IBM reliability experience with hybrid microcircuits

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MICROELECTRONICS

factor of five better than a comparable aluminum metalized device with respect to humidity. However, all gold metalized devices are not necessarily this good; an example is given. To evaluate bond integrity, a liquid-to-liquid thermal shock is used followed by a high temperature parameter readout. Data is presented from long-term life tests which indicate that reliable plastic devices are not adversely effected after five cycles of thermal shock. Also presented is data indicating acceleration factors for salt atmosphere testing of silicone packages. Finally, problems with procurement of reliable plastic encapsulated semiconductors are discussed from a user's viewpoint.

High-reliability plastic package for integrated circuits. H. KHAJEZADEH. IEEE l lth Annual Proceedings Reliability Physics (1973). p. 236. Two orders of magnitude improvement in the reliability of plastic packages has been achieved as the result of a systematic study of basic failure mechanisms and the development of improved materials, handling procedures and process controls. This improved integratedcircuit packaging system has resulted in plastic-encapsulated product capable of matching the reliability of hermetic packages under severe environmental stress. Fabrication techniques and screening procedures for high reliability transferred electron diodes. T. E. WALSH. IEEE l lth Annual Proceedings Reliability Physics (1973). p. 282. Extensive investigation of the fabrication techniques for GaAs transferred electron diodes for CW and pulsed microwave oscillators have resulted in observed MTBF's 3. C I R C U I T

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RELIABILITY,

*The reliability of independent exponential series systems--A bayesian approach. Technical report. N. R. DRAPER and l GUTMAN. UWIS-DS-72-317. Wisconsin University, Dept. of Statistics (Dec. 1972). 32 pp. Leiberman and Ross have recently given a solution to the problem of finding confidence intervals for the reliability function R(t) of two independent exponential series systems via a sampling theory approach. In the paper the authors examine the problem from the Bayesian point of view. The authors deal with both the uncensored and the censored cases, and illustrate the work with examples. Reliability analysis of a nuclear reactor fuel charging system. J. A. BUZACOTT. IEEE Transactions on Reliability R-22 No. 2, June (1973), p. 88. A fuel charge/discharge system for a nuclear reactor with on-load fuel changing is considered. The system consists of two fuel charging (fc) machines which operate in parallel. When both fc machines have been down for more than 28 days the reactor becomes subcritical and shuts down spontaneously. Using conditional probability arguments and renewal theory it is shown how reliability measures of a two unit redundant system can be extended to obtain the expected frequency and duration of reactor shut-downs due to fc system failures. Operational performance of computing systems. J. PA(. Automatizace 4 (1973), p. 103. (in Czechoslovakian). This

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RELIABILITY

in excess of 100,0(30 h for properly made devices. Screening controls and an operating temperature criterion have been established for ultrareliable radar transmitter diodes functioning in military environments.

Median-time-to-failare (MTF) of microwave power transistors under RF conditions. W. E. POOLE. IEEE llth Annual Proceedings Reliability Physics (1973). p. 287. For the first known time, comprehensive RF life-tests are being run on a microwave power transistor. Previous reliability predictions have been based on DC life-tests. Preliminary data indicates a median life of the order of 106 h (> 100 years) for a stateof-the-art 30 W L-Band device operating under normal RF operation. This exceeds the desired device reliability levels in solid-state phased array radars using this device. Tests are being run under two typical pulsed RF conditions: 120 us and 1500 us pulse width at 1.4 GHz. IBM reliability experience with hybrid microcircuits. P. A. TOTTA. IEEE I lth Annual Proceedings Reliability Physics (1973). p. 92. IBM has built and used hybrid microcircuits for about 10 years. They were introduced as SLT (Solid Logic Technology) with the announcement of System/360 in 1964. The reliability of SLT in the field has been surprisingly good. Mature SLT product has a field failure rate of about 1 to 5 × 10-*% fails/circuit/thousand hours. This is a hundred times better than second generation computer electronics, and ten times better than was expected for a hybrid technology with so many interconnections. MAINTENANCE

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paper describes dependence of computer performance on MTBF, MTTR, delay time, mission time and adjustment factors. Definitions 9f reliabilit)and maintainability parameters are applicated from engineering specifications and reliability standards of US and Soviet computers (inclusive RJAD computers). This paper is presenting data about predicted and operational MTBF of processors Minsk 2/22 computers in years 1964 1970.

Expected value and variance of failure time in redundant systems. E. J. MUTH. IEEE Transactions on Reliability R-22 No. 2, June (1973), p. 103. Formulas are derived for the mean value and the variance of the distribution of time to system failure for parallel redundant and m out of n systems. A novel approach is used in the derivation which requires only elementary calculus and no explicit integration of specific functions. For the general case component failure times are assumed to be statistically independent and exponentially distributed. In addition, a special case of statistical dependence is treated. Contact failures of crossbar switching system. J. WATANABI! and T. KASAHARA. Abstracts The transactions of the Institute of Electronics and Communication Engineers of Japan. 56 No. 6, June (1973), p. 2. The same type of plants for automatic switching systems are manufactured and used