I agree with Doug.
If its going to fail due to corrosion etc. you are going to know it quickly.
In a previous life working for a Telecom equipment maker we would do the 500
hour test, but by looking at the readings and taking a quick peek at the
sample after a week you could tell if you were going to pass or not.
If the issue is time, and you do need to verify to Bellcore compliance you
might want to consider taking a look after 7-10 days and giving a
"conditional" approval pending the test running out its full course.
Just my two cents. I have no doubt that some of the Bellcore and ex-Bellcore
gang
out there probably is going to be rebutting this soon....
A
Andy Heidelberg
Micron Custom Manufacturing Services
[log in to unmask]
----------
From: TechNet-request
To: TechNet
Subject: Re: Humidity Testing
Date: Wednesday,July 10,1996 5:12PM
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.
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