Elliptical, Solder-Post Footprint
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
Present square and circular solder post footprints do not provide the optimum wearout characteristics when joining to materials that have different thermal coefficients of expansion (TCE) in different directions. This invention provides an elongated footprint, preferably elliptical, to optimize wearout when solder post joins are made to a material with different TCEs in different directions. The elliptical footprint takes advantage of the anisotropic thermal expansion properties of some components, as shown in Fig. 1. The connections 2 between a device 1 and a carrier 3 are restricted to a region represented by an ellipse 4. The eccentricity of the ellipse 4 is determined by the ratio of the thermal coefficients of expansion (TCE) for the x and y axes of the carrier component 3.