Subject: | |
From: | |
Date: | Thu, 27 Mar 1997 15:00:27 -0600 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
To all you tech types,
I imagine this question has been seen before, but here goes....
We are experiencing some problems with cracked solder joints on an
assembly.
The PWB is a Polyimide material, .070" thick with 12 layers. All layers
are 1oz copper. The PWB has a bonded stiffener, 6061-T6 aluminum @.040"
thick. Board dimensions are 6" x 3.875".
Some components are placed over the stiffener, some are not. The
assemblies are prepared with straight through lead termination and are wave
soldered, some post assembly performed, cleaned, and inspected. All the
assemblies exhibit good wetting and generally good solder characteristics
at this point. The assemblies are then sent to our test department where
they are subjected to 10 thermal cycles of -54 Deg. C to +95 Deg. C at a
rate of 15 Deg. C. per minute (customers request). The
assemblies are inspected and that is when the fractures appear.
The fractures all appear on gold plated, side brazed lead DIPs that are
sitting directly on the stiffener. The fractures occur mostly at the lead
fillet, but occasionally happen near the pad fillet Also worth noting is
that the fractures occur on the side of the leads (the thin portion of the
lead) with the more severe ones occurring near the ends of the DIPs and
lessening as you move toward the middle.
My question is - What is causing the fractures and what can be done to
eliminate it? I am pretty sure of the correct answer, so don't beat me up
too much on this one, I had to ask. I need reassurance.
Thanks in advance for your help!!!
Steve McBride
Manufacturing Engineer,
Frontier Engineering Inc.
(405) 624-6821
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]> *
* with <subject: subscribe/unsubscribe> and no text in the body. *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] *
***************************************************************************
|
|
|