Greetings

Did you tape test it?  Hard to tell if it really is exposing from pics. You
also appear to have soda-strawing-is it running along the trace edges?

Fab house could have alot of different issues that might cause this, and
improper cure, or a contaminat preventing proper cure is certainly the most
likely-Fully cured and bonded Mask or LPI is a beast to get off.  If you
have breakdown its most likely not your process but theirs.

Some panels being dirty-poor pre-clean prior to application of the ink.
Incomplete drying after pre-clean, leaving moisture on the panels that was
then trapped and heated at wave.
If they were not spaced properly in the oven, or if they tried to cure too
many at one time in the same oven.
A change in ink batch-as in bad batch of ink.  (Though probably not in this
case_
Oven mechanics, loss of constant temperature, clogged air filter, if so
equipped.
New operator, or department supervisor alos tends to affect finished
quality, when the issue is not immediately detectable.

Any of these can result in good board bad board problems long before you
introduce assembly chemistry to a pre-existing reliabilty problem.  I
suggest you query them (Fab house) and then amaze them with your tech-net
compiled list of friendly suggestions.

The thermal excursion activated something under the mask, probably moisture.

Steve M

----- Original Message -----
From: "Barmuta, Mike" <[log in to unmask]>

Subject: Re: [TN] Intermittent solder mask problems, again.


> Charlie: Things to consider to better answer the question:
>
> 1. Is the problem on both sides of the board or just the wavesolder side?
>
> 2. Are the boards from the same or different dates/builds from the bare
> board fabricator?
>
> 3. Do these boards get both a thermal and U/V cure from the fabricator?
>
> 4. If you run a non-wavesoldered board (if possible from the same fab
date)
> thru the wash do you see the same effect?
>
> 5. 3 Ft/min thru wavesolder is pretty slow, depending on your preheat. Can
> you check on top/bottom side max temps prior to hitting the solderwave?
>
>
> I would guess that possibly the soldermask was not properly cured and the
> flux and heat in wavesolder may be reacting with it in addition to your
wash
> chemistry finally pushing it over the top.
>
>
>
> Regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett WA
>
> 425-446-6076
>
>

>
> Can anyone share process issues with Enthone solder mask? The customer has
> used my saponifier for just over a year with no issue like this.
>
> Flux used is Alpha RF800  (foam fluxer) pre-heat at 225 F and solder pot
at
> 490 F  w a conveyor speed of 3 ft / min,
>
> Saponifier  wash concentration was 10 %, temp at 120F, for 10 mins. Solder
> mask used is Enthone DSI 41G.
>
> Please explain on a batch of 50 boards, 5 were perfect, 5 were very bad
with
>
> solder mask peeling, and 40 in the middle with minimal fading.
>
>  All the processes were the same for all, all sat for 1-2 days after wave
> solder.
>
> Where the board was masked for secondary attachment ( mask removed prior
to
> clean) and also shadowed by the wave fingers there is no changing of the
> overall green color.
>
> If the wash chemistry is the culprit then it would affect every board and
in
> a uniform fashion. I have photos to share, maybe Steve G.  will let me
post
> them on his sight?
>
> My suspicions are, incorrect cure, application etc. of the Enthone mask.
>
> Thanks in advance.
>
>
> Charlie Pitarys
> Director of Application Technologies
> 603.622.2900 X-115
> www.kyzen.com <http://www.kyzen.com/>
>

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