Experimental determination of interfacial toughness curves

Abstract

The evaluation of mixed-mode interfacial fracture toughness is of great importance for the integrity of electronic devices because interfacial cracks are subjected to mixed-mode loading by vapor pressure, thermal stress and other factors. A lot of work has been done to clarify the unusual characteristics of the fracture of bimaterial interfaces. Since interfacial fracture toughness (G C ) greatly depends on phase angle (ψ), most work has focused on the determination of G C -ψ curves using various specimens. However, this requires a lot of time, expense and effort. In this work, the G C -ψ curves of oxidized Cu-based leadframe/EMC (epoxy molding compound) interfaces were determined by measuring interfacial fracture toughness under mode-I, mode-II and mixed-mode loading conditions using sandwiched-double-cantilever-beam (SDCB) specimens, Arcan specimens and sandwiched-Brazilian-nut (SBN) specimens, respectively. The experimental results showed that the measured G C -ψ curves obeyed the G C -ψ expression proposed by Ahmad first developed by Evans and Hutchinson based on the micromechanics modeling of mixed-mode fracture. Comparing data in the literature, the G C -ψ expression proposed by Ahmad was confirmed to be valid, and a method of predicting G C -ψ curves without much experiment was proposed.

Influence of Copper on Decarburization Kinetics of Stainless Steel Melt at High Temperatures.

“…Recently, it has been found that the stainless steel containing copper would exhibit good corrosion resistance, formability, and an antibiotic property. 1) However, it has been observed that the decarburization rate of stainless steel melt containing copper would be delayed in an AOD process.…”

“….... (1) where K (1) is the equilibrium constant of the reaction. The effect of alloying elements on the activity coefficient of carbon (g C ) in molten steel at 1 873 K is given by Eq.…”