Step 11: Notes on Etching
This is a section that I didn't think I would need to write seeing as etching is usually the easy part of the process of PCB making. However I have run into some issues that I think people should know about so that they can avoid them and make this a smoother project and better PCBs.
First, everyone should know is that if you go this route you need to use ferric chloride to etch the boards. I know it's nasty for the environment and a lot of people are trying not to use it, but the Mis Pro yellow ink will only work with ferric chloride as far as I know. You may ask how I figured this out and some of the images will show you how. I tried to etch my first set of boards in a mixture of hydrochloric acid and hydrogen peroxide, but the etching solution ate right through the Mis Pro ink and I ended up with those nice green boards of junk (oxidized copper) when I got frustrated and washed them off with water. Ferric chloride however does not eat away the Mis Pro ink and the etching will work as expected provided you follow the next suggestion.
Second, the thickness of the copper layer on your copper clad board is somewhat important. In the past I've used the old permanent marker drawing method and the toner transfer method of PCB etching on some copper clad that had a 2 ounce per square foot copper layer. This worked fine in the past as the permanent marker ink and the toner are a bit more robust and can withstand a longer etching process. The Mis Pro yellow ink however in my experience cannot withstand that same duration. This makes sense seeing as it wasn't necessarily designed for this purpose. The solution however is quite easy. If you choose a copper clad board with a thinner copper layer of 1 ounce per square foot the Mis Pro ink will survive the shorter etching process and give you a better PCB in the end. (If you're looking to buy PCB material check out eBay as it's a great source for bulk material at a good price. I buy from an eBay store run by the user abcfab and have gotten some good deals on some nice PCB material. The nice thing too is that you can contact him if you want a specific material (size, copper thickness, # of boards, etc.) and he'll work with you to get an order going.)
Lastly, my "Trace and Pad Test Board" was poorly designed. Yes that's a shot at myself, but I thought it was worth admitting. I realized during the etching process that there is way too much copper on that board that needs to be etched away. As such I thought about redesigning it with less open space, but then decided to stop trying to etch a nonuseable test board because I didn't want to waste more ferric chloride when I knew the process was working already. Also the Ethernet Arduino serves as much a better measure of printing and etching with this new printer modification as it will be a functional board that I can solder parts to and test traces on.
I know that those may seem like somewhat stupid or strict requirements, but they're things that worked for me and I figured I'd relay them to everyone. If you come out with results that aren't quite perfect just play with your printer settings and heat time as once I got those right things started to work a whole lot better and got some really nice results and a PCB which is ready for tinning and parts.
First, everyone should know is that if you go this route you need to use ferric chloride to etch the boards. I know it's nasty for the environment and a lot of people are trying not to use it, but the Mis Pro yellow ink will only work with ferric chloride as far as I know. You may ask how I figured this out and some of the images will show you how. I tried to etch my first set of boards in a mixture of hydrochloric acid and hydrogen peroxide, but the etching solution ate right through the Mis Pro ink and I ended up with those nice green boards of junk (oxidized copper) when I got frustrated and washed them off with water. Ferric chloride however does not eat away the Mis Pro ink and the etching will work as expected provided you follow the next suggestion.
Second, the thickness of the copper layer on your copper clad board is somewhat important. In the past I've used the old permanent marker drawing method and the toner transfer method of PCB etching on some copper clad that had a 2 ounce per square foot copper layer. This worked fine in the past as the permanent marker ink and the toner are a bit more robust and can withstand a longer etching process. The Mis Pro yellow ink however in my experience cannot withstand that same duration. This makes sense seeing as it wasn't necessarily designed for this purpose. The solution however is quite easy. If you choose a copper clad board with a thinner copper layer of 1 ounce per square foot the Mis Pro ink will survive the shorter etching process and give you a better PCB in the end. (If you're looking to buy PCB material check out eBay as it's a great source for bulk material at a good price. I buy from an eBay store run by the user abcfab and have gotten some good deals on some nice PCB material. The nice thing too is that you can contact him if you want a specific material (size, copper thickness, # of boards, etc.) and he'll work with you to get an order going.)
Lastly, my "Trace and Pad Test Board" was poorly designed. Yes that's a shot at myself, but I thought it was worth admitting. I realized during the etching process that there is way too much copper on that board that needs to be etched away. As such I thought about redesigning it with less open space, but then decided to stop trying to etch a nonuseable test board because I didn't want to waste more ferric chloride when I knew the process was working already. Also the Ethernet Arduino serves as much a better measure of printing and etching with this new printer modification as it will be a functional board that I can solder parts to and test traces on.
I know that those may seem like somewhat stupid or strict requirements, but they're things that worked for me and I figured I'd relay them to everyone. If you come out with results that aren't quite perfect just play with your printer settings and heat time as once I got those right things started to work a whole lot better and got some really nice results and a PCB which is ready for tinning and parts.
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The paper path in most laser printers is a sideways U. That means the paper has to bend around the drum and rollers, a normal PCB won't.
Even if you could get a laser printer with a straight path the PCB is too thick and you would need to modify the actual drum/toner assembly and the fuser assembly. Not easy at all.
Lastly the transfer of toner to paper relies on a static charge given to the paper to attract the toner. I don't think the conductive copper will hold the charge well enough, if at all.
The longer answer is it would depend on the construction of the printer and how easily you could "lift" it. Factor into that the different printhead system and whatever other mechanisms a laser printer might have and it could complicate the build. I don't really have access to a "junk" laser printer so I haven't been able to test this idea out. I'd need to take it apart and look at the specific printer to decide how to go about modifying it.
If you do decide to try it and are successful or find some helpful things out make sure to let me know as I would like to try that in the future.
1)Este proyecto en particular no tiene desperdicio ya que enseña muchas cosas interesantes pero creo que el producto final (PCB) no es del todo bueno, sobre todo en la terminación y a la hora de sumergirlo en cualquiera de los líquidos elegidos, pueda quedar con faltantes de cobre en lugares críticos de soldadura de componentes.Para mi todavía no hay nada mejor que un circuito impreso por una laser (conseguí una vieja Laserjet M400 por muy pocos $ y su rendimiento es maravilloso!!)
2)Cuando uno piensa que el percloruro férrico es nocivo para el medio ambiente e intenta otros medios, hay que pensar que tan peligrosas son las alternativas.El ácido clorhídrico, el muriático así como el sulfúrico o el nítrico (generalmente utilizados para hacer el "aguafuerte" que utilizan los joyeros y artesanos para distinto tipo de metales) son mucho más peligrosos que el mismísimo percloruro, por lo que muy a mi pesar lo sigo utilizando y aconsejo por todo concepto.(Todavía no se inventó líquido alguno que podamos utilizar y luego poder tirar por la cañería sin tener remordimientos...)
3)Por último: entré en tu sitio web y pude ver por las fotos que tu caja de herramientas está "asquerosamente" ordenada!! Nunca pude tener ese orden en la mía,aunque puedo encontrar cualquier cosa que necesite(siempre y cuando cuente con el tiempo suficiente)
Muchas Gracias por compartir tu proyecto con el resto de nosotros!
(Por favor, traducir pues mi inglés es muy malo)
***translation begins***
Generally I don't use to criticize any project because I consider it to be rude. Om the other hand I like to consider new ideas and this particular one looks fantastic to me because it "opens your mind" about every thing you can modify (recycle) and give a second chance to thing that usually would end up in the thrash.
1)This particular project is wasteless (**stands for "very usefull" or "excellent"), because teaches you interesting things but the final product (PCB) is not all that good, specially the finishing and when submerged in any of the suggested liquids, it can result on missing copper on critic places for soldering. There is nothing better yet than a laser printed circuit (I found a old Laserjet M400 for a few $ and its performace is wonderfull!!)
2)When you think about the ferric chloride is noxious for the enviroment and try other ways, you have to think about how dangerous the alternatives are. The chlorhidric acid, the "muriatic" (**this stands for an aqueous solution of sulfuric acid), the sulfuric or the nitric (generally used to make the "strongwater" used by jewelers and artisans for different metals) are way more dangerous that the ferric chloride, that's why although beeing sorry I keep using it and adviceing the use of it (it haves not been invented any liquid that we can use and throw away thorugh the sewer with no remorse...)
3)For last: I've been on your website and I have seen by pictures that your tooling box is "disgustingly" (**this stands for amazingly, it's an irony ;) ) organized!!! I've never been able to keep mine in that kind of organization, although I can always find what I'm looking for (if I have time enough)
Thank you very much for sharing your project with us all!
(please, translate because my english is too bad)
***End of translation***
The acid doesn't do much, except supply a source af Chlorine when the chemistri\y is refreshed by bubbeling Oxygen (Room Air works). This solution can be used forever, it just gradually grows in volume over time. Any tthoughts on using the inkjet printed board with this chemistry?
Perhaps curing the board/ink in an over set to the appropriate temprature for the the correct length of time would solve the pinhole problem.
We used a heat tunnel, which is basically an over with holes in each end and a conveyer belt.
Either way, figure that might help others understand what you meant.
Good comparison though.
Quiznos Subs ovens are similar too.
What's the best looking card you have made so far?
Are there other inks that could be used?
What if a wax ribbon printer (or other transfer type printers) was used... resolution high enough?
There have been a lot of ink suggestions I've seen and I'm trying to look into the availability of some of them for later if I can't get the results I'm hoping for with this ink.
Perhaps you could have an electronic heater below the moving plate, so you'll warm it just enough while printing and just where you are currently printing? Easier to adjust as well instead of the heat gun.
It's perhaps possible to make a micro-etch before printing, which means you etch it very little so you'll get an even and matte surface to print on.
You could glue a support for one corner on the metal plate, so you always find a correct "zero point". Could be as simple as epoxy a piece of pcb with an internal 90 degree angle (L-shape). Then you don't have to use so much scotch tape.
If you find some other colored inks you could also print solder mask (green or other color) and silk screen print (white).
Great work, I hope we'll see more of this.
The key to the TTF method is the second step of adding the green TRF paper on top of the toner.
Will the TRF stick to your resist ink? If it will, that should greatly improve the quality of the traces.
The other thing TRF does is make the resist VERY tough. I etch using a small sponge and just rub the ferric chloride across the board rather than the "bath" method. I can get through 1 oz copper in about 5 minutes this way, and you can watch the process and apply etching where it is needed. I get great results down to 8 mil traces with hardly ever a void.
As for the etching I've built a new heated and aerated etching tank this week to try and get a more consistent etch, but if I have problems with that the sponge method is something I'm going to try.
Have you tried reprinting it 2 or more times to make the ink thicker?
As for the aluminum or possibly steel I'm just going by what I was told it was could be either I'm not 100% sure.
If you check out some engraving supply sites they sell a thin double sided tape that releases easily for holding down your boards that may make setting up easier.
You need to redo your math on the metric copper thickness. (I think you mean 35 um (micrometer))