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June 2004

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Subject:
From:
"Crepeau, Phil" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 22 Jun 2004 17:05:56 -0700
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another factor might be the difference in the aries adapter lead cross section area compared with the 'former' dip lead cross section area. a 'significant' difference here would be worth looking into.

having said all this, though, i suspect your idea is closer to the root cause.  i just love to brain storm.

phil

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, June 22, 2004 1:37 PM
To: [log in to unmask]
Subject: [TN] Very Strange Solderballs...


Hi All!

Well, I'm just about at my wits end after fighting with something for the
past two days that for the life of me, I can't figure out.

Starting at the beginning, we've been building a mixed technology assembly
for well over two years now, that practically builds itself...it's that easy.
Has been running smoothly, and the boards don't have so much as a pimple on them
when we're done.

Recently, a 16-pin DIP IC has been very hard to get, so there was a change
made to use a 16-pin SOIC on an Aries SMT-to-PTH adapter...you can get the SMT
version of this part all over the place, and it's cheaper than the PTH version
even when buying the adapter along with the IC!

Didn't think there was going to be a shred of trouble with that change, but
boy was I wrong! And this problem has me completely baffled...

If you go and look at:

http://www.stevezeva.homestead.com/files/AdapterSolderballs.jpg

as well as:

http://www.stevezeva.homestead.com/files/AdapterSolderballs2.jpg

You'll see the solderballs that this whole story is about. They ONLY occur at
the locations where the Aries adapters are being used. Another weird thing is
that these solderballs won't wash away...even after multiple cleanings in
either an Electrovert H-500 inline cleaner, or a Aqueous Technologies SMT800
batch cleaner that uses Kyzen Aquanox 4512P chemistry...the only way to remove
these little buggers is mechanically by brushing them away. By the way, I'm using
Kesters 2331 water soluble flux in my Electrovert Electra, so it's even more
puzzling why the solderballs won't wash away. The flux is applied with an
OPTIFLUX-1 ultrasonic spray fluxer.

I want to try and figure out why I'm getting them in the first place. I've
been dinking with the wave profile for the last two days, changing everything
from one extreme to another. The solderballs either get worse, or stay the same.
I thought that maybe I wasn't drying out the flux well enough, but when I
either increased pre-heat, or slowed down my belt speed in an effort to do that,
the solderballs got worse.

Has ANYBODY ever experienced something like this before? I'm about to pull my
hair out!!

I have a theory about this that I think I'm going try an experiment to see if
I can prove how these solderballs may be occuring. If you look at this
picture:

http://www.stevezeva.homestead.com/files/Adapter.jpg

You can see that the leads on this adapter are machined pins. My theory is
that at the top of the pins, you see a sholder that might be effectively
"sealing" off the barrels slightly. That shoulder sits flush on the anullar ring. So
when the board passes across the wave, the barrel fills from the bottom up,
which is compressing the trapped air inside the barrel to a point at which the
barrel "burps" or "spits-up" (the Dads out there, all know about spitting up)
the solderballs.

I'm going to test my theory by putting some dissolvable spacers beneath the
adapter so that the shoulder won't be sitting flush on the pad, and see if I
still get the solderballs.

I sure would like to hear that somebody has seen this before, and found a way
to deal with it...

Thanks everyone!

-Steve Gregory-


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