Integrated circuits (IC) are typically enclosed in ceramic packages with metallic feed-throughs. Such devices, however, are susceptible to high-power microwave electromagnetic interference (HPM-EMI) since the microwaves readily penetrate the ceramic package and are picked up by package leads and interconnects when such lead lengths are of the same order of magnitude as the microwave wavelength. Thus, the interference of micro-circuits with HPM-EMI is a critical problem that confronts many designers of military equipment and other strategic systems.
For example, those concerned with the development of digital fly-by-wire systems have long recognized the need for isolating such systems from HPM-EMI. In such systems, the ceramic packages of conventional IC devices have been replaced by metallic packages to provide Faraday shielding, thereby directly eliminating absorbed HPM-EMI.
Electro-optic circuits including optical fiber have also been used to eliminate indirectly absorbed HPM-EMI picked up and transmitted along conventional metallic feed-throughs. However, such electro-optic isolators have limited power handling capabilities, thus precluding their use in isolating the power supply feedthroughs.
Further, spiral inductors formed on the IC chips near the power input pad have been used to partially isolate the digital portion of IC devices from HPM-EMI traveling along the power supply lines. This technique is relatively simple and may provide some isolation at long microwave wavelengths. Unfortunately, since the metallic feed-through is not eliminated, microwave isolation at short wavelengths will not be possible using this technique. This is because, at short wavelengths, HPM-EMI on the power supply lines will be re-radiated inside the package by the chip-to-package interconnect wires. Therefore, those skilled in the art of packaging military hardware would readily appreciate a microcircuit package which provides a high power feed through while still being resistant to HPM-EMI. The present invention addresses such a microcircuit package.