pcb
Is there a standard that gives the hole and pad size for soldering a wire to a PCB?
The IPC-7251 standard gives hole and land diameters for a given lead diameter. But because the finished hole diameter is 0.25 mm bigger than wire, these holes are difficult to get stranded wires into without them unraveling.
I cannot use a connector for this application.
Yes, this is done in the DRC settings. One of the parameters sets how far traces must be from board edges, which includes the edges of unconnected holes. I don't remember the exact setting name, but run "drc", look thru the settings, and you should be able to spot it.
You are saying you looked in the DRC but didn't find it. It's actually quite obvious and one of only two setting under the "Distance" tab:
I don't think you should depend on the holes to locate the part when tolerances are important. I agree with your 10-15 mils as I said earlier here (in metric 0.25 to 0.4mm).
Instead, make up a jig to hold the parts in the proper location while they are being soldered. It can be fancy for wave soldering or something simple that holds the parts while being hand soldered (perhaps fashioned from the mating part such as the punched chassis).
Round pins are a particular hassle if you call it too close- at least with square or rectangular pins you can skive off some plating inside the holes at the corners of the pin and still force the pin in. If you insist on the using the holes... um, maybe make the peg round and the hole square.. (call out slot-drilled square holes in the PCB).
Best Answer
A general rule of thumb would be to make your hole diameter (after plating) approximately 10% larger than the diameter of your wire. However, this will often lead to very small diameter differences. For example, 18AWG 16/30 stranded wire has a diameter of 0.046 inches (1.17mm). This value +10% gives you about 1.29mm, which is a difference of 0.12mm.
Generally your best bet is to twist the end of the stranded wire to help prevent it from unraveling. You can increase the hole size to an extent, but it depends on your application, plating, type of wire, solder, current, etc. how much you can increase it before you run into issues. Personally I probably wouldn't go beyond 20%.