6/20/2002

Folks is anyone manufacturing military PWAs using no-clean flux and not cleaning the PWAs prior to shipment?  If so, what is your reliability experience with this process?

We are considering a military application (Class 2) where mixed technology (SMT and PTH) PWAs will be soldered using no-clean flux and then not conformal coated (assuming the uncoated PWAs can pass our temperature/humidity qualification testing).  Although the no-clean flux we will use should be benign (we are having SIR testing performed to confirm this and Omegameter testing), I am concerned that contamination may be introduced by other shop processes such as mechanical assembly, testing, etc., even if one uses gloves or fingere cots during handling.  One could argue that after shipment, since the PWAs are not conformal coated, you can introduce contamination in the field and therefore, why not not clean prior to shipment.

We may be performing board testing (boundry scan, bed-of-nails, etc) on PWAs that have been soldered using no-clean flux.  I understand that certain noclean flux can impede this testing, and also, may cause problems in event we need to conformal coat the PWAs.

Any comments on this subject will be appreciated.