PCBA Tech - How to reduce the production of tin beads and dross in PCBA processing

How to reduce the production of tin beads and dross in PCBA processing
In the PCBA processing process, due to process and manual operation factors, there is a high probability that occasional tin balls and tin dross remain on the PCBA board surface, which causes great hidden dangers to the use of products, because tin balls and tin dross are in Loosening occurs in an uncertain environment, forming a short circuit of the PCBA board, resulting in product failure. The key is that this probability of occurrence is likely to appear in the life cycle of the product, which will cause great pressure on the customer's after-sales service.

The root cause of PCBA tin beads and dross

1. The amount of tin on the SMD pad is too much. During the reflow soldering process, the molten tin squeezes out the corresponding tin beads

2. The PCB board or components are damp, and the moisture will explode during reflow soldering, and the splashed tin beads will be scattered on the board surface

3. When the DIP plug-in post soldering operation, the tin bead splashed from the tip of the soldering iron is scattered on the PCBA board when the tin is added by hand and the tin is shaken.

4. Other unknown reasons

Measures to reduce PCBA tin beads and dross

1. Pay attention to the production of stencil. It is necessary to adjust the size of the opening appropriately in combination with the specific component layout of the PCBA board to control the printing volume of the solder paste. Especially for some dense foot components or board surface components are denser.

2. For PCB bare boards with BGA, QFN and dense-foot components on the board, strict baking action is recommended to ensure that the moisture on the surface of the pad is removed, so as to maximize the solderability and prevent the generation of tin beads.

3, PCBA processing manufacturers will inevitably introduce hand welding stations, which requires strict management control of tin dumping operations. Arrange a special storage box, clean the table in time, and strengthen the post-welding QC to visually inspect the SMD components around the manually welded components, and focus on checking whether the solder joints of the SMD components are accidentally touched or dissolved or the tin beads and tin dross are scattered to the yuan. Between device pins

PCBA board is a relatively precise product component, which is very sensitive to conductive objects and ESD static electricity. In the PCBA processing process, the manager of the factory needs to improve the management level (recommended at least IPC-A-610E Class II), strengthen the quality awareness of the operators and the quality team, and implement it from two aspects: process control and ideological awareness, to the greatest extent Ground to avoid the production of tin balls and dross on the PCBA board surface.
At present, the country has higher and higher requirements for environmental protection and greater efforts in link governance. This is a challenge but also an opportunity for PCB factories. If the PCB factory is determined to solve the problem of environmental pollution, then FPC flexible circuit board products can be at the forefront of the market, and the PCB factory can get the opportunity to develop again.