The current trends of increasing speed and circuit density of integrated circuits have created demands for new electronic packaging technologies. One technology that meets these demands uses multiple layers of thin film conductors1 dielectricsand insulators. To increase the reliability of this thin film technology, the failure mechanisms need to be fully understood. One common failure mechanism is the loss of adhesion between the layers which directly affects the device's performance. Eventhough adhesion strength is of critical importance, there does not exist a broadly applicable method to quantify it. This paper addresses one of the commonly used adhesion measurement techniques: the Z-axis pull test. A finite-element model was used todetermine the accuracy of this method. The finite-element model simulated the shear and adhesion effects during the Z-axis pull test. Polyimide and aluminum thin film adhesion strengths are the focus of this investigation. For the aluminum-polyimide thinfilm assemblies with film thicknesses of 50μm or less, numerical results show that the applied load during the standard Z-axis pull test is transmitted uniformly beneath the stud adhesion area. However, for film thicknesses greater than 500pm, the stress in the adhesion layer is less than the applied load. Experimental stud pull adhesion tests of a 0.Spm aluminum film on a 50μm polyimide film indicate an interface adhesion strength of 19.77MPa. Although this value is less than one-sixth of eithermaterial's yield strength, it is sufficient to pass the military standard thermal shock tests (MILSTD-883) of -60°Cto 155°C. This conclusion was confirmed both experimentally and numerically.
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