Elliptic C4 with optimal orientation for enhanced reliability in electronic packages

A method for forming electrical interconnects in an electronic package between a substrate and a semiconductor chip, said method comprising providing an array of C4 solder joints, each respectively connecting a metal pad on the surface of said substrate with a symmetrical metal pad located oppositely thereof on a surface of said semiconductor chip, forming an interconnect, wherein at least a portion of the array of C4 solder joints has oppositely facing metal pads on said substrate and semiconductor chip are of conformant elliptical configurations;

• a remaining portion constituted of non-elliptical metal pads on said substrate and said semiconductor chip being essentially of round or circular configurations, said substrate and said semiconductor chip are each substantially rectangular, said facing elliptical metal pads on said substrate and semiconductor chip being located proximate corner regions of said substantially rectangular semiconductor chip;
• and wherein said elliptical metal pads have minor axes thereof generally aligned along radial directions spaced from a center of said semiconductor chip towards a respectively therewith associated corner region of said semiconductor chip;
• the minor axes of the elliptical metal pads on said substrate and semiconductor chip being oriented to extend in parallel with a relative motion vector encountered between the metal pads on said substrate and the facing metal pads on said semiconductor chip responsive to reflow and operation of said electronic package.