Determining Interfacial Adhesion Performance and Reliability for Microelectronics Applications Using a Wedge Test Method

Abstract

Fracture mechanics is an effective approach for characterizing material resistance to interfacial failure and for making interface reliability predictions. Because interfacial bond integrity is a major concern for performance and reliability, the need to evaluate the fracture and delamination resistance of an interface under different environmental conditions is very important. This study investigates the effects of temperature, solution chemistry and environmental preconditioning, in several solutions on the durability of silicon/epoxy and glass/epoxy systems. A series of experiments was conducted using wedge test specimens to investigate the adhesion performance of the systems subjected to a range of environmental conditions. Both silicon and glass systems were relatively insensitive to temperature over a range of 22-60°C, but strongly accelerated by temperatures above 60°C, depending on the environmental chemistry and nature of the adhesive system used. Silicon/commercial epoxy specimens were subjected to preconditioning in deionized (DI) water and more aggressive solution mixtures prior to wedge insertion to study the effect of prior environmental exposure time on the system. The wedge test data from preconditioned specimens were compared with standard wedge test results and the system was insensitive to preconditioning in DI water but was affected significantly by preconditioning in aggressive environments. Plots describing - G (crack velocity versus applied strain energy release rate) characteristics for a particular set of environmental conditions are presented and a comparison is made for different environmental conditions to quantify the subcritical debonding behavior of systems studied. A kinetic model to characterize subcritical debonding of adhesives for microelectronic applications is also proposed based on molecular interactions between epoxy and a silane coupling agent at the interface and linear elastic fracture mechanics, which could help predict long-term deterioration of interfacial adhesion.