Screaming Circuits: Via in Pad


Hi Ho, Hi Ho, It's off to Via I go

Here's just another via in pad story. In the first example (the green one), all those open vias are like 15 miles wide - okay, drop the "e", but they're really wide. You can't quite drive a truck through them,... Read more

Vias under Power Transistors

Normally, a power component like this would have a big pad and some heat dissipation space under the heat slug. It might even have thermal vias going to another heat pad on the back side of the board. If it's... Read more

Oopsie in the Center Pad

Darn. This PCB don't look so good. Quick - name two things wrong with it... If you guessed that the solder mask is inverted and the vias are open, then you were right. Sorry. No points will be given for... 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

Moleish SMT Heatsinks

Well, no one ever did give me a reasonable estimation at how deep a mole of moles would cover the earth. But then, I didn't go back and dig up my old chemistry notes and see if I could find... Read more

Very Compact Layout?

How do you do it? We've told you not to space things too close. We've told you not to put vias in pads - like a million times. We've told you to watch out for spurious vacuum tubes. Okay, the... Read more

0.4mm pitch BGA pads

At 0.5mm pitch and larger, we generally recommend non-solder mask defined (NSMD) pads for BGAs. The NSMD pad will allow for better adhesion with the solder being able to grip the sides of the copper in addition to the top... 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

0201 and The Blind Via

0201 size passives can help drop down a PCB form factor, but to really get the most compression, you need to get rid of all of the traces. One way would be to put little transceivers on each lead of... Read more

Via in Pad - Right and Wrong

Here's a pretty simple via-in-pad example that has both good and bad. It's an SOIC-8 so it's a pretty big part. It's not super roomy, but there is plenty of space on the PCB to do things a little different.... Read more