PCB Technical - Why is the solder joint invalid in PCBA processing?

PCBA processing solder joints are invalid because of poor electronic component pins, flux quality defects, unqualified residues, and air oxidation; in addition, the quality control method is to submit a manufacturability report (DFM) according to different customer needs. Next, I will introduce the details for you.

PCBA processing solder joints are invalid because of poor electronic component pins, flux quality defects, unqualified residues, and air oxidation; in addition, the quality control method is to submit a manufacturability report (DFM) according to different customer needs.

1. Why is the solder joint invalid in PCBA processing?

1. Poor positioning of electronic devices: coating, environmental pollution, air oxidation, common points.

2. PCB welding layer is not good: coating, environmental pollution, air oxidation, expansion and contraction.

3. Welding material quality shortcomings: composition, unqualified residue, air oxidation.

4. Disadvantages of flux quality: low flux, high erosion, low SIR.

6. Disadvantages of other auxiliary materials: adhesives and detergents.

Second, how to control the quality of PCBA processing

1. It is particularly important to hold a pre-production meeting after receiving an order for processing PCBA. It is mainly the process of analyzing PCB Gerberfiles and submitting manufacturability reports (DFM) according to different customer needs. Many small manufacturers do not pay much attention to this. But this is often the case. It is not only easy to cause quality problems due to poor PCB design, but also a lot of rework and repair work.

2. Purchase and inspection of electronic components provided by PCBA

The procurement channels of electronic components must be strictly controlled, and goods must be obtained from large traders and original manufacturers to avoid the use of second-hand materials and counterfeit materials. In addition, it is necessary to set up a special PCBA incoming inspection station to strictly check the following items to ensure that the components are fault-free.

PCB: Check the temperature test of the reflow oven, whether the through holes without flying leads are blocked or leaking, whether the surface of the board is bent, etc.

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

3. SMT assembly

Solder paste printing and reflow oven temperature control systems are key points in assembly, and laser templates with higher quality requirements and higher processing requirements are required. According to the needs of PCB, some need to increase or reduce the steel mesh or U-shaped holes, only need to make the steel mesh according to the 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 AOI testing can greatly reduce defects caused by human factors.

4. Plug-in processing

In the plug-in process, the mold design of wave soldering is the key. PE engineers must continue to practice and summarize how to use molds to maximize productivity.

5. PCBA processing board test

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