RT: Who wants a method for through-hole using domestically available chemicals? - Page 1
Forum section: electronics / projects

author: alimirjamali
author_rank: Regular Contributor
timestamp: August 10, 2014, 05:52:09 am
content: One of the most popular Chemistry Youtubers has asked if there is enough electrical engineers who would like to watch a method for through-hole plating using domestically available chemicals.Here is the link to his Tweet:https://twitter.com/NurdRage/statuses/498252165928865792Dr. Nurd (@NurdRage /https://www.youtube.com/user/NurdRage) better know as Dr. Nurd Butyllithium is the equivalent of Dave Jones in Chemistry Youtube Video world. Please let him know if you are interested.P.S.:There is already a nice video by Pathetic Computing for PCB Copper Through-Hole / Via plating. Yet, who does not want another video?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 10, 2014, 08:05:51 am
content: Not terrifically hard as far as I know, but the magic really is magic, sadly:When you put conductor (and applied voltage) in a copper solution (typically copper sulfate with a little sulfuric acid), copper deposits on the cathode, and material is removed from the anode. The anode either needs to be a robust enough material to handle ionic oxygen (such as lead dioxide, MMO (a similar thing but based on ruthenium oxide and others), or good old fashioned platinum), or you use copper so the solution replenishes itself (handy!).Now, when copper deposits on the cathode, the current flow follows Ohm's law: so, if your anode is a copper coin and the cathode is a wide plate, you'll get a prominent raised spot where they're nearest. Or if the cathode is oddly shaped, or has edges, same idea.So, guess what a PCB looks like. Flat, plus blind holes that you can't get the anode anywhere near.So the first problem is, the deposit builds up on the facing surface. The second problem is microscopic: it also builds up on minute imperfections, so scratches and bumps and crystal edges grow preferentially. By the time it's macroscopic, you have a nasty, weak, porous, dendritic deposit.What's the secret? Closely guarded, of course.The most common (and most readily available) remedy is thiourea, which is present in some copper-alloy polishing compounds like Tarn-X. A few drops in a gallon of electrolyte is usually sufficient to produce dense, matte deposits.The mechanism is this: the sulfur atom in thiourea is attracted to copper metal, and acts as an insulating barrier (a boundary layer very much analogous to the mechanism that grants supercapacitors their super-high capacitances). Second, it's polarized by the applied electric field, in such a way that it reduces deposition at the high points. So now, instead of crystals growing along sharp edges, they grow kind of lumpy like. The valleys get some attention; the bath is said to have some "throw".But to do actual PTH in PCBs, you need the big guns of 'throw' power. Not just a leveling agent. Supposedly, the best are also sulfur-containing molecules, in the xantho- range of organic chemistry. But even the academics seem to just buy off-the-shelf blends without inquiring too deeply as to their contents.Polarity reversal is also used to increase throw; evidently, material is removed from peaks preferentially, especially when the various additives are used. There may also be weird diffusion-limited (and therefore frequency dependent) effects to do with the reversal of polarity (attracting oppositely charged molecules to the surface, say). This, of course, isn't much of a challenge to the regulars on a forum like this.Obviously, you also need some way to make the holes conductive in the first place. You can use conductive ink for this -- it's goofy, but should work well enough at very low current density, until enough copper is down to carry it. Or you can use an electroless strike bath, such as a hypophosphite based copper or nickel bath (very toxic, and may only work on metals; something about auto-catalytic bla bla bla), or a copper mirror reaction (usually using hydrazine hydrate (also nasty stuff) or potentially, ascorbic acid (yay!!)).So, in summary:Copper plating: easy. Sulfuric acid (drain cleaner -- the kind that says sulfuric acid, obviously), copper sulfate (root killer, or make it yourself from scrap wire (burn / strip the insulation, add oxidizer) and recrystallization* for purity), a dash of Tarn-X.*Copper sulfate crystals are a goal in themselves. Very beautiful compound, if I do say so myself. If nothing else, when you're done, forget about the electrolyte for a while, let it dry out. Rinse and dry the crystals, then put them in a decorative vial or something.Being able to make holes conductive: not bad. Get something conductive and runny. Beware that, if it leaves much residue in the hole, it's probably weak. So, maybe a source of compressed air should be on the "things you need" list, too.Being able to plate holes: somewhere between hard and impossible. Get the proper chemicals if you can. (Don't forget to dispose of everything responsibly, too!) This isn't something you can find on the hardware store shelves, at least not as far as I know (but hey, read labels and try things, maybe you'll get lucky -- and please do tell, either here, orScienceMadness, among others I'm sure, would be interested as well!).Increasing throw by polarity reversal: medium. Build an H-bridge to switch the cell polarity, and either leave the current as-is (the cell itself needs current proportional to working area, and no more than 5V), or try modulating that as well.Tim(Yes, besides being an electronics know-it-all, I'm sufficiently dangerous in the chemistry lab as well!)

author: SeanB
author_rank: Super Contributor
timestamp: August 10, 2014, 08:27:47 am
content: Polarity reversal is simple by using a half wave rectifier on the transformer, with a variable resistor ( big high power wire wound unit of appropriate resistance and power rating) so that you get a controlled reverse current on each cycle. That does give a much smoother plating with copper, and also works on zinc plating as well to give a smooth coating. Does not work well with chrome plate as there you need a smooth DC but is usable with the copper and nickel undercoats used to provide the keying layers and smooth the surface to a mirror finish prior to plating.Transformer has to be overrated quite a bit to handle the nett DC current through the core though.

author: IanB
author_rank: Super Contributor
timestamp: August 10, 2014, 08:47:18 am
content: What is the value of plated through holes for home use? If we assume a home etched board will only be double-sided then why not just solder wires through where the vias are needed? Sometimes the wires will be component leads that can just be soldered on both sides.

author: Kostas
author_rank: Regular Contributor
timestamp: August 10, 2014, 08:59:45 am
content: Quote from: IanB on August 10, 2014, 08:47:18 amPerhaps for a via under an IC? A bump under an ic can be problematic I suppose.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 10, 2014, 09:11:04 am
content: The problem is that even if you have a good plating process, you need to cnc drill the holes, as plating happens before etching.This is something that just isn't worth the bother.It won't be cheaper than the cheap PCB services, and although maybe quicker for a 1-off it will still take a lot of your time, which could probably be better spent on other things while waiting for a proper PCB house to do it properly.For a 1-off, rivets or through-links will be quicker than plating. For boards where density needs to be higher than you can do that way, chances are you'll struggle to etch & drill reliably to the required resolution, and you won't have a resist, which will make assembly harder.

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 09:21:57 am
content: At $5 / sqin for 3 professional double sided plated through solder mask silkscreened PCBs these days, where is the value in being able to do this?

author: Artlav
author_rank: Frequent Contributor
timestamp: August 10, 2014, 09:46:20 am
content: Quote from: EEVblog on August 10, 2014, 09:21:57 amNot having to wait for 8 days lead time plus 1-4 weeks of postage times to get your PCBs from Pcbcart, when all you want is to clean up a breadboard?

author: sleemanj
author_rank: Super Contributor
timestamp: August 10, 2014, 10:07:47 am
content: Quote from: EEVblog on August 10, 2014, 09:21:57 amWhy do people climb Everest? Freezing your nuts off, one misstep or unexpected storm from a painful prolonged death, days, weeks, months of planning, and execution, massive amounts of money, a huge support team, and in general a whole load of unpleasantness all for a scant few minutes when you finally get to stand on the summit and look out at the surroundings before you have to join the line heading back down again. When for a few hundred dollars you can get on an airliner, and in comfort and almost total safety be looking out at the world in a few minutes.They do it for the challenge, to prove they can, because it's regarded as a pinnacle of achievement in their particular past-time.

author: void_error
author_rank: Frequent Contributor
timestamp: August 10, 2014, 10:12:16 am
content: Quote from: EEVblog on August 10, 2014, 09:21:57 amI think it's not worth the effort, since you can get higher quality professional PCBs at such a low price.I'd still like to make double-sided PCBs with plated through-holes at home but I can't get most of the chemicals over here and I'm not sure about the success rate of the whole process. I'll still keep an eye on this, maybe someone comes up with a better solution.For single-sided boards, however, I'll still be making them at home and although without silkscreen and soldermask, but they're still going to be dirt cheap (something like $3 or less for a 50x100mm board). I can currently get 0.4mm traces reliably and I did manage to get 0.2mm line thickness text etched. Sticking to SMD will save me a lot of time because I don't have to drill so many holes, plus SMD parts are generally cheaper and occupy less space.Quote from: IanB on August 10, 2014, 08:47:18 amVia stitching maybe?

author: poorchava
author_rank: Super Contributor
timestamp: August 10, 2014, 10:45:40 am
content: I don't agree that homemade PCBs are not worth it. They are because they are simply cheaper. What is cheap enough not to bother with homemade versions for people living in US, OZ or western EU, doesn't necessarily have to be so for others. Remember, that most regular people living in centra/eastern EU, africa, india and so on quite often operate on an annual budget of ~$9-15k, with most of the stuff you need for living costing about the same as everywhere else.I mean if that's for my hobby and I don't care about the extra quality and it's just something I do in my free time, then I have no objections to tinker with PCBs at home.Another merit behind homemade PCBs is large stuff like power electronics. $5/sq.in may not be much, but if 1 sq.in is how mucha single capacitor on your board takes - it stops being economical pretty fast.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 10, 2014, 11:29:01 am
content: Quote from: poorchava on August 10, 2014, 10:45:40 amHomemade PCBs are definitely worth it, as the basic process is simple, quick and cheap, but as soon as you go beyond a simple non-plated 2-sided board with rivets or pins to link sides, the effort of additional processes rapidly becomes less worthwhile.

author: amyk
author_rank: Super Contributor
timestamp: August 10, 2014, 11:48:34 am
content: Look at OP's country... they are in a very different position from most of the West.This reminds me of the time when doing SMD at home was considered impossible, and hobbyists wouldn't even touch BGAs. Now there's still some reluctance to use BGAs, but SMD isn't considered so difficult anymore as processes with toaster ovens and hot air guns get improved upon. Maybe in another two decades hobbyists will be making multilayer boards with 0.5mm BGAs at home... while the industry has moved onto um-scale packages.

author: poorchava
author_rank: Super Contributor
timestamp: August 10, 2014, 12:22:27 pm
content: I only do 1-sided boards at home, which is typically perfectly enough for general prototyping. Since it's prototyping, a jumper link or two doesn't hurt. If one has CNC machine at hand this is another story - you'll always get perfect layer alignment, so double-sided boards ar as easy as single sided. Still - drilling holes like 0.4mm for vias will be pain in the ass, since those are typically rated for 80-130k rpm range, and spindles that can achieve such RPM are mostly out of hobbyists range. IMO when you cannot fabricate vias like 0.4/0.8 don't bother at all - larger sizes are impractical for dense circuits.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 10, 2014, 01:01:38 pm
content: Quote from: poorchava on August 10, 2014, 12:22:27 pmThat's just about feed rate - lower RPMs are fine if you just feed more slowly. I've hand-drilled (with drill stand) 0.3mm in the past so CNCing shouldn't be an issue.

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 01:29:05 pm
content: Quote from: Artlav on August 10, 2014, 09:46:20 amGetting your boardtodayis currently the only real advantage left for DIY boards.But even then, what use is plated holes really in a one-offtodayproto board? Soldering the feed through jumpers is going to be quicker than setting up some system to plate them.BTW, I've had my boards from PCBcart delivered to my doorstep in 8 days for normal boards. Quicker with other providers like pcbzone.net. Cost a bit more, but generally if you doing doubled sided layout that worth plating, then you can probably afford to pay a bit once in a while.I've made double sided DIY boards both professionally and personally in a few hours, and that has been handy, but it's pretty rare that I've needed that, and in all cases I've had no trouble with just soldering the feed-throughs. Having plated holes really wouldn't have given me any extra advantage.

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 01:34:42 pm
content: Quote from: sleemanj on August 10, 2014, 10:07:47 amOf course, and I support that, I've done it myself.I'm of course talking about the real practical value. This value window is quite narrow for any decently complex double sided board, and it's more narrow again when you start talking being able to plate them.I can understand the cost issue for larger boards in some countries though.

author: alimirjamali
author_rank: Regular Contributor
timestamp: August 10, 2014, 01:51:43 pm
content: Quote from: T3sl4co1l on August 10, 2014, 08:05:51 amThank you very much for detailed explanation Tim.Quote from: IanB on August 10, 2014, 08:47:18 amIt is hard to impossible to solder some parts such as IDC pin headers or TO-3 transistors on the top side(image courtesy of WIKIPEDIA under GPL licence).

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 01:57:52 pm
content: Quote from: alimirjamali on August 10, 2014, 01:51:43 pmIt's a one-off prototype board. There are plenty of ways around that problem. Been there, done that countless times.

author: Artlav
author_rank: Frequent Contributor
timestamp: August 10, 2014, 02:08:11 pm
content: Quote from: amyk on August 10, 2014, 11:48:34 amHm. Even without ovens SMD is quite easy to solder.So far i pushed my limits of home soldering and etching at TQFP100, with an FPGA board.I considered TQFP144, but i think if i push my boundaries again i might find them this time.BGAs? Nope.Quote from: poorchava on August 10, 2014, 12:22:27 pmHm, how about a DC motor with a drill head mounted in a simple drill press rig?It's much easier to align a piece of PCB than it is to a lign a hand-held drill.Quote from: EEVblog on August 10, 2014, 01:29:05 pmThere had to be a limit where you stop trying to make the board yourself and start looking for other options.So far, the most complex board i could make at home was this -It was an ordeal, getting all these fine traces to stick, getting the FPGA aligned, etc.Now, i want to make something like that -And that's when i started looking for alternatives, like PCBCart, since this is somewhat out of my depth already, even if i could plate the holes.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 10, 2014, 02:12:21 pm
content: Quote from: alimirjamali on August 10, 2014, 01:51:43 pmSo you design your board to avoid the need to.Or you put a thin bit of wire through and top-solder before mounting the partsAnd does anyone actually still use TO3's...?

author: Artlav
author_rank: Frequent Contributor
timestamp: August 10, 2014, 02:17:00 pm
content: Quote from: mikeselectricstuff on August 10, 2014, 02:12:21 pmAll sorts of power supplies?https://www.eevblog.com/forum/reviews/mastech-hy5002-power-supply-died-worth-fixing/

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 02:31:31 pm
content: Quote from: Artlav on August 10, 2014, 02:08:11 pmYes, maybe about 10 years ago when the PCB prototype game began to change toward the cheap shared panel model we take for granted these days.Not everyone remembers that before that (at least in this country), you had to buy a whole panel in order to get your one board made, and it cost a lot, like $300-$500 just for the film or something.So that was almost unheard of to get done for your own personal projects. It was actually one of the major perks of working for a company in that you could often throw one of your personal boards onto the spare panel space.As for work boards, depending upon the company I worked out, you might be under a lot of pressure to get a proto done, but no budget to pay the huge $$$$ to get a panel spun in 1-2 days, so you just made it yourself with positive photoresist coated boards from Farnell or a local supplier. Heck, I didn't even bother with a UV box, just stood it outside in the sun for 15 minutes each side.Or the boards were simply so complex it was impractical to make yourself, or that particular company (or project in the same company) didn't care about paying a few $K for a proto board in 24 hours.Or there was simply so much paperwork involved in raising the purchase order to get a board made, you'd just make it yourself because it was less hassle. There was no such thing as this online ordering stuff not that long ago in the scheme of things...So, yes, for various reason I haven't made my own boards for maybe a decade now. And there is getting less and less reason why I'd bother every year.

author: SeanB
author_rank: Super Contributor
timestamp: August 10, 2014, 02:34:03 pm
content: TO3P is a lot easier to both mount and interface. You just make a small board that takes the leads onto it at one end and the other end has a connector for off board wiring, along with possibly being able to have multiple devices along with the required base current resistors and even have emitter current sharing resistors along with sense leads if you are measuring current there. You can even save wiring for driver transistors with ease.DIY works for simple boards and large spacings, also for things where you need it within a day and do not want to pay. Works here in the back end of nowhere as well where delivery via anything fast is going to be ultra expensive.

author: alimirjamali
author_rank: Regular Contributor
timestamp: August 10, 2014, 02:59:21 pm
content: I am honored to see Dave & Mike here!Quote from: mikeselectricstuff on August 10, 2014, 09:11:04 amQuote from: EEVblog on August 10, 2014, 09:21:57 amIn Tehran we pay less than half. Delivery as short as one day. The price for 5000+ cm2 will be significantly reduced.I fully agree that with excellent pricing of cheap PCB services such as OSHPark and their equivalents worldwide, there remains few reasons to do plating or even etching at home. Even the worst Electronic Junkie could wait few days of the holidays to get his/her new PCB to sniff at.The reason I recommend encouraging the guy (NurdRage) is that he is a PhD in Chemisty who might be able to show us other cool methods such as making conductive fabrics & flexible objects, plating non-flat objects and many other useful methods. He requires a small amount of encouragement. Otherwise, I am sorry if I flooded the forum.

author: SeanB
author_rank: Super Contributor
timestamp: August 10, 2014, 03:39:17 pm
content: No apology needed, the forum is here to discuss ideas in an open atmosphere, where all are free to add an opinion. Yours is also valued, as this is something that often has been thought of before, but as times change you need to revisit the old ideas and refresh them. There is always room for good discussion here.

author: akis
author_rank: Frequent Contributor
timestamp: August 10, 2014, 04:20:03 pm
content: Quote from: IanB on August 10, 2014, 08:47:18 amIf the holes are plated through it allows you to run traces on the top layer without need to solder on the top. Soldering on the top is problematic for components that do not leave much space underneath and crowded spaces. In these cases you have to avoid any traces connecting at the top which makes routing much more difficult.

author: IanB
author_rank: Super Contributor
timestamp: August 10, 2014, 04:46:53 pm
content: Quote from: alimirjamali on August 10, 2014, 02:59:21 pmI do not warm to NurdRage. I do not like the whole anonymous "chemistry as a dark art" thing. I far prefer the chemistry videos from the University of Nottingham (Periodic Videos) where they are quite unapologetic about doing crazy stuff and being in the open about what they do.

author: alimirjamali
author_rank: Regular Contributor
timestamp: August 10, 2014, 05:08:56 pm
content: Quote from: IanB on August 10, 2014, 04:46:53 pmI also love Prof. Martyn Poliakoff and the staff. BTW, being anonymous does not mean that NurdRage is a closed person. I have never seen illegal stuff from NurdRage. Being anonymous is a personal choice for many who prefer privacy. Have you ever seen Afroman (https://www.youtube.com/Afrotechmods) in any of his videos? Does anyone know his real name?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 10, 2014, 10:17:55 pm
content: For those on the debate of make vs. buy:Keep in mind, half of us are professional engineers who have more important (read: hourly paid) work to do, and half of us are hobbyists who do this for fun and have a labor value of $0.00 (if even less -- i.e., doing it at overall expense, for fun). And half of each set overlaps, so many of both groups have experience with both making and buying.Regarding prototypes, personally, I moved completely to deadbug (which is also handy as I don't have the facility for chemicals in my current location). It's very labor intensive, but when you include layout and printing and so on, it's at least as fast, plus you can test it as you go.Tim

author: EEVblog
author_rank: Unknown
timestamp: August 10, 2014, 11:12:53 pm
content: Quote from: alimirjamali on August 10, 2014, 02:59:21 pmI agree, he should do it, some people will find use for it, it's interesting in it's own right, and it could lead to other stuff.I'm just trying to offer a practical perspective in what value such techniques will actually be for most people.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 11, 2014, 01:24:00 am
content: Quote from: EEVblog on August 10, 2014, 09:21:57 amCareful; some people react violently at the suggestion they should outsource their hobby PCBs...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 11, 2014, 02:17:01 am
content: Quote from: T3sl4co1l on August 10, 2014, 10:17:55 pmDo you mean deadbug on a piece of copper clad? I use Surfboards on copper clad. Stuff's cheap.http://www.digikey.ca/product-detail/en/9161/9161CA-ND/151979Then I can re-use the bits of circuitry that I want on other circuits.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 11, 2014, 07:28:08 am
content: Yes, that too. THT and limited SMT (<= 4 pins) can be done by tacking down small cut squares of PCB stock as pads; more either requires a fanout board like that, or a utility blade to carve traces by hand. The latter also helps with power handling (you can make nice wide traces/pours), but then you need supporting ground plane, so you can drill a few holes around and stitch the top surrounding copper to the solid bottom for requisite grounding.Example:http://seventransistorlabs.com/Images/GD9.jpgTim

author: SeanB
author_rank: Super Contributor
timestamp: August 11, 2014, 05:31:13 pm
content: If the others in the house moan about the chemicals you can do the old fashioned thing and plate things with copper, like leaves or the old standby of the first baby booties.

author: free_electron
author_rank: Super Contributor
timestamp: August 11, 2014, 05:52:36 pm
content: plating is one thing.there re bigger issues :- you need to drill the holes FIRST. this requires some sort of cnc setup as you have no visual queue where they need to be.once plated you need a way to apply etch resist ... either photomask (liquid or dry film ) and make darn sure the plated holes are well covered in mask or they will eat open during etching, or you need the sacrificial tin plating process... and then you need negative images...and then you can do doublesided.... multilayer is no-go...you can do doublesided without metallisation. just solder at top and bottom and use component pins as via's.once you go to surface mount the structures and drill holes become so small that home-etching is not feasible.in short : not worth the trouble.china : 8$ for 10 boards ... plated, soldermasked and silkscreened