Patent ID: 7918962

Claim:
A method of manufacturing a rotation detector that comprises a semiconductor chip, a nonmagnetic case body, a biasing permanent magnet and a nonmagnetic cap fixed to the case body for accommodating therein the semiconductor chip and the biasing permanent magnet, wherein: the case body has a joint surface; and the cap has an inside surface in contact with the joint surface, the method comprising: assembling the semiconductor chip, the case body and the biasing permanent magnet into a unit; forming at least one groove adjacent to the joint surface so as to form a space between the joint surface and the inside surface when the cap is fixed to the case body; fixing the cap to the case body so that the inside surface of the cap can be in contact with the joint surface; irradiating a laser beam at portions behind the inside surface of the cap under a prescribed pressure to melt materials of the case body and the cap and to make melted materials flow to the space; filling the melted materials in the space under the prescribed pressure; stopping irradiation of the laser beam when the melted materials function to gradually stop reducing a height of the inside surface of the cap from the joint surface of the case body; and cooling the melted materials to re-crystallize.