PCB hole sizes

[soggybag]

I'm designing a PCB on the computer. I'm trying to decide what sizes to use for the holes. Seems 1/8 watt resistors and many caps use about a 15mil hole. But this is a tight fit.

I'm guessing the size for 1/4 watt resistors and most other parts is probably twice that size.

What is the size of 1n400x diodes? These have thicker leads.

What is a good size for IC sockets?

[Andi]

Depends on the part, I'm afraid - get some digital verniers and check them each.

I use 0.6mm for 0.25W resistors, transistors and capacitors, 0.8mm for wires (7/0.2) and IC sockets, 1mm for 1N400x diodes and push-in sockets. 1.2mm for trimpots.

[R.G.]

If you're going to do any serious PCB layout, (guess what comes next, based on what I post here...)


Yep, that's right, go look up the datasheet for the part and it will have mechanical drawings which specify the lead sizes.
Failing that, go to Harbor Freight and buy one of their 6" dial calipers, usually under $20 and measure the leads. Add 0.010" to the lead and make the hole at least that big.

[John Lyons]

I use a .035/#65 bit and that covers me all the way up to and including 1N400x diodes.
Lifes too short to drill many different sizes

John

[soggybag]

Thanks for the replies. I'm new to making PCBs with the computer. I just had some PCBs made. I used the default hold size of 15 mil. They are all too small! I'm trying to think of what I can do with the boards I now have. I'm thinking I can mount a few parts on the surface. Some of the parts just fit, if I use 1/8 watt resistors. I tried drilling out the holes but they are plated through.

[R.G.]

The problem with holes too large is that solder has to cover the gap, and too big leaves you prone to bad solder joints. More of an issue with wave solder, I admit, but I have had bum solder joints across too-big holes before.

0.030" is a reasonable default. The default size for transistors, DIPs, and 1/4W resistors on down is either 0.028 or 0.025. 0.035 will barely take a 1N400x lead, but it's much easier to assemble at 0.042. I would never go below 0.025 unless for a via.

But then the factory that does my board stuffing wanted me to open up all the small stuff holes to 1mm/0.03937, too. And they were hand inserting.

The lead-plus-0.010" is that most industry guides say, and I think it was in mil spec, back when there was a mil spec.

[bumblebee]

I generally use a 1mm bit for all holes as the variance is so small I dont see the point in using different size bits.

[Andi]

I find that a 0.6mm hole is right for resistors, caps, transistors and small diodes - no problem pushing the legs through but tight enough that the components don't fall out when you flip the board over. I used to do everything 0.8mm but it's no more work for me to have all the holes the right size.

[R.G.]

This is a REALLY GOOD THING for PCB layout guys to have.
http://www.widgetsupply.com/page/WS/PROD/specials/SFB3-004