Author Topic: Etching is very slow  (Read 6061 times)

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Online IanB

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Re: Etching is very slow
« Reply #25 on: July 23, 2017, 07:00:56 am »
It really should not be necessary to do anything special to make ferric chloride work. Here's an illustration of the process from Big Clive. In his words, the etching takes "several minutes":

https://youtu.be/W_oDBp_wgJQ?t=10m
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Offline ion

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Re: Etching is very slow
« Reply #26 on: July 23, 2017, 04:14:24 pm »
Warm Ferric Chloride does etch faster, but don't heat it much past 50°C - as you approach 60°C it will start releasing HCl fumes.

Around 50°C and occasionaly rocking the etching bath, most of my boards are etched in about 10 minutes.  While room temperature Ferric Chloride will work, if you have fine traces a faster etch will probably give a better result.
 

Offline dsharp02

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Re: Etching is very slow
« Reply #27 on: July 23, 2017, 04:42:52 pm »
Quote
I use the pre-mixed Ferric Chloride solution from MG Chemicals in a photographic tray, float the tray in a sink of hot water and rock it back and forth.  Takes 15 to 20 minutes.  When it's done, I pour as much as possible of the FeCl back in the bottle.
I'm also using MG Chemicals Ferric Chloride.  I'm afraid of putting the used etchant back into the bottle.  I worry that bits of the paint I used as resist will contaminate the solution.  For now I'm just keeping the used etchant in a separate container.

Quote
(To prepare the boards, I use the MG Chemicals positive resist boards, laser or inkjet printer on transparencies and a single UV tube about 6 inches over the board for their recommended exposure time, then their developer diluted as recommended.)

If the etching (or developing come to that) gets slow, it's time to replace the solutions.

So, if etching is taking longer than 30 minutes at room temperature, there is something really wrong...

Hrm... I really don't know what's causing the issue.  It take more than 20 minutes just to get the etch started to the point where there are areas starting to show through.

Dave

Edit:  I've added a picture of my board.  The upper middle seems to be mostly clear, but the long traces on the left side and the traces for the H-bridge in the bottom center are not completely etched.
« Last Edit: July 23, 2017, 05:18:25 pm by dsharp02 »
 

Offline KL27x

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Re: Etching is very slow
« Reply #28 on: July 24, 2017, 12:53:02 am »
Quote
I'm also using MG Chemicals Ferric Chloride.  I'm afraid of putting the used etchant back into the bottle.  I worry that bits of the paint I used as resist will contaminate the solution.  For now I'm just keeping the used etchant in a separate container.
FYI, I wouldn't worry about that, at all. I read somewhere that aside from contamination with solvents, there's not much you can do to screw up ferric chloride etchant. I would add soap to the list, if you use a bubbler. And w/e is in Kemtech 15% muriatic acid.

Flecks of paint, leaves, twigs, dust, don't really matter. I keep a lid on my tank, but it is outdoors. I get some occasional debris. I pick or strain it out when the moon is blue.

I suspect OP had issues with paint re-adhering to the board, as others have pointed out. But if you have tried clean copper and it's still slow, a couple thing I'm gonna do. Check the thickness of your copper. If you're using 2+ oz pour, there's nothing necessarily wrong. The etching will be slow and uneven.

If you're using 1oz or lower, and/or you feel like the ferric is just too slow, add some hydrochloric acid. The ferric needs a little bit of excess HCl. If it doesn't have any (and pure lab grade ferric won't have any), it will etch fine for the first tiny bit, but it will quickly slow down. If you are using only a little part of your etchant, and keeping the rest in the bottle, you are setting yourself up for that problem. Some peeps seem to prefer this method, seeing it as less wasteful. I've seen where some people are putting a little Ferric on a sponge and wiping the board till its done. Then tossing it. And thinking they found the best way to use it without "wasting" any. This is obviously retarded AFAIC. This is just a dude who happened to use a half oz board and thought he discovered magic.

If you don't want to waste it, just use the whole 1L* bottle of it. And pour it back in a bottle or next time. Trying to use a little of it at a time and then disposing of it is more wasteful, in the long run.

*Or w/e volume will reasonably fill your container without fear of spilling. You can try the whole, put the pcb in a bag and a few mL or ferric, but this is not creating less mess or using less ferric. This is just dumb. 
« Last Edit: July 24, 2017, 01:27:23 am by KL27x »
 

Offline M4trix

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Re: Etching is very slow
« Reply #29 on: July 24, 2017, 01:20:42 am »
@dsharp02,

I don't wanna sound like a smartass but do yourself a favor... ditch the ferric-chloride etchant and use 'modern' etchants like sodium persulfate or HCL+ hydrogen peroxide. The second one doesn't even need to be heated. The downsides of ferric-chloride are already mentioned in this thread so I'll skip that part. If you want to use HCL+HP then this is my recipe which always work:

For 1L etchant -->

700ml - destilled water
250ml -  35% HCL
50ml - 30% hydrogen peroxide

The only downside of this etchant is a nasty odor like vomit.  ;D         
« Last Edit: July 27, 2017, 08:23:41 pm by M4trix »
 

Offline KL27x

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Re: Etching is very slow
« Reply #30 on: July 24, 2017, 01:31:20 am »
If you have 30% peroxide, this is a good etchant. But I wouldn't mix up a liter at a time, unless I were going to do a big stack of boards. With HCl and peroxide, you really don't want to mix up more than you need and try to save it for next time. Use just enough to do your boards, so it saturates with cupric chloride. And you will have to use less of your 30% peroxide to restore it for continued use.

The peroxide starts to spontaneously bubble off into the atmosphere as soon as you mix it with HCl. Next time you use it, you add more peroxide, and it works, again. I suppose it is practical if you have easy access to cheap 30% peroxide.

If you mix up just enough to get by, you will increase the copper concentration in the solution. (It will get greener). And next time you add peroxide, some of it will instantly be transferred to the copper I in the solution, turning it to copper II. And this etches copper. And it doesn't spontaneously release that O2 to the air.
« Last Edit: July 24, 2017, 01:42:23 am by KL27x »
 

Offline M4trix

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Re: Etching is very slow
« Reply #31 on: July 24, 2017, 02:27:51 am »
if you have easy access to cheap 30% peroxide.

Unfortunately, here in Croatia you can find 30% hydrogen peroxide only on the black market or if you have a friend who works in a hair salon. The drugstores sell only 3%. Well, there were times when you could buy 30% peroxide in drugstores but the lady behind the desk asks for your ID and asks for what purpose you're buying peroxide. Sometimes they give it without questions but that's rare.  :palm:   
 

Online IanB

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Re: Etching is very slow
« Reply #32 on: July 24, 2017, 02:47:56 am »
Unfortunately, here in Croatia you can find 30% hydrogen peroxide only on the black market or if you have a friend who works in a hair salon. The drugstores sell only 3%. Well, there were times when you could buy 30% peroxide in drugstores but the lady behind the desk asks for your ID and asks for what purpose you're buying peroxide. Sometimes they give it without questions but that's rare.  :palm:

Ah, but that's not really a problem. 50 ml of 30% peroxide contains 15 ml of peroxide (approximately). However, 500 ml of 3% peroxide also contains 15 ml of peroxide. So you just adjust the proportions in the above recipe:

250 ml - distilled water
250 ml - 35% hydrochloric acid
500 ml - 3% hydrogen peroxide solution

Next problem: is 35% hydrochloric acid available where you are? Here in the USA hardware stores sell it, but in Europe, I'm not so sure. Probably the best bet is pool supply stores, since HCl can be used for pH control in pools.

To me, this all starts to sound a bit complicated given that ferric chloride etching solution is so readily available.

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Online sleemanj

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Re: Etching is very slow
« Reply #33 on: July 24, 2017, 03:00:54 am »

Next problem: is 35% hydrochloric acid available where you are?


Way too strong if you ask me, that will be fuming.

I use 15%, which should be pretty easy to come by in most places, hardware stores, pool supplies, paint supplies, concrete driveway people...  Peroxide is typically harder to get in quantity.

By the same token as H2O2, exchange water for less concentrated HCl in the first place, all the water is doing is diluting.

You don't need to be precise about this stuff.  Take HCl, dilute until not fuming if it is, put PCB in HCl, add peroxide a little dribble at a time and watch the reaction.

Yeah I know, one should really "do like you ought'a, add acid to water", but in this case it's not practical, just don't go dumping a pile of H2O2 in at once, especially if it's 30% (excitement for sure!), a little dribble, mix, observe, repeat until the reaction is working at a rate you are comfortable with.  It shouldn't be giving off clouds of fumes and foaming up like an angry sea covering your bench in corrosive juices, it should just sit there quietly with some little bubbles forming on the surface of the PCB.

As above, save the etchant, use it again next time, following the same add-H2O2 and observe procedure, you probably won't need much.

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Offline M4trix

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Re: Etching is very slow
« Reply #34 on: July 24, 2017, 03:21:31 am »
Well, that's why I stashed on time some 40-50 liters of 35% HCL and 6 liters of 30% peroxide. Just in case if bad time comes.  ;)
 

Offline orin

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Re: Etching is very slow
« Reply #35 on: July 24, 2017, 03:45:53 am »
Quote
I'm also using MG Chemicals Ferric Chloride.  I'm afraid of putting the used etchant back into the bottle.  I worry that bits of the paint I used as resist will contaminate the solution.  For now I'm just keeping the used etchant in a separate container.
FYI, I wouldn't worry about that, at all. I read somewhere that aside from contamination with solvents, there's not much you can do to screw up ferric chloride etchant. I would add soap to the list, if you use a bubbler. And w/e is in Kemtech 15% muriatic acid.

Soap, bubbler?  Is this from experience?

Quote
If you don't want to waste it, just use the whole 1L* bottle of it. And pour it back in a bottle or next time. Trying to use a little of it at a time and then disposing of it is more wasteful, in the long run.

*Or w/e volume will reasonably fill your container without fear of spilling. You can try the whole, put the pcb in a bag and a few mL or ferric, but this is not creating less mess or using less ferric. This is just dumb.


There's a bit of a tradeoff for me - the more FeCl in the photographic tray, the less floating the tray in hot water warms it up... but with less FeCl there, it might weaken faster...  For the size of boards I do, it's a non-issue - and flood fill ground planes mean there's not much Cu to etch anyway!

Orin.
 

Offline lowimpedance

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Re: Etching is very slow
« Reply #36 on: July 24, 2017, 03:46:57 am »
Well, that's why I stashed on time some 40-50 liters of 35% HCL and 6 liters of 30% peroxide. Just in case if bad time comes.  ;)
Watch the shelf life of your peroxide !, it will slowly decompose when sealed, much faster after being opened.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline KL27x

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Re: Etching is very slow
« Reply #37 on: July 24, 2017, 04:37:43 am »
Quote
Soap, bubbler?  Is this from experience?
I scrub my boards with a drop of dishsoap and coarse stainless steel wool. And I use a very thin vertical tank (slightly less than 3/4" thick, about half a liter of cupric chloride) hooked up to an air compressor to give a lot of aeration. Depending on the airflow/pressure I give it, I can get 2 or 3" of head WITHOUT neglecting to carefully rinse all the dishsoap. And you only make that mistake once.

If I'm doing a tall board and there's not quite enough etchant, I can just turn up the air. There's a good inch or so of height added just from the density of bubbles swirling in it, not even including the foamy head (which appears to etch at least as fast as the liquid fraction).

This vertical tank has better throughput than a large tank I had once made using an igloo cooler running off fish tank bubblers and holding half a gallon of etchant.


Quote
Ah, but that's not really a problem. 50 ml of 30% peroxide contains 15 ml of peroxide (approximately). However, 500 ml of 3% peroxide also contains 15 ml of peroxide. So you just adjust the proportions in the above recipe:

250 ml - distilled water
250 ml - 35% hydrochloric acid
500 ml - 3% hydrogen peroxide solution
But if you have only 3% peroxide, you really want to take care to not mix up too much of this stuff. If you mix up a liter to etch a single 2"x3" board, you might as well throw it out when you're done. Next time you use it, a month or two later, it will just be diluted HCl. You won't be able to revive it, easily. The more peroxide you add, the more you dilute what you mixed up in the first place. FWIW, BP of peroxide is around 150C. So it is possible to boil 3% peroxide to make a higher concentration. But that would be a wee bit of extra work. This was the point I was trying to make. W/e you mix up, if you etch as much copper as you can into it, it will work better (albeit much slower) the next time around. Because it will have a higher concentration of cupric chloride in it. If you build a bubbler tank, you won't ever use peroxide and HCl, again. It's a pain due to the concentration of corrosive fumes, and it is a very innaccurate etchant, relatively speaking.

Quote
Watch the shelf life of your peroxide !, it will slowly decompose when sealed, much faster after being opened.
Even the lower % stuff has buffers added to keep it stable. The higher purity stuff, yes, take extreme care. Any foreign debris that gets in there will catalyze the decomposition. Think Mentos and Diet Coke.
« Last Edit: July 24, 2017, 05:22:33 am by KL27x »
 

Offline dsharp02

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Re: Etching is very slow
« Reply #38 on: July 24, 2017, 12:13:11 pm »
I think I'm going to use my vacuum sealer to create a sealed bag like in Clive's video.  A couple of dowels, and 3D-printed clips and I think I'll have the messiness bit sorted.

I'm going to try etching piece of a bare pcb and see if that works any faster.

I tried to use sharpie ink as a resist, but the laser does not seem to ablate it very well.

 

Offline oldway

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Re: Etching is very slow
« Reply #39 on: July 24, 2017, 08:13:56 pm »
@dsharp02,

I don't wanna sound like a smartass but do yourself a favor... ditch the ferric-chloride etchant and use 'modern' etchants like sodium persulphate or HCL+ hydrogen peroxide. The second one doesn't even need to be heated. The downsides of ferric-chloride are already mentioned in this thread so I'll skip that part. If you want to use HCL+HP then this is my recipe which always work:

For 1L etchant -->

700ml - destilled water
250ml -  35% HCL
50ml - 30% hydrogen peroxide

The only downside of this etchant is a nasty odor like vomit.  ;D       
The solution can be used again dozens of times, just add a little peroxide each time.
I noticed that the rapidity of the reaction depends mainly on the amount of peroxide added and little on the acid concentration.
But whenever peroxide is added, the solution is further diluted.
It is therefore advantageous:
-to use concentrated peroxide
- not to dilute too much the solution at the first use.
 

Offline M4trix

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Re: Etching is very slow
« Reply #40 on: July 26, 2017, 10:48:07 pm »
just don't go dumping a pile of H2O2 in at once, especially if it's 30% (excitement for sure!)



 :palm:  ;D
 

Offline cdev

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Re: Etching is very slow
« Reply #41 on: July 27, 2017, 12:29:32 am »
Try:

Toner transfer

Vinegar
Hydrogen peroxide
Salt. Add more salt to get more etching.

nail polish remover for cleaning off the board at the end.

Then treat it as you would with any other just etched PCB
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Online IanB

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Re: Etching is very slow
« Reply #42 on: July 27, 2017, 03:06:00 am »
I still haven't found out what is being given off in that video. It obviously isn't Chlorine gas or we'd have heard about it. I'm thinking it must be water vapor as steam. I think if it was me I'd be using less concentrated peroxide just to slow things down a few notches.

It's oxygen, from the peroxide. Basically, it is wasting the peroxide solution since the oxygen is bubbling off instead of helping to dissolve the copper. It suggests to me that a more dilute peroxide solution would be satisfactory.

Note: a common high school chemistry experiment is to add a drop of blood to some hydrogen peroxide. The blood catalyzes the decomposition of the peroxide solution and causes a similar reaction.
« Last Edit: July 27, 2017, 03:09:17 am by IanB »
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Offline uwezi

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Re: Etching is very slow
« Reply #43 on: July 27, 2017, 10:11:04 pm »
Try:

Vinegar
Hydrogen peroxide
Salt. Add more salt to get more etching.


Don't think that you are environmentally friendly or safer just because you use vinegar instead of "chemicals" such as hydrochloric acid, ferric chloride or sodium persulfate. Especially the copper salts formed in any of these etching methods are environmental hazards and need to be taken care off properly.

Also in Europe - at least Sweden and Germany - it is much easier to buy ferric chloride (if you want to stain yourself, your clothes, everything) or sodium persulfate than hydrogen peroxide.
 

Offline cdev

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Re: Etching is very slow
« Reply #44 on: July 28, 2017, 03:47:40 am »
I have a plastic bottle I pour the liquid into when I am done and then it just evaporates leaving some solids on the bottom. All the PCBs Ive ever done's (maybe a few dozen ;) etchant's remnants are in the bottom of this bottle and its still not that deep.. Unless you did it commercially, even if the boards you made were much much larger than the tiny ones I usually make I bet a single plastic bottle would probably hold a whole lifetime's worth of leavings.


Quote from: uwezi on Today at 16:11:04>Quote from: cdev on Yesterday at 18:29:32
Try:

Vinegar
Hydrogen peroxide
Salt. Add more salt to get more etching.


Don't think that you are environmentally friendly or safer just because you use vinegar instead of "chemicals" such as hydrochloric acid, ferric chloride or sodium persulfate. Especially the copper salts formed in any of these etching methods are environmental hazards and need to be taken care off properly.

Also in Europe - at least Sweden and Germany - it is much easier to buy ferric chloride (if you want to stain yourself, your clothes, everything) or sodium persulfate than hydrogen peroxide.
"What the large print giveth, the small print taketh away."
 


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