JP2590255B2 - Copper material with good bondability with ceramics - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a copper material having good bondability with ceramics.

[Prior art] A hybrid body made of ceramic and copper material is hybrid
It is often used for electronic components such as ICs. Conventionally, these bondings are performed by printing a metal paste containing an organic binder such as molybdenum or tungsten on ceramics, and then heating the metal paste in an atmosphere furnace to metallize the metal paste to form a metallized layer. After plating, it has been performed by a complicated method including various steps such as joining a copper material by soldering.

On the other hand, a method including a simple process of directly bonding ceramics and copper by generating copper oxide (Cu ₂ O) at a bonding interface between the ceramics and the copper material has been developed and attracted attention. In this method, the ceramics and the copper material are simply brought into direct contact with each other by heat treatment in a state where they are in direct contact with each other. As can be understood from the binary phase diagram of copper-oxygen, a Cu ₂ O liquid phase can be formed by heating to a temperature of 1065 ° C. or more and supplying oxygen to the contact interface. Then, the ceramic and the copper material are directly joined. There are two methods for supplying oxygen: a method using oxygen in copper (using tough pitch copper) and a method using oxygen present in the atmosphere (using oxygen-free copper). A joining method using tough pitch copper is generally used. ing.

Although this direct bonding method has simpler steps and various advantages as compared with the previous bonding method, there are still some problems to be solved.

This is because copper is heated to near the melting point and held, so the melting point is significantly reduced locally due to impurity elements such as S, Fe, Si, Ag, Pb, and Ni contained around 30 ppm, and the surface of the copper material (The surface on which the element is mounted) may be extremely roughened, or the same local melting point reduction may occur at the contact surface, resulting in a decrease in the area of wetting and a failure to obtain good bonding. is there.

For this reason, there have been disadvantages such as that the joining yield is remarkably reduced, leading to an increase in cost, and that the copper surface becomes rough, making it impossible to mount elements.

Therefore, the tough pitch copper used, the content of the impurity elements S, Fe, Si, Ag, Pb, Ni, etc. each 10ppm
It is necessary to make the following, and industrially, there are very severe restrictions such as furnace materials and operating conditions of the melting furnace.

[Problems to be Solved by the Invention] The present invention has been made in view of the prior art described above, and an object of the present invention is to provide a ceramic and a ceramic that do not need to strictly control impurities such as S. It is an object of the present invention to provide a copper material having good bonding properties.

[Means for Solving the Problems] The copper material of the present invention has an oxygen concentration of 180 to 300 ppm, with the balance being 1 to 1 tough pitch copper comprising Cu and unavoidable impurities.
This is a copper material having a good bonding property with ceramics, which is provided with a Cu layer having a purity of 99.95% by weight or more of 20 μm.

[Operation] A copper material having good bonding properties with the ceramic according to the present invention will be described in detail below.

Oxygen is an essential element for direct metal bonding with ceramics, and if the concentration is less than 180 ppm, the supply of oxygen at the bonding interface is insufficient, resulting in poor bonding. At a concentration exceeding 300 ppm, the bondability is good,
Even if a high-purity Cu layer is applied in a thickness of 1 to 20 μm, the surface on which the element is mounted becomes rough (excessive O ₂ is collected at the grain boundary, and the surface roughness becomes large). Therefore, the oxygen concentration is set to 180 to 300 ppm.

The high-purity Cu layer, at the bonding interface with the ceramic,
It has the effect of suppressing the decrease in local melting point due to impurity elements by being inevitably mixed, allowing the Cu ₂ O liquid phase at the interface to sufficiently exist, and obtaining a good bonding interface.

If the thickness of the high-purity Cu layer is less than 1 μm, the effect is small, and if it exceeds 20 μm, the bondability is reduced. Therefore, the thickness of the high-purity Cu layer is set to 1 to 20 μm.

When a high-purity Cu layer is not provided, the surface of the tough pitch on which the element is mounted becomes uneven due to the formation of a Cu ₂ O liquid phase, and the surface roughness becomes extremely large (Rmax 10 μm or more).
However, by providing a high-purity Cu layer of 1 to 20 μm, the surface becomes relatively smooth, which leads to stable quality of device mounting. In this case, the thickness of the high-purity Cu layer is preferably as thick as possible, but 1 to 20 μm is appropriate in view of the bonding property with ceramics, surface roughness and cost.

The high-purity Cu layer has a Cu concentration of 99.95% or more, and may be provided, for example, by plating. In the case of plating, the plating may be performed as it is, but rolling and sintering may be performed after Cu plating in order to further improve the smoothness of the material surface and to remove the urgent gas.

The type of ceramics to be joined in the present invention is not particularly limited, but, for example, Al ₂ O ₃ , AlO ₃
• SiO _{2 and the} like, and these ceramics may be films formed on an appropriate basis.

[Examples] A copper material having good bonding properties with ceramics according to the present invention will be described in detail below by way of its implementation.

A 0.3 mmt material of tough pitch copper having the components and component ratios shown in Table 1 was used as a test material.

Ceramics are alumina 1.5mmt × 30mmw × 500mml
Was used.

The copper material to be joined was prepared in advance by etching to 0.3 mm × 25 mm × 45 mm. Cu plating was performed in a copper sulfate plating bath before etching.

Bonding tests, a ceramic stacked copper material, N ₂ gas
After a heat treatment at 1070 ° C. × 10 minutes in a 100% atmosphere (dew point −50 ° C.), an appearance inspection (× 40) was performed, and the bonding property was evaluated based on the presence or absence of blisters. The surface condition was observed by measuring the surface roughness of the copper material surface and using a scanning electron microscope.

 Table 2 shows the test conditions and test results.

FIGS. 1 (a) and 1 (b) show No. 1 (Example) and No. 8 (Comparative Example) as representative examples of the results of scanning electron microscope observation of the surface of the copper material bonded to the ceramics. Show.

As is clear from Table 2 and FIG. 1, No. 1 to No. 6
(Example) shows that the bondability with ceramics is better than that of Comparative Example, and the surface of the copper material on which elements are mounted is also Rmax × 10
It was excellent in smoothness of not more than μm.

On the other hand, No. 7 and No. 8 (Comparative Example) did not have the Cu plating treatment, generated many blisters, and had irregularities on the copper material surface.

In Nos. 9, 10, 11, and 12 (Comparative Examples), regardless of the presence or absence of plating, the O ₂ concentration exceeded 300 ppm and the occurrence of blisters was small, but the surface roughness was large.

In Nos. 13, 14, and 15 (Comparative Examples), the O ₂ concentration was less than 180 ppm, and the surface roughness of the copper material surface was good regardless of the presence or absence of Cu plating, but there was a problem in the bondability.

No. 16 (comparative example) is a tough pitch copper with impurity control, and the bonding property and surface roughness are the same as those of the present invention. To do so, a considerable amount of equipment is required, leading to an increase in cost and a decrease in productivity.

[Effects of the Invention] According to the present invention, it is not necessary to control the limit of impurities, and by providing a Cu plating layer on conventional tough pitch copper, it is possible to provide a copper material having good bondability with ceramics. For example, ceramics as electronic components
This greatly contributes to the improvement of the quality and productivity of the copper composite material.

[Brief description of the drawings]

FIG. 1 (a) is a scanning electron micrograph showing the state of crystal grains on the surface of a copper material directly bonded to alumina ceramics using the copper material of No. 1 of the present invention. FIG. 1 (b) shows Comparative Example No. 8
3 is a scanning electron micrograph showing the state of crystal grains on the surface of a copper material directly bonded to an alumina ceramic using the copper material of FIG.

Claims (1)

(57) [Claims] An oxygen concentration of 180 to 300 ppm, and the balance is Cu
1 to 20 μm for tough pitch copper consisting of unavoidable impurities
A copper material with good bondability to ceramics, characterized by having a Cu layer having a purity of 99.95% by weight or more.