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Wave Soldering Defects - Solder Mask
Discoloration
A user recently submitted the following defect:
We have found that after selective soldering
dark stripes remain (figure 1) on the solder mask for our 8 layer
board (2,4mm thickness). Do you have any
explanation or info that might help to solve this problem? Can
you tell us if this is a quality problem?
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| Figure 1: Dark stripes on the solder mask after selective
soldering. |
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.
Wave Soldering Defects:
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Poor Penetration | | |
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