pcb etching

Thread Starter

adamclark

Joined Oct 4, 2013
472
I currently have another thread going for my diy psu. Im going to need to be making some pcb's real soon as im progressing faster than expected.. I have never etched a board before so I would like to do it as easy as possible.. ive searched and it seems like theres a dozen different ways to do it.. I do like the idea of uv etching though.. the less chemicals the better.. I don't think im going to need dozens of tiny traces at first. thanks for any ideas you can add for me.
 

Thread Starter

adamclark

Joined Oct 4, 2013
472
and before someone says it,, ive tried searching the site, but the search function will not work for me.. everything I search returns 0 results...thank you
 

jpanhalt

Joined Jan 18, 2008
11,087
I do like the idea of uv etching though.. the less chemicals the better.. I don't think im going to need dozens of tiny traces at first. thanks for any ideas you can add for me.
UV does not etch the boards. It is used to make the resist pattern before etching and utilizes more chemicals than the toner transfer method. At a minimum, the UV method requires a chemical developer for the photographic image. With a positive resist, which I suspect you would use, that developer can be as simple as a solution of lye in water.

For etching, I recommend ferric chloride. It is a robust etchant and is difficult to screw up. Some people prefer HCl and hydrogen peroxide. That works, but in my experience, it is more sensitive to conditions than ferric chloride.

All chemical etchants involve oxidation of unwanted copper on the PCB. They all produce waste; although, some users reuse that waste for making additional etchant.

John
 

GopherT

Joined Nov 23, 2012
8,009
The UV process works well if you can find the chemicals at a good price.
I have used the MG Chemicals photo boards - coating boards yourselves is a pita and no faster or better than laser toner transfer method.
 

Thread Starter

adamclark

Joined Oct 4, 2013
472
im not sure what the problem is for me searching.. it always returns 0 results.. I just typed in 555 timer and got 0 results. and I know for a fact there are hundreds of 555 threads.. as far as etching goes, Im starting from scratch and don't have any equipment at this point.. so I guess im looking for the way that requires the least chemicals and is the most foolproof so I can gain experience. At the moment im building a psu so the pcb's I need wont be to complex.
 

jpanhalt

Joined Jan 18, 2008
11,087
I guess im looking for the way that requires the least chemicals and is the most foolproof
I can appreciate your frustration with Internet searches that always show "0" returns. It is good you discovered that little challenge.

Now, you ask for the etching method that requires the "least chemicals." Did you my my post also not appear on your monitor? Ferric chloride is ONE chemical dissolved in water. It is a bit hard to conceive of a method doable at home that would involve fewer chemicals.

John
 

Thread Starter

adamclark

Joined Oct 4, 2013
472
I can appreciate your frustration with Internet searches that always show "0" returns. It is good you discovered that little challenge.

Now, you ask for the etching method that requires the "least chemicals." Did you my my post also not appear on your monitor? Ferric chloride is ONE chemical dissolved in water. It is a bit hard to conceive of a method doable at home that would involve fewer chemicals.

John
I did read it, then I read bill marsdens article and it covers the ferric chloride method but that's just for etching. I am probably most certainly going to use it to etch as you stated but I also would like some opinions on the actual transfer methods. as I stated my circuit isn't going to be overcomplicated. I was considering just using a resist marker to draw my traces on the copper clad board and then using the ferric chloride to etch.. would this even work? I don't want to buy a laminator and laser printer for the toner methods. at least not yet until my needs make the purchases necessary. My bad for not being as clear as I could be, I tend to think faster than I type
 

Lestraveled

Joined May 19, 2014
1,946
Here is my method for home made PCBs.

1. Print your PCB pattern onto clear transparency film. (The stuff used for over head projectors.) Get the kind that works with your printer. You will need 3 copies.

2. Take the 3 copies and align them perfectly. Tape them together. This makes the pattern very opaque.

3. Buy pre-sensitised Positive resist printed circuit board stock. Place your transparency on the board and sandwich using a pane of glass and foam on a stiff surface.

4. Expose to direct sunlight. Exposure time will between 4 and 20 minutes. Do a test run on a small sample to establish the correct exposure time. This is the most critical part of the process.

5. Develop, etch and drill.
 

jpanhalt

Joined Jan 18, 2008
11,087
My method is similar to yours with two differences:
1) If my transparency is not dense enough without needing multiple copies, I fill in the spaces with a white board black marker: http://www.electro-tech-online.com/blog-entries/improved-laserjet-transparencies-for-pcb.213/ Alternatively, an ink jet printer will give sufficient density for a single transparency thickness.

2) I use regular 15W fluorescent light bulbs for exposure. That gives a reproducible exposure of about 15 minutes.

John
 

GopherT

Joined Nov 23, 2012
8,009
Yes, you can just use a SHARPIE marker and etch with ferric chloride. Then drill and mount your components. It has been done this way for years.
 

Lestraveled

Joined May 19, 2014
1,946
You can use the above methods to make double sided boards also. You take your patterns and tape them to a strip of PCB stock. Of course you align the patterns very carefully when you tape them. The top side transparency needs to fold out like a cover of a book. This will allow you to tape the sensitized PCB to the strip of PCB stock. This holds everything in registration when you flip it to expose the second side.
 

jpanhalt

Joined Jan 18, 2008
11,087
When it gets so complicated as to need double sides and a large number of vias, I go commercial, including solder resist. The price difference was trivial. I used to use my exposure apparatus for double-sided boards regularly.

John
 
Top