TECHNET Archives

April 2000

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
Date:
Mon, 3 Apr 2000 21:48:05 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (89 lines)
ED,
An electrical test like bare board bed of nail test is OK but not a
guarantee that board will pass mechanical reliability of interconnect.

For example, take a 6 mil wide line,  cut a V notch in it so that there is
only 2 mil copper left. This will pass almost all electrical stress test but
is it mechanically reliable interconnect? Answer is NO.

At my previous employer, reliability was tested at following levels:
Raw board
Components
Test Board at Assembly level with typical solder joints
Product Level Assembled board

So to your questions, yes an assembled board will stand upto the thermal
stress. Check the specification of components carefully, though, so that you
do not exceed the limit of tolerance for the most sensitive component on
your assembly.

I have seen -45 deg.C - 65 deg.C test done on assembly and then pass ICT
test as part of shipping qualification. Hope this helps.

----- Original Message -----
From: "Ed Cosper" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, March 31, 2000 3:31 PM
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
##############################################################

ATOM RSS1 RSS2