Hi Ben,
Actually, it was from the COO. Here's his response:
"Hi Steve,
Thanks for calling and sending the email. We don't have a
document that specifically calls out the recommended solder paste
footprint, however, I am attaching a solder paste view from one of our
development products - we've built a bunch of these so it is quite
robust. As you will notice, there is no paste under the part, only on
the lead fingers. Let me know if you need anything else from us."
Also I was sent a *.pdf of the solder paste layer of their development
board that shows they don't print solder paste for the center pad:
http://stevezeva.homestead.com/QF1D512_toppaste.pdf
This was the first time I've run across a situation like this. But I
guess there's a first time for everything I guess...
Steve Gregory
Process Engineer
Kimco Design and Manufacturing
652 N. Five Mile Road
Boise, ID 83713
(208) 322-0500 Ext. 3133
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gumpert, Ben
Sent: Friday, April 19, 2013 9:39 AM
To: [log in to unmask]
Subject: Re: [TN] QuickFilter 16-pin VQFN
Steve,
I seem to remember seeing something about it not being required to
solder the center pad on some other QFNs, but I don't recall being told
not to.
Makes me wonder if you were talking to a designer that didn't want the
pad connected electrically, but doesn't really understand the soldering
process (or reliability).
Ben
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Friday, April 19, 2013 11:22 AM
To: [log in to unmask]
Subject: EXTERNAL: Re: [TN] QuickFilter 16-pin VQFN
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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