Flip chip assembly - A new thin film approach to single-crystal logic operators

The authors consider inverting or "flipping" the circuit chip on to an evaporated thin film insulating substrate. Bonding the "flip-chip" to matching terminal pads of evaporated aluminum runs on the substrate permits elimination of the weakest part of present planar passivated semjconductor; namely, the bonded lead from the device or circuit to the terminals of the enclosure. Further, this approach offers a solution to present yield problems of the previous method. A test vehicle chosen for "flip-chips" was a four stage counter. This is a parallel-carry design involving 24 circuit chips. A hermetic seal package approximately 1.2 inches square, containing a one-inch square substrate is used for interconnection of the circuit chips. Data shows that heat can be transferred efficiently with the flip-chip bonding method. Using the construction method outlined, temperature rises of less than 13°F have been calculated with more efficient transfer possible, if necessary. Complete development of the technique described offers unique characteristics which cannot be obtained in present microelectronic assemblies.