Semiconductor pressure transducer

Claim 1

A semiconductor pressure transducer comprising: a piezoresistive semiconductor diaphragm; a cylindrical stem made of a glass having a thermal expansion coefficient approximating that of said diaphragm, said diaphragm being hermetically bonded by anodic bonding to one side of said cylindrical stem; and a cylindrical holder for introducing a pressurized fluid to said diaphragm through said cylindrical glass stem, said cylindrical holder being hermetically bonded by anodic bonding at one end to the other side of said glass stem to support said glass stem; wherein said holder is made of a ferromagnetic alloy material having an austenitic structure and consisting essentially of Ni and Co, of which contents being within the range defined by a point A (Ni: 27.5%, Co: 16.5%), point B (Ni: 30.5%, Co: 16.5%), point C (Ni: 32.0%, Co: 11.5%) and a point D (Ni: 29.25%, Co: 11.5%) in FIG. 2, and the balance Fe, with at most small amounts of Si, Mn and C, said alloy material having been subjected to 30-90% cold working and stress relief annealing at 200°-600° C., and exhibiting a mean thermal expansion coefficient of 35×10 -7 /°C. or less over a temperature range between 30° C. and 350° C., whereby anodic bonding up to a temperature of 350° C. can be provided for bonding said cylindrical stem and cylindrical holder without breaking of the stem.