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In this Instructable, I will show you how to etch a circuit board with about a tablespoon of ferric chloride etching solution and a 2 inch square sponge. You will be amazed as the exposed copper on the PCB disappears before your eyes, and your board is completely etched in a minute or less!
I found a passing mention of this technique of using a sponge with a small amount of ferric chloride on the Pulsar web site, and I was very skeptical that it could possibly work. So naturally, I tried it.
Whenever I have made circuit boards in the past, I did it just like most of us do. I put the ferric chloride into a small tub, dropped the masked circuit board into the solution, and rocked it back and forth for a long time. Even with fresh, strong ferric chloride solution, it would usually take at least 10 minutes for the copper to be removed. As the solution grew weaker, the etch would take longer and longer.
A few months ago, I discovered the 1-part pool acid (muriatic acid) to 2 parts hydrogen peroxide method of etching a circuit board. You will find lots of wonderful Instructables on this method. That method works great, and it made me mad that I spent so much money and effort with ferric chloride over the years when I already had all the chemicals I needed right at home to use this method. The down sides of the acid and hydrogen peroxide solution are that the muriatic acid can cause skin burns and is a little dangerous and damages things that it contacts. Also, I found the etching solution to be quite aggressive which was great for fast etching, but I ended up with severe undercutting and partial obliteration of the traces, and the solution tended to be more corrosive to the resist materials I used, and partially dissolved the mask away during the etch.
This weekend I tried this sponge and ferric chloride method to etch 3 Arduino shield boards I am prototyping for our RFID-enabled member access system at TechShop (TechShop is the 15,000 square foot membership-based DIY workshop with locations in Menlo Park CA, Portland OR and Durham NC). I was so impressed with the success of this technique that I decided to write it up as an Instructable.
The method I will now show you gives you the advantages of all the other methods, and none of the downsides. Specifically:
o You get a fast etch (much faster than either method I know of),
o You use a tablespoon of solution, so disposal problems are eliminated
o A small bottle of ferric chloride will last for hundreds of boards
o No tank or tub is needed, no heating or agitation
o Undercutting is practically non-existent, and the resist stays in place
o There is no need to try to reduce the amount of copper being etched
o The etch is so fast that it is actually exciting to watch and show your friends!
Let's get to it, shall we?
I found a passing mention of this technique of using a sponge with a small amount of ferric chloride on the Pulsar web site, and I was very skeptical that it could possibly work. So naturally, I tried it.
Whenever I have made circuit boards in the past, I did it just like most of us do. I put the ferric chloride into a small tub, dropped the masked circuit board into the solution, and rocked it back and forth for a long time. Even with fresh, strong ferric chloride solution, it would usually take at least 10 minutes for the copper to be removed. As the solution grew weaker, the etch would take longer and longer.
A few months ago, I discovered the 1-part pool acid (muriatic acid) to 2 parts hydrogen peroxide method of etching a circuit board. You will find lots of wonderful Instructables on this method. That method works great, and it made me mad that I spent so much money and effort with ferric chloride over the years when I already had all the chemicals I needed right at home to use this method. The down sides of the acid and hydrogen peroxide solution are that the muriatic acid can cause skin burns and is a little dangerous and damages things that it contacts. Also, I found the etching solution to be quite aggressive which was great for fast etching, but I ended up with severe undercutting and partial obliteration of the traces, and the solution tended to be more corrosive to the resist materials I used, and partially dissolved the mask away during the etch.
This weekend I tried this sponge and ferric chloride method to etch 3 Arduino shield boards I am prototyping for our RFID-enabled member access system at TechShop (TechShop is the 15,000 square foot membership-based DIY workshop with locations in Menlo Park CA, Portland OR and Durham NC). I was so impressed with the success of this technique that I decided to write it up as an Instructable.
The method I will now show you gives you the advantages of all the other methods, and none of the downsides. Specifically:
o You get a fast etch (much faster than either method I know of),
o You use a tablespoon of solution, so disposal problems are eliminated
o A small bottle of ferric chloride will last for hundreds of boards
o No tank or tub is needed, no heating or agitation
o Undercutting is practically non-existent, and the resist stays in place
o There is no need to try to reduce the amount of copper being etched
o The etch is so fast that it is actually exciting to watch and show your friends!
Let's get to it, shall we?
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Signing UpStep 1What You Will Need
You don't need a lot of supplies for this Instructable, just the following:
o Ferric chloride (available at Radio Shack, 16 oz bottle for $10, part number 276-1535)
o Sponge (2" x 2" square, cut from any sponge, or paper towel will work too)
o Rubber Gloves (you don't want to stain your hands)
o Copper Circuit Board (one or two sided)
o Cup of water (to drop the etched board into to stop the etching)
o Ferric chloride (available at Radio Shack, 16 oz bottle for $10, part number 276-1535)
o Sponge (2" x 2" square, cut from any sponge, or paper towel will work too)
o Rubber Gloves (you don't want to stain your hands)
o Copper Circuit Board (one or two sided)
o Cup of water (to drop the etched board into to stop the etching)
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Regardless, it was my first ever PCB and it's not too bad, I think!
I use mine for touching up toner transfer on the occasion there is a hole or some other problem.
Regards,
Nicolae
Good point! Yes, Sharpie pen will often rub off, even during traditional tank etching.
I've never tried this, but I wonder if a paint pen would work? It might be a little bit too coarse, though.
There is a so a type of pen called a Rapidograph made by Koh-I-Noor (intro video on YouTube at http://youtu.be/xHSIk4Y79BY) that are really amazing and cool pens for drawing VERY detailed drawings. You fill them yourself with any india ink, so if you used a waterproof india ink, I wonder if that would work for resist for PCBs?
The rapidograph looks interesting — I may have to get hold of one of those.
P.S. My PCB soldered very well — on to testing now :|
Disposing the etchant in small amounts over a long time is no different than disposing the whole lot at once, it would all still end up down the drain.
Better to collect it all up (whatever way you etch) and take it to a proper disposal place in the end.
Where I live the local firehall will take whatever chemicals. You just drive them over in an onimous container and they'll add it to a big pile of mysterious things.
good lord :-)
all mine's pvc
"Disposal Considerations
Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. Although not a listed RCRA hazardous waste, this material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specific disposal requirements. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements. "
Its not much help, but I would take it to a landfill on one of their hazmat days, although its not illegal to dump it.
That said don't forget you are using a tiny fraction of the FeCl3 solution that the "traditional" method calls for per. PCB (and I bet lots of that solution goes guess where?). Also, the small amount of solution that is used using this method gets diluted many times over will probably not effect house pipes to any measurable degree. Just flush with lots of rinse water after each session.
You should always be careful about what you put down the drain. But ...well , I don`t know really.
I see what you`re saying , about this being a small source of copper into the nature. And I think it is.
But it could have been interesting to do some math on it, sometime : )
thats what i think when i pour stuff (harmful) down the drain
The thing about all this is...when you flush material down the drain, it DOES NOT go into your local lake, stream, river, or ocean! It goes to your community's waste water treatment plant. They precipitate out the metals (it is valuable to them), and the even use ferric chloride in the treatment process!
So unless you live on a boat and you dump your waste at sea, or you live in the back woods of some remote location and your sink and toilet pipes drain directly into the creek, your use of ferric chloride to etch circuit boards is NOT going to hut any aquatic life!
The people in your neighborhood collectively put more copper into the water system (from the copper cladding on the zinc pennies wearing down in their pocket and then laundering their pants) than you every will by etching circuit boards at home.
Am I missing something huge here, or is this a good idea?
You can use acetone or finger nail polish remover, or Zippo liquid lighter fluid (also known as naphthalene and white camp stove gasoline...not BBQ charcoal lighter liquid). Just pour a little bit on a rag and wipe off the sharpie marks.
Those of you having trouble, I can explain. Jim is using 1/2 oz copper laminate. If you're using 1 oz, it takes considerably longer. I like using the 1/2 oz copper boards just for this reason - it goes so much quicker. (I've done it with both types of board.)
Thanks
Were you using 1/2-oz, 1-oz, or 2-oz copper? I have heard from people using 2-oz and sometimes 1-oz copper that it takes a lot longer.
If your ferric chloride is working in the tank, it should work with the sponge.
I'm very surprised to hear that it didn't work for you...I have received hundreds of positive comments from people that love this technique, and literally only yours from someone who didn't find it to work.
Was your sponge wet with water before you put the ferric chloride onto it? The sponge should be dry.
Thanks!
Good Question !
Not sure on the weight of the PCB, suspect around 1oz. The sponge was dry. The ferric chloride was a new bottle from the same supplier which I used in the etching tank set up. The PCB was create using the Laser printer transfer method, the board was fully cleaned before transferring the layout design.
So unless I'm doing something completely wrong (possible), it just isn't working. I would love to use this method, looks really good so anything else you can suggest would be appreciated.
Thanks!
I was having tons of trouble with the dextrin paper. If I failed to get a good transfer the first time, the copper was super hard to clean good enough. After some experimenting I found a process that works most of the time.
Clean the PCB with acetone.
Clean the pcb with a soft sponge and class cooktop cleaner.
Rinse well and clean with white vinegar.
Rinse well and clean with dish soap.
Then I replaced the dextrin paper with "Reynolds Brand Genuine Parchment Paper" (kitchen supply stuff)! I used double sticky tape to put it on top of regular paper for the trip through my laserjet. (YMMV with double stick tape in the guts of a printer! You can easily cut it into big enough sheets not to need that if you worry.)
Toner sticks well enough to the parchment paper, but just barely. One pass through the laminator and the traces were fused perfectly and no need for the soaking. Due to the transparency of the parchment paper lining up double sided boards is easy in any light. The biggest problem is that the board doesn't stick to the paper even a little so you need to be careful when feeding it into the laminator that it does not shift. An iron would probably not work if the paper shifted under it at all.
Hi Dustin...
Wow, that's a great idea! I use parchment paper all the time at home for cooking candies and breads, and I never thought of using it for this purpose!
Thanks!