This message is directed to circuit card assembly shops and printed wiring 
board manufacturers.

We are a medium sized company that designs and manufactures CCAs for commercial
and military applications.  We currently have four different manufacturers of 
PWBs.  We are experiencing a problem with one type of soldermask that is 
provided by our vendor of choice.  The soldermask is liquid photo imagable 
and is IPC-SM-840 class 3 certified.  The name of the soldermask is PSR 4000 
manufactured by Taiyo America.

Our vendor feels that the soldermask is deteriorating after our semi automated 
saponified aqueous cleaning process.  Over copper substrates the soldermask 
develops small white spots that range in size approximately .010 to .020 inches
in diameter.  Soldermask covering copper traces.010 to .015 inches wide has 
turned white over 50 to 80% of the trace length.  This occurs both over the 
solder side and component side of the PWB.  The deteriorated soldermask on the 
traces then looses adhesion to the copper traces leaving bare copper exposed.

Our assembly process is as follows: 
1. Cure bake PWBs ( to recommended parameters set by the vendor to "condition" 
the soldermask.)
2. Install SMT components by hand.  ( RMA flux.)
3. Install the through hole components.
4. Wave solder CCAs. ( Or hand solder if wave soldering is not feasible. 
RMA flux.)
5. Clean CCAs using the batch washer.  ( Semi-aqueous method using De-Ionized 
water and Armakleen E-2001A saponifier.)

The washer recipe is as follows:  ( CCAs are washed in a Unit Design model 
ABC 2001 machine.)
1. Wash cycle. Duration 4 min., temperature 165 F, 4% saponifier solution added.
2. Quantity 3 rinse cycles.  Duration 1 min., temperature 165 F, 0% saponifier
solution added.
3. Dry cycle.  Circulating fan. 15 minutes at 150 F.

The pH value for the washing solution is 10.8.

This problem was first noticed about 9 months ago and only on one vendors PWBs.
At that point discussions with the PWB vendor and soldermask manufacturer 
resulted in adjustments to our curing parameters and wash recipes.  The problem
did not totally disappear but dissipated to a level that was acceptable.  The 
problem has resurfaced this week with a vengeance.

I am interested in any feedback on occurrences of this problem and solutions. 
Specifically these questions.

1. Are we the only people in this industry that are experiencing this problem?
2. Is our cleaning process indeed causing the damage, or is it a process 
problem with our vendor?
3. Is our saponified aqueous cleaning harmful for IPC-SM-840 class 3 LPI's 
in general?

Thank you for your anticipated responses.

Ron Rawlyk
Manufacturing Engineering
SED Systems Inc.
306 933-1688
rawlyk @ sedsystems.ca