-Steve Gregory- SAID ............
SNIP.....................
I took some more pictures this morning of something else, if anybody wants to
take a look and give an opinion. They have to do with that Dry-Film mask
adhesion problem that I talked about earlier. I've got a picture of one board
that has the mask flaked off, and one of a board that looks the way it's
supposed to. The Fab house continues to say it's our cleaning process,
because of the Kyzen Aquanox XJN that we use. The board that I took a picture
of that looks good, came from the latest replacement lot that they sent us.
It doesn't have any components mounted on it, but I ran it through the reflow
and did a tape test...no mask came off. Then I ran it through the MCS-1000
cleaner and did another tape test...no mask came off. The picture of the
board that has the mask coming off has components mounted on it, and the mask
has completely come off from every bit of copper...all the traces and the
via's, both on the top and the bottom of the board. From what I understand,
this problem has cost us over 30K...and the fab vendor still is sticking by
their guns saying that it's us, not them...help!
...............................................
Okay, steve, but you don't want to hear this.
Kyzen Aquanox XJN, and its kin, such as SSA, A4000, and all other Aquanox
series Kyzen materials
are basically incompatible with dry film soldermask due to the alkaline nature
of the chemistry.
Kyzen makes other solvent cleaners in its Ionox line, FC and BC to mention
two, that depend strictly
on the solvency of the chemicals to deflux a PWB\CCA. When we did early work
with SSA, we found
this out in a rather painful way. Our short term cure was to batch clean in
BC with an IPA rinse,
followed by a DI rinse. Long term solution was to discontinue use of dryfilm.
Dryfilm was also
discontinued previously in older days due to incompatibility with 1,1,1 and
for other reasons.
Your symptoms are classic. The dryfilm will be attacked all over, but will
penetrate first where the
dryfilm bends over traces. This area is either thinner, or has micro-cracks.
Once compromised, the
power of the wash will lift the dry film from the copper due to the lower
adhesion. Continued
washing will eventually leave all the dryfilm surface pitted as the soldermask
erodes away.
Variations in attack on bare PWBs versus finished CCAs may be due to exposure
to reflow and
its impact on the surface of the dryfilm. It may also reflect the cumulative
effect of multiple cleanings.
On the bare PWBs, mask an area with kapton tape, and wash 4 times, inspecting
with a decent
scope each time. Compare the protected surface with the exposed surface,
looking for pits.
If the soldermask can survive without pitting, try the same thing after one or
two reflow cycles.
If the dryfilm can survive these tests, I'll be surprised.
The cleaner you use, the Electrovert MCS-1000 may be retrofitted to use FC or
BC.
Steve Mikell
Lead Ind Eng
Plant 13
SCI Systems
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