A multiple mode buckling beam probe assembly

Claim 1

A multiple mode buckling beam probe assembly (50) for testing electrical characteristics of integrated circuits connected to pads (60) on a semiconductor chip substrate (58), said assembly being characterized by: a space transformer die (52) movable relatively towards and away from said substrate and spaced therefrom, said space transformer die bearing potted wires (54) forming laterally spaced contacts (56, 56') facing the substrate chip pads with said contacts being in general axial alignment with said pads, respectively, first (70) and second (74) planar locating guides positioned between said transformer die and said substrate relative to said movable die and being in juxtaposition respectively with said transformer die and said substrate, said first and second locating guides having holes (72, 76) therein aligned with respective contacts and pads, at least one planar locating center guide (82) in fixed relationship to said movable die, positioned intermediate of said first and second planar locating guides and spaced therefrom and having correspondingly sized holes (84) extending therethrough aligned with the holes of said first and second planar locating guides, a plurality of buckling wire probes (62, 62') extending between said transformer die and said substrate and positioned within aligned holes of said locating dies, said buckling wire probes being of a diameter slightly smaller than said holes so as to slide freely therein, and planar slotted offset guides (86, 90, 94) interposed between given pairs of said locating guides and having slots (88, 92, 96) formed therein of a length in excess of the diameter of said buckling wire probes sc as tc control the lateral buckling of the localized portions of said buckling wire probes between said locating guides with said slots being offset relative to said holes within said locating guides, and wherein said locating guices are spaced from each other at different distances to provide different effective free lengths (EFL 1 , EFL 2 , EFL 3 ) of said buckling wire probes passing therethrough; whereby, said wire probes will buckle laterally in sequence through individual buckling modes from the longest effective free length to the shortest effective free length under increasing applied axial compressive force exerted by the wire probe captured between the transformer die and said substrate, whereby said multiple mode buckling beam probe assembly can effectively increase the axial deflections of said wire probes while allowing greater probing density with the sequence and magnitude of each buckle of the multiple buckling modes being tailored to the specific needs of the probe assembly.