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Recent results from reliability tests on transistors
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A B S T R A C T S ON M I C R O E L E C T R O N I C S
AND RELIABILITY
Recent results from reliability tests on transistors. H. W. HAGMEISTER..\-achr.-Techn. 17, 7 (1964) (German). This paper begins with a description and a discussion of the results of reliability tests on standard type transistors in production for some time. After a brief summary of a system of continuous reliability checks by means of various test methods (some being accelerated tests) the results from reliability tests on n'mdern types of transistors for commercial applications are reported. These types of transistors exhibit a substantialiv improved behaviour with respect to life expectancy and considerably reduced failure rates when compared with standard types. In the final part the data obtained from these tests are compared with the failure rates observed in practical applications. Influence of m e c h a n i c a l d a m a g e on avalanche breadown in silicon pn junctions. A. GOETZBERGERand R. H. Fx.',cr{. Solid State Electron. 7, 543 (1964). Diodes exhibiting uniform avalance effect were mechanically damaged by scratching with a silicon carbide tool. T h e breakdown voltage in the damaged regions was found to be increased in n-p junctions and decreased in p*n junctions. Annealing at temperatures of 600~C and above resulted in gradual restoration of the original diode properties. It is concluded that about 2.5 x 10 :r donors are introduced into the space charge layer by the mechanical damage. Stability estimation of electron tubes' measurable features by m e t h o d of equivalent rate of failures. Sz. FtRKOWlCZ. Archiwum Elektrotechniki, XIII, 411 (1964) (Polish). This paper discussed stability estimation of electron tubes' measurable features based on the principle of ascribing to the observed relative changes of the investigated feature of the imagined failures equivalent rate. This method is called equivalent rate of failures method. The paper contains discussion of the substance of the proposed method and the way of determining the equivalent rate of failures as welt as principles of utilizing the said method in practice in order to draw conclusions on stability of the measurable feature under investigation. Further, experiments are described which have been carried out as a test of practical utility of the proposed method. This method of stability estimation of measurable features can be useful not only in the case of electron tubes but also with respect to other electronic components, e.g. resistors, condensers and transistors. Research toward a physics of ageing of silicon p-n junctions. H. C. GOaTO.X and K. P. Dt:CHA.xtV. IEEE Trans. on Component Parts, March, 28 (1964). An experimental programme has been initiated to develop an approach to reliability prediction based on an understanding of the physical processes responsible for degradation of performance characteristics of electronic component parts. A modification of the Eyring rate equation, accounting for the effects of nonthermal as well as thermal stresses, is used as the mathematical model. The part type used in the experimental programme is the ZJ 281-M silicon controlled avalanche rectifier. Nominally identical devices are subjected to various levels of temperature and electric field (dc reverse bias across the p - n junction) and time rates of change of electrical parameters are determined. As sufficient data becomes available, the constants of the Eyring equation will be determined and its utility as a prediction mechanism will be evaluated. At the same time, an analytical programme is being carried out to relate the observed electrical parameters to causitive physical mechanisms. Thus, the constants of the Eyring equation are given meaning in terms of activation energies and frequency' factors associated with the physical mechanisms responsible for the deterioration or ageing of observable electrical characteristics. F a i l u r e patterns of components. T. R. W. BUSHBY. Proc. IREE Australia, April, 240 (t964). ~[any components have failure-patterns that conform to the Gaussian law. If individual lifetimes be recorded, the test for conformity, and the determination of the mean life and standard deviation is easy. If this be impracticable, as occurs when the data consist of total failures in given time-intervals, mathematical models are necessary for such determination. Conversely, if individual lifetimes be recorded, the deterruination of total failures in given time-intervals is useful for stock-estimating. T h e solution of the models reveals some unsuspected variations in successive time-intervals, which might cause alarm and stock-estimating difficulties, if not foreseen. Such variations may also occur when a reliabilityimprovement project, resulting in an increased lifetime, is initiated. When an improvement by other means is not possible, a mandatory replacement of the faulty component at a determined time can reduce the failure-rate. T h e data are then used to prescribe the'optimum replacement time. An example of the use of this technique is given.
A B S T R A C T S ON M I C R O E L E C T R O N I C S
AND RELIABILITY
Recent results from reliability tests on transistors. H. W. HAGMEISTER..\-achr.-Techn. 17, 7 (1964) (German). This paper begins with a description and a discussion of the results of reliability tests on standard type transistors in production for some time. After a brief summary of a system of continuous reliability checks by means of various test methods (some being accelerated tests) the results from reliability tests on n'mdern types of transistors for commercial applications are reported. These types of transistors exhibit a substantialiv improved behaviour with respect to life expectancy and considerably reduced failure rates when compared with standard types. In the final part the data obtained from these tests are compared with the failure rates observed in practical applications. Influence of m e c h a n i c a l d a m a g e on avalanche breadown in silicon pn junctions. A. GOETZBERGERand R. H. Fx.',cr{. Solid State Electron. 7, 543 (1964). Diodes exhibiting uniform avalance effect were mechanically damaged by scratching with a silicon carbide tool. T h e breakdown voltage in the damaged regions was found to be increased in n-p junctions and decreased in p*n junctions. Annealing at temperatures of 600~C and above resulted in gradual restoration of the original diode properties. It is concluded that about 2.5 x 10 :r donors are introduced into the space charge layer by the mechanical damage. Stability estimation of electron tubes' measurable features by m e t h o d of equivalent rate of failures. Sz. FtRKOWlCZ. Archiwum Elektrotechniki, XIII, 411 (1964) (Polish). This paper discussed stability estimation of electron tubes' measurable features based on the principle of ascribing to the observed relative changes of the investigated feature of the imagined failures equivalent rate. This method is called equivalent rate of failures method. The paper contains discussion of the substance of the proposed method and the way of determining the equivalent rate of failures as welt as principles of utilizing the said method in practice in order to draw conclusions on stability of the measurable feature under investigation. Further, experiments are described which have been carried out as a test of practical utility of the proposed method. This method of stability estimation of measurable features can be useful not only in the case of electron tubes but also with respect to other electronic components, e.g. resistors, condensers and transistors. Research toward a physics of ageing of silicon p-n junctions. H. C. GOaTO.X and K. P. Dt:CHA.xtV. IEEE Trans. on Component Parts, March, 28 (1964). An experimental programme has been initiated to develop an approach to reliability prediction based on an understanding of the physical processes responsible for degradation of performance characteristics of electronic component parts. A modification of the Eyring rate equation, accounting for the effects of nonthermal as well as thermal stresses, is used as the mathematical model. The part type used in the experimental programme is the ZJ 281-M silicon controlled avalanche rectifier. Nominally identical devices are subjected to various levels of temperature and electric field (dc reverse bias across the p - n junction) and time rates of change of electrical parameters are determined. As sufficient data becomes available, the constants of the Eyring equation will be determined and its utility as a prediction mechanism will be evaluated. At the same time, an analytical programme is being carried out to relate the observed electrical parameters to causitive physical mechanisms. Thus, the constants of the Eyring equation are given meaning in terms of activation energies and frequency' factors associated with the physical mechanisms responsible for the deterioration or ageing of observable electrical characteristics. F a i l u r e patterns of components. T. R. W. BUSHBY. Proc. IREE Australia, April, 240 (t964). ~[any components have failure-patterns that conform to the Gaussian law. If individual lifetimes be recorded, the test for conformity, and the determination of the mean life and standard deviation is easy. If this be impracticable, as occurs when the data consist of total failures in given time-intervals, mathematical models are necessary for such determination. Conversely, if individual lifetimes be recorded, the deterruination of total failures in given time-intervals is useful for stock-estimating. T h e solution of the models reveals some unsuspected variations in successive time-intervals, which might cause alarm and stock-estimating difficulties, if not foreseen. Such variations may also occur when a reliabilityimprovement project, resulting in an increased lifetime, is initiated. When an improvement by other means is not possible, a mandatory replacement of the faulty component at a determined time can reduce the failure-rate. T h e data are then used to prescribe the'optimum replacement time. An example of the use of this technique is given.