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Aviation History
1960
1960 - 2246.PDF
582 FLIGHT, 7 October 1960 resistors, unfortunately, have a rather high positive temperaturecoefficient; other forms of resistors, produced from diffused layers, have a lower temperature coefficient. A capacitor can be formed from a back-biased diode often usedin variable capacitor tuning devices, whilst R-C distributive net- works can be formed by placing resistive silicon oxide over thefixed capacitor elements. Some of these possible components are shown in Fig 5, but a great deal of work remains to be done yetin evaluating the ultimate possibilities of these devices. It is interesting that in the main they follow the normaKtransistorprocessing techniques (i.e., selective etching, diffusion of impurities, thermo-compression bonding, etc.) common in the tran-sistor factory. One of the most useful illustrations of this type of construction was shown by Texas Instruments some time ago andis reproduced in Fig 6, in which the various components have been marked. It is obvious that these techniques will affect airborne equip-ment in due course, and the experimental work which is being done at the present time will undoubtedly lead to microminiatureassemblies capable of being used in aircraft communications and, to a certain extent, radar systems. It must be borne in mind,however, that these techniques are at the moment applicable only to transistorized electronic equipment and that magnetrons, modu-lators, aerials and heavy power supplies cannot be dealt with by these systems. Even then the volume of airborne transistorizedcomputer and communications equipment which lends itself to these techniques is increasing and within a few years some micro-miniaturized units should appear in aircraft. It will be interesting to see whether the predicted increase in reliability will be borne CONTAINER CONNECTION BOARD PRINTED WIRING OR TERMINAL STRIPS CONNECTION BOARD TERMINALS OUTPUT CONNECTIONS MAIN TERMINALS CONNECTION 8OHR0 TERMINALS WAFER No 2 UNDERSIDE SHOWING CONNECTIONS ENLARGED VIEW SHOWING U-UNK WRAPPED JOINT AVIATION ELECTRONICS . . . Top, Fig 4. Experimental microminia- ture assembly Right, Fig 5. Solid circuit component elements Below right, Fig 6. Solid circuit in silicon, courtesy Texas Instruments RESISTOR. FIXED Nil P CAPACITOR. FIXED THEnrmit rnooucto J s.o, N OK P DISTRIBUTED R.C NETWORK NESA TRANSISTOR RESISTOR. VARIABLE CAPACITOR FIXED (STUDY .US) OR VARIABLE (VADUBLE BUS) TRANSFORMER DIODE out in practice. From a theoretical point of view there is everyreason to hope for a gain in reliability of the order of at least ten to one, but a great deal of development is necessary before sucha prediction can be fulfilled. Communications receivers have now been built on the micro-module system in the USA, and the AN/PRC/36 receiver con- tains some ten modules of the size shown in Fig 2, resulting in apacking density of approximately a quarter of a million parts per cubic foot (approx 140/cu in). Circuits fabricated from single crystal germanium or siliconhave now been developed in the USA for most of the normal receiver functions, but have not yet been shown as completereceivers. The size, however, may be as small as 1 or 2 cu in, and the weight infinitesimal compared with normal receivers. Micro-miniaturization techniques lend themselves to digital computers, and this will open up a field in airborne communications which ina few years' time will enable multi-channel receivers, navigating devices and all kinds of new applications to be developed. The possibilities in the solid-state microminiature devices areenormous, and in the next few years one may expect to see con- siderable size and weight reductions being introduced into airborneequipment, although it will be many years before large-scale introduction of these devices takes place. 390 A RESISTOR RESI5TOC RESISTOR SIZE
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