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Magnetic Modelling of Droplet Pad Shapes by Ferromagnetic Fluids

IP.com Disclosure Number: IPCOM000062512D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Blum, A: AUTHOR [+3]

Abstract

For many contact applications, cylindrically shaped integrated chip pads are required. Standard C-4 (controlled collapse chip connection) pads are, however, ball-shaped with the inherent limitations as to shear strain. To provide more cylindrically shaped chip pads, it is proposed that the standard C-4 pad droplets be plated with a ferromagnetic material which allows them to be shaped in a superior way to obtain pinlike connectors. At the melting temperature of the droplets, the chip, bearing the pad structures, is subjected to a controlled magnetic field. Magnetic interaction with the ferromagnetic plating material leads to the molten chip pad droplets to be cylindrically elongated, elongation being determined by interaction of the magnetic and the adhesive forces of the surface of the chip pad droplet.

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Magnetic Modelling of Droplet Pad Shapes by Ferromagnetic Fluids

For many contact applications, cylindrically shaped integrated chip pads are required. Standard C-4 (controlled collapse chip connection) pads are, however, ball-shaped with the inherent limitations as to shear strain. To provide more cylindrically shaped chip pads, it is proposed that the standard C-4 pad droplets be plated with a ferromagnetic material which allows them to be shaped in a superior way to obtain pinlike connectors. At the melting temperature of the droplets, the chip, bearing the pad structures, is subjected to a controlled magnetic field. Magnetic interaction with the ferromagnetic plating material leads to the molten chip pad droplets to be cylindrically elongated, elongation being determined by interaction of the magnetic and the adhesive forces of the surface of the chip pad droplet. By causing the ferrogmagnetic material to migrate into the body of the chip pad, the liquid droplet pad can be shaped by appropriate magnetic fields, using known practices of ferromagnetic fluid modelling. After lowering the temperature, while retaining the magnetic field and converting the material to a solid phase, the shape of the pad thus obtained is maintained. This method allows fabricating integrated chip pads of high density and improved shear strain characteristics.

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