Centrifugal Stretching of C4 Joints
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
This is a technique for stretching C4 joints by accelerating silicon wafers away from a substrate. The C4 (controlled collapse chip connection) solder joint is used to connect a variety of silicon devices to underlying substrate/ packages. The joint is an array of low-melting-point metal posts or balls which provide support and electrical I/O for the silicon chips. Differences in the coefficients of expansion of silicon and the substrate require that the C4 joint be sufficiently flexible to accommodate differential thermal strains generated when the device is warmed to its operating temperature and cooled to the ambient temperature.