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Some problems of statistical estimation of reliability
Microelectronie* and Reliability
Pergamon Press 1965. Vol. 4, pp. 221-233.
Printed in Great Britain
ABSTRACTS ON MICROELECTRONICS AND RELIABILITY
RELIABILITY--GENERAL S o m e p r o b l e m s o f statistical estimation of reliability. Sz. FIRKOWICZ.Archiwum Elektrotechniki, XIII, 159 (1964) (Polish). This paper begins with definitions of basic notions related to reliability theory and contains discussions on principles of parametric and nonparametric reliability estimation. Parametric test based on exponential law of reliability has been discussed in detail. There are presented principles of statistically deducting the hazard x value and course of the reliability function R(t) and validity of assumption x = const in a given time interval. Further, two nonparametric tests of reliability estimation are discussed: first test based on the Clopper-Gorwood identity and second one based on a generalized form of exponential law of reliability. Efficiency of both nonparametric tests has been compared.
Equipment and methods for simulating ambient conditions. F. MARTIN. Nachr.-Techn, 17, 171 (1965) (German). The ambient conditions to which electronic components and equipment may be exposed must be taken into consideration during development, design and production. Simulation of such conditions requires laboratories which are equipped with expensive climatic and mechanical test equipment. The present test specifications are far from being uniform and permit no mutual comparison. The future development will lead to combination tests and include conditions hitherto rarely applied. The aim must be a standardization of the various specifications ensuring that the required operational reliability is guaranteed to a higher degree than was possible so far. Case studies of the decreasing failure rate phenomena in mixed populations. F. R. VAN WAG.XER. IEEE Trans. Comp. Parts, CP-11, 258 (1964). After a discussion on the decreasing failure rates found in many components and the relationship of this to Weibull distribution plots, a number of conclusions are given. These are, that although the case for decreasing failure rate is strong, it is not nearly as solid as many workers assume, because of the possibility of undetected mixtures of device population. Many errors which may occur due to the incorrect use of Weibull distributions are discussed in some detail and a summary of some of the mathematical work which has been done in this field is given. Computer screening technique for h i g h e r reliability. L. V. INGLE. IEEE Trans. CP-11, 2, 251 (1964). A computer programme has been developed that can be applied to screening potential failures from any group of components using an outlier technique. The programme features flexibility in that the user can request any frequency cell size for the 16 three-digit parameter positions available. It is equally possible to attempt screening from either high or low values for each parameter. A general cost model is presented which utilizes the computer output in determining the optimum economic screening level. RELIABILITY OF COlVIPONENTS, TUBES AND TRANSISTORS Experience relating to the operational reliability of diodes and transistors. W. ENGBERT and C. JE.XTSCH. Nachr.-Techn. 17, 135 (1964) (German). This paper reports on failures which occur with some types of diodes and transistors and which have been found in practical use of these components in a large computer and in a digital data processing system. A method is discussed which is used for evaluating such results for the purpose of obtaining reliability data with a certain accuracy, and which applies the results of these failure records. 221
Pergamon Press 1965. Vol. 4, pp. 221-233.
Printed in Great Britain
ABSTRACTS ON MICROELECTRONICS AND RELIABILITY
RELIABILITY--GENERAL S o m e p r o b l e m s o f statistical estimation of reliability. Sz. FIRKOWICZ.Archiwum Elektrotechniki, XIII, 159 (1964) (Polish). This paper begins with definitions of basic notions related to reliability theory and contains discussions on principles of parametric and nonparametric reliability estimation. Parametric test based on exponential law of reliability has been discussed in detail. There are presented principles of statistically deducting the hazard x value and course of the reliability function R(t) and validity of assumption x = const in a given time interval. Further, two nonparametric tests of reliability estimation are discussed: first test based on the Clopper-Gorwood identity and second one based on a generalized form of exponential law of reliability. Efficiency of both nonparametric tests has been compared.
Equipment and methods for simulating ambient conditions. F. MARTIN. Nachr.-Techn, 17, 171 (1965) (German). The ambient conditions to which electronic components and equipment may be exposed must be taken into consideration during development, design and production. Simulation of such conditions requires laboratories which are equipped with expensive climatic and mechanical test equipment. The present test specifications are far from being uniform and permit no mutual comparison. The future development will lead to combination tests and include conditions hitherto rarely applied. The aim must be a standardization of the various specifications ensuring that the required operational reliability is guaranteed to a higher degree than was possible so far. Case studies of the decreasing failure rate phenomena in mixed populations. F. R. VAN WAG.XER. IEEE Trans. Comp. Parts, CP-11, 258 (1964). After a discussion on the decreasing failure rates found in many components and the relationship of this to Weibull distribution plots, a number of conclusions are given. These are, that although the case for decreasing failure rate is strong, it is not nearly as solid as many workers assume, because of the possibility of undetected mixtures of device population. Many errors which may occur due to the incorrect use of Weibull distributions are discussed in some detail and a summary of some of the mathematical work which has been done in this field is given. Computer screening technique for h i g h e r reliability. L. V. INGLE. IEEE Trans. CP-11, 2, 251 (1964). A computer programme has been developed that can be applied to screening potential failures from any group of components using an outlier technique. The programme features flexibility in that the user can request any frequency cell size for the 16 three-digit parameter positions available. It is equally possible to attempt screening from either high or low values for each parameter. A general cost model is presented which utilizes the computer output in determining the optimum economic screening level. RELIABILITY OF COlVIPONENTS, TUBES AND TRANSISTORS Experience relating to the operational reliability of diodes and transistors. W. ENGBERT and C. JE.XTSCH. Nachr.-Techn. 17, 135 (1964) (German). This paper reports on failures which occur with some types of diodes and transistors and which have been found in practical use of these components in a large computer and in a digital data processing system. A method is discussed which is used for evaluating such results for the purpose of obtaining reliability data with a certain accuracy, and which applies the results of these failure records. 221