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SDIY PCB Etching
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Author SDIY PCB Etching
decaying.sine
I have been working on my DIY etching so that I could build some modules with available PCB artwork.

Here is a description of my strategy and some pics of the results.

I'm satisfied with the first batch of etching, but not entirely happy with my UV lamp and the tinning process. I still have to drill the PCBs. I have to order tungsten carbide bits. There are many degrees of freedom in doing this so it really depends a great deal on your individual setup and approach.

I etched the Buchla 258 (Verbos), Buchla 291 (Verbos), Buchla 230 (technik/2012), Yusynth S & H/Noise Gen, Yusynth ARP 4072, Yusynth Quadrature LFO, ACS CV Recorder, among others.

Sorry for so many pictures! I am about 50% satisfied with results at this point. There is a lot of technique and individual selection that goes into the process, and that makes it a pain.

Steps:
1. Find artwork. That's easy. Check MW and EM various online sites. Search for Verbos, Yusynth, etc.
2. Printed on www.smrsoftware Premium Vellum. I first used a very fancy HP laser printer at work but didn't like that the it didn't appear VERY black. I decided to use my HP Officejet Pro 8000 at home. I adjusted the settings to choose "card stock media" and maximum ink with maximum drying time. Basically, I wanted as much ink on the artwork as possible. Drying time for artwork with tons of ink was minimum of 1 hour and maximum of days.
3. PCBs with positive photoresist were used (MG Chemicals). PCBs with resist are shown in pics below. Etchant was 240 grams of ammonium persulfate in 1.5 liter of tap water (generally a typical concentration. probably on the low side).
4. Etchant tank was constructed of plastic tupperware, drilled holes for "air tubes." Air tubes were inserted and connected to air compressor typically used for aquariums. Drilled holes were sealed with epoxy from Home Depot. An aquarium heater was inserted (dropped) into the tank. Setting was for 88 Celsius (maximum).
5. Artwork laid on top of PCB with plastic "shield" on top to weigh down and ensure no air gaps between artwork and PCB. Glass was added to plastic shield to increase weight and prevent UV "undercutting" on artwork. This method resulted in no undercutting.
6. UV exposure ranged greatly in time. I used a 15W UV bulb and rack purchased from mouser. This seems much "weaker" than many of the major DIY exposure methods that use many bulbs for quicker exposure. I got "okay" results at first with 15 minutes exposure, but in the end decided I liked about 45 minutes of exposure with my setup, which resulted in fairly quick development and no undercutting.
7. PCB were placed under UV lamp in darkness and exposed for approximately 35-45 minutes.
8. PCB's were then placed in a solution of NaOH:tap water (10:1, MG Chemicals) and agitated with a foam brush. Development varied, but generally was 3-8 minutes depending on the board.
9. Etching time varied wildly. This is probably due to the relatively low concentration of etchant, heating in the tank, and other variables. I checked the status every 10 minutes.
*a key for success seems to be very good masking at the UV exposure point. I had much better success overall when I UV exposed a good 20 minutes more than I thought and developed the board in NaOH more than a few minutes longer than I thought. There are a couple subtle tricks to this it seems, but it surely depends on the individual setup.
10. After etching the PCB can be nicely stored prior to tinning with the photo resist layer still on top of the copper.
11. Prior to tinning... Photoresist removed with acetone and very good scrubbing. Plastic bristle brush or steel wool depending on the occasion. It's important to get all the photoresist off or it will not tin well or quickly.
12. Tinnit was used for non-electroplating tinining method. Tinnit powder was dissolved in tap water on the stove at temperature of 140-150 Fahrenheit. Boards were placed in tinnit solution until they had nice "coverage." Usually I left them in for 20-30 minutes. The longer they remain in the solution, the shinier they get. I had some trouble with this step because I didn't scrub off the photoresist well enough for the first board. I also scorched the PCB on a couple of occasion, which required steel wool scrubbing.

Picture documentation is below.





















discomicke
Thanks a lot for this info!

Have you also tried the press-n-peel paper method ? Seems a lot easier
Luka
nice work

i prob should use UV method
Pnp can be frustrating some times

I looked for tinning liquids down here and they were too expensive to make it worthwhile. You had to purchase large amounts and i just couldnt justify expense.
dude
oh man, it is so nice to see all this that you have talking about! and of course nice to see your daughter too!

i can still hear the bubbles from that tank hyper

so fucking cool man. you win the cool award.

i don't normally do this but:

goatse.cx
dude
oh and you forgot the most important picture
webb
Nice results!

Press N Peel method (or printing to high gloss paper) always worked for me but I hated dealing with chemicals. ferric chloride stains, pain to dispose of. ammonium persulfate is a pain to dispose of. Muriatic Acid + Hydrogen Peroxide is the best etchant since it's rechargable by inserting oxygen into the solution.

Got tired of it all and went the cnc route. Not only can I do pcbs but I can also do front panels. Haven't looked back since. Now I just have to dispose of the chemicals. smile
decaying.sine
I have never tried press-n-peel. I thought it would be fun to do the UV route. The single UV lamp works but takes longer. I like the idea of using a scanner bed to mount 4-5 UV lamps and then the spongy thing on the lid helps press the artwork up against the resistive surface to get rid of gaps. It seems to be a fairly common approach.

The muriatic acid and hydrogen peroxide sounds like a great idea. I wonder if you can recharge it just by bubbling oxygen from the aquarium pump and hoses that I already attached to my tank? Or, does it have to be a very high concentration O2 gas? I'll have to look into that because disposal is really annoying.

Did you build your own CNC setup, webb?

Homebrew PCB yahoo group is really active and there are tons of good threads there for the hardcore!
webb
decaying.sine wrote:

The muriatic acid and hydrogen peroxide sounds like a great idea. I wonder if you can recharge it just by bubbling oxygen from the aquarium pump and hoses that I already attached to my tank? Or, does it have to be a very high concentration O2 gas? I'll have to look into that because disposal is really annoying.


Just by letting it sit there it will recharge itself but you certainly can use an aquarium pump to pump air into it and it will speed up the process. You will be able to tell by the color when it's ready to be used again.

decaying.sine wrote:
Did you build your own CNC setup, webb?

Yup. Built it as a kit a few years ago.
decaying.sine
I think I'll officially move to HCL and Hydrogen peroxide. A CNC kit sounds cool. I'll have to read about that.
discomicke
http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Mill ing-Machine/ Would love to attempt to build this for pcb's and frontplanels someday
CJ Miller
How had I missed this thread so far? Great to see Brian's setup... and the unicorn! eek!

I was searching for photoresist. Last fall I decided to really address the challenges of doing PNP Blue and making some boards. I definitely have gotten some decent results, but not consistently. The detail has always been better towards the center of my boards, and sometimes a bit too blurry on the edges. And there have been occasional lines or creases, probably from the PNP moving a bit, despite being taped down. It seems a bit wasteful that the PNP are one-use only. And making some decent boards has gotten me wanting to have finer pitch options for SMT and traces between pins.

A couple weeks ago I was lucky to score a cheap ultraviolet exposure box, it is about 18"x12", so I can hopefully use it for even large PCBs and maybe photoresist panels for 17" boats. Naturally, UV this strong (180 Watts) requires extreme caution to avoid damaging skin and eyes.

Speaking of caution, I already have NaOH for developing. I'll need to figure out exactly how much to dilute it. Last time I tried using it, my PH strips completely dissolved. The lye is in pellet form.

What will probably require the most fussing with is the resist. I have far too much PCB material here to warrant spending more for pre-sensitized boards. I imagine that applying resist myself will be troublesome, mostly because hardly anybody seems to do it. I would be especially eager to hear accounts from DIYers here about experiences applying photoresist to copper. What is it composed of?

For etching I have been using CuCl in a Pyrex lasagna-type dish I bought for this purpose. I am probably going to use a vertical tank instead from now on. Keeping the etchant charged with the vertical action of settling copper and rising bubbles seems more optimal to me. Hoping to find a heavy glass tank about 12"x12"x2", I don't know where yet.
Pfurmel
I have been using PNP with good results. Contrary to popular belief, the sharpie works a charm to touch up anything that was missed.
I clean the copper clad as much as possible with alchohol prior to applying the PNP.
I have heard that glossy magazine paper works just as well, I am going to try it next time as PNP isn't all that cheap.

I would love to build one of those cnc machines, ferric chloride is not the nicest stuff to have around.

Where do people buy their copper clad boards? Just wondering if there is anywhere cheaper than farnell.
Dr. Sketch-n-Etch
I cut my boards on an old paper cutter (guillotine) they were throwing away at school. Works great!

I prepare boards by sanding the edges smooth, then wiping the copper with an acetone-soaked paper towel to remove oils, then polishing with fine steel wool, then wiping with acetone again.

I use PnP Blue. The big secret: apply gentle-yet-firm pressure with the iron -- don't push too hard. Also, it is very important to have the board on a flat surface. I put a piece of paper between the PnP and the iron, and I move the iron in a circular motion all over the board for a couple minutes.

I use a superfine-tipped Staedler LUMO permanent marker for touchups. I find that the ground trace I always put around the edges of my boards always needs a few little touchups. I use a ruler to get nice edges. Having a flat ironing surface and following my ironing tips alleviates most of this, however.

I also use HCl/H2O2. I've been using the same bottle of solution for three years. Every couple of times, I add a few splashes of HCl, and every time I add a tablespoon or so of H2O2. I wear one rubber glove (again, the same one for three years) and just swish the board around with my gloved hand for a few minutes. Slow gradual etching is best. If it's done in 30 seconds, then your etchant is too strong and you will get ragged traces, as the etchant goes underneath the edges of the masking. The reaction between O2 and CuCl is very rapid, so just swishing the solution around will do to recharge it.

After etching, I leave the masking on until I am done drilling, as this protects the copper cladding and also aids in aiming the drill bit into the centre of the hole.

For drilling, I use #68 for most components (I buy these by the dozen from Thomas Skinner), #60 for pin connectors, 1/16" for MTA-156 power headers, and 1/8" for mounting holes. Set the drill press to the highest speed. My 1/10" grid layout scheme really facilitates drilling. I just go down each row lengthwise. I have also found that I can scrape the business side of the board (lightly) against the straight edge of my steel drill press table to knock off the little edges which form around the holes when the drill bits start to get dull. This extends the life of the bits enormously.

After drilling is complete, I wipe off the masking with an acetone-soaked paper towel, then polish the copper again with fine steel wool, then tin the copper with Liquid Tin. This takes about 30 seconds. Then I rinse the board in hot tapwater and dry it off. When I'm ready to solder, I give it one more very very light polishing with steel wool -- enough to make the surface accept the solder easily, but not enough to rub off the tinning (which is very thin).

Lastnight, I cut, printed and etched three Korgo III boards in about one hour. Tonight I'll drill them all -- that will take about an hour and a half (they're big boards with several hundred holes each). Tomorrow night I'll install the wire jumpers (yes, I'm that nice of a guy). It's a lot of work for $35 each, but what can I say? It's a hobby.
Peake
I love the pic of you waiting in agitated expectation...and don't let the munchkin touch the bare copper! Skin oils prevent tinning wink

I've got two UV lamps now, to speed exposure. I've seen DIY directions for mounting and wiring four of them on a board, and even one inside an old computer shell.

Someone here turned me on to Liquid Tin, which works far better than Tinnit, requires no heating, stores well, etc.

After I'm done with a board and have it tinned, I'll often tin further it with a soldering iron and solder...

Success to you!
L-1
Quote:
12. Tinnit was used for non-electroplating tinining method. Tinnit powder was dissolved in tap water on the stove at temperature of 140-150 Fahrenheit. Boards were placed in tinnit solution until they had nice "coverage." Usually I left them in for 20-30 minutes. The longer they remain in the solution, the shinier they get. I had some trouble with this step because I didn't scrub off the photoresist well enough for the first board. I also scorched the PCB on a couple of occasion, which required steel wool scrubbing.


Can you explain in details about this alloy?
I use Rose's alloy but this process isn't strong side of my technology.

Ioan
A little bit of knowledge I found regarding printing films for UV exposure on inkjet printers. Has to be tested and I've only got a laser printer, but here it goes:

Print using green rather than black. The theory behind is that green (combined yellow and cyan pigments) should work better than black.
- yellow pigment is a "natural" UV filter
- many cyan inks contains UV inhibitors (probably because the pigment in it tends to be the first one to vanish after exposure to sunlight)

Cheers !
Dr. Sketch-n-Etch
L-1 wrote:
I use Rose's alloy but this process isn't strong side of my technology.

That's pretty cool! Can you explain briefly how you do this with Rose's alloy? How do you get uniform coverage? (Thanks in advance!)
L-1
This alloy melts at 96C. I put it in a bowl (pictured), add water and a bit of liquid soap (I belive it helps to increase boiling temerature) and heat on a stove. Then I rub etched board a bit with thin abrasive paper, then a bit with orthaphosphoric acid. Then I put my board into boiling water with liquid Rose's alloy and cover board with this alloy using short brush, then remove excesses with instrument shown (made from windscreen wiper). It's all.
I etch boards in this bowl too, on a stove to accelerate the process.
CoreyC
Pfurmel wrote:

I have heard that glossy magazine paper works just as well, I am going to try it next time as PNP isn't all that cheap.


I use glossy magazine paper when I etch boards and it does work great as long as you can get your heat to transfer evenly onto the board.
Dr. Sketch-n-Etch
I saw a demo on the web where the guy added one tiny little bead of Roses alloy to a can of boiling water, along with some citric acid. Then he put the board into the water and it was tinned. It looked great. He rubbed the traces with some soft implement in the water, ostensibly to spread the alloy around. It looked great.

My initial impression was that the alloy bead dissolved in the water, but maybe not. seriously, i just don't get it
L-1
Quote:
My initial impression was that the alloy bead dissolved in the water, but maybe not.


No, of course no.
Dr. Sketch-n-Etch
L-1 wrote:
Quote:
My initial impression was that the alloy bead dissolved in the water, but maybe not.


No, of course no.

Well, the product I use for tinning called "Liquid Tin" is a solution of tin in fluoboric acid with a bit of thiourea as an electroless plating aid. And, citrate is a strong complexing agent for many metals (such as Fe(III)). However, I do like the idea of rubbing the metal directly on the traces. Why couldn't the PCB simply be heated with an iron and the metal rubbed directly on it? (Perhaps this would be messier.)
L-1
Quote:
Why couldn't the PCB simply be heated with an iron and the metal rubbed directly on it? (Perhaps this would be messier.)


I did so earlier but I love when result of my work is clean & tidy.
glitchpop
This is a great thread. Thanks for documenting your process so well. Inspires me to have another go at etching my pnp attempts ended in waah
Dr. Sketch-n-Etch
I saw a video on the interwebz the other day (sorry, no link... I'm too lazy to go find it again) and the dude was transfering from shiny paper (not PnP blue) to very thin PCB material (it was flexible) using a laminator. It appeared to work perfectly. I've got enough practice with ironing PnP now to get it 95% right, but I do have a laminator (from my abortive attempts at making DecalPro dry transfer decals for front panels). I'm wondering if it would work with regular old thick PCB material?
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