JPH0597532A - Bonding composition - Google Patents

Abstract

PURPOSE:To provide a bonding composition permitting to efficiently produce a highly reliable ceramic-metal bonded product in a high yield in the state reduced in the generation of defeats caused by a thermal stress produced by a difference between the thermal expansion coefficients of the ceramic and the metal. CONSTITUTION:The objective bonding composition of this invention is characterized in that the composition is formed of a mixture substantially comprising 60-80wt.% of Cu, 5-15wt.% of at least one on In and Sn, 1-10wt.% of at least one of Ti and Zr, and the remaining amount substantially with Ag. 10-30wt.% of at least one of W and Mo may be added to the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding composition for use in forming a bonded body of a metal and a ceramic having a large coefficient of thermal expansion, and in particular, a highly reliable bonding with few defects such as cracks. The present invention relates to a bonding composition capable of forming a body.

[0002]

2. Description of the Related Art Conventionally, a refractory metal method or an active metal method has been widely used as a method for joining a ceramic and a metal. That is, the refractory metal method uses Mo, W,
A fine powder of refractory metal such as Mo-Mn is sintered on the surface of the ceramic to form a coating layer, and then a Ni plating layer is formed on the surface of the coating layer in order to have compatibility with the brazing material. This is a method of integrally joining with a metal.

Further, the active metal method includes Ti, Zr and Hf.
Of the periodic table represented by Group IVa element, Ag-Cu
It is a method of integrally joining ceramics and metal through a melt generated by heating to a high temperature together with Ni, Ni or the like.
Here, Ti is an element having a strong affinity for ceramics and metals, and it is possible to firmly bond oxide ceramics, nitride ceramics, carbide ceramics and various metals.

[0004]

However, in the case of forming a bonded body by the above-mentioned high melting point metal method or active metal method, both ceramics and metal members need to be heated to a high temperature. During cooling, thermal stress is generated due to the difference in coefficient of thermal expansion between the two members, and as a result, defects such as cracks in the ceramics and peeling of the joint surface are likely to occur, and the product yield and reliability tend to be reduced. It was

For example, as a bonding composition which has been conventionally generally used in the active metal method, Ag-Cu having a eutectic composition of Ag and Cu (72% Ag-28% Cu).
There is a bonding composition in which about 2% by weight of Ti as an active metal is added to a brazing material. However, when joining a metal and ceramics using this composition, it is necessary to heat to a high temperature of about 820 to 830 ° C. in order to generate a liquid phase of a eutectic compound, and the heat that acts during cooling is required. There was a defect that cracks were easily generated in the ceramics due to the stress.

It was also confirmed by the experiments by the present inventors that the bonding strength between Ti as an active metal and ceramics is extremely strong, so that cracks are likely to be induced by the concentration of thermal stress.

Therefore, in order to prevent thermal stress from impacting during cooling, a method of gradually cooling the bonded body to room temperature over several tens of hours after heating and bonding was also tried, but a long cooling time was also tried. Therefore, there is a problem that the manufacturing efficiency is significantly reduced.

The present invention has been made in order to solve the above-mentioned problems, and the number of defects caused by thermal stress due to the difference in thermal expansion coefficient between ceramics and metal is small, and the ceramic-metal bonded body is highly reliable. An object of the present invention is to provide a bonding composition capable of efficiently producing a high yield.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present inventor prepared various bonding compositions, produced a large number of bonded structures using the compositions as a bonding agent, and characterized each bonded structure. The following findings were obtained by comparing.

That is, in the case of joining ceramics and metal, by lowering the heating temperature during joining,
The thermal stress generated by the difference in thermal expansion is small, and the occurrence of cracks is small. Then, in order to lower the heating temperature at the time of joining, it is effective to add a predetermined amount of In and Sn.

In addition to forming an Ag-Cu eutectic compound by adding a Cu content higher than that of an Ag-Cu eutectic composition as compared with a conventional silver-copper brazing filler metal containing an active metal. Excessive Cu component forms a solid solution layer, and its soft elasticity exerts an action of relieving thermal stress between the ceramics and the metal, so that a bonded body with few cracks can be obtained. Further, by controlling the amount of the Ti component involved in the reaction between the ceramic and Ti by diffusing Ti into the excessive Cu phase, it is possible to prevent the formation of an extremely strong bond between the ceramic and Ti. It Therefore, the occurrence of cracks due to stress concentration is reduced.

Furthermore, by adding a predetermined amount of refractory metal having a thermal expansion coefficient close to that of ceramics such as Mo and W to the bonding composition, the stress generated at the bonding interface between the metal and the ceramics can be effectively reduced. I got the knowledge that I can.

The present invention has been completed based on the above findings. That is, the bonding composition according to the present invention has a weight ratio of 60 to 80% Cu, 5 to 15% at least one of In and Sn, and 1 to 1 at least one of Ti and Zr.
It is characterized in that it is formed by a mixture containing 10% and the balance substantially consisting of Ag.

Further, by weight ratio, Cu is 60 to 80%, at least one of W and Mo is 10 to 30%, and In and S.
It may be formed of a mixture containing at least one of n of 5 to 15%, at least one of Ti and Zr of 1 to 10%, and the balance substantially of Ag.

Cu constituting the bonding composition according to the present invention
Is a eutectic composition with Ag when heated (72 wt% Ag-28
Wt% Cu) is produced and added to firmly bond the ceramic and the metal. Conventionally commercially available Ag-Cu brazing agents have the same composition ratio as that of the eutectic composition in order to maximize the production amount of the liquid phase of the eutectic composition.
It was manufactured by mixing u powder and Ag powder.

However, one of the major features of the present invention is that the amount of Cu added is set to 60 to 80% by weight. That is, hard Ag-Cu that functions as a bonding agent
In addition to the minimum amount of Cu component necessary for producing the eutectic compound of, an excess amount of Cu component is further added, and a solid solution phase of Cu having a soft elasticity and containing this excess amount of Cu component, It is possible to absorb and absorb the thermal stress acting on the joint surface.

When the added amount of Cu is less than 60 wt%, the above-mentioned buffer action is insufficient, while the added amount is 80 w.
If it exceeds t%, the bonding strength between the metal and the ceramic will be reduced, so that the addition amount of Cu is 60 to 80 w.
It is set in the range of t%.

In and Sn are added in an amount of 5 to 15 in order to reduce the temperature at which a liquid phase eutectic compound is formed in the bonding composition.
% By weight. That is, in the conventional silver-copper brazing material having a eutectic composition, it was necessary to heat to a high temperature of about 820 ° C. at the time of bonding, but in the bonding composition according to the present invention, a liquid containing In and / or Sn was used. Due to the effect of reducing the phase generation temperature, the heating temperature at the time of joining can be reduced to about 700 to 750 ° C. Therefore, the cooling temperature width in the cooling step after heating and joining is narrow, and cracks generated in the joined body can be significantly reduced.

If the addition amount of at least one of In and Sn is less than 5 wt%, the effect of reducing the heating temperature is insufficient, while if the addition amount is an excessive amount exceeding 15 wt%, the metal content is increased. Causes a decrease in the bonding strength between the and ceramics.

Further, Ti and Zr act as an active metal for enhancing the wettability of the bonding composition with respect to the ceramics, and in order to enhance the bonding strength between the ceramics and the metal, 1
It is added in the range of 10 wt%. By using the bonding composition containing an active metal such as Ti described above,
The metal material can be directly bonded to the ceramics without forming the Ni plating layer as in the conventional method.

The addition amount of the active metal such as Ti is 1 wt%
If the amount is less than the above, the effect of improving the wettability will be insufficient, while if the amount added exceeds 10 wt%, the Ag-Cu brazing material will flow easily, and in particular, a conductor circuit pattern will be formed. When the ceramic circuit board is manufactured by joining the metal plate and the ceramic board, a short circuit easily occurs due to the flow of the brazing material, and the operation reliability of the circuit board deteriorates.

W and Mo are effective components for relaxing stress in the joint between ceramics and metal, and are added in an amount of 10 to 30% by weight. That is, by adding high melting point metals W and Mo having a thermal expansion coefficient relatively close to that of ceramics to the bonding composition, it is possible to form a bonding layer having a thermal expansion coefficient intermediate between those of the metal and the ceramic. It is possible to exert a thermal stress relaxation action on the bonding layer between the ceramic and the ceramic. Therefore, it is possible to obtain a ceramic / metal bonded body having high bonding strength and excellent heat cycle characteristics.

When the amount of addition of at least one of the above W and Mo is less than 10 wt%, the stress relaxation effect in the bonding layer becomes insufficient, while when the amount added exceeds 30 wt%, it becomes excessive. However, the joint strength decreases and the original heat transfer characteristics and insulation characteristics of ceramics are impaired. Therefore, the added amounts of W and Mo are set in the range of 10 to 30% by weight.

The above-mentioned bonding composition may be used by adding a small amount of binder and then press-molding it to interpose it on the bonding surface in the form of a thin plate, but usually it is a mixture adjusted to the above-mentioned predetermined composition. The body is kneaded with a binder solution prepared by dissolving ethyl cellulose or the like as a binder in terpineol or the like as a solvent to prepare a paste to be used.

Aluminum nitride (AlN), alumina (Al ₂ O ₃ ) or the like is used as the ceramic material, while Cu, Fe, Cr or Fe-N is used as the metal material.
An i alloy or the like is used. Then, in a state where the thin plate-shaped or paste-shaped bonding composition is interposed on the bonding surface between the metal material and the ceramic material, in vacuum or in an inert gas atmosphere such as N ₂ or Ar, or in a non-oxidizing atmosphere. By heating at a temperature of 700 to 750 ° C. for 10 to 30 minutes, a joined body in which ceramics and metal are firmly integrated is formed. Since Ti contained in the composition easily reacts with hydrogen, it is not preferable to use H ₂ gas as the heating atmosphere gas.

[0026]

Since the bonding composition having the above structure contains In and Sn, the liquid phase generation temperature is A
The temperature is lower than that of the g-Cu brazing material, the heating and joining temperature can be suppressed to be low, and the occurrence of cracks due to the difference in thermal expansion coefficient between the metal and the ceramics can be effectively prevented in the cooling process, and the reliability is improved. A high bonded body can be obtained.

Further, as compared with the conventional Ag—Cu brazing filler metal, since Cu is contained in excess, Cu which is rich in soft elasticity is used.
A phase is formed on the joint surface, and a buffering effect is absorbed to absorb thermal stress acting on the joint surface. Therefore, a bonded body having excellent heat cycle characteristics can be obtained with less peeling between metal and ceramics.

[0028]

EXAMPLES Next, one example of the bonding composition according to the present invention will be described with an example applied to the following bonded body.

[0029] 2% of Ti powder in a weight ratio as in Example 1 Example 1, Ag powder 2
20 parts by weight of a binder solution prepared by dissolving ethyl cellulose as a binder in terpineol as a solvent was added to 100 parts by weight of a powder mixture containing 4%, 60% Cu powder and 14% In powder, and mixed. After mixing with a machine, the mixture was kneaded with a three-stage roll to prepare a paste-like bonding composition.

On the other hand, the paste-like bonding composition is interposed on both sides of a ceramic substrate made of aluminum nitride (AlN) having a thickness of 0.635 mm, and a copper circuit board having a thickness of 0.3 mm is arranged in contact with each other to form three layers. A large number of laminates having a structure were formed.

Next, each of the obtained laminated bodies was placed in a heating furnace, the inside of the furnace was adjusted to a vacuum degree of 10 ^-4 Torr, and then the temperature was adjusted to 73.
The AlN ceramic substrate and the copper circuit board were integrally joined by heating at 0 ° C. for 10 minutes to obtain a large number of joined bodies.

Example 2 As Example 2, a powder mixture containing 2% by weight of Ti powder, 60% by weight of Cu powder, 10% by weight of W powder, 10% by weight of In powder and 18% by weight of Ag powder was used. Except for the above, the treatment was performed under exactly the same treatment conditions as in Example 1, and a large number of joined bodies having the same dimensions were manufactured.

Comparative Example On the other hand, as a comparative example, a eutectic composition (72 wt% Ag-28
2% by weight of Ti powder was added to a commercially available Ag—Cu brazing filler metal having a wt% Cu), and a thin plate-like bonding composition having a thickness of 0.3 mm, which was pressure-molded, was prepared in Example 1 and made of an AlN ceramic substrate. A large number of laminates were prepared by interposing between the copper foil and the copper circuit board. Then, each of the obtained laminates was vacuumed (10
^-4 Torr) at a temperature of 830 ° C. for 10 minutes to produce a large number of bonded joints of Comparative Examples. Here, heating temperature (830 ℃)
Is the working temperature of the Ag-Cu eutectic compound.

After the heat-bonded joints of Examples 1 and 2 and Comparative Example were cooled to room temperature, the surface and cross section of the ceramic substrate were inspected by naked eyes and a penetrant flaw detection method to find defects such as cracks and peeling. Was measured. As a result, in the joined body according to Example 1, 0.6%,
It was 0% in Example 2 but was 21% in the joined body of Comparative Example.
Met.

That is, in Example 1, as compared with the case of the comparative example, since the heating temperature at the time of joining is lower by about 100 ° C., the thermal stress acting on the joining surface at the time of cooling is relatively small and cracks are generated. Less is. Since Cu having higher elasticity is added in an excessive amount as compared with the conventional Ag—Cu brazing filler metal, the thermal stress acting on the joint surface is buffered, and as a result, a more sound joint can be obtained. Further, since a part of Ti diffuses in an excessive amount of Cu, the reactivity of Ti is appropriately suppressed and controlled. Therefore, thermal stress does not concentrate on the portion strongly joined by TiN, and cracks are less likely to occur.

Further, in Example 2, since W having a coefficient of thermal expansion close to that of ceramics is added, the coefficient of thermal expansion between the bonding layer and the ceramic substrate can be approximated, and the thermal stress due to the difference in coefficient of thermal expansion can be reduced. It was possible to reduce the number of defects and almost eliminate the defects of the ceramic substrate.

Further, in order to evaluate the durability and reliability of each joined body, each joined body of Examples 1 and 2 and Comparative Example was used and heated in the range of -65 ° C to + 150 ° C, and subsequently +150. When the heat cycle test (TCT) in which the operation of cooling to 650C to -65C was set as one cycle was repeatedly performed, the joined bodies of Examples 1 and 2 showed microcracks, cracks, peeling, etc. even after 1000 cycles. The occurrence rate of defects was 0%. On the other hand, in the bonded body of the comparative example, 1
After 00 cycles, cracks occurred at a rate of 45%.

[0038]

As described above, since the bonding composition according to the present invention contains In and Sn, the liquidus formation temperature is lower than that of the conventional Ag-Cu brazing material, It is possible to suppress the heating and joining temperature to a low level, effectively prevent the occurrence of cracks due to the difference in thermal expansion coefficient between the metal and the ceramic in the cooling step, and obtain a highly reliable joined body.

Further, as compared with the conventional Ag-Cu brazing material, since Cu is contained in excess, Cu which is rich in soft elasticity is used.
A phase is formed on the joint surface, and a buffering effect is absorbed to absorb thermal stress acting on the joint surface. Therefore, a bonded body having excellent heat cycle characteristics can be obtained with less peeling between metal and ceramics.

Front page continuation (72) Inventor Takayuki Naba 4-4, 2 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Corporation Keihin Office

Claims (2)

[Claims] 1. A Cu content of 60 to 80%, at least one of In and Sn of 5 to 15% and at least one of Ti and Zr of 1 to 10% by weight, with the balance being substantially Ag.
A bonding composition formed of a mixture of 2. A weight ratio of Cu is 60 to 80%, at least one of W and Mo is 10 to 30%, at least one of In and Sn is 5 to 15%, and at least one of Ti and Zr is 1. A bonding composition, characterized in that it is contained in an amount of 10% by weight and the balance is substantially Ag.