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 70 Years of Manufacturing Excellence
America's Oldest. A History of Innovation.

Over the past 70 years, the electronics manufacturing industry has changed dramatically as the industry continues to adapt to evolving demands and technology. Epec is at the forefront of innovation, with the expertise and agility to move at the speed of today’s businesses. 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 new product introduction (NPI) process that helps our customers get to market faster, 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 70 years and then some.

Learn more about our 70 year story →





Celebrating 70 Years - Epec Engineered Technologies