EDM Applied to make PCB's

I believe kerosene is a more commonly used fluid.

Hmmm, 2 kv sparks plus kerosene ???

I had a PCB made with money. Money is a widely used substance that allows one to transfer onerous tasks over to someone specialized in said task. Money has no particular storage requirements. I mean, I like steak, but it wouldn't occur to me to get my own cow.

Some friends of mine have their own cows. And pigs, and other animals. They haven't had to pay store prices for meat in years. They're called "farmers". Without them, you wouldn't be able to get meat either.

It takes all types. Some of us are DIY, some of us are $$$, some of us are both. Can't you just accept that different people like doing different things?

and

Hmmm, 2 kv sparks plus kerosene ???

Yes I know...1kW energy + fuel=more danger....Isn't kerosene similiar to jet fuel.. This could spark some ridicule...how about zapping in liquid propane. ;) I do recall there are other liquids used for EDM.

I don't think it's a very good fit.

EDM tends to come in two varieties. One is very localized, either point-type, or a wire "saw" which cuts all the way through something. Covering a whole pcb with a point type operation would seem rather slow, but I suppose might be an option for designs where you can leave most of the copper and simply use thin outlines of removal to isolate pads.

The other is a larger area operation, but requires a shaped electrode - essentially, making a die. Usually this is a quite messing operation of machining a block of graphite.

When photoresist is not used, the preferred choices in practice seem to be either a specialized milling cutter, or a laser system. My employer uses both to make small geomotery-critical microwave boards, generally on teflon substrate.

Good for them. Ask them how much effort and machinery is required if all you want is *one* filet mignon. I mean I like wearing T-shirts, it would never occur to me to open my own sweatshop. Also ask them if they sell the rest of their meat? Wouldn't your comparison imply that if you make your own PCBs you should sell some if it's comparable to the farmer's case? The farmer is just *gasp* like a PCB shop.

Exactly, they're called farmers, and god bless them for we are all parasites on them in the end...

Farmers call themselves farmers, I'd bet. They don't call themselves "gourmets" and then go around asking on gourmet groups about how to make your own steak, am I right?

Just like a farmer grows meat, a PCB shop makes PCBs. It's really quite simple, otherwise they wouldn't call themselves a PCB shop.

My problem is that this is an electronics group, and we have people wasting time and energy on something that's been done for 50+ years and is easily accessible with pocket money today, instead of building phase-locked oscillators or PIC based LED flashers. Building my own PCBs is a phase I went through in high-school, and then quickly abandonned as my projects became more than 1 IC with 1 resistor. No one asks how to make their own resistors out of nichrome wire...

The O.P. might take this idea to one of these Yahoo discussion groups:

I can imagine this technology becoming an environmentally friendly way to make boards, if sufficiently developed.

I made a couple of test boards last weekend - surface mount, single sided+ground, couple of square inches each. Took about 1/2 hour for the pair of them. In fact most of that was waiting for things to happen, so probably 10 minutes actual "labour". It would have taken me longer than that to prepare the gerbers and go through the order process. Then I would *still* have to wait 2 weeks and pay >$60.

I would always out-source actual production, and, these days, prototypes much more complicated than the above. But I find manual production still has a place.

snip

Probably because it's pretty easy to do. I do still make the odd load resistor from Nichrome wire, Why? because it's incredibly easy, cheap and fast. I could make another resistor in the time taken to fill out a web-based order form. It costs me virtually nothing in materials. Compare that with waiting 1-2-3 days, the cost of the resistor and "Freight and handling ", that jolly convenient excuse to pad your bill a little.

But going back to PCBs, there's a time and place for everything, and I don't really understand why there's a problem with that. Occasionally I want a new rev of a board this morning, or today at the latest. What PCB house can do that ? And while they all produce high quality PCBs, I have become a little cynical about their advertising and promises about delivery. Things like:

"Aha, day 1 only counts if you have the design here by 0730, 0800 is far too late"

"Ohh, the UPS man missed us today for some reason, that's not our fault that it adds one day"

There's a description of exactly such an effort on the last group mentioned, with decent results, IIRC. Raster-scan, EDM, zap, zap, zap!

Best, James Arthur

Most printed wiring boards are made by chemical etching or by ECM (electro-chemical machining), using an electrolyte that dissolves the copper. This is relatively fast, and the 'hazardous' material is only the copper itself (the etchants are much more benign than the copper is, chemically). Simple etching leaves the copper dissolved in the solution, ECM can plate the copper out of the solution (good for recycling).

The etching or ECM works straight from a printed-on resist coating. EDM won't. You'll have to raster-scan the board to do the work, just like the mini-mill machines do. And, we used graphite, copper, or tungsten electrodes for EDM (they wear down slowest); so we would predict that copper is going to be a very slow material to machine with EDM techniques. The thermal conductivity makes lots of the heat of the spark dissipate instead of removing material, and the dissipated heat IN THE WORKPIECE will be a limit on cutting speed (turn the current up, you burn the board; turn it down, you cut real slow).

Some exotic boards are made in porcelain-on-steel, with additive (electroplated) copper. You could make a steel/porcelain/steel board that would be strong, mechanically stable, and the steel would ECM just fine. Weld on your components, and there ya go: ROHS compliant lead-free printed circuits.

I get up at 6am with an idea; prototype by 8:30; board layout by 10:00; working unit before noon; have a nice lunch; wonder if Law and Order reruns still start at 2pm?

My workload averages about 10 hours/month lately. So I have more 'free time' than 'free money'.

Luhan

That's easy for the idle rich to say.

We didn't all inherit billion-dollar estates, and some of us don't even have a sugardaddy! Imagine that, if you can.

Thanks, Rich

You should understand the hobbyist approach. Maybe I find an interesting circuit on a website and because I want to use these free samples I have already one year, decide to make it. It is just a small circuit, some audio preamp for a small electret mike to measure frequency response of speakers, a booster for operating white LEDs on a single cell, a PWM to drive a small motor, whatever.

I then order the parts, of course in through-hole, because I can breadboard them. Digikey has too high prices and shipping costs. I also have a great stock of salvaged parts to reuse, so the order is really small and cheap. I do not really trust those simulators and I also do not know so well how to operate the prog. In the meantime I programm the PIC, and after some trouble because the website listing is for the 16F84, I manage to programm it. Now all the parts are there and I plug them into the breadboard. The PIC still has to be reprogrammed, because I inverted the outputs and some minor glitches, but the rest of the hardware works. I will try to tweak a few values, seems a bit sensitive to EMC when I move my hand close, but finally the board can be made. I just paint it with that etch resistant marker on the cleaned copper. The etching is done in 15 min. after some setup time of course. The drilling is a bit messy, broke that expensive tungsten drill, because it was difficult to center and the stand is giving away. But anyway, now the soldering iron is already hot. Lets hope that pot has some flexible leads, the holes are a bit off... But it is all my own work, well maybe not the schematic, but at least the board. Have to show it to my GF!