| 摘要 |
<p>1,168,133. Thermistors. GENERAL ELECTRIC CO. 18 April, 1967 [19 April, 1966], No. 17692/67. Heading H1K. [Also in Division C1] A thermistor has two leads ohmically bonded to a doped synthetic single crystal diamond and displays a negative temperature coefficient of resistance of greater than 0.05 over a temperature range in excess of 500‹ C. The dopant may be boron, aluminium, or beryllium and may be incorporated (in the proportion of 0.001-1.0% by weight of diamond) during the nickel-iron catalysed conversion at 1100- 1700‹ C. and a pressure of 45-60 kilobars of graphite to diamond. 250-300Á diamonds are separated from residual graphite, catalyst, and pyrophyllite container material by respective treatments with sulphuric-nitric acid, hydrochloric-nitric acid, and dilute hydrofluoric acid. To make the thermistor of Fig. 1 (not shown), a degreased diamond (1) is placed in contact with degreased heat sink-lead assemblies consisting of iron-nickel-cobalt leads (4) welded to molybdenum or tungsten bodies (3) each coated with, for example, a palladium-nickel-chromium alloy (2). These parts were jigged with an alumino-silicate glass preform (5) in a gas-tight furnace containing oxygen-free forming gas of low dew point and heated to form ohmic con tacts and seal the assembly, the leads being pushed inwards during the process. An outer envelope (7) of devitrified glass is applied to protect the lead-heat sink welds. Oxide on the exposed portion of the leads is removed and the leads chromium-plated. Bonding alloys to replace the ternary alloy used are gold-nickelchromium, iron-nickel-cobalt, and palladiumnickel. The lead materials are tungsten, molybdenum, and the following materials which require no protective chromium coat:-platinum, palladium, and platinum-clad molybdenum. If leads are attached directly to the diamond, alloying, diffusion bonding, thermocompression bonding, ultrasonic welding, or nail-head bonding may be used. If headers are used bonding materials may be placed thereon by evaporation, as a slurry, or by firing-on an alloy preform. The atmosphere used in the firing stage and which is retained within the encapsulation, may instead be argon, helium, nitrogen or hydrogen, or the firing may be effected in vacuo.</p> |
