PCBA Tech - Quality control requirements during PCBA SMT processing

The PCBA processing process involves a series of processes such as PCB board manufacturing, PCB incoming components procurement and inspection, SMT processing, plug-in processing, program firing, testing, aging, etc. The supply chain and manufacturing chain are long, and defects in any link will be The quality of PCBA boards in large quantities is not good enough, which causes serious consequences. Therefore, the control of the entire PCBA patch processing is particularly important. This article mainly analyzes the following aspects.

1. PCB circuit board manufacturing

It is particularly important to hold a pre-production meeting after receiving an order for PCBA processing. It is mainly to analyze the process of PCB Gerber files and submit a manufacturability report (DFM) according to different customer needs. Many small manufacturers do not pay attention to this, but tend to prefer Here. Not only is it prone to poor quality problems caused by poor PCB design, but also a lot of rework and repair work.

2. Purchase and inspection of PCBA incoming components

It is necessary to strictly control the procurement channels of components, and must obtain goods from large traders and original manufacturers, so as to avoid the use of second-hand materials and counterfeit materials. In addition, it is necessary to set up a special PCBA incoming material inspection post to strictly inspect the following items to ensure that the components are fault-free.

PCB: Check the temperature test of the reflow oven, whether the fly-line vias are blocked or leaking, whether the board surface is bent, etc.

IC: Check whether the screen printing is exactly the same as the BOM, and store it at constant temperature and humidity.

Other commonly used materials: check screen printing, appearance, power measurement, etc.

3. SMT patch assembly

Solder paste printing and reflow oven temperature control systems are the key points of assembly, and laser stencils with higher quality requirements and better processing requirements are required. According to the requirements of PCB, some steel mesh holes or U-shaped holes need to be added or reduced, and steel mesh can be made according to process requirements. Among them, the temperature control of the reflow oven is very important for the wetting of the solder paste and the firmness of the steel mesh, and can be adjusted according to the normal SOP operation guide.

In addition, strict implementation of the AOI test can greatly reduce the defects caused by human factors.

4. Plug-in processing

In the plug-in process, the mold design for wave soldering is the key. How to use the mold to maximize the yield rate is a process that PE engineers must continue to practice and summarize.

5. Program firing

In the previous DFM report, customers can be advised to set up some test points on the PCB (test points) in order to test the circuit continuity of the circuit in the PCBA processing after all the components of the PCB are soldered. If there are conditions, you can ask the customer to provide a program, burn the program into the main control IC through the burner, and test various touch actions more intuitively, so as to verify the integrity of the entire PCBA function.

6. PCBA processing board test

For orders with PCBA test requirements, the main test content includes ICT (circuit test), FCT (functional test), burn test (aging test), temperature and humidity test, drop test, etc.