The impact of PCB solder mask design on PCBA processing

We all know that PCBA is to attach components to the PCB board through the SMT process. Then PCBs designed with different processes will have different impacts on PCBA processing. Today, let’s discuss the impact of PCB solder mask design on PCBA processing.

Both sides of the PCB board are copper layers. PCB boards without solder masks are easily oxidized when exposed to the air and become defective products, which also affects the electrical performance of the PCB board. Therefore, there must be a protective coating on the surface of the PCB circuit board that can block the oxidation reaction between the PCB and the air, and this coating is the solder mask covered with solder mask paint material. The role of the solder mask in controlling welding defects during the PCBA welding process is very important. PCB designers should try to reduce the spacing or air gap around the pad features. Improper PCB solder mask design will lead to the following PCBA defects.

1. The solder mask is too thick and exceeds the thickness of the PCB copper foil pad, forming a suspension bridge and open circuit during reflow soldering.

2. The solder mask processing is poorly aligned with the pad, resulting in contamination of the pad surface, poor solder joint tinning or a large number of solder balls.

3. When there is a wire passing between two pads, a PCB solder mask design should be adopted to prevent soldering short circuits.

4. When there are more than two SMDs close to each other and their pads share a wire, a solder mask should be used to separate them to prevent stress caused by solder shrinkage that may cause the SMD to shift or crack.

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