Metal fusion bonding – Process – Plural joints
Patent
1989-10-31
1990-11-06
Heinrich, Sam
Metal fusion bonding
Process
Plural joints
228193, 228254, H01L 2160, H05K 334
Patent
active
049679503
ABSTRACT:
A method is described for attaching circuit chips to a flexible substrate (laminate) using controlled chip collapse connection technology (C-4). The substrate is "tinned" with an alloy of eutectic composition in its contact region with the solder balls on the base of the chip. The alloy and the solder are chosen such that they are miscible. The system temperature is raised above the alloy melting point thus causing the alloy and the solder to mix, the mixture composition moving away from the eutectic composition with time and thus raising its melting point. Eventually the mixture melting point is higher than the temperature at which the system is maintained and the mixture solidifies to form a contact. In this way contact between the chip and the flexible substrate can be effected at a temperature below the melting point of the pure solder and lower than one which would result in degradation of the laminate adhesive.
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patent: 4033503 (1977-07-01), Fletcher et al.
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patent: 4465223 (1984-08-01), Cammarano et al.
patent: 4518112 (1985-05-01), Miller et al.
patent: 4876617 (1989-10-01), Citowsky
Lynch et al., "Brazing by the Diffusion-Controlled Formation of a Liquid Intermediate Phase", Welding Journal, Feb. 1959, pp. 85s-89s.
W. A. Dawson et al, "Indium-Lead-Indium Chip Joining", IBM Technical Disclosure Bulletin, vol. 11, No. 11, 4/69, p. 1528.
Legg Stephen P.
Schrottke Gustav
Bryant Andrea P.
Heinrich Sam
International Business Machines - Corporation
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