JPH03257077A - Insulating substrate having high radiation of heat and its production - Google Patents

Abstract

PURPOSE:To obtain the title insulating substrate having high bonding strength, inhibiting the generation of thermal stress and not causing the peeling and cracking of the joined part by joining a metallic Mo or Mo alloy sheet to a ceramic substrate with a ceramic layer in-between. CONSTITUTION:The surface of a ceramic substrate 1 having high heat conductivity is coated with a ceramic layer 2 different from the substrate 1 in compsn., a metallic Mo or Mo alloy sheet 3 is put on the ceramic layer 2 and they are heated to a temp. above the melting temp. of the layer 2. The layer 2 is then solidified by cooling and an insulating substrate having high radiation of heat is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high heat dissipation insulating substrate in which a metal plate is bonded to a substrate made of highly thermally conductive ceramics, and a method for manufacturing the same.

[Prior Art] Conventionally, in order to use a highly thermally conductive insulating substrate as a power module substrate, a Cu circuit board has been attached to an Al2O3 substrate.

In particular, techniques for directly bonding Cu to an Al2O3 substrate and techniques for bonding via an active metal have been put into practical use. The technique of bonding Cu circuit boards through active metals is Ti, Z
A metal layer containing a highly active metal such as R is formed on the surface of a ceramic member, a Cu circuit board is placed on top of the metal layer, and the Cu circuit board is heated and bonded.
This has been achieved by active metals such as

[Problems to be Solved by the Invention] However, in all of the above conventional methods of attaching a CU circuit board to an Al2O3 substrate, since there is a large difference in the coefficient of thermal expansion between Al2O3 and Cu (see the table below), During cooling, thermal stress is generated, which makes it easier for joints to peel or crack. Therefore, there was a problem that the reliability of the product was low.

In addition, as the capacity of transistors has increased in recent years,
Good heat dissipation from the substrate has become an even more important factor, and highly thermally conductive non-oxide substrates such as SiC and AIN are being adopted. These non-oxide-based substrates have a smaller coefficient of thermal expansion than Al2O3.
(See the table below), adhesion to the Cu plate is even more difficult.

Additionally, the method of bonding an Al2O3 substrate and a Cu circuit board via an active metal requires the work to be carried out in a vacuum atmosphere, which has the problems of low productivity and unstable adhesive strength. .

In view of the above conventional problems, the present invention has high thermal conductivity,
The present invention aims to provide a highly reliable heat dissipation insulating substrate suitable for large current circuits and a method for manufacturing the same.

[Means for Solving the Problems] The high heat dissipation insulating substrate of the present invention includes a substrate made of highly thermally conductive ceramic, and a ceramic made of a material different from that of the substrate, which is coated on the surface of the substrate. A metal plate made of molybdenum alone or an alloy containing molybdenum is bonded thereon using the ceramic layer as an adhesive layer.

Further, the method for manufacturing a high heat dissipation insulating substrate of the present invention includes a step of coating a ceramic layer of a material different from that of the substrate on a part or the entire surface of a substrate made of highly insulating ceramic; A metal plate made of molybdenum alone or an alloy containing molybdenum is placed on top of the layer, and in that state, the substrate and metal are heated to a temperature higher than the melting temperature of the ceramic layer, and then cooled to solidify the ceramic layer. This process consists of the step of adhesively fixing the plates.

Ceramics with high thermal conductivity forming the substrate used in the present invention include AA'203. SiC.

AA'N, Si3N4, etc. are used, and in addition to these, MgO, Si02, Al103 are used as sintering aids.
, Y2O3, CaO, etc. This sintering aid is
AA'203. By adding a small amount to ceramics such as SiC, AIN, Si3N4, etc., it has the effect of promoting sintering and obtaining dense ceramics. As the material of the ceramic layer forming the adhesive layer between the substrate and the metal plate, high melting point glass, active metal-containing glass, active metal-containing ceramic, etc. are used. Additionally, the melting time of the ceramic layer when bonding metal plates is generally 400
It is carried out in a non-oxidizing atmosphere at a temperature between 1200°C and 1200°C.

As a method for forming the ceramic layer, known methods such as screen printing, dip coating, and brush coating can be used. The metal plate may be bonded to the substrate and then etched to form a circuit, or it may be processed into a circuit board by etching or punching in advance and then bonded to the substrate.

Note that the surface of the metal plate is protected by applying nickel plating or the like.

[Function] In the high heat dissipation insulating substrate of the present invention, the metal plate is made of molybdenum alone or an alloy containing molybdenum, and its coefficient of thermal expansion is relatively close to that of the ceramics forming the substrate such as AIN, so that it can be used after heat bonding in the manufacturing process. The thermal stress generated during cooling is extremely small.

In addition, since the components of the ceramic layer serving as the adhesive layer easily adhere to both the metal plate and the substrate, a good bonding state between the metal plate and the substrate can be obtained. Furthermore, it is considered that the ceramic layer absorbs the difference in coefficient of thermal expansion between the substrate and the metal layer and suppresses the occurrence of negative layer thermal stress.

[Example] Examples of the present invention are shown below. The bonding strength of the insulating substrates in each example was evaluated as shown in FIG. 2. In other words, A as a ceramic substrate
A thickness of approximately 10 μm (δ shown in FIG. 2) is formed on the IN substrate 11.
A ceramic layer 12 is formed in the thickness (t shown in FIG. 2).
Approximately 0. 2mm.

Metal plates 13 with a width (W shown in Fig. 2) of about 10 mm are bonded and fixed as shown in Fig. 2, and when pulled up with force F in the direction of the arrow, the value of force F at which the joint starts to peel off is determined by the value of force F. evaluated.

(Example 1) AIN containing 2.0% by weight of Y2O3 as a sintering aid
Board (dimensions: height 30mm, width 30mm.

(thickness 0.6 mm) on top of Na2O・P2O3・5i0
2 series glass (melting point = 700°C) was applied to a thickness of 10 μm by screen printing method, and after drying, Mo plate (
A film (thickness: 0.2 mm) was placed thereon and heated at 1000° C. in an Ar atmosphere. After cooling, a bonding strength test shown in FIG. 2 was conducted, and the force F at which the bonded portion began to peel was 10 kg.

(Example 2) AI containing 8.0% by weight of Y2O3 as a sintering aid
N substrate (thermal conductivity: 160W/mk, dimensions: length 3Qm
m, width 30mm, thickness 0.6mm) in the atmosphere.
When heated at 100℃ for 10 minutes: 10% on the surface of the filter AIN.
A μm thick Al2O3/Y2O3 layer was formed.

Mo plates (dimensions: length 28 mm) were placed on both sides of the obtained AIN board.
, width 28 mm, thickness 0.5 mm) was heated to 1200°C in an N2 atmosphere, and the AIN substrate and M
Both sides of the o-plate were firmly joined. When the insulating substrate thus formed was subjected to a bonding strength test shown in Figure 2, the force F at which the bonded portion began to peel was 5k.
It was g.

(Example 3) It was found that it was possible to join the NO plate in the same manner as in Example 2 with respect to a Si3N4 sintered body containing 5% by weight of Al2O3 and 5% by weight of Y2O3 as sintering aids.

A heat cycle test between -50°C and 120°C was carried out for 500 cycles on the obtained joined body.
There was no loss in bonding strength after that, and when the bonding strength test shown in FIG. 2 was conducted after the heat cycle, the force F at which the bonded portion began to peel was 6 kg.

(Comparative example) As a comparative example, C was deposited on an Al2O3 substrate through a Ti layer.
When the bonding strength test shown in FIG. 2 was similarly conducted on a conventional insulating substrate to which U-plates were heat-bonded, the F at which the bonded portion began to peel was 4 kg.

(Example 4) As shown in FIG. 3, one of the ceramic layers of Examples 1 to 3 described above is formed on the outer periphery near the end of a cylindrical AIN substrate 21, and a cylindrical Mo plate 23 is heat-bonded. electron tube outer tube 2
4, it was possible to achieve a good hermetic seal.

[Effects of the Invention] As explained above, according to the present invention, since a metal plate made of molybdenum alone or an alloy containing molybdenum is bonded to a substrate via a ceramic layer, the bonding force is strong and thermal stress does not occur. It is possible to obtain a high heat dissipation insulating substrate in which the heat dissipation is significantly suppressed and peeling or cracking does not occur at the bonded portion.

Therefore, it is possible to provide a high heat dissipation insulating substrate on which a highly reliable circuit for large currents can be formed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the schematic structure of the high heat dissipation insulating substrate of the present invention, FIG. 2 is a diagram showing a method for evaluating the bonding strength of the high heat dissipation insulating substrate in each embodiment of the present invention, and FIG. 3 is the present invention. FIG. 2 is a cross-sectional view showing the structure of an electron tube envelope to which the method is applied. In the figure, 1 is a substrate, 2 is a ceramic layer, and 3 is a metal plate. Patent issuer Sumitomo Electric Industries, Ltd.

Claims (2)

[Claims] (1) A substrate made of highly thermally conductive ceramics, a ceramic layer made of a material different from that of the substrate that is coated on the surface of this substrate, and this ceramic layer used as an adhesive layer to stick on top of it. A high heat dissipation insulating substrate consisting of a metal plate made of molybdenum alone or an alloy containing molybdenum. (2) A process of coating a ceramic layer of a material different from the material of the substrate on a part or the entire surface of a substrate made of highly thermally conductive ceramics, and coating molybdenum alone or molybdenum on this ceramic layer. a step of stacking metal plates made of an alloy containing the metal alloy and heating the metal plates in this state to a temperature higher than the melting temperature of the ceramic layer; and a step of adhesively fixing the substrate and the metal plate by cooling and solidifying the ceramic layer. A method for manufacturing a high heat dissipation insulating substrate consisting of.