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Harris Corporation has undertaken a multichip module (MCM) project that will develop a four-channel digital RF receiver as a very dense, lightweight system. A single-channel system has been implemented with its supporting logic chips in a 6"*7" PCB (printed circuit board). The four-channel module was fabricated on a 2.5"*2.5" substrate that will be assembled in a 2.75"*2.75" metal package with 200 leads. The module contains a total of 41 chips, twelve being VLSI. To test currently available substrate technologies, the substrate was fabricated in two different varieties: a low-temperature cofired ceramic, the DuPont Green Tape, and a high-density copper/polyimide. Bonding to the top level of the system was done by both TAB (tape automated bonding) and gold wire bonding. An important feature of this MCM is that it exploits design-for-testability concepts which allow defective die or interconnects to be easily identified, thus facilitating module rework. This approach does not require boundary scan to be incorporated into chip design, or test registers to be added to the module. >

Transport measurements have been performed on the conducting state of a memory-type chalcogenide glass, of composition Te81Ge15As4. DC resistivity was measured from 4°K to 300°K and indicates no carrier freeze-out occurs down to 4°K. The resistance ratio, ϱ(300°K)/ϱ(4°K), was found to be 2.5. AC conductivity measurements at room temperature showed only an 18% increase in σ(ω) up to 150 khz. Hall effect experiments at 100 Hz show no dependence of carrier concentration on temperature from 77°K to 300°K, and indicate a room temperature mobility of 85 cm2/V-sec. The sign of the Hall constant implies that the carriers are holes. Resistance was measured as a function of magnetic field from 0 to 140 kOe, at 1.6°K. The magnetoresistance was positive and proportional to H2 at low fields, with saturation beginning to set in above about 80 kOe. The results of these studies, taken in conjunction with the X-ray and NMR data, can be used to suggest a plausible model for memory behavior in chalcogenide glasses.