If it is resin smear and the circuit is working normally now, the risk is very
low that you will ever have a problem with it. However, if the problem is due
to Post Separation or Inner Layer Separation, rework and thermo/mechanical
shocks can increase the resistance. Some circuits are very sensitive to
changes in resistance and therefore, you may start getting intermittent
failures (like a "cold solder joint").
Even with the Post Separation defect the odds are in your favor that the
circuit will never fail in service. You will have to do a risk assessment. If
the environment is benign and the consequence of a failure is small, you may
want to leave the board in service. On the other hand, if the environment is
harsh and/or a single failure could cause server harm, you may want to scrap
the circuit board and replace it with a good one.
No matter what your decision, you should insist that the problem be fixed. All
interconnect problems can and do cause functional failures sooner or later. It
is virtually impossible to screen out these defects from bad lots or to measure
their individual effect for every situation. The only "safe" answer is to
eliminate the defect...Not an easy task I can assure, but necessary
none-the-less!
Regards,
Jim Reed, Texas Instruments, Austin, TX
Voice = 512 250-7172,
Fax = 512 250-7967,
Email = [log in to unmask]
Pager = 800-759-8888 ID 289-7077
------------------
Original text
From: Michael Barmuta <[log in to unmask]>, on 4/16/97 2:48 PM:
Art: There is not one simple answer. Many factors come into play.
1. Board material of construction
2. Board thickness
3. Degree of smear(how bad is it?)
4. Interface connect mechanism(els.Cu,direct metal,etc.)
5. Applied circuit power
6. Product use environment(mechanical shock, temp variations,
vibration, g loads, frequency of these conditions etc.)
7. Product reliability and liability
I don't know if this is a hypothetical question or you're sitting on a box of
expensive product and not sure what to do with it.You could try some "shake n
bake" testing based on the worst type of condition it will be used in. This
could give you an insight into the severity or degree of the problem and
possibly weedout the bad product.
Product application is a key player in this. My advice is if in doubt don't,
otherwise it could be really costly.
Regards
Michael Barmuta
Fluke Corp.
Everett Wa.
206-356-6076
On Wed, 16 Apr 1997 09:09:08 -0700 Art Shuler wrote:
> From: Art Shuler <[log in to unmask]>
> Date: Wed, 16 Apr 1997 09:09:08 -0700
> Subject: Resin Smear
> To: [log in to unmask]
>
> Any opinions to the following question would be helpful:
>
> Let's say a Multilayer PWB is known to have Resin Smear at the
> interconnects. The board has been completely processed and installed in
> the unit, and the unit is working properly. What are the chances of the
> Resin Smear propagating into complete separation after a period of time,
> causing the board to fail due to open circuits?
>
> Art Shuler
> [log in to unmask]
>
> ***************************************************************************
> * 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] *
> ***************************************************************************
>
***************************************************************************
* 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] *
***************************************************************************
***************************************************************************
* 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] *
***************************************************************************
|
