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Modelling joining materials for microelectronics packaging
554
World abstracts on microelectronics and reliability
pad damage caused by the carrier contacts. Electrical evaluations include continuity and electrical test performance at multiple temperatures.
The reliability of aluminum metailization with a polyimide passivation. M. SATSUNTANI, T. WADA, H. KINOSHITA and H. ASADA. Proceedings of the 24th Symposium on Reliability and Maintainability, Tokyo, Japan, 23 (6-8 July 1994). Through the investigation of reliability issues of aluminum metallization with a polyimide passivation, it is found that the stress-migration resistance and moisture resistance of aluminum metallization with a polyimide is equivalent to those with the conventional SiO2 passivation. On the other hand, electromigration resistance is lower than that of the conventional passivation.
Reliability Au-Sn flip-chip bonding on flexible prints. ANTAL F. J. BAGGERMAN and MARTIN J. BATENBURG. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 257 (May 1995). Flip-chip bonding, with an Au-Sn metallization system, has been successfully introduced for the mounting of integrated circuits (IC's) on flexible polyimide prints. Since most consumer electronics, and more specifically for hearing instruments, the usable volume is decreasing very rapidly, maximum miniaturization is achieved by using flip-chips. In order to avoid open circuits during reflow soldering of all other components, a high melting soldering process is required for the bonding of the IC's. An additional advantage of the Au-Sn process is that the bumps do not completely melt, and a certain stand-off height is guaranteed. The bumps are deposited on top of the bond pads and are bonded to copper tracks on a polyimide foil. The required tin is either deposited on the bump or on the copper tracks, Both Au-Sn soldering processes are performed by using pulsed heat thermode (gang) bonding. It has been found that the quality of the bonds depends on the microstructure formed in the bonding region. Energy dispersed X-ray analysis (EDX) measurements indicate that eutectic (80/20) Au-Sn or ~' phases are required for good quality bonds. To obtain these phases, the temperature at the interface and the initial amount of tin are optimized. As a consequence of a large thermal mismatch and a small stand-off height of the IC, the number of cycles to failure during temperature shock experiments is limited. The results are remarkably improved (by a factor of 20) by using an epoxy-based underfill material.
Modelling joining materials for microelectronies packaging. JORMA K. KIVILAHTI. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 326 (May 1995). Modelling of solder-substrate interactions together with careful experimental work can provide a good basis for developing new materials such as conductive adhesives and Pb-free solders as well as fluxless soldering
processes for microelectronics packaging. The modeling of the solder-substrate interactions will in effect lead to a rationalization of the trial and error methods commonly employed and hence minimize the number of experiments required. It provides useful information on the chemical reactions, stabilities of various microstructures and growth rates of reaction products during joining or in use of electronic devices. This is of particular importance in the case of small solder volumes, since the compositions and microstructures of solder alloys can be entirely altered by the solder-substrate reactions during the joining. As specific examples the solder-substrate reactions have been investigated in the Sn-Bi/Cu and Sn-Bi-Zn/Cu systems with and without adhesives. The soldersubstrate-environment interactions under high purity reducing gases have been studied also with the meniscograph. The reduction of surface oxides, formation and the stability of the intermetallic layers, Cu3Sn and Cu6Sns, and the growth of brittle Bi layer in the microjoints due to the change of the composition of the solder filler was studied both theoretically and experimentally. Moreover, an explanation concerning the strong dewetting effect of zinc-containing solders found experimentally is given. An emphasis was placed also on the solder-substrate environment interaction by studying the effect of humidity on chemical stability of microjoints in an epoxy-based adhesive.
Conductive adhesives for SMT and potential applications. HENRIK L. HVIMS. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 284 (May 1995). Environmental issues have an ever-increasing influence on the selection of materials and processes in electronic manufacturing. This paper discusses the use of conductive adhesives as a replacement for solder on SMT-printed circuit boards. As a result of a world-wide market survey, a number of conductive adhesives have been selected. The key issue of this paper has been to uncover the market for adhesive types and their composition, as well as the technical investigation of the influence of component termination and printed-circuit surface types on adhesive bonding stability. Four different types of adhesives on two different metal surfaces are compared with conventional solder technology. Each adhesive has been applied to the PCB's by either screen printing or dispensing according to the manufacturer's recommendation, followed by curing. All PCB's went through thermal and humidity cycling followed by electrical measurements of resistance; all variants have been adhesion tested. All adhesive variants have been microsectioned for metallurgical and microstructure examination. Energy Dispersive Analysis of X-ray (EDAX) of the metal particles in the adhesive has been carried out and documented. Rework of conductive joints is briefly addressed. Finally, aspects of occupational health are discussed concerning work
World abstracts on microelectronics and reliability
pad damage caused by the carrier contacts. Electrical evaluations include continuity and electrical test performance at multiple temperatures.
The reliability of aluminum metailization with a polyimide passivation. M. SATSUNTANI, T. WADA, H. KINOSHITA and H. ASADA. Proceedings of the 24th Symposium on Reliability and Maintainability, Tokyo, Japan, 23 (6-8 July 1994). Through the investigation of reliability issues of aluminum metallization with a polyimide passivation, it is found that the stress-migration resistance and moisture resistance of aluminum metallization with a polyimide is equivalent to those with the conventional SiO2 passivation. On the other hand, electromigration resistance is lower than that of the conventional passivation.
Reliability Au-Sn flip-chip bonding on flexible prints. ANTAL F. J. BAGGERMAN and MARTIN J. BATENBURG. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 257 (May 1995). Flip-chip bonding, with an Au-Sn metallization system, has been successfully introduced for the mounting of integrated circuits (IC's) on flexible polyimide prints. Since most consumer electronics, and more specifically for hearing instruments, the usable volume is decreasing very rapidly, maximum miniaturization is achieved by using flip-chips. In order to avoid open circuits during reflow soldering of all other components, a high melting soldering process is required for the bonding of the IC's. An additional advantage of the Au-Sn process is that the bumps do not completely melt, and a certain stand-off height is guaranteed. The bumps are deposited on top of the bond pads and are bonded to copper tracks on a polyimide foil. The required tin is either deposited on the bump or on the copper tracks, Both Au-Sn soldering processes are performed by using pulsed heat thermode (gang) bonding. It has been found that the quality of the bonds depends on the microstructure formed in the bonding region. Energy dispersed X-ray analysis (EDX) measurements indicate that eutectic (80/20) Au-Sn or ~' phases are required for good quality bonds. To obtain these phases, the temperature at the interface and the initial amount of tin are optimized. As a consequence of a large thermal mismatch and a small stand-off height of the IC, the number of cycles to failure during temperature shock experiments is limited. The results are remarkably improved (by a factor of 20) by using an epoxy-based underfill material.
Modelling joining materials for microelectronies packaging. JORMA K. KIVILAHTI. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 326 (May 1995). Modelling of solder-substrate interactions together with careful experimental work can provide a good basis for developing new materials such as conductive adhesives and Pb-free solders as well as fluxless soldering
processes for microelectronics packaging. The modeling of the solder-substrate interactions will in effect lead to a rationalization of the trial and error methods commonly employed and hence minimize the number of experiments required. It provides useful information on the chemical reactions, stabilities of various microstructures and growth rates of reaction products during joining or in use of electronic devices. This is of particular importance in the case of small solder volumes, since the compositions and microstructures of solder alloys can be entirely altered by the solder-substrate reactions during the joining. As specific examples the solder-substrate reactions have been investigated in the Sn-Bi/Cu and Sn-Bi-Zn/Cu systems with and without adhesives. The soldersubstrate-environment interactions under high purity reducing gases have been studied also with the meniscograph. The reduction of surface oxides, formation and the stability of the intermetallic layers, Cu3Sn and Cu6Sns, and the growth of brittle Bi layer in the microjoints due to the change of the composition of the solder filler was studied both theoretically and experimentally. Moreover, an explanation concerning the strong dewetting effect of zinc-containing solders found experimentally is given. An emphasis was placed also on the solder-substrate environment interaction by studying the effect of humidity on chemical stability of microjoints in an epoxy-based adhesive.
Conductive adhesives for SMT and potential applications. HENRIK L. HVIMS. IEEE Transactions on Components, Packaging and Manufacturing Technology, Part B, 18(2), 284 (May 1995). Environmental issues have an ever-increasing influence on the selection of materials and processes in electronic manufacturing. This paper discusses the use of conductive adhesives as a replacement for solder on SMT-printed circuit boards. As a result of a world-wide market survey, a number of conductive adhesives have been selected. The key issue of this paper has been to uncover the market for adhesive types and their composition, as well as the technical investigation of the influence of component termination and printed-circuit surface types on adhesive bonding stability. Four different types of adhesives on two different metal surfaces are compared with conventional solder technology. Each adhesive has been applied to the PCB's by either screen printing or dispensing according to the manufacturer's recommendation, followed by curing. All PCB's went through thermal and humidity cycling followed by electrical measurements of resistance; all variants have been adhesion tested. All adhesive variants have been microsectioned for metallurgical and microstructure examination. Energy Dispersive Analysis of X-ray (EDAX) of the metal particles in the adhesive has been carried out and documented. Rework of conductive joints is briefly addressed. Finally, aspects of occupational health are discussed concerning work