Bev,
I wasn't a member of 9701 during those discussions either but my experience says I agree with Werner's asertion that event detectors are better than data loggers at determining when an event occurred. However, I'm going to side with your comments. Data loggers are easier to come by and less expensive and aren't as finicy as event detectors. The kinds of problems I've seen during reliability testing aren't due to poor detection of events but understanding exactely what failure generated the event. I'm sure you would agree that you can't ( or at least shouldn't) run a reliability evaluation, with data loggers or event detectors, without doing FMA. I've seen too many cases during my previous employement and with the current Pb-Free testing to know that it's sometimes more import to know what failed. I'm currently evaluating temperature cycling failures on Pb-Free test vehicles that were subjected to 6000 cycles of 0C to 100C. The event detectors indicated that approximately 25 to 30% of the peripherical leaded packages on the test boards failed. Manual resistance measurements after the 6000 cycles confirmed the detected events. However, FMA has shown that the peripherial leaded package Pb-Free solder joints were not the reason for the failures. In one case the events detected were cracks in through-vias used in the daisy chain and in the second case the events detected were cracks in outer-layer daisy chain traces.
Regards,
George
George M. Wenger
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bev Christian
Sent: Friday, May 06, 2005 8:05 AM
To: [log in to unmask]
Subject: Re: [TN] IPC 9701 Failure Definition
Werner,
I was not a member of the committee during those discussions. However,
if a company has a library of completed testing using the data loggers
and they that a product tested to X number of cycles which they know by
experience will be equivalent to more than the life of their expected
product, shouldn't that be good enough? Or better yet, they have run
experiments with both data loggers and event detectors and have
correlated the results?
Probably the main reasons people use data loggers over event detectors
are:
1) data loggers are easy to come by - more people sell them
2) event detectors are SO finicky when it comes to glitches . You
practically have to ground your grandmother three countries away to not
have spurious signals.
Regards,
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: May 5, 2005 11:50 PM
To: [log in to unmask]
Subject: Re: [TN] IPC 9701 Failure Definition
Hi,
Yes youn are correct. HOWEVER, I have a real problem with the use of
data loggers for finding solder joint reliability. They have been shown
to miss failures for many thousands of cycles after the fracture
actually occurred. I strongly advise against the use of data loggers [
they arew o.k. for bare board testing] for solder joint reliability
testing. Their inclusion in IPC-9701 was against my advice and against
all my experience.
Werner Engelmaier
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