We have manufactured thousands of boards with a mix of both ceramic and
plastic parts, mainly for military communications equipment. We use RMA
paste and an aqueous wash. We now place a much greater percentage of
plastic parts of course, because that is where the technology has migrated.
I have not yet had to deal with the issue of entrapped corrosive residues
in any of our product.

I don't buy the Rosin-bad, low residue-good argument. There are a lot of
good reasons to go with a low-residue process, but to just out of hand say
an RMA process is bad is not one of them IMO.

At 11:35 AM 12/16/98 -0800, you wrote:
>Season's Greets,
>
>A query (actually re-query) to those in the know on the usage of plastic
>microcircuits instead of ceramics.
>
>I have some component guys who have ruled that plastic parts can only be
>assembled on a no-clean flux line.  Anyone using a rosin (RMA) flux is
>dis-qualified from assembling for us.  I know the theory is that the
>microcracks formed at reflow temperatures will entrap corrosive residues,
>but I have trouble buying the NO-CLEAN GOOD, ROSIN-BAD generalization.
>
>Opinions?
>
>Ralph Vaughan
>Boeing-Atlanta
>
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----

Jeffrey C. Guynn <[log in to unmask]> Phone: (219) 429-6345
Lead SMD Manufacturing Engineer        Fax: (219) 429-4688
Raytheon Systems Company M/S 25-31
1010 Production Road, Fort Wayne, IN 46808-4106

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