Wow,
Thanks to everyone for all the info.
I have a new update. We tried 4 things based on a number of
recommendations:
1. Applied flux and hit the area with an iron. The discoloration went
away. But, we have such a large area on so many boards there is no real
way to get this done in a timely fashion. In addition, we scratched the
area up pretty well, so, either way, it looks bad.
2. We tried to re-wave the board. The discoloration got whiter/hazier
3. Used Methyl Chloroform to test for permanency. No mask was evident
on the swab which tells me the mask is cured.
4. Lastly, we baked a board at 250F for 45 minutes -- no change.
So...Any ideas what it is or if it is detrimental?
Any suggestions?
It's Friday...If anyone can suggest the boards are OK and I can feel
comfortable to ship that would be fine by me.
-Carrie
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gregg Klawson
Sent: Friday, April 23, 2004 11:50 AM
To: [log in to unmask]
Subject: Re: [TN] White Discoloration -- Excessive Heat, Insufficiently
Cured SM, or, Both?
Carrie,
Some info from one SM mfr, this may help.
http://www.enthone.com/electronics/pdf/Imup5.pdf
-- Gregg
At 02:27 PM 4/22/2004, Morse, Carrie wrote:
>Here's the status. I baked the boards for 45min @ 250F and...I still
>have the white haze. No change. So, What do you all think?
>(IOW--HELP!!!!)
>
>-Carrie
>
>-----Original Message-----
>From: Brian Ellis [mailto:[log in to unmask]]
>Sent: Thursday, April 22, 2004 2:06 AM
>To: TechNet E-Mail Forum.; Morse, Carrie
>Subject: Re: [TN] White Discoloration -- Excessive Heat, Insufficiently
>Cured SM, or, Both?
>
>I'm not saying that this is the cause, but another possibility is
>hydrolysis of the uncured solder mask. If the boards are coated and
>then stored in a humid atmosphere before development (either before or
>after
>exposure) for more than an hour or two, then some components in the
>chemistry may absorb sufficient humidity to hydrolyse, partially
>upsetting the polymerisation.
>
>I suggest methylene chloride would be better than acetone for a wipe
>test, but it depends on the chemistry of the LPI.
>
>Brian
>
>Morse, Carrie wrote:
> > 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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