JPH0748180A - Ceramic-metal conjugate - Google Patents

Abstract

PURPOSE:To obtain a ceramic-metal conjugate prevented from developing debonding or cracking under heat cycle environment with thermal shock by jointing a specific ceramic sintered compact to either metallic copper, copper alloy, metallic aluminum or aluminum alloy. CONSTITUTION:First, magnesia powder or its mixture with spinel powder is incorporated with a sintering auxiliary followed by pressure molding and then sintering at 1200-1850 deg.C to obtain a ceramic substrate 10>=9.5X10<-6>/ deg.C in average thermal expansion coefficient as magnesia sintered compact or spinel-magnesia sintered compact. Second, silver-copper-based alloy foils containing an active metal and cut to specified shape are placed on both surfaces of this substrate followed by heat treatment at 850 deg.C for 15min at 5X10<-5>Torr under a load of e.g. 0.3g/m<2> through spacers, thus obtaining the objective substrate 20 where copper plates 18 are jointed to both the surfaces of the ceramic substrate 10 through an alloy layer (joint layer) 16, i.e., either active metal-contg. alloy layer, a solidified matter layer from a eutectic melt composed of copper and copper oxide, or layer of compound with the ceramic sintered compact component (s).

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 more particularly to a ceramic-metal bonded body excellent in thermal shock resistance.

[0002]

2. Description of the Related Art In recent years, not only computers and communication devices, but also all kinds of electronic devices, from industrial devices to home electric appliances, have been remarkably miniaturized and have high performance, and semiconductors used have high power and high integration. In addition, there is a trend toward modularization, and high heat dissipation characteristics are particularly required for semiconductor mounting boards for high-power ICs and power modules. As a radiator and heat sink as a cooling component that dissipates thermal energy and suppresses temperature rise, conventionally, alumina,
Ceramics such as beryllia, aluminum nitride, silicon carbide, cubic boron nitride and diamond, and metals such as aluminum, aluminum alloys, copper, copper alloys, tungsten and molybdenum are selected according to the purpose or used in combination. ing. Among them, alumina and aluminum nitride are excellent in thermal conductivity, electrical insulation, and mechanical properties. Therefore, as a material having both high heat dissipation and high insulation, conventionally, for example, copper or aluminum is used. Used as a ceramics substrate by joining the circuit boards of. In particular, since copper has high heat conduction and low resistance, it is essential to cope with high power.

[0003]

However, the coefficient of thermal expansion of the general ceramic sintered body containing alumina and aluminum nitride is about 3 to 9 × 10 ⁻⁶ / ° C.
The coefficient of thermal expansion of metals such as copper and aluminum is 16 × 10 ^-6 /
Greater than ℃. Therefore, when these ceramic sintered body and metal are joined, large thermal stress due to the difference in coefficient of thermal expansion occurs during cooling in the joining process, resulting in peeling of the metal plate or cracking of the ceramic sintered body. Or, a residual stress is generated in the bonded body and sufficient strength cannot be obtained. Further, when these bonded bodies are used in a heat cycle environment where ambient temperature changes and repeated thermal shocks are applied, cracks occur inside the ceramic sintered body due to thermal stress generated due to the difference in coefficient of thermal expansion. Occurs, the adhesive strength, the airtightness, the electrical insulation is deteriorated, and finally, peeling occurs between the metal plate and the ceramic sintered body, and the ceramic sintered body has a defect such as damage, There is a problem that it cannot be used as a highly reliable component. For example, thickness 0.
In the case of a conventional heat sink in which a 3 mm copper foil is bonded to both sides of an alumina substrate of 50 × 30 × 0.635 mm, -4
In a heat cycle test in which holding at 0 ° C. for 30 minutes and holding at 150 ° C. for 30 minutes are repeated, almost damage occurs after about 50 to 200 cycles. Therefore, the heat sink cannot be applied to a field requiring high reliability such as high thermal shock resistance of at least 1000 cycles.

Further, the ceramic heat sink materials other than the above-mentioned alumina and aluminum nitride all have a coefficient of thermal expansion equal to or less than that of alumina, and have a large difference from the coefficients of thermal expansion of copper and aluminum. Even with such a bonded body of a ceramic heat sink material and copper or aluminum, there is a problem that the thermal shock resistance is inferior as in the case of the above-described heat sink in which alumina and copper are bonded.

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 thermal stress as disclosed in JP-A-56-41879 are produced by plastic deformation. Although a method of inserting a cushioning material having a high malleability to be absorbed is used, the former method has a considerable difference in the coefficient of thermal expansion between the cushioning material and the ceramic sintered body. There is a problem that the resulting thermal stress occurs,
The latter method has a problem that when the generated thermal stress is extremely large, the plastic deformation of the cushioning material cannot sufficiently absorb the stress.

The present invention has been made in view of the above circumstances, and an object thereof is temperature change, particularly low temperature (eg -50 to -40 ° C) and high temperature (eg + 150 ° C).
In a heat cycle environment in which heating and cooling are repeated for a long period of time, a problem such as peeling of the metal from the ceramic sintered body and cracks in the ceramic sintered body can be appropriately mitigated. It is to provide a ceramics-metal bonded body.

[0007]

In order to achieve such an object, the gist of the present invention is a ceramic-metal bonded body in which a metal plate is bonded to a ceramic sintered body. The average thermal expansion coefficient of the sintered body is 9.
It is a magnesia sintered body or a spinel-magnesia sintered body having a density of 5 × 10 ⁻⁶ / ° C. or more, and the metal plate is made of any one of copper, copper alloy, aluminum and aluminum alloy. .

[0008]

[Effects and Effects of the Invention] In this way, the coefficient of thermal expansion of the ceramic sintered body is relatively large and is 9.5 × 10 ^-6.
Since the magnesia sintered body and the spinel-magnesia sintered body having a temperature of / ° C or higher are used, the difference in the coefficient of thermal expansion from the metal plate to be joined is small. Therefore, the residual stress at the time of joining is reduced, and the thermal stress generated is greatly reduced even in a heat cycle environment where the temperature change is large, especially when a thermal shock such as repeated heating and cooling is applied for a long period of time. Thus, peeling between the ceramic sintered body and the metal plate and generation of cracks in the ceramic sintered body are appropriately alleviated, and a ceramic-metal bonded body excellent in durability and reliability can be obtained. In addition, high heat conductivity copper, copper alloy,
Since either aluminum or an aluminum alloy is used, high heat dissipation can be obtained, and a ceramic-metal bonded body having more excellent durability and reliability can be obtained. For example,
In the 50 × 30 × 0.635 mm dimension and shape, it has a heat resistance cycle characteristic of at least 10 times or more, that is, 500 cycles or more, as compared with the case of bonding a copper plate to a conventional alumina or aluminum nitride substrate.

Further, preferably, the metal plate is copper or a copper alloy, and the metal plate and the ceramic sintered body are
Bonded through any bonding layer of an alloy layer containing an active metal, a solidified layer of a eutectic melt of copper and copper oxide, or a compound layer of copper and a component of the ceramic sintered body. ing. In such a ceramics-metal bonded body, the metal plate and the bonding layer are firmly bonded to each other, and the ceramic sintered body and the bonding layer are bonded firmly to each other, so that high bonding strength is obtained.

Further, preferably, a circuit is formed on at least a part of the metal plate, and the ceramic sintered body is a substrate or a package for semiconductor mounting. When such a ceramic-metal bonded body is used in a power semiconductor module or the like, heat generated in a semiconductor or an electronic component is appropriately dissipated, and peeling or cracking occurs even when a temperature change occurs. Since copper, copper alloys, aluminum, and aluminum alloys used for metal plates also have low resistance, they can be used as substrates or packages that require high reliability for large current and large power circuits. It is suitable and can be used for a power transistor module, a microwave transistor module, a power hybrid IC substrate, and the like.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

For example, a vehicle containing ethyl cellulose and terpineol as the main components is added to and mixed with the silver-copper mixed powder containing the active metal having the composition shown in Table 1, and the mixture is kneaded with, for example, a three-roll mill to mix powder pastes P1 to P13. Was produced. In addition, silver containing an active metal having a composition shown in Table 1-
Copper-based alloy foils (thickness 50 μm) H1 to H13 were prepared.

[0013]

[Table 1]

Next, for example, a sintering aid is added to the magnesium powder obtained by thermally decomposing a magnesium compound (eg, magnesium salt such as magnesium hydroxide or basic magnesium carbonate), and a pressure is applied. After molding, sinter at a predetermined temperature (eg 1200 to 1850 ° C),
For example, No. 1 shown in Table 2 with dimensions of 50 × 33 × 0.6 mm
No. 8 ceramic substrates (magnesia substrates) 10 were obtained. After printing the mixed powder pastes P1 to P13 with a thickness of about 20 μm on both surfaces of the ceramic substrate 10, the temperature is 130 ° C.
Then, 104 kinds of printed boards 14 as shown in FIG. 1 having printed layers 12 formed on both sides thereof were obtained. This printed circuit board 14
A predetermined circuit pattern schematically shown in FIG. 1 is formed on one surface (the upper surface in FIG. 1). Next, these printed circuit boards 14 are subjected to, for example, N ₂ atmosphere at 600 ° C.
Degreasing is performed, and an oxygen-free copper plate having a thickness of 300 μm and a thickness of 350 μm are respectively placed on the printing layers 12 on both sides of the printed board 14, and a load of, for example, 0.3 g / mm ² is applied via a spacer, for example, 5 × 10 5. ^The ceramic substrate 10 as shown in FIG. 2 is obtained by heat treatment at 850 ° C. for 15 minutes in a vacuum of ⁻⁵ torr.
A ceramic bonded substrate 20 was obtained in which the copper plates 18 were bonded to both surfaces of the copper plate 18 via the alloy layer 16. In this example, the alloy layer 16 corresponds to the bonding layer.

[0015]

[Table 2]

Separately, the alloy foils H1 to H13 are cut into a predetermined shape and placed on both surfaces of the ceramic substrate 10 of No. 1 to No. 8 shown in Table 2 above, and further placed on this alloy foil. Thickness 30
An oxygen-free copper plate of 0 μm is placed, a load of, for example, 0.3 g / mm ² is applied through a spacer, and, for example, 5 × 10 ⁻⁵ to
Heat treatment was performed at 850 ° C. for 15 minutes in a vacuum of rr, and copper plates 18 were formed on both surfaces of the ceramic substrate 10 with the alloy layers 16 interposed therebetween on both sides of the ceramic substrate 10 as shown in FIG. A ceramic bonded substrate 20 bonded with was obtained.

Separately, a No. 9 alumina substrate and a No. 10 aluminum nitride substrate having the same size and shape as the ceramic substrate were prepared separately, and mixed powders P1 to P13 and alloy foils H1 to H13 were used in the same manner as above. As a comparative example, a copper-alumina bonded substrate and a copper-aluminum nitride bonded substrate were respectively manufactured.

These obtained ceramic bonded substrates 20
When the peel strength of the copper-alumina bonded substrate and the copper-aluminum nitride bonded substrate was measured by a peel strength test, all the samples were 10 kg / cm or more. In addition,
The peel strength test is obtained by bonding a tensile terminal to a bonded substrate, peeling a copper plate from a ceramic substrate in a direction of 90 ° with a tensile tester, and measuring a load when peeled.

Next, the ceramic bonded substrate 20 and the copper-
In order to evaluate the thermal shock resistance of the alumina-bonded substrate and the copper-aluminum-nitride bonded substrate, 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 was defined as one cycle. The test was repeated. The temperature was adjusted very quickly by sending cold or hot air into the tester. As a result, in the ceramic bonded substrate 20 (that is, the bonded substrates using the magnesia substrates of No. 1 to No. 8 in Table 2), neither crack nor peeling was observed even after 2000 cycles. On the other hand, the No. 9 and No. 10 copper-alumina bonded substrates and the copper-aluminum nitride bonded substrates, which are comparative examples that were simultaneously tested, were tested after 100 to 150 cycles and 50 to 100 cycles, respectively. Later, cracks occurred on the ceramic side and the copper plate peeled off. From the above test, it was confirmed that the ceramic bonded substrate 20 of this example has a high bonding strength and a thermal shock resistance 10 times or more higher than the conventional one.

That is, in the ceramic bonded substrate 20 of this embodiment, since the magnesia sintered body having a relatively large coefficient of thermal expansion is used as the ceramic substrate 10, there is a difference in the coefficient of thermal expansion from the bonded copper plate 18. small. Therefore, even when the temperature changes, the thermal stress caused by the difference in the coefficient of thermal expansion is relatively small, and the durability is higher than that of the bonded substrate using the conventional alumina substrate and aluminum nitride substrate. To show.

Further, as shown in Table 2, since the magnesia sintered body has a relatively higher thermal conductivity than alumina, the magnesia sintered body is relatively excellent in heat dissipation and is generated on the ceramic substrate 10 side when used as a heat sink or the like. Heat is a metal or copper plate 18
Is preferably transmitted from the side and is preferably dissipated from the side of the metal plate,
A more reliable ceramic-metal bonded body can be obtained.

Further, since a copper plate 18 having a high thermal conductivity and a low resistance is used as the metal body and a circuit is formed on the copper plate 18 on one surface, it is excellent in heat dissipation and can cope with a large current. And a highly reliable ceramic-metal bonded body can be obtained even for a large power circuit.

Further, since the ceramic substrate 10 and the copper plate 18 are bonded via the silver-copper alloy layer containing the active metal, the active metal diffuses near the interface between the ceramic substrate 10 and the copper plate 18 during the heat treatment. Further, higher joint strength can be obtained.

Further, since the oxygen-free copper plate is used as the metal plate to be bonded, the wettability between the copper plate and the alloy layer is good, and the reaction between the active metal in the bonding layer and the oxygen in the copper plate is good. Since there is no decrease in the activity of the active metal due to this, a strong joined body of the copper plate and the ceramic sintered body can be obtained.

Further, since the copper plates 18 having substantially the same thickness are bonded to both sides of the ceramic substrate 10, even when thermal stress caused by temperature change is generated, the thermal stress generated on both sides is offset to further improve durability. The ceramic bonded substrate 20 having high properties is obtained.

The ceramic bonded substrate 20 of this embodiment is used.
Since it has a structure in which the thermal stress is reduced as described above, it is possible to shorten the cooling time during the heat treatment as compared with the conventional bonded substrate. Therefore, the manufacturing process is shortened, the heat treatment is easily controlled, and the cost is reduced. The ceramic-bonded substrate 20 having a significantly higher cooling rate than the conventional one (that is, the rate at which a copper-alumina bonded substrate causes peeling or cracks in the alumina substrate) was evaluated by the thermal shock tester to be 1000. It was confirmed to have a thermal shock resistance equal to or longer than the cycle.

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

With respect to the silver-copper mixed powder containing the active metal having the composition shown in Table 1, 20 internal weight% of refractory metal powder (for example, tungsten (W) powder or molybdenum (M
o) powder or a mixed powder thereof, and then adding W or M to the silver-copper mixed powder in the same manner as in the first embodiment.
13 kinds of pastes P14 to P26 containing o were prepared.

Next, using No. 1 to No. 8 magnesia substrates shown in Table 2, pastes P14 to P26 are printed on both surfaces of the substrate 10 in the same manner as in the first embodiment, and after degreasing, an oxygen-free copper plate is mounted. Then, heat at 850 ° C. for 15 minutes in a vacuum of 1 × 10 ⁻⁵ torr, and apply copper plates 1 to both sides of the ceramic substrate 10 as shown in FIG.
A ceramics-metal bonded substrate 20 having 8 bonded thereto was obtained. The peel strength of each of the obtained bonded substrates 20 is 10 k.
It was g / cm or more. The joint substrate 20 was also evaluated for thermal shock resistance in the same manner as in the first embodiment.
After the cycle, neither cracking of the ceramic substrate 10 nor peeling of the copper plate 18 was observed.

Also in this embodiment, as in the first embodiment, the difference in the coefficient of thermal expansion between the ceramic substrate 10 and the copper plate 18 is small and the generated thermal stress is relaxed, so that it has high thermal shock resistance. Therefore, a highly reliable ceramic-metal bonded body can be obtained. Further, in this embodiment, since the ceramic substrate 10 and the copper plate 18 are bonded to each other via the alloy layer containing the high melting point metal powder in the silver-copper mixed powder, the coefficient of thermal expansion of the alloy layer is high. The thermal stress due to the difference in the coefficient of thermal expansion between the ceramic substrate 10 and the copper plate 18 is further reduced by being made smaller by the melting point metal, and a ceramic-metal bonded body having more excellent thermal shock resistance and high reliability can be obtained. .

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

For example, No. 1 shown in Table 3 having a size of 50 × 33 × 0.6 mm obtained by mixing magnesia powder and spinel powder in a predetermined ratio and press-molding.
Using the mixed powder pastes P1 to P13 and the alloy foils (thickness 50 μm) H1 to H13 in the same manner as in the first embodiment except that the 1 to No. 16 spinel-magnesia substrates (sintered bodies) were used, As shown in FIG. 2, a ceramics-bonded substrate (spinel-magnesia-based bonded substrate) 20 having oxygen-free copper plates bonded to both surfaces of the substrate was obtained. Further, as a comparative example, a copper-spinel bonded substrate was produced in the same manner using the No. 17 spinel substrate. When the peel strengths of the obtained ceramic bonded substrate 20 and copper-spinel bonded substrate were measured, all showed a value of 10 kg / cm or more.

[0033]

[Table 3]

Next, the thermal shock resistance of the above-mentioned ceramic bonded substrate 20 and copper-spinel bonded substrate was evaluated in the same manner as in the first embodiment, and it was found that the ceramic bonded substrate 20 was ceramic substrate 10 even after 1000 cycles. No cracks or peeling of the copper plate 18 were observed. On the other hand, the thermal expansion coefficient of the comparative example is as low as 7.6 × 10 ^-6 , No. 17
The copper-spinel bonded substrate using the substrate having the composition of
After the cycle, the board cracked and the copper plate 1
8 peeling occurred.

That is, also in the present embodiment, the ceramic bonded substrate 20 has a small difference in the coefficient of thermal expansion between the ceramic substrate 10 and the copper plate 18 as in the first embodiment, and therefore occurs when a temperature change occurs. The resulting thermal stress is reduced, and high thermal shock resistance and durability are exhibited.

Further, in this embodiment, since the ceramic sintered body in which magnesia is mixed with spinel is used as the substrate, the damage of the substrate due to the digestion of the magnesia sintered body is suppressed and the durability is further improved. Reliable.
It is considered that this is because the spinel is dispersed in the crystal grain boundaries of magnesia to protect the crystal surface of magnesia.

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

N in Table 2 with dimensions of 50 × 33 × 0.6 mm
o.1 to No.8 (Magnesia sintered body), No.11 to No.16 in Table 3
(Spinel-Magnesia sintered body) ceramic substrate 1
0, a tough pitch electrolytic copper foil (thickness 300 μm and 350 μm) was placed on the upper and lower surfaces of the substrate, and heat treated at a temperature of about 1075 ° C. for 5 minutes in an N ₂ atmosphere to bond them, and as shown in FIG. A ceramic bonded substrate 20 was obtained. Also,
Using the No. 9 alumina substrate, the No. 10 aluminum nitride substrate and the No. 17 spinel substrate, copper-alumina bonded substrates, copper-aluminum nitride bonded substrates and copper-spinel bonded substrates were obtained in the same manner. When the peel strength of each of the obtained bonded substrates was measured, all showed a value of 10 kg / cm or more.

Next, these ceramic bonded substrate 20, copper-alumina bonded substrate, copper-aluminum nitride bonded substrate,
When the thermal shock resistance of the copper-spinel bonded substrate was evaluated in the same manner as in the first embodiment, the ceramic bonded substrate 20 (that is,
No.1 to No.8 magnesia bonded substrates and No.11 to No.16
The spinel-magnesia junction substrate) is 1000
After the cycle, neither cracking of the ceramic substrate 10 nor peeling of the copper plate 18 was observed. In contrast, the No. 9 copper-alumina bonded substrate, No. 10 copper-aluminum nitride bonded substrate, and No. 17 copper-spinel bonded substrate, which are comparative examples, are on the ceramic substrate side after 150, 100, and 150 cycles, respectively. A crack was generated on the copper plate and the copper plate was peeled off.

That is, also in the present invention, as in the first embodiment, since the difference in the coefficient of thermal expansion between the ceramic substrate 10 and the copper plate 18 is small, the thermal stress generated when a temperature change occurs is reduced. It shows high thermal shock resistance and durability.

In the present embodiment, the copper plate 18 reacts with the ceramic substrate 10 by a eutectic reaction or the ceramic substrate 1.
It is bonded by a compound with 0 component (main component, sintering aid, glass forming substance, etc.), and a solidified product of the eutectic melt or the compound is formed in the bonding layer.

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

Aluminum-silicon brazing filler metal having a thickness of 50 μm was applied to No. 1 to No. 8 and No. 11 to No. 16 ceramic substrates 10 of Tables 2 and 3 having dimensions of 50 × 33 × 0.6 mm. An aluminum plate (thickness: 300 μm) is placed on the upper and lower surfaces of the substrate through the spacer, and a spacer, for example, 0.3 g /
A load of mm ² was applied, and heat treatment was performed at a temperature of 610 ° C. for 15 minutes in a vacuum of 10 ⁻⁵ torr to obtain a ceramic bonded substrate 20 having aluminum plates bonded to both sides as shown in FIG. At the same time, No.9, No.10, and No.17 alumina substrates, aluminum nitride substrates, and spinel substrates were processed in the same manner to obtain aluminum-alumina bonded substrates, aluminum-aluminum nitride bonded substrates, and aluminum-spinel bonded substrates. . When the peel strength of each of the obtained bonded substrates was measured, all were 8 kg / cm or more.

Next, when the thermal shock resistance of these bonded substrates was evaluated in the same manner as in the first embodiment, the ceramic bonded substrate 20 (that is, the magnesia bonded substrates of No. 1 to No. 8 and No. 11 to No. 11) was evaluated. In No. 16 spinel-magnesia bonded substrate), neither cracking of the ceramic substrate 10 nor peeling of the aluminum plate 18 was observed after 1000 cycles. On the other hand, Comparative Example No. 9 aluminum-alumina bonded substrate, No. 10 Aluminum-
The aluminum nitride bonded substrate and the No. 17 aluminum-spinel bonded substrate were cracked on the ceramic substrate side after 150, 100 and 150 cycles, respectively, and the aluminum plate was peeled off.

That is, also in this embodiment, the ceramic bonded substrate 20 has a difference in the coefficient of thermal expansion between the ceramic substrate 10 and the aluminum plate 18 smaller than that of the conventional one, as in the first embodiment, so that the temperature change. The thermal stress generated when is caused is reduced, and high thermal shock resistance and durability are exhibited.

FIG. 3 shows a power semiconductor module 22 in which the ceramic bonding substrate 20 according to the embodiment of the present invention is used.
It is a figure which shows typically the example applied to. A semiconductor element 24 is joined to a part of the copper plate 18 having a circuit pattern and joined to one surface of the ceramic joined substrate 20 via a solder layer 26. Further, the semiconductor element 24 is connected to the other portion of the copper plate 18 by the wiring 28. The ceramic bonding substrate 20 used in the power semiconductor module 22 is the heat dissipation plate on the surface of the ceramic substrate 10 opposite to the surface on which the semiconductor element 24 is bonded, as described in the above embodiments. The copper plate 18 is bonded (see FIG. 2) so that the heat generated in the semiconductor element 24 can be appropriately dissipated, and the excellent thermal shock resistance,
It has durability and reliability. In this example,
The alloy layer 16 is omitted in the drawing.

In FIG. 4, the ceramic bonding substrate 20 is
It is sectional drawing which shows the example applied to the other power semiconductor module 30 typically. The structure on the side where the semiconductor element 24 is bonded to the ceramic substrate 10 is substantially the same as that of the power semiconductor module 22 described above, and therefore description thereof is omitted. The alloy layer 1 is formed on the opposite surface of the ceramic substrate 10.
The copper plate 18 is joined via 6 and the heat sink 3
2 are joined via the solder layer 34. Therefore, as compared with the power semiconductor module 22 described above, the heat generated in the semiconductor element 24 is dissipated more efficiently. The heat sink 32 is provided with many fins 36 on the opposite side of the solder layer 34 to increase the surface area in order to further improve the heat radiation efficiency. Further, in this embodiment, the copper plate 18 is used not as a heat dissipation plate but as a conductor to form a part of the circuit.

Although one embodiment of the present invention has been described in detail above, the present invention can be implemented in still another mode.

The shape of the magnesia sintered body and the spinel-magnesia sintered body can be changed according to the application such as the plate shape of the embodiment, a cylindrical shape, and the like. A pressure molding method, an injection molding method, or the like is selected according to the application and shape.

The method for producing the magnesium sintered body is not limited to that shown in the examples, and for example, high-purity metallic magnesium obtained by burning (vapor phase oxidation) metallic magnesium in a high-purity oxygen stream. Using pure magnesium powder,
It is also possible to add a sintering aid, if necessary, and to form the material into a predetermined shape, followed by firing. By doing so, a higher purity magnesium sintered body can be obtained. The above-mentioned magnesium powder is particularly preferable because it has less aggregation and is excellent in sinterability.

Further, the method for producing the spinel-magnesia sintered body is not limited to that shown in the examples, and for example, it is formed by using spinel-magnesia powder obtained by thermally decomposing a mixture of a magnesia compound and a spinel compound.・ It may be baked. The spinel-magnesia mixed powder or the method for synthesizing the spinel powder is a method of mixing a magnesium salt and an aluminum salt so as to have a spinel-magnesia mixed composition or a spinel composition to obtain a coprecipitate (coprecipitation method).
Alternatively, a freeze-drying method, a spray pyrolysis method, an alkoxide method, an underwater spark discharge method and the like can be mentioned as preferable methods.

The magnesia sintered body and the spinel-magnesia sintered body may contain a sintering aid and an accessory component in a range of 20% by weight or less. However, the characteristics of the sintered body are such that the coefficient of thermal expansion is 9.5 × 10 ⁻⁶ / ° C. or higher, preferably 11 × 10 ⁻⁶ / ° C. or higher, and more preferably 12.5 × 10 6.
^A temperature of ^-6 / ° C or higher is desirable to reduce thermal stress and obtain high durability and reliability. That is, the thermal cycle characteristics are improved by making the thermal expansion coefficient of the metal body to be joined as close as possible. The thermal conductivity is 0.04cal / cm ・ sec ・ ℃
From the viewpoint of heat dissipation, it is preferably 0.07 cal / cm · sec · ° C. or higher, more preferably 0.09 cal / cm · sec · ° C. or higher.

Further, a magnesia sintered body and a spinel-
The bending strength of the magnesia sintered body needs to be 15 kgf / mm ² or more. If it is less than 15 kgf / mm ² , the thermal shock resistance will be insufficient. Preferably 20k
gf / mm ² or more, more preferably 25 kgf / mm ²
The above is desirable. Thermal shock resistance is a function of bending strength, and higher thermal shock resistance can be obtained by increasing bending strength.

Further, a magnesia sintered body and a spinel-
The magnesia sintered body preferably has a relative density of 95% or more, that is, a porosity of less than 5%. This is because as the porosity increases, the mechanical strength decreases, the number of open pores increases, and the water absorbency is obtained, and the water resistance (that is, the digestion resistance or hydration resistance) of the sintered body decreases. The relative density of the sintered body is preferably 97.5% or more (that is, porosity is less than 2.5%), and more preferably 99% or more (that is, porosity is less than 1%). In this case, open porosity is preferable. The water absorption rate corresponding to is approximately 0%, which is excellent in water resistance, high in mechanical strength, and high in thermal conductivity.

Copper, copper alloys, aluminum and aluminum alloys used for metal plates have a thermal conductivity of 0.3 in particular.
It is desirable that cal / cm · sec · ° C or higher.Since such a metal plate has high thermal conductivity and high conductivity, it has a relatively large current when compared with other metals even with the same shape. It is possible to flow. Therefore, as a circuit board for passing a constant current, there is an advantage that the thickness of the metal circuit board can be reduced as compared with other metals. Among them, single component copper and aluminum are preferable in terms of high thermal conductivity and high conductivity. As copper, copper having a purity of 99.9% or more is generally preferred, and examples thereof include oxygen-free copper, tough pitch copper, and copper phosphate.

The method of joining the magnesia sintered body or the spinel-magnesia sintered body and the metal plate is not limited to the method shown in the examples. For example, when the metal plate is a copper or copper alloy plate, it is shown in Table 1. Through such a brazing material containing an active metal, heat treatment may be performed in a vacuum of 10 ⁻⁴ torr or more or in an inert gas in a temperature range of about 800 ° C. to 1000 ° C. for joining. Alternatively, oxygen is 100 to 3000
It is also possible to join by bonding a copper plate containing about ppm or a copper plate that has been pre-oxidized to a magnesia sintered body or a spinel-magnesia sintered body and heat-treating it in an inert gas atmosphere at a temperature range of 1000 to 1100 ° C. Is. In this case, as described in the above-mentioned examples, the solidified product of the eutectic melt of copper and copper oxide, or the compound of the components of copper and the ceramic sintered body is formed in the bonding layer. Are joined through. Further, when the metal plate is aluminum or an aluminum alloy and aluminum-silicon alloy is used as a brazing material for joining, 550 to 550
It may be heated in the range of 650 ° C.

In the case of joining via an active metal-containing silver-copper alloy, the active metal contained is T.
i is the most preferable, and the content thereof is preferably 2 to 8% by weight. If the amount is too small, the dispersion of the active metal at the bonding interface is insufficient and the bonding strength is reduced, and if it is too large, the ceramic sintered body side is excessively corroded and the bonding strength is also reduced. Further, from the viewpoint of thermal shock resistance, it is 2 to 6
About wt% is particularly preferable.

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 perspective view illustrating a manufacturing process of a ceramic-metal bonded body according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a ceramic-metal bonded body according to an embodiment of the present invention.

FIG. 3 is a perspective view showing an example in which a ceramics-metal bonded body according to an embodiment of the present invention is applied to a power semiconductor module.

FIG. 4 is a cross-sectional view showing an example in which the ceramic-metal bonded body according to the embodiment of the present invention is applied to another power semiconductor module.

[Explanation of symbols]

10: Ceramic substrate 16: Alloy layer (bonding layer) 18: Copper plate (metal body) 20: Ceramic bonding substrate (ceramic-metal bonded body)

Claims (3)

[Claims] 1. A ceramic-metal bonded body comprising a ceramic sintered body and a metal plate bonded to the ceramic sintered body, wherein the ceramic sintered body has an average coefficient of thermal expansion of 9.5 × 10 ^−6.
/ ° C or higher magnesia sintered body or spinel-magnesia sintered body, and the metal plate is made of any one of copper, copper alloy, aluminum and aluminum alloy. . 2. The metal is copper or a copper alloy, and the metal plate and the ceramic sintered body are an alloy layer containing an active metal, a solidified material layer of a eutectic melt of copper and copper oxide, Alternatively, the ceramic-metal bonded body according to claim 1, wherein the ceramic-metal bonded body is bonded via any bonding layer among compound layers of copper and a component of the ceramic sintered body. 3. The ceramic-metal bonded body according to claim 1, wherein a circuit is formed on at least a part of the metal plate, and the ceramic sintered body is a semiconductor mounting substrate or package.