PURPOSE: To prevent any oxidation of the electrode structure or positional shift between the electrodes caused by thermal expansion or contraction by welding together the contact surfaces of the vertical peripheries of a lid and a metallic plate which is fixed to the peripheral end of a vacuum case to seal the airtight case.
CONSTITUTION: A metallic plate 5 is fixed to the peripheral end 1a of a vacuum case 1 by heating a frit glass 4 and the vacuum case 1 to 400W500°C. Next, after the vacuum case 1 to which the metallic plate 5 is fixed is cooled to ordinary temperature, an electrode structure 2 is installed in the vacuum case 1 through the opening of the metallic plate 5. After that, a lid 6 consisting of a metallic plate is attached to the opening of the metallic plate 5 and then the contact surfaces of facing vertical peripheries 5a and 6a are welded together by a laser welder 7. Therefore, the electrode structure 2 is assembled at ordinary temperature without being heated to high temperature. Accordingly, there is no possibility that various parts of the electrode structure 2 are exidized and that a shift is caused between the electrodes by thermal expansion or contraction.
YONEZAWA TAKETOSHI
WATANABE MASANORI
NONOMURA KINZO
TAKAHASHI MASAYUKI
