Patent ID: 8818010
Filing Date: 2014-08-26
Classification: H04R

Abstract:
1. A microphone unit comprising: a base board; an electrically conductive layer formed on a first surface of the base board; and a transducer that is mounted on the base board, includes a diaphragm, and transduces a sound pressure into an electrical signal, wherein a coefficient of thermal expansion of the diaphragm is larger than a coefficient of thermal expansion of the base board and is smaller than a coefficient of thermal expansion of the electrically conductive layer, and a coefficient β of thermal expansion of the combination of the base board and the electrically conductive layer given by the following formula is in a range 0.8 to 2.5 times as large as the coefficient of thermal expansion of the diaphragm: where: a is the coefficient of thermal expansion of the base board, b is the coefficient of thermal expansion of the electrically conductive layer, x is a thickness of the base board, y is a thickness of the electrically conductive layer, and r is a formation area ratio of the electrically conductive layer.