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|Investigation of Fracture Toughness and Strain Fields of Copper/Polymer Interface Using Image Correlation Technique|
|Keywords: interface delaminaion, immage correlation, moisture|
|Delamination between copper leadframe and epoxy molding compound of microelectronic devices is a common failure concern. Interfacial adhesion characterizes the resistance of an interface to initiation and growth of interfacial delamination. In general, interface strength is an important factor for the successful fulfilment of package requirements in micro- and nanoelectronics applications. Conventional delamination testing methods need the critical force which leads to crack propagation and do not provide any information about the strain fields before and during the crack propagation. A testing method which has been developed for the high resolution analysis of delamination process is employed. Sandwiched metal/polymer/metal 4-Point Bending specimens were employed to measure the adhesion strength in terms of interfacial fracture toughness. During the bending tests, high resolution images of the crack tip area were taken at different loading states. These images were analyzed later by microDAC technique (i.e. micro deformation analysis by image correlation). The microDAC approach is based on the application of digital cross correlation on greyscale submatrices of the analysed images. The result is a full-field displacement description of the analyzed surface. In combination with Finite Element Models, interface crack modes can be analyzed and the mode mixity can be derived. This is an important factor which must be known for the analysis of interface reliability. In addition to this high resolution full-field analysis, fracture surfaces were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to determine the failure path and mechanisms.|
|M. Hossein Shirangi, Student
Robert Bosch GmbH
Reutlingen, BW 72762,