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.


Figure 1: Dark stripes on the solder mask after selective soldering
Figure 1: Dark stripes on the solder mask after selective soldering.


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.

Celebrating 65 Years of Manufacturing Excellence  Learn More →
America's Oldest. A History of Innovation.

Today at Epec, the customer comes first, and everything we do must be put through that filter. Whether it is developing e-commerce platforms to make it easier to work with us, or creating a NPI (new product introduction) process that helps our customers get to market faster, or the other 10 new projects we have in process, we must focus on building the new. By doing that every day, and by always making the customer our top priority, we plan on being here for another 65 years and then some.

Learn more about our 65 year story →



Celebrating 65 Years - Epec Engineered Technologies