Method of Eliminating Static and Dynamic C-4 Fatigue Problems
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
A method is proposed which eliminates static and dynamic C-4 fatigue problems. It comprises rules for the selection of materials and/or bodies to avoid C-4 fatigue problems caused by static and/or dynamic thermal expansion of chips and carriers. The materials and bodies are selected such that the coefficients of thermal expansion prevent static shearing stress in the C-4 balls and that during the warm-up phase of the system, the shearing stress in them is of very short duration, so that the balls can be considered elastic, i.e., they are not subject to crystallization. (Image Omitted) Fig. 1 shows a flip-chip assembly. The heat sink of the assembly is positioned underneath the carrier, Fig. 2 shows the equivalent electric circuit for the assembly of Fig. 1.