Instructables

The Etchinator - low cost PCB spray etcher (under $100)

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What/Where/Why/How?


What is etching and what is spray etching?


Etching is the process of eating away a pattern on a target material by using an etchant liquid that attacks the target material.

The most common target materials are copper and brass. The most common etchant liquids are ferric chloride, ammonium persulphate and cupric chloride

On a hobby scale it is common to submerge the target into a container filled with the etchant. This can be very slow and is often sped up by either mechanical agitation or using an aquarium / fish-tank bubbler. Even with the speed up from sloshing the container around this process can take 10-15 minutes for a PCB or over an hour for a thick brass plate.

The spray etching method uses the same etchant liquid as the submersion method, but instead sprays the liquid onto the target. This can speed up the process by an order of magnitude.

The advantages that spray etching has over the more mundane submersion method of etching is
  1. Faster
  2. Less manually intensive
  3. More uniform etch
  4. Produces sharper edges / better detail

Where are spray etchers used?

  • Manufacturing PCB (Printed Circuit Boards)
  • Etching plates for intaglio printmaking
  • Etching brass nameplates / plaques
  • Photochemical machining of mechanical parts (often used in model trains)
  • Etching jewellery
  • Etching stencils (if you can't afford a laser cutter hint hint)
  • Automatically generating traffic by showing friendly site logos made from brass

Why a ROTARY spray etcher?


This rotary spray etcher can be built for between $50 and $100, depending on where you need to source your material. This is a lot less than the $300 plus that other spray etching machines would cost. It is also quicker and easier to build as long as someone else has made all the errors along the way FOR you.

How?


Well here is where I get to say "follow me on this remarkable journey of discovery"
 
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kirkguille8 months ago

Anybody having issues with sprayer holes getting blocked with debris? Maybe some kind of online filter may work... Working on it.

cunning_fellow (author)  kirkguille7 months ago

Only if I let the solution get very thick with spent brass and leave it unused for a long period.

With fresh ferric or any CuCl I have not had blockages.

knaster11 months ago
This instructable rules, thanks! I was wondering, for heating, is there any reason you couldn't use a glass aquarium heater? I'm currently testing out various tubes and configurations in preparation for building my own etchinator, it seems the spray tubes are pretty finicky to get going. I've tried both a 22mm OD / 15mm ID tube and a 34mm OD / 28mm ID tube and the smaller definitely doesn't work as well as the larger one - however i still can't get the larger one to spray all the way up the tube. I bought two of these motors which looks like they should be quite perfect, no? I too had problems making a good impeller, best i've tried is getting a fan like this, rip out the fan part and glue it upside down to a piece of plastic covering the bottom of the tube. Figuring out how far up the tube the water/spray is going to reach and calculating the drop of the water over distance seems really hard - any way of doing this without experimenting? I'm currently prototyping in a plastic tub but would like to migrate the project to a larger glass aquarium i bought second hand.
cunning_fellow (author)  knaster11 months ago
Yes, you can use an aquarium heater. Just make sure it is compatible with your etchant.

Is there a ring plastic at the bottom of your tube with just a hole in the center? You can't get the water to travel all the way up the tube without this ring preventing the water from going out the bottom also.
Well it's a plastic circle with a 6.35mm hole in the bottom and the fan glued as an impeller on the inside - picture attached. The impeller is the most confusing part to me so i'm not sure i did this right..
IMG_3037.JPG
cunning_fellow (author)  knaster11 months ago
At a guess I would say try increasing the size of the hole.

All my iterations where done experimentally so I can't give you any maths. However the tubes throw out a LOT of liquid and I would think that the 6.35mm hole is becoming a bottle neck.
kirkguille1 year ago
First pic! (Sorry, tomorrow i will post a better pic)
2013-07-17 18.28.23.jpg
cunning_fellow (author)  kirkguille1 year ago
Fabulous work. It almost looks radioactive with that green back lighting.

Is that CuCl etchant full density yet, or are you still using H2O2 in it?
Lol, thanks. It's CuCl + H2O2, with a white back light (so i can see when the work it's done..) ,
cunning_fellow (author)  kirkguille1 year ago
Cool. If you are after absolute best results then measure and titrate the CuCl (as per Adam Seychell guide) and go easy on the H2O2. Too high an acid and too much free oxygen causes the etchant to be very aggressive. Very high Acid and O2 will also cause a lot of fuming and will rust your motors.

It also saves money on H2O2 :)
Acid-motor issue fixed. The holes in the pvc conduit where way too high, now my motor is pretty safe from it. :)
kirkguille1 year ago
A preview of the working machine: http://www.youtube.com/watch?v=f7xyQUiLLsA
kirkguille1 year ago
Hello, thanks for this beautiful design, i'm almost done with my own etchinator with a few mods, in the next week i will be showing some pics.
bfk1 year ago
Your Instructables are top shelf there, Mr. cunning_fellow. Never new Aussies could be so creative:) More please!
cunning_fellow (author)  bfk1 year ago
We don't just spend all day saying "Crikey mate a stingray just got me"

We have to fill in the rest of our days somehow.

There is a new instructable on the burner I want to try get done for the Zing competition. However it's pretty hard slog when all your parts from digikey have to come via kangaroo.
And, I suppose, why a great sense of humour is also required. I'd put a vote in for you, but for some reason, can't bring myself to do that just yet:) Good luck. I'm looking forward to seeing it.
jgmrequel1 year ago
Total Awesome Instructable. Would love to see your through hole plating setup next
Great instructable! Could you please put up a video showing it in action?
Bri-Wiz,

It no so exciting to watch the machine run in a video. I will try do a video of its use though. I will just cut/FF/timelapse the boring "spray" part.
I know the video may seem boring to professionals but for us poor laymen it will be fascinating and inspiring especially as this is a beautifully built apparatus!
SDX20002 years ago
>If this project is well received and people seem keen I have another few projects about home brew PCB manufacturing equipment

Yes Yes Yes!
cunning_fellow (author)  SDX20001 year ago
SDX,

Stay tuned. About 10 people so far have told me they have built or are building The Etchinator and I have some feedback to improve the design.

I am also working on the write if for another few pieces of equipment at the moment.
I am in the process of constructing an etchinator, with the goal of eventually scaling it up by using a row of spray tubes with blinds between them to control the angle. I have constructed one impeller out of plexiglass, and am still trouble-shooting it, but wonder, what do you imagine the fan looking like in a perfect world? Is it still based on fluid entering through a small hole in the end, or does it pull fluid in from the sides?
Thanks so much,
Cat
cunning_fellow (author)  catbates1 year ago
Cat,

I would suggest having a look at Adam Seychells spray etcher on the way back machine.  The photos have gone AWOL, but the descriptions are all there.

Economics is not very kind to “scaling up” the design I show here.

With the spray tube etcher here there is one motor (the expensive part) per tube.  If you scale up to 10 tubes you need 10 motors.  In contrast pump/nozzle type spray etcher still only needs one pump.

Although the original motors I bought years ago where $5, recently the cheapest reliable source of motors I have found outside the US is $12.  This means a 10 tube etcher would be $120 just in motors.  Motors alone you are spending more in parts than a diaphragm pump.

Aside from the low cost of the small version, the etchinator comes out favourably because you don't need to construct a tank.  The HDPE storage crate make a very convenient liquid tight container.  If you are scaling up you are going to have to make your own PVC tank.  The Etchinator style has lost both advantages now.  It's no longer easier to build and it will be more expensive.

WRT you question about the impeller.  I am looking at axial inflow radial outflow styles.  Look at a car turbo charger photo off google to get an idea.  There is still a small inlet hole but the impeller blades come down and face forward.

Also if you DO decide to scale up the spray tube etcher, you probably don't need the blinds.  The angle issue I show in the digram on step.4 is not really about the angle of the impact causing undercutting. It is the angle of the impact having less force therefore a slower etch (poor uniformity).  Any overlap from not having “blinds” will cause faster etching.  If you just work out how far apart to have tubes to balance out the speed-up and the slow-down your should be right :)

But really I do recommend a pump version for anything much larger than what is shown.  The pump  version on a large scale will be

Cheaper
Easier to construct
Very marginally better results (Adams style, Creeds style will be MUCH worse)
Easier to automate
Thanks for the detailed response. I will look into Adam's design, and see what I can make of it. Cheers!
cunning_fellow (author)  catbates1 year ago
A few things to keep in mind if you DO build the pump version.

The pump Creed used is apparently not etchant safe and will die a horrible death without modification. (See the link in Step.1 to Adams experience with the same pump). In that link Adam recommends FloJet instead (which is the brand proto-trains used).

Hoses running outside of a containment vessel are not a great idea. Read the section “Etching tank No.4” in the proto-trains link in Step.1. Watch Creeds video and pause at 3:21. Now imagine that pressure relief hose on the OUTSIDE of the tank. That is the volume of corrosive fluid being splashed around the shop when the hoses let go.

A second PVC containment vessel that contains ALL hoses and the pumps is probably a good plan. PVC is cheap and making the outer tank will only be expensive in time. Weigh that up against time cleaning up after a spill WHEN it happens.

Finally these days if you look at that festering pit flea-bay and search for “PCB Ceramic Spray Nozzle” you actually find something. I have never bought or used these so I don't know what the quality is, but they are not too expensive to give a try.
dandumit2 years ago
regarding a sophisticated impeller/fan . There a lot of activity / enthusiasts that are building at home made 3D printers (also there is a group on yahoo). Also are available commercial services for this. On a such a printer can be made this impeller fairly easy . Also I am interested to participate on this "improvement".
Regards,
Daniel
cunning_fellow (author)  dandumit1 year ago
Daniel,

It seems there is a fair bit of interest happening. I am going to try find someone local with a 3D printer to come up with a printable design for it.

It should make easier one of the more fiddly parts of the build.

I have also had feedback from a few people to make the etcher easier to keep clean.
Tomdf2 years ago
I don't do enough etching to justify making one of these, but I just wanted to say that this is incredibly well documented and written. I also like seeing plastic used without a laser cutter (they can be such a crutch.)

Did you etch the Hackaday logo from a solid sheet? How come it doesn't get massive undercuts?
cunning_fellow (author)  Tomdf2 years ago
It gives a perfect opportunity to say to people "Doubt but not using hand tools is an art.....". It is a shame a lot of people don't think it is an art well worth their learning. Obviously entering the Hurricane contest means I would love to have a working CNC mill or a laser cutter. I am glad however that I have spent the time learning to use ruler, saw and a file.

The Hack-a-Day logo was made from the same 0.7mm (1/64") as the Instructable Robot. The lack of undercut is the "extra way big" advantage of spray etching. The droplets hitting the target at speed and close to perpendicular help etch directionality.

If you tried to do the same etch depth (0.35mm) sloshing around in a container full of liquid, you would get about 0.2mm undercut. Sloshing gives a wanted to unwanted direction of etch ratio of about 3:1 on fresh etchant down to 2:1 on spent etchant.

The Etchinator gives more like 10:1 down to 5:1. If you want better than that you are going to have to build something like Adam Seychell did.
cunning_fellow (author) 2 years ago
Thanks everyone for the positive comments.
Gregg E.2 years ago
"Mark the drill points at 6mm intervals along the first line. Mark the second line with the same 6mm intervals but offset by 2mm. Finally do the marking of the third line offset by another 2mm (4mm total)."

Making a note that the offset is vertical to better cover the item being etched would be a good idea.

An easier way to ensure the motor couplers align with the tubes would be to turn a step on them. Use a ratcheting PVC pipe cutter (a good one) and you'll have perfectly straight pipe to coupler connections.
cunning_fellow (author)  Gregg E.2 years ago
thanks, I will try draw up a diagram to clear that ambiguity up.
Forgot to mention that drilling the couplers on the lathe will make perfectly centered holes, as long as the tailstock is properly aligned.
rimar20002 years ago
WOW!
temper2 years ago
Great instructable, terrific detail and all well done.

Good old Reverse Garbage eh? They are not as good as they used to be but I have scored some nice material from them over the years. I miss them now I have moved to the country.

With respect to posting your other projects - well just call me Colonel Mustard ;-)
Aleator7772 years ago
This is very very well done! Kudos for such thorough documentation.
Orngrimm2 years ago
Wow! Just a brilliant example of a nicely done instructable complete with prior art and stuff.
Well done!
AtomRat2 years ago
I do like the concept of this rotary etching box, but I do have to ask though: If this makes small streaks like shown in the last images, how is this better than etching in a tank where the pcb is surrounded by a moving etchant, and no streaks?
I'm Australian as well, I have not found other's alike that have attempted home etching with the quality we are after ( repetitive small production i guess ) and I', glad to see another is out there somewhere! I'll 'follow' you on instructables so we can discuss further pcb, and material finding in Australia as I know this is hard sometimes
cunning_fellow (author)  AtomRat2 years ago
AtomRat,

The stripes you are referring to are in an appendix of what can go wrong if you don't build it accurately.

If you follow the plans there will be no stripes.
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