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 :).