[sdiy] PCB / Panel Manufacture

[Ingo Debus]

> Am 08.02.2020 um 19:52 schrieb Shawn Rakestraw <shawn at epicpoolsga.com>:
> 
> Thanks for pointing out the small via and acid trap, Vesa. I do not understand your comment about no thermals on the pads. Can you or someone else briefly describe what that means?

Thermals, also called heat traps, make soldering easier. A pad inside a big copper plane (mostly a ground plane) is connected to that plane via four short traces rather than being just a part of the plane. You can heat up the solder joint without having to heat up the whole plane. I think I saw thermals on the pictures of your board. AFAIK Eagle places them automatically.


> Ingo, I thought that I need all of my grounds connected to the center tap. If I separate them, the capacitors will form a "new" virtual ground for the DC output side?

Sure there are different schools of thought, and if you ask n layouters you’ll get n+1 opinions :-)
Of course all grounds have to be connected. But you can do this in different ways. Keep an eye on the currents flowing through the traces. In a power supply, the traces from the rectifier and the center tap of the transformer to the big electrolytics carry a hefty ripple current. The electrolytics are charged only during a short time around the peaks of the ac input voltage. No matter howthick these traces are, there’s always some voltage drop across them. This does not matter as long as these traces are not shared for other current paths.

Ground planes, as on your layout, are a good thing. But it gets difficult to predict where the currents are flowing. So I like to keep the ripple-ly traces separate from the ground plane.

Ingo