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Thermal stress analysis of a multichip package design
1204
World Abstracts on Microelectronics and Reliability
system that alternates between two modes of system operation. In one mode all s servers are available and in the other mode, only s - 1 servers are available for serving the customers. This is due to breakdown of one of the servers. The random variables representing the system with s servers and s - 1 servers have exponential distributions. In such a system, the steady-state birth/death equations are coupled because of the two modes of operation. A recursive solution is presented for computing steady-state probabilities of such a system. Once these probabilities are known, the performance measures of interest can be easily obtained. Two practical examples validate the results and show the utility of this method. A distinct advantage of the recursive technique is that it is much faster and requires much less memory than the existing non-recursive techniques as has been shown by the authors. In a bi-level situation, the system performance measures are always bounded by two independent queueing systems with s and s - 1 servers. A procedure has been outlined for extension to multiple modes of system operation.
Relayed communication via parallel redundancy. OURANIA CHRYSAPHINOU, STAVROS PAPASTRAVRIDIS and PANOS SYPSAS. IEEE Trans. Reliab. 38(4), 454 (1989). A special communication system with moving relay stations was introduced by Chiang & Chiang. The relay stations are all
moving at the same speed from an origin toward a destination. If k consecutive stations fail before the first station reaches the destination, all stations ahead of the k failed stations as well as the k failed stations are lost. The objective is to have one station reach the destination without k or more consecutive failed stations between the destination and the origin. In this paper a different communication system is described where relay stations are moving in groups of k stations. If all k stations of a group fail, then all groups of k stations ahead of the k failed stations as well as the k failed stations are lost. The objective is to have one station reach the destination with all groups having at least one station in good condition. We show that this second communication system requires fewer stations on the average. Also we examine the probability distribution of the numbers of station required in the first communication system.
Bounds on the reliability of binary coherent systems. FRANK BEICHELT and LUTZ SPROSS.IEEE Trans. Reliab. 38(4), 425 (1989). The structure function of a binary coherent system is approximated by using only a few of its minimal path sets and of its minimal cut sets. These two "incomplete" structure functions are represented as disjoint sums. The average of each is a lower and upper hand bound, respectively, for the system reliability. The usefulness of these bounds is demonstrated on example networks.
4. M I C R O E L E C T R O N I C S ~ - G E N E R A L
Semiconductor vendors paying closer attention to ASIC. JEE (Japan) 27 (February 1990). While demand for semiconductors has intensified since 1988, prices also have remained high, allowing chip vendors to achieve record results. Lately, however, some signs of a slowdown in the American computer industry have appeared and expansion appears to have given way to transition. Prices also may decline as supply of IM-bit DRAMs, which has propelled the semiconductor market, meets demand as a result of increased production. Electric measuring equipment output to reach ¥ 700 billion. JEE (Japan) 54 (February 1990). Despite a drop in IC tester
output late in the year, Japanese electric measuring instrument production in 1989 is likely to reach ¥700 billion, surpassing 1988's record ¥657.5 billion. The value of production rose 11.6 percent to ¥423.344 billion in the first seven months of the year, according to the Ministry of International Trade and Industry.
Multichip modules: next-generation packages. ROBERTR. JOHNSON. IEEE Spectrum 34 (March 1990). Reduced delays between chips, simplified power distribution, and enhanced dissipation capabilities are among the advantages of assembling and encapsulating dice on substrates.
5. M I C R O E L E C T R O N I C S - - D E S I G N
Thermal stress analysis of a mulflebip package design. ROBERT DARVEAUX,IWONATURLIK, LIH-TYNG HWANG and ARNOLDI~ISMAN. IEEE Trans. Compon. Hybrids mfg Technol. 12(4), 663 (1989). In this paper, we provide a thermal analysis of our package design, with emphasis on thermally induced stress in the critical package components. The package employs flip-chip solder bonding and thin-film interconnections between chips. Indium was chosen as the die attachment medium between each chip and the water cooled heat sink. A methodology is given to estimate the stresses in the structure during a power-up. Finite difference and finite element computer simulations were used to calculate the temperature and stress distributions under both transient and steady-state conditions. It was shown how thermal gradients, expansion mismatches, and global bending of the structure determine the stress distribution. The components in the module have various thermal time constants, and the stresses during a transient are related to the rate at which each component heats up. Therefore, even if a design is optimized to be thermal expansion matched under operating conditions, stresses can develop during a transient.
AND
CONSTRUCTION
Thermal studies on finned LSI packages using forced convection. YASUYUKIYOKONO and MASARUISHlZUKA. IEEE Trans. Comport. Hybrids mfg TechnoL 12(4), 753 (1989). This paper describes extensive computer-based analytical as well as experimental studies on finned LSI packages, utilizing a Cavity Down type QFP348pin (Quad Flat Pack 348pin) package, in order to examine the simulation method for a high thermal performance package and its heat sink. The numerical analysis was accomplished for a conjugate problem, which encompassed flow and heat transfer in the cooling air stream and heat conduction in the package and the heat sink. Experiments were conducted to measure the temperature rise at the junction, the package surface, and the fin, using several kinds of omnidirectional heat sink fins in a wind tunnel. The applicability of the model used for the simulation and also the computational scheme were verified by comparing the experimental results with those obtained on the basis of the present model. These comparisons lead to the conclusion that the proposed numerical method of predicting the thermal resistance of finned LSI packages is expected to serve satisfactorily for thermal designers.
World Abstracts on Microelectronics and Reliability
system that alternates between two modes of system operation. In one mode all s servers are available and in the other mode, only s - 1 servers are available for serving the customers. This is due to breakdown of one of the servers. The random variables representing the system with s servers and s - 1 servers have exponential distributions. In such a system, the steady-state birth/death equations are coupled because of the two modes of operation. A recursive solution is presented for computing steady-state probabilities of such a system. Once these probabilities are known, the performance measures of interest can be easily obtained. Two practical examples validate the results and show the utility of this method. A distinct advantage of the recursive technique is that it is much faster and requires much less memory than the existing non-recursive techniques as has been shown by the authors. In a bi-level situation, the system performance measures are always bounded by two independent queueing systems with s and s - 1 servers. A procedure has been outlined for extension to multiple modes of system operation.
Relayed communication via parallel redundancy. OURANIA CHRYSAPHINOU, STAVROS PAPASTRAVRIDIS and PANOS SYPSAS. IEEE Trans. Reliab. 38(4), 454 (1989). A special communication system with moving relay stations was introduced by Chiang & Chiang. The relay stations are all
moving at the same speed from an origin toward a destination. If k consecutive stations fail before the first station reaches the destination, all stations ahead of the k failed stations as well as the k failed stations are lost. The objective is to have one station reach the destination without k or more consecutive failed stations between the destination and the origin. In this paper a different communication system is described where relay stations are moving in groups of k stations. If all k stations of a group fail, then all groups of k stations ahead of the k failed stations as well as the k failed stations are lost. The objective is to have one station reach the destination with all groups having at least one station in good condition. We show that this second communication system requires fewer stations on the average. Also we examine the probability distribution of the numbers of station required in the first communication system.
Bounds on the reliability of binary coherent systems. FRANK BEICHELT and LUTZ SPROSS.IEEE Trans. Reliab. 38(4), 425 (1989). The structure function of a binary coherent system is approximated by using only a few of its minimal path sets and of its minimal cut sets. These two "incomplete" structure functions are represented as disjoint sums. The average of each is a lower and upper hand bound, respectively, for the system reliability. The usefulness of these bounds is demonstrated on example networks.
4. M I C R O E L E C T R O N I C S ~ - G E N E R A L
Semiconductor vendors paying closer attention to ASIC. JEE (Japan) 27 (February 1990). While demand for semiconductors has intensified since 1988, prices also have remained high, allowing chip vendors to achieve record results. Lately, however, some signs of a slowdown in the American computer industry have appeared and expansion appears to have given way to transition. Prices also may decline as supply of IM-bit DRAMs, which has propelled the semiconductor market, meets demand as a result of increased production. Electric measuring equipment output to reach ¥ 700 billion. JEE (Japan) 54 (February 1990). Despite a drop in IC tester
output late in the year, Japanese electric measuring instrument production in 1989 is likely to reach ¥700 billion, surpassing 1988's record ¥657.5 billion. The value of production rose 11.6 percent to ¥423.344 billion in the first seven months of the year, according to the Ministry of International Trade and Industry.
Multichip modules: next-generation packages. ROBERTR. JOHNSON. IEEE Spectrum 34 (March 1990). Reduced delays between chips, simplified power distribution, and enhanced dissipation capabilities are among the advantages of assembling and encapsulating dice on substrates.
5. M I C R O E L E C T R O N I C S - - D E S I G N
Thermal stress analysis of a mulflebip package design. ROBERT DARVEAUX,IWONATURLIK, LIH-TYNG HWANG and ARNOLDI~ISMAN. IEEE Trans. Compon. Hybrids mfg Technol. 12(4), 663 (1989). In this paper, we provide a thermal analysis of our package design, with emphasis on thermally induced stress in the critical package components. The package employs flip-chip solder bonding and thin-film interconnections between chips. Indium was chosen as the die attachment medium between each chip and the water cooled heat sink. A methodology is given to estimate the stresses in the structure during a power-up. Finite difference and finite element computer simulations were used to calculate the temperature and stress distributions under both transient and steady-state conditions. It was shown how thermal gradients, expansion mismatches, and global bending of the structure determine the stress distribution. The components in the module have various thermal time constants, and the stresses during a transient are related to the rate at which each component heats up. Therefore, even if a design is optimized to be thermal expansion matched under operating conditions, stresses can develop during a transient.
AND
CONSTRUCTION
Thermal studies on finned LSI packages using forced convection. YASUYUKIYOKONO and MASARUISHlZUKA. IEEE Trans. Comport. Hybrids mfg TechnoL 12(4), 753 (1989). This paper describes extensive computer-based analytical as well as experimental studies on finned LSI packages, utilizing a Cavity Down type QFP348pin (Quad Flat Pack 348pin) package, in order to examine the simulation method for a high thermal performance package and its heat sink. The numerical analysis was accomplished for a conjugate problem, which encompassed flow and heat transfer in the cooling air stream and heat conduction in the package and the heat sink. Experiments were conducted to measure the temperature rise at the junction, the package surface, and the fin, using several kinds of omnidirectional heat sink fins in a wind tunnel. The applicability of the model used for the simulation and also the computational scheme were verified by comparing the experimental results with those obtained on the basis of the present model. These comparisons lead to the conclusion that the proposed numerical method of predicting the thermal resistance of finned LSI packages is expected to serve satisfactorily for thermal designers.