Micromachining methods for fabricating micromechanical structures which include plunger elements free to reciprocate within cavities are fabricated using processing steps in common with those employed in high density interconnect (HDI) technology for multi-chip module packaging. A polymer, such as a polyimide, is utilized as a micromachinable material. In one embodiment, cavities are formed in the polymer material by laser ablation, employing a sacrificial layer as a mask. Electroplated copper may be employed as a sacrificial release layer. One particular structure is a micromechanical electric switch including an array of individual switch contacts actuatable in common.