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Materials Science at Oregon State University

Graduate Student Seminars - Dick Casali and Kunal Kate

Date: Thursday, Mar 7th
Presenter: Dick Casali and Kunal Kate, OSU Materials Science


Dick Casali abstract:
Microelectronics: Lead Free Solder, Surface Finish and Fracture Toughness

Since 2006 consumer electronics companies have taken the lead out. Legislation has forced this change upon the industry. The consequences of this had been far reaching and spurred research into what makes a 'good' solder for electronics. Traditionally, eutectic SnPb had been used but now that Pb is effectively banned in certain geographies such as the EU, China and Japan, other solder formulations had to be utilized. The ternary alloy system most manufacturers are utilizing consist of SnAgCu (SAC). Literature has shown that ASTM E399 testing (Plane-strain fracture toughness) is an effective way to measure fracture toughness differences between solder alloys systems, including just changing the surface finish or protective coating over the solder. Surface finishes are used to prevent oxidation thus providing a longer shelf life for unassembled printed circuit boards (PCB). This allows the PCB to be made in high volumes in one place then assembled in another place, months after be fabricated. What effect does surface finish have? Is the surface finish play an important role in the metallurgical bond and therefore fracture toughness? Plans will be presented to help start answering these questions.

Kunal Kate abstract:
Models for predicting powder-polymer properties and their use in injection molding simulations of aluminum nitride

Powder injection molding (PIM) is widely used to manufacture complex-shaped ceramic and metal components in high production volumes. In order to design and fabricate PIM components, it is important to know a number of material properties at different powder- polymer compositions. In this research, several predictive models for estimating rheological, thermal and mechanical properties as a function of powder-polymer mixtures were evaluated using experimental data obtained from the literature. Based on this survey, models were selected for predicting rheological, thermal and mechanical properties for aluminum nitride-polymer mixtures at various volume fractions of powder using experimental measurements of unfilled and filled polymers. The material properties were estimated for two aluminum nitride powder-polymer mixtures and used in mold-filling simulations. These results will provide new perspectives and design tools for identifying useful material compositions, component geometry attributes, and process parameters while eliminating expensive and time-consuming trial-and-error practices prevalent in PIM.