Carrie: One more thing to look for.
Look carefully, sometimes it is hard to detect, at the bottom fluxed side of
the board. Is the white discoloration only on the mask or is it also in the
surrounding open non-masked areas of the board?
If it's just the mask then you have probably have a soldermask issue. If
it's also on the laminate then you probably have a fluxing/preheat issue.
Also since you are using an OA flux I'm assuming your are seeing this after
wash. You may want to take a board after wavesolder and wash with cool water
and dry thoroughly. See if you have the same condition. Sometimes
saponifiers, high wash/rinse temps and long exposure times can aggravate the
condition depending on what the initial problem is.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Morse, Carrie
Sent: Thursday, April 22, 2004 7:13 AM
To: [log in to unmask]
Subject: Re: [TN] White Discoloration -- Excessive Heat, Insufficiently
Cured SM, or, Both?
Actually, it's a gloss LPI. I wish it were matte -- then we wouldn't
have solder balls!
-----Original Message-----
From: Chezhian, Krishnan [mailto:[log in to unmask]]
Sent: Wednesday, April 21, 2004 8:07 PM
To: 'TechNet E-Mail Forum.'; Morse, Carrie
Subject: RE: [TN] White Discoloration -- Excessive Heat, Insufficiently
Cured SM, or, Both?
Hi Carrie,
What type of soldermask & the vendor is used on the board. I presume it
is a matte soldermask, if that is the case you need to look at the wave
solder temperature. The reason being, solid additives are used as
matting agents or thermal cross linkers & the white haze can be avoided
with proper temperature control. If still cannot resolve get the fab
vendor to change to gloss soldermask if solder balls is not an issue in
your process. Hope this helps.
Krishnan
SANMINA-SCI
Quality Assurance / NPI Manager
E-mail: [log in to unmask] Phone (Off): 082-363000 Ext.
1602
Mobile: 012-8888-379
-----Original Message-----
From: Morse, Carrie [mailto:[log in to unmask]]
Sent: Thursday, April 22, 2004 2:36 AM
To: [log in to unmask]
Subject: [TN] White Discoloration -- Excessive Heat, Insufficiently
Cured SM, or, Both?
We are wave soldering a LPI board and seeing a Whitish Discoloration --
Haze like -- only in the areas that the board has seen OA flux and wave.
We are using a wave pallet and the areas not exposed do not exhibit this
phenomena. This board is also processed through SMT for one side and we
do not see this around any of the SMT.
We have not seen this problem in the past, and, the Wave operator states
that the wave recipe has not changed.
So, I am wondering -- if LPI is not fully cured, will it turn white when
exposed to OA flux and Wave?
Also, what IS the max temp LPI should be able to see and for how long
without discoloring?
We've done an Acetone test, but, it comes up clean and....I think I read
in a previous posting that the Acetone may not be an effective test for
LPI. Is that true? If so, What IS an effective test?
I'm headed to the Omega tester to see "how clean" the board is.
All advice is welcome!
-Carrie
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