PCBA Tech - How to reduce the tin ball and dross on PCBA board surface?

How to reduce the tin ball and dross on PCBA board surface?

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 ball tin dross

1. There is too much tin on the SMD pad. During the reflow soldering process, the tin is melted and the corresponding tin bead is extruded

2. The PCB board or components are damp, 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 soldering operation is performed manually, the tin beads splashed from the soldering iron tip are scattered on the PCBA board surface when the tin is added by hand.

4. Other unknown reasons

Measures to reduce PCBA tin beads and dross

1. Pay attention to the production of stencils. It is necessary to adjust the size of the opening appropriately in combination with the specific component layout of the PCBA board, so as 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 is recommended to ensure that moisture on the surface of the pad is removed, to maximize solderability and prevent the generation of tin beads

3. PCBA processing manufacturers will inevitably introduce hand welding stations, which requires strict management control over 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 more precise product component, which is very sensitive to conductive objects and ESD static electricity. In the PCBA process, factory managers need to improve their management level (at least IPC-A-610E Class II is recommended), strengthen the quality awareness of operators and quality teams, and implement them from two aspects: process control and ideological awareness, to the greatest extent Avoid the production of tin beads and dross on the PCBA board surface.