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Reliability of systems with standby components
WORLD
ABSTRACTS
ON MICROELECTRONICS
Application of scanning electron microscopy to integrated circuit failure. J. R. DEVANEY, Solid St. Technol., March (1970), p. 73. The application of scanning electron microscopy to routine integrated circuit failure analysis is discussed. Investigations concerning ball bond contamination and open metalization
AND RELIABILITY
at contact windows are outlined. The results indicate that insufficient cleaning of the bonding wire after drawing is the source of chlorine residues on the bond. The open metalization problem has been resolved by a change in the oxide profile by the integrated circuit manufacturer.
3. C I R C U I T A N D S Y S T E M S R E L I A B I L I T Y , M A I N T E N A N C E
Reliability and the importance of maintenance. R. THOMASON, Electron. Radio Tech. 4, No. 2 (1970), p. 51. It is concluded that system effectiveness can be obtained by "trading-off" inherent reliability against maintainability if repair is possible. Reliability is, in effect, a special case of availability in which maintenance is not carried out, and, as a result it is possible to decide how much emphasis should be placed on maintenance by considering the operational circumstances. Where operating time is short and repair either impossible or costly, the emphasis is on reliability. On the other hand, for systems in long-term or continuous operation, the emphasis will be on maintainability. It follows from what has been said, that maintenance of equipments constructed to an availability requirement, must be maintained completely in accordance with the code of practice outlined by the designer, and using materials and tools approved for the purpose.
Reliability in action. Z. S. SIEMASZKO.Electron. Purr, June (1970), p. 223. It is highly desirable for reliability to be a "built-in" feature of electronic equipment. This article describes a 10-year development of three generations of radio equipment and raises some general aspects of reliability. The state variable approach to system effectivehess. N. I. HEENAN, I E E E Tram Reliab. R-19, No. 1, February (1970), p. 24. Expressions are given in the literature for the availability, mean-time-betweenfailures, mean uptime, and mean downtime for systems consisting of a number of identical modules in redundancy. Using the concept of superstates, vector expressions for these parameters are presented which apply to a system consisting of an arbitrary intereonnection of different types of modules. A vector expression for system effectiveness is presented which is formally the same as the expression for availability in the case of a single-funct,on system and which can be extended easily to cover multifunction systems.
Reliability analysis of redundant networks using flow g r a p h s . K. B. MISRA and T. S. M. R i o , I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 19. A flow graph approach for reliability analysis is applied to redundancy with elements in the simple series-parallel networks and to the more general case with elements in non-series-parallel combinations. The reliability of networks for elements with open or short failures is analyzed with flow graphs. Typical examples are shown.
17
AND REDUNDANCY
An approach to the m i n i m i z a t i o n of mlsclassiflcation in the repair of equipment. A. J. GRoss, I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 10. A problem which can be quite costly to an agency involved with repairable equipment on a large scale is the misclassification which can arise when repair work is initiated. Often a piece of equipment finds its way to the repair shop even though it has not experienced a failure. On the other hand, a failed component may not be repaired properly because the cause of failure is not properly diagnosed; thus a delay will occur in returning the component to service. A mathematical model is developed which accounts for the two misclassification possibilities and a procedure is given which minimizes the misclassification probabilities, contingent on a fixed amount of available capital for this purpose. The model is of the Markov type with the simplifying assumption of constant transition rates (over time) among the various states.
Reliability of systems with standby components. J. B. JONES, I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 35. A method is introduced for approximating the reliability of a large complex system with standby components. It is done by substituting an approximate simple model for the more complex system. Each part of the model has a simple formula for its reliability. A n approach to field repair of avionics computers. R. A. GRUENINGER, Proc. 1970 Ann. Symp. Reliab., Los Angeles, IEEE Cat. No. 70 C 2-R, 3-5 February (1970), p. 292. Avionics computer programs frequently include, as a contractual requirement, the development of techniques for repair of system subassemblies. This paper describes a repair technique developed to permit the removal and replacement of flat packs and discrete components on multilayer interconnection boards in the field. Generally, maintainability and field repair specifications require simplified techniques. In keeping with this philosophy, the repair technique described was developed for application within the following customer specified field shop restraints: Special facilities such as clean rooms shall not be required. Use of complex repair tools shall be minimized. Tools required shall be simple to operate and repair. Curing ovens shall not be required. Additional limitative conditions were established: (1) No solvents would be used in removal of solder fluxes during repair. If proven acceptable, dry fluxes would not be removed from the repaired page. (2) A minimum time to repair (MTTR) would be established to include an average of 15 rain accelerated cure of the conformal coating material.
ABSTRACTS
ON MICROELECTRONICS
Application of scanning electron microscopy to integrated circuit failure. J. R. DEVANEY, Solid St. Technol., March (1970), p. 73. The application of scanning electron microscopy to routine integrated circuit failure analysis is discussed. Investigations concerning ball bond contamination and open metalization
AND RELIABILITY
at contact windows are outlined. The results indicate that insufficient cleaning of the bonding wire after drawing is the source of chlorine residues on the bond. The open metalization problem has been resolved by a change in the oxide profile by the integrated circuit manufacturer.
3. C I R C U I T A N D S Y S T E M S R E L I A B I L I T Y , M A I N T E N A N C E
Reliability and the importance of maintenance. R. THOMASON, Electron. Radio Tech. 4, No. 2 (1970), p. 51. It is concluded that system effectiveness can be obtained by "trading-off" inherent reliability against maintainability if repair is possible. Reliability is, in effect, a special case of availability in which maintenance is not carried out, and, as a result it is possible to decide how much emphasis should be placed on maintenance by considering the operational circumstances. Where operating time is short and repair either impossible or costly, the emphasis is on reliability. On the other hand, for systems in long-term or continuous operation, the emphasis will be on maintainability. It follows from what has been said, that maintenance of equipments constructed to an availability requirement, must be maintained completely in accordance with the code of practice outlined by the designer, and using materials and tools approved for the purpose.
Reliability in action. Z. S. SIEMASZKO.Electron. Purr, June (1970), p. 223. It is highly desirable for reliability to be a "built-in" feature of electronic equipment. This article describes a 10-year development of three generations of radio equipment and raises some general aspects of reliability. The state variable approach to system effectivehess. N. I. HEENAN, I E E E Tram Reliab. R-19, No. 1, February (1970), p. 24. Expressions are given in the literature for the availability, mean-time-betweenfailures, mean uptime, and mean downtime for systems consisting of a number of identical modules in redundancy. Using the concept of superstates, vector expressions for these parameters are presented which apply to a system consisting of an arbitrary intereonnection of different types of modules. A vector expression for system effectiveness is presented which is formally the same as the expression for availability in the case of a single-funct,on system and which can be extended easily to cover multifunction systems.
Reliability analysis of redundant networks using flow g r a p h s . K. B. MISRA and T. S. M. R i o , I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 19. A flow graph approach for reliability analysis is applied to redundancy with elements in the simple series-parallel networks and to the more general case with elements in non-series-parallel combinations. The reliability of networks for elements with open or short failures is analyzed with flow graphs. Typical examples are shown.
17
AND REDUNDANCY
An approach to the m i n i m i z a t i o n of mlsclassiflcation in the repair of equipment. A. J. GRoss, I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 10. A problem which can be quite costly to an agency involved with repairable equipment on a large scale is the misclassification which can arise when repair work is initiated. Often a piece of equipment finds its way to the repair shop even though it has not experienced a failure. On the other hand, a failed component may not be repaired properly because the cause of failure is not properly diagnosed; thus a delay will occur in returning the component to service. A mathematical model is developed which accounts for the two misclassification possibilities and a procedure is given which minimizes the misclassification probabilities, contingent on a fixed amount of available capital for this purpose. The model is of the Markov type with the simplifying assumption of constant transition rates (over time) among the various states.
Reliability of systems with standby components. J. B. JONES, I E E E Trans. Reliab. R-19, No. 1, February (1970), p. 35. A method is introduced for approximating the reliability of a large complex system with standby components. It is done by substituting an approximate simple model for the more complex system. Each part of the model has a simple formula for its reliability. A n approach to field repair of avionics computers. R. A. GRUENINGER, Proc. 1970 Ann. Symp. Reliab., Los Angeles, IEEE Cat. No. 70 C 2-R, 3-5 February (1970), p. 292. Avionics computer programs frequently include, as a contractual requirement, the development of techniques for repair of system subassemblies. This paper describes a repair technique developed to permit the removal and replacement of flat packs and discrete components on multilayer interconnection boards in the field. Generally, maintainability and field repair specifications require simplified techniques. In keeping with this philosophy, the repair technique described was developed for application within the following customer specified field shop restraints: Special facilities such as clean rooms shall not be required. Use of complex repair tools shall be minimized. Tools required shall be simple to operate and repair. Curing ovens shall not be required. Additional limitative conditions were established: (1) No solvents would be used in removal of solder fluxes during repair. If proven acceptable, dry fluxes would not be removed from the repaired page. (2) A minimum time to repair (MTTR) would be established to include an average of 15 rain accelerated cure of the conformal coating material.