Using Ammonium Persulphate

[50caliber]

Hey guys,

I have some PNP blue and was just about to use it but I don't know how to etch the board with Ammonium Persulphate could someone send me a link to a tutorial or give me instructions?

Also I have the layout in eagle and want to print it on a 4 inch by 3 inch copper clad board, how will I change the size of the layout image on the computer?

Thanks guys

[ACS]

I would have thought there were instructions that came with it?

Mine say to mix in a 1:5 ratio with hot (75°C) water - which in effect for me means a good dollop (a couple of tablespoons) of the persulphate mixed with a decent splash (100mL or so) or hot (ie out of the tap) water.  Put it in a small plastic disposable container (I find the ones that my Chinese takeaways come in just perfect!) add the PCB and agitate.

I agitate by swirling for a few minutes, then typically pop it all in the microwave for a few second to heat it back up again.  Keep agitating - seems like nothing much is happening for a while (other than small bubbles) but then after maybe 6-8 mintues you'll see the edges of the copper start to go, then pretty quickly over the next minute or so it will be done.

Hard to go wrong really - 'bucket chemistry' is the phrase I like to use...

Aidan

[50caliber]

Cheers mate I didnt realise it was that simple.

I might put the container on top of a hot water bottle to keep it warm and that way you could roll it back and forth

[ACS]

No worries - as I said, it's hard to go wrong I reckon...

As for your second issue with printing at the right size, you've got a couple of options open to you.  I don't use Eagle, so this is generic advice.  There may be a shortcut to this in Eagle...

1. Use the 'scale' function in your print driver to scale the printed image up or down until you get the size you want.  Takes a few test prints on paper to get it right (10 or so often, depending on your eye!), but there you go.
2. Print from Eagle to a pdf (use a free PDF printer such as CutePDF for example).  Copy the image from this PDF (can use ctrl+A, copy and paste in most PDF's) in to your favourite image editor, scale a bunch of them up and down (you can usually fit 6-8 on a page) and test print to paper.  Pick the closest, scale up and down again from there, test print again, and you'll be sure to find one that's on the money.

You could screen grab to achieve the same effect as 2, but the quality is usually not quite as good...  may or may not be an issue for you.

I usually like to use an IC as a standard measurement - ie when that's printed to the right size, then you know the rest is right.  If no IC, then it's less critical, so just eyeball it until you think the spacing is about right

Good luck!
Aidan

[sasuke_kun12]

I usually shake the container really violently to agitate my PCB. I might make an agitator with a left over toy car motor