Sanderstrom (sorry, but I don't know how to do the oomlot) wrote



Strictly speaking, failing to provide thermal relief, to a power/ground plane, for any plated hole that must be soldered is a problem whatever soldering mechanism you use. It is more of a problem for machine soldering (wave, reflow, vapor phase, whatever) than for hand soldering. If your board is going to be assembled by hand then you can accomodate a solid plane connection by soldering each side independently. You will still have a solder void inside the barrel of the hole at the plane, but your connection should otherwise be okay. DO NOT try to force the solder to wick through from one side. If you heat the connection enough to compensate for the heat sink of the plane, then you are very likely going to delaminate the pad/trace(s).

Clearly the best choice is to provide good thermal relief between any hole that is to be both soldered and connected to a power/ground plane. Per the IPC Standard IPC-2222, 9.1.2 Thermal Relief in Conductor Planes, the width of each web (or spoke if you prefer) should be equal to 60% of the pad diameter divided by the number of webs (or spokes) connecting the pad to the plane. In other words, the sum of the widths of the spokes will be 60% of the pad diameter. If convenient, use four spokes. If necessary you can reduce this number to three or two, but you should avoid using a single spoke if at all possible. All of this also assumes that you have chosen the appropriate pad diameter for the diameter of the hole.

Good Luck.

Joe