JP3095490B2 - Ceramic-metal joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joined body of a ceramic member and a metal member, and more particularly to a joined body of a ceramic member and a metal member which is excellent in cold-heat cycle resistance.

[0002]

2. Description of the Related Art In general, nitride ceramic materials are
It has features such as light weight and high hardness, excellent electrical insulation, excellent heat resistance and corrosion resistance, and is utilized as a structural material, a material for electric parts, etc. by utilizing these characteristics. By the way, when a nitride-based ceramic material is used as a structural material, for example, the ceramic material is a brittle material by nature, so that it is generally used by bonding with a metal material. On the other hand, by using the high electrical insulation properties of the nitride ceramic material, when used as a mounting substrate for electronic components, for example, bonding with a metal is performed for the purpose of forming an electric circuit. I have. Thus, when considering the practical use of nitride ceramic materials,
Joining with metal materials is an important technology.

[0003] As a method of joining the nitride-based ceramic member and the metal member as described above, a method using a high melting point metal such as Mo or W or an active metal such as an IVa group element or a Va group element has been used. Are known, and among them, the active metal method is frequently used because high strength, high sealing property, high reliability and the like can be obtained.

The active metal method is a joining method utilizing the fact that metal elements such as Ti, Zr, and Nb are easily wetted and reacted with a nitride-based ceramic material. It is used as a brazing method using a brazing material that has been used, a method of interposing an active metal foil or powder between a nitride ceramic member and a metal member, and heating and joining (solid phase diffusion joining). Also, an active metal is directly used as a metal member to be joined.
Generally, active metals such as Ti are added to the eutectic brazing material of Cu and Ag (Ag: 72wt%) from the viewpoint of easy handling and processing.
This is interposed between the ceramic member and the metal member,
A method of joining by heat treatment at an appropriate temperature is often used.

[0005]

By the way, high bonding strength is required for the joining parts of the nitride ceramic member and the metal member, but the thermal expansion coefficient of the ceramic material is smaller than that of the metal material. There is a strong demand to suppress the occurrence of defects caused by this difference in thermal expansion.
In other words, when a ceramic material and a metal material having significantly different coefficients of thermal expansion are joined to each other, a residual stress due to a difference in thermal expansion occurs in a cooling process after the joining, and a joint strength with an external stress significantly reduces the joining strength, In addition, cracks are generated from the maximum stress point due to the cooling process after the joining or the addition of the cooling / heating cycle, and further, the ceramic material is broken.

[0006] In view of such a point, in the above-mentioned joining method using the active metal brazing material, although a joined body having a relatively high joining strength can be obtained, sufficient joining reliability such as cooling and heating cycles can be obtained. At present, it has not been possible to obtain a conjugate having good reproducibility. For example, a substrate obtained by bonding a copper plate or the like on a nitride-based ceramic member using an active metal brazing material is used as a mounting substrate for a semiconductor element or the like. Since the amount of heat radiation from the semiconductor element has increased dramatically, and the amount of heat transferred to the mounting substrate has increased,
There is a strong demand for improvement in reliability for cooling and heating cycles and the like.

The present invention has been made in order to solve such problems, and provides a ceramic-metal bonded body which satisfies high bonding strength and has high reliability against the application of a cooling / heating cycle or the like. It is intended to be.

[0008]

The ceramic-metal joined body of the present invention comprises a nitride-based ceramic member,
i, see contains at least one active metal selected from Zr and Nb, via a Ag-Cu-based brazing material layer containing 15～35Wt% of Cu, and a metal member bonded to the nitride-based ceramic member Wherein the active metal segregated layer having a thickness of 7 μm or less is continuously present at the bonding interface on the nitride-based ceramic member side.

Examples of the nitride ceramic member used in the present invention include aluminum nitride, silicon nitride, sialon and the like. The material properties of the nitride ceramic member itself are not particularly limited, but it is particularly preferable to use one having a fracture toughness value K _IC of 4.5 MPa · m ^1/2 or more. The ceramic-metal joined body of the present invention is intended to improve the cold / heat cycle resistance and the joining strength by the structure of the brazing material layer itself, and has a fracture toughness value K _IC of 4.5 MPa · m ^1/2 or more. By using the nitride-based ceramic member, it is possible to further improve the cold-heat cycle resistance. That is, if the fracture toughness value K _{IC of} the nitride-based ceramic member is 4.5 MPa · m ^1/2 or more, cracks may occur in the nitride-based ceramic member when a thermal cycle or the like is applied to the joined body. Is suppressed.

The metal member may be appropriately selected from various metal materials according to the application. Examples of the structural material include a steel material, a heat-resistant alloy, a cemented carbide, and the like. Examples thereof include Cu, Cu alloy, Ni, Ni alloy, W, and Mo.

[0011] The ceramic-metal bonded body of the present invention is characterized in that the above-mentioned nitride ceramic member and metal member are formed by changing the eutectic composition of Ag-Cu (72 wt% Ag-28 wt% Cu) or a composition in the vicinity thereof. It is mainly joined with an Ag-Cu brazing material containing an appropriate amount of at least one active metal selected from Ti, Zr and Nb.

In the ceramic-metal bonded body of the present invention, the active metal in the brazing material is segregated at the bonding interface on the side of the nitride-based ceramic member, and the segregation layer is basically formed of the active metal. It is mainly composed of nitride. It is important that the segregation layer of the active metal is formed continuously at the bonding interface, so that the bonding strength and the thermal cycling resistance can be improved.

As described above, the active metal segregation layer is mainly composed of a nitride formed by a reaction between the active metal in the brazing material and nitrogen in the ceramic member. By continuously forming such a reaction layer at the bonding interface on the nitride ceramic member side, high bonding strength can be stably obtained, and the segregation layer of the active metal functions as a stress relaxation layer. Cracks can be suppressed from occurring in the nitride-based ceramic member due to the addition of a cycle or the like. The suppression of this crack, as described above,
The use of a nitride ceramic member having a fracture toughness value K _IC of 4.5 MPa · m ^1/2 or more is more effective.

However, the nitride of an active metal such as TiN itself is a brittle material, and if the thickness is too large, there is a risk that the nitride may be a starting point of cracks. Therefore, the thickness of the active metal segregation layer is 7 μm or less. It shall be the. Further, if the layer thickness is too small, it is difficult to form the layer uniformly, so that the thickness is preferably 4 μm or more. Therefore, the thickness of the active metal segregation layer is preferably in the range of 4 μm to 7 μm. The segregation layer performs its function if it is formed uniformly and continuously at the bonding interface.
m.

Further, since the nitride of the active metal is originally a brittle material as described above, the compound mainly constituting the above-mentioned segregation layer is formed as a composite compound further containing the other material constituting the ceramic member. It is possible to further improve the cooling / heating cycle characteristics. For example, if the ceramic member is an aluminum nitride sintered body, it is preferable to use a ternary compound of active metal-aluminum-nitrogen. Thus, for example, by containing aluminum, the ductility of the compound is increased, and it is possible to prevent the segregation layer from becoming a starting point of cracks.

As described above, the Ag-Cu-based brazing material used in the present invention mainly has a eutectic composition of Ag-Cu or a composition in the vicinity thereof, and has at least two components selected from Ti, Zr and Nb. It contains a suitable amount of various active metals. The active metal is activated at a heat treatment temperature (joining temperature) and reacts with the nitride-based ceramic member to form, for example, a nitride, which contributes to the improvement of the joint strength and the thermal cycling resistance. However, if added in an excessively large amount, although the joining strength is increased, it may cause cracks when a cooling / heating cycle is added. Therefore, it is preferably less than 10% by weight. On the other hand, if the amount of the active metal is too small, sufficient bonding strength cannot be obtained, so that the content is preferably 1% by weight or more. In addition, Ag-Cu
The alloy shall basically satisfy the eutectic composition,
A similar effect can be obtained if the Cu content in all brazing filler metal components is about 15% by weight to 35% by weight.

The ceramic-metal bonded body of the present invention is manufactured, for example, as follows. First, a nitride-based ceramic member and a metal member are prepared, and a paste of an Ag-Cu-based brazing material containing an active metal as described above is applied to the nitride-based ceramic member side. Here, as specified in the present invention, in order to uniformly form a layer in which the active metal is segregated on the bonding interface on the nitride ceramic member side, a brazing material paste is applied to the nitride ceramic member side. is important. When the brazing material paste is applied to the metal member side, a small amount of oxygen adheres to the surface of the applied paste layer before the joining process, and this oxygen transfers the active metal to the nitride ceramic member side. Hinder. Therefore, it is difficult to uniformly form a layer in which the active metal is segregated. In the conventional method, it was common to apply a brazing material paste to the metal member side. The use form of the above-mentioned Ag-Cu-based brazing material is preferably used as a paste containing Ag, Cu and an active metal, but is not necessarily used in the form of a foil laminate. is not.

Next, the nitride-based ceramic member coated with the brazing material paste and the metal member are laminated, and in a vacuum or an inert atmosphere such as a nitrogen atmosphere, at a temperature at which the Ag-Cu eutectic is formed. Heat treatment is performed to join the nitride ceramic member and the metal member by utilizing the eutectic liquid phase and the reaction between the active metal and the ceramic member.

At this time, the bonding temperature is generally 800 ° C.
The bonding time (heating time) is about 5 minutes to 15 minutes at about 900 ° C., but in order to uniformly segregate the active metal into the nitride-based ceramic member, about 830 ° C. to 870 ° C. Preferably, the time is about 10 minutes. Further, as a condition for segregating the active metal, the degree of vacuum is set to 10 ^-4 To
rr or less.

In order to make the compound constituting the segregation layer into a complex compound such as active metal-aluminum-nitrogen, the compound is treated at a high temperature and for a relatively short time, or at a medium temperature or higher for a long time. Is preferred. As described above, by increasing the reactivity at the time of bonding, after the active metal reacts with nitrogen, aluminum or the like is easily dissolved in the active metal and nitrogen, and a composite compound is easily formed.

[0021]

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

Example 1 First, a plate-like sintered aluminum nitride having a thickness of 0.8 mmt was prepared as a nitride-based ceramic member, and a copper plate (oxygen-free copper) having a thickness of 0.3 mmt was prepared as a metal member. On the other hand, a brazing filler metal having a weight ratio of Ag: Cu: Ti = 70.6: 27.4: 2.0 was prepared, and an appropriate amount of a resin binder and a dispersion medium were added to the brazing filler metal and mixed sufficiently to prepare a bonding paste.

Next, as shown in FIG. 1A, the bonding paste 2 is screen-printed on one main surface 1a of the aluminum nitride sintered body 1 and dried, and then the bonding paste 2 is formed. The copper plate 3 was laminated and arranged on the coating layer of the above. Thereafter, the above-mentioned laminate is placed in a vacuum of 1 × 10 ⁻⁴ Torr or less at 850 ° C. × 10 minutes (heating rate: 10 ° C./min, cooling: furnace cooling)
1B, the aluminum nitride sintered body 1 and the copper plate 3 are joined via the brazing material layer 4 to obtain the desired ceramic-metal joint 5 as shown in FIG. Was.

Comparative Example 1 A ceramic-metal joined body was produced under the same conditions as in Example 1 except that the joining paste was applied to the copper plate side.

Comparative Example 2 A brazing material having a weight ratio of Ag: Cu: Ti = 27.4: 70.6: 2.0 was prepared, and a bonding paste was prepared in the same manner as in Example 1. Then, a ceramic-metal joined body was produced under the same conditions as in Example 1 except that the joining paste was applied to the copper plate side.

Each of the ceramic-metal joints (aluminum nitride) produced in Example 1 and Comparative Examples 1 and 2 was manufactured.
Copper) was analyzed by EPMA. FIG. 2 schematically shows the result of the analysis by EPMA of Example 1. FIG. 3 schematically shows the result of analysis of Comparative Example 2 by EPMA. As is clear from FIG. 2, in the ceramic-metal bonded body according to Example 1, a layer in which Ti segregated was continuously formed at the bonding interface on the aluminum nitride side. The thickness of the Ti segregation layer was about 4.5 μm. Further, it was confirmed by X-ray diffraction that this segregation layer of Ti was mainly composed of TiN. On the other hand, in the ceramic-metal joined body according to Comparative Example 2, as shown in FIG.
A layer in which Ti segregated was formed at the bonding interface on the aluminum nitride side. However, the Ti segregation layer had a discontinuous portion, and its thickness was about 3 μm. In the ceramic-metal bonded body according to Comparative Example 1, the thickness of the segregation layer of Ti was further reduced to about 1.5 μm, and the formation state was discontinuous.

Further, at the bonding interface of each ceramic-metal bonded body, 10 μm × 10 μm centered on the segregation layer of Ti.
When the component ratio of the area of was analyzed by EPMA, Table 1
The result as shown in FIG.

[0028]

[Table 1] The analysis results shown in Table 1 also indicate that the ceramics of Example 1
The metal bonded body supports that Ti is segregated at the aluminum nitride-side interface.

Next, the characteristics of each of the ceramic-metal joined bodies produced in Example 1 and Comparative Examples 1 and 2 were evaluated as follows. First, a thermal cycle test (TCT) was performed on each ceramic-metal joint. TCT is -40
One cycle consisted of 30 ° C x 30 minutes + RT x 10 minutes + 125 ° C x 30 minutes + RT x 10 minutes. The evaluation method after TCT was performed by measuring the peel strength of the copper plate and checking for the presence or absence of cracks. FIG. 4 shows the relationship between the number of TCT cycles, the peel strength, and the occurrence of cracks. As is clear from FIG. 4, the ceramic-metal bonded body according to Example 1 has an extremely large initial bonding strength, a small reduction in strength even when a cooling / heating cycle is applied, and a crack by TCT of up to 100 cycles. Was not found. On the other hand, the ceramic-metal joints according to Comparative Examples 1 and 2 each had a low initial bonding strength, cracks occurred in about 50 cycles, and a large reduction in strength thereafter. .

Example 2 The bonding temperature condition in Example 1 was changed from 850 ° C. × 10 minutes to 85 ° C.
A ceramic-metal joined body was produced under the same conditions as in Example 1 except that the temperature was changed to 0 ° C. × 30 minutes.

When the interface analysis of this ceramic-metal bonded body was performed by EPMA, a layer in which Ti segregated was continuously formed at the bonding interface on the aluminum nitride side (the layer thickness was equivalent to that in Example 1). , Al
Was diffused, and it was confirmed that a Ti-Al-N compound was formed. In the ceramic-metal joined body according to Example 1, it was confirmed that Al was diffused into the segregation layer of Ti, but the quantity of the ceramic-metal joined body according to Example 2 was larger. .

When the occurrence of cracks in the ceramic-metal joined body according to Example 2 was confirmed by TCT, no crack was observed up to 300 cycles, and it was found that the ceramics-metal joined body was excellent in the thermal cycling resistance. The measured values of the peel strength were almost the same as those in Example 1.

Examples 3 to 5 The fracture toughness values K _IC were 4.7 MPa · m ^1/2 and 4.1 MPa · m, respectively.
Three kinds of aluminum nitride sintered bodies of ^1/2 and 4.0 MPa · m ^1/2 were prepared, and each of them was used under the same conditions as in Example 1 to obtain a ceramic-metal joined body (Examples 3 to 4).
5) was produced.

The peel strength of these three types of ceramic-metal joints was measured, and TCT under the same conditions as in Example 1 was performed for 100 cycles, and the presence or absence of a fine crack of the aluminum nitride sintered body was determined as follows. Confirmed by. First, the copper plate and the brazing material layer were removed by etching, and the presence or absence of a fine crack on the surface of the aluminum nitride sintered body was determined by a fluorescent penetrant inspection (PT) inspection.

As a result, the initial measured values of the peel strength were almost the same for all the ceramic-metal joints as in Example 1, but in Example 3 (AlN: K _IC = 4.7 MPa · m ^1/2). )
No crack was observed in the ceramic-metal joined body of Example 1 even after 100 cycles of TCT, whereas fine cracks occurred in other ceramic-metal joined bodies (Examples 4 and 5).

[0036]

As described above, according to the ceramic-metal bonded body of the present invention, a segregation layer of an active metal, which is a reaction layer, is continuously formed at an appropriate thickness at the bonding interface on the nitride ceramic member side. As a result, a high bonding strength can be stably obtained, and the occurrence of cracks in the nitride-based ceramic member due to the addition of a thermal cycle can be suppressed. Therefore, it is possible to provide a ceramic-metal bonded body having high bonding strength and excellent reliability with respect to a thermal cycle with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of a ceramic-metal joined body in one embodiment of the present invention.

FIG. 2 is a view schematically showing an EPMA analysis result of a bonding interface of a ceramic-metal bonded body according to one embodiment of the present invention.

FIG. 3 is a diagram schematically showing an EPMA analysis result of a bonding interface of a ceramic-metal bonded body shown as a comparison with the present invention.

FIG. 4 is a diagram showing the relationship between the number of TCT cycles and the peel strength of the ceramic-metal joined body according to one embodiment of the present invention, in comparison with a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sintered aluminum nitride 2 ... Paste for joining 3 ... Copper plate 4 ... Brazing material layer 5 ... Ceramic-metal joined body

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-18087 (JP, A) JP-A-2-149478 (JP, A) JP-A-64-65859 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) C04B 37/02

Claims (4)

(57) [Claims] 1. A nitride ceramic member, Ti, Zr
And at least one active metal selected from Nb and Nb.
And a metal member joined to the nitride-based ceramic member via an Ag-Cu-based brazing material layer containing 15 to 35 wt% of Cu. Has a thickness of 7
A ceramic-metal joined body , wherein a layer in which the active metal having a thickness of not more than μm is continuously present. 2. The ceramic-metal bonded body according to claim 1, wherein the thickness of the active metal segregation layer is in a range of 4 to 7 μm. 3. The ceramic-metal joined body according to claim 2, wherein the segregation layer of the active metal is mainly composed of a nitride of the active metal.
Metal joint. 4. The ceramic-metal joined body according to claim 1, wherein said nitride-based ceramic member is made of an aluminum nitride sintered body, and said active metal segregation layer is formed of said active metal, aluminum and nitrogen. A ceramic-metal joined body comprising the compound of the above as a constituent element.