I just came up with a new idea for PCB thru hole activation - Tell me what you think

idbruce

Thru hole activation has plagued me for a very long time, and I have been trying to come up with a sure fire way, which will accept either copper plating or solder. Anyhow, as I was sitting in front of the computer investigating homemade etchant, this idea popped into my head.....

Items Needed:

• Disc sander
• Sandpaper - grit to be determined through experimentation
• Large tray to act as a dust collector
• Piece of sturdy copper tubing or rod
• Sheet of paper
• Water soluble spray glue or even a tube, perhaps even Elmers basic glue (For the disussion, I will assume water soluble spray glue)
• Tube of crazy glue or super glue
• Razor blade or some other sharp squeegee
• Double clad FR4 PCB material
• Vacuum cleaner
• Bucket of hot water
• Small sharp awl or polished piece of wire

Procedure

1. Mount the predetermined sandpaper to the disc sander
2. Setup dust collecting tray near the sander to collect the dust
3. Turn on the sander
4. Run copper tubing or rod into the sanding disc and sand off enough to acquire a good accumulation of copper dust within the collector tray
5. Coat both sides of PCB material with water soluble glue
6. Before the glue dries, attach paper to both sides
7. Drill out all the necessary holes in the PCB
8. Squeeze out a fair portion of crazy or super glue onto paper clad PCB material
9. Using a squeegee or razor blade, fill all of the drill holes with the crazy or super glue applied in the previous step
10. Immediately suck out all the excess glue with a vacuum cleaner
11. Using a sifter, immediately cover the entire board with the copper dust collected in step #4
12. Shake of the loose copper dust (perhaps vacuum out the excess dust from the holes)
13. Allow the crazy or super glue to dry thoroughly
14. Soak the PCB in a bucket of hot water to remove the paper and remaining water soluble glue
15. Burnish all holes with a small sharp awl or polished piece of wire
16. Apply additional copper plating, perhaps it might even be solderable at this point

I have heard of using activation ink, but I have never heard or read of anyone attempting a procedure like this, so if this works, just remember you heard it from little old Bruce And if it does not work, well then someone is impersonating me

pjv

idbruce wrote: »

........ a sure fire way.....

That's a pretty tall order !

Bruce, how would you (electro) copper plate dust that is in non-contact to the next speck of dust, and is encapsulated in a coating of super glue ?

Others do something similar by smearing conductive glue/ink into the holes and vacuuming them out. Not too reliable from all reports, and for "sure fire", reliability is the issue. That reliability improves if one then electroplates the "glued" boards. But then again, subsequent etching removes most, if not all, the electroplating.

Been messing with this (commercial) process for some time, and a horrible mess it is, in my opinion..... send your boards out.

Cheers,

Peter (pjv)

idbruce

Peter

Bruce, how would you (electro) copper plate dust that is in non-contact to the next speck of dust, and is encapsulated in a coating of super glue ?

I would imagine that the burnishing that I suggested could quite possibly connect particle to particle and they would not be encapsulated in glue, only the outer most surface of each particle would be in contact with the glue.

In my opinion, it is worth an experiment just to test the theory.

T Chap

You ask what others think: Sounds like a perfectly good waste of time. Utter nonsense to be putting time towards this stuff.

jazzed

Just use rivets :-)

idbruce

Just use rivets

That is a nice alternative, but that stuff is expensive.

ctwardell

jazzed wrote: »

Just use rivets :-)

or not...

In a previous life doing TV repair I had the displeasure of working on many GE TV sets that used such rivets.

It was so bad that there was actually a hot line you could call for help. The rivets were numbered, you would tell the tech the symptoms and they would read off a list of which rivets to connect with jumper wires.

Given the potential self-heating on your high current board I would not suggest using rivets,

C.W.

Phil Pilgrim (PhiPi)

'Seems like way too much work for something that would have sketchy reliability. BTW, you don't have to have plated holes. DIPs and discrete components can be soldered top and bottom to make the connections. Vias can be connected with short pieces of wire. Some components like vertical headers and switches would be impossible to solder topsides, but you just keep that in mind in your layout and don't make throughboard connections with those parts.

-Phil

idbruce

Phil

Some components like vertical headers and switches would be impossible to solder topsides, but you just keep that in mind in your layout and don't make throughboard connections with those parts.

The headers, switches, and such are definitely the gotchas. All of your ideas are good and valid points, providing you have the board space to make it all happen.

Of course, this idea has not yet been tested, but as for "sketchy reliability", I would definitely agree, however, I believe that if there was good contact from one particle to the next, through a burnishing process, then I believe electroplating would make it reliable.

There is another question:

Without burnishing or electroplating, would the copper content of the hole be sufficient enough to allow solder to flow through, and if so, would the super or crazy glue melt, thus breaking the potential bond necessary for the solder to flow through? I don't expect an answer, I am just curious.

W9GFO

Copper dust is poisonous. I would imagine that the smaller particles would get past the shop vac filter.

idbruce

Rich

Copper dust is poisonous. I would imagine that the smaller particles would get past the shop vac filter.

I am sure it is However we are not talking about daily projects, maybe one or two a year. I am still worried about all the aluminum dust that I must have taken in.

Beau Schwabe

https://www.youtube.com/watch?v=s3GY-j4Gh0E

https://www.youtube.com/watch?v=9rME-XGCcCo

W9GFO

idbruce wrote: »

Rich

I am sure it is However we are not talking about daily projects, maybe one or two a year. I am still worried about all the aluminum dust that I must have taken in.

I was pretty sure you were aware of the poisonous nature of copper dust but I can imagine that many people aren't. After all, copper is used in pennies and water pipes so it would be reasonable to assume that it is safe. The number of people reading what we write here hugely outweighs the number of participants in this thread. I think it never hurts to point out potential safety issues.

idbruce

Beau

Funny thing.... I came across that first video yesterday, I only watched it for a minute or two, then just clicked it off. Since you mentioned it and linked to it, I watched both videos all the way through. Now that is definitely the way to go. Thanks for the links.

idbruce

Rich

The number of people reading what we write here hugely outweighs the number of participants in this thread. I think it never hurts to point out potential safety issues.

I agree whole-heartedly. Many times I mention safety issues and then other times I forget. I really need to pay better attention and provide safety warnings when appropriate.

Mark_T

Its possible to buy copper in nanoparticulate form, very expensive though...

Beau Schwabe

Bruce,

Also look into Chrome plating techniques ... Once you get to the electroplating stage, virtually any metal can be used/transferred. The key steps are applying a temporary conductive medium to something that is otherwise non-conductive that can withstand initial electrolysis currents without breaking down. Once initial deposits are made, the current can be increased to speed up the transfer.

erco

I'd suggest try painting a dab of some of this silly conductive glue, silver auto defroster fixer or conductive epoxy (carbon, silver or nickel) inside the hole before all that.

http://www.ebay.com/itm/USA-Conductive-Wire-Glue-Model-Railroad-Way-HO-Scale-Train-DCC-Locomotive-Wiring-/231262188884

http://www.ebay.com/itm/Nickel-Conductive-Epoxy-Heat-Cure-Electro-conductive-Nickel-Filled-2-5mg-1part-/161121872591

idbruce

Beau

Have you tried the method described in the videos? Additionally, have you done a lot of plating or just tinkered with it?

I have always been interested in plating and I know the basics, but just never got around to actually doing it yet. There was a point when I was actually looking for small crocks to hold various plating solutions, however it now appears that most people use plastic these days.

If I ever do get into plating, it will be on a very small basis, using small containers. In fact, the only thing that I really want to plate is circuit boards, but on the other hand, I would like to reverse the process, and strip gold plating from objects to recover the gold. Chrome plating would also be nice, but in that case, I believe it would have to be a much bigger operation to satisfy my wants and needs.

Duane Degn

While in college I read "The Electroplater's Handbook". It was intensely interesting (I majored in chemistry). One thing I recall (other than you can plate gold directly on iron) is there are lots of very nasty chemicals involved. I would strongly encourage you to learn enough about the chemicals involved to know how to safely dispose on them.

I find plating very interesting but I've never done it since I don't feel like I would know what to do with the waste (and I'm a chemist). I don't think there should be such a person as a casual electroplater. If you're going to do please do it right. Many of the chemicals involved are very toxic. A lot of these chemicals should not be poured down the drain and a few would do extreme damage to the sewage system if they were disposed this way.

Beau Schwabe

Duane,

A friend of mine used to work for DCI (Dura Chrome Industries) out of Oklahoma City... The process is very similar.

As far as doing any electroplating myself, I used to do this all the time when I was a kid with various keys we had ... drove my parents nuts, but it was easy to identify which key belonged to what if you knew the "pattern".... I got a little tricky with alternating different metals in the electroplating.

Tubular

The guys at Kinsten (Taiwan) may have a plating kit already, or before too long. The thing I like about it is that it requires minimal equipment - just the normal etching tank and heater, and a bunch of trays.

http://kinsten.com.au/pth/

A little while back I had a "brilliant idea" that if I used the really thin Kinsten (0.2mm), then my 0.5mm wide vias would be wider than the hole is deep, and I could just put a ball of solder on both sides, and it would "simply" connect through.

So I tried this... and for some reason, *no* conduction between the two sides. I don't know whether there's a layer of trapper air there, or something going on with the flux, or what, but it defeated me. I would like to revisit it with preheater and hot air and see if it can be made to work

jmg

This is all sounding like an argument to just do it properly. Low yields and high labour costs.

Tubular wrote: »

The guys at Kinsten (Taiwan) may have a plating kit already, or before too long. The thing I like about it is that it requires minimal equipment - just the normal etching tank and heater, and a bunch of trays.

http://kinsten.com.au/pth/

Not exactly cheap, so you can get quite a few real boards done for that price.

Tubular wrote: »

A little while back I had a "brilliant idea" that if I used the really thin Kinsten (0.2mm), then my 0.5mm wide vias would be wider than the hole is deep, and I could just put a ball of solder on both sides, and it would "simply" connect through.

So I tried this... and for some reason, *no* conduction between the two sides. I don't know whether there's a layer of trapper air there, or something going on with the flux, or what, but it defeated me. I would like to revisit it with preheater and hot air and see if it can be made to work

So you think the solder did not melt right through ? - it would seem that fully molten solder would have to connect ?

A variant on this, would be to use conductive paste only on vias, and reserve thru hole parts for bottom soldering only.


That simple rule avoids needing any cleaning, and blocked vias are no big issue, makes inspection easier and lowers the resistance too...

Conductive ink would work well with 3D printers too... - such a setup could even be used for SMD attach too, with the right curing ?

Some graphs are here
http://www.gwent.org/presentations/performance_vs_price_in_conductive_inks.pdf

WBA Consulting

You could always just do it the correct way: PCB Through-Hole Repair Eyelets.

Guide on eyelet installation from CircuitMedic:
http://www.circuitmedic.com/products/201-3140G.shtml

Eyelet Kit from CircuitMedic:
http://www.circuitmedic.com/products/201-3140.shtml

Eyelet Kit from BEST
http://www.solder.net/products/pcb-repair/thole-repiar-kits/

CircuitRework Guide on Eyelets
http://www.circuitrework.com/guides/5-1.shtml

Oldbitcollector (Jeff)

W9GFO wrote: »

Copper dust is poisonous. I would imagine that the smaller particles would get past the shop vac filter.

I came here for this caution.. Fiberglass dust isn't exactly recommended for breathing either.

Tubular

jmg wrote: »

This is all sounding like an argument to just do it properly. Low yields and high labour costs.
Not exactly cheap, so you can get quite a few real boards done for that price.

You're not wrong, it's about the same cost as a local pcb run. I'm happy with the speed and accuracy of the kinsten process, but would love to find a way to plate the holes...

So you think the solder did not melt right through ? - it would seem that fully molten solder would have to connect ?

I think something like that is going on. I was using copper planes on both sides which sink the heat away, but the solder did appear completely molted in the vicinity of the via hole. However while the solder on top appeared to be melting nicely, the solder on the other side would be cool, perhaps with something insulating on its surface, or trapped air, or something. Possibly the fibreglass (albeit thin) was repelling the solder a bit like it does on the flat

I didn't spend enough time on it. Clearly at some drill diameter it has to work.

A variant on this, would be to use conductive paste only on vias, and reserve thru hole parts for bottom soldering only.
That simple rule avoids needing any cleaning, and blocked vias are no big issue, makes inspection easier and lowers the resistance too...
Conductive ink would work well with 3D printers too... - such a setup could even be used for SMD attach too, with the right curing ?
Some graphs are here
http://www.gwent.org/presentations/performance_vs_price_in_conductive_inks.pdf

Yeah that's an interesting idea. Not sure if you mean solder paste to fill the vias or a conductive glue, but both are options.

For heated solder paste you could put the pcb hard against a backing so the solder didn't leak out of the via well. Cover the through holes with kapton tape and smear paste over the rest. You could do multiple passes easily until the via wells were filled. Would be interesting to see what the yield was like.


@WBA yes I have some of those little rivets, they are interesting and as you say would be good for repair. However I wouldn't want to do a whole board's worth of vias with them!