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December 2013

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From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 20 Dec 2013 06:36:02 -0600
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Hi Reuven - I think that is a possible idea, however, what void percentage 
do you suggest and what technical data/investigative studies do you have 
to support the recommended void percentage? One thing to consider is that 
if a workmanship topic is missing from the JSTD-001/IPC-610 documents, it 
doesn't mean that the topic hasn't been reviewed.  The IPC committees work 
 hard to only put workmanship criteria in the specifications that is 
necessary and is supported by data. An example - the IPC-7093 BTC 
committee completed extensive efforts looking at the voiding of QFN 
thermal pads and found no industry consensus on a void percentage 
requirement. The JSTD-001 committee therefore has not included a maximum 
void percentage requirement in the 001 specification and the IPC-610 
specification shows no examples of voiding requirements of QFN thermal 
pads. The workmanship criteria show in the JSTD-001/IPC-610 specifications 
results in added costs to products and processes so the committees are 
very careful to not add requirements unless there is technical 
data/justification. I know a number of OEMs/CEMS who have a 50% maximum 
void requirement on the QFN thermal pad unless the component has specific 
thermal or electrical functional requirements. The IPC-7093 specification 
has some good information on the topic of BTC thermal pads and voids. The 
committees would welcome any investigative data on the topic too.  Happy 
Holidays!

Dave Hillman
Rockwell Collins
[log in to unmask]



From:   Reuven Rokah <[log in to unmask]>
To:     <[log in to unmask]>
Date:   12/20/2013 12:48 AM
Subject:        [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs
Sent by:        TechNet <[log in to unmask]>



Hi TechNets,

I didn't see in the IPC-A-610E any acceptability reference in regards with
the percentage of voids in solder joints of exposed thermal pads of QFNs 
or
other components with exposed thermal pads.

I recommend to add it in the next revision.


-- 

Best Regards,

*Reuven Rokah*

Mobile: 972-52-6012018
Tel:        972-3-9360688
Fax:          076-5100674
 <http://www.rokah-technologies.com/>[log in to unmask]
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