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Failure probability of strict consecutive-k-out-of-n:F systems
648
World Abstracts on Microelectronics and Reliability
and Maintainability, Union of Japanese Scientists and Engineers, 35 (2-4 June 1987). In the THB (Temperature Humidity Bias) test, a reliability test for plastic packaged ICs, testing was conducted on ICs with and without heat sinking. The ICs' different exothermic temperatures, different structures, and different moisture penetrating processes are projected to cause a difference in the effects on their moisture resistance. For both heat sink and non-heat sink ICs, we measured the relationship between the exothermic temperature and the moisture penetrating process, and the coefficient of moisture absorption and mean time to failure in a THB (850C/85~ RH) test using five kinds of ICs and six different bias on/off ratios. An overview of IC failure analysis. D, R. JONES and M. WOODWARD. New Electron., 45 (April 1988). The failure mode of an IC device is defined as that characteristic of the device for which it has been classified a failure, i.e. deviation from specification or desired performance. The principal IC failure modes are summarised. The actual failure analysis procedure depends on the type of device, expected failure mechanisms, observed failure modes, package construction and technology used. The general steps in an orderly failure analysis are shown. This simplified flow diagram stresses the importance of establishing the potential failure mechanisms, based on all data available, before any actual analytical steps or other destructive or non-destructive tests.
3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability modeling and evaluation for networks under multiple and fluctuating operational conditions. JOHN YUAN, CHIN-Hu LIN, SAY JAU CHANG and StaiN-Hun LAL IEEE Trans. Reliab. R-36, 557 (1987). A simple multistate Markov process models a component and a system of any configuration under several operational conditions. Based on it, a simple tie-set approach calculates availability and frequencies-of-system-failure during different conditions; a cut-set approach calculates probabilities and frequencies of system-failure during various conditions. There are two interpretations of operational conditions: (1) environment such as weather or stress, and (2) operating conditions such as occur in several sequential or fluctuating phases. As the system is assumed at any moment under a condition with a certain probability or weight, some relative reliability measures can be further obtained simply to identify which conditions are disastrous. Failure probability of strict consecutive-k-out-of-n:F systems. IEEE Trans. Reliab. R-36, 551 (1987). Ahmad (1982) has published a technique to compute the reliability of a network without resorting to paths or cutsets. However, the technique uses a random choice of next node connected to the previous node in the construction of a tree. This approach can lead to a large number of terms in the reliability expression. Our modified version of the Ahmad technique always produces a reliability expression with the same or fewer terms as the original technique. Reliability of systems with consecutive minimal cutsets. J. GEORGE SHANTH1KUMAR.IEEE Trans. Reliab. R-36, 546 (1987). A system with n components in sequence is a strict consecutive-k-out-of-n:F system if and only if it fails when at least k consecutive components are failed, but isolated strings of component failures of length less than k do not occur. This paper gives the failure probability function of a strict linear consecutive-k-out-of-n:F system in a closed
A more detailed approach is illustrated. This is in no way the only possible methodology and the use of some specialised technique in a different part of the analysis is not precluded.
Horizontal die cracking as a yield and reliability problem in integrated circuit devices. YEHYA M. KASEM and LEo G. FEINSTEIN. IEEE Trans. Compon. Hybrids mfq Technol. CHMT-12, 654 (1987). The problem of horizontal silicon die cracking, which can occur in CERDIP packages with glass as a die bonding material, is addressed. This fracture mode has been attributed to the combined effects of mechanical and thermal stresses. The mechanism of the fracture will be proposed and related to both the die edge condition and the die attach process. The saw-and-break die separation method is identified as the prime source of stress raisers and die edge damage. Sudden cooling causes internal thermal stress and mechanical loads in the assembly due to the solidification of the glass die attach medium and the mismatch of the coefficients of thermal expansion in the package components. The development of a nondestructive sequential screening test and accept/reject criteria for devices that are more likely to develop cracks in the field during temperature changes or slight mechanical loading are described. In addition, the results of a quantitative computer analysis are presented. This analysis is based on the finiteelement method and is performed to determine temperature distribution and stress levels inside the die as a result of the cooling process. Remedial recommendations for minimizing the problem are outlined.
MAINTENANCE
AND
REDUNDANCY
form. The calculation of the failure probability of a strict circular consecutive-k-out-of-n:F system is reduced to the linear case.
A method for evaluating all the minimal cuts of a graph. G. B. JASMON and K. W. FOONG. IEEE Trans. Reliab. R-36, 539 (1987). This paper presents a new technique to determine all minimal cuts for all the sink nodes in a non-planar network. The algorithm uses a subset method and an iterative process to achieve high effeciency. For an N-sink node network there are ( 2 N - l ) possible combinations of nodes (non-empty subsets). These subsets are checked against several conditions to see if they can be transformed into minimal cutsets. An iterative process is used to generate these non-empty subsets efficiently so that the number of subsets to be checked is about (U"-1)/2. Since this algorithm generates all the minimal cutsets for all nodes in one operation, it is faster compared to conventional methods which compute for one sink node at a time. Tests using random graphs showed a small cpu time per minimal cutset. Bayesian inference on parameter of exponential distribution and its characteristics. Mlcrno HORIGOME. Proceedings of the 17th Symposium on Reliability and Maintainability, Union of Japanese Scientists and Engineers, 27 (2-4 June 1987). This paper deals with Bayesian inference of parameter of the exponential distribution. As main results have already obtained, their applications are discussed from the practical viewpoints. In particular, this paper places stress on the comparison of the results by the classical method with one by the Bayes method, and comparison of three kinds of data, i.e., the complete data, the Type I censored data and the Type II. Sensitivity study of the cumulant method for evaluating reliability measures of two interconnected systems. Q. AHSAN and K. F. SCHENK.IEEE Trans. Reliab. R-36, 429 (1987). The
World Abstracts on Microelectronics and Reliability
and Maintainability, Union of Japanese Scientists and Engineers, 35 (2-4 June 1987). In the THB (Temperature Humidity Bias) test, a reliability test for plastic packaged ICs, testing was conducted on ICs with and without heat sinking. The ICs' different exothermic temperatures, different structures, and different moisture penetrating processes are projected to cause a difference in the effects on their moisture resistance. For both heat sink and non-heat sink ICs, we measured the relationship between the exothermic temperature and the moisture penetrating process, and the coefficient of moisture absorption and mean time to failure in a THB (850C/85~ RH) test using five kinds of ICs and six different bias on/off ratios. An overview of IC failure analysis. D, R. JONES and M. WOODWARD. New Electron., 45 (April 1988). The failure mode of an IC device is defined as that characteristic of the device for which it has been classified a failure, i.e. deviation from specification or desired performance. The principal IC failure modes are summarised. The actual failure analysis procedure depends on the type of device, expected failure mechanisms, observed failure modes, package construction and technology used. The general steps in an orderly failure analysis are shown. This simplified flow diagram stresses the importance of establishing the potential failure mechanisms, based on all data available, before any actual analytical steps or other destructive or non-destructive tests.
3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability modeling and evaluation for networks under multiple and fluctuating operational conditions. JOHN YUAN, CHIN-Hu LIN, SAY JAU CHANG and StaiN-Hun LAL IEEE Trans. Reliab. R-36, 557 (1987). A simple multistate Markov process models a component and a system of any configuration under several operational conditions. Based on it, a simple tie-set approach calculates availability and frequencies-of-system-failure during different conditions; a cut-set approach calculates probabilities and frequencies of system-failure during various conditions. There are two interpretations of operational conditions: (1) environment such as weather or stress, and (2) operating conditions such as occur in several sequential or fluctuating phases. As the system is assumed at any moment under a condition with a certain probability or weight, some relative reliability measures can be further obtained simply to identify which conditions are disastrous. Failure probability of strict consecutive-k-out-of-n:F systems. IEEE Trans. Reliab. R-36, 551 (1987). Ahmad (1982) has published a technique to compute the reliability of a network without resorting to paths or cutsets. However, the technique uses a random choice of next node connected to the previous node in the construction of a tree. This approach can lead to a large number of terms in the reliability expression. Our modified version of the Ahmad technique always produces a reliability expression with the same or fewer terms as the original technique. Reliability of systems with consecutive minimal cutsets. J. GEORGE SHANTH1KUMAR.IEEE Trans. Reliab. R-36, 546 (1987). A system with n components in sequence is a strict consecutive-k-out-of-n:F system if and only if it fails when at least k consecutive components are failed, but isolated strings of component failures of length less than k do not occur. This paper gives the failure probability function of a strict linear consecutive-k-out-of-n:F system in a closed
A more detailed approach is illustrated. This is in no way the only possible methodology and the use of some specialised technique in a different part of the analysis is not precluded.
Horizontal die cracking as a yield and reliability problem in integrated circuit devices. YEHYA M. KASEM and LEo G. FEINSTEIN. IEEE Trans. Compon. Hybrids mfq Technol. CHMT-12, 654 (1987). The problem of horizontal silicon die cracking, which can occur in CERDIP packages with glass as a die bonding material, is addressed. This fracture mode has been attributed to the combined effects of mechanical and thermal stresses. The mechanism of the fracture will be proposed and related to both the die edge condition and the die attach process. The saw-and-break die separation method is identified as the prime source of stress raisers and die edge damage. Sudden cooling causes internal thermal stress and mechanical loads in the assembly due to the solidification of the glass die attach medium and the mismatch of the coefficients of thermal expansion in the package components. The development of a nondestructive sequential screening test and accept/reject criteria for devices that are more likely to develop cracks in the field during temperature changes or slight mechanical loading are described. In addition, the results of a quantitative computer analysis are presented. This analysis is based on the finiteelement method and is performed to determine temperature distribution and stress levels inside the die as a result of the cooling process. Remedial recommendations for minimizing the problem are outlined.
MAINTENANCE
AND
REDUNDANCY
form. The calculation of the failure probability of a strict circular consecutive-k-out-of-n:F system is reduced to the linear case.
A method for evaluating all the minimal cuts of a graph. G. B. JASMON and K. W. FOONG. IEEE Trans. Reliab. R-36, 539 (1987). This paper presents a new technique to determine all minimal cuts for all the sink nodes in a non-planar network. The algorithm uses a subset method and an iterative process to achieve high effeciency. For an N-sink node network there are ( 2 N - l ) possible combinations of nodes (non-empty subsets). These subsets are checked against several conditions to see if they can be transformed into minimal cutsets. An iterative process is used to generate these non-empty subsets efficiently so that the number of subsets to be checked is about (U"-1)/2. Since this algorithm generates all the minimal cutsets for all nodes in one operation, it is faster compared to conventional methods which compute for one sink node at a time. Tests using random graphs showed a small cpu time per minimal cutset. Bayesian inference on parameter of exponential distribution and its characteristics. Mlcrno HORIGOME. Proceedings of the 17th Symposium on Reliability and Maintainability, Union of Japanese Scientists and Engineers, 27 (2-4 June 1987). This paper deals with Bayesian inference of parameter of the exponential distribution. As main results have already obtained, their applications are discussed from the practical viewpoints. In particular, this paper places stress on the comparison of the results by the classical method with one by the Bayes method, and comparison of three kinds of data, i.e., the complete data, the Type I censored data and the Type II. Sensitivity study of the cumulant method for evaluating reliability measures of two interconnected systems. Q. AHSAN and K. F. SCHENK.IEEE Trans. Reliab. R-36, 429 (1987). The