Via press crushes copper to make a mechanical connection

via-press-in-action

[Jay] was looking for a way to make his own vias on homemade double-sided PCBs when he stumbled across this post from about five years ago. The technique shown here makes mechanical vias and was developed by [Retromaster]. There’s no soldering involved, instead he uses some solid core copper wire and a press to crush it tightly against the board.

The press is made from aluminum stock, with a couple of plates of stainless steel which come in contact with the board. The aluminum stock is easy to work with, but it’s relatively soft which is the reason for the addition of steel. He uses copper wire which already fits tightly in the hole through the substrate. After clipping off the excess as near to the board as possible a trip through the press leaves each side flat as shown in the inset image.

We looked through some of the other projects we’ve seen from [Retromaster] like the Atari 2600 in an FPGA and this emulated Amiga floppy drive. But we didn’t see any diy boards where he used this crushing technique.

Comments

  1. Woah, that’s really clever, and it works a hell of a lot better/cleaner than I would have thought! Too bad I already invested in through-hole rivets… :|

    Now if someone would post a design for a DIY press for setting THOSE…

  2. svofski says:

    I use the same technique except that I just hammer the pieces of copper wire (usually legs of old useless capacitors). I found out that it’s still necessary to solder the joints properly, sometimes they look perfect but there would be no contact.

  3. Dax says:

    I think you’re still going to have to solder the riverts in place or else the inevitable oxidation in between the contact can really ruin your day.

    That said, you could try to fashion a copper plug that is just as long as the board is thick, and applying a tiny bead of solder on top.

  4. Sven says:

    This is called riveting, not pressing afaik. Pressing would be just forcing the copper wire into a tight hole without deforming it.

    If done properly (with enough force, and with the same metal in the rivet and the board) the metal to metal contact should be good enough to not develop bad contacts for several tens of years.

    Still, i don’t think this is either faster or more compact than just drilling 0.4mm holes, threading a 0.3mm wire back and forth through all the holes, soldering both sides and cutting away the excess loops. The only advantage i can see with these riveted solid copper vias is that they might be usable as thermal vias for chips with soldered pads underneath.

    • The main problem with this method is the lack of through plating. This means the only connection is the pressed flare of the copper ‘rivet’. This thin connection can gradually oxidize over time. Soldering afterwards is a good idea. If there is to be a chip mounted over the ‘rivet’, use a higher melting point solder and wick away the excess or you will get a capillary dome forming under the chip which could float it if the low melt point SMD solder is used. You can also buy via rivets made for this application.
      Here is a search for images of this task, click on any image to get into the details.

      http://tinyurl.com/agxg4gt

    • RoadWarrior222 says:

      8-15 years IMO, based on number/age of cars known to need dashboard PCB R&R when this technique used in construction. Also used in some lighting panels, and other stray places in a vehicle.

  5. Simon says:

    Push a veropin through a hole, snip to size, dab of solder. Job done.

  6. Natalie says:

    would be tempted to turn this to a spot welder of sorts, not sure how well that would work on PCB’s…

  7. fartface says:

    Very old school. we used to do this back in the early 90’s. Except no press. I would just use a small ball peen hammer and smack each via lightly on a vice. Then we would solder the vias on each side anyways.

    • flink says:

      In navy soldering shops we used a jeweler’s anvil with a pointed center punch to flare a rivet and then a flat punch to set the end flat. A touch of solder after that and the job was done. I wish I had a dime for every new via rivet I’ve set. I spent 3 1/2 years soldering and doing board rework. I love the smell of burning resin flux in the morning….

  8. Chris says:

    I wonder if you’d be able to use the drill files and create a CNC controlled machine that would drop in a solder covered rivet or wire. Place them all (PnP style) and then reflow the board, possibly at the same time as other components.

  9. Bob Spafford says:

    Actually, a drill press which might already be in your shop will generate all the force you need.

    Warning! Solder will flow when forced gently, given enough time.. I was once responsible for servicing an instrument which had a memory failure. I found a short on a bit line, so I replaced the driving chip, no fix. I replaced the receiving chip, no fix. The wave soldered board appeared to be absolutely perfect. After much head scratching, I finally removed a plastic protector supported on Teflon spacers, and found the problem. The Teflon had exerted pressure on the solder which covered the full length of the trace. And hidden under the Teflon, I found that the solder had flowed out sideways until it contacted a neighboring trace.

    It had taken 18 YEARS of pressure on the solder bead before the short occurred!. Also, 100 year old stained glass windows often show sagging glass from flowing solder. Just be aware that given even slight forces, solder NEVER STOPS MOVING!

  10. Peter says:

    Is a custom press actually necessary? Can a normal vise be used instead?

  11. johnmeacham says:

    mechanical cold welding can be a very robust electrical connection. It is one of the reasons wire-wrapping is still used in certain designs that require high reliability.

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