Printing PCBs

[eeka chu]

I was staring at an old inkjet printer recently and wondering if perhaps I could convert it to print PCBs for me.

There are two things getting in the way at the moment as I see it.

Firstly, PCBs obviously don't bend, so the printing rail would need pulling out and the paper feed translating into a horizontal feed of the print rail across the board or the pcb under the rail.

Secondly, regular inkjet ink is water soluble, so that'd need changing to something solvent based and more permanent.

Just seems like an interesting idea to convert something destined for the skip to something that could make the process a lot easier. The resolution should mean that pretty fine tracks could be achieved, probably finer than you can etch at home.

A final worry might be that the jets spray droplets that are designed to blot out on paper to give a smooth look. That might need some tweaking when printing onto copper to avoid pitting in the masked areas but that could also be solved as part of the ink step if you need to mix your own.

It'd be better than going for a plotter since plotters only do lines.

[richie00boy]

If you can do it I'll have one. However, I suspect the fact that industry hasn't done it would indicate that it's quite a challenge.

Then again maybe you should just get a plotter from a skip, and change the pen

[markiemrboo]

It actually has already been done with an Epson InkJet printer!

http://techref.massmind.org/techref/...kjetresist.htm

[eeka chu]

KICKASS! This is precisely what I was thinking of! I was even looking at an epson while I was thinking about it. Time to get busy.

[FastEddy]

Hey, between Japan and the UK, you guys are going to rule the world ... again!

What about printing (from other printer types) some sort of transparent mask to do the intermediate steps like printing on clear plastic (vinyl or whatever) then use that as a mask ??

Now we need to make those vinyl sign cutters (or those flat feed plotters) to do a "vertical mill" job on PCBs ... No chemicals at all? Would this be more environmetally friendly?

Speaking of which, anyone have favored links to these NCR / CNC vertical cutters / mills for PCB prototype mfger? ... maybe like this DIY mill: http://cq.cx/pcb-router.pl ... or ... http://www.pathcom.com/~vhchan/cnc/cnc.html ... but I suppose this is a topic for another thread.

[eeka chu]

Printing clear masks is really easy if you have a laser printer, and a few people do go that way and expose photosensitive boards.

Another options is to use a Press and Peel type transfer method. Laser print onto transfer paper and then iron it onto the board.

I've used Press and Peel quite a lot. I can only offer your my word as a fellow tweaker that I experimented with a lot of variables, from roughly prepared boards all the way through to polishing the copper and cleaning it with acetone and IPA. I was unable to find any trick to getting the PnP to stick properly. One or two transfers came out nearly perfectly. Some needed marker penning back into order. Others just didn't stick at all. And the stuff isn't cheap.

Photosensitive boards would probably give a better result, but then you have to think about exposure and washing off exposed layers.

CNC routing is also another option people already use. I don't even know how much this is used in industry anymore since other methods can better it. It's an option, but unless you already have a high speed router (e.g. you've DIY'ed a CNC dremel router as a practice / wood / plastic machine) or have access to something similar (e.g. you work in a school with one), it's probably not worth bothering with. I believe there are still companies selling board prototyping routers for tens of thousands, but I'd definitly question their real worth and whether or not the company producing them is just not keeping up. Lasers are used sometimes. Again, super expensive and not 100% necessary.

The beauty of the printer method is that printers are now only a few pounds second hand, and it'd be a one step method. Load the board, click print... etch. You could literally stick all your PCB stuff on the same desk as your computer and have a beautifully accurate prototype done in minutes without messing around.

[FastEddy]

... mmm ... yes, all you say is true and you are correct about the end result. Router cutting also has a registry problem with double sided boards that may be dramatically reduced by you print method ... it can be quite hard to beat the quality / good tolerance from even a 300 dot per inch printer = ink jets now being better than 600 dpi. Do you have a way to register the startup feed for double sided printed boards ... or is this a problem ?

(I do see occasional single sided prototypes using the vertical milling method from Taiwan "one off" houses, but can't remember seeing any double sided ... yet.)

[radtech]

Originally posted by eeka chu
It'd be better than going for a plotter since plotters only do lines.

Many moons ago when I worked for a little computer company one of the things we did was design circuit boards, the finished designs were drawn on plastic film (mylar IIRC) with a plotter. We did double sided boards with solder mask and artwork, I don't think there was much the plotter couldn't handle.
The one problem I can see is that the resolution was limited by the pen width, so we plotted them much larger than 1:1, and they were shrunk down by the board manufacturer. To do direct to copper plotting you'd need a pen at least as thin as your thinnest trace.

[FastEddy]

" ... Many moons ago ... the finished designs were drawn on plastic film (mylar IIRC) with a plotter. ... much larger than 1:1, and they were shrunk down by the board manufacturer. ..."

Yes! This was SOP many moons ago ... Infact this was the methodology for making early integrated circuit chip masks as well ... many, many moons ago. The whole process of design to plotter to mask to film to size reduction to chemical process (or electron beam) was originally invented & developed by Dr. Ramo (the R in TRW = http://en.wikipedia.org/wiki/Simon_Ramo ) ... he being quite the home brew DIY type and amateur photographer (and a real nice guy according to my Dad.)

[eeka chu]

Originally posted by FastEddy
Do you have a way to register the startup feed for double sided printed boards ... or is this a problem ?

You're right about the resolution. A lot of the other hacked printers I've seen recently have been quite modern ones, which have resolutions measured in thousands of DPI.

As I suspected, the issue is not so much how thin they can print but how carefully the DIYer can etch them. The thinnest lines the printers can do are ruined by standard etching. One of the DIYers is using an old, beaten up spray etching unit.

Double sided boards will always be a problem because you need to get it back into some know position when it's flipped for the control system to be able to line up the two sides, as you've figured.

The method at the moment seems to just be to use an L shape to 'home' the board and same tape I think. Seems to be working fine for double sided work.

If you wanted to get precision on it, you could CNC out a clamp to know dimensions that would put both sides of the board at a known offset when flipped.

With a bit of care, you could probably cut a clamp by eye. Tracks on modern boards may be small, but they're definitly visible and that means you can align them.

An old fridge pump would be great for a vacuum hold down.

Originally posted by radtech

We did double sided boards with solder mask and artwork, I don't think there was much the plotter couldn't handle.

The strange thing is, the pen plotters I've seen haven't been very cheap. I've actually found modern hi-res printers that are cheaper than the old plotter model we had in secondary school.