What is insufficient wetting?
Wetting refers to the process where the solder melts and adheres to the metal on the PCB and the component pin/lead. With insufficient wetting, the solder melts but does not bond properly to either the PCB pad or the pin.
This usually happens because the circuit board has contaminants, or the pad or pin was not heated up properly, causing the solder to cool down before it can bond with the pad/pin.
Types of Insufficient Wetting:
Insufficient Wetting of the Pad
The solder surrounds the pin but does not adhere to the pad
Insufficient Wetting of the Pin
The solder flows smoothly over the pad, but does not connect properly to the pin.
Insufficient Wetting of Surface Mount
Solder does not flow evenly over the rows of SMT pins. Inconsistencies can be seen in the solder joint.
How to prevent or fix an insufficient wetting?
- Keep the board clean before soldering to ensure no contaminants can affect soldering.
- Ensure even and sufficient heat-up by using the soldering iron tip to touch both the pad and the pin.
- Using flux on the pin and pads can increase the wetting ability of the solder by allowing for smoother flow.
- For surface mount components, it may help to heat the pad before the pin to allow the entire pad to heat up consistently.