Oh sorry for not replying, I thought the forum would auto-notify me about any replys. Now I've configured my account to do so
Anyways, good job that you did there, congratulations!
Thanks, you also gave me some tips!
Are you (carloscuev) sucking ink through the holes with a vacuum? it appears mamalala isn't. Also would be interested in hearing if either of you has experimented with limited -or asymmetric AC instead of pure DC to achieve a smoothing action.
In my case, the Indian Ink is too thin so if I suck the ink with a vacumm I'm left with a very thin layer with high resistance, I use a booger sucker haha (see attachment)
just to unclog the holes because if curing with the holes cloged of ink, it will dry clogged. So that way, with a fat layer of ink in the hole, when curing it deposits a nice conductive layer. As mamalala said, his conductive ink mixture is about warm-honey viscosity so in his case, vacumming the holes is the way to go.
I just went to my local art shop and got a bottle of Daler Rowney FW Acrylic Black ink and did a quick test. Without any graphite, I can get a about 500 ohm resistance in a 1mm hole using just the ink. Probably lower with a second coat.
About the Asymetric AC, I haven't done that. To get smooth copper deposition you need a surfactant in the solution, I use Polyethylene Glycol 6000 (buy it on ebay) and mamalala uses Tween 20
Does that sound like enough to be useable or do I need to get a resistance down in the low ohms?
500ohm in a 1mm hole of 1.6mm PCB is what I'm getting
so it's enough. Proportionally we're talking about 1kOhm for a 0.5mm hole and so on. And as SeanB said:
500R is fine, start at a very low current and slowly ramp it u with time, pull the board out the first few times and look to see when you get a full coat of copper then you can ramp it up.
Yes, I start at 25% of my calculated current, and ramp it up 25% every 10 minutes until I get to 100% By the time I've reached that point I can see in the microsope a lot of particles of copper already deposited over the ink, looks rather beautiful
Noob question, once the holes plating is done, how do you cover or seal those holes at the pcb traces etching process ?
I cover them with paint, the same process of the conductive ink but now with paint to mask them from the acid. I got this idea from a youtube video, keep reading this reply for the link please.
Yes. Use dry-film resist. Laminate it onto each side of the PCB, then expose and develop. That stuff is called "tenting resist" for a reason: it will tent over the holes 
Then etch the board and strip off
I'm using dry-film resist, but big holes don't get tented, however my smallest ones (0.5mm) do get tented
, but anything up from there won't, what dry-film resist are you using?
Some very valuable notes (I think):
About the process in general:
As amspire I had dismissed the idea too, until I saw this video:
http://youtu.be/bD9imNIkTKM and browsing that user channel found this one too:
http://youtu.be/KTNuTv_IQp4 If you're interested in plating vias at home it's a good idea to watch them too. Here they cite this thinktink website (
http://www.thinktink.com) that has lots of valuable information.
About curing the ink:
When using just indian ink, as in my case Higgins Black Magic with no added graphite there's a problem. If you cure the board too fast you'll get a thin non conductive layer on top of the ink, I think it's because this ink has some acrylic compund or something and if you cure it too fast you'll have good conductivity from layer to layer, but the copper won't deposit. I observed this because doing a test I cured it with a lighter, raising the temperature very fast, I could see the ink bubbling on the big holes. And then when plating no copper was adhered to the surface. So I changed to curing it with a heatgun slowly ramping up the temperature (1 min) and then letting it cool down. You'll see that the conductivity gets very affected with the curing temperature you're using. I'm looking to do further tests with and temperature controlled oven to find out the best curing temperature and ramp-up time for this ink. Also as I mentioned, I've got (from ebay too) 5 micron graphite powder, I'll run some more tests. Here's the 5 micron graphite from eBay:
http://www.ebay.com/itm/121066283612About the anodes
Make an effort to get Phosphorus-Copper alloy anodes, search for electroplating shops in your country, search in alibaba and ask for a sample (almost always you pay shipping) or do anything you can to get them, the results are way better than using other types of anodes. The guy from the youtube video says he found Phosphorus-Copper pipe in Home Mart being sold as heat exchange pipe or something like that, watch the video. The small anode I got from the local electroplating shop looks very ugly because it's used and highly eroded, but produces amazing results, I'm looking forward to buy more, I've phoned them and I got the addres of their provider. I attch a picture of the ugly but magic anode. Also in order to keep your plating solution usable for long time you'll need Polypropylene felt bags to cover the anodes as the anodes will generate a black slug and you don't want that in you solution. The local electroplating shop has been using the same solution they first made since 1994! Again, in the youtube video you can see how they look like.
About the plating solution
In the thinktink website you can get the recipe (
http://www.thinktink.com/stack/volumes/voliii/consumbl/cplatmix.htm) for the solution. And as the user in the YT video says, instead of that rare Copper Gleam GLX as surfactant, you can use Polyethylene Glycol 3350 available at drug stores, even in my country (Mexico) I was able to find it, then I bought from ebay Polyethylene Glycol 6000 but both of them work well, haven't made a deep comparison of results but they were at plain sight the same. The problem I had is that I got 98% sulfuric acid instead of 35% and the problem is that this ratios are not volumetric, they are mass rates, so for a 35% sulfuric acid, 35% of its weight is sulfiric acid, and the rest is water, but pure sulfuric acid has a density of about 1.84g/cm³ so the calculations turn out to be a bit harder than expected when not dealing with the concentrations of that recipe. However I studied some days a bit of chemistry and made a PHP script to easily find the right amounts, you can find it here:
http://escalalibre.com/edwt/ just click in "
6. Via Electroplating Solution Calculator" and fill the requested fields according to the chemicals that you can get and hit "Calculate" to get the volumes and weights of each component for a specified amount of solution.
Very Important Note: as you can see, the amount of HCl is very small, but AFAIK is very critical not to mix more than the specified amount of Cl
- ions, as a tip, if you got 35% HCl, you can mix in a separate container 34 parts of distilled water by weight to 1 part of 35% HCl by weight, with this you have 1% HCl so if you recalculate for 1% HCl using the web tool, the quantity of 1% HCl would be higher and more manageable than using 35% HCl.
About the plating time and layer thickness
In the thinktink website you can read about this:
http://www.thinktink.com/stack/volumes/volvi/copplate.htm but I'm not sure if the same would apply if not using their Copper Gleam GLX surfactant, something tells me it doesn't matter, so I also made a simple calculator for the plating time and current. Again, you can find it by going here:
http://escalalibre.com/edwt/ and clicking in "
7. Via Electroplating Current and Time Calculator" and as you can read there, the current density is recommended to a maximum of 20 amps per square foot (ASF)
Hope all of you can find this large post useful.
Cheers!
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