Hi Ed'

I remember Werner quoting some not named classics of satellite assy's,
with half of life "tested" out of them ! By "experts" !
If you'd specify which regime of which standard (No', please)you followed,
that would assist in analysis .
1
YES !
2
yes and no, depends, sometimes full pass indicates wrong application .
If all passes ; you have no idea where the limit is ;
if all fails (my condolences, know how yo feel);
likelihood of hitting it with oversized hammer (specifying wrong >shock<
test!)
is very high indeed (hope it ain't yo' mate).

While i would not believe cycling (likes IPC-SM-785) would fail you this
broad this fast,
following some shock standard could do it easy .

So, the specs of cycles/stress/shock/rises/durations/whatever, please ;
'm sure Werner would pull precedent from his extensive legal files instantly
than .
If obvious ; few of us could know

paul

-----Original Message-----
From: Ed Cosper [mailto:[log in to unmask]]
Sent: Saturday, 1 April 2000 8:31
To: [log in to unmask]
Subject: [TN] Thermal stressing


Hi all,

 I need some feedback. Here is the situation.

We had some concerns about marginal interconnects on some 10 layer boards
that had passed the bare printed circuit board bed of nails test at 100
volts. To instill more confidence in the products, the bare printed circuit
boards were submitted for environmental chamber thermal stressing (the 3
cycle test as outlined by IPC). Parts were stressed by an outside lab,
returned, assembled, in circuit tested, burned in, then final tested.

A sample of the parts that passed the final assembly test was sent out again
for the environmental chamber stress test.  The parts were then retested and
all the parts failed test. ( We have not determined why yet.)

Based on this I have two questions.

1) Is it possible to overstress loaded board?
2) Would you expect assembled boards to pass after chamber thermal cycling?
( I don't know if thermal cycling is appropriate for assembled products )

All thoughts are appreciated.

Ed Cosper
ABC

##############################################################
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
##############################################################

##############################################################
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
##############################################################