What are SMD Components? SMD PCB Assembly Service

Electronic devices with components attached to or mounted directly on the surface of the printed circuit board (PCB) are known as surface-mount devices or SMDs. The assembly factory solders SMD components to the surface of the PCB bare board through SMT assembly. SMT has largely replaced through-hole technology in the electronics industry, which included inserting components using wire leads into holes in the circuit board.

A variety of SMD patch components
Table of Contents

Advantages of SMD PCBA components

Because SMD components can have smaller leads or no leads, they are often smaller than their DIP counterparts. Also, compared to the THT, SMT assembly technology allows both sides of a PCB to be used when required. The following are the advantages of using SMD components in circuit boards

An Efficient Assembly

The assembling process is automated, which produces more accurate results. In the automatic PCB assembly process, SMD support and pick-and-place pads provide precise placement and secure mounting. The lightweight SMD PCB terminals will help you maximize the efficiency of the assembly.

Connections with Stable Solder

SMD components ensure a secure hold on the board. It’s because each pole has two solder pads used by the manufacturers. Significant electronic PCB components can even be placed. To ensure that shock resistance and high vibration, manufacturers also run endurance tests. As a result, you will eventually receive a smooth and maintenance-free SMD process.

Reliable Processing

For the creation of surface mount devices, several manufacturers use LCP, a high-performance plastic. It ensures optimum dimensional stability and accurate grid alignment. The substance is highly heat-resistant to solder. So, a smooth, reliable SMD connection method is assured. In addition, in order to ensure the smooth progress of PCBA services and reduce rework costs, an AOI inspection will be performed after the surface mount installation is completed, and this inspection equipment is placed at the outlet of the reflow soldering.

Good Physical Tolerance

Due to their tight physical tolerance, SMT is more reliable while operating at high frequencies. This is solely due to the surface mount design.

SMD Component List

There are many types of SMD components, and FS Technology lists some related types below for your PCB component identification:

Discrete SMD Resistors

Surface mount resistors come in two basic variations:

  • Thick film: In contrast to axial resistors, which deposit a resistive film on a circular core, thick film surface mount resistors are made by screening resistive film on a flat, highly pure alumina substrate surface. The resistance value is calculated by altering the resistive paste composition before and laser trimming the film after screening.
  • Thin film: Tin thin film resistors have solderable terminations on the sides and a protective covering on top. They have a resistive element on a ceramic substrate. On the ceramic substrate, the stops have an adhesive layer, a nickel barrier underplating, and either a dipped or plated solder covering. The nickel barrier is crucial in maintaining the solderability of terminations.

Network Resistor (RA/RN)

High-grade ceramic chips called network resistors have metal electrodes on each end for connecting the thick film resistive element. Typically, this chip contains several resistors with comparable specifications and is excellent for digital memory circuits. 

SMD Network Resistor

SMD Capacitors

Typically, SMD capacitors are rectangular blocks with two metal pieces spaced apart by an insulator. They are energy storage devices, and the capacitance unit is the Farad (F). 

Three kinds of SMD capacitors

SMD Inductors

Inductors are the fundamental surface-mount components that transform electrical energy into magnetic energy and store it. They are made up of an insulator and an enameled wire. H is the inductance unit.

SMD Inductors


A device with two or more inductors is a PCB transformer. SMD transformers share the same structural construction, even though their designs differ significantly in voltage, current, winding capacitance, etc. 

Diodes and Triodes

Diodes have unidirectional conductivity and are polar components. As a result, there is negligible resistance encountered by the current entering from the positive electrode. If the current enters through the negative electrode, the resistance is high.

Triodes, on the other hand, serve as current amplification control components. While Q stands for triodes, D or CR stands for diodes.

SMD Diodes and Transistors


SMD integrated circuits combine elements such as diodes, capacitors, inductors, and resistors on a small semiconductor and are known as Integrated circuits (ICs).

Crystal Oscillators

Crystal oscillators are quartz devices with dual terminals that have silver coating coated on them. Their function produces an oscillation frequency that makes the device’s clock signals.

SMD Crystal Oscillators

SMD PCBA Components Specifications

Below are the various electronic SMD components’ specifications:

  • Network Resistor (RA/RN): They identify their resistor values similarly to chip resistors.
  • SMD Capacitors: Since the unit is too large for SMD capacitors, it is measured in Farad. As a result, we frequently use nF, pF, or F. For instance: o1F = 1000000μF, 1μF = 1000nF, 1nF = 1000pF, etc
  • SMD Inductors: Manufacturers provide the inductance value in the same style as resistors and capacitors. Thus, 200 denotes 20 H, whereas 203 denotes 20000 H
  • Transformers: They have surface mount headers for PCB attachment and a wire twisted around a toroidal core.
  • Triodes and Diodes: While Q stands for triodes, D or CR stands for diodes.
  • Semiconductor ICs: The semiconductor ICs are packaged by manufacturers such as SOJ, SOP, BGA, LCCC, PPGA, QFP, etc.
  • Crystal Oscillators: Crystal oscillators are denoted by the letter Y, and the SMD variety typically consists of a quartz component packaged in an IC. SMD crystal oscillators can have two or four pins.


Surface Mounted devices (SMD) have become popular because of their diversity; however, SMD components are different types, so it may be challenging to distinguish between them. We hope this article helps you understand the types and recognize SMD PCBA parts. For any questions, ask away in the comment section. 

What is the difference between SMT and SMD?

SMD Components (BOM) Souring Service

Welcome to our premier SMD components sourcing service, your trusted partner for all your electronic component needs. With an extensive network of suppliers and years of industry expertise, we offer a comprehensive range of services to meet your specific requirements. From prototyping to full-scale production, our aim is to streamline your sourcing process, reduce lead times, and ensure the highest quality components for your projects.

FS Technology – Your One-Stop SMD PCB Assembler

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