| 摘要 |
PURPOSE: To form a uniform gap all over the core block after glass welding with little stress which is easily introduced into a soft magnetic material by specifying the range of warpage on the back surface of a substrate, difference in thickness between the front and back surfaces of the substrate of one core block, and difference in the thermal expansion coefft. from room temp. to transition temp. of the glass. CONSTITUTION: The difference in thickness between the center part and the edge part of a substrate 1 of a half core block before held between and joined with a nonmagnetic gap material is specified to <=0.5μm. Further, warpage on the back surface of the substrate 1 is always controlled to be concave with about 0.5-1μm depth so that the warpage on the back surface matches the warpage on the top surface. The glass used to always obtain concave warpage with <=1μm depth of the back surface of the substrate is a low melting point glass 3 the coefft. of thermal expansion of which from room temp. to the transition temp. is lower than the coefft. of thermal expansion of the substrate by <=10×10<-7> / deg.C.
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