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The problems of reliability growth and demonstrations with military electronics
World Abstracts on Microelectronics and Reliability
Peak temperature during turnover and the volumetric degradation of switching transistors and ICs. A. P. I ~ I v ~ . Microelectron. & Reliab. 13, 103 (1974). Temperature increase as a consequence of switch-over power transients can be blamed as the cause of some typically volumetric failures, e.g. C-E punch-through and C-B breakdown, in high-level switching operation. Calculating the depth of thermal penetration on both collector junction sides and considering the thermal capacity of this heated-up volume section as well as the thermal resistance for the same, both as a function of time, one gets a fair model for junction temperature rise estimations, i.e. in the knowledge of switchover power vs time function and constructional data of a transistor one can calculate the junction temperature vs time function. Considering several typical transistors of various technologies ranging from the minute transistor on a monolithic IC chip to bulky alloyed Ge or mesa SI power types and assuming a fair structure and even current distribution, it is proved that the arising peak turnover temperature jumps are completely harmless since they are ranging from some hundredth °C (IC transistor) to some °C (power type) at full rated switching power levels. A badly uneven structure, however, leads to thermal runaway and the occurrence of hot spots in the bulk and so to total deterioration (short) since temperature rise is inversely proportional to the junction area involved in actual current conduction, i.e. to the ratio of effective to nominal junction area, especially at power transistors where specific turnover energy density is high. Thus, brief operational screen tests where collector current limiting ratings are transgressed and switching times artificaily elongated, seems to be a good method for sorting out specimens of inherently poor structure which are prone to volumetric degradation. On the contrary, switching power levels of bipolar IC transistors are so low that the whole bulk-degradation effect can be neglected and so a costly switching-operation life test seems as unreasonable as superfluous at ICs, at least as compared to effective but cheap d.c. operational methods.
Radiation-stimulated failure mechanism in a dielectrically isolated integrated circuit. J. L. AZAREWtCZ and T. F. 3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability analysis of regular distributed chain structures. R. J. MORGAN and W. H. HOLMES. IEEE Trans. Reliab. R-23, 1, 11 (April 1974). This paper considers the reliability analysis of chain structures of identical sections. The sections are distributed in the sense that there is more than one input and output node to each section. System failure occurs if no path exists between system input and output. (System branch failures are by open circuit only.) This model is particularly applicable to redundant communication systems. It is shown that the distributed chain structure is asymptotically equivalent to a series structure of identical equivalent sections, assuming that the number of sections is large and that the branch reliabilities are equal. The reliability of the equivalent section is obtained as the subdominant eigenvalue of a transition matrix. The error in this representation is negligible for system branch reliabilities large.
The problems of reliability growth and demonstrations with military electronics. J. E. GREEN. Microelectron. & Reliab. 12, 513 (1972). The last decade has seen major changes in
21
WROBEL. Proc. IEEE 24th Electronic Components Conference, Washington D.C. 48 (13-15 May 1975). An apparent latchup condition has been observed in a dielectrically isolated integrated circuit. This circuit has been analyzed with non-destructive tests using Linae and laboratory measurements, and the failure mechanism has been identified. The device package was then opened, and the failure path was verified visually. Upon removal of a metalization short, which was the cause of the failure, the device returned to normal operation.
Simple cable tester spots faults, identifies repairs. EDWARD L. RAUB, JR., Electronics 125 (3 Oct. 1974). This simple tester checks circuits as fast as an operator can push buttons, taking less than 1 sec per circuit to verify faults and locate all pins involved in short and open circuits, transpositions and misroutings. For example, a tester containing two 20-button jukebox switches easily checks a 40-conductor harness, including any jumpers, in 40 sec. The unit does not require preprograming, and the principal component is a multibutton push switch with two poles per button, at least one of which is double-throw. A measurement technique of time-dependent dielectric breakdown in MOS capacitors. SEUNG P. LI. Microelectron. & Reliab. 13, 209 (1974). The statistical nature of timedependent dielectric breakdown characteristics in MOS capacitors was evidenced by testing large numbers of capacitors fabricated on single wafers. A multi-point probe and automatic electronic visual display technique are introduced that will yield statistical results which are necessary for the investigation of temperature, electric field, thermal annealing, and radiation effects in the breakdown characteristics, and an interpretation of the physical mechanisms involved. It is shown that capacitors of area greater than 2 × 10 -3 cm 2 may yield worst-case results, and that a multi-point probe of capacitors of smaller sizes can be used to obtain a profile of non-uniformities in the SiO 2 films. MAINTENANCE
AND
REDUNDANCY
electronics technology and microelectronics especially have provided the potential for greatly enhanced standards of reliability. But military electronics can provide many examples where the user has experienced poor reliability, well below both the original staff requirement and the minimum, level of reliability agreed to be attainable by the technical experts and accepted by the contractor. In such situations of disillusion and disappointment the goodwill between the involved parties is usually strained, and reliability theory and practice tend to be discredited. It is against this kind of practical experience that the overall problem of reliability growth in development and of assurance tests in production will be critically examined.
Unpowered to powered failure rate ratio--a key reliability parameter. D. S. TAYLOR. IEEE Trans. Reliab. R-23, 1, 33 (April 1974). The unpowered to powered failure rate ratio (2'/),) is a key system reliability design parameter. An initial assumption of this ratio can greatly influence a system design. Furthermore, some system configurations, e.g. parallel system, are much more sensitive to this ratio
Peak temperature during turnover and the volumetric degradation of switching transistors and ICs. A. P. I ~ I v ~ . Microelectron. & Reliab. 13, 103 (1974). Temperature increase as a consequence of switch-over power transients can be blamed as the cause of some typically volumetric failures, e.g. C-E punch-through and C-B breakdown, in high-level switching operation. Calculating the depth of thermal penetration on both collector junction sides and considering the thermal capacity of this heated-up volume section as well as the thermal resistance for the same, both as a function of time, one gets a fair model for junction temperature rise estimations, i.e. in the knowledge of switchover power vs time function and constructional data of a transistor one can calculate the junction temperature vs time function. Considering several typical transistors of various technologies ranging from the minute transistor on a monolithic IC chip to bulky alloyed Ge or mesa SI power types and assuming a fair structure and even current distribution, it is proved that the arising peak turnover temperature jumps are completely harmless since they are ranging from some hundredth °C (IC transistor) to some °C (power type) at full rated switching power levels. A badly uneven structure, however, leads to thermal runaway and the occurrence of hot spots in the bulk and so to total deterioration (short) since temperature rise is inversely proportional to the junction area involved in actual current conduction, i.e. to the ratio of effective to nominal junction area, especially at power transistors where specific turnover energy density is high. Thus, brief operational screen tests where collector current limiting ratings are transgressed and switching times artificaily elongated, seems to be a good method for sorting out specimens of inherently poor structure which are prone to volumetric degradation. On the contrary, switching power levels of bipolar IC transistors are so low that the whole bulk-degradation effect can be neglected and so a costly switching-operation life test seems as unreasonable as superfluous at ICs, at least as compared to effective but cheap d.c. operational methods.
Radiation-stimulated failure mechanism in a dielectrically isolated integrated circuit. J. L. AZAREWtCZ and T. F. 3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability analysis of regular distributed chain structures. R. J. MORGAN and W. H. HOLMES. IEEE Trans. Reliab. R-23, 1, 11 (April 1974). This paper considers the reliability analysis of chain structures of identical sections. The sections are distributed in the sense that there is more than one input and output node to each section. System failure occurs if no path exists between system input and output. (System branch failures are by open circuit only.) This model is particularly applicable to redundant communication systems. It is shown that the distributed chain structure is asymptotically equivalent to a series structure of identical equivalent sections, assuming that the number of sections is large and that the branch reliabilities are equal. The reliability of the equivalent section is obtained as the subdominant eigenvalue of a transition matrix. The error in this representation is negligible for system branch reliabilities large.
The problems of reliability growth and demonstrations with military electronics. J. E. GREEN. Microelectron. & Reliab. 12, 513 (1972). The last decade has seen major changes in
21
WROBEL. Proc. IEEE 24th Electronic Components Conference, Washington D.C. 48 (13-15 May 1975). An apparent latchup condition has been observed in a dielectrically isolated integrated circuit. This circuit has been analyzed with non-destructive tests using Linae and laboratory measurements, and the failure mechanism has been identified. The device package was then opened, and the failure path was verified visually. Upon removal of a metalization short, which was the cause of the failure, the device returned to normal operation.
Simple cable tester spots faults, identifies repairs. EDWARD L. RAUB, JR., Electronics 125 (3 Oct. 1974). This simple tester checks circuits as fast as an operator can push buttons, taking less than 1 sec per circuit to verify faults and locate all pins involved in short and open circuits, transpositions and misroutings. For example, a tester containing two 20-button jukebox switches easily checks a 40-conductor harness, including any jumpers, in 40 sec. The unit does not require preprograming, and the principal component is a multibutton push switch with two poles per button, at least one of which is double-throw. A measurement technique of time-dependent dielectric breakdown in MOS capacitors. SEUNG P. LI. Microelectron. & Reliab. 13, 209 (1974). The statistical nature of timedependent dielectric breakdown characteristics in MOS capacitors was evidenced by testing large numbers of capacitors fabricated on single wafers. A multi-point probe and automatic electronic visual display technique are introduced that will yield statistical results which are necessary for the investigation of temperature, electric field, thermal annealing, and radiation effects in the breakdown characteristics, and an interpretation of the physical mechanisms involved. It is shown that capacitors of area greater than 2 × 10 -3 cm 2 may yield worst-case results, and that a multi-point probe of capacitors of smaller sizes can be used to obtain a profile of non-uniformities in the SiO 2 films. MAINTENANCE
AND
REDUNDANCY
electronics technology and microelectronics especially have provided the potential for greatly enhanced standards of reliability. But military electronics can provide many examples where the user has experienced poor reliability, well below both the original staff requirement and the minimum, level of reliability agreed to be attainable by the technical experts and accepted by the contractor. In such situations of disillusion and disappointment the goodwill between the involved parties is usually strained, and reliability theory and practice tend to be discredited. It is against this kind of practical experience that the overall problem of reliability growth in development and of assurance tests in production will be critically examined.
Unpowered to powered failure rate ratio--a key reliability parameter. D. S. TAYLOR. IEEE Trans. Reliab. R-23, 1, 33 (April 1974). The unpowered to powered failure rate ratio (2'/),) is a key system reliability design parameter. An initial assumption of this ratio can greatly influence a system design. Furthermore, some system configurations, e.g. parallel system, are much more sensitive to this ratio