JPH07187839A - Nitride ceramics-metal joined body and its production - Google Patents

Abstract

PURPOSE:To obtain a nitride ceramics-metal joined body satisfying high bonding strength, having superior heat cycle resistance and excellent in mass productivity. CONSTITUTION:A nitride ceramic sheet is joined to a metallic sheet with at least one kind of active metal selected from among Ti, Zr, Hf and Nb and an In-contg. brazing filler metal to obtain the objective nitride ceramics-metal joined body. Joining treatment is carried out in a nitrogen atmosphere capable of use of a continuous furnace excellent in mass productivity. Since the active metal and the In-contg. brazing filler metal are used, joining temp. is reduced, satisfactory joining characteristics are ensured even in the nitrogen atmosphere and heat cycle resistance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-based ceramic-metal bonded body having improved heat resistance cycle characteristics and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for joining a nitride-based ceramic substrate such as aluminum nitride and a metal plate, a so-called DBC method (Direct Bonding copper method) and active metal methods using active metals such as 4A group elements and 5A group elements are known.

The active metal method is a bonding method utilizing the fact that metal elements such as Ti, Zr, Hf and Nb easily wet and react with the ceramic material. Specifically, a nitride ceramics substrate and a metal plate are laminated via an active metal brazing filler metal containing an active metal, and the laminate is fired in a vacuum or an argon atmosphere to obtain a nitride ceramics. The substrate and the metal plate are joined together.

By the way, when a nitride ceramics substrate is used, the firing atmosphere must be a vacuum atmosphere or an argon atmosphere as described above. This is because in the active metal method, high bonding strength is obtained by utilizing the reaction between active metals such as Ti and nitrogen in the nitride-based ceramics substrate. This is because when bonding (baking) is performed in an atmosphere, the active metal reacts with nitrogen in the atmosphere, and as a result, bonding is not performed.

That is, in the joining mechanism by the active metal method, it is considered that the liquid phase formation of the brazing filler metal component by heating promotes the reaction between the active metal and the nitride-based ceramics substrate. If it reacts with nitrogen in the atmosphere before reaching the liquidus temperature of the brazing filler metal component, most of the active metal that already reacts with nitrogen in the nitride-based ceramics substrate is already present when the liquidus temperature is reached. I will not do it. For this reason, when the active metal method is applied to the nitride-based ceramics substrate to join the metal plates, firing is performed in a vacuum where only a batch furnace that is inferior in mass productivity can be used, or the gas itself is expensive. In addition, the use of a batch type furnace also requires firing in a general argon atmosphere, resulting in extremely low mass productivity and high manufacturing cost.

On the other hand, the bonded body of the nitride-based ceramic substrate and the metal plate is required to have high bonding strength, and the coefficient of thermal expansion of the ceramic material is smaller than that of the metal material. There is a strong demand for suppressing the occurrence of such defects. That is, when a nitride-based ceramics substrate and a metal plate having a large coefficient of thermal expansion are bonded to each other, residual stress due to the difference in thermal expansion occurs in the cooling process after bonding, and the bonding strength is significantly reduced due to the synergistic effect with external stress. In addition, cracking occurs from the maximum stress point due to the cooling process after joining and the addition of a heat cycle, and further, the nitride ceramics substrate is broken. Therefore, it has been strongly desired to improve the heat resistance cycle characteristics of the bonded body.

[0007]

As described above, in the bonded body of the nitride ceramics substrate and the metal plate to which the conventional active metal method is applied, a vacuum or an argon atmosphere has to be used as a bonding atmosphere, The mass production is extremely low and the manufacturing cost is high. Also,
Since cracks and the like are likely to occur due to the addition of heat cycles, it has been strongly desired to improve the heat resistance cycle characteristics.

The present invention has been made in order to solve such a problem, and it is a nitride-based ceramic-metal joint which satisfies a high joining strength, exhibits excellent heat cycle characteristics, and is excellent in mass productivity. It is an object to provide a body and a method for manufacturing the body.

[0009]

In order to achieve the above-mentioned object, the present inventor has proposed a conventional nitride ceramics-
As a result of examining various aspects of the metal bonding substrate, it was possible to use a nitrogen atmosphere as a bonding atmosphere by adding In to the active metal brazing material to lower the bonding temperature, and at the same time, a heat-resistant cycle It has been found that the characteristics can be improved.

The present invention has been made based on the above findings. The nitride-based ceramic-metal bonded body of the present invention has a nitride-based ceramic plate and a brazing material layer on the nitride-based ceramic plate. A joined body comprising a joined metal plate, wherein the nitride ceramic plate and the metal plate are Ti,
It is characterized in that they are bonded in a nitrogen atmosphere through the brazing material layer containing at least one active metal selected from Zr, Hf and Nb and In.

Further, the method for producing a nitride-based ceramic-metal bonded body according to the present invention comprises at least one selected from Ti, Zr, Hf and Nb on at least one surface of the nitride-based ceramic plate and the metal plate. A step of forming a coating layer of a brazing filler metal paste containing an active metal and In, a step of laminating the nitride ceramic plate and a metal plate via the coating layer of the brazing filler metal paste, and the laminate Is fired in a nitrogen atmosphere to bond the nitride-based ceramic body and the metal plate to each other.

The nitride ceramics plate used in the present invention contains aluminum nitride or silicon nitride as a main component,
Of the main constituent elements such as aluminum nitride sintered bodies and silicon nitride sintered bodies containing sintering aid components such as yttrium oxide and aluminum oxide, and sialon sintered bodies containing Si, Al, O and N as the main constituent elements. Various ceramics sintered bodies containing nitrogen can be used. Further, the metal plate may be appropriately selected from various metal materials according to the application, for example, Cu plate, Cu alloy plate, Ni plate, Ni alloy plate,
Examples include single plates such as W and Mo, alloy plates, and the like. These metal plates may be patterned in advance according to, for example, the circuit shape.

A nitride ceramics-metal bonded body according to the present invention comprises a nitride ceramics plate and a metal plate as described above, and at least one active metal selected from Ti, Zr, Hf and Nb and an In metal. It is joined in a nitrogen atmosphere using a brazing filler metal containing (hereinafter, referred to as In and active metal-containing brazing filler metal). As the brazing filler metal component used here, for example, an Ag-Cu brazing filler metal or a Cu brazing filler metal having a eutectic composition of Ag-Cu (72 wt% Ag-28 wt% Cu) or a composition in the vicinity thereof is exemplified.
In the present invention, the brazing filler metal and the active metal
An In-added In and brazing filler metal containing an active metal is used.

The amount of active metal added to the brazing material as described above is preferably in the range of 2 to 6% by weight based on the total amount of the brazing material, and the amount of indium added is based on the total amount of the brazing material. It is preferably in the range of 12 to 20% by weight.
If the amount of the active metal is less than 2% by weight, sufficient bonding to the nitride-based ceramics plate cannot be achieved, and if it exceeds 6% by weight, heat cycle characteristics may be deteriorated.
If the amount of indium is less than 12% by weight, the melting point lowering effect cannot be sufficiently obtained, and if it exceeds 20% by weight, a brittle intermetallic compound is likely to be formed.

The melting point of In and the active metal-containing brazing material is lowered by In, and in the case of Ag-Cu based brazing material, for example, the melting point is lowered from the usual 780 ° C. to 680 ° C. As a result, for example, actual joining can be performed at a temperature of about 700 to 800 ° C. On the other hand, the reaction between the active metal and the nitrogen in the nitride-based ceramics plate starts to proceed from about 500 to 600 ° C. Therefore, when using In and an active metal-containing brazing filler metal, even if the bonding is performed in a nitrogen atmosphere, the difference between the reaction initiation temperature and the liquid phase formation temperature of the brazing filler metal is small. Even after reaching the temperature, the reaction between the active metal and nitrogen in the nitride-based ceramic plate sufficiently progresses.

In other words, the In and active metal-containing brazing filler metal forms a liquid phase at a temperature of about 700 ° C., and the reaction between the active metal and the nitride-based ceramic plate is promoted. The reaction between the active metal and the nitride-based ceramics plate proceeds while being promoted by the liquid phase from a temperature at which there is not much difference from the reaction initiation temperature between the active metal and nitrogen, and as a result, nitrogen and active metal in the atmosphere Reaction is suppressed. Therefore,
It is possible to obtain sufficient bonding strength even in a nitrogen atmosphere. Since the joining can be performed in a nitrogen atmosphere in this manner, a continuous furnace having excellent mass productivity can be used.

Further, as described above, by using the brazing material containing In and the active metal, the actual joining temperature is 800
Since it is possible to reduce the temperature from about 900 ° C to about 700 ° C to 800 ° C, the residual stress will be reduced by the amount corresponding to the lowering of the joining temperature, thus improving the thermal cycle resistance of the joined body. it can.

The nitride ceramics-metal bonded body of the present invention is manufactured, for example, as follows.

First, a nitride ceramics plate and a metal plate are prepared, and a paste of the above-mentioned In and active metal-containing brazing material is applied to, for example, the nitride ceramics plate side. The coating thickness of the brazing material layer is preferably set to, for example, 40 μm or less so that the layer thickness of the brazing material layer after heat bonding does not become too thick in order to improve the heat resistance cycle characteristics.

Next, a metal plate is laminated and arranged on a nitride ceramics plate coated with a brazing material paste, and a temperature corresponding to the brazing material used in a nitrogen atmosphere, for example, Ag-Cu brazing material is used. For example, as described above, heat treatment is performed at a temperature of about 700 to 800 ° C., and the liquid phase of this brazing filler metal promotes the reaction between the active metal and the nitride-based ceramic plate to bond the nitride-based ceramic plate and the metal plate. To do.

Since the heat treatment for bonding is performed in a nitrogen atmosphere, it is possible to use a continuous furnace as described above, which can greatly improve mass productivity and reduce manufacturing cost. Becomes Further, the obtained joined body has high joining strength as described above and is also excellent in heat cycle characteristics.

[0022]

EXAMPLES Next, examples of the present invention will be described.

Example 1 First, it had a shape of 63 × 29 × 0.635 mm and had a thermal conductivity of 170 W.
An aluminum nitride substrate of / m K was prepared. On the other hand, a weight ratio In: Ag: Cu: Ti = 14.0: 59.0: 23.0: 4.0 of In and active metal-containing brazing filler metal was prepared, and a proper amount of resin binder and dispersion medium was added to this brazing filler metal and mixed well. An In- and Ti-containing brazing paste was prepared. This In and Ti-containing brazing paste is applied to the surface of the aluminum nitride substrate with a thickness of 30 μm.
It was screen printed so that

Next, on the coating layer of the brazing material paste,
A 0.3 mm thick phosphorous deoxidized copper plate is placed and placed in a nitrogen atmosphere at 700 ° C for 10 minutes in a continuous furnace (tunnel furnace).
Was used to bond the aluminum nitride substrate and the copper plate together to obtain the desired aluminum nitride-copper bonded substrate. This joined substrate was subjected to the characteristic evaluation described later.

Comparative Example 1 A Ti-containing brazing material containing no In and having a weight ratio of Ag: Cu: Ti = 67.7: 26.3: 6.0 was prepared and made into a paste.
It was applied to the surface of an aluminum nitride substrate made of the same material. this
A copper plate made of the same material as in Example 1 was placed on the coating layer of the Ti-containing brazing paste and heat-treated in a batch furnace at 850 ° C. for 10 minutes in a vacuum of 1 × 10 ⁻⁴ Torr. did. The obtained aluminum nitride-copper bonded substrate was subjected to the characteristic evaluation described below.

Comparative Example 2 The atmosphere during joining was set to a vacuum of 1 × 10 ^-4 Torr, and
An aluminum nitride-copper bonded substrate was produced in the same manner as in Example 1 except that the batch type furnace was used, and was subjected to the characteristic evaluation described below.

Comparative Example 3 An aluminum nitride-copper bonded substrate was produced in the same manner as in Example 1 except that the atmosphere at the time of bonding was an Ar atmosphere and a batch type furnace was used.

Comparative Example 4 As in Comparative Example 1, a Ti-containing brazing material containing no In was used to perform bonding at 850 ° C. in a nitrogen atmosphere in the same manner as in Example 1. Almost no joint was made, and it was not practically usable. Also, the bonding temperature was set to 700 as in Example 1.
When the temperature was set to ° C, no liquid phase was formed by the brazing material, and similarly, almost no joining was performed.

The characteristics of the aluminum nitride-copper bonded substrates prepared in Example 1 and Comparative Examples 1 to 3 described above were evaluated as follows. First, -40 ℃ x 30 minutes + RT x 10 minutes +
After performing a thermal cycle test (TCT) with 125 ° C × 30 minutes + RT × 10 minutes as one cycle, the peel strength was measured as the bonding strength of each bonded substrate. Also, in the same way, the thermal cycle test (T
After CT), the soundness rate η (%) was calculated as the heat resistance cycle characteristic of each bonded substrate. The soundness rate η is an index showing the heat resistance cycle characteristic, η = 100% indicates a state without cracks, and η = 0% indicates that cracks are generated on the entire surface. Figure 1 shows the relationship between the number of cycles of TCT and peel strength, and Figure 2 shows the relationship between the number of cycles of TCT and heat-resistant cycle characteristics (health rate η).

As is clear from FIG. 1, the bonded substrate according to Comparative Example 1 has a large initial bonding strength, but the deterioration of the bonding strength due to TCT is severe, whereas the aluminum nitride-copper bonded substrate according to Example 1 is It can be seen that the strength deterioration due to TCT is hardly seen. Further, it can be seen that strength characteristics almost comparable to those of the bonded substrates of Comparative Examples 2 and 3 bonded in a vacuum or an argon atmosphere are obtained.

Further, as is apparent from FIG. 2, Comparative Example 1
While the number of cracks increased with the increase in the number of TCT cycles, the aluminum nitride-copper bonded substrate according to Example 1 did not generate cracks even after 500 cycles of TCT, and the heat-resistant cycle characteristics were excellent. You can see that it has improved significantly. Further, it can be seen that even when compared with the bonded substrates of Comparative Examples 2 and 3 bonded in a vacuum or in an argon atmosphere, heat cycle characteristics that are almost comparable are obtained.

As described above, the bonded substrates according to Comparative Examples 2 and 3 have almost the same characteristics as the bonded substrate of Example 1, but the manufacturing cost is about 1.5 times that of Example 1. Moreover, since the batch type furnace is used, the mass productivity is extremely poor.

As described above, by using the brazing filler metal containing In and the active metal, high joining strength can be obtained even when joining is carried out in a nitrogen atmosphere, and the joining temperature can be further lowered. It is possible to reproducibly obtain a nitride ceramics-metal bonded body having excellent heat cycle characteristics. Then, by realizing the joining in the nitrogen atmosphere, it becomes possible to use a continuous furnace which is excellent in mass productivity and has a low manufacturing cost.

[0034]

As described above, according to the present invention, a nitride-based ceramic-metal bonded body having a high bonding strength and excellent heat resistance cycle characteristics is provided in a nitrogen atmosphere which can be used in a continuous furnace. It is possible to manufacture (join). Therefore, it is possible to greatly improve reliability and mass productivity, which are extremely important as industrial products of nitride-based ceramics-metal bonded bodies.

[Brief description of drawings]

FIG. 1 is an aluminum nitride according to an embodiment of the present invention.
It is a figure which shows the relationship between the cycle number of TCT of a copper joining substrate, and peel strength.

FIG. 2 shows aluminum nitride according to an embodiment of the present invention.
It is a figure which shows the relationship between the cycle number of TCT of a copper joining board, and a heat resistance cycle characteristic (health rate η).

Claims (2)

[Claims] 1. A bonded body comprising a nitride-based ceramic plate and a metal plate bonded to the nitride-based ceramic body via a brazing material layer, wherein the nitride-based ceramic plate and the metal plate. Is a nitride-based ceramic-metal, which is bonded in a nitrogen atmosphere through the brazing material layer containing at least one active metal selected from Ti, Zr, Hf and Nb and In. Zygote. 2. A coating layer of a brazing filler metal paste containing In and at least one active metal selected from Ti, Zr, Hf and Nb is formed on at least one surface of a nitride ceramic plate and a metal plate. And a step of laminating the nitride ceramic plate and the metal plate via the brazing material paste coating layer, firing the laminated body in a nitrogen atmosphere, and the nitride ceramic plate and the metal. A method for manufacturing a nitride-based ceramics-metal bonded body, which comprises a step of bonding with a plate.