I’ve covered some basics of drilling in the article, How to make a printed circuit board step by step. This is an updated and more specifically how to drill a PCB guide or at least how I did it guide. Having been totally impressed with my latest efforts of producing a PCB from photo paper laser printing methods, I wasn’t going to mess it all up by bodging the drilling process.
This could be a problem though as most of the decent drilling I had ever done was at Leicester University using a very decent table mounted PCB drill.
Most of my home drilling has been inaccurate to say the least, using a hand held thirty year old PCB drill from a hobbyist shop.
Looking at how small the pads where on the PCB it became fairly evident that I wasn’t going to be able to use my usual 1mm drill bits. It was going to have to be .8mm if I wanted any pad left to solder on to and given my past experience of breaking 1mm drills with my hand held thing I had to come up with another idea.
Drilling a PCB
The problem with that old hobbyist drill was that it vibrated too much and maybe something had become slightly bent over the years as when you tuned it on with a 1mm drill bit in it, it just looked blurred as it spun so something was amiss. Another problem was that I didn’t really want to spend much either. I had an old plastic cased blue coloured Black and Decker drill from years ago, a pretty small and simple no hammer action thing. Upon putting a 1mm drill bit in it and pulling the trigger I was pleasantly surprised to see it spin quickly and accurately and not the blurred mess my other one produced. This would give me half a chance to drill accurately.
I was going to have to spend something though unfortunately and that was going to have to be on a drill stand or drill press. For the price I could justify it as hopefully not only would it mean I could drill PCB’s in the future but it would also mean I could use it to drill front panels and cases for my impending electronic projects. I was amazed at how oval I could get holes hand holding a piece of aluminium in one hand with a circular revolving drill bit.
Circuit board drill bits
I chose to drill the board before I cleaned it, I’m not sure if it would make a difference either way but I like to clean the board just before I solder it so it stayed the way it was while I drilled it. I also decided to drill the whole board with a .8mm drill, I recently took delivery of a production board and they appear to have used a .8mm drill for every hole so I figured I would do the same. I could always enlarge holes at a later date. It seems better to just use smaller holes now anyway as the component leads seen to be getting thinner and it’s more of a problem for me to solder components with a lot gap around them rather than have components whose legs are too large for the holes. Next time I’m going to use carbide drill bits, but I stuck with steel so I have something to compare.
The holes are also at a perfect ninety degree angle to the board which can’t be said of my previous efforts and setting the drill depth gauge so the drill moves a minimum also helps accuracy. As the board is flat and only millimetre thin you can have the drill bit a couple of millimetres higher than the board and you only need to go a couple of millimetres through the board as well. All in all you can probably set it so you only have about 5 mm between the high and low settings. So that’s not much movement up and down.
The drill stand has been a huge success. One of those how have I managed without one moments. I certainly wouldn’t want to be without one again for any drilling job to be honest. It just made the whole PCB drilling process so much more enjoyable. Not something I would now put off but look forward to doing. Being able to hold the board in one hand and control the drill with the other was great and I didn’t snap a drill bit which is unheard of for me.
PCB drill sizes
Years ago when we made PCB’s at university the holes we drilled were almost all 1mm and .8mm for IC’s and IC sockets. The pads were much larger in those days and I don’t think there would be much pad left if you drilled with a 1mm drill.
I printed a fairly recent “standard” PCB design that I downloaded and I think that .8mm is now the “normal” size to drill most components. That’s certainly what I’ll be doing from now. There are still some components that may need a larger hole to be drilled. You will probably spot these due to them having larger pads.
The ones that caught me out and needed to be enlarged were pre-set resistors. Some capacitors may also need this doing. It’s a lot easier to enlarge a hole that’s too small than trying to solder a component in when there’s no pad left!
I only used a pretty basic .8mm steel drill bit which was not only cheap from an electronic hobbyist supplier but also getting on a bit. I’ve now ordered some more hopefully better quality one’s off the internet which should make the holes a bit cleaner. Rubbing my finger over the holes you could feel a definite edge both on the copper and component side. But it was far better that I thought it would be.
As you can see there is a bit of an edge to the holes. A steel .8mm drill bit was used and not even a new one so I'm not surprised but it does give me something to compare to when I get a carbide bit.
It was my eyes that could have done with a helping hand in all honesty and maybe I’ll try some kind of magnifier maybe next time. Also the fibreglass drillings tend to build up over the surface obscuring where you’re drilling so I frequently had to remove the board from the platform and wipe my hand over it. Maybe some kind of fan could be used to blow the debris off the board if I was going to be doing a lot if drilling.
I’m just trying to find somewhere or clear a little corner where I can leave the drill and stand set up permanently now.
So far it’s by far the best PCB I’ve etched and now I’ve drilled it without messing it up. Hopefully, if you’re a novice this, how to drill a PCB article has helped give you some information and point you in the right direction.