Hi Paul-

A fascinating application!

When plating copper into vias is not possible, or is inconvenient, "macro-scale" designs use eyelets.  You can't attach to inner layers reliably with them, and I always found the external contacts to be unreliable as well, so we made sure they were soldered on both sides.  But they can look a lot more professional than braid, and lend themselves to automation.  I presume that your application would be much tinier than any commercial eyelets and tooling sets could handle, but theoretically you could probably come up with something like that.

Another possibility might be an organo-metallic paste like ORMET sells, or perhaps some kind of sintering nano-metals.  But either of these options would probably have trouble getting through the aluminum oxide to make a connection without some kind of assistance from a suitable flux.  Probably a lot of risky development would be required for this path, but it has the potential to be scalable down to your preferred geometry.

Yet another possibility is that aluminum is commonly sputtered onto silicon wafers, so why not get it deposited into the holes?  Activation and masking problems, but the prettiest and easily scalable to tiny geometries.

I don't understand your process (I'd like to get the little guide available on your company's website, but for some reason it either isn't sending out the email or my spam filter is eating it).  But another way people build interesting boards is to put the vias in before the outer metal goes on.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Jackson
Sent: Thursday, February 27, 2014 2:31 PM
To: [log in to unmask]
Subject: [TN] Aluminum fine-line PCB

Hi All,

I'm new here to Technet so I'll ask you to be gentle, at least at first. 
We are manufacturing fine-line aluminum trace PCBs and our customers are mainly wirebonding chips directly on the aluminum and attaching components on selective copper pads. We are trying to find a more elegant way to achieve through-hole connectivity than our current method of filling vias with solder wick braid and aluminum solder paste. It works but it's "fugly". The aluminum is 30µm and the dielectric is typically 2.1mil. Any ideas would be greatly appreciated.

Paul Jackson
Omni Circuit Boards
(855) 798 9717
*w*ww.omnicircuitboards.com


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