What is the assembly process of PCB

The advancement of modern technology has made our working life more convenient, and the great development of the electronics industry has fundamentally changed our lives. Of course, the development of the electronics industry is also inseparable from the development of printed circuit boards. The core component of electronic equipment used by people is the printed circuit board.

PCB is usually green, a rigid body with various electronic components on it. These components are welded to PCB during the “PCB assembly” or PCBA process. PCB is composed of substrates, components, components, copper wiring layers, mounting holes, and inner and outer layers.

PCBA refers to the process of installing, plug-in and welding PCB boards for components. The PCBA production process must be completed throughout the process. This article describes all PCBA production processes.

PCB assembly process

PCBA refers to the overall structure after welding electronic components (including SMD patch components and DIP plug-in components) on the basis of PCB bare board.
PCBA production processes can be divided into several large processes. SMT patch processing → DIP plug -in processing → PCBA test → three anti -coating → finished product assembly.

1. SMT patch processing link

The process of SMT patch processing is: tin paste stir → tin paste printing → SPI → sticker → return welding → aoi → repairs

(1). Stir

After thawing the tile paste from the refrigerator, stir it by hand or machine to print and weld it.

(2). Ten paste printing

Place the tile paste on the steel mesh and print the tin paste on the PCB pad by spatula.

(3). SPI

SPI is the thickness detector of tin paste, which can detect the printing of tin paste and play the purpose of controlling the effect of tin paste.

(4). Paste
The machine and equipment place the relevant electronic components on the PCB. With the improvement of production technology, fully automated machinery and equipment have completely replaced manual placement and achieved fast and accurate components. These robots can work around the clock without feeling tired.

(5). Back welding

The installed PCB plate is overwritten. After the high temperature effect inside, the tin paste shaped paste is heated into liquid, and finally cooled and solidified to complete the welding.

(6). AOI
AOI is automatic optical detection. It can detect the welding effect of the PCB board by scanning, and the lack of the board can be detected.

(7). Rebate
Rebate poorly detected AOI or manually.

2. DIP plug-in processing link

The process of DIP plug -in processing is: plug -in → peak welding → scoop -cutting → post -welding processing → scrubbing → check

(1). plug -in
Pour the plug-in material pins and insert them on the PCB board

(2). Wave welding
The inserted board is welded over the peak, and this process will be sprayed on the PCB board with liquid tin, and the welding will be cooled.

(3), cut feet
The pins of the welded board need to be cut for too long.

(4). Post-welding processing
Use electric soldering iron to weld the components.

(5). Washing board
After welding, the boards will be dirty. They need to be cleaned with laundry water and laundry slots, or use machines for cleaning.

(6). Examination
Check the PCB board, and unqualified products need to be repaired, and qualified products can enter the next process.

3. PCBA test

PCBA tests can be divided into ICT tests, FCT tests, aging testing, vibration testing, etc.
The PCBA test is a big test. According to different products, different customer requirements, the test methods used are different. The ICT test is to detect the welding of components and the throughout of the line, and the FCT test is to detect the input and output parameters of the PCBA board to check whether it meets the requirements.

Fourth, PCBA three anti-coating
The step of PCBA three anti -coating process is: apply A side → dry → apply B side → room temperature curing 5. Spray thickness: spray thickness: 0.1mm — 0.3mm6. All coating operations should not be less than 16 ° C and 16 ° C and 16 ° C. Relative humidity is less than 75%. There are still many PCBA three anti -coating, especially in some environments with harsh temperatures and humidity. PCBA coating three -proof paint has superior insulation, moisture -proof, leakage electricity, shock -proof, dust-proof, anti -aging, mildew -proof, mildew -proof prevention. The performance of anti-part loosening and insulation resistance can extend the storage time of PCBA, isolation of external erosion, pollution, etc. The spraying method is the most commonly used method in the industry.

Five, finished product assembly
After the coating is tested, the OK PCBA board is assembled for the shell, and then the test is performed. Finally, it can be shipped.
PCBA production is a ring buckle, and any part of any link will have a great impact on the overall quality. It is necessary to strictly control each process.