A tester apparatus, comprising: a portable supporting structure suitable for holding a substrate carrying a microelectronic circuit and having a plurality of terminals on the substrate connected to the microelectronic circuit; a plurality of contacts on the portable supporting structure, the contacts suitable for matching the terminals for making contact to the terminals; a plurality of lands forming a first interface on the portable supporting structure and being connected to the contacts; a stationary structure that includes a frame, an actuator and a holding structure, the portable supporting structure being receivable to be held by the holding structure of the stationary structure and being removable from the holding structure of the stationary structure; a plurality of members forming a second interface on the stationary structure, the members having contact surfaces that match with the lands and are resiliently depressible by the lands allowing for relative movement between the portable structure and the stationary structure, the second interface being connected to the first interface when the portable structure is held by the stationary structure and being disconnected from the first interface when the portable supporting structure is removed from the stationary structure; an actuator having first and second actuator pieces that are actuable relative to one another to move the portable supporting structure relative to the stationary structure and engage the first interface with the second interface; an electrical tester connected through the second interface, the first interface, and the contacts to the terminals so that signals are transmitted between the electrical tester and the microelectronic circuit to test the microelectronic circuit; and a thermal chuck mounted to the frame of the stationary structure, characterized in that, the tester apparatus is configured such that, upon actuation of the actuator, the portable supporting structure and frame of the stationary structure move relative to one another to engage the lands of the first interface with the contact surfaces of the members of the second interface, the said relative movement of the portable supporting structure and frame of the stationary structure relative to one another engaging the thermal chuck with the portable supporting structure. a portable supporting structure suitable for holding a substrate carrying a microelectronic circuit and having a plurality of terminals on the substrate connected to the microelectronic circuit; a plurality of contacts on the portable supporting structure, the contacts suitable for matching the terminals for making contact to the terminals; a plurality of lands forming a first interface on the portable supporting structure and being connected to the contacts; a stationary structure that includes a frame, an actuator and a holding structure, the portable supporting structure being receivable to be held by the holding structure of the stationary structure and being removable from the holding structure of the stationary structure; a plurality of members forming a second interface on the stationary structure, the members having contact surfaces that match with the lands and are resiliently depressible by the lands allowing for relative movement between the portable structure and the stationary structure, the second interface being connected to the first interface when the portable structure is held by the stationary structure and being disconnected from the first interface when the portable supporting structure is removed from the stationary structure; an actuator having first and second actuator pieces that are actuable relative to one another to move the portable supporting structure relative to the stationary structure and engage the first interface with the second interface; an electrical tester connected through the second interface, the first interface, and the contacts to the terminals so that signals are transmitted between the electrical tester and the microelectronic circuit to test the microelectronic circuit; and a thermal chuck mounted to the frame of the stationary structure, characterized in that, the tester apparatus is configured such that, upon actuation of the actuator, the portable supporting structure and frame of the stationary structure move relative to one another to engage the lands of the first interface with the contact surfaces of the members of the second interface, the said relative movement of the portable supporting structure and frame of the stationary structure relative to one another engaging the thermal chuck with the portable supporting structure.