MOISTURE ABSORPTION AND AUTOCLAVE PERFORMANCE OPTIMIZATION OF GLOB TOP BALL GRID ARRAY
Author: Trent Thompson Company: Motorola Semiconductor Product Date Published: 9/10/1996
Surface Mount International
Abstract: This report summarizes evaluations performed to determine and improve the moisture sensitivity level and autoclave performance of the glob top ball grid array (GTBGA). Two “glob top” or liquid encapsulant with different CTES and rates of moisture absorption were considered. Results horn studies determining the optimal cure profile for the liquid encapsulant are included. The effects of using clean methods A or B at different positions in assembly to enhance encapsulant to die surface and solder resist/substrate adhesion are presented. Flag designs that reduce Cu surface area on the substrate for better die attach adhesion, the optimal substrate solder resist and die attach epoxy for this application are also discussed. These results aR benchmarked with the overmolded plastic ball grid area (PBGA) performance which is a JEDEC Level 5. The reliability test responses are the package peel test which evaluates die bond cohesive strength and encapsulant to solder resist adhesion; C-SAM (C-Mode Scanning Acoustic Microscopy) to inspect for delamination at various package interfaces and weight gain to determine package moisture absorption and reabsorption rates.