Patent attributes
A stem package with good high frequency characteristics for high-speed transmission at 10 Gbps and higher includes a stem which has an under surface, an upper surface and one or more through holes penetrating from the upper surface to the under surface, a mount for mounting, with an optical semiconductor device, on the upper surface, a lead terminal for signal supply penetrating one of the through holes with an insulator between the stem and the lead terminal, the upper surface having an earth conductor adjacent to the lead terminal for signal supply and Projecting from the upper surface so that a difference between the characteristic impedance of the transmission line constituted by the through hole, the insulator, and the lead terminal for signal supply and the characteristic impedance of the transmission line constituted by a lead terminal for signal supply projecting from the upper surface is small.
