore, the lead capacitors have leads rather than terminations as well as a beveled top as its polarity indicator.
Also, there are no placement or soldering issues when making use of the plastic molded tantalum capacitors. You will find them in two sizes – the extended and the standard range.
What are Tubular Passive SMD Components?
These cylindrical devices, which are also called MELFs, are useful for resistors, diodes, tantalum and ceramic capacitors, and jumpers. In addition, they have metal and cylindrical end caps that are useful for soldering.
What are the Active SMD Components?
Surface mounting provides more types of passive and active passages compared to the through hole technology. Below are the different categories of the active smd components.
LCCCS – Leadless Ceramic Chip Carriers
From the name, these carriers feature no leads. Rather they feature groove-shaped, gold plated terminations referred to as castellations, which offer signal paths that are shorter, thereby permitting higher frequencies for operation. Also, we can divide these LCCCs in different families. This depends on the package’s pitch. Of all, the most common is the 50 mil family. The other families available include 20, 25, and 40 mil families.
CLCC – Ceramic leaded chip carriers
You can find these in the postleaded and preleaded formats. For the preleaded carriers, they have Kovar or copper alloy leads, which the manufacturer attaches to it. Also, for the postleaded type, the leads are attached by the user to the ceramic leadless chip carriers’ castellation.
Plastic Packages for the Active SMD Components
The ceramic packages are costly and are mainly for the military applications. Also, the plastic packages for the smd components are frequently used for the nonmilitary applications, whereby there is no need for hermeticity. Below are the plastic packages for the active smd components.
Small Outline Transistors
A small outline transistor is widely regarded as one of the important and active devices when dealing with surface mounting. These surface mount devices are both four-lead and three-lead devices. Generally, these packages are useful for transistors and diodes. Also, these packages have now become universal for the surface mounting small transistors.
Small Outline Integrated Circuit
This is basically called a shrink package having leads on centers of 0.050 inch. Also, it is useful in the housing of integrated circuits that are larger than possible in the SOT packages. There are cases whereby they are useful in housing multiple SOTs.
Furthermore, this has leads on both sides which are usually formed outward where it is referred to as the gull wing lead. It is necessary to handle the small outline integrated circuits with care to avoid any lead damage. They come in two body widths, which are 300 mil and 150 mil. Packages that have body width less than 16 leads will have a value of 150 mil. However for cases over 16 leads, then you should use the width of 300 mil.
Plastic Leaded Chip Carriers
The plastic leaded chip carrier is a less expensive option or version of the ceramic chipcarrier. Its leads offer the necessary compliance in taking up the stress of the solder joint as well as preventing cracks coming to the solder joint. They require proper handling.
Small Outline Package
The small outline package features J-bend leads. However they only feature pins on just two of its sides. Furthermore, the thin small outline package is a PLCC and SOIC hybrid. It also combines the space efficiency of the SOIC and PLCC’s handling benefits. The shrink small outline package is usually useful for very high density DRAMSs.
Ball Grid Array SMD Components
Ball grid array is referred to as a type of array package such as the pin grid array, however with the exception of the leads. The BGA package comes in different types, however the major categories are plastic and ceramic BGA.
The ball pitches of the different types are standardized at 1.5, 1.27, and 1.0 mm pitch, which is equal to 60, 50, and 40 mil pitch. Also, the BGAs body sizes usually vary from about 7 – 50 mm, with their pin counts also varying from 16 -2400.
Fine Pitch SMD Packages
These smd components feature fine pitch, as well as higher number of leads. Examples of this pitch package include thin quad flat pack, plastic quad flat pack, and ceramic quad flat pack. The fine pitch package feature thinner leads and they also require a thinner pattern land design.
Identifying the SMD Components
The SMD components, which are also known as surface mount components can be described as electronic components which are mounted on the PCB (printed circuit board) to work and function. Now, we will be talking about ways of identifying the surface mount device components easily and quickly.
Identifying the SMD Resistors
The SMD resistors can be described as the main surface mount components limiting the amount of current that passes through them. The R denotes resistance and the unit of measurement of resistance is called ohm. Here, there are two main methods for indicating the resistance value present on the appearance of the SMD resistors.
In the Arabic numbers
Here, the first two of the Arabic numbers tell us the resistance value’s absolute numbers. Also, the last number indicates a power of 10. Explaining this, it means that 103 is 10000Ω, then 391 indicates 390Ω. While 470 indicates 47000Ω.
Combining R and the Arabic numbers
Arabic numbers standing before the R indicate the value of resistance for the entire part. Also those coming after the R indicate the resistance value’s fractional part. Explaining this, it means that R100 indicates 0.100Ω, while 5R60 indicates 5.60Ω. Also, 30R9 indicates 30.9Ω.
Furthermore, the classification of the SMD resistors according to use differences includes normal resistors, power resistors, precision resistors, high-frequency resistors, high-resistance resistors, high-voltage resistors.
Identifying the SMD Capacitors
The SMD capacitors can be described as parts of the printed circuit board (PCB) made up of two pieces of metal which an insulator separates and majorly used in storing energy. The C denotes capacitance, while the unit of measuring it is in Farad (F).
This F unit is somehow too large or big for the capacitance of SMDs, and we always make use of the smaller unit, which is pF, nF, μF. Note that 1μF is the same as 1000nF, while 1nF is the same as 1000pF.
Two main methods are available for indicating the value of the capacitance on the appearance of the SMD capacitors. The first method is to denote the working voltage and capacitance on the capacitors directly.
The second method is by combining the working voltage and the Arabic numbers. The first two of the Arabic numbers help to indicate the capacitance value’s absolute numbers. Also, the final number indicates a power of 10.
To explain further, 107 indicates 10 x 10^7 pF which equals 100μF. Also, 225 indicates 22 x 10^5 pF which equals 2.2μF. Furthermore, on the SMD capacitors, a letter and a combination of some numbers denote the capacitance. These letters indicate the capacitance tolerance.
Classifying the SMD Capacitors
Ceramic capacitors are composed of ceramic insulators having two terminals that are sprayed using solver and then sintered. On the SMD capacitors, the C.CAP indicates ceramic capacitors.
Aluminum electrolytic capacitors are composed of aluminum cylinders that are filled with a liquid electrolyte (altogether as a negative electrode) as well as an aluminum strip (denoting the positive electrode) which is covered using an oxide film which serves as the insulator and plugged into it.
The Tantalum electrolytic capacitors are composed of niobium or tantalum (serving as the positive electrode, while dilute sulfuric acid serves as the negative electrode. Also, it includes the oxide film, which is covered on niobium or tantalum, which serves as the insulator. TC or TAN.CAP denotes the tantalum capacitors.
Identifying the SMD Inductors
The SMD inductors are one of the major electronic components, which help in the conversion of electrical energy to magnetic energy. It also stores it. Also, inductors are composed of a specific enameled wire that winds around the insulator. The L indicates the inductance, and it is measured in Henry (H).
1H means 1000mH, while 1mH means 1000μH. This is the method useful in indicating the value of inductance on the appearance of the SMD inductors.
The first and initial two numbers in the Arabic numbers, tells us the inductance value’s absolute numbers. While the final or last number indicates the power of 10. This means that 470 indicates 47H, while 101 indicates 100H, and 100 indicates 10H.
Identifying the SMD Triodes and SMD Diodes
The SMD diodes are the conductive and unidirectional electronic components. The Diodes are polar components, and it is impossible to reverse their negative and positive electrodes. Also, when there is a flow of current from its positive electrode, the resistance of the diode becomes extremely small. Also, vice versa, there is an extremely large value for the resistance. D or CR indicates the diodes.
On the SMD diodes, that terminal that is printed with lines can be denoted as the negative side of the electrode. The SMD triodes help in controlling the components, which amplifies the current. The Q stands or denotes the triodes.
Identifying the SMD ICs
The SMD ICs are also called surface-mount integrated circuits. This helps in the integration of components like inductors, capacitors, resistors, and diodes, on a very small semiconductor. After this, it is then packaged. With respect to the differences in packaging, the ICs, integrated circuits include SSOP, CSP, BGA, QFP, PQFP, PPGA, PLCC, etc.
Identifying the SMD Crystal Oscillators
The SMD crystal can be described as the quartz piece having two terminals that are sprayed and polished with the help of a silver film. When you package the IC using a quartz piece in forming an oscillation circuit, then it becomes an SMD oscillator. The Y denotes crystal oscillators.
The SMD crystal oscillators offer the main clock signals that serve the system. Also, on any components, if there’s a number combination and Z or HZ, then it is known as a crystal oscillator. Furthermore, you will be able to see the crystal oscillators from that image below. The DIP crystal oscillators feature two long pins. Also, the rest will be the SMD crystal oscillators. In addition, there are four or tins pins.
Identifying the SMD Connectors
The SMD connectors offer permanent and temporary electrical connections for the circuits. Also, there are normally used in the pairs.
Identifying the Switches of the SMD Button
The switches of the SMD button are the surface mount switches, which make use of a button in separating or connecting the two contacts on realizing the switch of the circuit.
This article has given full details regarding the entire well-known surface mount device – SMD components. We have explained how to identify these electronic components just from their appearance. However, if you have needs or concerns regarding the SMD components or printed circuit board, you can contact RayMing PCB using any of our channels.