Hi Wayne - you have good timing with your question as I can give you the
latest info from the IPC committee meeting last week. The JSTD-001
committee had a comment submitted asking for void criteria for BTCs.  A
small task group with global representation from several industry product
segments was formed to review the issue. We reviewed the issue with data
resources from consortia, IPC and SMTA resources.  We had one very specific
conclusion: Any void criteria that would be put into the JSTD-001
specification would be addressing solder joint integrity only. Many BTCs
have either thermal or electrical functional needs which is a design issue
that should be addressed during the product design phase.  Here is what the
task team responded back to the JSTD-001 committee with:

"The JSTD-001 QFN Void Criteria task group recommends that a "request for
data" be issued as a review of the current available industry data was
found to not be sufficient to establish a data based maximum void criteria
for solder joint integrity. The voiding criteria requirements pertaining to
the functionality of a QFN or other Bottom Terminated Components (i.e.
thermal or electrical performance) are a design function and not part of
the IPC-JSTD-001 specification scope. The "request for data" responses
should be sent to the QFN Void Criteria task group by October 31st, 2018 so
that they can be reviewed prior to the 2019 IPC JSTD 001 APEX committee
meeting. The  JSTD-001 QFN Void Criteria task group will provide a void
criteria recommendation to the IPC JSTD 001 committee based on the data
submissions at the  2019 IPC JSTD 001 committee meeting."

The void number you listed - especially the 25% - have little to no
technical data justification in terms of solder joint integrity.The
JSTD-001 BTC Void task group is looking for DOE/test/investigation data and
there will be a recommendation to the JSTD-001 committee for review at the
2019 committee APEX meeting. I understand that seems like a long time but
any criterial that is put into the JSTD-001 specification must be done
based on data as those requirements results in costs to the industry.

A number of OEMs verbally committed to providing BTC void data to the
JSTD-001 BTC Void task group so I am confident the issue will be resolved
within the year. If anyone has  data they would like  to submit to the task
group, please send it to me and I'll make sure it is included in the data
review.

Let me know if you have any additional questions.


Dave Hillman
IPC JSTD-001 BTC task group lead
Rockwell Collins
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On Sat, Mar 3, 2018 at 6:18 PM, Wayne Showers <[log in to unmask]>
wrote:

> I do not know of an IPC criteria on this.  I have seen 25% (The BGA
> criteria) cited, but this is not, to my knowledge accurate.
> The limits I have used in the past are 50% Coverage with no void exceeding
> 15% in the center and no more than 10% anywhere else.
> I also used a 70% Coverage and 10% Void criteria for a very heat sensitive
> application.
>
> Question 1: Is there now a citable IPC criteria? and if NO,
> Question 2: What are some of this groups recommended criteria?
>
> Thanks and Regards, Wayne Showers, NPI/Technical Manager, 4Front Solutions
>