PCB Assembly Process: 5 Steps Help You Finish The PCB Assembly

It is magic that assembly lots of components on a small board; it is also magic that uses the small board to create a prosperous electronic world. Professional PCB assembly manufacturers made high-end PCB fabrication and assembly products, and for those who want to buy or interested in the PCBs, knowing how the PCB assembly is also necessary.

There are 5 general steps to assembly PCBs: Adding solder paste, Picking and placing the components, Soldering, Inspection, and Test.

Step 1: Adding Solder Paste

Solder paste is important for PCB assembly that is a specialized form of solder flux headed by minute solder spheres. It can be applied on the printed circuit board during the PCBA process because of its paste. Generally speaking, the solder paste was made of tin and lead, while as the development of industry and complement of legislation, nowadays, most solder particles have 99.7% tin and 0.3% copper.

The solder screen helps people put solder paste onto the printed circuit board, and you should ensure that the position is right. Then waiting for the deposition of the solder paste, and you will finish the first step of the PCBA process.

Step 2: PCB Pick and Place

After adding solder paste the PCBA process will enter the PCB pick and place that is the most important for PCB assembly. During the process of pick and place, PCB manufacturers need help from PCB assembly machines. The engineer designs accurate positions of every component for the PCB pick and place machine finish the second process of the PCB assembly process.

Awareness: In some PCB assembly processes, manufacturers may add small dots of glue to ensure the components on the printed circuit board. While these dots may create some difficulties when the printed circuit board needs to repair.

Step 3: Soldering

The soldering process of the PCB assembly aims to remain the solder paste and surface mount components in their place. Reflow soldering help solidify the solder paste and adhere components on the board. Therefore the printed circuit board which have finished the PCB pick and placed will move through an industrial-grade reflow oven by a conveyor belt. The oven will provide a heat temperature to melt the solder in the solder paste. When the melting is done, the conveyor belt will pass the printed circuit board into a series of cooler heaters.

Step 4: Inspection

After the soldering, PCB manufacturers usually make an inspection of the printed circuit board. Instead of manual inspection, automatic optical inspection is a far more viable solution. To ensure the quality of the printed circuit board, PCB manufacturers also take other inspections such as, visual inspection, and X-ray inspection to check the functionality of the board, find the lower-quality solder, and identify any potentially hidden problems. With those inspections, your printed circuit board can avoid some poor quality connections, misplaced components, and shorts due to the movement of the PCB during the reflow process.

Step 5: Test

The last process of PCB assembly is testing. The final inspection is also known as the “functional test” that issued to test the functionality of PCBs. This test creates a test circumstance for the PCB to operate. During this test, testers will monitor the electrical characteristics of PCBs, when the power and simulated signals run through the PCB in the test.

Cleaning and Packing

When you finished the PCB assembly process, there may have some amount of flux residues in printed circuit board because of the soldering process. Therefore, before you delivery the final PCB process to customers, clean the printed circuit board is necessary. Packing PCB for safe delivery is also important. When you finish the cleaning process, utilizing compressed air to dry the board. Then you finish the whole PCB assembly process.


All the PCB assembly process should be arranged after the PCB manufacturing. And if you want to create a high-quality PCB board, there are other processes you should consider. Before the PCB assembly process, you should design for manufacturability(DFM) check and electronic components checking.

  • Design for manufacturability(DFM) checks:

In this process, manufacturers will check the PCB design to analyze any missing, redundant, or potential problems. This process can check any design errors, give time to designers to correct any flaws.

  • Electronic components checking:

Before the PCB assembly our engineer team will check the packaging, value, quality, part number, the footprint of the components, and ensure they match with the BOM and the PCB board to avoid any mistakes before PCB assembly start.

UETPCB is a professional PCB fabrication and assembly manufacturer in China with more than 15 years of experience. We provide custom PCB service, turnkey PCB assembly, prototype PCB service, and are trying to satisfy all requirement of our customers.

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