SMT pad design is a very critical part of PCB design. It determines the soldering position of the components on the PCB, the reliability of the solder joints, the soldering defects that may occur during the soldering process, the clarity, testability and maintainability Waiting to play a significant role. If the PCB pad design is correct, a small amount of skew during mounting can be corrected due to the self-correction effect of the surface tension of the molten solder during reflow soldering. On the contrary, if the PCB pad design is not correct, even if the placement position is very accurate, there will be soldering defects such as component displacement and tombstone after reflow soldering. Therefore, pad design is one of the key factors that determine the manufacturability of surface mount components. Common pads are a “common disease and frequently-occurring disease” in PCB design, and it is also one of the main factors that cause hidden dangers in PCB soldering quality.

What are the effects of common pads on PCB soldering quality

1. After the chip components are soldered on the same pad, if the pin plug-in components or wiring are soldered again, there is a hidden danger of false soldering during the secondary soldering.

2. The number of repairs during subsequent commissioning, testing and after-sales maintenance is limited.

3. When repairing, unsoldering a component, the surrounding components of the same pad are all unsoldered.

4. When the pad is used in common, the stress on the pad is too large, causing the pad to peel off during soldering.

5. The same pad is shared between the components, the amount of tin is too much, the surface tension is asymmetric after melting, the components are pulled to one side, causing displacement or tombstones.

6. Similar to the non-standard use of other pads, the main reason is that only the circuit characteristics are considered and the area or space is limited, which leads to a lot of component installation and solder joint defects in the assembly and welding process, which ultimately affects the reliability of the circuit. Big impact.