What Is PCB Assembly Process

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Understand the PCB Assembly Technologies

Assembling a printed circuit board requires more than just the raw components and a well-designed board. It also requires the right technology. In this case, there are several options to choose from, and each brings something different to the table. For instance, there’s surface mount technology (SMT), as well as manual soldering, and the use of pick and place machines.

While some PCB assembly processes will require just one technology, others will require a combination of two or more technologies. For example, many boards require the combination of through-hole technology (THT) and surface mount technology. Understanding when, where, and how to integrate those technologies is a critical consideration when choosing a company to handle your project or production.

It’s also important to understand that the PCB assembly steps involved with the various technologies differ, as well. Below, we’ve outlined some basic steps involved, as well as how they differ from technology to technology.


The basic PCB assembly proceeds in the following way.


Solder Paste Application

The paste solder grains mixed with flux is applied on the baseboard of the PCB. The stencils of different sizes and shapes are utilized to ensure the application of paste on the specific locations only.

Component Placement

The small electronic components of the circuit are placed on the solder pasted board, either manually or automatically, with the help of pick and place robotic mechanism.

Reflow: The solidification of the solder paste is performed in the reflow process. The PCB board with mounted components is passed through a reflow oven that has over 500° F temperature. Once the solder paste is melted, it is taken back to the conveyor and solidified by exposing it to a cooler.


This follows the post reflow process. The inspection is performed to check the functionality of components. This stage is important as it helps identify misplaced components, poor quality connections, and shorts. Generally, misplacements occur during the reflow process. The PCB manufacturers employ manual checks, X-ray inspection, and automated optical inspection at this stage.

Through-hole part insertion

Many circuit boards require the simultaneous insertion of through-hole and surface mount components. So, in this step that that is accomplished. Generally, the through-hole insertion is performed using wave or manual soldering.

Final inspection and cleaning

Finally, the PCB board is inspected for its electronic potential by testing it under different currents and voltages. Once the PCB board passes this inspection this stage, it is washed with deionized water as soldering leaves some residues. After washing it is dried under compressed air and a fine product is packaged.

The Right PCB Assembly Process for You

While the SMT assembly process is faster and often more accurate than either the traditional PCB assembly process, it is not always the best option. Each situation varies and there is no single solution that will always work for every need.

At Advanced Circuits, we understand that needs, budgets, and goals vary. We pride ourselves on offering exactly the solutions each client needs. Whether you’re producing a single prototype for proof of concept needs or you’re ready to move into full production with thousands of units being produced, we can help. Contact us today to schedule your consultation or to learn more about our services and capabilities.

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