electroplating as a assiting process

Prior to my current position I worked for a electroplater/electrocoater, we never did copper but we did do about a dozen corrosion resistance alloys like tin/zinc and zinc/nickel. So having caught the recent posting of the use of copper electroplating to coat a nozzle I got to thinking.

A low quality conductive polymer could likley be built by simply mixing large amounts of carbon black pigment into an existing thermoplastic. Extude a small amount into a cavity and over to a buse bar and use a progressive fill plating bath. Then when the part is finished turn on the power. The copper would plate out onto the wire slowly at first but as the current began to pass though the copper rather than the plastic the plating rate would increase. Measure the resistance of the wires to determine when to stop.

Also available is electrocoating rather than electroplating, using functionialized plastic rather than metal salts. So in theroy you could extrude the conductive plastic, plate up a wire, switch baths, and then electrocoat on insulation. This would also seal the cut ends of wire to prevent possible short circuits. You also start being able to build things like capacitors.

We would use conductive baskets filled with the raw plating material and attach them to one of the buse bars. You can take plated material and reverse the current flow and strip off the plating fairly easily, so recycling becomes as simple as tossing the wires into the basket that holds the copper supply, moving the basket to the other side of the bath and throwing a switch. That way you even recycle the metal that plated out on the buse bar. When the copper is gone you just toss the conductive plastic into it own recycling area.

Just another idea for the rapidly growing pile.

Mike

The thoughts and ideas expressed in this post do not reflect those of my employer and are intended only as communications between individuals. Any attempts at implement are at your own risk

Edited 1 time(s). Last edit at 09/12/2007 09:34PM by ohiomike.

Have you had success in making polymers or waxes conductive by adding carbon black to them? I used to work for a company that makes artifical hands/limbs ect and we had to paint the wax with silver based paint at great expence. I suggested that they add carbon black to the wax to make it conductive and therefore reduce cost but they never tried it to my knowledge. If the reprap prints wax then recycling is really easy, isn't it!

I think this idea could have a big potential.
In one of my test with catalytic polymerized reins I had the intention to add conductive fillers such as copper or graphite powder. I always doubted that the conduction could be high enough but if we give it this electrolytic treatment afterwards, it could highly improve it.

All we have to do is find the best polymer mix to achieve good metal adhesion.

This sounds like a really good idea, I hope someone can make it work. I've heard about heavy filler loads of metals in plastic to do metal printing/sintering, but this sounds like a good way to print the circuits followed by some plating enhancement. The thing I just thought about was the mention of the buss bar. You need to have conductivity. There are traces that will just go from one hole to another. That means, there will be no end to connect to it. So not to bring up a problem without a solution. How about a conductive brush the rides just above the plating liquid, gently touching the unplated conductive surface as the liquid rises the covered traces get plated. There would be some trickyness to this and maybe require an x and y pass of plating, but just adding to the process dialogue. Any thoughts?

You might have to be careful. If the bus bar is also submerged in the plating solution, it could get plated as well, and that might cause some problems. It might grow in the wrong ways, and end up connecting the wrong things, if possible.

If this is just for circuits, you could try and plate the traces on the bottom side of the board, while somehow applying the current through the bus bar on the top side, out of the way of the liquid. I'm not sure if that's very doable, or even necessary, but it's a thought, and you did ask for thoughts.

On the other hand, if you didn't want to have to flip the board over for that solution, you could have your pcb resting at a tilt. As you slide your bus bar across it, you submerge it slowly. This would allow the bus bar to apply current to a trace, and yet not actually be under the liquid. Unfortunately, you wouldn't get the whole trace plated on one pass, as the bus bar stops applying current to the trace before all of it has been submerged. You would have to alternate the direction of tilt, and keep raising and lowering the plate out of solution, but it would prevent the bus bar from getting plated, which just might be a bad thing.

Again, just thoughts.

Thats kind of what I was trying to explain

if we do get this system setup and working, an easy way would be to work within the parameters of the system and use them to our advantage. if we can print metallic plastic, why not print an extra line (or lines) out away from where we want it electroplated, apply the buss bar there, electroplate everything, then either cut off that excess, or ignore it.

then there is no complicated multi-pass system, and its all stuff that would be relatively simple. it just takes a bit of getting used to thinking about designing within the system instead of trying to come up with a new way of doing it.

One could also utilize the photoelectric effect to print circuit boards. Place a sheet of mildly conductive plastic into the solution, apply a voltage to the sheet that is just under the voltage needed to deposit copper(1.1 volts or so, just as long as it is below 1.4 volts, for copper I think) Then project an image of the circuit you want to print, the added electrons from the photoelectric effect will deposit copper where the light strikes. This of course takes into account that the electrons will not be localized(ie the whole sheet might get plated) but given that the plastic is resistant the distance the created electrons should flow will be dependant on this value. This resistance value will determine how fuzzy the image is. Instead of computing what voltage to set the base plate to, I would just turn the voltage up slowly until copper starts to plate out, then turn the power down, remove and wash the plate with acid to remove this test haze, and reinstall and try projecting the pattern. Ideally this should be done with a laser, but a simple test would be to just project a light on half the sheet. Those are my thoughts, I'll try to test them when I get back to the states.

I am going to try and answer a lot of questions in one post so dont get confused if I seem to jump around.

The reason that they were painting on the circuits rather than using conductive filler is because conductive filler degrades the physical performance of the plastic and because the conductivity of the silver is FAR higher than a plastic/filler blend could ever get to. The only reason that this has potential is because as the copper plates out the conductivity will skyrocket so all that is necessary is to get the process started, and you can use a large current source (an arc welder perhaps) if necessary to get the first layer of copper. And once the wire is formed the poor physical performance of the polymer becomes irrelevant.

Since the plating bath is progressivly filling as the robot indexes up I would simply extrude a line of conductive polymer from the part to the buss bar. Drill holes in the buss bars to give the robot the ability to drop a glob of conductive polymer and make good contact. Keep the part far enough away from the buss bar to make any plating spikes unimportant. Make both buss bars identical and use a removal conductive basket to hold the raw copper. Then every other few runs switch the positions of the buss bars so that the material that plated out on the bar gets used to regenerate the bath. If you switch the bars every run you could just leave the tails attached and remove them after all the copper had been stripped off off.

That would require that all circuits at some point touch the outer wall of the part and that after the part was finished the tails be cut off and the access holes be sealed but its the simplest solution that I can imagine.

Mike

The thoughts and ideas expressed in this post do not reflect those of my employer and are intended only as communications between individuals. Any attempts at implement are at your own risk

Edited 1 time(s). Last edit at 09/12/2007 09:29PM by ohiomike.

That was my point about the conductive brush keeping ahead of the solution, to eliminate machinations needed in the design to accomodate access to inner jumpers having to be run all the way to the buss. That means there is considerable work in designing for production and post processing to eliminate what would otherwise become dangerous shorts. Also, would something like this lead to embedded components. Could you say somehow control consistency to deposit resistive conductor to produce a resistor, nearly adjoining and more highly conductive material to become capacitors, long swirling traces for inductors? Its a long ways from there to semiconductor printing but this makes me think its really a matter of proper materials science with lots of testing of different things for ease/benefit of use.

Alternatively, you could try and keep the solution contained, say in the tip of a tool head. Then you wouldn't have to worry about large tubs of solution, or moving a circuit board up and down. It would probably work like a syringe head, slowly pumping the solution onto the board just where you wanted it. Encircling the syringe would be a suction cup feeding to the pump, drawing off the solution, and preventing leaks. Just outside that would be were the cathode comes into contact with the metal plate/trace. This would prevent the electrode from getting plated itself. If the nozzle could be made to have a small enough area of solution contact, it could even be used to just "draw" the metal on a conductive plate base, effectively allowing any 3d shape to be made via electroplating. If this could be done simply, in a mostly self-contained manner, it could feasibly do just as well as or better than laser sintering for making 3d shapes out of metal. The shape wouldn't have to necessarily be filled with powder, for instance, and could be hollow. I'm not sure how to handle overhangs, unless the tip is so fine that the surface tension of the liquid helps it adhere to the metal you're forming.

Do you think this could be used for applying small amounts of semiconductor? If you could use two anodes, and control how much current went to each, you could probably even dope the result. Just an idea, but it sounds interesting, if it could be done. Probably the best way to apply metals with high melting points, unless the laser can be focused tight enough, with fine enough grains of metal powder.

More thoughts. Rambling and dense ones at that.

I think you're going to have a problem with the surface tension of the liquid. That's how pens work. The liquid will draw out all over the surface. Suction cup? Don't think that's going to work, you can't seal a rough surface and you still need to expose the part that is the conductive bar so I don't see a gain over lowering the board into solution. Laser, those are cool, where'd you get it? I think it was Sebastien that said, loosely quoting.. "Dude.. Laser!"

The words "suction cup" were probably poorly chosen. I was trying to think of the best way to describe the part of the tool head designed to suck off the solution, before it spread too much. It doesn't necessarily have to have a seal, though if you need to absolutely prevent any liquid from getting past it, you could have a cloth border, to soak up any stray liquid. The wikipedia page described using a cloth tipped brush for electroplating. We could try that instead.

One problem with the method I outlined is speed. Terribly slow, I'm afraid.

I think a laser with sintering could be a better choice, as lasers are much faster, more precise, and can do more things, such as etch, cut, and trim. They just cost a lot, in optics for focusing and transport. Fiber optics are good for the last bit, but they still aren't cheap. If we could reprap optics, that would be great. Lasers hands down, at that point. I just saw this method of electroplating as a possibly cheaper method to make circuits and semiconductors. I don't know yet how hard it would be to sinter doped silicon.

Any improvements you can make on the idea, or ways to make the giant vat of solution more viable, are certainly accepted. It just seems that the giant vat would take a lot more parts than just a tool head/pump. It would take the vat itself, and means of moving both the circuit board and the bus bar. Not to mention it would require a bus bar in the first place.

I seem to be specializing in general thoughts.

It'd mean not putting the z-axis motor BELOW the working surface, for one.

I was envisioning it as a final process after removing from the reprap.

Hey, i found this interesting article of exactly this subject, although specifically for zinc plating. i have just read through it diagonally but I think we could extract useful info from it if we just take the time to read it more.. uhh.. horizontally

[www.patentstorm.us]

Hmm, thats a long one, but I was encouraged about the part that stated bright zinc deposition with or without added cyanide. We certainly want to be as safe and green as possible to allow the widest acceptance. Thats because after reading the howto's for plating, they say don't even think about doing this at home. Well if we can find relatively safe methods, we can decide for ourselves. We just don't want to be saddled with toxic leftovers.

Yeah I agree with you. If we have to use cyanide in our electroplating solutions, it will be a disaster at some point.
They use cyanade to improve adhesion and plating quality. Like this they achieve a perfect shiny metallic surface in the end, instead of a uneven, porous one.
In the article above they are actually speaking about ways to make away with it, and one component is N-Methyldiethanolamine, wich is not poisonous and i will be using for my UV-set resins.
I will try and read this article in depht this evening and come back on this.

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Edit: After reading the article more thoroughly...
Well, all that chemistry in the article is quite pointy and way ahead of our actual state of affairs.
first thing to achieve is a conductive polymer, one that is sticky enough to accommodate metallic deposits. To this respect, PE or PP blends will probably not work due to their notorious lack of adhesion capacity.

Edited 1 time(s). Last edit at 06/11/2007 09:04AM by Fernando.

I've been plating things in copper for years at home. Its a non toxic solution of copper sulfate, HCL, and water, heres a guide to mix your own [www.thinktink.com]

Anyways, if you want a nice shiny copper plated object be sure to circulate the fluid to insure a even coating. This is usually done by slow (1-3 in/sec) horizontal motion(reciprocal) of the object to be plated while in the bath. We tried bubbles but the bubbles stuck to the object resulting in porous plating. And remember that the larger the vat, the better. The ph and ion balance is crutial to get that shiny finish, If your vat is too small then the chemistry will change and your finish will look dull or oxidized. But if you don't care bout that then fine, I have plated 1/2 thick copper in a gallon bucket that was still nice and shiny, so a lot can be done in a bucket. Hope all this info helps. Ps, if your copper sulfate crystallizes out onto the bottom, save it, crush it up and stir it back in. If you let your vat sit too long you can get some big crystals(2x2x4in) that are nice and pretty.

Later

The bath I ran was an industrial electrocoating system, and I definitely agree that mixing is HUGELY important. We would use eductors that took the outflow of a pump and slowed it down by entraining large amounts of the surrounding fluid. An eductor is a simple little plastic part that would be ideal for the reprap to print, its basically a megaphone designed to be used in a liquid. With a couple of eductors a simple aquarium pump should be enough to aggitate the size of bath we are talking about. With a couple of values that same pump could serve double duty as the inflow and outflow control for the bath.

To start I imagine that it will be necessary to design parts to allow for use of a simple buse bar, then drill out and plug any point were it touches the outerwall of the part. But honestly I imagine a simple nail or screw driven into the conductive polymer could be used to close the circuit. It might be possible to plate out a wire while the reprap is running, using a print head with an nail or screw attached to plate while the extruder is building another section. But now your talking about a four headed printer, with extruder, support material, conductive polymer extruder, and plating contact. Add a paint nozzle and you could insert very thin layers of insulation, or conductive paint to build capacitors and transformers. If you plate a wire in two sections with a gap in between, then fill that gap with the conductive polymer you have created a resistor, with the resistance determined by the length and depth of the gap.

I could see being able to print a circle of conductive polymer plate up a wire on it, paint with insulation while leaving a contact point and then repeat. It MIGHT be possible at that point to build an eletromagnet, which starts to allow basic dynamoes and eventually motors.

Mike

The thoughts and ideas expressed in this post do not reflect those of my employer and are intended only as communications between individuals. Any attempts at implement are at your own risk

Edited 1 time(s). Last edit at 09/12/2007 09:28PM by ohiomike.