QFN footprint

[mobile]

Hi,

I've been watching many many videos on youtube and I really like that topic.

So normally during my daily job I'm a software engineer, recently I decided I would like to swing over to electronic engineering (if possible :-). I have access to Altium (through my employer). So I'd like to understand some kind of video grabber and try to make one by myself.

It should be a simple design since it's a one chip solution.

I tried to desolder an existing device (heated up the PCB) just to see the footprint:
http://imageshack.us/photo/my-images/210/qfndesoldered.jpg/

So at first I tried to make some kind of PCB library with Altium (Tools -> Component Wizzard -> QFN)
however the dual row layout probably cannot be done with it it seems.
 
What I noticed through the componentwizard is that there's some solder mask expansion I just wondered that kind of solder mask expansion seems to be so big that the footprint might end up with no solder mask at all.. But from the de-soldered sample I can clearly see a solder mask in between the pins.

As far as I understand the solder mask expansion is the gap between the copper/pad and the solder mask, I don't understand how that should apply to those QFN packages.

I have the package specs I will add them asap.
I wonder how can that one be drawn with Altium designer?

(I'm an absolute beginner please correct me if I'm wrong with something here ^^)

[mariush]

There's a very good blog that explains a lot about various footprints, here's the QFN footprint:

http://blogs.mentor.com/tom-hausherr/blog/2011/04/06/pcb-design-perfection-starts-in-the-cad-library-part-15-qfn/

There's also some very good posts towards the beginning of the blog but overall the whole blog is a very informative one.

Hope it helps.

Look into Camtasia Studio for screen capturing.

[mobile]

Hi mariush,

thanks for your reply! I'm studying it :-)

here's the QFN dimension (which I promised to show)
http://img542.imageshack.us/img542/1033/qfndimensions.png

I'm just trying to get that thing somehow into the altium PCB/Schematic library but having some hard time to understand how to do that.. I'll keep playing of course :-)

[David_AVD]

Perhaps you can do the outside set of pads via the wizard, then add the inside set manually.  Shouldn't take long.

[mobile]

I'll try my luck tomorrow and will post my result here once it's done :-)