Hi Tecnetters,
I hope you all
had a good X-mass.
One of my colleagues asked me to present a
question to this forum.
We are manufacturing PCBs with
electroless nickel - immersion gold ( ENIG ) finishing, using Atotech chemistry
. Most of the boards are very dense SMD , fine pitch , BGA etc . All
boards are passing through ECT and visual inspection before ENIG .
According to him, we are facing ,
from time to time , a phenomena of plated ENIG on the Solder Mask and /or on
text, resulting in shorts ( which are extremely small) .
These shorts cannot be found by
visual inspection, only by ECT.
The changes we made so far in
our production in order to minimize the problem are:
1 ) Higher exposure
energies and longer curing time for Solder Mask
2 ) Lowering activation (
palladium ) before electroless nickel
3 ) Improving rinses (including
agitation) , after palladium
But still we are getting these shorts from time to time
We think that considering the
ENIG process , we are close to skip most plating problems
.
If any of you, wise ones, has a
practical advice as to eliminating our problem, we will be
grateful.
Best regards,
Yehuda
Weisz