Magnetic Modelling of Droplet Pad Shapes by Ferromagnetic Fluids
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
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.