Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

The PCB “Via Press”

Posted by retromaster on August 18, 2009

 

When designing double-sided PCBs, it’s crucial to be able to place vias underneath SMD ICs. Otherwise, the boards become too difficult (not to mention ugly) to route. This presents us with a problem when making those boards at home, however. A via must protrude from the board only very little, otherwise it cannot be placed under an IC (So, placing copper wire in the via hole and soldering both ends is out). Since it’s very difficult (almost impossible for most people, including myself) to reproduce the through hole plating process at home, I’ve been investigating practical ways of making vias that can solve this problem.

The best solution I’ve come up with so far  is using “mechanical vias”. In a nutshell, I place a small piece of copper wire in the via hole. It needs to be a tight fit so that it won’t slip out of the hole. I trim the ends of the wire so that very little (perhaps less than a millimeter) of it sticks out of the hole in both sides. Then, I place the board in something like a vice (what I referred to as a “via press” in the post title) and applying pressure to the board crushes both ends of the copper via and produces what seems like a reliable connection between the two sides.

I built a device out of aluminium (see photo) that can be used as a “via press”. I place the board in this press, sandwiched between two stainless steel plates (aluminium itself is too soft to crush the copper wire). The jaws of the device are more than 17cms wide so it can accomodate reasonably large boards. As you can see from the photo(s), the workmanship is far from perfect, but it works and I guess it’s alright given my (lack of) tools and prior experience when it comes to metalworking. Lots of vias can be made in just one pass using this device. So far, as it can be seen from the photos, this method seems to be quite successful :).

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8 Responses to “The PCB “Via Press””

  1. John said

    Nice tool! Can I have a layout for this project? I am building a double sided board and having troubles in making the vias… Hope this helps! Thanks!

  2. retromaster said

    Well, I am afraid I haven’t made any layouts or drawings for this project. Everything’s in my head, really :) But I’ll be glad to answer any specific questions you may have, or to add more photos if you think seeing the device from different angles would help.

  3. John said

    Yes please for the photos from the different angle. and by the way how the screw is attached to the stainless steel and the aluminium ( the part in the middle). Thanks!

  4. retromaster said

    The aluminium part in the middle has a non-threaded hole on the top through which the screw passes. The hole in the aluminium part at the top (in the frame) is threaded. The nut seen in the middle is a “nylon insert lock” type, so it sticks to the screw. It freely turns in the large window in the middle part when the screw is turned.

    When the screw is turned right, the bottom end of the screw pushes against the bottom wall of the window and presses the steel plates together. When it is turned left, the top side of the nut pushes against the bottom wall of the window and lifts the part in the middle upwards.

    The stainless steel plates are not attached to the device, the idea was to screw them on to the aluminium jaws of the device but I did not do it in the end, as it seemed to work just fine as is.

    I hope these explanations helped. I’ll take and add some more photos when I have the time.

  5. Dale said

    Nice job. How did you make the grooves in the upright piecse and the tabs on the horizonatal parts that ride in the groove.

    Thanks.

  6. retromaster said

    I used a Proxxon MF70 mill.

  7. Dale said

    Thanks for the reply. That mill looks like an awesome tool to have. I don’t have a mill but I do have a welder so I started fabricating my own press.

    Half way into it I was struck by inspiration and found that my “welding clamp” worked very nicely as a hand held press to rivet the vias.

    Thought I would share that as an alternative to the press.

    The following line shows a clamp very similar to what I tried:

    http://www.lowes.com/pd_91323-281-20D_0__?productId=3121711&Ntt=vise+grip&pl=1&currentURL=%2Fpl__0__s%3FNtt%3Dvise%2Bgrip

  8. retromaster said

    Actually, my “inspiration” for the via press was a machine vice. Obviously, with a machine vice one can only make vias on tiny boards, but it was quite useful for testing if the idea was worth implementation.

    Thanks for sharing.

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