Inkjet PCB printing.

[moonshadow]

I did my first milled PCB board about 25 years ago. So when I recently

decided I had to go over to surface mount, I realised my chances of

being able to mill a trace between the pads of an SOT device ... were

very slim. So again, I decided to have a look at alternative

ways of producing PCB's. Of course, this thinking raised more questions

than answers!. I am specifically wondering if it would be possible to

produce an A5 sized ink jet printer, that could print onto the surface

of the PCB board. Also by changing the ink I wondered if the component

layout could also be printed direct onto the board. My questions are as

follows ....

1. Has anyone done this ?.

2. Some inks are already available that can cope with the rigors of an
etching bath. Does anyone know of any that can also be used in a
piezo-electric print head ?.

3. Since the ink would not be mechanically 'fixed' to the copper by absorption, is there any pre-treatment of the board that would make the printing more durable in the etching bath ?. I am thinking about a coating,
pre-etching, abrasion, pre-heating etc ?.

4. Has anyone any practical experience of cutting Press and Peel film to the actual size required, taping it to a sheet of paper and then passing it through the LASER printer ?. Ie what kind of tape would withstand the heat inside the printer ?.

5. Does anyone know of any low cost OEM inkjet mechanisms ?.

Now for a glimpse of the future, have a look at the following link.

http://www.circuitree.com/CDA/Articl...121582,00.html .

This is about taking the idea a stage further and using an inkjet, printing metalic tracks direct onto an insulating substrata. I WANT one !!!!!!

John K.

[C_Moore]

Hi John,
I have used pressNpeel with great results.The way I did it I drew my layout with pcb express(freedownload).printed it on paper with a laser printer. cut out the layout then printed it on the pressNpeel with a laser printer.cut out the layout and using a house hold iron transfered the layout to the copperclad board. then etched it using sodium persulphate.The stuff is simple to use.Hope this helps. regards Charlie Moore

[moonshadow]

Thanks for the reply Charlie. I don't use a LASER printer normally so when I tried the toner transfer idea I had it done in a print shop down town for £1 a sheet (including the poitive). Press-n- Peel works out to about £1.50 a sheet. I was wondering why so many people were trying to perfect the toner transfer method, when there was so little difference in price .... providing of course that Press-n-Peel was as easy as it sounds.
Printing acid resist ink directly onto the board appealed to me and I am naturally very curious as to why it has not developed into some sort of small hobby type device. For example Maplins are selling a CD/DVD printer at the moment for less than £50 and that is in effect a flatbed, thick material printer. So the technology is possible, providing ferric acid resistance inks are available that will go through a piezo electric print head OK. I have emailed off to several ink manufacturers, some of whom specifically claim to sell acid resistant inks and flushing fluids. Not sure if these are UV cured or not. Thanks again. John K.

PS. We still need Mavericks mill to drill all the holes Hi!

[Richard]

John, I once heard about a guy using a flat bed plotter. He got a normal plotter pen, took out the tip, drilled it, and put in a fine etch-resist marker pen.

Then he secured a piece of copper clad (washed in detergent to remove grease) with tape to the plotter. Apparently, the results where surprisingly good.

You can get second-hand plotter on EBay for about £40.

[Richard]

For example Maplins are selling a CD/DVD printer at the moment

I have one of these, it uses thermal transfer with an ink ribbon. The model I have prints at 200dpi and the newer one 300dpi, which is pretty low res.

It does put a tough, thick layer of ink onto the CD surface however.

[citldave]

For quick prototypes i use a laser onto OHP film and then expose RS photoresist boards always gives excelent results but honestly its been some time since ive done this as ive found the likes of pcbpool and others cheap and quick at giving me prototypes and i dont have to mess with the chemicals. especially as its none PC to dispose of them down the sink now.

[moonshadow]

Thanks for the reply chaps. I only really started thinking about this two days ago when my wife closed up the printer door to make room for her coffee cup. After I extracted half a ream of screwed up paper from it's innards ... it printed out garbage. I had the thought at the time that I wished I could produce PCB's with the same resolution as the garbage Hi!
Milling can cut out pads and traces for DIL sized components, but is cannot produce completed PCB's. By that I mean it cannot print component layout graphics topside. Nor can it print solder resist layouts, spray flux on pads etc.. . So what I had in mind was a device that would do all these things in an automated fashion and quickly. A small milling machine would probably be able to cut at about 10 inches per minute whereas doing all these process's with a printer would finish off a whole board in seconds .... everything except for the holes and they are quickly becoming redundant. So at the moment I am thinking about an A5 sized box of tricks that will accept a stack of blank boards at one end and produce a stack of completed boards at the other end (minus holes, tin plating and etching). Now if flexible drive powered drill head could be mounted on the same assembly as the printhead (or instead of it) then the print mechanism stepper motors could be driven from different software to produce a milling machine type motion for drilling all the holes on a second pass. I am wondering if it could be manufactured for sale at below £200. Just thinking out loud ! John K.

[Tim]

John

An interesting concept. I have seen the output of the LPKF macanical engravers and it superb. There is still milage to be had from the technique.

As an addition to the methods you have listed why not add a flat bed with a UV lazer to raster the image onto the photo resist.

[Richard]

John, take a look as some of the lovely equipment here -

http://www.megauk.com/products.html

[roger]

Hi John,

Ink-jet (piezo) pcb printing has been discussed ad infinitum on

http://groups.yahoo.com/group/Homebrew_PCBs/

You need time, over 7,000 posts, to come to any conclusion, but as I remember, I think the general conclusion was that using positive photoresist with some additional thinners in a piezo head worked well. (the resist was not, of course, uv exposed), only dried.

I have often wondered why a pcb printer of this nature has not been developed, but recently I haven't had the time to explore it.

Maybe we should form a group to develop this since Mavericks mill seems to have disappeared into the ether.

Roger

[roger]

Hi Tim,

The problem with a flat bed laser raster using a laser printer for exposure is that photo resist requires uv light (<400 nm wavelength) while laser printers generally work on red end lasers (around 600 nm).

UV laser diodes are available but still relatively expensive and the optics for uv are different to red end.

Roger

[moonshadow]

Hi Roger.
I have just realised that the PCB forum still exists (there haven't been any posts to it for the last 60 days and I couldn't find it the last time I looked). I had better move this theme over to that list before I get my wrists slapped Hi!. I'll post my reply there. Sorry about that Les. Maybe Les would allow us to discuss this subject there ?.

John.

[keyscoob]

Further to Richard's post above. I have used PCB making equipment from Mega for a few years now and am very pleased with the results. Their etching tank has served me well so far.

Carl

[Phil]

Originally Posted by moonshadow

I had better move this theme over to that list before I get my wrists slapped.

I can move this whole thread there if you want me to

[moonshadow]

OK Sir, Thank you.

[fullspeceng]

If you're looking to make small double sided pcbs with minimal effort, checkout our direct inkjet pcb printing kit: www.fullspectrumengineering.com/tutorial.html

[benjaminh]

It would be interesting to see a close up of a finished board.......

[Bob Walsh]

You need to use “inkjet” transparency film, not plain acetate. The difference is tiny fibers embedded into the acetate give the ink something to adhere to. also be sure to give PLENTY of time for the ink to dry before touching or even moving the transparency much. I find that 30 min. works good, but more or less might be required depending on ambient temperature and humidity.



http://www.techstore.ie/Design-Print

[Alex Chadiak]

The results were stunning. The lines were sharper, the holes clearer, the pads better defined. What a difference it makes going from a 600 dpi laser to a 4800(?) dpi inkjet. So, I felt it worth the risk, and decided to run my exposure test with the inkjet. Using some inkjet transparencies (they’re kinda coated with some type of fiber?), I printed my patterns. I exposed my board, and then developed it… the results were WOW! Of course, I messed up a few things with this first run, mostly I let the light cook for too long.

[wastrix]

Originally Posted by Alex Chadiak

Of course, I messed up a few things with this first run, mostly I let the light cook for too long.

Well that is a minor problem with inkjets. The ink is often not dense enough (even at 4800dpi) to create a perfect opaque black on the transparency, so it is easier to overexpose.

Theoretically if you had a perfect black, you could never overexpose a board. Unfortunately this is not possible with either type of printer

[moonshadow]

On many printers the registration is accurate enough to pass the transparency through the printer more than once (allowing time for the ink to dry properly between prints). If there are inaccuracies they show up on the pad holes getting smaller and slightly fuzzy edge to tracks under a magnifying glass. Since most of my problems in the past have been due to the black not being dense enough, I usually run two sheets through the printer and then make a sandwich of them, and that seems to work every time. Most of my stuff is DIL and not that critical.

Using a sandwich of two transparent sheets also gets rid of the micro crazing of the ink. The tracks look OK to the naked eye but under a glass all of the black area's have micro crazing which can leave one with an open circuit track. It often shows up first, when trying to solder, as the crazing stops normal solder flow on the pads. It is one of the reasons I asked for a USB microscope for Christmas Hi!.

Also I have been working towards screen printing pads and track directly onto the copper. I still have to make up a safe light and an exposure light before I can do the first experiments, but process can be seen at ....

http://homepage.ntlworld.com/moonsha...n_printing.htm

[Maverick]

Milling can cut out pads and traces for DIL sized components, but is cannot produce completed PCB's.

Not true , I can produce PCB's on my LPKF just fine 0.1mm track widths QFN, TQFP100 infact pretty much anything SMT or otherwise with. Double sided and through hole plates with 0.3mm vias.

Do some research b4 ya comment

[moonshadow]

Maybe you should read what I said before jumping in with both feet ....

"Milling can cut out pads and traces for DIL sized components, but is cannot produce completed PCB's. By that I mean it cannot print component layout graphics topside. Nor can it print solder resist layouts, spray flux on pads etc.."

[Maverick]

True that it can't but it read like you were unable to do fine PCB work , which is far from the truth LPKF I own can do any layout I throw at it down to tiny 5*5mm 40pin QFN.

As far as solder resist and solder Ident , you are correct , but then again these are real easy to screen print on. As is solder paste with a stencil which I use a Co2 laser to create.

Masking ink is quite thick I doubt very much that you could inkjet print it easily if at all. Solder paste would be impossible to print as it is a suspension of tiny balls of solder in a sticky flux.

Maybe we should form a group to develop this since Mavericks mill seems to have disappeared into the ether.

I did finish the mill and got reasonable results , but to be honest to get the results you need for fine SMT work , it simply isnt cost effective unless you can get a lot of aluminium milling work done cheap. Another stalling point for fine work is that you really need a spindle with zero bearing slogger and a speed of at least 60,000rpm , these alone are really expensive.

My homebrew mill is on the deck gathering dust , I may rebuilt it at some point for heavier work. It is doable as I proved but you really need a metal frame and bed for the accuracy and a HS spindle (with a floating Z which i stupidly didn't implement). Unfortunatley I dont have access to that sort of milling equipment and to get it done as a one off by an engineering shop was going to cost as much as a pro system . So I cut my losses and got the S62