Effects of Ferroelectric Properties on Mechanical Behavior of Class II Multilayer Ceramic Capacitors

Abstract

Class II Multilayer Ceramic Capacitors (MLCCs) are one of the most widely adopted types of passive components in modern electronic systems due to their high volumetric efficiency. Mechanical failures are dominant in MLCCs due to the brittle nature of the ceramic dielectric. Over the years, there have been many studies on the effect of design parameters, assembly parameters on crack susceptibility of these parts. Barium Titanate (BaTiO3) based ceramic is used as the dielectric in Class II MLCCs. This material is responsible for capacitance aging and temperature dependent properties in these units. Changes in mechanical properties due to electrical and mechanical loading or loading history is widely reported in the literature for bulk BaTiO3 and other ferroelectric materials. However, these effects have yet to be reported for Class II MLCCs components in the literature. With the indentation technique becoming more popular in research and development, more studies have adopted the technique for assessing mechanical properties of MLCCs and other electronic components. However, indentation measured properties are dependent on test parameters. In the case of ferroelectric materials, the properties also depend on texture of the specimen and other electromechanical coupling effects. In this study, baseline measurements of mechanical properties under various test parameters as well as treatment history of MLCCs are established using the Oliver-Pharr method. Two mechanisms are evaluated for the potential change in flexural strength for MLCCs with DC voltage history. The first one is the fracture toughness anisotropy caused by domain switching. The second one is the change in stress distribution in the MLCC body with the increase in effective dielectric texture (crystallinity) due to poling under a bending load. Finally, flexural strength is measured for commercial MLCCs with different volumetric ratio of effective dielectric, and an empirical relationship is developed to relate the change in flexural strength to the applied poling voltage and the volumetric ratio of the tested units.