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August 2011

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 31 Aug 2011 16:12:04 -0500
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Hi Mark - if you leave the thermal vias open then the solder will thieve 
down them leaving the center pad "solder starved". I recommend you use 
some fabrication format which permits the vias not allowing solder to 
thieve - aka either capping them or filling them. The IPC-7093 standard on 
Bottom Termination Components also may have some helpful information.

Dave Hillman
Rockwell Collins
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Mark Larson <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
08/31/2011 02:52 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Mark Larson <[log in to unmask]>


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Subject
[TN] QFN with solder slug






I am curious how others are handling these parts for soldering. Do you 
leave the thermal vias in the slug covered or uncovered with solder mask? 
Do you fill with anything? What size hole on a 62 mil board? Tie to all 
GND planes or just the back side? Thermal relief the via or bury it in the 
plane?

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