Detailed guide for PCBA processing

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The PCBA processing process covers the entire process from raw material procurement to finished product shipment, including SMT chip mounting, DIP plug-in processing, PCBA testing, three-proof coating, and finished product assembly. Each step strictly follows the process requirements to ensure the quality and performance of the final product. In this article, we will detail the manufacturing process of PCBA, with the specific contents as follows.

SMT Chip Mounting Process

The process of SMT chip mounting includes: solder paste mixing → solder paste printing → SPI → mounting → reflow soldering → AOI → rework.

  1. Solder Paste Mixing

After taking the solder paste out of the refrigerator and thawing it, it is mixed manually or by machine to be suitable for printing and soldering.

  1. Solder Paste Printing

Place the solder paste on the steel mesh and use a scraper to print the solder paste onto the PCB pads.

  1. SPI

SPI, namely solder paste thickness detector, can detect the printing condition of solder paste, playing a role in controlling the effect of solder paste printing.

  1. Mounting

Various components are automatically mounted on the circuit board using machine equipment.

  1. Reflow Soldering

The assembled PCB board is reflow soldered, where the solder paste is heated to become liquid through high temperature inside and then cooled and solidified to complete the soldering.

  1. AOI

AOI, namely automatic optical inspection, can scan and detect the soldering effect of the PCB board, identifying any defects.

  1. Rework

Defects identified by AOI or manual inspection are reworked.

DIP Plug-in Processing Process

The process of DIP plug-in processing includes: plug-in → wave soldering → trimming → post-solder processing → cleaning → quality inspection.

  1. Plug-in

Process the pin of the plug-in material and install it on the PCB board.

  1. Wave Soldering

Pass the assembled board through wave soldering, where liquid tin is sprayed onto the PCB board, and then cooled to complete the soldering.

  1. Trimming

The pins of the soldered board need to be trimmed if they are too long.

  1. Post-solder Processing

Manual soldering of components is performed using an electric soldering iron.

  1. Cleaning

After wave soldering, the board may be dirty and requires cleaning using cleaning solution and washing tank, or by using a cleaning machine.

  1. Quality Inspection

Inspect the PCB board, and defective products need to be reworked before qualified products can proceed to the next process.

PCBA Testing

PCBA testing includes ICT testing, FCT testing, aging testing, vibration testing, etc.

PCBA testing is a comprehensive process, and the testing methods adopted vary depending on the product and customer requirements. ICT testing checks the soldering of components and the continuity of circuits, while FCT testing examines the input and output parameters of the PCBA board to ensure compliance with requirements.

PCBA Three-proof Coating

The process of PCBA three-proof coating includes: brushing Side A → air drying → brushing Side B → room temperature curing. The spraying thickness is 0.1mm to 0.3mm. All coating operations should be carried out under conditions of not less than 16°C and relative humidity below 75%. PCBA three-proof coating is widely used, especially in harsh environments with high temperature and humidity. The coating provides excellent insulation, moisture resistance, leak resistance, shock resistance, dust resistance, corrosion resistance, anti-aging, anti-mildew, anti-loosening of components, and insulation against electric arcing. It can extend the storage time of PCBA, isolate external erosion, pollution, etc. Among them, the spraying method is the most commonly used coating method in the industry.

Final Assembly

The PCBA boards that have been tested OK after coating are assembled into the outer casing, followed by testing, and finally ready for shipment.

PCBA production is a chain of processes, and any problem in any link can have a significant impact on the overall quality. It requires strict control over each process.

 

Overall, PCBA processing requires meticulous attention to detail and adherence to industry standards to produce reliable and high-quality electronic devices.