Screaming Circuits: CAD Parts Libraries


Missing Mars Probes

Back in ancient times when multi-legged beasts ruled the earth, there were a lot more standards. Or maybe there were just fewer total things resulting in fewer total variations, which looks like more standards. In any case, if you got... Read more

Via in Big Pads

The answer to the question: "is it ever okay to put open vias in BGA pads?" is simply No. It's no, no, no, no, not ever!!! That makes it easy. No technique to worry about. No tolerances. Nothing. Just don't... Read more

Via in Pad x 8

Here's an interesting via in pad case. On the one hand, the footprint is very symmetrical and clean looking. On the other hand, it has open vias in the pads. At first glance, I thought this was a DIP footprint... Read more

How not to treat your BGA friends

Over the years, most of what we see are good PC boards. But some standout in the other direction as examples of what not to do. Some didn't make it through the board house alive. Some were unknowingly rendered useless... Read more


It's pretty important to have unambiguous polarity markings and pin one markings printed on your PCB. In theory, for SMT parts, it really shouldn't matter; the centroid would take care of the placement orientation. But, you may have noticed that... Read more

Connectors Kill

Lot's of types of components can cause footprint woes. QFNs have their center pad issues. BGAs have escape via issues. But the most common footprint issues seem to be with connectors. At least with chips and discrete silicon and passive... Read more

More CAD footprint woes

AT this point, I really shouldn't call them "woes." More like business as usual. I'm talking about the need to make custom footprints, or at leas modify footprints. Back in the old days, the only thing needed to make footprints... Read more

Shrouded vs. non-shrouded

A connector isn't a connector isn't a connector. In this photo, the original PC board was designed to have an unshrouded break-away header, as shown in the inset on the right. I measured it. The entire header fits within the... Read more

"Shrinky Dink"

I had some "Shrinky Dinks" when I was a kid. Amazingly you can still buy them. You can also use that concept in your prototyping. I did that recently. I have a robot board design that I'd like to shrink... Read more


In the land of protorypes, sometimes "close enough" is good enough. That can save money on PC boards and assembly when a particular package version of your part is out of stock. But, it's not universal. Sometimes you can't go... Read more