I would appreciate some help here from you guy's & gal's!

*OK.  You asked for it....

On considering the switch from using RMA flux for Class 3 to OA-(WS) for
board assembly a full SIR testing exercise has been carried out
externally IAW IPC-TM-650 using appropriate test coupons; this proved
satisfactory.

*OK, so what does passing this SIR indicate to you.  To me, it indicates that an OA flux was put on a flat test coupon (B-24),
soldered and cleaned, then SIR tested.  It tells me that it meets at least the SIR requirements of J-STD-004.  Now the big question,
do you feel that the lab results on an FR-4 bare copper coupon with no components adequately represents your product, which
may be on another laminate, probably solder masked, probably tin-lead coated?  I wouldn't.  Most of the IPC materials
characterization tests are interested in creating a level playing field for fair comparison.  In the case of J-STD-004, you know
that Alpha, Kester, Multicore, etc., all tested the same way on the same substrate (at least in theory).  It does NOT address the
question of whether you or your supplier can intelligently use that flux on real product.  As an example, we use Alpha UP-78 as
one of our standard pastes here at Rockwell.  A damn fine material and almost bulletproof, but at CSL I saw some users process
it too cold or too fast through reflow and got bad results.  J-STD-004 results were fine.  Operational results were bad.  This is why
I have been an advocate of tests similar to J-STD-001 Appendix B, using a process qualification vehicle.  One of the task groups
at IPC is developing the CSL Umpire board for that purpose.  You might consider using it, rather than B-24 boards.

ROSE testing will be used locally as a form of process control but I was
wondering whether their would be benefit in using ion chromatography to
assess the first off's pucker hardware...........maybe one for you Doug!

*I would say that yes, IC would be beneficial and worth the cost.  You need a true measure of cleanliness to assess acceptability
and you need to have some good data upon which to set your ROSE process control limits.

Doug Pauls
Rockwell Collins

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