Is there an electronic rule or just a rule of thumb regarding through hole solder pad dimensions?
That is, if I have a 0.025 inch diameter drill hole (suitable for 24AWG wire), what should be the total diameter of the solder pad?
This is to have an appropriate surface of pad to solder on for both good electrical and mechanical properties.
What ratio should I use?
For example, x2 or x3, would give a total diameter of 0.05 and 0.075 inches respectively.
Or I can try to have the same surface between the drilled hole and the soldering pad. Doing some math, that would mean taking a sqrt(2) ratio.
However, that looks (at least visually) a very small surface.
Any suggestion? Or even pointer to material for good PCB design practices where that can be explained?
Thank you.
Best regards,
Best Answer
You can calculate a minimum annular ring from the hole size. If you use a 10 mil annular ring then a 25 mil hole would lead to a 45 mil pad size.
You'd want to make it larger than that if possible if there is mechanical stress on the leads and much larger if there is mechanical stress and the PCB does not have plated-through holes.
Generally it's a bad idea to just solder a stripped loose stranded wire into a hole in the PCB, the wire ends up breaking off just above the PCB just from a bit of handling.