DESIGN CONSIDERATIONS FOR FABRICATION OF LARGE AREA, HIGH DENSITY, HIGH LAYER COUNT CIRCUIT BOARD ASSEMBLIES
Author: Deepak K. Pai Company: General Dynamics Date Published: 9/30/2001
Medical Electronics Symposium
Abstract: Replacement of conventional fine pitch leaded devices such as plastic quad flat packages (PQFP) with high I/O count devices such as plastic ball grid array packages (PBGA) is seen as one of the primary ways to further integration of automotive electronic packaging. One major concern with PBGA packages in automotive environments is the vibration durability of the solder ball connections associated with their strength and flexibility. This paper addresses PBGA’s fatigue capability and reliability issues through experiment tests and numerical analysis. Test method, experimental setup, and analytical approaches are presented. Fatigue endurance of a given component is reported as a function of input vibration excitation level and the location of that component. Observed failure mechanisms of PBGA and PQFP components are further discussed. The experimental results show that the PBGA components have superior fatigue performance than the PQFP components do within typical level of vibration excitation. Test data are then fitted to two-parameter Weibull distributions. Master curves are found for cumulative failure rate for solder balls and copper leads, respectively. That master curve covers all Weibull distributions of cumulative failure rates at any given vibration excitation levels. Design guidelines addressing fatigue reliability are discussed in terms of printed circuit board layout and application limitations of given components.