Hi Carrie,
If it is gloss soldermask & you do not see any whitish haze prior to your
wavesolder process & happens only after that - then did you try baking the
boards at 140C for 2 hrs prior to your reflow & wavesolder process. But if
the boards have legend & they have gone through a UV bump at the Fab vendors
process then the white residue is locked in & nothing can be done to remove
it & it becomes worse after the thermal contact during the wave-solder
process.
But this is only cosmetic & does not pose any reliability issue, the only
way is to either accept it "as is" , scrap it or conformal coat after the
wave-solder process to cover the white haze.
The above may not be good to hear, but that is what it is.
Thanks,
Krishnan
-----Original Message-----
From: Morse, Carrie [mailto:[log in to unmask]]
Sent: Thursday, April 22, 2004 10:13 PM
To: Chezhian, Krishnan; TechNet E-Mail Forum.
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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