Yes, dry inert atmosphere would be a poor test for flux residue problems.

Maybe we were doing something wrong but I remember HALT/HASS testing under
ambient/air conditions with LN2 going through a heat exchanger for thermal
shock.  Testing for an office environment so we did not add extreme humidity
or salt spray but those could also be accelerating factors.  One false
result we did see was from flux residue.  The beta prototype used for a test
vehicle had rework where someone in engineering used an RA solder flux.
Failed quickly as you may expect but not really valuable information as that
material was not available in the production environment.  Best to test
product 'off the line', but that makes it kind of hard to get a design
change before production starts.

Brad Vanderhoof
AITI




----- Original Message -----
From: "Tegehall Per-Erik" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, March 20, 2003 11:34 PM
Subject: Re: [TN] Flux Contamination Testing


I don't think HALT/HASS testing would be useful in this case since that type
of testing is performed in dry nitrogen atmosphere. In dry conditions, it is
not likely that the flux residues will affect the resistance.

Per-Erik Tegehall
IVF

-----Ursprungligt meddelande-----
Från: BRAD VANDERHOOF [mailto:[log in to unmask]]
Skickat: den 21 mars 2003 08:06
Till: [log in to unmask]
Ämne: Re: [TN] Flux Contamination Testing


I think a good test would be HALT/HASS (Highly Accelerated Life Test/Highly
Accelerated Stress Screening).  This will push assemblies to failure and
tell you if possible flux residues are a major weak point in the product.
Difficult and cryptic to interpret but faster than traditional life testing.

Brad Vanderhoof
AITI


----- Original Message -----
From: "Bloomquist, Ken" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, March 20, 2003 1:42 PM
Subject: [TN] Flux Contamination Testing


> I have a question regarding a test for flux contamination on conformally
> coated boards.
>
> I know all about testing uncoated boards but was wondering if there are
any
> tests for type UR coated boards?
>
> Does a temperature soak do any good at bringing problems to the surface?
>
> Does baking cause any remaining flux to become conductive?
>
> Does a humidity/temperature soak do any good?
>
> What were looking for is a parallel electrical path that might reduce the
> value of a small SMT resistor.
>
> Thanks in advance,
>
> KennyB
>
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