Browse Prior Art Database

Composite Solders

IP.com Disclosure Number: IPCOM000061698D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Pollak, RA: AUTHOR

Abstract

The present solders are composites of distinct particles together with fusible metals or alloys. High degrees of compositional freedom greatly increase the number of possible solders and mechanical properties of solders beyond that what can be obtained with metals or alloys alone. Consequently, the range of solder joint design is extended beyond that achievable with conventional fusible metal or alloy solders. It is often desirable to design solders with higher ultimate stress (point at which material starts to neck and break) and with a hierarchy of melting points (e.g., 100 to 300ŒC) to be used for joining electronic components directly to pads on the surface of cards and/or boards. The composite solders have the design degrees of freedom needed for this surface attach application.

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Composite Solders

The present solders are composites of distinct particles together with fusible metals or alloys. High degrees of compositional freedom greatly increase the number of possible solders and mechanical properties of solders beyond that what can be obtained with metals or alloys alone. Consequently, the range of solder joint design is extended beyond that achievable with conventional fusible metal or alloy solders. It is often desirable to design solders with higher ultimate stress (point at which material starts to neck and break) and with a hierarchy of melting points (e.g., 100 to 300OEC) to be used for joining electronic components directly to pads on the surface of cards and/or boards. The composite solders have the design degrees of freedom needed for this surface attach application. The particles in a composite solder can be chosen such that they reinforce the solder joint. For example, the particles can be fibers of a metal with a higher melting point than the fusible metal or alloy component of the composite solder. The extended design range of the composite solders can provide the solutions to a wide variety of additional solder problems. A fusible metal or alloy in the composite solders forms a matrix in which distinct particles are embedded. Enormous numbers of combinations of matrix alloys with the particles are possible and they can be chosen to optimize a wide variety of solder properties in accordance with design parameters described below. Materials which can be used as the matrix include all conventional solder materials: alloys such as Pb:Sn, Ag:Sn, Sn:Zn, Ag:Pb, Cd:Zn, Ag:Cd, Sb:Sn or alloys based on Bi, In, Au or Al. The range of the particles which can be used in the composite solders is essentially infinite. Properties of the particles include composition, microstructure, shape and size. The particles can be composed of many materials including metals and non-metals, such as ceramics. The particles can be uniform in composition or can have microstructure advantageous to the situation. The particles can be coated to adjust the matrix/particle interaction. Shape and size of the particles can be adjusted to design consideration of a given application. Shapes include equiaxed or fibrous particles or shapes between. Chemical interaction between the solder and the anchorage sites (e.g., pads on boards) can also be used as a design parameter. Conventional (e.g., conduction, convection and r...