DE2035767A1 - Electrical insulator with high thermal conductivity - Google Patents

Description

Patent attorneys

Dr.-ing. WiJlielin ßeichel
Kipl-Ing. Wolfgang ßolcliel

6 Frankfurt a. M. 1
Park street 13

GEIERAL ELECTRIC COMPANY, Schenectaäy, New York, V.St.A.

Electrical insulator with high thermal conductivity

The invention "relates to electrical insulating materials and Insulating body with high thermal conductivity.

Electrical insulating materials with high thermal conductivity have a wide range of applications. They are mainly used in semiconductor technology and are used there in many components and components, for example in the measuring and reference junction of thermocouples, in rectifiers, switching elements, etc. It is known that the heat loss in the current-carrying semiconductor components that are used in or operated above room temperature, the nominal operating values. This difficulty occurs in particular with semiconductor components that are to be operated with high powers. In order to remedy these disadvantages, it is known to use heat sinks. \ Thus, for example, for cooling a Silicifim-HaIbleiter.plättchensauf attach the back of the semiconductor device a heat sink serving as a heat exchanger and is gas- or liquid-cooled. Since the cooling body or ^T ärmeaustauscher generally consist // of a metal, it is necessary to insulate the semiconductor body from the metal heat sink electrically _ ^. This should, however, affect the heat conduction from the ο semiconductor to the heat sink as little as possible

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cp v / earth. It has therefore already been proposed electrically icolating separators with a relatively high V / poor * "** flexibility between the semiconductor body and the heat sink ta '. to be assigned. The separating body is made of ceramic bodies, which are in the ' y, containing essential beryl oxide, and made of diamond bodies' • manufactured. Leave the high cost associated with diamonds

however, commercial use is not permitted. The commercial . Use of beryl alumina or beryl oxide is also limited due to the toxicity of certain species. The detox these substances would also lead to high costs.

The object of the invention is to provide an insulating material or to find an insulating body that is cheap to manufacture on the one hand and to use and on the other hand has a thermal conductivity that is greater than that of the common today Insulating materials, for example from A ^ Oy. The thermal conductivity should, if possible, even be greater than the thermal conductivity made of commercially available stainless steel. Furthermore, the insulating body to be created should be made of a substance or a r-Iaterial exist that are both physically and chemically compatible with the semiconductor material and the heat sink material.

This object is achieved according to the invention in that the insulating material is a uniform or unitary body consisting essentially of aluminum nitride, that the density of the body is greater than about 80 % of the theoretical density of aluminum nitride, that the thermal conductivity at room temperature is greater than about 0.50 watt / cm and degrees Kelvin and that the electric
Centimeters.

and that the electrical specific resistance is more than 10 ohm

To compare the insulating material according to the invention with others The following table is used for materials; '

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- 3 - '.: ■■■■. '.. ■■ \ -:

Thermal conductivity (watt / cm ⁰ K)

- ■ ■
■
Material. -
Single crystal Polycrystalline diamond 27.0 ■. ■ ■. . Cu 4.0 BeO 3.T ■■ .- ■■ 2.6 to 3.1 Gd - - 0.8 Pt "'■■ /■'-.■ '■■ - ■; ■ -' ■■ '■ 0.7 Sn -; ■■ '■ - 0.65 Pb; , - 0.35 Al ₂ GJ (corundum) 0.35 about 0 * 3 Y ₂ O ₃ ;
Stainless steel
■ Type 3®4 0.27 0.15

As can be seen from the table, diamond has the greatest thermal conductivity. Siamonds are for commercial use but too expensive. Of the non-metallic materials has BeO excellent properties, namely a high V / thermal conductivity

and'an electrical specific. resistance of about 10 ohm centimeters, but is poisonous in solid form, what increases the "abration costs" of the metals Copper has a very high thermal conductivity, but like all other metals, too high an electrical conductivity for the stated purpose Conductivity. Type 304 austenitic stainless steel is both a poor conductor and proportionate good electrical conductor. The oxides suitable for coherent or bonded bodies, for example lieraraiken or G-Iasarten, almost all have one at room temperature -Thermal conductivity and an electrical specific

1Ö9 & O0 / 1375

Resistance whose values are equal to or less favorable than the corresponding values of aluminum earth or aluminum oxide. These values are about 0.3 watts / cm and ⁰ K or less and about 10 ¹⁰ to 10 ¹⁶ ohm centimeters.

Coherent bodies, which, however, essentially consist of single-phase ü-aluminum nitride powders (AlN) consist, have one, extremely A desirable combination of the properties mentioned if the density of the body is greater than 80 ^ "of the theoretical density . of aluminum nitride, although higher densities are preferable, and when made from a powder- which contains substantially more than 95 percent by weight AlN. The properties of single crystals made of AlN are even better.

Hot-pressed bodies, the density of which is almost 100 ⁰ Jo of the theoretical density, but which are made from commercially available powders that only have a minimal AlN content of. 94 percent by weight show, a thermal conductivity of only about 0.3 watt / cm and ⁰ K at room temperature or even less. Similar body, the density of 97 / is approximately cent of theoretical density, but which are made of single-phase powders containing about 99 weight percent AlN having a thermal conductivity of more than 0.6 Watt / cm, and ⁰ K at '"" room temperature. Single-phase powders can easily be determined by X-ray, fluorescence or diffraction analysis. A single crystal body made of AlN of medium purity even at room temperature has a thermal conductivity of 1 ', 95 watts / cra and ⁰ K. The electrical resistivity of -AlN is more than 10 ohm centimeters, a value that is completely sufficient for the purposes mentioned . -

109809/13 7S

Claims (5)

Patent claims Insulating body, aurch ge ke η η ζ eich η et,. that it consists of a uniform or unitary body, essentially containing aluminum nitride, that the density of the body is greater than 80% of the theoretical density of aluminum nitride, that the thermal conductivity at room temperature is greater than 0.5 watt / cm and ⁰ K. and that the electrical resistivity is more than 10 ohm centimeters. '- 2. Insulating body according to claim 1,. . dad ü roh ge k en η ζ e i c h net, that the body consists of several cohesively bonded particles which contain essentially single-phase aluminum nitride. 3. Insulating body according to claim 2,. · Thereby ge ken η ze i'c h'.n et,. that the particles contain at least 95% pure aluminum nitride. .-. ■■■■■■■ 4 »insulating body according to claim 1, since you rc Ia = ge ke η η ζ eic, h η et that the body ^ consists of several cohesive flocculated particles containing · ^M 'is substantially single phase Alumniumnitrid having a purity of at least 95 fo, that the body has a density of at least $ 95 of the theoretical density of;. ■■, -. Has aluminum nitride, and that the thermal conductivity at Room temperature is at least 0.6 watt / cm and K. 109809 / 137B 5. Insulating body according to claim 1, characterized, that the body is a single crystal of aluminum nitride, which has a thermal conductivity of at least 1.2 watt / cm · and ⁰ K at room temperature. HeLi / lo / 13tS