Pat,
If the "contaminants" are on the surface, they should be easily rinsed off
with IPA prior to inspection. We often do this to prevent needless
inspection rejections. Besides, I don't believe surface contamination is a
legitimate rejection criteria for the coating material - maybe for the
assembly, but not of the coating itself. If, on the other hand the
contamination is within the coating, check the cleanliness of the bulk
material. We filter a lot of our coating material first, before mixing.
-----Original Message-----
From: Pat Lujan [mailto:[log in to unmask]]
Sent: Thursday, August 12, 1999 6:06 PM
To: [log in to unmask]
Subject: Re: [TN] Uralane 5750
Hans and Technetters,
Definitely not performing this in a clean room; however we have hepa
filtration. We have recently aquired a laminar air flow work station where
I have been air curing the boards prior to an oven cure. I have even gone
through the additional expense of purchasing new ovens with modifications to
filter the incoming air into the oven.
Another form of contamination which I forgot to mention in my previous
e-mail is a snowflake, dandruff looking type of crystallization. After
talking to vendor (Ciba Specialtly Chemicals) I am suspecting that this is
coming from moisture. Part A of Uralane 5750 is hygroscopic and this may
be the source.
Thanks for any comments in advance.
Pat
>>> Hinners Hans CIV WRALC/LYPME <[log in to unmask]> 08/12 3:20 PM
>>>
Hey Pat,
I don't know Uralane but are you doing this in a Cleanroom
environment?
If so what Class and flow type?
Have you tried letting the boards cure in a cleanhood or something?
Hans
Air Force Material Command - We keep them flying!
~~~~~~~~
Hans M. Hinners WR-ALC/LYPME Bldg. 640
Materials Engineer 380 Second Street,
Suite 104
Manufacturing Eng. Sec. Robins AFB GA 31098-1638
912-926-1970 (Voice) 468 - 1970 (DSN) 912-926-7974 (Fax)
[log in to unmask]
> I need help with a problem I have been fighting for 6 months. We
> currently use Uralane 5750 on hi-rel PWA's used in space applications.
> Our method of applying is the brush method per NHB5300.4(3J) April 85.
>
> The quality requirements state that "Coating shall be free from
> contamination or foreign material. Any contaminant visible under 4- to
> 10- power magnification shall be cause for rejection."
>
> My problem seems to be the properties of Uralane 5750. It seems to remain
> tacky after it is cured and this appears to attract all airborne
> particles. Our CSI and GSI inspectors naturally crank up the scopes to
> 10 power. I used Humiseal 1B31 in the same environment and do not have
> the same problems.
>
> My main customers Boeing and TRW have both issued CAR's against this
> process as it realates to contamination. I am in need of any input that
> may help me improve my process. I am a NASA certified Instructor in
> Conformal Coating and Staking and have not been able to solve this
> problem.
>
> Any information that would aid me in continuing my career would be greatly
> appreciated.
>
> Pat Lujan
> Senior Mfg. Eng.
> BFGoodrich Data Systems Div.
> Albuquerque New Mexico USA
> 505.938.5373
>
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