Plated through hole activator solution

[amushrow]

And that's solution in both senses of the word.

Now I know most people don't bother making their own PCB's due to the cost and the faff of it (mostly the faff) but I found it interesting so I was doing it anyway, and I got hung up on having plated through holes for a double sided board. There is a solution you can make up yourself but it required an expensive and difficult to obtain chemical (Calcium Hypophosphite), and so I sought to reduce the cost.

To cut the story short I was able to make the same solution through a different method with cheaper stuff.
I've also been able make a powder (well, pretty blue crystals) of the stuff which can be re-hydrated with household ammonia.

What I was wondering is if anybody else is even interested in this.
If so I'll put together a little guide on it, and if people are interested in buying some of the dried product I could price that up.

Youtube Link to the original solution:

Basically once you have made up the solution you dip your board into it and some of the solution gets caught in the holes, you then cure it in an oven and you have a reasonably conductive layer in your holes. You'd then have to electroplate the board to cover the holes properly in a thicker layer of copper, so it's not really for everyone (although doing some simple plating isn't that difficult)

[Mark]

Thank you amushrow! 

Yes there are people interested and I am one of them.   

At them moment I use the bungard copper rivets with good success (even placing them under a 56 pin VQFN with ground pad) but I'm always interested in new methods.  Any help or guidance would be appreciated.   

[mikeselectricstuff]

With cheap Chinese CNC engravers available to do the drilling ( if not the routing - seperate issue!), homemade DS PCBs may be more useful if there's a sane way to do plating.
 

[mikeselectricstuff]

Protecting the hole plating during etching is going to be an issue, so usefulness maybe limited to milled PCBs.
You're also going to need to drill, electroplate plate, then mill, so will need to use a jig & pins or similar to re-align the board,  for milling after plating,though you probably need that anyway for double sided milling.
Unless it's  simple PCB where you can runn all tracks to a common bar to connect them for plating.
   

[amushrow]

Protecting the hole plating during etching is going to be an issue, so usefulness maybe limited to milled PCBs.

Perhaps, but protecting them wouldn't be an issue if you're using photosensitive film on the pcb which is able to cover right over the holes (of course you'd need more chemicals to work with that; although nothing expensive or dangerous, well not too dangerous)

[bluscape]

Hi,

I'm very interested. I've been battling for the past three weeks to get consistent results using graphite powder and acrylic ink.
Please do share.

BTW. This guy has a very nice article on plating, micro etching and manufacturing of 4 layer boards:

http://www.hebertlabs.com/projects/project%20reports/electroplating%20through%20holes%20and%20vias.htm

Thanks in advance!

[jmelson]

Protecting the hole plating during etching is going to be an issue, so usefulness maybe limited to milled PCBs.

Nope.  You have to go to a different process, though.  You start out with very thin copper, like 1/10th ounce.  You drill the blank panel first, using entry and exit material to prevent burrs on the copper.  Then clean up the surface a bit with Scotchbrite or similar mild abrasive.  Laminate dry film resist in the negative of the usual, ie. the resist covers where you want NO copper.  Then, electroplate the panel and holes to desired thickness.  Then, strip the resist and dip in etching bath for just a few seconds, then rinse like crazy to remove any etchant that might have settled in the holes.

I have not done this, but have put dry film over drilled, double-sided boards that I then soldered via wires through.  But, it proved that the resist could "tent over" the holes very reliably.  I guess with the plate first and then etch away the foil method you don't even have to worry about the tenting.

Jon

[bluscape]

I've seen the commercial PCB manufacturers use a thin sheet of aluminium to prevent burs. Just place it on top of the laminate and drill. Off course  the most important thing is to always use sharp drill bits.

[deepfryed]

Just came across this while searching for something else, hopefully useful for someone.

1. Drill holes
2. Activate holes and electroplate with copper
3. Mask off the regions you want removed
4. Tin plate the remaining areas, including the through holes - the tin plating protects the copper in etchant
5. Strip off mask
6. Etch copper off

This way you don't need to worry about tenting the holes.