TDK's small and thin SMD type electromagnetic buzzers provide high sound pressure, compactness and reliability. TDK has adopted a liquid crystal polymer with high heatproof properties in the housing component of the SDR series. To support the diaphragm, metallic rings are now used instead of conventional resin materials to make the structure solid so that it is no longer affected by thermal expansion at reflow process temperature. Also, highly reliable epoxy adhesives and ultrasonic welding is applied to joints of individual parts. These improvements have allowed TDK to provide a small size of 8.5 mm square with a height of 4 mm and a high sound pressure.