Glass-moulded type semiconductor device

Claim 1

A glass-moulded type semiconductor device comprising: a semiconductor arrangement composed of at least one semiconductor pellet having at least one P-N junction, edges of which are exposed to peripheral surfaces of the semiconductor pellet; a pair of electrodes secured to opposite ends of said semiconductor arrangement through a brazing material; a first mould glass layer secured to the entire circumferential surface of said semiconductor arrangement and extending to the surfaces of said electrodes for passivating the P-N junction of said semiconductor arrangement; and a second mould glas in the form of at least one layer secured to the surface of said first mould glass layer by sintering the second mould glass layer on the first mould glass layer after the first mould glass layer is formed, wherein said second mould glass layer has a thermal expansion coefficient sufficiently greater than the thermal expansion coefficient of the first mould glass layer so that after cooling said second mould glass layer following sintering a compressional pre-stress force is exerted by said second mould glass layer on said first mould glass layer, the thermal expansion coefficient of each of said mould glass layers being selected in such a manner that the thermal expansion coefficient of said first glass layer is larger than an apparent thermal expansion coefficient of a semiconductor assembly comprising said semiconductor arrangement and said brazing material, and wherein the thermal expansion coefficient of the second mould glass layer is set to be sufficiently greater than the thermal expansion coefficient of the first mould glass layer so that said compressional pre-stress force exerted by the second mould glass layer on the first mould glass layer will be sufficient to prevent breakage of the first and second mould glass layers during heating and expansion of the first mould glass layer when the semiconductor arrangement is in a conductive condition, said heating and expansion of the first mould glass layer being caused by the contacting relationship between the first mould glass layer and the semiconductor arrangement, and further wherein the difference in thermal expansion coefficients between said semiconductor assembly and said first mould glass layer is substantially not larger than 0.5×10 -6 /°C., and the difference in thermal expansion coefficients between said first and second mould glass layers is substantially in the range of 0.2×10 -6 /°C. to 0.5×10 -6 /°C.