Hughes Aircraft Company

Skw Corporation

Scott B Evans

Frank L Augustine

Kevin L Soch

A focal plane array uses non-contact electrical interconnects instead of indium bumps. The interconnect bump comprises one or more vacuum microelectronics devices. The non-contact interconnect provides no themally conductive path between the detector and readout. For thermal detectors, the detector is not thermally connected to the readout and thus undergoes larger temperature changes in response to infrared radiation. For cryogenically cooled detectors, the detector and readout each have separate heat sinks with separate temperature controls. The readout may thus be operated at a higher temperature than the detector. The non-contact interconnect eliminates heat leakage from the readout to the detector enabling a thermal gradient to be maintained simultaneously with a net savings in refrigerator power. The non-contact interconnect also allows for differences in thermal expansion between the detector and the readout and thus increases the reliability of the focal plane array.

Non-contact interconnect for focal plane arrays

Individual processing cells are provided in close proximity to each detector element in an infrared detector array. Signals generated by the detectors in response to incident infrared radiation are converted to amplified voltages by their respective processing cells, with all of the cells sampling and holding their respective amplified signals simultaneously. The signals held by the various cells are then read out serially during the next cycle of alternating exposures and shadings by a rotating chopper. The amplified signals of all the cells are simultaneously reset at the beginning of each chopper cycle. The simultaneous sampling and holding allows all of the held pixel signals to represent equal periods of exposure or shading, while the local voltage conversion and signal amplification at each processing cell substantially improves the final signal-to-noise ratio.

Infrared detection system and method with distributed signal

A focal plane array having an interconnect bump that has high thermal resistivity, and which may be used to interconnect the detector and readout of the array. The detector and readout each have separate heat sinks with separate temperature controls. The readout may thus be operated at a higher temperature than the detector. A high thermal resistance interconnect bump is employed to limit heat leakage from the readout to the detector to an acceptable level, and to enable a thermal gradient to be maintained simultaneously with a net savings in refrigerator power. The heat sink for the detector is made in such a way as to not obscure the active area of the detector, that is, it is annular in shape so as to surround the active area of the detector. The interconnect bump comprises a thermally insulating pedestal comprising a material such as polyimide, for example, with an over-the-edge metallization employed as an electrical contact. The pedestal employs perforating vias in order to increase the thermal resistance. Disposed on top of the pedestal is an indium bump which mates with a corresponding bump on the detector. A similar interconnect having a polyimide pedestal may also be provided on the detector to provide for even greater thermal resistance. The high thermal resistivity of the interconnect allows the detector and readout to operate at distinct optimal temperatures.

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Carlsbad, CA, United States of America

Scott B Evans