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DIY PCB Etching Technique preferences?
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Please be positive and constructive with your questions and comments.

DIY PCB Etching Technique preferences?

by robodude666 on Tue Nov 09, 2010 10:22 am

Hey guys,

My Birthday is coming up, so I decided to spoil myself with some new fun toys. I've been wanting to make DIY PCBs for a long while, and figured this is the perfect time. Between my senior project for college and some other projects being able to make PCBs would be very useful.

I am considering getting the kit from Jameco based on Collin Cunningham's Circuit Skills articles on Make Magazine. This particular method uses pre-sensitized boards and UV light to "print" the design onto the board, then positive solution to develop the board and ferric chloride to etch the board. I know there is another popular method for getting the pattern onto the board. Some people find it preferable to print the design onto paper, then using an iron to transfer the toner onto the copper clad and use hot water to remove the paper bits leaving the toner on the board.

Is there anything that suggests one method is "better" than the other? In either case you'll need ferric chloride (though I do wish there was something that could be easily disposed of). I like the idea of the toner transfer method simply because it seems less time critical and requires less chemicals. You don't have to worry about exposing the PCB to light ahead of time, etc... however, it seems the photo-resist method is gaining popularity over the past year or two.

In either case, I don't have a lazer printer but I have access to one in my school. It also seems regular copper clad boards (that aren't pre-sensitized for the photo-resist method) are really cheap (like ~70c a pop on ebay!).

What do you guys think?

-robodude666
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Re: DIY PCB Etching Technique preferences?

by Entropy on Tue Nov 09, 2010 1:23 pm

You might want to read some of the articles on cupric chloride etchant. It's reusable/refreshable, and when you do have to dispose of it, it is apparently a lot easier to "render safe" for disposal than FeCL. It is somewhat harder to work with though.
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Re: DIY PCB Etching Technique preferences?

by mitpatterson on Tue Nov 09, 2010 1:29 pm

I use the toner transfer method, and i use ferric cloride, one way i have found that i belive makes it somewhat safer to dispose of it to mix in like a lot(like a 1 lb box) of baking soda, should nuturalize the acid and turn it into a solid, not sure if you can put it in the trash then or not.

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Re: DIY PCB Etching Technique preferences?

by robodude666 on Tue Nov 09, 2010 2:02 pm

mit, MGChemicals has a FAQ where they mention sodium carbonate. However, they still say the solid that's left over should be disposed of properly. Not sure what the law is in NYC.

Entropy, I ran across the cupric chloride article on instructables but I question it still. Wikipedia says cupric chloride is toxic, and eventually you'll end up with a lot of solution if you simply keep reusing it and adding acid to it or do you have to add very little acid + aeration to revitalize the solution?

If Cupric Chloride is used instead of Ferric Chloride, would the etching process still be the same except with the different etchant being used?

-robodude666
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Re: DIY PCB Etching Technique preferences?

by mitpatterson on Tue Nov 09, 2010 2:15 pm

I don't go though very much FC, so i really haven't had to deal with disposal, but what i do i keep a bucket(1 gal) of warm water mixed with backing soda near by to rinse my hands(gloved of course) and the board off in to naturalize the acid, and that whole 1 gal gets mixed with a bit more baking soda and dumped down the drain with a lot more water, my guess is in that whole amount there is less than 1 oz of FC in there, so i highly doubt that little will hurt anything. For larger amounts according to MG it looks like you can neutralized it and pour off the water, and further dilute it pour down the drain, and then the sludge left needs to be disposed of. Like i said i don't use very much at a time, i use a sponge to spread it, so i only use a few ounces at a time and i just keep reusing it, and when i used even less, say 1 ounce outside i just mixed it with a lot of water and BS and poured in the grass(only did this once, and it was only 1 ounce, so i doubt i did any harm), i have no clue the law, and for hobbyist amounts, if you really naturalize it i doubt it will cause any harm.

Now if you start talking gallons of the stuff that is a different issue

Now as far as boards i have had good success with these: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=360150127369 and no, i'm not affiliated with them in anyway, but they where fast and they cut to about any size you want they also have many other thickness's and single sided available as well

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Re: DIY PCB Etching Technique preferences?

by mitpatterson on Tue Nov 09, 2010 2:23 pm

Also to the EPA, if you need to send me a letter regarding any violations just send it to my forums private message's it will probably end up in a circular recycling bin since i like to recycle(seriously i do)

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Re: DIY PCB Etching Technique preferences?

by uhe on Wed Nov 10, 2010 3:15 pm

I use Sodium persulfate (Na2S2O8) for etching and toner transfer for the layout.
Sodium persulfate dissolves in water to a clear solution which gets blue over time. It sould be 40°-50°C hot but a hot water bath gives good results too.
I do not use photo-resist method because toner transfer is faster and easier and I do not need the precision and definitely better results of the photo resist method.
"I have not failed. I've just found 10,000 ways that won't work." - Thomas Edison
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Re: DIY PCB Etching Technique preferences?

by robodude666 on Wed Nov 10, 2010 7:25 pm

I think I like the Cupric Chloride as the etchant from all that I've read. It's not as dangerous as some other chemicals being used, and it's easily made. The copper clad supplier mit linked to on eBay seems excellent as they can cut boards to a custom size for you.

The photo-resist method does seem a bit better, but I'll try the toner transfer method first. It has easier setup and requires less materials.

Hope to get the stuff in a week or two and make a few boards. I wonder board I should etch first.. I don't have any designs ready.. hmm.
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Re: DIY PCB Etching Technique preferences?

by mitpatterson on Thu Nov 11, 2010 5:08 pm

I did a test etch today, and i figured i would share with you guys, I used those boards i linked to from ebay, and used Ferric clorride from Radio Shack, I used the test patern from here: http://dorkbotpdx.org/blog/laen/adventures_in_etching_the_test_pattern My results are below, the black dots on the test pads show the pads that had continuity between them. The other side didn't have any continuity between any pads, so i must have screwed that one up, but 50% success isn't too bad for my first time with this pattern, and i did not touch up any traces either before or after, normally i would use a sharpie to touch up before etching, but for this test i didn't
test etch.jpg
Test Etch
test etch.jpg (248.72 KiB) Viewed 1904 times

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