How to find the best PCBA manufacturers?

There will be many kinds of bad phenomena in the SMT process, and cold welding is one of the bad defects. The following will introduce what is cold welding, the causes of cold welding, and the solutions to cold welding, so as to help you effectively control the bad cold welding question.

What is cold welding?

Cold soldering is due to the fact that the solder at the soldering point does not reach its melting point temperature or the soldering heat is not sufficient during the reflow soldering process of the circuit board SMT process, so that it is solidified before wetting or flowing, and no metal alloy layer is formed at all. All or part of the solder is in an amorphous state and simply accumulates on the surface of the metal to be welded.

SMT processing cold welding causes:

1. The heating temperature is not suitable;

2. Deterioration of solder paste;

3. Preheating is excessive, the time is too long or the temperature is too high;

4. Due to surface contamination, the flux ability is limited;

5. Insufficient flux capacity

Solutions for SMT processing to produce cold welding:

1. Adjust the reflow soldering temperature curve;

2. Replace with new solder paste;

3. Improve the preheating conditions;

4. Surface contamination on and around pads or pins will inhibit flux capability resulting in incomplete reflow and should be resolved with proper post-plating cleaning process;

5. Insufficient flux capacity will result in incomplete removal of metal oxides and subsequent incomplete coalescence, similar to surface contamination.