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December 2007

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Subject:
From:
Charlie Pitarys <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Charlie Pitarys <[log in to unmask]>
Date:
Tue, 11 Dec 2007 14:18:31 -0600
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I know this has been brought up several times. Searched the archives but 
more help will be appreciated.
Full process:

Before Reflow PCB have Temperature storage at 65°C for a minimun of 24H 
(some time few weeks)

After Refow before wave solder the PCB have Temperature storage at 70°C 
for 8 hours (the night)

After Wave solder (Pacific 9000M flux) 100% of production is cleaned. Current 
wash temp. was set at 70C. Yes I know this is extreme and advised to 
lower<60C. This helped a little.
If a sample section PCB is protected with Kapton and Kapton removed before 
cleaning No Problem appears on that solder mask area.

You can even see an outline where the wave solder fingers caused shadowing 
of the solder mask and on the top side along the edge where some flux has 
wicked over.

I need to direct my customer to documents, etc. that have substance on this 
issue. He is hesitant to receive my advise and reasons that I know for this 
occurance. Bad solder mask.
The problem of white mark is only on few case (less than 5% of PCB).

The PCB I saw was subjected, before any process a Temperature storage of 
65°C during 3 weeks (can this make the PCB more sensitive ?)
My flux analysis shows the spectrum has all the signature features for a 
carboxylic acid and a library search brought up adipic acid as the closest 
match.
Thanks in advance

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