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April 2004

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Subject:
From:
"Chezhian, Krishnan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 22 Apr 2004 08:07:07 +0800
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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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