| 摘要 |
PURPOSE:To enable an exact measurement of a thickness of a diaphragm plate in a noncontact manner and to prevent the reduction in mechanical strength without the damage to the diaphragm. CONSTITUTION:Concavities 16A-16I, having an angle theta, are formed in a main surface of a water by etching using an etching liquid whose main component is KOH (mercury kalium). This is an anistoropic etching, and a surface 15 is two digits or more slower in an etching rate as compared with surfaces 16 and 17, which is utilized to form the surface 15 as shown in a drawing and to form it into a quadrangular pyramid resulting from etching. A diaphragm part 2 is formed by etching a surface (back surface), being opposite to the main surface, with the etching liquid whose main component is KOH, and a recess 15, having a width H, is also formed by etching. This enables an accurate measuring of a plate thickness of a diaphragm 2 in a noncontact manner and prevents the reduction in mechanical strength. |
