Analysis of mechanical properties of thermal cycled Cu Plated-Through Holes (PTH)

Abstract

The aim of thermo-mechanical reliability assessment in microelectronic packages is life time prediction under different thermal and mechanical induced stress loads. The analysis of long time stability of thermally loaded Plated- Through-Holes (PTH) in Printed Circuit Board (PCB) also requires an accurate determination of material data. This leads to application of different test and measurement methods, which are allowed to measure mechanical materials properties at micro- and/or nanostructural scale. This paper focuses on application of instrumented nanoindentation measurement technique for analysis of mechanical properties of microelectronic relevant electroplating copper. Nanoindentation method has been widely used for characterization of mechanical behaviour of devices in small volume (especially for PTH) and determined typically elastic mechanical properties (reduced modulus and hardness). In combination of modified Finite-Element (FE) simulation models and nanoindentation test results elastic and plastic material properties of copper in small scale were obtained. It was dimensionless functions for determination of presentable stresses developed, which allows to indicate the stress-strain curve of bulk materials. It is a precondition to implementation of this function that the indentation depth is out of indentation size effect. The presentation of calculated stress-strain curves by using of dimensionless function and the influence of thermal cycling of material behaviour of PTH are subject of this paper.