Instructables

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.
 
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ryanbou2 years ago
Awesome work. Question- could a laser printer be modified in this same way to directly print toner onto a board?
MandingaRes3 years ago
En general no hago críticas a ningún proyecto porque me parece que es de muy mal gusto. Al contrario me gusta ponderar las nuevas ideas y ésta en especial me parece fantástica ya que "abre la cabeza" respecto a todo lo que se puede modificar (reciclar) y darle otra una segunda posibilidad de uso a muchos elementos que normalmente irían a parar a la basura.
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)
e5frog3 years ago
The idea was good, the final result not really that good unfortunately.
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?
wa7jos3 years ago
How about a hybrid solution between this and the TTF method?
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.
kidharris3 years ago
Did you check your printer settings to be sure that you are printing in the best quality possible?

Have you tried reprinting it 2 or more times to make the ink thicker?
PS. Your anodized aluminum sure looks a lot like galvanized steel to me.

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.
michaeloqu3 years ago
I can understand why H2O2 would do that. It's a very agressive oxidizer. But it's posslble to make a CuCl2 solution without using any H2O2 at all. With a solution of Cuperic Clhoride + HCl it should have a much less agressive overall oxidation rate; the primary oxidation is performed by the CuCl2 itself, not the HCl. The reaction is CuCl2 + Cu (metalic copper on the board) --> 2(CuCl).

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?
rewolff3 years ago
2.8 mm copper is REALLY thick. That'd be about twice the thickness of the board.

You need to redo your math on the metric copper thickness. (I think you mean 35 um (micrometer))