Our company does lead tinning on military ceramic and military plastic
components.  The plastic packages need to be baked out as you are doing but
you should also verify that the component temperature reaches 100 C in
preheat prior to being dunked in 250 C solder.  As long as these are
conventional plastic components (no embedded heat sinks etc.) you should be
fine.  To verify you should use acoustic microscopy to check for
delamination inside the package.  There are several vendors who can do this
for you.  One of them is Sonoscan in San Jose, CA.

Ball grid arrays are another story.  We have found that reflow temperatures
above 220 C should be avoided and multiple reflows are generally safe near
200 C.  Most package manufacturers aren't ready to promise much here.

Russ Winslow
Six Sigma / Winslow Automation, Inc.
San Jose, CA
[log in to unmask]

-----Original Message-----
From: Stuart Korringa <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, July 24, 1998 5:44 AM
Subject: [TN] Assembly process for plastic parts


>        My company is historically involved in military programs but in the
>     last 5 or so years we have made a change to many more commercial
>     product lines. We are using more plastic parts both for commercial and
>     military customers as I suspect many other companies are also doing.
>
>        The question from Components Reliability Engineering is about the
>     practice of using chipbonder to attach surface mount plastic parts to
>     a through hole PWB which is then inverted and sent through wave solder
>     thereby soldering the through hole and SM components simultaneously.
>     The plastic parts have been baked but CRE is concerned about latent
>     damage to the dunked plastic parts. There is no damage to the external
>     package but what about the inside?
>
>        Any insight to the inside of a component and reliability from
>     TechNet is appreciated.
>
>     Stu Korringa
>     Smiths Industries
>     Grand Rapids, Michigan
>
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