IMPROVED YIELD AND PERFORMANCE OF BALL-GRID ARRAY PACKAGES - DESIGN AND PROCESSING GUIDELINES FOR UNIFORM AND NONUNIFORM ARRAYS

Two models are presented for analyzing ball-grid array (BGA) solder in terconnects: a) A model for predicting solder joint geometries after a n upright or inverted reflow process and b) a reliability model for es timating maximum shear strain and fatigue life under a global thermal mismatch load condition. The reliability model includes a newly derive d closed-form expression relating the maximum shear strain in a solder joint to the load, material, and joint shape parameters, The models a re used to generate design/processing guidelines that may be used to i mprove the yield of a BGA soldering operation and the inservice reliab ility of the interconnect, potential benefits of using a nonuniform ar ray (i.e., one including joints of different size and shape) are explo red.