Patent GB-1130666-A (GB)
Title: A semiconductor device
IPC: H01L23/66
Filed: 1967-04-27
Abstract: 1,130,666. Semi-conductor device. NIPPON ELECTRIC CO. Ltd. 27 April, 1967 [30 Sept., 1966], No. 19508/67. Heading H1K. A semi-conductor device comprises a semiconductor element disposed in a substantially central recess on one side of a flat conductor member with one terminal connected thereto so that the conductor member serves as a common electrode for the device, there being a plurality of slots in the conductor member extending from the recess to its periphery with a signal conductor mounted in each slot and separated from the common conductor member by a dielectric layer, the signal conductors being connected to further respective terminals and the semiconductor element. As shown in Fig. 1a, the flat common conductor 13 is in the form of a disc having a diametrical slot cut part of the way through its thickness. A ceramic insulator, such as steatite, is laid in the base of the slot and flat strip conductors 11 and 12 of oxygen-free copper are arranged within the slot as shown. A diffused transistor pellet is disposed upon the inner end of the conductor 12, the portion of the slot surrounding the pellet serving as the substantially central recess. The arrangement of the transistor pellet on the conductor is illustrated in Fig. 2 (not shown). The collector electrode is connected directly to the conductor 12 and the emitter and base electrodes are connected by thin gold or aluminium wires using thermal pressure bonding, to the strip conductor 11 and to the common conductor 13 respectively. The strip conductors 11 and 12 may be bonded to the ceramic dielectric by means of a thin layer of soda glass. In order to facilitate the electrical connection to the transistor electrodes the conductors 11, 12 and 13 are preferably coated with a thin gold layer. An extension 19 from the common conductor serves as the emitter lead and a further thin conducting layer (16), Fig. 1b (not shown), may be arranged on the underside of the conductor 13 and spaced therefrom by a thin insulating layer (15), with an extension 20 therefrom serving as a separate D.C. earthing conductor. The upper surface of the device may be hermetically sealed by a ceramic, Fig. 3 (not shown) or metal, Fig. 4 (not shown), cover. Alternatively the device may be sealed in a casting resin. The device is especially designed for use at the highest operating frequencies, the conductors 11 and 12 in conjunction with the common conductor 13 functioning as strip lines whose impedances are appropriately matched both to the transistor element and to the external circuit. The construction provides excellent electrostatic screening of the conductors 11 and 12 from each other and of the transistor element from the external circuit; electromagnetic screening may also be provided by making the conductor 13 of a high-permeability material. The conductor 13 also serves as a heat sink. Fig. 5 shows an alternative embodiment in which a semi-conductor integrated-circuit element 51 is disposed in a recess in a common conductor 53 with its common electrode electrically connected thereto. Lead-out conductors 56, connected to the element 51 by wires 59, are mounted on dielectric layers 55 bonded to the bottom of slots 54 in the common conductor. A ground or earth conductor 58 is spaced from the underside of the common conductor by a dielectrc layer 57. The slots can be sealed with an air-tight sealing medium and the complete structure may then be sealed with a metallic lid which also completes the electrical shielding. Radiator fins may be bonded or soldered to the earth conductor. The invention may be applied to field-effect transistors as well as to bi-polar transistors and integrated circuits.