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May 2008

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Subject:
From:
Leland Woodall <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leland Woodall <[log in to unmask]>
Date:
Tue, 13 May 2008 14:28:27 -0400
Content-Type:
text/plain
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text/plain (238 lines)
Jerry,

Our boards see no cleaning cycle.  We have, though, looked at our
filters on our stencil and wave solder pallet cleaning machines, as well
as those at our conformal coating process.

No matches were found in any of the above.  Either the material was
completely different, or else much larger in diameter than what we're
seeing.

Thanks again,

Leland

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jerry Dengler
Sent: Tuesday, May 13, 2008 2:14 PM
To: [log in to unmask]
Subject: Re: [TN] Stainless Steel Contamination Question

Leland,

Do you wash these boards prior to finding the strand?  If so does the
cleaner use a stainless steel wire mesh filter?  Just another long shot.

Jerry 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Tuesday, May 13, 2008 1:58 PM
To: [log in to unmask]
Subject: Re: [TN] Stainless Steel Contamination Question

It is probably  a magnetic grade of stainless if it is clinging to the
leads, can you confirm this?

 
 
John Burke
 
(408) 515 4992

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, May 13, 2008 8:06 AM
To: [log in to unmask]
Subject: Re: [TN] Stainless Steel Contamination Question

David,

We haven't seen any of this interfering with or preventing a solder
joint from forming.  In every instance, it's clinging to the leads.

Wouldn't that pretty much rule out our reflow ovens?

The earliest part of our process where this has been found is at
in-circuit test after the wave solder operation.

That leaves our Omron AOIs, our Huntron visioning stations, and our
flying probe machines.  We've looked in and all around those processes,
and still are coming up with nothing.

Like trying to find a (stainless steel) needle in a haystack...

Leland

-----Original Message-----
From: David Greig [mailto:[log in to unmask]]
Sent: Tuesday, May 13, 2008 10:57 AM
To: Leland Woodall
Subject: RE: [TN] Stainless Steel Contamination Question

Are the fibres causing any problems with solder joint formation, if so
then trace backwards from the oven. If not then look around the oven and
forwards to the point at which they are observed.
What about the air/nitrogen source into the oven? Any bit of kit that is
opened and closed regularly.

The gaskets are used likely on electronic or even electrics enclosures,
particularly clam shell cases. The cut ends of the gaskets typically do
fray out loose fibres.


Best Regards
 
David Greig

-----Original Message-----
From: Leland Woodall [mailto:[log in to unmask]]
Sent: 13 May 2008 15:29
To: David Greig
Subject: RE: [TN] Stainless Steel Contamination Question

David,

Where in my manufacturing process might I find one of the knitted EMC
gaskets?  Are you familiar with any particular machinery that would use
these?

Thanks again,

Leland

-----Original Message-----
From: David Greig [mailto:[log in to unmask]]
Sent: Tuesday, May 13, 2008 10:26 AM
To: 'TechNet E-Mail Forum'; Leland Woodall
Subject: RE: [TN] Stainless Steel Contamination Question

Perhaps an EMC gasket. One of the knitted mesh materials commonly used
consists of knitted stainless steel fabric. There may well be residues
of silicones and other lubricates used in the knitting or weaving.


Best Regards
 
David Greig

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: 13 May 2008 14:47
To: [log in to unmask]
Subject: [TN] Stainless Steel Contamination Question
Importance: High

Hi Everyone,

 

We've had a problem lately with fine strands of stainless steel wire
being found on top of some of our .5 mm pitch ICs.  This has caused both
internal and external issues, and we've yet to identify the source.

 

It's definitely formed wire, with a thickness ranging from 7 to 10
microns, and up to 3 mm in length.  

 

Our automated optical inspection stations can only reliably detect
widths of 12 to 15 microns.

 

I've checked the internet in an attempt to find common applications of
this wire.  I've found two, and they were for ultra-fine filters and
stencil screen mesh.  We've investigated (I think) all of our machinery
that would utilize filters this small and have found no such usage.
I've also checked every stencil in our plant, and all of our mesh
material is some type of a plastic compound.

 

Do you have any idea where this stainless steel might be coming from?

 

Any suggestions would be sincerely appreciated!

 

Thanks,

 

Leland


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