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PCB SMD Components: Types and How to Identify Them

Posted:03:22 PM December 02, 2022 writer: NextPCB

SMD components are the most widely used for PCB manufacturing. SMD components are small and compact devices that are used in electronic devices, boards, and products. They can be found in computers, phones, TVs, cars, and other products.

These components are often used to create printed circuit boards (PCBs) or integrated circuits (ICs). The following blog post will teach you about different types of SMD Components and how to recognize them:

Types of SMD Components

There are three types of SMD components, and each has its own purpose. 

Passive SMD Components

Passive SMD components are passive devices that require no external power supply or signal to operate. They can be used in many different applications, including wireless communications, automotive electronics, and other applications where reliability is critical. Below are the types of passive SMD Components. 

1. Surface Mount Discrete Resistors

These are small, flat-shaped components that can be mounted directly on circuit boards. They are often used to provide resistance values from 0Ω to 5Ω in series with other components or circuits. There are two types. 

  • Thin film surface mount resistors
  • Thick film surface mount resistors

2. Surface Mount Resistor Networks 

These have a chip that has multiple resistors connected together in series with each other, and they are usually used to give greater resistance values than single-resistor networks would provide due to having more than one component per unit area of the surface on your PCB. 

3. Surface Mount Capacitors

These use ceramic capacitors, and electrolytic capacitors as their dielectric materials instead of glass or plastic packaging like you see with traditional leaded electrolytic capacitor construction methods; this makes them easier to install since they don't require any special tooling or adhesives for assembly purposes!

  • Ceramic
  • Tantalum

4. SMT Tubular Passive Components 

Metal Electrode Leadless Faces, or MELFs, are passive SMD devices used for capacitors, diodes, jumpers, tantalum, and resistors. As the name explains, they are cylindrical shapes with metal caps for soldering.

Because of their cylindrical shape, it's not necessary to place resistors near the board surface. Additionally, MELFs are inexpensive and color-coded for values. MLL 34 & MLL 41 identify MELF diodes, while 0805, 1206,1406, and 2309 identify MELF resistors.

Active SMD Components

Active SMD components act as a switch when they receive a specific input signal from their host system; they respond by switching off or on (depending on whether it's an ON/OFF signal). 

When turned off, the active device draws very little current from its circuit; however, when turned on, it draws more current than normal due to its increased operating voltage. This is why you have seen these devices referred to as “switches” – not because they control anything but rather because they're designed to switch between two states depending upon what kind of input voltage you give them! 

Ceramic Leaded Chip Carriers

Ceramic Leaded Chip Carriers are used for high-frequency applications. The dielectric material is ceramic, and the leads are made of gold-plated copper. Plus Leadless packages are available in two types: plastic and ceramic (plastic variants use a plastic substrate).

Leadless Ceramic Chip Carriers 

Leadless ceramic chip carriers are a type of SMD component, which means they can be mounted to a printed circuit board (PCB) using solder paste.

Leadless ceramic chip carriers are often used in high-speed ICs and other electronics that require small size and high reliability. They have no leads or pins that connect directly to the board; instead, they have integral metal pads on their surface that serve as contact points for electrical connections between components. These pads are made up of a mixture of oxide and titanium nitride films. 

Plastic Packages for the Active SMD Components

The ceramic packages are primarily meant for military use. But plastic packages for the SMD components are also used in nonmilitary applications, where a hermetic seal is not needed. Below are some examples of plastic packages for active SMD components.

Small Outline Transistors

There are four-lead and three-lead surface mount devices. Devices of this sort are useful for both transistors and diodes. And these packages have become universal for smaller surface-mount devices.

Plastic Leaded Chip Carriers 

The plastic leaded chip carrier is a cheaper option or alternative to the ceramic chip carrier. Its leads take the stress off the solder joint and prevent cracks from forming in it. However, they require careful handling.

Small Outline Package

The small outline package is probably your best option if you're looking for J-bend leads. It includes pins on only two sides, and it's thin and space-efficient. In addition, the small outline package is a PLCC and SOIC hybrid. It also combines the handling benefits of the PLCC or SOIC with the high density of DRAMSs.

Small Outline Integrated

This is a shrink package, which means leads are 0.050 inches apart. It's also helpful in housing larger integrated circuits than can be housed with SOT packages. Sometimes they're used to hold multiple SOTs as well.

Furthermore, these are referred to as gull-wing leads owing to their two sides, and it is necessary to handle them carefully in order to avoid leads being damaged. They appear in two different body widths, which include 150 mil & 300 mil packages that have a body width of fewer than 16 leads that will use the smaller size of 150 mil. However, for packages with more than 16 leads, then you should use the size of 300 mils.

Circuit Ball Grid Array 

When people typically talk about BGA, they are referring to a type of packaging known as a pin grid array. This is different because the leads are not on pins. The package comes in different types, but the major categories are plastic and ceramic BGA.

There are three different sizes of BGAs, which differ in pin count. The standard size is 7-50 mm, with a 16-2400 pin count. The ball pitches are all 1.5, 1.27, or 1.0 mm pitch, which corresponds to 60 mils, 50 mils, or 40 mils pitch respectively.

Pitch SMD Packages

SMDs are made of a plastic-like material but with finer leads. Examples of this type of SMD include thin quad flat pack, plastic quad flat pack, and ceramic quad flat pack. The fine pitch package features thinner leads and requires a thinner pattern land design.

How to Identify SMD Components 

There are several ways to identify an SMD component. The first step is to look at the shape of your component and its size, which will help you determine if it's an IC or another type of component. If you're still unsure about what type of component you have, try looking at one side only or even just one pin on your board (if applicable).

If all else fails, turn over your PCB and check for markings on its bottom surface; these markings may indicate where wires connect with different parts of whatever circuit board is underneath! 

Identifying the SMD Resistors

Surface mount components designated with a letter R often denote resistance and the measurement is called ohms. For example, one SMD resistor can be at 0.1 or 1 ohm. A number before the R, such as 10R, means that it has to be higher than 1 ohm. In this text snippet, two main methods of measuring an SMD resistor's resistance are described in detail. 

Identifying the SMD Capacitors

SMD capacitors are considered parts of the printed circuit board made up of two metal pieces with insulation that keeps them separate. They are used in storing electricity (which is measured in Farads). The letters C denotes Capacitance, and the unit used to measure it is "Farad."

This F unit is too large for small capacitors with SMDs. We typically always use smaller units, like pF, nF, or μF. For instance, 1μF = 1000nF and 1nF = 1000pF.

Identifying the SMD Inductors

SMD inductors are one of the major electronic components that help convert electrical energy to magnetism. It also stores it. In addition, an inductor is made up of a specific enameled wire that winds around the insulator. The L indicates how much inductance there is, which is measured in Henry's (H).

1H means 1000mH, or 1,000, micrometers of inductance. On the other hand, 1mH refers to 1,000μH or one millimeter of inductance. This is a method that can be used to indicate the value of an SMD inductor on the PCB board.

SMD Triodes and SMD Diodes

A diode is a type of electronic component that allows you to control the direction of the current. A diode is polar, meaning that it can only control current in one direction: from the positive electrode to its negative electrode. Also, when there's current flowing from the positive side of the diode, the resistance becomes very small. Vice versa, when there's no current flowing from the negative side of the diode, there is a very large resistance. Diodes are most commonly marked with either D or CR.

When metal SMD diodes, the terminal with lines on it and metal backing can be denoted as the negative side of the electrode, the metal SMD triodes help in controlling the components, which amplify current. The designation for metal SMD resistors is a capital Q.

Identifying the SMD ICs

ICs, or integrated circuits, are devices that make electronics work better by integrating components like resistors, capacitors, and inductors onto a semiconductor. ICs are then packaged. There are many different types of IC packaging, such as SSOP, CSP, BGA, QFP, PQFP, PPGA, and PLCC.

Identifying the SMD Crystal Oscillators

The SMD crystal can be recognized as a quartz piece that has two sprayed and polished terminals. When you package an IC with this quartz piece and form an oscillation circuit, it becomes an SMD oscillator. The Y denotes crystal oscillators.

SMD crystal oscillators allow the system to have the main clock signal. There are also some devices with numbers combined with Z/HZ, which means it's also a crystal oscillator. Additionally, there are 4 or 5 pins on the device.

Identifying the SMD Connectors

SMD connectors are known for their provision of temporary and permanent connections in the circuit. And more importantly, SMD Connectors are utilized in pairs. 

Switches of the SMD Button

Switches of the SMD Button are used to reconnect or separate the two connections to highlight the switches of the board as they are surface mount switches. 

Why Choose NextPCB

PCB industry demands high accuracy, quality, and durability, and NEXTPCB  manufacturer of PCB and PCB assembly products having more than 15 years experience in this field. Our clients' success determines our success and you can check our clients reviews as we have designed not only for small businesses but also for large businesses throughout the world. Approach us and receive the best quotes! Also, our online free DFM PCB Gerber viewer can help you review your PCB design hence avoid resulting in costly errors.

Bottom Line 

In this blog post, we have learned about the types of SMD components. We also discussed how to identify them based on their shapes and sizes. Thank you for reading! If you have any questions regarding the topic, let us know, and our team will approach you as soon as they find it. 

Tag: SMD Components
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