Impact of Die Attach Sample Preparation on Its Measured Mechanical Properties for MEMS Sensor Applications

Computational modeling is often leveraged to design and optimize electronic packages for both performance and reliability purposes. One of the factors that affect the accuracy of computational models is the accuracy of the material properties. Microelectromechanical system sensors, in particular, are usually extremely sensitive to slightest material property changes in the package. Therefore, even small measurement variations in material characterization due to different sample preparation methods or different testing techniques can impact accuracy of computational models that are leveraged for designing or analyzing sensor performance. The challenge in material characterization is even greater for materials that require curing. Die attach polymers, for example, have strict curing profile requirements that are used during the manufacturing process. Such curing conditions are usually hard to duplicate in laboratories, and the samples used for material characterization may not necessarily be representative of the actual component in the final product. In this study, the effect of parameters such as temperature curing profile, application of pressure during curing, and sample preparation technique on temperature-dependent thermomechanical properties of two types of die attach elastomers is investigated. The mechanical properties, including the elastic modulus (E), coefficient of thermal expansion, and glass transition temperature of the die attach material, are measured using a suite of techniques such as dynamic mechanical analysis and thermomechanical analysis. The analysis is performed for a wide temperature range corresponding to typical sensor applications. It is shown that sample preparation and characterization techniques have a considerable impact on the measurements, which results in different MEMS sensor performance predictions through computational modeling.