Hi guys
I felt my contributions have been a bit lacking recently and have permission from Jake to post pics and go through the fabrication process I'm using to make the saber PCBs.
I hope it will dispel some of myths and mystery about making PCBs at home and encourage others to have a go as its really not that difficult (as long as health and safety precautions are taken seriously, it's actually a fun and highly intersting process).
Part one is mostly descriptive, the exiting stuff will happen in part two so please bear with me.
----Part One----
I use a common home brew technique called toner transfer. It was discovered a few years ago that laser (and to a lesser degree ink jet) toner inks are resistant to many forms of etching mediums. Not all printers are made the same though so if you decide you might like to try your hand at etching after reading this, avoid Brother models as the ink for those have a higher melting point and results are very hit and miss. I use a 1200dpi Samsung mono tone laser jet printer and it's worked like a charm so far.
To make use of the ink as a resist, the circuit image is first checked to make sure it is true black and white (and corrected if not) then the image is mirrored in readiness for printing.
The next step is to make a test print with the toner levels set to minimum. To avoid miss printing the proper run, a mark is made somewhere on the top of the sheet for correct orientation later. The test print gives a print area "hot spot" and a piece of gloss photo paper is cut slightly larger than the print area and secured in place with sticky notes for easy removal.
Once secured, it's put back in the loading tray in the correct orientation and the toner levels are set to maximum. You need as much ink as you can get your printer to lay down as a resist layer, adjusting the printers altitude setting to high will also help to increase the ink density, though finding the settings for this can be elusive:
A piece of copper clad board is then roughly cut so it's slightly larger than the piece of gloss paper, this ensures none of the print is placed "off board" by accident. It's then buffed with 0000 grade wire wool along both axis (length, then width and back to length for a final pass) and cleaned with acetone and isopropyl alcahol to ensure there is no dirt, oils or residues left on the copper surface.
The easiest way to check how clean the copper is after wiping it down is the water test. The board should be able to hold water for a minimum of 10 seconds as enough oil residue to stop the toner bonding to the copper will part the water.
Once cleaned and checked, the board is heated in increments over a 20min period till it reaches about 30~40°C:
The print is then carefully aligned and placed face down (one end first) onto the heated copper surface and fed through the laminater about 4~5 times and the next part is to feed it through a Hot Roll laminator set to max temp (I use a GBC HotSeal H312). This allows for far fewer passes as the board is already warmed and doesn't draw heat away from the ink and rollers:
(I modified my laminator and cut a section out of the main housing to gain better access to the rollers)
Note: Externally heated rollers are not recommended for this type of work as they suffer from hot spots and can't the high temperatures where the pressure is applied due to the fact that the feed rate is so slow and the rollers start to cool down as they turn away from the heat source.
**
Normally the board and paper would then be cooled under cold running water. Once cold it would go in a receptical cintaining warm water to soften the paper for easy removal.
That bit is messy and more brands than not will also leave the gloss layer on the board as well. It does come off by rubbing, but this comes with a high risk of accidentally knocking some of the ink off while your at it and vias have a nasty habit of protecting the gloss layer inside them so need fingernails or a relatively pointy but blunt tool to get them out.
I count myself to be very lucky in this respect as I don't have to do any of that nonsense. I discovered by accident that the local supermarket brand of gloss paper I use peals off easily and cleanly while the board is still hot leaving the ink and a very fine layer of paper behind:
Ink that is still attached to the photo paper is an indication of possible oils still present on the copper, or can be a caused by using under temperaturesn as in this case as I only passed it through the laminator three times and it could have done with at least one more.
Your kind of committed once peeling has begun, so I use an etch resist pen to fill in any holes that do appear. If thin tracks are broken, I use the acetone to clean off all the ink and start again with a fresh print as etch resist pens don't come with fine tips, let alone one that can deal with the .3mm tracks used on the saber boards.
Well, that's it for the moment. I hope it was informative and if there are any questions regarding any part of the process, please feel free to ask.