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December 2005

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Subject:
From:
"Barmuta, Mike" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Barmuta, Mike
Date:
Wed, 14 Dec 2005 13:42:07 -0800
Content-Type:
text/plain
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text/plain (121 lines)
Hi Steve: When you're talking about a "chem-film conversion coating" on
aluminum I'm assuming you are referring to a chromate conversion
coating. Let me know if that's not the case.

Although they are normally meant to be, chromate conversion coatings are
not necessarily permanent, they can be chemically stripped. Stripping
can be done using either a strong caustic(base) or acidic chemical
formulation.

So it is possible for the cleaner+heat to cause this effect. I doubt the
RMA flux would be aggressive enough.

The first thing that comes to my mind is..... Is this a RoHS compliant
part? Perhaps they are using a non-hexavalent chromate coating that will
not stand-up to the cleaning cycle as the traditional hexavalent coating
would.

                                                                Regards

	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett WA
	
425-446-6076



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stephen Gregory
Sent: Wednesday, December 14, 2005 12:59 PM
To: [log in to unmask]
Subject: [TN] Really Terrible Looking Chem Film...


Hi All!

We have a series of boards that we build here, that we've been building
for years and years. 

These boards use a 320-pin right-angle male connector that has an
aluminum chem-filmed body.

After building the last batch of boards, we have 5-assemblies that have
the worst looking chem-film coating on the connectors I have ever seen.
Check out:

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

I'm not a chem-film guru by any means, but I have a hard time believing
that anything in my process caused this appearance. Chem-film conversion
coatings are permanent aren't they? I mean the only way to remove them
is mechanically, or etch them, right?

These boards were wave soldered with a RMA flux and cleaned in Kyzen
Aquanox 4512P.

Anybody seen this before and know what might cause this?


Stephen Gregory
Senior Process Engineer
LaBarge Incorporated      
Tulsa, OK 74146
(918) 459-2285
(918) 459-2350 FAX
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