A pinned interposer and mating sockets to facilitate removable mounting of high connection density micro devices between a pair of substrates in compact electronic circuit packages. The pinned interposer has an inner set of contacts, typically in a rectangular array, that, in cooperation with a mating socket, allows pluggable connection of a micro device such as a MEMS device connected to a first printed circuit substrate. An outer set of contacts on the interposer provides electrical interconnection between the first substrate and a second substrate located atop the high connection density micro device, thereby effectively sandwiching the micro device between the first and second substrates. The outer set of contacts may be disposed in a circular array.