Wave Soldering Defects

Solder Mask Discoloration on a Printed Circuit Board

Normally this is a cosmetic issue but should be investigated for the real cause. When running a thicker board it is probable that the soldering process or dwell times may have changed.

The most common reasons for this occurrence include:

• Different flux used, higher temperature, longer dwell time or boards were run twice in pallet
• Solder mask/resist type, thickness or cure cycles have changed
• PCB supplier has been changed, or mixed batches of boards

There is no reference to the board finish, solder alloy being used or flux type - water or alcohol based. These are important when conducting analysis of the process problem.