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June 2004

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Subject:
From:
"Kasprzak, Bill (sys) USX" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 23 Jun 2004 08:33:15 -0400
Content-Type:
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Steve,

I've recently used an adapter socket similar to the one that you're using
for the same reason. (Can't get the DIP package anymore.) The socket that we
used came from Emulation Technology. The problem that we ran into was that
we wanted to "tin" the gold plated pins on the bottom of the adapter prior
to board insertion. Even though the specs from  EmTech stated that the
solder joints that hold the pins on the bottom of the board used high
temperature solder, all the pins fell off when attempting to tin the part in
a 500F solder pot. So tinning was out of the question.

My original thoughts when looking at your solder balls was that it was
moisture related but since it is confined to the adapter socket only, that
can't be it.

My two cents worth would be to see if you get a reaction if you try to "tin"
the socket. Maybe there's some kind of coating on the pins or perhaps you
are reflowing the solder that holds the pins to the adapter socket that's
causing the solder balls. If you can tin the socket, then install it after
tinning and see if you get the same results.

Good luck. Keep us posted if you can.

Bill Kasprzak
Moog Inc., Systems Group, Process Engineer


-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, June 22, 2004 4:37 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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