Not bad idea if the extra heat cycle is (should be) tolerable, Dave .
Maybe Steve also could dip them in paste sheet ; flip upside(legs up)down on
pallet (keeping cooler as well);
in theory all the paste should wick evenly in reflow (dispensing indium
does).
Practically I prefer miniwave still ; with vacuum pick up handling it's
clean and easy.
Also the flux dip is reassuring with sus finish .
Still again , the reflow would give more even result ; have to try this one
; you may have a point

paul

-----Original Message-----
From: David Hillman [mailto:[log in to unmask]]
Sent: Wednesday, 29 September 1999 23:17
To: [log in to unmask]
Subject: Re: [TN] Pre-Tinning Fine Pitch...


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
[log in to unmask]




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

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
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To:   [log in to unmask]
cc:

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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