A three-dimensional circuit module includes z-axis connection pins, such as twist pins to electrically connect multiple, spaced-apart substrates, such as circuit boards. An expanding portion of a bulge of the pin mechanically and electrically contacts a corner edge of a via in a substrate without full insertion of the bulge in the via. Compression of the expanding portion of the non-inserted bulge establishes the electrical connection, which is also assisted by the longitudinal restraint on the pin relative to the substrate. Assembly and disassembly is facilitated without requiring the bulge to be fully inserted into the via.