Hi Steve
We're both slightly nervous.  I got my first intrusive reflow stencil in
today.  Can't wait to try it.  Like your experience the uncontrolled tests
were very encouraging.  Try www.itm-smt.com and go to articles.  I can't
really comment on your choice of aperture size without knowing the lead area
filling the hole and thus the solder volume required.  The referenced
article has a suggested formula.  Also try the Bob Willis web site.  Good
luck
John Thorup

> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: Thursday, November 11, 1999 11:52 AM
> To:   [log in to unmask]
> Subject:      [TN] Intrusive Reflow
>
> Hi ya'll!
>
> I'm getting ready to do some intrusive reflow on this board we got
> here...(this is my first time! I'm s-o-o-o nervous...not really...well,
> maybe
> a little...hehehe) Anyways,
> the parts are going to be 2, 20-pin SIP sockets. The board is .063" thick,
> the holes
> are spaced .100" apart, and the hole diameter is .040". I'm trying to
> decide
> how big I should make my apertures.
>
> I've looked at all the archive postings (there are a 168 of them on
> intrusive
> reflow) to see if anybody posted any recommended stencil thicknesses,
> and/or
> aperture sizes,
> but there was none. I looked on the web, but couldn't find any real
> guidelines either...
> (hmmmm, something I couldn't find...now THAT's a change!)
>
> I need to keep my stencil thickness at 6-mils, 'cause I've got some 20-mil
> pitch stuff on the same side. I was thinking of doing .060-.070" diameter
> circles over the holes...
> does that sound okie-dokie?
>
> I did a little test with the SIP socket and a syringe full of solder
> paste. I
> drew a bead of paste (about .030" dia.) down the row of holes and dropped
> the
> connector in, then reflowed it. Then I got my dremel tool out and did me a
> rough cross section to check the barrel fill. It actually wasn't too
> bad...there were about 2-3 holes that were a little shy volume-wise but
> that
> was because (I think) the solder wicked over to the holes next to it
> because
> of the continuous bead of paste I had laid down. That shoudn't happen when
> I
> have individual deposits of paste for each hole.
>
> So how big should I make my openings? Did I guess right at .060-.070"?
>
> -Steve Gregory-
>
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