Screaming Circuits: QFN and DFN


QFN / QFP switcheroo

Here's an all too familiar face. We see this a lot with chips that have both a QFP (quad flat pack)and a QFN (quad flat pack, no leads) package. Especially if the QFP packaged part has been around for a... Read more

Good QFN, Good QFN Paste Layer

I write a lot here about things that go wrong with various layouts. Hopefully by doing that, I can help some of you avoid common pitfalls. But I should probably write about more good things though to balance it out.... Read more

Parts Library Strikes Again

Here's a little bit of a parts library or wrong package problem. I'm not exactly sure how it happened. The board may have been laid out for a small QFP footprint but then a QFN part was purchased. The footprint... Read more

A Couple of Interestingly Tiny Parts

Yeah, I'm kind of a broken record on this subject. But, you have to expect that given where I work and that I believe in what I do, I'm going to be such a broken record. I ran across these... Read more

A Little Pad In That Via

Here's an interesting via-in-pad situation we ran across a while ago. I'm not sure what the chip is. Probably a processor or an FPGA that generates a bit of heat. The intention with the layout was on the right track.... Read more

CAD Library or Substitution Issues

We recently ran across an issue out on the shop floor that was most likely due to the components library in the CAD package. A QFN part was sent for this assembly but the land pattern on the board was... Read more

Silver via problems

Here's an interesting via situation that I hadn't heard about until just recently. In these two cases, the engineer has a QFN with a center pad that is required more for grounding then for cooling. Given the lack of criticality,... Read more

Microvias, Blind and Buried Vias

In a few previous posts, here, here and here, for starters, I've discussed the dreaded via in pad and hopefully, given some useful information about what to do if you must put vias in pads. In the image, (A) shows... Read more

Soldermask Via Caps

Today, I'll start with the basics: Soldermask via caps. This isn't the best, but it is the easiest. Almost any board house can pull this one off with a reasonable chance of success. In this example, what we're looking at... Read more

Via in pad methods

Here is another method for dealing with QFN heat slugs with thermal vias. While the best option is to plug the via holes with metal early in the board fab process and then plate over with copper, there are a... Read more