JPH0793099B2 - Method for manufacturing rotating anode X-ray tube target - Google Patents

Description

The present invention relates to a rotary anode target for an X-ray tube, in particular, a rotatable heat radiation member and an X-ray generator fixed to the heat radiation member and facing the cathode. The present invention also relates to a method for manufacturing a rotating anode target suitable for increasing the capacity.

[Conventional technology]

Conventionally, as a target of a rotary anode X-ray tube, a combination of a tungsten alloy, which is an X-ray emitting material, and molybdenum or graphite, which is a heat dissipation member, has been used. The proposal for use as a member is made in JP-A-61-143929, and the covering of the heat-dissipating member with tungsten is proposed in JP-A-58-169853 for which graphite is used as the heat-dissipating member. .

[Problems to be Solved by the Invention]

Since the targets of tungsten and tungsten-molybdenum have a large specific gravity, the load acting on the bearings of the rotor becomes large and it is difficult to make them function when the size of the target is increased to increase the heat capacity. Further, the tungsten-graphite target can be increased in size by increasing the heat capacity because the specific gravity of graphite is small, but the deterioration of the bonding interface strength due to the reaction layer of carbide or the like during use poses a problem.
Even if a barrier layer that suppresses the generation of carbides is provided, the mechanical strength of graphite itself is basically low and it is difficult to apply it to high-speed rotation.

In order to confirm the safety due to the material of this heat dissipation member, tungsten with a target shape of φ100 mm shown in Fig. 5,
Table 1 shows the results of comparing the stress (centrifugal force) of molybdenum, graphite, and aluminum nitride materials at high speed rotation (21.000 RPM) by the finite element method, and comparing the safety factors shown in Eq. (1).

Safety factor = maximum tensile strength of material / maximum stress by calculation ...
(1) From the table, it can be seen that aluminum nitride has about 12 times the allowable strength of tungsten, about 2 times the molybdenum, and about 4 times the allowable strength of graphite.

From these results, aluminum nitride ceramics are considered to be ideal as a heat dissipation member because they have the characteristics of low specific gravity, large specific heat, high thermal conductivity and high melting point. However, since aluminum nitride is a ceramic, its reliability of mechanical strength is unstable. Also, the joining of ceramics and metal is extremely difficult in itself, and an optimal method such as this has not been established yet. This is especially true for aluminum nitride ceramics, which is a new material.
Therefore, in order for aluminum nitride ceramics to actually function as a heat dissipation member for a rotating anode X-ray tube target, ordinary brazing and joining methods such as simple physical vapor deposition (PVD) are sufficient to improve reliability. Not applicable.

In view of the above, the present invention improves the reliability deterioration of the mechanical strength caused by using ceramics such as aluminum nitride as the constituent material of the heat dissipation member, increases the reliability of the mechanical strength of the target made of ceramics, and It is an object of the present invention to provide a method for manufacturing a rotating anode X-ray tube target that can enhance heat dissipation.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, a method for manufacturing a rotary anode X-ray tube target according to the present invention is a conductive film made of a metal of an X-ray emitting material or a compound thereof using CVD on the entire surface of a ceramic constituting a heat dissipation member. It is characterized by covering with.

[Action]

By covering the entire surface of ceramics such as aluminum nitride whose mechanical strength is unstable with CVD with a conductive film made of a metal of X-ray emitting material or its compound, the entire surface of ceramics such as aluminum nitride can be covered. Fine cracks can be filled with metal or its compound. From the above results, it is possible to increase the mechanical strength at high speed rotation and form a stable electric field when a high voltage is applied.

〔Example〕

FIG. 1 shows a manufacturing apparatus used in the manufacturing method of the present invention.
Is an aluminum nitride target member, 2 is a reaction tube, 3 is an electric furnace, and 4 is a target insertion rod. For the reaction tube 2,
The WF ₆ cylinder 5, the H ₂ cylinder 6 and the Ar cylinder 7 are connected in parallel via mass flow meters 5a, 6a, 7a and valves, respectively. Ar is for cooling, and 8 is a heater for heating WF ₆ . Also, in order to reduce the pressure inside the reaction tube 2, N ₂
Connect an oil rotary vacuum pump (not shown) through the trap 9,
The upstream of the exhaust system is connected to the absorption tower via the die floor 10. FIG. 2 shows an example of a target manufactured by the manufacturing method of the present invention. The target 11 is an aluminum nitride ceramics 1 and a tungsten 12
It is composed of.

Next, the procedure for forming the tungsten conductive film will be briefly described. The reaction tube 2 is depressurized by an oil rotary vacuum pump to flow H ₂ gas, and the temperature at which the tungsten conductive film is formed, for example,
The temperature is set to 500 ° C. and WF _{6 is} passed through the reaction tube 2. The gas at this time is, for example, WF ₆ = 20cc / min, H ₂ = 1000cc
/ min, (WF ₆ : H ₂ = 1: 50), total pressure 0.5 Torr ~ 760 Torr.

As a result, a hydrogen reduction reaction of WF ₆ + 3H ₂ → W + 6HF occurs, and a tungsten conductive film is formed on the surface of the target 11. After generating the desired thickness, W
It is cooled to room temperature by flowing the F ₆ and H ₂ gases instead of Ar gas, and then the inside of the reaction tube 2 is brought to atmospheric pressure with Ar gas to take out the target 1.

FIG. 3 shows a state photograph of the bonding interface of the tungsten-aluminum nitride target obtained by the above method. In this way, it can be seen that in this method, tungsten has spread very well around the surface of the aluminum nitride ceramics. This makes it possible to obtain a high-strength target made of aluminum nitride ceramics.

The above describes an example of a tungsten film having a uniform film thickness, but as shown in FIG. 4, it is not always necessary that the film thickness of the tungsten covering the entire surface of the target is uniform. It is also possible to reduce the thickness of the target as a whole by supplying the gas concentratedly only to the track layer to form a tungsten layer with a desired thickness, or to reduce the thickness of other parts by grinding or the like. It is also possible to improve the high temperature resistance by forming a tungsten alloy in the X-ray generation layer.

Further, the metal that covers the heat dissipation member is not limited to tungsten or a tungsten alloy, and any metal that is an X-ray emitting material or a compound thereof may be used, such as molybdenum or a molybdenum alloy.

Furthermore, the temperature, pressure, gas flow rate, etc. in the reaction tube shown in this example are an example of the case where tungsten is used as the metal, and if a conductive film of an X-ray emitting material is formed, other conditions are used. But it is possible.

〔The invention's effect〕

Aluminum nitride has low specific gravity and high thermal conductivity,
In addition, it has a large specific heat and a large specific strength, so it has ideal conditions for a rotary anode X-ray tube target due to its physical properties, but since aluminum nitride is a ceramic,
The reliability of the structure is difficult to say as it is. According to the manufacturing method of the present invention, it is possible to significantly improve the reliability of the rotating anode X-ray tube target with respect to the mechanical strength as a structure, and at the same time, to use aluminum nitride as an insulator. Conductivity can be imparted. At that time, by covering the entire surface of the aluminum nitride ceramics, which is an insulator, with a conductive film, a stable electric field can be obtained,
It is possible to prevent the occurrence of abnormal discharge locally. That is, without covering the entire surface of the aluminum nitride ceramics,
For example, when the bottom surface is not covered, when it is attached to an X-ray tube and used specifically, gas is released from the ceramic surface and the inside of the tube is boosted to generate glow discharge. However, the present invention solves such a problem. In addition, by covering the entire surface with tungsten, the heat dissipation by radiation can be enhanced as compared with the aluminum nitride main body.

As a result, it becomes possible to actually manufacture a rotary anode X-ray tube target having a high function, which cannot be obtained with the rotary anode X-ray tube target manufactured by the conventional manufacturing technique.

[Brief description of drawings]

FIG. 1 is a view showing a CVD apparatus used in the manufacturing method of the present invention, FIGS. 2 and 4 are sectional views of a rotary anode X-ray tube target manufactured by the manufacturing method of the present invention, and FIG. FIG. 5 is a mesh division diagram of a model used for confirming the safety of the material of the heat dissipation member, FIG. 5 is an enlarged photograph showing the metal structure of the joint between aluminum nitride and tungsten of the rotating anode X-ray tube target manufactured by the invention. .

Continuation of the front page (56) Reference JP-A-2-94344 (JP, A) JP-A-63-174251 (JP, A) JP-A-61-143929 (JP, A)

Claims (1)

[Claims] 1. A method of manufacturing a rotary anode X-ray tube target, characterized in that the entire surface of a ceramic constituting a heat dissipation member is covered with a conductive film made of a metal of an X-ray emitting material or a compound thereof by using CVD.