Making a PCB using Press 'N Peel Blue

[jimbob]

Im just now deciding to learn how to use this technique as i followed the essay from Tonepad -thanks Fransisco btw-- anyway, it ends before i can learn about the etching process. How do i get the extra copper off the board (the copper that is not part of the traces ect..) It says something about ferric chloride? ammonium persulfate? How does this work?

thanks

jimbob

[markr04]

My suggestion: avoid Ferric Chloride. Go with either Ammonium Persulphate or Sodium Persulphate. Ferric Chloride is such a hassle (you can't pour it down the drain because it will eat at your plumbing, for example). Although it has been successfully used for many years, I was told that ferric is going to be phased out in favor of the 'more friendly' chemicals anyway. The other two are *much* easier to deal with.

The persulphates come in a powder form. Mix 1 part powder and 4 parts water. It's a clear liquid. It turns a slight blue as the copper is eaten away.

Here's a link for the process. Skip the printing part (or read it if you're interested in an alternative to Press n Peel) and go to the etching part.

These instructions are for ferric chloride. If you use the persulphates, you can skip all the notes dealing with the hassle of disposal, not using anything steel, etc. that pertain to ferric only. The etching process itself is the same no matter which chemical you go with.

http://www.fullnet.com/u/tomg/gooteepc.htm

[ESPm2M]

... dead link ...

[Torchy]

Anyone know where to get the alternatives to Ferric in the UK ?

[LinuxMan]

... dead link ...

It works for me...

Cheers
LM

[ESPm2M]

When I posted that the link was not working.  This was the case for some time after as well.  It seems to work now though

[Mark Hammer]

Although other things ARE better then ferric chloride, FeCl is about the easiest to obtain etchant, comes premixed, and doesn't need to be warmed.  

Yes it does eat the copper in your home's plumbing every bit as easily as it eats the copper on the board, BUT.....

...if the used stuff won't eat the copper on the board, then it won't be all that aggressive towards your plumbing either.  When you realize how much the tiniest bit of "finger juice" on the copper prevents the etchant from working, you'll feel a lot better about what the odds are that used etchant will eat through decades-old plumbing with all sorts of grime-of-ages coating it.

Plumbing is not your only concern, though.  FeCl stains like nothing else.  It's like the hoof and mouth disease of clothing stains.  If one article of clothing gets stains, you CANNOT wash it with anything else you want to keep pristine because the FeCl will come off in the wash and attach itself to other pieces of clothing too.

On top of this, FeCl is not very nice to the wee beasties out there whose lives are affected by what comes out of your plumbing.  So, flushing it down the drain is contraindicated.

What you CAN do is de-activate it with baking soda.  The baking soda will foster a chemical reaction that will result in salt and rust among other things, and leave very little FeCl when its done.

Please note, however, that this chemical reaction takes FAR more space than the FeCl and baking soda itself occupy.  Figure about 10 times more space.  Seriously.  So if you want to deactivate an older batch of FeCl, pour it into a MUCH larger plastic or glass container (reserved for just that purpose), and bit by bit mix in the baking soda.  It will start to foam and heat up (it's the foaminess that takes up all the space).  If the container requires stirring, stir gently.  If it will withstand shaking, shake gently., adding in a bit more soda and a bit more.  Eventually, it will stop growing, and turn into something that sort of resembles cotton candy from hell.  At that point, it is dry and you can just dump it in a bag and throw it out.  Like I said, at that point you have essentially a big bang of rust and salt.  The bag contents will ALSO stain clothes, but it will be safe to stick in the municipal garbage.

Given all this nuisance, one of the things you can derive from this little description is that:

a) You REALLY don't want to fill up any container with fresh or used etchant anywhere near the brim.  Always leave lotsa space between the level of the etchant and the level of the container.

b) You probably don't want to make up or use large batches of the stuff at any time because deactivating a pint of it is a big deal.  I tend to use smaller inexpensive resealable containers from the dollar store, such as "sandwich" containers for lunch kits.  The size is pretty much big enough for everything that is posted at Tonepad, and most of the stuff posted at GGG.

The cleaner/fresher the etchant, the better/faster it will work.  Although you don't NEED to warm it up, warming helps to speed up etching.  I generally just float the board on top of the etchant, face down, and warm the board from behind with a hair dryer, heat gun on low, or a desk lamp pointed at it.