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Failure analysts curb device faults
ABSTRACTS ON ELECTRONICS RELIABILITY AND MICROMINIATURIZATION
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Statistical circuit analysis based on part test data. F. A. APPLEGATE, Electro-Technol., May 1963, p. 140. The reliability of a circuit is no better than that of its component parts. An accurate and efficient part testing programme is described and its results are then applied to the statistical analysis of the worst-case circuit design in which the parts are to be used. Fail-safe transistor logic. D. H. TAYLOR, Brit. Commun. Electron., Nov. 1962. Failure to safety is an obvious requirement in applications such as railway signalling, aircraft operation, and in most instances where human life may be at stake. This article describes circuits based upon transistors which were devised in relation to nuclear reactor working. Failure analysts curb device faults. N. A. VELEZ and C. L. VOGT,Jr., Electronics, 35, 68 (1962). Gives examples of failure modes in several types of component, e.g.: Diodes. (a) Aluminium button between spring and crystal dislodged and loose in the envelope. (b) Excessive solder built up under the crystal and the crystal was cracked. (c) A crack existed between the whisker and the crystal Capacitors. (a) Ceramic capacitors showed cracks between the plates. (b) Extraneous solder inside a ceramic capacitor caused shorts. Transistors. (a) The base lead was melted open and a diode in series with the base was shorted by excessive current. Both were caused by bad circuit testing. (b) Excessive storage time. A diode in the circuit had misaligned whiskers and was presumed to be a poor risk. Expressing capacitor reliability accurately. D. E. ]VIAGUIRE,Electron. Ind., 21, 100 (1962). The assumption of an exponential distribution may lead to serious errors and the use of Weibull paper is shown. In some cases the components will have a mixed behaviour and separate Weibull parameters are necessary for the different periods. Two examples are given in which the data are tabulated and then plotted on Weibull paper. H o w to evaluate resistor performance. L. S. KING, Electron. Engng., 10, 40 (1962). Factors which cause a resistor to deviate from the nominal value--initial tolerance, temperature coefficient variations, load-life performance deviations and environmental exposures--are discussed briefly. Excessive current noise can be an indication of poor reliability. The solutions to the reliability dilemma lie between lotacceptance and process-control philosophies. Some checking must be done to ensure that the process has been kept under control and that failure mechanisms are understood.
Component failures predicted by infra-red. P. J. KLASS, Aviat. Week ~ Space TechnoL, 77, 85 (1962). Reports on a new technique for detecting potential component failures in electronic equipment by measuring their infra-red radiation intensity. The operating temperature of a component is a major factor affecting its reliability and longevity. Infra-red provides a means of measuring component temperatures while the circuit is operating, without the inconvenience of attaching thermocouples or the risk of changing component temperatures by the measurement process. Some evidence has been obtained to indicate that abnormal rates of temperature rise after the application of power may be important clues in the prediction of component longevity. Extensive controlled tests are now planned to check on this and other points in connection with the technique. CIRCUIT RELIABILITY Improved reliability in wideband feedback transistor amplifiers. E. DAVIES, Marconi Rev., 25, 4 (1962). Describes an improved wideband transistor amplifier based on the philosophy that maximum reliability is obtained when a given specification is met by a circuit incorporating the minimum number of components, provided the configuration assures that performance is not affected by component variations due to aging. General usage assemblies for Navy electronic equipments. T. E. ]V[cDuFFIE and G. C. NEUSCHAEFER, Proc. 8th Nat. Symp., Reliability and Quality Control, Washington, D.C., Jan. 1962, p. 388. Describes the U.S. Navy's programme for standard usage circuits. From an analysis of about 100 Navy electronic equipments, 24 circuits were found which were recommended for standardization. Of these, 21 were actually built and tested.
255
Statistical circuit analysis based on part test data. F. A. APPLEGATE, Electro-Technol., May 1963, p. 140. The reliability of a circuit is no better than that of its component parts. An accurate and efficient part testing programme is described and its results are then applied to the statistical analysis of the worst-case circuit design in which the parts are to be used. Fail-safe transistor logic. D. H. TAYLOR, Brit. Commun. Electron., Nov. 1962. Failure to safety is an obvious requirement in applications such as railway signalling, aircraft operation, and in most instances where human life may be at stake. This article describes circuits based upon transistors which were devised in relation to nuclear reactor working. Failure analysts curb device faults. N. A. VELEZ and C. L. VOGT,Jr., Electronics, 35, 68 (1962). Gives examples of failure modes in several types of component, e.g.: Diodes. (a) Aluminium button between spring and crystal dislodged and loose in the envelope. (b) Excessive solder built up under the crystal and the crystal was cracked. (c) A crack existed between the whisker and the crystal Capacitors. (a) Ceramic capacitors showed cracks between the plates. (b) Extraneous solder inside a ceramic capacitor caused shorts. Transistors. (a) The base lead was melted open and a diode in series with the base was shorted by excessive current. Both were caused by bad circuit testing. (b) Excessive storage time. A diode in the circuit had misaligned whiskers and was presumed to be a poor risk. Expressing capacitor reliability accurately. D. E. ]VIAGUIRE,Electron. Ind., 21, 100 (1962). The assumption of an exponential distribution may lead to serious errors and the use of Weibull paper is shown. In some cases the components will have a mixed behaviour and separate Weibull parameters are necessary for the different periods. Two examples are given in which the data are tabulated and then plotted on Weibull paper. H o w to evaluate resistor performance. L. S. KING, Electron. Engng., 10, 40 (1962). Factors which cause a resistor to deviate from the nominal value--initial tolerance, temperature coefficient variations, load-life performance deviations and environmental exposures--are discussed briefly. Excessive current noise can be an indication of poor reliability. The solutions to the reliability dilemma lie between lotacceptance and process-control philosophies. Some checking must be done to ensure that the process has been kept under control and that failure mechanisms are understood.
Component failures predicted by infra-red. P. J. KLASS, Aviat. Week ~ Space TechnoL, 77, 85 (1962). Reports on a new technique for detecting potential component failures in electronic equipment by measuring their infra-red radiation intensity. The operating temperature of a component is a major factor affecting its reliability and longevity. Infra-red provides a means of measuring component temperatures while the circuit is operating, without the inconvenience of attaching thermocouples or the risk of changing component temperatures by the measurement process. Some evidence has been obtained to indicate that abnormal rates of temperature rise after the application of power may be important clues in the prediction of component longevity. Extensive controlled tests are now planned to check on this and other points in connection with the technique. CIRCUIT RELIABILITY Improved reliability in wideband feedback transistor amplifiers. E. DAVIES, Marconi Rev., 25, 4 (1962). Describes an improved wideband transistor amplifier based on the philosophy that maximum reliability is obtained when a given specification is met by a circuit incorporating the minimum number of components, provided the configuration assures that performance is not affected by component variations due to aging. General usage assemblies for Navy electronic equipments. T. E. ]V[cDuFFIE and G. C. NEUSCHAEFER, Proc. 8th Nat. Symp., Reliability and Quality Control, Washington, D.C., Jan. 1962, p. 388. Describes the U.S. Navy's programme for standard usage circuits. From an analysis of about 100 Navy electronic equipments, 24 circuits were found which were recommended for standardization. Of these, 21 were actually built and tested.