In U.S. Pat. No. 3,560,907 there is disclosed an electrical circuit connection apparatus for effecting connections of microminiature electrical and electronic circuits without disturbing the circuits physical connective aspects. This apparatus has an insulative fired ceramic substrate having an opening passing completely therethrough and a plurality of slots extending from one surface a limited extent into the substrate; a corresponding plurality of sheet-like contacts of metallic spring material received edgewise within the slots and having edge portions extending into the substrate opening and outwardly thereof beyond an outer substrate surface. The exposed circuit plane is located at the substrate opening such that the contact edge portions within the opening are resiliently urged substantially normally against respective portions of the circuit completing connection with collateral circuit apparatus.
This device poses several problems. One is that the ceramic substrate is fragile and difficult to form. The ceramic must be cut ultrasonically and the location of the slots is critical because their location determines the reach of the sheet-like contacts. The ceramic initially is so soft and chalky that it must be impregnated with a material such as epoxy resin. The resin has to be centrifuged out of the slots prior to the curing of the epoxy resin, or otherwise the slots will be shortened in depth thereby undesirably altering the reach of the contacts, or narrowing the slots preventing insertion of the contacts. If the ceramic is impregnated prior to the cutting of the slots, the material cannot be cut ultrasonically. If the material is fully fired prior to cutting the slots, the material is too hard to cut mechanically. Another problem is that the curing temperature of the epoxy resin impregnant causes some distortion or shrinkage of the ceramic, which must be compensated for at the time the slots are cut. However, it is not possible to make any precise compensation, so there always exists at least some mislocation to the slots or inaccuracy in their depth, with resulting errors errors in the reach of the contacts.
Yet another difficulty is due to the weakness of the ceramic at the time of the cutting of the slots. Consequently, there must exist some space between adjacent contacts, otherwise the intervening ceramic will break out. The inability to provide closely spaced adjacent slots prevents or interferes with the making of high density measurements on a chip, that is, the probing of great numbers of closely spaced-apart pads per chip.
The present invention substantially overcomes these problems, and it is believed that it constitutes a major advance in the art. Particularly, this invention permits a greater density of contacts or probes which allows for greater utility in the making of electrical measurements on chips and other electronic circuits.