Characterization of the Microstructure of Ceramics Used in Multilayer Ceramic Capacitors by Means of the Scanning Laser Acoustic Microscope

Analytical data obtained by the scanning laser acoustic microscope (SLAM) on multilayer ceramic capacitors can be correlated to microstructural elastic properties of the dielectric and electrode materials, to the quality of bonding between the layers, and to construction variables, such as materials thicknesses, number of layers, etc. These data can be used to build up predictive models of high-quality and poor-quality components, which is very important for nondestructive screening of high-reliability parts. Although SLAM screening of multilayer capacitors (such as specified in MIL-C-123) is quite straight forward and in current use for quality control, dilemmas can occur in which batches of nominally identical parts demonstrate widely different ultrasonic transmission and widely different SLAM images. These differences correspond to elastic property differences which may affect reliability. In this paper the authors discuss materials characterization aspects of acoustic microscopy as it pertains to multilayer ceramic capacitors. [Key words: capacitors, multilayer, ultrasonics, electrical properties, lasers.]