It sounds as though Ken may be performing this test on a limited number
of boards to validate a possible process issue. I agree that shipping a
board that has been tested as he has suggested would not be wise. If Ken
set aside a specific number of boards, performed accelerated testing on
them, collected evaluation data, and then scrapped them he would be fine.
Barrie
HALT/HASS Engineering
-----Original Message-----
From: Brent Stayer [mailto:[log in to unmask]]
Sent: Thursday, June 22, 2000 2:06 PM
To: [log in to unmask]
Subject: Re: [TN] Thermal shock profile
Ken,
I sure hope I don't get one of those boards...........
Are you trying to make good product out of "suspected bad" with the thermal
shock testing? In my humble opinion, these boards should be scrapped. If
not, what will be your criteria for allowing these to be shipped? If I get
only one or two more failures? And if you get none, are you sure that this
test didn't accelerate other points of failure just to the edge and they
will fail in the field (infant mortality). Upon return from the
field/customer, these will most likely be attributed to "infant mortality"
when effect, they actually have an assignable cause.
I believe that if you do perform the test, the only things you may get is:
1. If they all pass, "A warm fuzzy feeling" that they are OK.
2. If you have a lot of fallout, relief that you didn't ship them. And I
might add, a lot of opinions that they only failed because you "over
stressed" them.
Play it safe, don't ship!!!!!!!!!!
Brent
Reliability Engineer
>>> [log in to unmask] 06/22/00 12:54PM >>>
We have found some internal fab defect (cracking at one of the inner layer)
which we don't know is due to assembly process or fab process induced.
If I were to create a Thermal shock profile to precipitate defect on a
loaded board How can I come out with? I have decided to use -10C to +70C, 10
minutes soaks, +/-20C/minute ramps, 12 cycles which will give a test
duration approx. 3.6 hours.
Any comments will be highly appreciated. All the failed one were found
during ICT testing hence decided to send all lot.
re,
Ken Patel
______________________________________________________
Ken Patel Phone: (408) 490-6804
1708 McCarthy Blvd. Fax: (408) 490-6859
Milpitas, CA 95035
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
|
