True plated vias at home - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: February 18, 2019, 05:13:25 pm
content: So what do you need for this more advanced process?1) what method can be used to drill the hole? I understand they use a carbide drill with a excess of 100k rpm in an air spindle. Can you drill a hole conventionally and use something like a microreamer to clean it up? An option here would be to make a custom drill press that uses an air spindle so the hole can be drilled correctly.2) how is the chemical process done? I assume you need something like a rocker table or a combined ultrasonic process?I know its hard and not economical. I wanted something better then the copperset via kit.If you have alot of time, can you electrodeposit a lip around the hole then use a micrometer connected to an annode thats being gradually removed to grow a verticle layer downards then do lapping to clean it up?In the ink method is there significant adhesion between the electroplate and the via wall?Then when you grow a almost full shorted cylinder, use a micropipet to inject liquidy epoxy around the via growth pcb hole interface as its cooled to make a verticle wall bond then finish the plating? There is significant differential contraction so a copper tube grown along side a fiberglass wall should shrink and allow thin glue to enter under vacuum.I dont like the ink idea for some reason

author: Mark
author_rank: Frequent Contributor
timestamp: February 18, 2019, 05:48:18 pm
content: I can't help with the chemical process, but for drilling i would recommend standardising on one size of via hole and using a drill bit of that size in a CNC machine. Import the NC drill file into FlatCam and export gcode to the CNC.For all other holes (i.e. anything larger than your standard via, like power connector leads) use a 0.8mm end-mill. After importing the NC drill file into FlatCam, select all the remaining holes and use the end-mill for those. FlatCam does the rest and generates gcode for the CNC.I've found that the cheap ebay 0.8mm end mills are strong enough for most FR4 laminates I've tried them with. They are also cheap enough to keep a good stock of. I also tried 0.5mm end mills but with many breakages.

author: coppercone2
author_rank: Super Contributor
timestamp: February 18, 2019, 05:57:12 pm
content: I have no problem getting good holes with a 8k rpm carbide drill in a proxxon collet drill press but i thought vias needed extreme surface finish or something. I thought the ultra high speed carbide might polish it. You also might need some kind of acid bath to clean the hole.I wonder if the use of a reamer would rectify this? I never understood why a high speed drillcutting process would be used for surface texture reasons rather then a reamer scraping operation. It should far exceed the quality and remove any burnished glue. But i supose the material might fracture and melted polymer bonding material is pushed into the holes.. does this still happen with reaming?Regardless it should decrease the need for agressive acid removal?Can piranah fluid be used to burn the polymers? In more dillute form? Can the board bd hard frozen first to decrease thermal activity? I.e. liquid nitrogen submerged drilling?With a precision fluid system you can proboblt cycle corrosive liquid through a single drill hole to clean it up while decreasing harmful materials use. A sacrificial low reactivity gasket can be used on tiny diameter stainless or glass tubing.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 18, 2019, 06:22:20 pm
content: Quote from: coppercone2 on February 18, 2019, 05:57:12 pmFor reference, most commercial PCB drilling machines are >100k RPM and closer to 150K RPM is typical.

author: coppercone2
author_rank: Super Contributor
timestamp: February 18, 2019, 07:51:07 pm
content: yes I heard that is the requirement for VIA plating but I am not sure if its just because you need alot of them and a reamer is a pain in the ass or if there is a better reason.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 18, 2019, 08:39:35 pm
content: Quote from: coppercone2 on February 18, 2019, 07:51:07 pmIt's a good question - I have no idea.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 01:28:12 am
content: any idea what chemical they use to clear up the vias from the polymers when they are drilled (I guess it is gummy compared to the fiberglass)?What I imagine is maybe if the speed is low, you get fractures under your cut, so as the drill is 'shaving' the material off the top, its ripping chunks off and then deforming the softer material into the fracture hole if the fracture forms in a way that is partially not in the drill path. Then you get a hole with patches of softer stuff on the sides. I figure a reamer should scrape it off, unless the reamer also fractures the material.Not sure if speed can circumvent this some how, I have trouble imagining mechanical things at 100 k + rpm. Maybe the piece that normally gets dislodged by a slower drill just gets hammered by the momentum of the fast drill, so it forms a clean cleave?Do you know what the most economical spindle that spins 100kRPM+ for a small home made drill press would be? I don't want a CNC machine. I don't mind setting up by hand, it would just a air powered drill press I guess?? (maybe you need to wear leather, face shield and gloves when you use it in case the bit blows up?). It would not be hard to make, you can probobly trick out a heavy duty arbor press or something with a air spindle head. The entire assembly could move up and down since at most your drilling like a 1mm hole. Like a magnetic drill rather then a quill feed. You would just need to tighten down the rack gear tolerances and maybe shape some posts or something to make it flatter but it should be doable with scraping. Just add a spring to a arbor press to pull the whole thing upwards or maybe even a pully/counterweight to mimic the quill spring. A big ass arbor press should be plenty stiff enough? Flexible air hoses should have no problem moving with the arbor press.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 19, 2019, 12:11:48 pm
content: The holes are rough but it doesn't matter as long as the conductive ink activates things properly. Indeed, a rough surface has "bite", making the plating more secure.The missing link is a conductive ink to electroplate the surface, or an activator to electroless plate the surface. I believe the latter is used industrially, but the former may be easier to demonstrate at home.The other key is a long-throw plating bath, with a combination of levelers to improve evenness of deposition, circulation of electrolyte to ensure adequate ionic concentration, and as far as I know, usually a pulsed current waveform (including reversal) to help knock down peaks as they form.Tim

author: MagicSmoker
author_rank: Super Contributor
timestamp: February 19, 2019, 12:41:37 pm
content: Quote from: coppercone2 on February 18, 2019, 05:13:25 pmA few days ago I was doing a semi-rush job on a replacement of a 12kV / 60A high speed rectifier using (20) 600V TO-247 diodes and I needed to drill 240 holes for the static and dynamic balancing networks. I did not relish the prospect of doing this by hand but didn't have enough time send the board out so on a lark - and without much hope of success - I tried chucking a #56 carbide drill into my benchtop drill press and set the pulleys to 3100 RPM. I firmly gripped the board then gently rotated the quill handle to drill the first hole and to my surprise the bit went through just fine and didn't break. I do have that shitty Dremel drill press contraption but it breaks bits if you look at 'em funny while drilling, so I expected similar issues with my bigger drill press, but that didn't prove to be the case.I can't help with plating-through the holes - generally, if I need those I send the board out (in fact, I send the board out 99% of the time), but I can at least recommend the 2 parts 3% H2O2 to 1 part 31.45% HCl (aka pool acid) etchant recipe. It etches extremely quickly at room temperature, doesn't give off too many noxious fumes and remains transparent the entire time. Oh, and it is cheap.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 01:19:13 pm
content: Quote from: T3sl4co1l on February 19, 2019, 12:11:48 pmcan you grow them down for a rim if you insert a thin electrode into the hole opposite to a formed rim and then slowly remove it as the cylinder grows if you want to do one at a time?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 19, 2019, 01:24:34 pm
content: Quote from: MagicSmoker on February 19, 2019, 12:41:37 pmYeah, a drill press is all you really need, to avoid breaking drills terribly often. Speed is just, well, speed. 100kRPM is great for rapid fire production, but if you can take it slower, anything less is fine.Amazingly, I'm in the habit of freehanding with carbide drills. But, this is only with relatively large sizes (#57 I think?), great care, and for maybe dozens of holes (vias in hand-carved copper clad -- one-off prototypes). I fully expect to break a drill every time I attempt this; any that survive multiple holes, well that's just a bonus.(I also have a carbide-tipped jobber drill for making larger holes, for screws and such. Pricey, but saves the wear that a HSS drill would get, which would be pretty significant by now.)Tim

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 01:26:44 pm
content: it says you need to clean the holes out with some kind of acid bath to remove organic polymers from the PCB that the ink has a bad time adhearing to. Are you sure it does not polish it or make a chemically cleaner hole some how? a little reamer would be best but I keep thinking the PCB is some weird material that behaves differently.I am now thinking, if you get some piranah fluid into a drilled hole, let it turn it burn the plastic, then ream out a few thousandths to get a nicer surface finish, it should make a REALLY dry surface for ink to adhere to.But the bond between conductive ink, PCB and copper must not be very good? do you want a good bond here? is it worth investigating a superior bond or does it actually get worse mechanical strain and you want some gummy stuff in there?there is no way conductive ink would be as strong as good slightly thinned epoxy poured in after growing vs grown on ink?

author: 2N3055
author_rank: Super Contributor
timestamp: February 19, 2019, 01:35:19 pm
content: Get your self a "Printed Circuits Handbook" by Clyde F. Coombs, Jr, read it and then order multi-layer boards with plated trough holes from professionals like the rest of us.It is chemical process, that needs many chemicals (some dangerous and some not), and while simple in principle, it is hard to do right and with repeatable results.It's not worth it.In general, holes are drilled with super high speed drills that leave clean hole. Then it is cleaned with acids , and then holes are activated with chemicals. For many years palladium based process was the best, lately there are others. This activation enables electroless deposition of thin copper layer in holes walls and then whole board is electroplated to full copper thickness including holes.For prototypes, you can use rivets, pins or wire links from top to bottom, and soldering of trough hole components on both sides...I haven't done any of it for a very long time, except some quick simple protoboards where it was quicker to to this than wire links manually in perfboard.It is fascinating topic but best left to professionals nowadays..

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 01:42:38 pm
content: im interested in it because its interesting and i wanna do it, I have the copperset system which makes a pretty nice via (you deform a lead filled copper slug int the hole). It actually comes with a little spiral hand reamer (or maybe its just a drill bit).Can you explain the mechanics of how 100krpm leave a cleaner hole in this material then low speed drilling? I don't understand this. Everything is left better to professionals lolHow do you quantify the surface finish? Assuming you used a jewelers saw to cut apart the PCB after you drill it to look at the hole under a proper microscope.

author: 2N3055
author_rank: Super Contributor
timestamp: February 19, 2019, 01:51:33 pm
content: As I said, get the book. It has 20-30 pages chapter just on drilling...It's pure gold and answers ALL your questions.

author: TopLoser
author_rank: Unknown
timestamp: February 19, 2019, 02:08:00 pm
content: Quote from: 2N3055 on February 19, 2019, 01:51:33 pmRemarkably there's a PDF version for download...https://www.dropbox.com/s/dyxkpus0whnbe2r/Printed_Circuits_Handbook_6Th_Ed_Malestrom.pdf?dl=0

author: Ian.M
author_rank: Super Contributor
timestamp: February 19, 2019, 02:12:13 pm
content: *IF* you are determined to DIY through plated holes, Caswell do an electroless copper kit that will plate on epoxy and other plastics. That will give you working plating chemistry, then you'll just have the problems of cleaning the holes, only activating the hole walls and afterwards, long throw electroplating to build up enough copper thickness.https://www.caswellplating.com/electroplating-anodizing/electroless-plating-kits/electroless-copper-plating-kits/electroless-copper-kit-1-pint.html

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 03:51:09 pm
content: Thanks for the book its what i was looking for, free infoWhat would happen if you tried to grow a cylinder downwards from a overplated rim? The electrode would be attached to J shaped rod attached to a motorized micrometer above the bath that would slowly draw the electrode away from the deposition. Like a arc welding type process in terms of distancing the electrode. If you had strong fluid flow through the hole could it prevent side deposition and look more like a cylinder without thickening so much?Can you plasma spray the holes? Perhaps it would be easier if you can clean em up after. Say flame plasma spray on a ceramic pcb? Say just drill the holes, rough it up with some acid, plasma spray the whole thing with copper then surface grind and drill and ream the probobly kinda clogged holes then fill holes with wax, mask, etch. It would actually make sense more then dealing with fr4 because if you go through all this effort you might as well go for the gold(nitride)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 19, 2019, 04:12:27 pm
content: What do you mean? Plating directionally so that the hole can be filled lengthwise? How would that work, what would cause it to expand radially into the wall and not simply crust over with lumpy crystals?Plasma/flame spray would probably work, CVD too (but not so much PVD as that's more line-of-sight), assuming you can get particles into the hole. So, probably not for small holes. It's likely to do a worse job than activation + electroless does. CVD would be fine I would think, but has no reason to exist* when electroplating is adequate.*There probably are CVD copper processes known, I just don't know of them. Ah, quick search turns up a few, including molecular layer processes. Nice. Well, in any case, electroplating is more than adequate on the PCB scale -- stereolithography processes need atomic precision these days, but PCBs certainly do not.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 05:09:22 pm
content: Ok i got this idea. If you dont mind doing vias one at a time.I noticed if a fuse blows with a heavy surge nearby you get nice looking copper plating. What if you make a *gun* mechanism which is a pipe with a reduction connected to a hoke (or whichever connector has the face seal gasket. I think they might be hoke hydraulic ones). I had sometbing like a 2 square inch pcb plated with shiney copper that needed sand paper to remove with a single blown fuse. Maybe bigger.Hell you might get sufficent plating thickness. That stuff was solid. Way easier then vacuum kilns or whatever you use for real controlled cvd. Just ream the hole afterwards.Then you flow argon through the pipe, press the gasket around your via hole and use a decent cap to vaporize a small copper wire and have argon flow carry it so it deposits into the via. You can even cool the pcb down on a peltier coldplate before hand so it better works as a condenser and actually heat the gun assembly so it clogs less. It might give a better or cheaper basecoat then plating baths. You can put like 20 charges into a dip40 socket and vaporize them one after the other so you can work fast.I wonder if you can use flow at atmospheric pressure this way.Or make a special jig that you put the pcb between and thread fine copper wire through each of the vias and blow them in series.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 05:14:22 pm
content: And for growning it down the bore, who cares if its crusty so long the base layer is good? Just use a few series reamers. You can clean em up fast.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 05:16:33 pm
content: And you can draw a blocking rod downwards the bore from the top as the electrode moves down to discourage weird crystal growth? Like push/pullOr even have the top blocking thing be a ceramic cutting tool that spins and continously knocks off unruley sideways growth.The custom advanced organic chemistry scares me. Sounds expensive and perishable and like it can fuck up easily.i dont like the idea of conducyive ink or laced plating baths. Sounds like a big company tempremental headache.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 05:23:43 pm
content: Your gonna end up having to buy a spectrometer to check plating chemicals. I dont mind machine tool operation, there must be a more controllable method.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 05:27:05 pm
content: If you can blow wire you can make platinum or silver or whatever material vias. I wonder if you can make invar vias that are stable if you turn invar into gas!

author: jmelson
author_rank: Super Contributor
timestamp: February 19, 2019, 07:56:55 pm
content: Quote from: coppercone2 on February 19, 2019, 01:28:12 amThat's called epoxy smear, and the standard technique is plasma desmearing. It can be done in a modified microwave oven. You build a Plexiglas air tight box inside the microwave, and drill a small hole in the microwave for a vacuum hose. You put a beaker with a paper towel wet with household bleach inside. You make up 2 grids of screen material with some sewing pins sticking out of their faces, these generate plasma at the points. The bleach generates oxygen and chlorine ions which break down the epoxy smear in the holes, and etches back the hole walls slightly to expose the ends of the glass fibers. After a few minutes of plasma, you blow the dust out of the holes with compressed air.I don't know of any sane chemical open-air room temperature process. Decades ago, there was mechanical hone, a chamber with a vacuum on one side of the board, you sprayed abrasive slurry on the other side of the board, and the vacuum sucked it through. It looked like a VERY messy process.JonJon

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 08:44:50 pm
content: will swabbing it with 30% hydrogen peroxide and 98% H2SO4 work? it burns anything. Very cheap too.https://en.wikipedia.org/wiki/Piranha_solutionYou can mix it in tiny amounts in a test tube using drops actually. Would work well for VIA's if you make 20 drops up (like 1mL)]Then put it on a formed glass fiber swab that is inserted into the holes.

author: IconicPCB
author_rank: Super Contributor
timestamp: February 19, 2019, 08:47:27 pm
content: spindle speed is immaterial; it is the combination of spindle speed versus linear feed.In fact taking it slowe (lower spindle speed ) produces less smear for two reasonsspindle bearing runout is lower and generated heat is lower.Chemical desmear process can take place in highly alakaline ( PH=11) solution at 60C for a few minutes.A good source of high speed spindles is Alfred Jaeger a German company.A 60K RPM spindle will set you back a few thousand Euro.You will need a small three phase inverter to drive the spindle ( small - 400watt).In terms of activation chemistry Think and Tinker from USA have a product, a conductive ink.I recommend it.I have used palladium suspension from Atotoech. Very finicky suitable only for continuous production excellent results. Can not recommend it for one off production.I am using a Russian idea based on copper hypophosphite. Suitable for stop start production. HIGHLY RECOMMEND IT.Requires an electropolishing cell consisting of a high current source( say 10 amps per square decimeter of copper).Excellent results with minimal chemistry , better adhesion to hole walls than anything I have used to date.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 08:48:35 pm
content: im gonna try making a plating gun that blows up copper wire in a tube with a argon feed. I am curious.Is the surface finish by a 8k spindle ok for a 0.8mm to 0.3mm via ?Base solution = warm sodium hydroxide? What do you mask the PCB with? Can you just lay the drilled board on a flat plane on glass on a hot plate and put a drop of strong hydroxide solution on each via hole and heat then rinse? Don't want to make large corrosive baths up. Also less masking.

author: IconicPCB
author_rank: Super Contributor
timestamp: February 19, 2019, 08:58:39 pm
content: The gun idea might work.There is a company using plasma in hard ish vacuum.They start with fr4 only sheet.Drill it and then it goes into the plasma chamber.A mixture of gasses is used to clean the fr4 sheet and hole walls and then a sliver of copper is evaporated in a tungsten crucible.The atoms are deposited allover the sheet.The sheet is ready for electroplating.It is then flash electroplated and from there on it is treated in conventional process including additional pating weight post masking.Advantages if this approach reduced chemical load at the end of process.On the question of base solution itis a mixture of two chemical sodium hydroxide and one other the name escapes me... let me have at least one coffee first ting in the morning.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 09:17:37 pm
content: I imaigned doing something like that with a 'vacuum kiln" but its a rather complicated apparatus.I made a ghetto gas diffuser a while back using those coffee straws and an old mini epoxy-can (the paste bondo stuff). I will try to flow some argon through it and blow a 'bridgewire' in front of the flow to see if the most crude way works first before I try to to make some kind of sealed focused apparatus (I have a feeling it might take a few iterations). I was going to use this just to see if I can make smoke laminarish.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2019, 09:18:30 pm
content: what is chemical load? The amount of chemicals that are stuck in the PCB and offgass?You can make super-bases, is it one of those? Maybe hydrogen peroxide and sodium hydroxide?

author: IconicPCB
author_rank: Super Contributor
timestamp: February 20, 2019, 02:39:25 am
content: Chemical load ...of waste byproducts.Regulation and disposal there of.The alkaline mix consists of sodium and calcium hydroxide. Dissolves glass.

author: coppercone2
author_rank: Super Contributor
timestamp: February 20, 2019, 02:44:26 am
content: any idea what the sodium hydroxide does to the epoxy? are any toxic compounds formed or can it be neutralized to salt, evaporated and burned maybe?