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April 2013

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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Fri, 19 Apr 2013 09:08:52 -0600
Content-Type:
text/plain
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text/plain (68 lines)
Good morning all,

 

I've been looking at a board that we will be building in several weeks,
and one of the packages on the is a 16-pin VQFN. Part number is:
QF1D512-QN-T. Datasheet is here:

 

http://www.quickfiltertech.com/files/QF1D512%20SavFIRe%20Datasheet%20A15
.pdf

 

I always check the datasheet to look at the recommended solder paste
footprint to ensure that the stencil I spec out falls within the
manufacturers recommendations. Yeah I know that sometimes the
manufacturers footprint doesn't always work, but I look at it anyway for
a sanity check.

 

Well, the datasheet doesn't have one, and I sent a contact email to
QuickFilter asking if they had a recommended solder paste footprint for
this part and didn't receive a reply, so I called them the next day.
When I spoke with them I was told that they didn't have a documented
footprint for the part, but there was one thing they wanted me to know,
which was to NOT print solder paste for the center pad beneath the part.
"But why?" I asked, "there's a pad there in the drawing of the part...".
I was told that the pad is completely non-functional, and the reason
that it's there is because they didn't want to have to come up with a
custom lead frame for this part, and this was the lead-frame that was
"off-the-shelf" and what was used.

 

Well, I was surprised! I mean this does make things easier for assembly
by not having to worry about soldering the center pad, but this is the
first time I have ever ran across something like this. Have any of you
ever run across this on any other QFN parts?

 

Have a good Friday everybody!

 

Steve Gregory

Process Engineer

Kimco Design and Manufacturing

652 N. Five Mile Road

Boise, ID 83713

(208) 322-0500 Ext. 3133

 


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