They varied from 3100 to 3800 V/mil.
Andy Magee
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Subject: Re: FW: Re[2]: Humidity Testing
Author: Doug McKean::(MCKENDAB) at ~FABRIK
Date: 7/12/96 5:05 AM
From: Doug McKean
Date: Fri, Jul 12, 1996 5:05 AM
Subject: Re: FW: Re[2]: Humidity Testing
To: "'IPC - Technet Input'"
Andy,
Just curious - What is the volt-per-mil rating of the material
in between the traces supposed to be?
Doug
Dill, Norm J wrote:
>
> Andy,
> Considering your test was run at 100 v with a .006" spacing,
is there
> any chance that airborne contaminants contributed to your 300/500
hour
> failures?
>
> Norm Dill
> [log in to unmask]
> ------------------------
> Subject: Re[2]: Humidity Testing
> Date: Wednesday, July 10, 1996 4:18PM
>
> We've done some testing on flex circuits and found that
> there was about a 300 hour incubation period before visible
> defects were evident on the failing circuits. Actual
> electrical failures (shorting) took up to 500 hours. The
> insulation resistance falls off early in the test as the
> moisture reaches equilibrium in the polyimide, and then
> falls further at about the time of the incubation period.
>
> The continuous bias voltage was 100V. 85C, 85%RH 100 mA
> current limited, 0.006" spaces between traces. Measurements
> were taken at 24, 48, 72, 144, 200, 300, 400, 500, 550 and
> 1500 hours.
>
> Andy Magee - Applications Engineer
> Rogers Corp - Circuit Materials Unit
> Tel: (602) 917-5237
> Fax: (602) 917-5256
> E-Mail: [log in to unmask]
>
> ______________________________ Reply Separator
> _________________________________
>
> Subject: Re: Humidity Testing
> Author: SIRGuru::(SIRGUR) at ~FABRIK
> Date: 7/10/96 1:12 PM
>
> From: [log in to unmask]
> Date: Wed, Jul 10, 1996 1:12 PM
> Subject: Re: Humidity Testing
> To: TechNet
> I'll give you my favorite engineering answer - It depends.
>
> If you are trying to determine if a fabrication or assembly process
> is
> Bellcore-compliant, the answer is no. Bellcore compliancy is only
> obtained
> through the SIR and Electromigration testing in Chapter 13 of
TR-78.
>
> If you are trying to determine if a vendor has acceptable product,
> and you
> don't really care about Bellcore compliance, then I would say the
> answer is
> yes. The seven day SIR test, IPC-TM-650, method 2.6.3.3 rev A, is
an
> alternative.
>
> The Bellcore electromigration test is 85C/85% RH, so is the SIR
> method.
> The Bellcore test goes 96 hours before the first measurement in an
> unbiased
> state, then a bias of 10 volts is applied.
> The SIR test is biased from the start with a 50 volt bias.
> The Bellcore test is not tied to an absolute resistance value.
> The SIR test has a minimum of 100 megohms.
>
> I'm not really trying to bash the Bellcore electromigration test,
but
> I
> understand the time constraint. In my opinion (that and 50 cents
> gets you a
> Diet Coke), you are best to do both methods concurrently. The SIR
> test should
> be able to allow you to make the decision in 7 days vs. 25 days.
> Alternatively, you could interrupt the electromigration test after
> 7-10 days
> and see if you have any signs of corrosion or metal migration. It
> has been
> my experience that if you have not seen electromigration and
> corrosion after
> 7 days at 85/85 and a 50 volt bias, you would not see it in 500
> hours.
> Again, my opinion.
>
> Hope this was helpful. If you want to discuss it in greater depth,
> give me a
> call at (317) 457-8095.
>
> Doug Pauls
> CSL, Inc.
> [log in to unmask]
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