JPH069906B2 - Composite material consisting of graphite and copper or copper alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite material composed of graphite and copper or a copper alloy used in, for example, an X-ray target or a sputtering target.

[Conventional technology]

The coefficients of thermal expansion of copper and copper alloys are greatly different from that of graphite. The coefficient of linear expansion of copper and copper alloys is 18-20 × 10 ^-6
On the other hand, the linear expansion coefficient of graphite is 3 to 7 × 10 ⁻⁶ . Generally, in the range where the coefficient of thermal expansion does not pose a practical problem in brazing or diffusion bonding, the difference in linear expansion coefficient between the two is 10 × 10 ^-6.
If it is smaller.

For this reason, when the two are joined by hard brazing or diffusion joining, the shrinkage rate of the copper plate is larger in the cooling process after joining, so that a large dimensional difference occurs between the two and a large residual stress occurs, and the graphite, which is a brittle material, The board may break.

For example, as shown in FIG. 9, it is assumed that when the graphite plate 1 and the copper plate 2 are stacked in the thickness direction, they are diffusion bonded (or hard brazed) at a high temperature. In this case, the copper plate 2 shrinks relatively to the graphite plate 1 in the cooling process after joining. Therefore, when the difference between the temperature at the time of joining and the temperature at the time of cooling is large, the graphite plate 1 and the copper plate 2 bend as shown by the imaginary line in FIG. 9, and in extreme cases, as shown in FIG. Radial cracks 3 are generated in the graphite plate 1. Therefore, the composite material composed of the graphite plate 1 and the copper plate 2 may be joined with a small test piece in some cases, but the graphite plate 1 has a practical size.
Is often destroyed.

Therefore, at present, they are fastened together by mechanical means, joined by a resin adhesive, or joined by soft brazing of indium, solder or the like at a relatively low temperature.

[Problems to be solved by the invention]

However, mechanical fastening cannot locally increase the fastening force because the load is locally applied. on the other hand,
In the case of joining with a resin-based adhesive or soft brazing, the heat resistance of the joined portion is inferior, so there is a problem with those used at high temperatures such as an X-ray target and a sputtering target.
Moreover, when used in a vacuum or a special atmosphere, an impurity gas may be generated from the adhesive.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 60-187546, it has been proposed to interpose a Ti layer and a Ni layer between a graphite plate and a copper plate, but according to the study by the present inventors, ,
When using Ti and Ni for the insert plate, if the composite material is large to some extent, the graphite is likely to be damaged in the cooling process after joining, and thus it may not be applicable to a product having a realistic size. It was also found that the cause of graphite breakage when such an insert plate made of Ti or Ni is likely to be due to the difference between the coefficient of thermal expansion of the insert plate and the coefficient of thermal expansion of graphite.

Therefore, an object of the present invention is to obtain a composite material which has high heat resistance and is less likely to cause breakage of graphite.

[Means for solving problems]

The composite material of the present invention includes a graphite plate, a copper plate made of pure copper or a copper alloy, and Mo, Nb, Ta, W provided between the graphite plate and the copper plate and having a smaller coefficient of thermal expansion than the copper plate.
Of the above-mentioned graphite plate and a copper plate through a high-temperature joining means such as diffusion bonding or hard brazing through the insert plate. They are joined together. The insert plate is preferably a metal having a higher elastic coefficient than the copper plate.

[Action]

In the composite material having the above configuration, the copper plate and the graphite plate are joined together through a heat-resistant insert plate, and the linear expansion coefficient of this insert plate is 7.5 × 10 ⁻⁶ (at 20 ° C.) or less. It was found that this is not too large as compared with the linear expansion coefficient of graphite of 4.0 to 6.0 × 10 ^−6, and that it is a very appropriate difference in thermal expansion from the viewpoint of preventing breakage of graphite. . Moreover, this insert plate has a large elastic coefficient and high rigidity. Since the copper plate and the graphite plate are bonded by diffusion bonding or the like through the heat-resistant high-rigidity insert plate having an appropriate coefficient of linear expansion as described above, the shrinkage of the copper plate after bonding is suppressed and the composite material Bending is also reduced. Therefore, the graphite plate can be prevented from cracking or breaking during the cooling process.

Since the graphite plate and the copper plate of the composite material are surface-joined to each other by a joining means that is performed at a high temperature such as hard brazing or diffusion joining, they have high joining strength and heat resistance. Further, it has far superior heat resistance as compared with joining by an adhesive material, and there is no fear that gas will be released in a vacuum atmosphere.

〔Example〕

In one embodiment shown in FIG. 1, the composite material 5 includes a graphite plate 6, a copper plate 7 made of pure copper or a copper alloy, and an insert plate 8 provided between the graphite plate 6 and the copper plate 7. It has and.

The insert plate 8 is made of a metal whose coefficient of thermal expansion is smaller than that of the copper plate 7 and whose melting point is equal to or higher than that of the copper plate 7. The target metals are Mo, Nb, Ta, W and alloys of these metals. The linear expansion coefficient of the insert plate 8 may be a value close to the linear expansion coefficient of the graphite plate 6 or an intermediate value between the graphite plate 6 and the copper plate 7. Specifically, a metal having a linear expansion coefficient of 7.5 × 10 ⁻⁶ (at 20 ° C.) or less is adopted.

The thickness of the copper plate 7 is practically about 2 to 30 mm, while the thickness of the insert plate 8 is practically 1/20 of the thickness of the copper plate 7 although it depends on its elastic coefficient. Through 1
/ 5th place, that is, about 0.1 to 2.0 mm is used. Since it is desirable that the insert plate 8 has high rigidity, it is preferable to select a material having an elastic coefficient higher than that of the copper plate 7. In consideration of the above, the material of the insert plate 8 is preferably a refractory / low thermal expansion metal such as Mo, W, Nb, or Ta, or an alloy thereof.

The insert plate 8 is sandwiched between the graphite plate 6 and the copper plate 7,
By heating to the bonding temperature and pressing in the thickness direction, the graphite plate 6 and the copper plate 7 are diffusion bonded via the insert plate 8. The graphite plate 6 and the insert plate 8
, Or by interposing an appropriate hard brazing material between the copper plate 7 and the insert plate 8 to join by hard brazing. Joining temperature is, for example, 600 to 100
It is around 0 ° C.

Although the shrinkage rate of the copper plate 7 is larger than that of the graphite plate 6 in the cooling process after joining, an insert plate 8 having high rigidity is sandwiched between the graphite plate 6 and the copper plate 7, and these are diffusion-bonded to each other. Or, since they are firmly joined by hard brazing, the contraction of the copper plate 7 due to the difference in the coefficient of thermal expansion is suppressed. Therefore, the bending of the composite material 5 is reduced, and the graphite plate 6 is prevented from cracking.

The melting point of the insert plate 8 is equal to or higher than the melting point of the copper plate 7, and the graphite plate 6 and the copper plate 7 are joined to each other by a joining means performed at a high temperature, so that the composite material 5 has excellent heat resistance. Exert its abilities. Moreover, since the thickness of the insert plate 8 is as thin as 1/20 to 1/2 of the thickness of the copper plate 7, it has little influence on the thermal conductivity between the graphite plate 6 and the copper plate 7. Further, not only a local load is not applied as in the case of mechanical fastening, but also a pollutant is not emitted as in the case of using an adhesive. In addition, since the heat resistance of graphite is excellent at about 2500 ° C in a non-oxidizing atmosphere,
By cooling the copper plate 7 side by an appropriate means, excellent high temperature heat resistance is exhibited.

For these reasons, the composite material 5 is suitable for an X-ray target, a sputtering target and the like.

FIG. 2 shows an example of the X-ray target 10. In order to obtain a characteristic X-ray of long wavelength carbon, the target 10 is
The composite material 5 shown in FIG. 3 is used. This composite 5
The end face 6a of the graphite plate 6 is processed into a taper shape, and a characteristic X-ray of carbon is generated by applying an electron beam to the taper end face 6a. In order to cope with the temperature rise at that time, a cooling cylinder 11 is provided on the copper plate 7 side, and a coolant such as cooling water is circulated through the cooling cylinder 11 through pipes 12 and 13 to cool the graphite plate 6 through the copper plate 7. Do.

In such an X-ray target, it is necessary to have a heat resistance of about several hundreds of degrees Celsius and not emit an impurity gas even in a vacuum atmosphere. Further, since the target 10 is rotated at a high speed around the axis for the purpose of preventing local heating, high bonding strength Required. The composite material 5 of this embodiment is suitable for satisfying these requirements. In the composite material 5 of the embodiment shown in FIG. 4, the copper plate 7 is provided with a tapered recess 7a.

The sputtering apparatus shown in FIG. 5 coats an adherend (not shown) with graphite and uses the composite material 5 of the present invention as a target. The structure of the composite material 5 is basically a structure in which a graphite plate 6 and a copper plate 7 are joined at high temperature via an insert plate 8 similarly to the composite material 5 (shown in FIG. 1) described above. The opposite side of the target is cooled, typically because the surface of the target is heated to high temperatures during sputtering. In the illustrated example, the coolant 15 is supplied to the copper plate 7 side through the coolant supply pipe 14,
The target, that is, the composite material 5, is cooled. In this case, the copper plate 7 also serves as a backing metal for pressing. In the figure, 16 is a magnet.

In order to increase the sputtering speed, it is necessary to increase the energy input to the target, but the heat resistance is 200 ° C or less in the conventional bonding with resin adhesive or soft brazing, There is a problem in heat resistance. On the other hand, the target using the composite material 5 according to the present invention is remarkably excellent in heat resistance, so that a larger amount of energy can be input, and the sputtering speed can be improved.

The joint shape of the composite material 5 or the graphite plate 6 used for the target includes an annular shape shown in FIG. 6, a rectangular shape shown in FIG. 7, or a U-shape shown in FIG.
Various shapes are possible.

〔The invention's effect〕

According to the present invention, it is possible to prevent breakage of graphite when a graphite plate and a copper plate having large thermal expansion coefficients are joined to each other by a high temperature joining means such as diffusion joining or hard brazing. Moreover, the composite material of the present invention is excellent in heat resistance and bonding strength, and there is no fear of releasing an impurity gas into the atmosphere.

[Brief description of drawings]

FIG. 1 is a sectional view of a composite material showing an embodiment of the present invention, and FIG.
FIG. 4 is a perspective view of an X-ray target using a composite material showing another embodiment of the present invention, FIG. 3 is a sectional view of the composite material shown in FIG. 2, and FIG. FIG. 5 is a cross-sectional view of a composite material showing an embodiment, FIG. 5 is a cross-sectional view of a sputtering apparatus, and FIGS. 6 to 8 are plan views showing mutually different shape examples of the composite material. FIG. 9 is a side view showing an example of a conventional composite material, and FIG. 10 is a plan view showing a state in which the composite material shown in FIG. 9 is cracked. 5 ... Composite material, 6 ... Graphite plate, 7 ... Copper plate, 8 ... Insert plate.

Claims (2)

[Claims] 1. A graphite plate, a copper plate made of pure copper or a copper alloy, and Mo, Nb, Ta or W provided between the graphite plate and the copper plate and having a smaller coefficient of thermal expansion than the copper plate. The above-mentioned graphite plate and copper plate are joined to each other through the insert plate by a joining means that is performed at a high temperature such as diffusion joining or hard brazing. A composite material consisting of graphite and copper or a copper alloy. 2. The composite material of graphite and copper or copper alloy according to claim 1, wherein the insert plate is made of a metal having a higher elastic modulus than that of the copper plate.