Screaming Circuits: QFN and DFN

PROTOTYPE AND SMALL VOLUME
PCB ASSEMBLY MADE EASY

Most parts in place

Mark Rules has made a bit of progress on his tiny motor controller. Someone suggested that he look at a rigid-flex board so that the driver could be wrapped around one of the motors. The idea would be to have... Read more

QFN solder voids

I've written a couple of posts about QFN float problems (here), (here) and (here). There is another problem we run across as well. With larger QFN parts, the opposite problem can occur in the center pad area. When the square... Read more

QFN CAD Libraries

In previous posts (here and here), I've talked about QFN layout issues and solder stencil openings. Here is an example of a the library that follows the component manufacturer's and our recommendations. First step is the copper layer. In this... Read more

QFN solder paste stencil guidelines

To better illustrate the proper way to make your solder paste stencil for QFN parts, as I discussed in the post just before this one, I went to the back room and took a couple of photos of good and... Read more

QFN float be bad

At a recent tradeshow, I received a sample part in a 3 x 3 mm QFN package. While I haven't tried yet, I'm pretty sure that, like a water bug, the part is light enough to float on a water... Read more

Via in pad?

In general, we would recommend against placing vias in any pads that will receive solder during the assembly process. A couple of undesirable events can happen depending on the method used during board fab. If your vias are left open,... Read more