And don't forget that incoming components, including the printed circuit
boards, may be delivered neatly contaminated. If you want hi-rel with
"no-clean" chemistry, all you may be doing is, instead of having one
cleaning operation, you may have displaced it to each of your suppliers.
Furthermore, you need to do much more process control and in-house
qualification testing. Be careful that it does not cost more, in the
long run, than using an easily cleaned chemistry and good cleaning, with
easier soldering as a side-benefit.

Brian

> Bogert wrote:
>
> 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.

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