Customer part with small qty you might have to be - non standard. But the design sign off on the non-std and need to be prove using rel test + function test - nothing like antenna type or ground bouce, data it is OK. Normally prototype stuff. Hopefully, the leadframe is covered with solder (not exposed copper ground). Normally, QFN is high frequency or high power device, ground is essential for thermal and function, but yours might be different. (non thermal, low frequency). My 2 cents.
Joyce Koo
Researcher
Materials Interconnect Lab
Office: (519) 888-7465 79945
BlackBerry: (226) 220-4760
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, April 19, 2013 11:09 AM
To: [log in to unmask]
Subject: [TN] QuickFilter 16-pin VQFN
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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