Hi Michael.  

We had some experience with component cracking due to moisture entrapment,
from TSOP, PQFP, ICs and some Memory DRAMs.  We required the supplier to
provide the components in hermetically sealed packages and once received in
manufacturing and the package was opened we had a given time period to use
up all the components.  If the components were not used up within that given
period of time, and the monitoring process for humidity within the facility
exceeded the boundaries of the requirements, then the components were baked
for moisture removal.

The effect of component cracking or popcorning is long term reliability of
the product with the use of those components.  In our case the cracking
occurred on the bottom side of the package and was not visible unless the
component was removed, which by the way was the way we found out about the
cracking in the first place.

IPC has documentation regarding component cracking, you should contact them
and get copies to establish your process.

Hope this helps.

Leo Lambert
Technical Director
EPTAC CORP.
At 03:21 PM 9/30/96 -0400, Michael Branning wrote:
>My company is setting up a small surface mount line. We have been building
>thru-hole boards with one PQFP package per board (IC only available in SMT)
>for some time with very good success. We've been using hot air (Leister)
>rework tools to mount the SMT parts by hand. However, we are in the process
>of designing some full SMT boards (one sided).
>
>We've just purchased and started using a Lovell convection oven and a small
>manual screen printer. Up till now, we generally have ignored the
>humidity/exposure warnings on the IC packaging. Is the only effect we must
>be concerned with "popcorning"? Does the package always dramatically fail?
>Or can problems be created that are invisible to the naked eye? If the parts
>must be baked, what equipment would be suitable for small production runs?
>(50-100 boards)
>
>Sorry to sound like a rookie; thanks for the help!
>
>Michael Branning
>Avtec
>
>***************************************************************************
>* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
>***************************************************************************
>* To unsubscribe from this list at any time, send a message to:           *
>* [log in to unmask] with <subject: unsubscribe> and no text.        *
>***************************************************************************
>
>
>

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************