Hi Steve! It still amazes me that we are a industry dominated by surface mount
technology but we tend to think in wave soldering terms! One option you might
try is to use your reflow ovens for tinning - stencil print the component
footprint on a nonwettable substrate (e.g. ptfe or stainless steel), use your
placement options (manually or automatically) to place the parts on the
solderpaste deposit, and then run them thru the oven. This works quite well but
can be problematic in the placement step. And if you don't want to make a
stencil, you can hand apply the solder paste on the leads manually. Good Luck.

Dave Hillman
Rockwell Collins
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"Stephen R. Gregory" <[log in to unmask]> on 09/28/99 06:34:38 PM

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Subject:  [TN] Pre-Tinning Fine Pitch...



Hi ya'll!

Boy, I may have quite a task ahead of me. There's this assembly that has hit
the floor that has just about every part (CQFP's and ceramic SOIC's) in the
un-formed state, and we've got to form and trim, then Pre-tin the gold plated
stuff. I've already got a call into Six Sigma to get a quote on doing this
stuff for me, but it may turn-out that we won't have the time to deal with
this build and sub-contracting the forming and trimming, and pre-tinning out
(what's new?).

But in case I have to pre-tin the CQFP's myself, are there any tips that
anyone can share to help me get through this as painlessly as possible? These
parts are 320-pin 25-mil pitch and still have the tie-bars attached. I've got
a bottle of nitrogen and plan to "Rube-Goldberg" me an enclosure to blanket
the pot with nitrogen over the tinning pot that I'll be using...I think
that'll help to cut down on the bridging I'll see. I'm going to use an RMA
flux as well...any other suggestions? PLEASE?

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