Ammonium Persulphate

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Mike
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Ammonium Persulphate

Post by Mike » Thu Mar 31, 2005 5:01 pm

I finally bought some of this stuff. Finally no more nasty Ferric Chloride! And I will be able to see the board. Rather than just putting some etchant in a bucket and setting the board in it, I'm setting up a whole etching system. With this stuff, I've got a few questions. Fisrt, is it safer to use thank Ferric Chrloride? Like does it burn as much if it comes in contact with skin? And does it stain chlothes? Second, does it go bad once the crystals are mixed with water? Third, is what I've heard that it eats right through etch resist pen, true, so if I fix any parts of a board with a sharpie it doesn't matter?<p>I also have a couple of questions about the etching tank. I'm using a fish tank air pump with a 4" long bubble wand in the bottom center of the tank. Is that enough? Also, do you think using a heater is worth the extra cost? Finally, does this destroy more than copper metal? I want to use clips to hold the pcb in the solution, and want to know if I can use metal clips, as long as they are not copper.<p>Thanks for all the help!

Dean Huster
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Re: Ammonium Persulphate

Post by Dean Huster » Fri Apr 01, 2005 5:34 am

Good for you, Mike! I love ammonium persulfate ... or more accurately, I hate ferric chloride.<p>Q:
"First, is it safer to use than Ferric Chrloride? Like does it burn as much if it comes in contact with skin?" <p>A:
I've never had any such problem with it. I've stuck my hand into tanks of the stuff with dkek dkkkk no kdk ill dlddddd eeffects. Well, I wouldn't recommend doing it on a routine basis rather than using tongs. But what happens when you stick your hand into ferric chloride? It turns yellow. Nasty.<p>Q:
And does it stain clothes? <p>A:
Compared to ferric chloride, you could use ammonium persulfate as a laundry additive, although I wouldn't. Just a comparison. It might attack a white shirt after it's been pretty well spent, so I wouldn't etch my board while wearing my Sunday-go-to-meetin' clothes.<p>Q:
Second, does it go bad once the crystals are mixed with water? <p>A:
Hey, that's not second. That's third. Anyway, it holds up pretty well. When I could leave the etching system set up permanently, I just covered the tank to reduce evaporation and all was fine. However, if you transfer the solution to a plastic jug, don't keep it tightly capped, because the solution will pressurize the container. Let it breathe a little bit. I ruined a good chunk of tiled floor at school when I tightly capped a gallon of the stuff and it ruptured.<p>Q:
Third, is what I've heard that it eats right through etch resist pen, true, so if I fix any parts of a board with a sharpie it doesn't matter?<p>A:
Fourth, I've not had that much trouble with it doing that. A Sharpie just doesn't work as well as other things. My best resists was Testor's #1103 flat red model paint back in the olden days when they had decent model paints and I was using ferric chloride. For some reason, the other Testor's colors wouldn't hold, but the #1103 did. Go figure. If you use the Sharpie, make sure that it's the original size pen as the fine-tip ones don't work as well. Make sure its new so that it lays on thicker. And don't try an off-brand unless you know it works.<p>Q:
I also have a couple of questions about the etching tank. I'm using a fish tank air pump with a 4" long bubble wand in the bottom center of the tank. Is that enough? <p>A:
Avoid the air stones for the bubbles. I prefer a piece of the regular plastic air line with 1/16" holes drilled along the submerged length. The more air, the better and faster the etching, but any air bubbler will cool down a heated solution at a rapid rate.<p>Q:
Also, do you think using a heater is worth the extra cost? <p>A:
Absolutely! A heated solution, whether ammonium persulfate or ferric chloride will etch in a fraction of the time. In either solution, if the solution is new, the bubbler is roiling the surface and the soup is hot, a board can etch in five minutes. Etching time always increases as the etchant gets used up, the temperature drops or the agitation lowers. I use two fish tank heaters to bring the solution up to temp and one to maintain.<p>Q:
Finally, does this destroy more than copper metal? I want to use clips to hold the pcb in the solution, and want to know if I can use metal clips, as long as they are not copper.<p>A:
Stick with as much plastic and glass as you can. I know that ferric chloride would cause the ferrous metals at the other end of the house to rust, it was so bad about that. You can get plastic tongs at a photo supply house. I've not even bothered to try working with stainless steel, so don't know the effects. If plastic works, why change?<p>You can make a board carrier by putting longitudinal slots in a strip of 1/4 plastic to keep the PCB from slipping to the side and adding a long rod to lower and raise the carrier and PCB.<p>Dean<p>[ April 01, 2005: Message edited by: Dean Huster ]</p>
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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Mike
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Re: Ammonium Persulphate

Post by Mike » Fri Apr 01, 2005 5:56 am

Thanks for the detailed reply. At the time I do not have a heater, but wanted to try my first board. It was cold, in my basement, and it only took around 25-30 minutes to etch. It was neat physically seeing the process also. I came back into the room right about when it was done and I saw the last of the copper dissolving right before my eyes.<p>It's kind-of weird how it works, though, because when you first put it in, the copper shows, but 10 minutes later I looked at it again, and I could have sworn it was finished. The board had turned completely white, like the color of the PCB. I took it out, but it wasn't done. again, 10 minutes later, I looked and the copper had shown up again and was almost all gone.<p>I'm not using an air stone, because I have heard exactly what you told me before. Instead I am using a 4" perferated bubble tube I got at PetSmart. Seems to work perfectly.<p>Do you think just a couple of holes in the top of the container will be enough for the solution to get enough air, or will I need more? I'm going to go take a picture so I can show what I mean.<p>Thanks again for the reply,
Mike

Mike
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Re: Ammonium Persulphate

Post by Mike » Fri Apr 01, 2005 6:07 am

Here are the pictures. For dial up connections, they are large (1024x768, 300k each). Actually, rather than drilling holes in the container (which by the way took me forever to find. I couldn't find one that was clear, only frosted. For once the Container Store actually had a purpose), can I just leave the top up like it is now for the tube to come out or could that be too much?<p>http://www.electronet.dyndns.org/etch1.jpg
http://www.electronet.dyndns.org/etch2.jpg<p>Thanks again,
Mike

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Re: Ammonium Persulphate

Post by bsparky » Fri Apr 01, 2005 7:46 pm

Were do you buy ammonium persulfate never heard of it before. Ferric chloride is nasty stuff. Had it ruin a whole tool box and every thing in it once.

Mike
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Re: Ammonium Persulphate

Post by Mike » Fri Apr 01, 2005 9:03 pm

Fry's Electronics. It's only at the store, you can't buy it on their website.<p>It's 14.99 for enough to fill that 5 liter container I have it in. The bottle is 2.2lbs of crystals that mix with 4 liters of water, making about 4 1/2 liters.<p>They also sell Sodium Persulphate, which is 18.99 for the same amount of crystals, and I was going to get but they were out of stock. It supposably is compatable with etch resist pens (which they say ammonium persulphate isn't), but, like Dean, on the first (and only so far) board I made, there were some spots I had to fill in with a Sharpie, and, just to be safe, I also put some Radio Shack dry transfer PCB traces I had, but they were not needed because the Sharpie worked just fine. I also took it out right when the board was done, so maybe had I left it in there much longer it would start to eat away at it. But Ferric Chloride did that too, often before the board was done.<p>It's really great stuff, though. As you can see from the pictures (if you looked at them), the solution is just like water with a light blue tint. It doesn't stain your hands nor clothes (I runed a pair or jeans with Ferric Chloride once). And you can see the board.<p>If you don't have a Fry's near your house (either way, I kinda don't like the store because they treat everybody like you are a crook by having people stand by the door who compare every item in your bag to the receipt. But you can just refuse like I do.) then try calling the 800 number on the www.outpost.com website or call the Fry's closest to you and see if they can ship it.

Dean Huster
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Re: Ammonium Persulphate

Post by Dean Huster » Sat Apr 02, 2005 1:33 pm

Mike & Sparky, here's a pointer to a topic that's now gotten buried on page two of the topic list:<p>http://206.131.241.58/ubb/ultimatebb.ph ... 002566&p=2<p>This is a list of suppliers and the things they carry that I created. Go down to Kelvin and you'll find another supplier of ammonium persulfate. Kelvin specializes in sales only to schools, but I've heard of folks getting stuff from them if they persist and claim that they'll take their order elsewhere. Either that, or make believe that you teach and see if they'll deliver to your home address (think of some reason or other here) rather than the school address.<p>Kelvin tends to be cheaper on a lot of things.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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JOHN GAGARIAN
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Re: Ammonium Persulphate

Post by JOHN GAGARIAN » Thu Apr 28, 2005 4:16 pm

Re: ammonium persulfate. I have been using the stuff for many years now.Price per pound is about one dollar when purchased in 50 pound bags.
Persulfate must be maintained in 2 or 3 heavy plastic bags inside each other and inside an AIR THIGHT CONTAINER.
I mix only the quantity I need for a run. It is always better to use fresh mix rather than store it up. After it is depleted, persulfate is a potent weed and plant killer, and maintains house drains clean.
I use the mix at 130 F degrees. and the best method i found is to use a pivoting tank made of acrillic. This produces a continuosly wawy motion that expedites copper removal. Generally I have 2 or 3 tanks of different sizes I always use the closest one to the size of the boards and use enough solution neccesary to cover the board I use a DC motor with an eccentric coupled to the tank producing a tilting motion). A variable power supply is a good way to control the speed of the motor I use hot water to mix the ammonium Once the solution is mixed I use a 150 W spotlamp on top of the tank> This provides bright illumination and keeps the solution at working temperature.Working temp is 130/150 degrees F.
Do NOT overheat

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philba
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Re: Ammonium Persulphate

Post by philba » Thu Apr 28, 2005 8:46 pm

I'm a big fan of AP. Go get an aquarium heater. It wont get you much above 100F but that's a pretty good temperature. I get about 15 minute etch times.<p>I have been using CuCl but I have to be a chemist to use it and I'm getting tired of it so I'm switching back to AP.<p>I built a vertical etching tank that, with the heater and air hose, holds exactly a quart of etchant. <p>Anyone know how to regenerate spent etchant?

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Re: Ammonium Persulphate

Post by peter-f » Fri Apr 29, 2005 5:54 am

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by JOHN GAGARIAN:
Re: ammonium persulfate. <p>... I use the mix at 130 F degrees. and the best method i found is to use a pivoting tank made of acrillic.
<hr></blockquote><p>Acylic?
Wouldn't Polypropylene be better for chemicals of almost any sort?
It's formulated for non-reactance, unlike acrylic (for example, you CAN"T glue it).
It's cheaper.
It can be found in molded containers of numerous sizes.<p>I'd advise anyone doing work with chemicals they're not familiar with... start with a PP container.<p>As for clips to hold the work... Plastic woodworking spring clamps - about $1 each.
Just periodically inspect the spring for reaction from vapors.<p>And (please) neutralize your chemicals before disposition! After all, they thought MBTE wasn't going to be a problem... now look!

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philba
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Re: Ammonium Persulphate

Post by philba » Fri Apr 29, 2005 8:26 am

Acryllic works fine with AP. Use a fusing cement and you'll be ok. I couldn't find a PP (or HDPE - works as well) container that was approx 8"x8"x2" (HxWxD) - as I wanted to only mix 1 quart at a time and wanted to do up to a 6x6 board vertically. So I made my own.

peter-f
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Re: Ammonium Persulphate

Post by peter-f » Fri Apr 29, 2005 3:00 pm

hey- I can appreciate your custom-size problem ... but PP containers are plentiful... as are 1 gallon buckets. <p>Just that: I'd recommend Anyone working with etchants be CERTAIN to make/find a container that's LEAKPROOF! Cement can hold for a long while... then fail. And plastic stress-cracking is a process that gives the pro's Plenty of exercise! It's not for a novice!

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Re: Ammonium Persulphate

Post by JOHN GAGARIAN » Fri Apr 29, 2005 5:59 pm

I agree that PP is safer than acrylic, but it is difficult to install pivots on this materiel.
I have been using acrylic made tanks for years on a daily basis. It holds pretty well use and abuse. The ideal etching temperature for persulfate is 140 F. I was unable to find any method to Rejuvenate persulfate. Howewer I was told that used persulfate is a excellent weedkiller and mixed with other elements can be used also as a fertilizer. The safety sheet doesn't indicate a recommended method of disposal except dilution in water.

Dean Huster
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Re: Ammonium Persulphate

Post by Dean Huster » Sat Apr 30, 2005 10:09 am

"Weedkiller" and "fertilizer" seem to be at odds with each other here! I'd want to know a lot more about ground water contamination before I started spreading that stuff all over the wild blackberry canes I'd like to kill.<p>Since it's an ionic solution, I'd think that there would be a way to plate out the copper in the spent solution, but I don't even know original etching reaction. I was at first guessing that you were possibly ending up with a copper sulfate solution (or something similiar) but couldn't figure out where the ammonia went. Any REAL chemists or CEs out there who can come up with the actual reactions here?<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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peter-f
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Re: Ammonium Persulphate

Post by peter-f » Sun May 01, 2005 6:22 pm

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by JOHN GAGARIAN:
I agree that PP is safer than acrylic, but it is difficult to install pivots on this materiel.
<hr></blockquote><p>Well... it can be drilled... or a frame with pivots can be constructed to support a PP container... for Heavens sake! Your an engineer! <p>
And Dean... fertilizers CAN be weed killers... (I don't think the opposite is true!)
Example: Over-fertilization (Use too much SuperPhosphate, for one) can kill any plant (keep that in mind when your neighbor decides Not to maintain a bush or weeded area!)
:p

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