The Different Types of PCB Assembly Processes

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Printed circuit boards are the cornerstone of modern electrical design evolution. Have you noticed how technology is becoming smaller and more compact in size? From simple cell phones to complicated medical technology, every electrical product moves towards enhanced functionality while reducing in size.


Well, that has been achieved by integrating printed circuit boards into application designs. Compared to traditional circuit boards, printed circuit boards allow for the utilization of less space, increased electrical output, and long-term device reliability.


As a result, many companies have entirely shifted towards manufacturing printed circuit boards. So how are they built? What is circuit card assembly or PCB assembly process? Are there different types of PCB assembly processes? Read this article to find out.


PCB Assembly Process or Circuit Card Assembly


The process of fabricating printed circuit boards is referred to as the PCB assembly process. While the terms PCB assembly process, PCBA (printed circuit board assembly), and circuit card assembly (CCA) are used interchangeably, the IPC approved term is circuit card assembly.


Circuit card assembly refers to printed circuit boards that have the components attached to them, while the process of mounting and soldering said components is called the PCB assembly process.


Although the steps for a PCB assembly process are more or less standardized, the different types of components require modifications to certain steps. Needless to say, all different types of PCB assembly processes are moving towards automation. Companies like Hemeixin Electronics use automated steps in a PCB assembly process to ensure precise and accurately designed printed circuit boards.


In this article, we will discuss three basic types of PCB assembly processes, which are:


i. Surface Mount Technology (SMT) Assembly Process
ii. Through-Hole Technology (THT) Assembly Process
iii. Mixed Technology


Surface Mount Technology Assembly Process


Surface mount technology refers to the use of surface mount devices (SMDs) for the fabrication of printed circuit boards. SMDs are very popular these days since they can be mounted directly onto a PCB with the help of solder paste.


They’re easy to work with as compared to thru-hole components, and using SMT in a PCB assembly process involves the following steps:


1. Solder Paste Stenciling


Solder paste is a mixture of metallic grains and an electrochemical called flux. It helps solder the components to a PCB. Solder paste is applied to parts of printed circuit boards where components have to be attached. A solder screen or stencil helps in the precise and accurate application of the paste to areas where components will mount.


2. Pick and Place


An automated pick and place station moves the PCBs along a conveyor belt and mounts the SMT components onto the circuit boards. The machine stores the components in reels and rotates to supply the correct amount for the correct location.


3. Reflow Soldering


The complete circuit card assembly is moved through a reflow oven equipped with heaters and coolers. The circuit card assembly is heated to melt the metal grains in the solder paste and then readily cooled, so the paste solidifies. An important step in the PCB assembly process, it helps the components tightly adhere to the printed circuit boards.


Through-Hole Technology Assembly Process


It is an outdated technology but is useful in certain applications. Thru-hole technology uses pin-thru-hole components (PTH) inserted via drilled holes in printed circuit boards. Their ends are fixed on pads on the other side of the PCB and are soldered in place. Double-sided PCBs cannot be fabricated using thru-hole technology, which is part of the reason for its decreasing popularity. The steps of a THT PCB assembly process are as follows:


1. Component Placement


The PTH components have to be manually installed. Design engineers carry out the process with precision and accuracy based on the client's design files. Adherence to the thru-hole assembly standard is required to guarantee quality products.


2. Inspection


A matching transport frame is placed on the circuit card assembly to visually inspect any misplaced components, which are then rectified. Inspection is an important step in all types of PCB assembly processes.


3. Wave Soldering


Wave soldering uses a solder machine in which printed circuit boards are slowly moved over a wave of liquid solder at high temperatures. The cooled-down solidified solder holds all the pin-thru-hole components on the other side of the PCB.


Mixed PCB assembly Technology


As previously mentioned, technology is becoming advanced, and, as a result, different types of components have to be used in single application designs. So, the chances are that an application might require a circuit card assembly with both SMT and PHT components. This called for mixed technology assemblies. Mixed technology boards employ both thru-hole and surface mounting technology. We will discuss single-sided, one-side SMD/one-side THT, and double-side mixed assembly processes.


Single Side Mixed Assembly


Both surface mount components and pin-thru-hole components are installed on one side of a PCB as follows:



One Side SMT/ One Side THT


This PCB assembly process involves just one additional step:



This PCB assembly process is rarely recommended since the use of adhesives instead of reflow soldering might lead to soldering issues.


Double Side Mixed Assembly


The circuit card assembly has to be heated three or more times, resulting in low efficiency. This PCB assembly process is also very costly.

These were some of the types of PCB assembly processes. All these different types do involve a final inspection followed by a functional step to ensure the proper working of printed circuit boards. Depending on your application design, you might need to follow a specific PCB assembly process. We recommend getting in touch with a professional PCB fabricating company like Hemeixin Electronics.


Hemeixin Electronics is a one-stop-shop solution for all your PCB design needs. They offer state-of-the-art printed circuit boards which are custom built. Their printed circuit boards undergo rigorous testing and quality control checks to ensure that you receive a product worthy of your application designs and requirements. In addition, they use the best equipment and materials in all types of PCB assembly processes and the printed circuit boards themselves. At Hemeixin, your satisfaction is given top priority, while design engineers aspire to bring you affordable yet the best market solutions! Contact Hemeixin Electronics today and get a quote!

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