Save your money!! Printing own PCB's

Hydroid

Senior Member
While not directly to do with Picaxe, I do use it to manufacture PCB's for use with Picaxe projects, so maybe someone else can benefit from my experience. I did a quick search and couldn't find this subject having been discussed before, so here goes...

For years, I've been using positive pre-sensitized PCB to make my own printed circuit boards. I retrofitted an old Canon scanner with a dual strip of UV Leds to act as the exposure device and it works very well. A few days ago, I realized I was running low on positive developer fluid, so I checked my places where I get supplies and got a shock. The last time I bought a litre of the stuff, about a year ago, it was $10.99 Cdn. Now, they want over $30!

I called my brother about it - as he's a chemist - and asked if he had any idea if he could bulk order it through his company to save a few $$. He asked me for the exact name of the product, which I gave him. A few seconds later, he replies, "Why don't you mix it yourself?" Huh?, was my response...

He tells me that all he did was Google the product name appended with MSDS and he quickly found the "Material Safety Data Sheet" for the product. Seems that it's required by law to make those available for hazardous chemicals. "So what's in this stuff?", I ask. He says, "10% Sodium Hydroxide (NaOH) by weight and distilled water, that's it"....

Because you mix the developer in a 1:10 ratio with water to get the working developing fluid (1 part developer to 10 parts water), the actual amount of NaOH in the working fluid is in a ratio of 1:100, so to make a litre of the final developing fluid to use for developing the exposed PCB, you just need to mix 10 grams of NaOH in a litre of water. He also suggested that I add the 10g to about 100 ml of water initially to speed up the dissolving of the NaOH. He told me it would get a bit warm, but nothing to worry about. Once dissolved, top it up to a full litre of water.

So, I just went to my local hardware store where I bout a 500g bottle of 100% NaOH (they sell it for unplugging drains and such) for less than $4. I got it home, mixed it up as described above (10g NaOH to 1 litre of tap water - I didn't have distilled on hand) and then put in my small test piece of exposed PCB scrap, and bingo, works EXACTLY the same as the $30 stuff!

So, for my ~$5 investment in NaOH, I can make 50 litres of final working developer. Buying the concentrate would cost me $150 (5 bottles on concentrate at $30/bottle to make the same 50L of final fluid).

I keep thinking how much money I've wasted over the years buying really expensive diluted drain cleaner.... Boy, do I feel stupid!

Live and learn :)
 
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stan74

Senior Member
I used to print pcb designs on paper with a laser printer then clothes iron them to the copper for a minute before etching with fecl. Tracks between pins no prob. Cheap and fast.
 

premelec

Senior Member
Pretty much anything you etch copper with ends up with toxic copper salts - you can evaporate them to a solid and take to your nearest.... hazardous material repository... or put them in a jar in the basement for future reference... my approach has been to etch as little area as possible... ;-0
 

Rick100

Senior Member
Disposing of the left over ferric chloride is one of the reasons I switched to milling my pc boards with a cnc engraver.
http://www.gearbest.com/3d-printers--3d-printer-kits/pp_356128.html?wid=21
That's not an endorsement of this product since I had to replace several parts to get good results. I think it's a little faster process than etching, since drilling the holes only requires a bit change.

When I etched my boards, I used the process Stan described of Laser printing to cheap photo paper and transferring to the copper with an iron. The transfer process was the tricky part. The etching was the easy and fun part. Drilling out the holes was not fun. Even with a Dremel drill press, I broke several .025 inch drills over the years.

I just looked at both bottles of Radio Shack ferric chloride etching solution on my shelf. The instructions for disposal of the use solution on both bottles say:
"Discard used solution into toilet bowl and flush."
The Safety Data Sheet linked to by the the RS website says take it to a waste facility.

I guess I'll just leave them on the shelf for "future reference" like premelec said.
 

SAborn

Senior Member
For over 20 years now i have use NaOH (which is Caustic Soda here in Oz) you can buy it in the super market or hardware store.
I do suggest a lower ratio of 7 grams per litre, as 10g/ltr can strip some resist boards, and when the solution is a little old or in cold weather warm it in a bucket of hot tap water.

As for disposal of use ferric chloride, try placing some bare steel ( scrap metal, nails, screws, etc) into the solution for a few days, what you will find is the copper and ferric parts of the solution will clump together and settle to the bottom of the solution, leaving a almost clear acid solution behind which is very except able to be flushed down the drain, minus the copper sludge settled to the bottom.
 

premelec

Senior Member
I recall some impressive youtube videos on peroxide etching - but haven't tried it - did mention fumes but seemed very fast if you can get the high % peroxide... you still have a copper toxic to dispose...
 

stan74

Senior Member
See my last post premelec. Printing a reverse pcb on paper with a laser printer with the toner set high and ironing on to copper works brill and is very fast. Just photo copy a design and reverse it with windoze paint. Not many people have a laser printer though, I don't.
 

Hydroid

Senior Member

Hydroid

Senior Member
I used to print pcb designs on paper with a laser printer then clothes iron them to the copper for a minute before etching with fecl. Tracks between pins no prob. Cheap and fast.
I also use that method and find it works well. I modified a laminator to run at hotter temperatures and got improved results. It works great for basic boards, but I've had no luck with really fine detail. Case in point, I tried to make a PCB for use with a CAT4016 constant current LED driver chip (TSSOP24 format) and the trace widths of 0.01" were just too thin for the laser printer method - even when using the pricey "blue" transfer paper. By comparison, the pre-sensitized PCB method worked great the very first time. Might be just a function of my Samsung laser printer, it wasn't that expensive, so maybe a better laser could do it - Don't know..
 

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