Screaming Circuits: QFN and DFN

PROTOTYPE AND SMALL VOLUME
PCB ASSEMBLY MADE EASY

Large Via In Pad

I haven't written about via in pad in a while, but the issue hasn't quite gone away yet. This particular QFN, to the left, has the vias tented, which is good. However, it could be better. If you look close,... Read more

Many Faces of the QFN

When I first started using a CAD package for circuit design, I couldn't understand why the software didn't come with all of the standard footprints and why that wouldn't be good enough. That level of ignorance was hopefully pretty short-lived.... Read more

Inverted QFN Land Pattern

Have you ever experienced the heartbreak of inverted land pattern? It's not supposed to happen, but every now and then, it does. Maybe something happened when creating a custom footprint. Maybe, somehow it got inverted in the CAD software and... Read more

What's Wrong With This Picture?

What's wrong with this picture? I forgot to warn you that there'd be a pop-quiz. It's only worth 10% of your final grade though, so not to worry. We're fully into the rainy season here in Oregon now. It's dumping... Read more

Tented QFN/QFP Via in pad

Here's a pretty decent example of mask-tented vias in the thermal pad of a QFP. Most manufacturers recommend no more then 100 - 125 um wider than the via to minimize voiding and thermal insulation in cases like this. This... Read more

QFN Solder Mask Issues

Here's another QFN oopsie. Presumably, in this case, the flag pad on the QFN is needed as a heat sink and those vias are designed to conduct heat to the other side of the board. That's all good. But, with... Read more

Lets Get Small

I’ve been slowly working on this microcontroller board (very slowly) for a while. I’m using PCB123 and some new, very small components to put it together. I’m amazed at the changes that have happened recently in this industry. Change has... Read more

Speaking of Common QFN Issues...

Here is the classic QFN via in pad. It simply isn't possible to solder the center pad properly with that much open via real estate. The best way to deal with this is to fill the holes with something that... Read more

Novel QFN Land Pattern

Because the center land is so much bigger then the side pads, QFN solder paste can be a problem if not handled properly. I've written about options before, but here's another approach. I ran across this QFN land pattern the... Read more

PCB123 QFN 28 footprint

First things first. I still haven't received the little ZigBee modules. Microchip said they'd ship out on the 14th so I shouldn't expect any different. I'm going ahead and getting started on the schematic anyway. When I get the modules,... Read more