Now we have our board cleaned up and touched up if necessary it’s time to etch the thing.
It’s important to do some test boards with your chemicals to ensure that you get the mix right and also to get a rough idea of the timing you need to allow.
I’m using a mixture of Sodium Perborate and Hydrochloric acid. I’m not sure what the proper name or formula is for this mix. It’s the standard mix for sale here in Barcelona.
I make the mix up in a large ABS plastic container in a well ventilated space with plenty of water handy just in case. We’re talking about the kitchen here…
Place the board ready in the same container as before (emptied out and dried of course) and pour the etchant over the top of the board. Careful not to splash any.
Plastic tweazers are handy for handling the board. Note this
etchant is green as I have used it before, fresh mix is clear.
The etchant bubbles a little when you first put it in. I think it’s the
paper that causes this as later on the bubbles stop even though
the etching continues.
After a couple of minutes the etching is really starting to show.
All I’ve done is to give it a bit of a gentle agitation, no heating or
A minute of two later we’re nearly there. The remaining copper is
very thin and won’t take long to disappear
After about 5 minutes we should be well on our way. There are bound to be lots of fine traces remaining which we need to keep an eye on to ensure that they are all etched away properly. I like to etch using a clear tub that I can shine a light through underneath. It makes watching the etch progress much easier. The exact timing probably depends on temperature, time of day, phase of the moon etc.
Just a little over 7 minutes and all that remains is a couple of thin patches.
Dunk it for a few more seconds and we’re done.
When you think you are done take your board out and rinse it under the tap. Hold it up to the light or against a window (in the daytime) to inspect it for copper bridges that may remain. You’ll need to use you judgment as to how you fix the any bridges. If they are quite extensive then you probably need to drop your board back in the etch bath for a few another minute. If however your board use lots of ultra fine traces and is pretty well etched on the whole then you don’t want to risk over etching. In this case you might be best off removing any bridges the manual way with a scalpel or similar.
Once your etch is complete pour the solution safely back into your storage container. (assuming that you’re not etching any more boards)
Ok, I know. I should have done this in the kitchen really.
The light was good in here for taking the photos.
Now you need to clean your board up to be ready to move on to the next phase. You can use just about any method you like short of sandpaper to remove the toner. Some people just use a scouring pad and some elbow grease, others, like me, go for the easy route and splash a bit of universal solvent into the deal. Either way, we just need to remove the toner so we can solder easily solder our components.
Golden Cat Universal solvent. I’m not certain what this is made from.
I think I’d rather not know.
This is the stuff I use. We’ve had it around the house for ages. It’s horrible stuff and melts just about everything, but it’s great for removing toner. It’s so old that the price is actually in Pesetas as well as Euro which puts it at circa 2002 I think.
A dab of solvent works its magic.
The board etched and cleaned up ready for soldering.
Here’s the board along side its sister board. The one on the right is for
the LED display, the one on the left is for the rest of the components.
Now we are finished. Your timings may differ, there are probably lots of influences such as ambient temperature, exact mixture etc. But for me it takes around 5 – 10 minutes to etch boards of this size and surface area.
Next step. Construction : But that’s for a later date as I have things to do.
I found an Epson Stylus Colour 1520 on the street that I’m going to cannibalize for all the goodies like stepper motors and switches.