DIY plated through holes

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DIY plated through holes

Postby bearmos » Wed Jan 18, 2012 10:12 pm

I just finished writing up some of the details on DIY plated through holes. This is what the simple constant current source was designed for. This process was slightly adapted from Think and Tinker - a really great site for DIY PCB fab. The overall process is:
1. Drill holes in the PCB
2. Coat the holes with a mixture of water-proof ink and finely powdered graphite
3. Cure the ink so it doesn't rub off
4. Dunk the PCB in the electroplating tank, apply current, and let chemistry do the rest of the work.

Here are the pages of interest:
- electroplating (part 1)
- electroplating (part 2)
- electroplating (part 3)
- electroplating (part 4)

Overall, the process is a lot simpler than I expected. Here are some pictures for a quick overview:
The bath ingredients. ..notice nearly every chemical there has a pretty serious warning on it. . .please, take these seriously. . .:
Image

Slopping conductive ink (all over the PCB to "activate" the through holes:
Image

The same board, after getting the top layer of ink carefully removed (for the most part):
Image

Plating in progress, using the simple constant current source previously made:
Image

And some plated through holes:
Image

It should be noted that this is something that needs to be done *before* traces are etched into the PCB because the electroplating relies on current passing through the work-piece to deposit the copper ions onto the PCB. If the board is already etched, anything not touching the cathode clip won't plate properly. If you'd like to do PTH's with an etched board, you'll need to pattern plate tin solder or bright tin first (see think and tinker for details). This tin plating will also coat the insides of the PTH's so the copper doesn't disappear, since the tin acts as an etch resist.

The copper doesn't come out all that "bright" (probably because the bath lacks brighteners and anode bags). But, this sure beats soldering individual wires through vias, and I can put them under IC's now without any hassle - all this while still getting my board done the same night!
Last edited by bearmos on Thu Jan 19, 2012 3:06 pm, edited 1 time in total.
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Re: DIY plated through holes

Postby tayken » Wed Jan 18, 2012 11:29 pm

Wow! Kudos! I was considering the same thing during the time I was fabbing at home (nowadays impossible, landlady will surely get mad, nice thing she never sees my workbench). One question: How long does the plating process take from start to finish? I saw the calculations but how long does it take to cure the ink for example?
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Re: DIY plated through holes

Postby bearmos » Thu Jan 19, 2012 12:08 am

tayken wrote:Wow! Kudos! I was considering the same thing during the time I was fabbing at home (nowadays impossible, landlady will surely get mad, nice thing she never sees my workbench).

Thanks, I realize a lot of people will probably think this is silly because of how cheap PCB's are now. . .

One question: How long does the plating process take from start to finish? I saw the calculations but how long does it take to cure the ink for example?

I throw it in the toaster oven (not used for food) for a 15-30 min at ~90-100C or so (I think that 30 min @ 100C is recommended). I haven't done a whole lot of experimentation here to see what the minimum time is though - I always have other things to keep me busy:)

I've never actually done a stop-watch style test, but some estimates for the total time to plate a board is probably:
- 5 minutes max to slop/vacuum ink
- 30 minutes curing in the oven
- 5 minutes to clean off sides of board
- 1 hour plating, depending on current used, desired thickness, etc.

So it looks like the whole thing is well under 2 hours, 10 minutes of which is actually hands-on work. Sure beats the hour+ hunched over a workbench soldering all those vias:)
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Re: DIY plated through holes

Postby Zeta » Thu Jan 19, 2012 7:49 am

Nice.
I have thought about electroplating to do PTH ever since we did some stuff with electolysis at the university lab but it is really hard to get the right chemicals without a permision.

bearmos wrote:Thanks, I realize a lot of people will probably think this is silly because of how cheap PCB's are now. . .

I have to wait 1 moth or more to get anything from seed/itead so dong it at home is the best option for me.
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Re: DIY plated through holes

Postby bearmos » Thu Jan 19, 2012 8:28 am

Zeta wrote:it is really hard to get the right chemicals without a permision.

Here in the US, the chemicals are as easily had as going to the nearest home improvement store/autoparts store. The only thing that is remotely "special" is the PEG (which can be had on ebay, of course;-)), but it's also commonly used in laxatives, handcream, etc - although whatever else is in those products would probably contaminate the bath. . . I'm not sure what it's like in other locals - it continually amazes me how it is to get some basic chemicals in some places. . .

The trick with implementing this is that you'll need to protect the PTH's before chemical etching.
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Re: DIY plated through holes

Postby Zeta » Thu Jan 19, 2012 1:57 pm

in a country where a smart kid can use Muratic Acid and Sulfuric Acid to make a nasty drug the government tries to have tight control over what chemicals you buy (of couse the government always fail)

btw, what is ZAPS (Root Kill)? what is it used for? google didn't help.
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Re: DIY plated through holes

Postby hak8or » Thu Jan 19, 2012 2:39 pm

Awesome! I always wondered how someone could get plated through holes on pcb's at home.

bearmos wrote:Thanks, I realize a lot of people will probably think this is silly because of how cheap PCB's are now. . .

One can never doubt the advantage and increased drive knowing that you can have a working PCB by the end of the day or in a few hours compared to having to wait for a PCB to get to you in days if not weeks. :P

Also, one of your picture links are not working.
http://twilightrobotics.com/images/stor ... eview2.jpg
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Re: DIY plated through holes

Postby bearmos » Thu Jan 19, 2012 2:40 pm

Zeta wrote:in a country where a smart kid can use Muratic Acid and Sulfuric Acid to make a nasty drug the government tries to have tight control over what chemicals you buy (of couse the government always fail)

btw, what is ZAPS (Root Kill)? what is it used for? google didn't help.


Yeah, I can go to the auto parts store and pick up some Sulfuric Acid and nobody bats an eye. . .yet when I go to the drug store coughing up a lung and try to buy cough syrup, I get asked for ID to make sure I'm over 18. . .

ZAPS is a misspelling of ZEP's (sorry about that!) - a brand of "root killer" - which is Copper Sulfate Pentahydrate It's meant to be poured down a toilet drain and flushed into the sewer system in order to kill tree roots that are growing into the pipes.

Here's a link and description for the real product:
http://www.homedepot.com/buy/cleaning/drain-openers/zep/2-lb-root-kill-62964.html
Zep 2 lb. Root Kill is an effective solution for ridding your sewer pipes, drain and septic field lines of shrub and tree roots. The powerful granular formula dissolves these pipe-clogging elements on contact without harming the target tree or bush.

Dissolves septic systems clog-causing roots
Powerful granular formula dissolves roots without harming shrubs or trees
Protects pipes from corrosion
Promotes root and fungus control within sewage system
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Re: DIY plated through holes

Postby charliex » Sat Jan 21, 2012 5:31 am

its funny i think you have almost exactly the same supplies we do, zep from home depot and the acid from the autoparts store.. nobody batted an eyelid at the 5 gallons of sulfuric acid.

the RP power supply is in process, hopefully we'll get it up and running soon. this should really help us fix the unevenness we were getting in the plating, it made it really hard to cnc the board on one side, at first it was really great then something happened and the boards started to plate unevenly, one of our guys is a a chemist so he went over and over it, we tried just about everything.

Tonight we met a guy who works in the etch-ant chemical business, we're hoping he'll spill some of the insider secrets on the chem, since otherwise it can be 55 gallon drums!

i'll have to write out some more of the notes we took on the process, i left a link on the blog article

cheers
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Re: DIY plated through holes

Postby bearmos » Sat Jan 21, 2012 3:22 pm

charliex wrote:its funny i think you have almost exactly the same supplies we do, zep from home depot and the acid from the autoparts store.. nobody batted an eyelid at the 5 gallons of sulfuric acid.

Yep, these were the suggestions of the original guide I was following from Think and Tinker (link in original post). I saw PEG mentioned several places, low and behold, ebay had some for under 10 bucks. I think I only used a quart of battery acid - I think you guys are doing things on a bit bigger scale:)

charliex wrote:the RP power supply is in process, hopefully we'll get it up and running soon. this should really help us fix the unevenness we were getting in the plating, it made it really hard to cnc the board on one side, at first it was really great then something happened and the boards started to plate unevenly, one of our guys is a a chemist so he went over and over it, we tried just about everything.

I saw what looked to be an h-bridge breadboarded on your wiki - i'll be curious to see how much of a difference this will make. Another tip from Think and Tinker is bubble sparging, as well as anode bags (under 10 microns I think). The idea is to constantly filter the bath so you don't wind up with any large particles - I think they recommended this for usage more often than once a week.

charliex wrote:i'll have to write out some more of the notes we took on the process, i left a link on the blog article

It looks like you're using Janus Green B as a brightner - I was wondering where you sourced this? It looks fairly expensive at $55 for 5 grams, I forget where I was looking now. . .I'm generally not terribly concerned with how nice the boards look, since they're just quick proto's, but it seems like the brightner would also allow for faster plating and better adhesion of copper plating. I've found that if I go much more above 10ASF then I wind up with lots of uneven copper on the work piece that can simply be wiped off. As long as I'm 10ASF or under, things turn out OK though.

I also found this site that sells full kits - just add your own battery acid - they a bit expensive - the interesting part is that they sell brigheners for around $10 that will cover 1.5 gallons of plating solution. Interestingly enough these are labeled non-hazardous, which is encouraging vs. the Janus Green B I vendor I found - which won't even deliver to residential addresses (I havne't looked into the nasty details of either of these compounds yet). I suspect that one of these "brigheners" is actually a leveler, but I haven't contacted them yet to do any digging. The bath composition in the kit seems to be pretty standard, so I'm thinking I can probably use their ready-made brighener packs, as long as I don't wind up adding too much PEG.
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Re: DIY plated through holes

Postby charliex » Fri Feb 03, 2012 12:18 am

janus green b, a chemical supply place in the city of industry, can't find the name.
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Re: DIY plated through holes

Postby bearmos » Sun Feb 05, 2012 2:45 pm

cool - I'll probably pick some janus green b up, the guys from the kit place were no help at all (they wouldn't give any hints as to what was in their mixes or what I should buy. . .
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Re: DIY plated through holes

Postby charliex » Wed Feb 08, 2012 10:34 pm

thats pretty much what we found too, the secret sauce is all black box, its the same for ferrofluid suspensions.
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Re: DIY plated through holes

Postby cpirius » Wed May 30, 2012 8:04 pm

I'm not sure what kind of PEG to get. It looks like it comes in different molecular weights? At least that's what I think the number by the PEG is for.

I couldn't find it listed anywhere in the write up. The picture shows what looks like 3350, which I only see on eBay in the form of MiraLAX Laxative Powder. eBay options seem more limited than they where before. Anyone have a suggestion for where to get PEG?
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Re: DIY plated through holes

Postby bearmos » Wed May 30, 2012 9:17 pm

You're correct, PEG with molecular weight of 3350 was used in the write up. I think charliex just used laxative (commonly available in local stores in the US). When researching this, I couldn't really find a lot of specifics on the exact use of PEG - quantity or molecular weight.
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