JPH06329480A - Joined body of ceramics and metal and its production - Google Patents

Abstract

PURPOSE:To prevent release of a metal from a ceramic sintered body and the occurrence of crack which is caused by change of temperature, by laminating metal bodies through a specific metal layer formed on the surface of the ceramic sintered body. CONSTITUTION:A mixture of at least two or more kinds containing a high melting metal and a silver-copper-based alloy and different in a ratio of high melting metal content of silver-copper-based alloy content is laminated on at least a part of the surface of a ceramic sintered compact 10 in the order of the larger content ratio to provide metal layers 22a to 22c. Then, a metallic body 16 is positioned in a state brought into contact with the surface on the opposite side of the ceramic sintered body having these metallic layers 22a to 22c, and then, heat-treated in the presence of an active metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-metal bonded body and a method for manufacturing the same.

[0002]

2. Description of the Related Art Ceramic sintered bodies such as alumina, silicon nitride and aluminum nitride are widely used for semiconductor substrates, automobile parts and the like because they are excellent in heat resistance, wear resistance and insulation. There are cases in which heat dissipation is required together with power modules, engine parts, rocket outer wall materials, etc., but ceramic sintered bodies generally have poor thermal conductivity, so in such cases A ceramic-metal bonded body is used, which is bonded to a metal having excellent thermal conductivity (such as copper) to improve heat dissipation. Examples of the joining method include a method in which a metal body is brazed to a ceramic sintered body using silver solder or the like, and JP-B-57-135.
As disclosed in Japanese Patent Publication No. 15, there is a method in which a ceramic sintered body is placed in contact with a metal body and bonded by a eutectic reaction in a predetermined atmosphere.

[0003]

However, while the coefficient of thermal expansion of a general ceramic sintered body is about 3 to 10 × 10 ⁻⁶ / ° C., the coefficient of thermal expansion of metals such as copper and stainless steel is used. Is as large as 16 to 18 × 10 ^-6 / ° C. Therefore, in such a ceramic-metal bonded body, since the thermal expansion coefficients of the two bonded are largely different, stress (thermal stress) caused by the difference in the thermal expansion coefficient is generated due to the temperature change during the bonding process or during use. However, peeling may occur at the bonding interface, or cracks (cracks, cracks, etc.) may occur when the strength of the ceramic sintered body is lower than the thermal stress. Therefore,
At the joint interface between the ceramic sintered body and the metal, a cushioning material having a coefficient of thermal expansion intermediate between the two and a ductility that absorbs thermal stress as disclosed in JP-A-56-41879 by plastic deformation are excellent. Although a method of inserting a cushioning material or the like is performed, in the former method, since there is a considerable difference in the coefficient of thermal expansion between the cushioning material and the ceramic sintered body, thermal stress caused by it is generated. The latter method has a problem that the stress cannot be sufficiently absorbed by the plastic deformation of the cushioning material when the generated thermal stress is extremely large.

The present invention has been made in view of the above circumstances, and its object is to solve the problems such as the separation of the metal from the ceramic sintered body and the generation of cracks in the ceramic sintered body due to the temperature change. It is to provide a ceramics-metal bonded body which can be suitably solved.

[0005]

[Means for Solving the Problems] To achieve the above object, the gist of the present invention is to provide a ceramic sintered body and at least a part of the surface of the ceramic sintered body. Including a formed metal layer and a metal body bonded to the ceramic sintered body through the metal layer-
A metal joined body, wherein the metal layer contains a refractory metal, a silver-copper alloy, and an active metal, and the ratio of the content of the refractory metal to the content of the silver-copper alloy is the above. The ceramic sintered body is reduced in size continuously or stepwise with increasing distance from the surface.

[0006]

In this way, the metal layer formed on the ceramic sintered body is made of titanium (Ti),
Since the active metal such as Nb, Hf, and Zr is contained, the active metal diffuses in the vicinity of the interface when the ceramic sintered body and the metal body are bonded, so that the two are firmly bonded and the metal layer is The ratio of the content of the refractory metal to the content of the silver-copper alloy is reduced continuously or stepwise as the distance from the surface of the ceramic sintered body is reduced. It is made relatively small on the sintered body side and made relatively large on the opposite side. This is because the refractory metal such as tungsten and molybdenum has a small coefficient of thermal expansion of about 5 × 10 ⁻⁶ / ° C., while the silver-copper alloy has a large coefficient of thermal expansion of 16 to 18 × 10 ⁻⁶ / ° C. Therefore, the coefficient of thermal expansion of the metal layer is determined to be an intermediate value between the coefficients of thermal expansion according to the ratio of the content rates of the two. Therefore, at the bonding interface between the ceramic sintered body and the metal body, the difference in the coefficient of thermal expansion at the interface between the respective metal layers becomes small, and when the temperature changes, the thermal stress caused by the difference becomes small. Peeling and cracking of the ceramic sintered body are preferably eliminated. Furthermore, since the metal body is bonded to the ceramic sintered body through a metal layer, heat generated on the side of the ceramic sintered body is preferably dissipated by the bonded metal body, and a semiconductor substrate or an engine component, It is suitable for parts that require heat dissipation as well as insulation and heat resistance such as rocket outer wall materials.

[0007] Preferably, the metal body is bonded to the metal layer via the silver-copper alloy layer. Since such a ceramics-metal bonded body has good wettability between the copper plate and the silver-copper alloy during bonding, sufficient bonding strength can be obtained, and good thermal conductivity and high durability can be obtained. .

Also, preferably, the ceramic sintered body is a substrate, and the metal body is a copper plate or a copper alloy plate.
When the ceramic substrate having such a structure is used in a power module, a semiconductor module for a piezoelectric element, or the like, heat generated in a semiconductor or electronic component is dissipated by a metal body, and the temperature of the semiconductor and the substrate is increased. In addition to being suitably relaxed, peeling and cracking do not occur even when a temperature change occurs as described above, and it is suitable as a substrate for semiconductors, electronic components, etc. used at high temperatures.

Also, preferably, in the ceramic substrate, a circuit pattern is formed on at least a part of a copper plate or a copper alloy plate. Such a ceramic substrate is
A high-reliability ceramic circuit board can be obtained which can handle a large current and does not peel off the circuit pattern when a temperature change occurs.

Also, preferably, the ceramic sintered body is an alumina sintered body or an aluminum nitride sintered body. Such a ceramic-metal bonded body has thermal conductivity,
Since it is particularly excellent in insulating properties and mechanical properties, it is particularly suitable for substrates such as semiconductors and electronic parts as described above.

[0011]

A second aspect of the present invention is directed to a method for producing a ceramic-metal bonded body according to the present invention, which contains a refractory metal and a silver-copper alloy, and contains a refractory metal. Using a mixture of at least two or more different ratios to the content ratio of the silver-copper-based alloy, on the surface of at least a portion of the ceramic sintered body, a laminating step of forming a mixture layer in descending order of the ratio, It is to include a step of positioning the metal body in contact with the surface of the mixture layer opposite to the ceramic sintered body, and a heating step of performing heat treatment in the presence of an active metal.

[0012]

In this way, by stacking a predetermined type of mixture on the ceramic sintered body for a predetermined number of times, silver having a high melting point metal content is added as the distance from the surface of the ceramic sintered body increases. A mixture layer with a reduced proportion to the copper-based alloy content is obtained. Therefore, by performing heat treatment in the presence of an active metal, the active metal diffuses into the mixture layer to firmly bond the ceramic sintered body and the metal body, and the metal layer is formed of a refractory metal and silver. -A copper-based alloy and an active metal, and the ratio of the content of the refractory metal in the metal layer to the content of the silver-copper-based alloy is continuous or stepwise as the distance from the surface of the ceramic sintered body increases. It is possible to easily obtain a ceramic-metal bonded body which is made extremely small.

[0013] Preferably, the active metal is contained in the mixture layer formed by the laminating step or is laminated outside the mixture layer. In this way, when heated, the active metal easily diffuses in the mixture layer,
Can reach the surface of the ceramic sintered body and the surface of the metal body,
The silver-copper alloy and the active metal firmly bond the two.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a process flow chart of the present invention. For example, in a silver-copper-titanium mixed powder (average particle size: 1.2 μm, copper: 1.3 μm, titanium: 20 μm) having compositions No. 1 to No. 9 in Table 1, tungsten powder (grains). Diameter 2.4 μm) and the weight ratio thereof is, for example, A: 60%, B:
40%, C: 20% so that a total of 27 kinds of mixture raw materials are prepared, for example, an auxiliary agent having ethyl cellulose and terpineol as main components is added, and the mixture paste is kneaded with, for example, a three-roll mill. A _{1 to} A ₉ , B ₁ to
To produce a B _9, C ₁ ~C _9. In this embodiment, titanium corresponds to the active metal and tungsten corresponds to the refractory metal.

[0016]

[Table 1]

Next, separately prepared, for example, 50 × 33 ×
Alumina substrate with a size of 0.6 mm (sintered body: Al ₂ O ₃
96%, the balance CaO, MgO, SiO ₂ and a trace amount of unavoidable impurities) 10 on both sides of the mixture paste A ₁ ~
A ₉ , B _{1 to} B ₉ , and C _{1 to} C ₉ are a combination of the same subscripts (for example, A ₁ , B ₁ and C ₁ ), A, B,
After printing with a thickness of, for example, about 20 μm in the order of C, the operation of drying, for example, at about 130 ° C. was repeated to obtain 9 types of printed boards 14 having the printing layer 12 formed on both sides as shown in FIG. The printed layer 12 is composed of three layers (12a, 12b, 12c) of a predetermined thickness corresponding to the mixture pastes A, B, C, respectively, as shown in a partial cross section in FIG. A predetermined circuit pattern is formed on one surface (the upper surface in FIG. 2) of the substrate 14. Further, since the print layer 12 has the same cross-sectional structure on both sides, FIG. 3 shows only the structure on one side. Next, these printed boards 14 are degreased at 600 ° C. in an N ₂ atmosphere, for example, and each of them has a thickness of, for example, 300 on the printed layers 12 on both sides of the printed board 14.
Oxygen-free copper plates 16 and 18 of μm and 350 μm are placed, a load of, for example, 0.3 g / mm ² is applied through a spacer, and the temperature is set to 2 at 850 ° C. in a vacuum of 5 × 10 ⁻⁵ torr.
Heat treatment was performed for 0 minutes to obtain an alumina-bonded substrate 20 having copper plates bonded to both surfaces as shown in FIG. In this example, the alumina substrate 10 corresponds to the ceramic sintered body, the printed layer 12 corresponds to the mixture layer, and the active metal is contained in the mixture layer.

These alumina-bonded substrates 20 have a metal layer 2 corresponding to the printed layer 12 on both sides of the alumina substrate 10.
The copper plates 16 and 18 are bonded to each other via the metal layer 2
2 is a printing layer 12a, 1 as shown in FIG.
It is composed of three layers 22a, 22b and 22c corresponding to 2b and 12c, and the amount of tungsten particles 26 in the silver-copper alloy 24 containing titanium is large on the alumina substrate 10 side and small on the copper plate 16 side. It has a structure dispersed in. That is, in the metal layer 22, the ratio of the content rate of tungsten to the content rate of the silver-copper alloy is
The diameter is gradually reduced as the distance from the surface of the alumina substrate 10 increases.

The peel strength of the alumina-bonded substrate 20 and the alumina-bonded substrate of the same shape in which a copper plate was bonded by a conventional silver brazing or Cu-O eutectic reaction was measured. 14 kg / c for both
In contrast, the strength of the conventional alumina bonded substrate was 8 kg / cm. In the peel strength test, a tensile terminal was bonded to the alumina bonding substrate 20, the copper plate 16 or 18 was peeled off with a tensile tester in the direction of 90 ° with respect to the alumina substrate 10, and the load when peeled off was measured. It is what I asked for.

Further, in order to evaluate the thermal shock resistance of the alumina-bonded substrate 20, a series of steps of holding at −50 ° C. for 30 minutes in the thermal shock tester, heating to 150 ° C. and holding for 30 minutes is one cycle. The test was repeated. The temperature was adjusted very quickly by sending cold or hot air into the tester. As a result, the alumina bonded substrate 2
No cracking or peeling was observed even after 500 cycles. On the other hand, the alumina-bonded substrate produced by the above-described conventional method that was simultaneously subjected to the test showed cracks after about 50 cycles. From the above-mentioned tests, the alumina-bonded substrate 20 of the present example has a bonding strength. Strong again
It was shown to have sufficient durability against temperature changes (temperature cycle).

That is, the metal layer 22 formed on the alumina substrate 10 and the layer 22a on the alumina substrate 10 side have a high tungsten content and a low coefficient of thermal expansion, and the copper plates 16 and 18 are provided.
The side layer 22c has a low tungsten content and a high thermal expansion coefficient, and the intermediate layer 22b has an intermediate tungsten content rate and an intermediate thermal expansion coefficient.
Since the silver-copper alloy content increases as the distance from the alumina substrate 10 increases, that is, the coefficient of thermal expansion increases, the difference in the coefficient of thermal expansion between the copper plates 16 and 18 and the alumina substrate 10 is caused by the metal layer 22. It is absorbed and thermal stress caused by it is hardly generated. For this reason, residual thermal stress (residual stress) due to heating / cooling when joining the copper plates 16 and 18 becomes small, and high joining strength can be obtained as described above, and cracks and peeling are prevented even if temperature changes occur. Thus, the alumina bonded substrate 20 that does not generate is obtained.

Further, since the alumina-bonded substrate 20 has a copper plate 18 as a heat dissipation plate bonded to one surface thereof, when it is used as a substrate for a power module or the like which generates a large amount of heat,
The heat generated in the semiconductor is suitably dissipated by the copper plate 18, and high durability and reliability are obtained. This is a copper plate 1
8 and the alumina substrate 10 serve as a bonding layer for the metal layer 2
No. 2 is formed of a relatively dense layer made of tungsten and a silver-copper alloy, and has good heat conduction, and as described above, thermal stress is reduced, so that peeling and cracks are less likely to occur. This is because.

Further, using a mixture paste in which the mixing ratio of the silver-copper-titanium mixed powder and the tungsten powder is changed,
Since the printing layer 12 having a three-layer structure is formed by printing and stacking, by firing the metal layer, the ratio of the content ratio of tungsten to the content ratio of silver-copper alloy decreases as the distance from the alumina substrate 10 increases. 22 is easily obtained. At this time, since the mixture paste to be printed contains titanium, this titanium is diffused in the metal layer and acts as an active metal, and the alumina substrate 10 and the copper plate 1
6 and 18 are firmly joined.

Further, since the copper plates 16 and 18 having the same size and shape are bonded to both surfaces of the alumina substrate 10, the same degree of thermal stress is generated on both surfaces to cancel each other when the temperature changes. The alumina bonded substrate 20 having high durability against temperature changes is obtained.

Further, in this embodiment, since the ceramic sintered body is the alumina substrate 10, it is excellent in mechanical properties, thermal conductivity and insulation properties, and is suitable as a substrate used for a power module or the like.

An oxygen-free copper plate 1 is used as the metal body to be joined.
Since 6 and 18 are used, the wettability between the copper plate and the brazing material is good, and there is no reduction in the activity of the active metal due to the reaction between the active metal in the brazing material and oxygen in the copper plate. ,
A strong joined body of the copper plate and the ceramic sintered body can be obtained.

Next, another embodiment of the present invention will be described.

For example, using a silver-copper-titanium mixed powder having the No. 1 composition in Table 1 and molybdenum powder (particle size 2.6 μm), the weight ratio of molybdenum powder is, for example, 50%, respectively.
Two kinds of 25% mixture raw materials were prepared, for example, an auxiliary agent containing ethyl cellulose and terpineol as main components was added, and the mixture paste was kneaded with, for example, a three-roll mill to prepare mixture pastes D and E. Furthermore, silver-copper brazing filler metal pastes F _{1 to} F ₁₃ were prepared in the same manner as the mixed paste from the mixed powders having the compositions of No. 10 to No. 22 in Table 1. In this example, molybdenum corresponds to the refractory metal.

Next, several separately prepared sheets, for example, 50 × 3
The mixture pastes D and E are sequentially printed with a thickness of, for example, about 30 μm on both surfaces of an aluminum nitride substrate having a size of 3 × 0.6 mm (sintered body: 96% by weight of AlN, balance Y ₂ O ₃ and trace amount of unavoidable impurities). After that, the operation of drying at, for example, 130 ° C. is repeated, and any one of the silver-copper brazing filler metal pastes F _{1 to} F ₁₃ is further applied thereon, for example, about 15
By printing with a thickness of μm, 13 kinds of printed boards similar to the printed board 14 shown in FIG. 2 were obtained. The printed layers of these printed boards have the same structure as that of the first embodiment, and a circuit pattern is formed on one surface thereof. Further, an oxygen-free copper plate was bonded to both sides of the aluminum nitride substrate by the same method as in the first example to obtain an aluminum nitride bonded substrate 28 having the same shape as the alumina bonded substrate shown in FIG.

The metal layer 30 of the aluminum nitride bonded substrate 28 is a layer 30 containing molybdenum, which corresponds to the pastes D, E and F, as shown in a partial cross section in FIG.
a, 30b and a layer 30c containing no molybdenum, and therefore the molybdenum particles 32
The ratio of the content ratio of the above to the content ratio of the silver-copper alloy 34 is gradually reduced as the distance from the surface of the aluminum nitride substrate 36 is increased, and the layer closest to the copper plate 38 becomes a molybdenum-free silver-copper alloy layer. ing. The aluminum nitride substrate 36 corresponds to a ceramic sintered body in the present invention.

Here, the aluminum nitride bonded substrate 28
The peel strength and thermal shock resistance of the aluminum nitride substrate 36 and the copper plate 38 were compared with those of the conventional bonded substrate as in the first embodiment. In all of the aluminum nitride bonded substrates 28 of this example, the peel strength was 14 kg / cm or more, and cracks did not occur even after 100 cycles in the thermal shock test, whereas the conventional one had a peel strength of 8 kg / cm and 10 cycles. The result was that cracks occurred. Also in this example, it is shown that the aluminum nitride bonded substrate 28 has stronger bonding strength than the conventional one and has sufficient durability against temperature change (temperature cycle).

That is, also in this embodiment, the silver-copper alloy 3 having the content ratio of the molybdenum particles 32 is the same as in the first embodiment.
The ratio with respect to the content ratio of 4 is the aluminum nitride substrate 36.
Since the metal layer 30 formed on the aluminum nitride substrate 36 absorbs the difference in coefficient of thermal expansion between the copper plate 38 and the aluminum nitride substrate 36, the metal layer 30 formed on the aluminum nitride substrate 36 absorbs the difference. Almost no resulting thermal stress occurs. For this reason, residual thermal stress (residual stress) due to heating / cooling when joining the copper plates 38 becomes small, and high joining strength can be obtained as described above, and cracks and peeling do not occur even if temperature changes occur. The aluminum nitride bonded substrate 28 is obtained, and when it is used as a substrate for a power module or the like that generates a large amount of heat as in the first embodiment, the copper plate 38 bonded to one surface serves as a heat dissipation plate. It works and has high durability and reliability.

Further, since a mixture of silver-copper-titanium mixed powder and molybdenum powder having different mixing ratios and a silver-copper brazing material are used to form a three-layered printed layer by printing and lamination, By firing this, the metal layer 3 in which the ratio of the content rate of the silver-copper alloy to the content rate of molybdenum increases as the distance from the aluminum nitride substrate 36 increases.
0 is easily obtained. At this time, since the mixture paste to be printed contains titanium, this titanium diffuses into the metal layer 30 and acts as an active metal, so that the aluminum nitride substrate 36 and the copper plate 38 are firmly bonded. Furthermore, in this embodiment, since the silver-copper alloy layer (metal layer 30c) is formed on the copper plate 38 side and the wettability between the copper plate and the silver-copper brazing material at the time of joining is good, it is sufficient. A good bonding strength can be obtained, and good durability can be obtained together with good thermal conductivity.

Also in this embodiment, since the copper plates 38 having the same size and shape are bonded to both surfaces of the aluminum nitride substrate 36, the same degree of thermal stress is generated on both surfaces when the temperature changes. Therefore, the aluminum nitride bonded substrate 28 having higher durability against temperature changes can be obtained. Further, since the copper plate 38 is an oxygen-free copper plate, the copper plate 3
8 has good wettability with the brazing material, and there is no reduction in the activity of the active metal due to the reaction between the active metal in the brazing material and oxygen in the copper plate. A strong joined body can be obtained.

Further, in this embodiment, since the ceramic sintered body is the aluminum nitride substrate 36, it has a higher thermal conductivity than the case of using the alumina substrate of the first embodiment, and is used as a substrate for a power module or the like. It is more preferable.

Next, another embodiment of the present invention will be described.

50 × having the same composition as that used in the first embodiment
50 × 5 mm alumina sintered body, aluminum nitride sintered body of the same composition and size as the second embodiment, 50 × 50 × 1
0 mm silicon nitride sintered body (Si ₃ N ₄ 92% by weight, balance Al ₂ O ₃ , Y ₂ O ₃ and trace unavoidable impurities)
And a 50 × 50 × 10 mm zirconia sintered body (ZrO
₂ 97%, the remainder Y ₂ O ₃ and traces of unavoidable impurities) (hereinafter, when not particularly distinguished are prepared as ceramic sintered body), a mixture paste A used in the first embodiment
₁ , B ₁ and C ₁ were respectively laminated and degreased on one surface of the ceramic sintered body in the same manner as in the first embodiment to obtain four kinds of printed ceramic sintered bodies.

Next, an oxygen-free copper plate having a thickness of 0.5 mm, an SS41 steel plate having a thickness of 5 mm, and a SUS430 having a thickness of 5 mm.
A steel plate (hereinafter referred to as a metal plate unless otherwise specified) is prepared, and one of them is placed on the paste printing surface of each of the four types of printed ceramic sintered bodies described above, and heating is performed as in the first embodiment. By processing, 12 types of ceramic-metal bonded bodies were obtained. In the obtained ceramic-metal bonded body, the metal body was bonded to the ceramic sintered body via the metal layer, and the metal layer had the same cross-sectional structure shown in FIG. 5 as in the first embodiment. .

Here, the bonding strength of the ceramic-metal bonded body was measured by a shear test and compared with the conventional bonding with a brazing material and bonding with a buffer material. As a result, the shear strength of the ceramic-metal bonded body of this example was 10 in all cases.
While was kg / mm ² or more strength, the strength of the bonded body according to the conventional method was less than 8 kg / mm ^2. Further, when the same thermal shock test as in the first example was conducted,
In all of the ceramic-metal bonded bodies of this example, cracks did not occur even after 100 cycles, whereas in the bonded body according to the conventional method, cracks occurred after 10 cycles. Also in this example, it was shown that the bonding strength was improved as compared with the conventional bonding method.

That is, also in this embodiment, since the metal layer has the same structure as that of the first embodiment, the residual stress at the time of joining is small, and the metal body and the ceramic sintered body are separated even when the temperature changes. The difference in the coefficient of thermal expansion is absorbed by the metal layer and the thermal stress is reduced, so that a ceramic-metal bonded body having high bonding strength and durability can be obtained. The silicon nitride sintered body is a material having large bending strength and fracture toughness, and the joined body using the same had particularly good thermal shock resistance.

Further, by appropriately determining the coefficient of thermal expansion, the number of laminated layers, and the thickness of the metal layer according to the types, shapes, and dimensions of the ceramic sintered body and the metal body to be joined, as shown in this embodiment. Since various ceramic-metal bonded bodies can be obtained, they are also useful for automobile engine parts, rocket outer wall materials, and the like.

Although the embodiments of the present invention have been described in detail above, the present invention can be carried out in still another mode.

In the examples, tungsten powder having an average particle diameter of 2.4 μm and molybdenum powder having an average particle diameter of 2.6 μm were used as the refractory metal used in the mixture, but instead of this, an average particle diameter of 20 μm. The following tungsten powder and molybdenum powder may be used. If the average particle size becomes too small, handling becomes difficult, and if it becomes too large, the problem that uniform dispersion does not occur tends to occur. Therefore, the particle size is preferably 0.5 to 10 μm, more preferably 0.5 to 6 μm. It is preferable to use a powder having an average particle size of about 0.0 μm. Further, the refractory metal is not limited to one of tungsten and molybdenum, and may be a mixture of these.

The content of the refractory metal in the mixture is appropriately determined according to the required coefficient of thermal expansion, but when the content of the silver-copper alloy is too low, sufficient bonding strength can be obtained. 80% for all layers when printed and laminated
It is necessary to be below, and in order to obtain higher strength, it is desirable to be below 60%. Also, the metal layer is
It is preferable to continuously change the ratio of the content of the silver-copper alloy to the content of the refractory metal in order to reduce the thermal stress, but two or more layers with different ratios (that is, the ratio changes stepwise. Layer), a sufficient effect can be obtained. To obtain a metal layer in which the ratio changes continuously, for example,
It suffices to reduce the difference in the content ratio between the layers and to make the structure as multilayer as possible. By doing so, there is no rapid change in the ratio at each layer interface due to the occurrence of the movement of the refractory metal and the silver-copper alloy at each layer interface at the time of joining, and the above ratio is continuously changed. A changing metal layer is obtained. In the case of a stepwise change, it is more preferable to be composed of three or more layers having different ratios in order to reduce thermal stress.

In addition to the compositions shown in the examples, the silver-copper alloy may have a composition of 100 to 100% in the range of 40 to 96% by weight of silver and 4 to 60% by weight of copper. If necessary, Ni may be contained in the range of 3 wt% or less, Li of 0.5 wt% or less, Sn of 10 wt% or less, and In of 15 wt% or less. The conditions in the heating step are mainly determined by this composition, the metal body and the ceramic sintered body to be joined, the temperature is 650 to 950 ° C., and the atmosphere is 1 × 10 ⁻³ torr or more (preferably 1 × 10 ^{− 4} or more) vacuum or inert gas such as Ar or N ₂ gas,
It is heated by applying a load of 0.1 to 0.5 g / mm ² in an H ₂ gas atmosphere.

The active metal used is titanium (T
In addition to i), it may be Nb, Hf, Zr, etc., and the active metal is contained in all of the mixture as described in the examples, or contained in the mixture forming any one of the layers, In the step of laminating the mixture, any layer may be laminated as a layer of active metal alone. Since the active metal easily diffuses, it is sufficient that the active metal exists in at least one of the metal layers between the ceramic sintered body and the metal body. Further, the average particle diameter of the active metal is not limited to 20 μm shown in the embodiment, but may be any value as long as it is sufficiently diffused during heating, for example, 10 μm or 30 μm.
It may be about m. In order to obtain sufficient bonding strength, the addition amount of the active metal to the silver-copper alloy is 0.
It is necessary to be 1% or more, preferably 2% or more, and since the active metal causes strength reduction when excessively diffusing into the ceramic sintered body, the addition amount is 25% or less, preferably 10% or less, more preferably It should be 5% or less. Further, when the layer of the active metal alone is provided as described above, it is desirable to stack the layers as close to the metal body as possible in order to avoid excessive diffusion into the ceramic sintered body.

In addition, the mixture may contain a ceramic raw material having the same composition as the ceramic sintered body constituting the ceramic-metal bonded body, a glass component such as SiO _{2 and the} like. In this case, its content needs to be such that the thermal conductivity and bonding strength of the metal layer are not deteriorated.

As the ceramic sintered body, spinel, mullite, silicon carbide, boron carbide, boron nitride, sialon, zircon, etc. can be used in addition to those shown in the examples. Low material is relatively suitable for such applications, as the signal delay time is relatively short when used as a substrate material. In addition to these unavoidable impurities, these ceramic sintered bodies may contain a sintering aid. As the sintering aid, in addition to those shown in the examples, for example, for alumina, Y ₂ O ₃ , B is used.
aO, Cr ₂ O ₃ etc.
CaO, BaO, SrO, CaCO ₃ , BaCO ₃ , S
rCO ₃ , calcium aluminate, La ₂ O ₃ , CeO
₂ etc. In addition to the plate shape shown in the embodiment, the shape may be a prismatic shape, a cylindrical shape, or the like depending on the application, and may be a multilayer substrate or the like having a laminated structure. Furthermore, according to the method of the present invention, since the thermal stress generated is small, it is possible to bond a metal to a relatively low-strength ceramic sintered body.

As the metal body, tough pitch copper, iron-based steel materials, nickel, titanium steel and the like can be used in addition to those shown in the examples, and the shape thereof is the same as that of the ceramic sintered body. Various materials such as a plate shape, a prism shape, and a column shape can be used. The heating step in the manufacturing method of the present invention is appropriately determined according to the material of the ceramic sintered body, the metal body, the composition of the mixture, and the like.

Furthermore, in the ceramic-metal bonded body of the present invention, the metal layer interposed between the ceramic sintered body and the metal body reduces the thermal stress due to the difference in the coefficient of thermal expansion between the two. It is possible to bond a bonded body and a metal body having a high coefficient of thermal expansion with higher bonding strength and durability than those of the related art, and therefore the conventional limit 10
Shape exceeding 0x100x0.5mm, for example 5m thickness
It is possible to join metal bodies of m or more. For example, when it is used for a semiconductor module for a piezoelectric element or the like, a relatively thick copper circuit board can be joined, and a large current (50-60
A substrate is obtained on which A) can flow.

As a method of forming the metal layer, in addition to the method of printing the paste on the ceramic sintered body described in the embodiment, a raw mixture sheet of a predetermined type prepared by, for example, a doctor blade method is laminated. Depending on how
In the case of using the printing method, if a relatively thick layer (50 μm or more) is required, the same paste may be overlaid and printed.

Although not illustrated one by one, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a process flow chart of an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a stacking process of FIG.

FIG. 3 is a partial cross-sectional view of FIG.

4 is a perspective view showing an alumina bonded substrate manufactured by the process shown in FIG. 1. FIG.

5 is a partial cross-sectional view of FIG.

FIG. 6 is a partial cross-sectional view of a ceramics-metal bonded body according to another embodiment of the present invention, which is a view corresponding to FIG. 5.

[Explanation of symbols]

 10: Alumina substrate 16: Copper plate 20: Alumina bonding substrate 22: Metal layer

Claims (7)

[Claims] 1. A ceramic sintered body, a metal layer formed on at least a part of the surface of the ceramic sintered body, and a metal body bonded to the ceramic sintered body via the metal layer. A ceramics-metal joined body, wherein the metal layer contains a refractory metal, a silver-copper alloy, and an active metal, and the content of the refractory metal is relative to the content of the silver-copper alloy. The ceramic-metal bonded body, wherein the ratio is reduced continuously or stepwise as the distance from the surface of the ceramic sintered body increases. 2. The ceramic-metal bonded body according to claim 1, wherein the metal body is bonded to the metal layer via the silver-copper alloy layer. 3. The ceramic-metal bonded body according to claim 1, wherein the ceramic sintered body is a substrate, and the metal body is a copper plate or a copper alloy plate. 4. The metal / ceramics joined body according to claim 3, wherein a circuit pattern is formed on at least a part of the metal body. 5. The ceramic-metal bonded body according to claim 1, wherein the ceramic sintered body is an alumina sintered body or an aluminum nitride sintered body. 6. Ceramic firing using a mixture of at least two or more kinds, which contains a refractory metal and a silver-copper alloy and has a different content ratio of the refractory metal to that of the silver-copper alloy. A stacking step of forming a mixture layer on the surface of at least a part of the united body in the descending order of the ratio, and a step of positioning a metal body in contact with the surface of the mixture layer opposite to the ceramic sintered body. And a heating step of performing heat treatment in the presence of an active metal, the method for producing a ceramic-metal joined body. 7. The ceramic-metal bonded body according to claim 6, wherein the active metal is contained in the mixture layer formed by the laminating step or laminated outside the mixture layer. Production method.