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March 2006

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Subject:
From:
"Schaefer, Chris" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Schaefer, Chris
Date:
Mon, 6 Mar 2006 09:56:21 -0600
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Steve,

What are the other variables during the wash process? Such as the pressures in each wet module, etc... Also, is it possible to perform a pull test on the plastic part to determine the bond strength between the plastic cover and the SMT part? Does the manufacturer have recommended process parameters for the SMT process and cleaning process? If so, are you complying with these parameters? What chemistry concentration of the A4512 are you employing? The chemical may be adding to the problem (unlikely, but it may) - you may want to find out what the bonder is and contact Kyzen to see if the A4512 has issues with the bond material.

We use the Kyzen A4520 and have found that it has issues with some materials in which it causes the materials to discolor and things like that, but nothing like what you are seeing. We run at 125F wash, 150F rinse, 150F final rinse, and at 1.5FPM conveyor speed. Roughly 99.999% of the products we process have zero issues even at these temperatures.

Hope this helps...

Chris Schaefer
Suntron Corporation
Process Engineer
540 N. Rogers Road
Olathe, Kansas 66062
913.393.5878
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen Gregory
Sent: Monday, March 06, 2006 9:19 AM
To: [log in to unmask]
Subject: [TN] A new one for me, ESD Suppressors...


Mornin' Everybody!

Last Friday, I had a problem with a new part that I've never used
before, and maybe somebody else has seen this problem. It's with
something called an ESD Suppressor. It's a little 0603 SMT part that
looks a lot like a LED...in fact, that's what I thought it was at first.
It's made by Littlefuse.

My problem is that there's a little green piece of plastic on the top of
it that looks like it's held there with a tiny dot of glue, that is
either coming off or breaking during wash. I'm washing the boards in a
batch cleaner using Kyzen Aquanox 4512P at 140 F. for 20-minutes
followed by a ambient temperature rinse cycle, and a 15-minute 100 F.
dry cycle.

I did read in the datasheet that I'm probably washing at too high a
temperature. The datasheet says that they have been tested IAW ASTM-543
for 4-hours at 40 C., with 3 solutions (H2O, detergent solution, and a
defluxer). I didn't know that there was this limitation until we
observed the little green pieces of plastic coming off. You can see a
picture at: 

http://stevezeva.homestead.com/files/ESD_Suppressor.jpg

My question is; what is that little green plastic piece? There's nothing
in the datasheet that describes it. Is it something functional to the
part? Or is it something there for pick and place? I've got a call into
Littlefuse and I'm just waiting for a call back. But I thought I'd ask
you all to see if someone else has run across these little guys before.
I don't have a clue about them...

Have a good Monday!

-Steve Gregory-



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