PCB Isolation routing

One of the first things I did upon getting a desktop CNC machine was to research software that would allow me to route and drill PCB’s (printed circuit boards) without the mess of chemicals.

Printed circuit boards don’t necessarily have to be expensive to buy from a good board house. In fact I’ve seen them as low as $30-$40 with silk screen and solder mask. The problem with many of the low price boards is lead time. At the very least you’re talking a couple of days.

But what if you want it NOW? Or at least the same day? A time honored method has been to start with a copper clad board, apply “resist” in the pattern of your circuit, put it in a chemical bath to eat away the unwanted copper, then drill holes for components, vias, etc.

There’s absolutely nothing wrong with that method. You can make some really good boards this way, with fine detail. There are different methods of getting your circuit pattern onto the board, such as pen, tape, photo resist, etc.

If you have access to a small CNC router, you can avoid the hassle and mess, and also precision drill and contour your board to any shape you want. You’ll have a new set of hassles of course :) But that’s all part of the fun, right?

The software I’m about to describe assumes that you will be able to produce gerber files. That may well be a severe limitation for many. Gerber files are generated by PCB design software, and not everyone has access to that. So this method generally won’t work well  if you have hand drawn circuits, patterns cut from books or magazines, etc. Sorry. But this will give you a chance to learn something new. There are no doubt some free/low cost software packages to be found with good enough quality for simple projects. That’s a topic for another day.

So after much digging around, playing with different software to route boards on my CNC machine, I ended up choosing a program called PHCNC.

PhCNC_CAM_largePhCNC_CNC_large

Pictures of the PHCNC software running from http://www.accuratecnc.com/software.html

I have no affiliation with the company that makes this software, other than being a customer. During my research, I found that accuratecnc and another company, LKPF (http://www.lpkfusa.com/Software/ccam.htm) both make CNC machines specifically for isolation routing. I’ve seen both praised for the high quality boards they produce. However when it comes to the software, especially if you want to run it on your own CNC machine, accuratecnc’s PHCNC is by far easier to use. In fact, LKPF’s software won’t even allow you to generate standard g-code for your CNC machine. You’d have to jump through some hoops just to get the software, then jump though some more hoops to be able to use it on your machine.

PHCNC is a little pricey, but not that bad. It’s basically $400 or $500 (for the pro version). You have to attach a dongle to use it. The dongle appears to make the software think one of their machines is connected, even though it’s your own CNC. Actually I’m not sure if it can directly control your CNC machine at all, but rather you’d use your favorite CNC control software (like Mach3 in my case), and load the file that PHCNC produces.

I tried a couple of other programs too, including CopperCAM. At first, CopperCAM seemed great. Simple interface, fairly straightforward approach. But, I soon ran into problems. The biggest one was in loading gerber apertures from gerber files. In short, the board designs might load in, and if the board was very complicated at all, it would more than likely be messed up due to the poor support for the ability to load in custom pad shapes and other features. When I say custom, I’m not even talking fancy. Rectangular pads with rounded corners for instance were problematic. So after trying many options, I finally decided it was worth the investment to get something that would just work. So far, after making a few boards, it’s working pretty well.

AccurateCNC has an interesting link on their site describing the aperture problems. I ran across this early on, and kind of dismissed it for awhile while I tried other software. However I found myself paying more attention to this after much frustration.

http://www.accuratecnc.com/software_tests.html

So what do you get when you make your own board? Well, they’re not “pretty” compared to those nice boards you get from PCB fabs, but they’re functional, and you can have them same day, which is sometimes quite advantageous. In a future article I’ll review a few PCB fab places I’ve used. Some of them are quite affordable if you don’t want to make a big mess with chemicals or have a CNC machine with proper software tools to make your own, or can simply afford to wait. If you plan well, you’ll have plenty of other stuff to work on while waiting impatiently for the UPS truck to show up :P




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