Post by thread:[OT]:PCB chemistry

I saw a discussion that started last week about PCB fabrication. One of the messages said that the useful life of Ferric Chloride could be extended by performing electrolysis on the solution to recover etched copper. I have tried this and it works. I think that the cathode should be copper and that the anode should be non-cuprous to prevent a simple transfer of copper from anode to cathode. The outcome of all this is that it removes the issue of diposal of used Ferric Chloride at least for a while as it now lasts for ages. Hope this is useful to someone! Alan Embedded Systems Engineer Microtima Ltd Ouseburn Mews 3-7 Stepney Bank Newcastle upon Tyne NE1 2PW Tel: 0191 2304411 Fax: 0191 2304422 -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> Alan Gorham wrote : > > I saw a discussion that started last week about PCB fabrication. > One of the messages said that the useful life of Ferric Chloride > could be extended by performing electrolysis on the solution to > recover etched copper. > > I have tried this and it works. I think that the cathode should be > copper and that the anode should be non-cuprous to prevent a > simple transfer of copper from anode to cathode Do you have any figures for the V and A of the electroplating tank ? My book deals with clean solutions of copper salts, not those contaminated with iron. A table that shows electrode potentials has -0.43V for Fe and +0.33V for copper. In a solution of mixed salts isn't there going to be migration of metals out of solution on to both electrodes ? And I think I'm correct that CuCl is the insoluble sludge, which is going to be more difficult to electrolyse than an aqueous solution If so, I don't know the dissociation constant for CuCl (which will be very low if it's insoluble) but perhaps getting the Cu out of the liquid phase before it reacts with the Cl atoms may work better than working on the sludge One idea I had for this (if it works) is to copper-plate other metal items. Decorative parts could be lacquered -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

If anyone is thinking about trying the electrolysis trick on some of their tired Ferric Chloride, then please go ahead. I have not delved too deeply into the Chemistry of it but I have seen results. I etch my boards in a plastic tray about the same dimensions as A4 paper and a depth of approx 2cm of Ferric Chloride. This gives an idea of the volume of etchant I use. My electrodes are a 10cm copper rod and a 10 cm steel rod. The cathode is copper and the anode is steel. The electrodes are at 6 cm separation and I simply hook them up to a 0-30V, 2A bench power supply. At a current of 1A I can recover about 10g of copper in 20 minutes. The etchant certainly seems to be noticeably more effective after this recovery. With regard to dangerous gases emitted: I perform the electrolysis in a fume cabinet with the extractor running. Since I am quite pleased with the results I have not looked too deeply into any implications, so if anyone can say if there are good reasons to stop then I will!! Alan {Original Message removed}

If you're going to go to a replenishable etchant, you might as well go all the way to Cupric Chloride etchant, which has some other nice features as well (such as TRANSPARENCY!) See http://www.dnai.com/~rexa/Projects/CuCl_ech.html I'm not sure why Iron chloride is so popular. Perhaps because it IS/WAS an industrial chemical already, easilly available in large quantities for low prices? BillW -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

While I could assume this is the case, I'd rather ask and know for sure: You remove the rods from the tank when you are not performing electrolysis, right? Do you current-limit the supply, or does the solution limit the current acceptably for you? Do you clean the copper rod before each use (as it should tarnish quickly in air)? Have you copper plated anything just for fun? Have you ever thought about getting a heavier layer of copper on your PCBs by using an unetched pcb as your cathode? -Adam Alan Gorham wrote: {Quote hidden}> > If anyone is thinking about trying the electrolysis trick on some of their > tired Ferric Chloride, then please go ahead. > I have not delved too deeply into the Chemistry of it but I have seen > results. > > I etch my boards in a plastic tray about the same dimensions as A4 paper and > a depth of approx 2cm of Ferric Chloride. This gives an idea of the volume > of etchant I use. > > My electrodes are a 10cm copper rod and a 10 cm steel rod. > The cathode is copper and the anode is steel. The electrodes are at 6 cm > separation and I simply hook them up to a 0-30V, 2A bench power supply. > > At a current of 1A I can recover about 10g of copper in 20 minutes. > The etchant certainly seems to be noticeably more effective after this > recovery. > > With regard to dangerous gases emitted: I perform the electrolysis in a fume > cabinet with the extractor running. > > Since I am quite pleased with the results I have not looked too deeply into > any implications, so if anyone can say if there are good reasons to stop > then I will!! > > Alan > {Original Message removed}

A couple of answers for you - Current limiting is built in to the concentration of the solution and SEPARATION of the electrodes. Voltage should be monitored across the electrodes and limited to around 2V (no large bubbles forming on the electrodes). You need to supply about 5V 'push' to get 2V 'flow' through the electrolyte. Clean metal (rubbed with sand paper) is essential for electrical conduction into/out of the electrolyte. Without special additives the metal ions will *NOT* adhere properly to an electrode, you just get a buildup of metal powder over the surface. Electro plating requires special (and often poisonous) solutions held at selected pH and temperature to achieve proper plating. So, no, you can't expect to be able to plate things with a simple cell, especially not existing circuit boards. You *CAN* get some success with (dull) nickle plating if you want to protect steel, copper or brass, but it's usually cheaper to buy parts already plated. Bye. {Original Message removed}

> A couple of answers for you - Thanks, what you said ties in with what my creaky old e-p book says (voltage, adding acid). In e-p terms an etching solution is well out-of-spec so I'm not expecting any sort of professional results. More of an experiment - if it fails I haven't lost anything, not especially fussed either way -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Alan Gorham wrote: {Quote hidden}> > If anyone is thinking about trying the electrolysis trick on some of their > tired Ferric Chloride, then please go ahead. > I have not delved too deeply into the Chemistry of it but I have seen > results. > > I etch my boards in a plastic tray about the same dimensions as A4 paper and > a depth of approx 2cm of Ferric Chloride. This gives an idea of the volume > of etchant I use. > > My electrodes are a 10cm copper rod and a 10 cm steel rod. > The cathode is copper and the anode is steel. The electrodes are at 6 cm > separation and I simply hook them up to a 0-30V, 2A bench power supply. > > At a current of 1A I can recover about 10g of copper in 20 minutes. > The etchant certainly seems to be noticeably more effective after this > recovery. > > With regard to dangerous gases emitted: I perform the electrolysis in a fume > cabinet with the extractor running. > > Since I am quite pleased with the results I have not looked too deeply into > any implications, so if anyone can say if there are good reasons to stop > then I will!! Thanks Alan! Does the resistance change when the copper is completely removed from solution? Maybe you could build a automatic circuit (using a PIC??) that removes all the copper then switches itself off. -Roman -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Thanks Alan! Does the resistance change when the > copper is completely removed from solution? Maybe > you could build a automatic circuit (using a PIC??) > that removes all the copper then switches itself > off. > -Roman Yeah, but then the etchant would immediately start working away on the copper electrode! Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics