PCB etching and lasers

[Hank Hill]

Joe,

If I were a smarter man, I'd do exactly what you're suggesting. It's spot on the right way for a low volume hobbyist to operate. I could farm out work for years before I approached the cost of a machine purchase. However, I have a desire for convenience and control.

I'm the type of person that try's to justify each time I spend any quantity of money. Therefore, I can talk myself into a one time machine purchase and then be able to engrave and vector cut all I want, where I would be wasting time trying to justify every time I sent a piece out for work. I even have a couple of local contacts (one which will probably read this) that would probably be glad to take my money to farm out a job here and there. I realize it is not a rational thinking process at all but I do like my toys.

My plans consist mostly of cutting and engraving wood, acrylic, and preparation of PCB prototypes. Everything from signing my turning projects to testing my latest circuit design. It's more the less a tool to aid my love of both woodworking and electrical engineering.

Thanks for your tips!

[Michael Hunter]

and preparation of PCB prototypes.

A standard CO2 laser is not much help with PCBs - it won't touch the copper and won't cut the base material (FRP or phenolic paper) well (if at all) either.
Some people have reported success using their lasers to cut patterns in self-adhesive film to make etching masks, but I doubt that would be reliable for thin PCB traces.

Making smart boxes and front panels for the completed PCBs is another matter - go for it!

[Hank Hill]

A standard CO2 laser is not much help with PCBs - it won't touch the copper and won't cut the base material (FRP or phenolic paper) well (if at all) either.
Some people have reported success using their lasers to cut patterns in self-adhesive film to make etching masks, but I doubt that would be reliable for thin PCB traces.
The process is called laser resist ablation and is slightly different than what you describe. You take a copper clad board, paint the surface, and then use a laser to remove the paint in preparation for acid etching. It works quite well actually if you raster from bottom up, assuming that exhaust is on the topside. There's always more than one way to skin a cat.

[Rodne Gold]

There is an issue doing it that way , and that is no matter how you ablate , there is always a residue on the copper surface and you need a method to clean it off if you want a decent etch. You can use a toothbrush with mild abraisive household cream cleaner to do so , and hopefully you dont remove paint along with residue. I do tons of etching using my lasers.

[Hank Hill]

There is no easy method for PCB etching from my experience but the advice I've been given already for cleaning up the splatter is to use some of the acidic based cleaners like Tarn-X, Zap, Restore4, etc. to avoid scrubbing. There's also the option of using black acrylic based lacquer. Perhaps you've already tried some of this too then Rodne. I still think ablated etching sounds more convenient than photomasking with transparent film or heat-transfers.

There's some neat mods out there to modify ink jet printers too but the quality of the etch tends to be poor. I've been farming out my PCB work until now but having a laser will give me the excuse to get deal with the etching myself. I don't look forward to the fun with hydrofluoric acid though.

[Joe Hillmann]

Now I am just being nosy, what are the PCB's for?

[Richard Rumancik]

. . . . I've been farming out my PCB work until now but having a laser will give me the excuse to get deal with the etching myself. I don't look forward to the fun with hydrofluoric acid though.

What do you plan to use the hydrofluoric acid for? I have never seen hydrofluoric acid in relation to PCB etching. It is sometimes used for glass etching. There are probably many safer options to use for etching copper.

[matthew knott]

hydrofluoric acid !!!! not sure you need that for pcb etching, its dangerous stuff, I have always used ferric chloride, works a treat, plus a proper etching tank with heater and pump make a huge difference in the results. Look on ebay, find them cheap. Ive always used photoetch as i probably still gives the best results (what pro pcb companies use). A uv light box is also cheap! But dont let any of that put you of buying a laser, have fun with it, i can etch pcbs directly with my laser, just cant drill the holes so always do surface mount.

[Rodne Gold]

The residue does need some mechanical abraision , even acidic cleaners like phosphoric acid etc will not remove it. You might have issues with extremely thin tracks or very fine detail..but you might have the same issues when etching with a paint resist. The secret to avoid undercutting or resist lifting is to have the item in the etchant for as short a time as possible.
Hydrofluoric acid is a no no - it is extremely dangerous and getting any on you is very bad news.

Heated ferric is the way to go , use an aquarium heater to get it to just under 40c or use a warm water bath to do the same , spray it on if possible , and use what is called an Edinburgh Etch formulation (added citric acid)
This will reduce etch times to sometimes 1/10th of using cold ferric and will allow the resist to last.
Edinburgh Etch...see this
http://www.lawrence.co.uk/acatalog/etch.pdf
Lots of stuff can act as a resist , we have used permanent marker pens (sharpies/khoki) , lettraset , wax , pitch , vinyl etc,

[Chuck Stone]

This one can print out circuit boards
http://www.fujifilmusa.com/products/industrial_inkjet_printheads/deposition-products/dmp-2800/index.html#overview