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Thread

Experiments with ultrasonics and vibration etching

2013-10-19 by <fred27murphy@...>

There was a thread on here about using ultrasonics to assist etching, but it went off topic and fizzled out. So I decided that the only way to find out if it worked was to give it a go.

I decided not to confuse things with the quality of the board exposure (I use presensitised boards) so my test boards were just 1.5cm square pieces of uncoated copper clad. I can't find the thickness of the copper (Maplin ref HX00A), but it's a comparative test so I don't suppose it matters.

I mixed up some fresh ferric chloride (with a dash of citric acid) and tried the following:

- Just a bit of sloshing in a small plastic container

- Placing the container in an ultrasonic cleaning bath (James 7050 50W) full of water.

- Using a small ziplock bag of etchant in the same bath in case the container absorbed too much of the ultrasonic

- Attaching the board to the end of a small cheap AAA battery powered electric toothbrush.

I kept the temperature around 42C. I had a thermometer, but it wasn't an accurately temperature controlled experiment.

The results:

Sloshing - half of the copper had gone around 12 minutes, all at 13:30.

Ultrasonic in container - pretty much the same

Ultrasonic in ziplock - looked like it was doing better with patterns of bubbles on the board, but pretty much the same.

Toothbrush - half by 5:00 and all by 8:00

So there you have it. The Ultrasonic bath is pretty much a waste of time. Also it's small and as the bath is stainless steel it needs to be protected from the etchant with an inner container. That reduces the working size further.

The toothbrush (Oral B pulsar - 2 for about £7) worked surprisingly well. I suspect it wouldn't make as much difference on a larger board. The small board on the end of the brush meant it could vibrate it easily. To be honest it's a good way to hold the board anyway. I cut of the bristles and drilled a hole for a cable tie.

If it had been a success my next step would have been to see how the resist stood up to ultrasonics, but there seems little point.

Re: [Homebrew_PCBs] Experiments with ultrasonics and vibration etching

2013-10-20 by ctech

"Ultrasonic in ziplock" Highly dubious that the attenuation of air inside the bag is low enough for this to have a chance to work at all...

Can you coat the emitter with something and do it without plastic bag?

How does the power level and frequency of your emitter compare with commercial cleaners?

Keep experimenting!

Btw I etch 1oz copper in 4 minutes with a standard bubble ferric chloride setup....

On Sat, Oct 19, 2013 at 8:53 PM, <fred27murphy@...> wrote:

There was a thread on here about using ultrasonics to assist etching, but it went off topic and fizzled out. So I decided that the only way to find out if it worked was to give it a go.

I decided not to confuse things with the quality of the board exposure (I use presensitised boards) so my test boards were just 1.5cm square pieces of uncoated copper clad. I can't find the thickness of the copper (Maplin ref HX00A), but it's a comparative test so I don't suppose it matters.

I mixed up some fresh ferric chloride (with a dash of citric acid) and tried the following:
- Just a bit of sloshing in a small plastic container
- Placing the container in an ultrasonic cleaning bath (James 7050 50W) full of water.

- Using a small ziplock bag of etchant in the same bath in case the container absorbed too much of the ultrasonic
- Attaching the board to the end of a small cheap AAA battery powered electric toothbrush.

I kept the temperature around 42C. I had a thermometer, but it wasn't an accurately temperature controlled experiment.

The results:
Sloshing - half of the copper had gone around 12 minutes, all at 13:30.

Ultrasonic in container - pretty much the same
Ultrasonic in ziplock - looked like it was doing better with patterns of bubbles on the board, but pretty much the same.
Toothbrush - half by 5:00 and all by 8:00

So there you have it. The Ultrasonic bath is pretty much a waste of time. Also it's small and as the bath is stainless steel it needs to be protected from the etchant with an inner container. That reduces the working size further.

The toothbrush (Oral B pulsar - 2 for about £7) worked surprisingly well. I suspect it wouldn't make as much difference on a larger board. The small board on the end of the brush meant it could vibrate it easily. To be honest it's a good way to hold the board anyway. I cut of the bristles and drilled a hole for a cable tie.

If it had been a success my next step would have been to see how the resist stood up to ultrasonics, but there seems little point.

Re: [Homebrew_PCBs] Experiments with ultrasonics and vibration etching

2013-10-20 by Jan Kok

Thanks for reporting those results. I would suggest/request that you try "washing" the board with etchant using a small piece of sponge.

I've tried that, using a soft amber colored plastic (polyethylene?) foam sponge and it seems to work maybe twice as fast as the sloshing method.

RE: Experiments with ultrasonics and vibration etching

2013-10-22 by <fred27murphy@...>

Thanks for your comments. It's good to know that people on here are interested in more than just how to do toner transfer.

I think the ziplock bag would have had minimal attenuation. Whilst there was a little air in it, it was above the waterline of the bath. I suspect the rigid plastic container would have attenuated more. The cleaner claims to be 50W and 45kHz. I may make a bubble etch tank (or maybe even spray) but thought I'd try something different.

If it looked like it made any difference I would consider modifying the cleaner or coating the bath, but as it appeared to be nothing it would seem a bit pointless to destroy it.

I tried the sponge technique when an etch started well but then seemed to stop. It worked well, but definitely affected the thinner tracks and small text. I used photoresist boards so perhaps a little more delicate than toner.

Fred

---In homebrew_pcbs@yahoogroups.com, <jan.kok.5y@...> wrote:

Thanks for reporting those results. I would suggest/request that you try "washing" the board with etchant using a small piece of sponge.

I've tried that, using a soft amber colored plastic (polyethylene?) foam sponge and it seems to work maybe twice as fast as the sloshing method.

RE: RE: Experiments with ultrasonics and vibration etching

2013-10-29 by <andrewm1973@...>

Fred,

I use both positive photoresist (pre coated boards) and negative photoresists (laminated at home).

The positive resist is thin and fragile. It does not hold up to the sponge technique. In fact it gets erroded noticeably by my rotary spray etcher if I am using old ferric that had had much brass in it.

The negative photoresist is much more robust. it actually takes some effort with a sharp knife to scrape it away.

---In Homebrew_PCBs@yahoogroups.com, <homebrew_pcbs@yahoogroups.com> wrote:

Thanks for your comments. It's good to know that people on here are interested in more than just how to do toner transfer.

I think the ziplock bag would have had minimal attenuation. Whilst there was a little air in it, it was above the waterline of the bath. I suspect the rigid plastic container would have attenuated more. The cleaner claims to be 50W and 45kHz. I may make a bubble etch tank (or maybe even spray) but thought I'd try something different.

If it looked like it made any difference I would consider modifying the cleaner or coating the bath, but as it appeared to be nothing it would seem a bit pointless to destroy it.

I tried the sponge technique when an etch started well but then seemed to stop. It worked well, but definitely affected the thinner tracks and small text. I used photoresist boards so perhaps a little more delicate than toner.

Fred

---In homebrew_pcbs@yahoogroups.com, <jan.kok.5y@...> wrote:

Thanks for reporting those results. I would suggest/request that you try "washing" the board with etchant using a small piece of sponge.

I've tried that, using a soft amber colored plastic (polyethylene?) foam sponge and it seems to work maybe twice as fast as the sloshing method.