JP2004327349A - Evaporation type getter and vacuum container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a getter, having a small and simple structure and easy to manufacture, and to provide a vacuum container suitable for the getter. <P>SOLUTION: The evaporation type getter comprises tubing 2 using fibers made of a conductive metal wire (for example, a metal containing Ti as a main component), and a material having appropriate thermal resistance and electric insulation so that the material is not melted at the evaporation operation temperature of the metal. A structure with the metal wire inserted is provided in an inner space of the tubing. Electrical current is applied to the metal wire to allow the material to evaporate, and to attach at least to the tubing. Because the metal wire which can be high temperature is wrapped by the insulating tubing, the metal wire can be evaporated with maintaining the heat of the heated metal wire. Accordingly, the insulating structure can be simple, easy to manufacture, small, and low cost. Because the tubing uses fibers, the surface area is wider allowing a wider deposition area to be obtained for an improved discharge speed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a getter used for mounting a sensor or the like used in a vacuum environment, and particularly to a getter suitable for small-sized and inexpensive mounting and a vacuum container suitable for the getter.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2003-004524 [Non-Patent Document 1] Vacuum Handbook (published by Nippon Vacuum Technology Co., Ltd.)
In the past, vacuum tubes and cathode ray tubes, and in recent years, sensors (vibrating gyros, far-infrared sensors, resonance filters) manufactured using micromachine technology, etc., use a vacuum vessel as an operating principle or to improve its performance. It is required to be implemented within. In vacuum vessels, no matter how much the gas inside the vessel is exhausted and removed, the adsorbed gas on the inner wall remains and is released later, or gas leaks at the sealing part of the components or small permeated gas in the material body exist. Doing is well known. Then, as the time elapses after the vacuum sealing, the degree of vacuum in the vacuum container is reduced by the gas, and the performance of the electron tube and the sensor is reduced. For this reason, a technique has been applied in which a solid vacuum pump called a “getter” is sealed in the vacuum container of these electronic components and the above-mentioned gas is removed to maintain the degree of vacuum in the vacuum container.
There are evaporable getters and non-evaporable getters widely used as getters, and some of these getters are provided with or without an electric heater for heating them. In particular, for sensors that have been actively researched and developed in recent years, miniaturization is required, and many devices, such as conventional electron tubes, do not allow the entire member to be heated to high temperatures during manufacturing. The method is limited in getter insertion.
As a practical method for enclosing getters in small packages,
(1) The non-evaporable getter is heated and activated, and then sealed.
{Circle around (2)} A non-evaporable getter with a built-in heater is enclosed, sealed and heated to activate.
{Circle around (3)} The evaporable getter is sealed and heated by a separate heater to evaporate.
(4) A method of evaporating the evaporable getter itself as an electric heater has been considered.
[0003]
[Problems to be solved by the invention]
However, each of the above methods has the following problems, and is insufficient as a small and inexpensive getter.
(1) requires equipment for enclosing, assembling, and sealing by heating in a vacuum device, which makes the manufacturing equipment complicated and large, but is highly productive and suitable for mass production. Increases the cost (see Patent Document 1).
In the case of (2), since the getter itself is difficult to manufacture and very expensive, it is difficult to reduce the cost as a vacuum vessel.
The problem (3) is that not only is the evaporable getter expensive, but also because it has a large heat capacity, it cannot be put into a small part.
(4) has the same principle as that of a vacuum evacuation pump called a titanium getter pump or a titanium supplementation pump (refer to page 90 of Non-patent Document 1), in which gas molecules are deposited on a clean surface of a metal deposited in vacuum. Are adsorbed and captured, and the result is evacuated.
In order to insert a getter into a small vacuum vessel at low cost, it is considered that the method (4) that can reduce the cost of the getter material itself is most suitable. However, in the vacuum vessel in this case, for example, a titanium alloy wire is used as an evaporation source, and the titanium alloy wire is directly energized to heat and evaporate titanium, and the wall surface around the evaporation source on which the evaporated titanium is attached, and the evaporated metal is diffused. It is required to provide a shielding plate for eliminating the influence of other components on the structure, and to further provide electrical insulation between the evaporation source and the surroundings. Therefore, when the size is reduced, the evaporation source becomes a thin line, and there is a problem that it is difficult to use a structure in which the same evaporation source as a conventional pump is used independently.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a getter which has a simple structure, is small in size and easy to manufacture, and a vacuum container suitable for the getter.
[0004]
[Means for Solving the Problems]
In the present invention, a tube made of a conductive metal wire (for example, a metal mainly composed of Ti) and a fiber made of a material having heat resistance and electrical insulation that does not melt at the evaporating operation temperature of the metal. Having a structure in which the metal wire passes through the inner space of the tube, and is configured to apply an electric current to the metal wire to evaporate the material, and adhere to at least the tube for use. .
[0005]
【The invention's effect】
In the present invention, since the metal wire to be heated is wrapped by the insulating tube, the metal wire can be evaporated while keeping the metal wire warm during heating. Therefore, the insulating structure is simple, the manufacturing is easy, and the device is small and inexpensive. Further, since the tube uses fibers, the surface area is large and the vapor deposition area can be large, so that effects such as an improvement in the pumping speed can be obtained.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. The following figures show an example of the form, and the dimensional ratio and the like are not limited.
FIG. 1 is a diagram of a first embodiment, and is a perspective view showing a structure in which a metal wire 1 serving as a getter material of the present invention is covered with a woven tube 2 made of a heat-resistant insulating material. In FIG. 1, one of the ends of the getter 3 is drawn.
[0007]
In FIG. 1, a metal wire 1 is a single material or an alloy of a material having a high performance of adsorbing gas, such as titanium, zirconium, vanadium, iron, aluminum, and metal barium, or a structural material such as molybdenum, tantalum, and nickel. And an alloy with the material to be used.
The metal wire serving as a getter is known as a material for a titanium sublimation pump described in Non-Patent Document 1 or as a non-evaporable getter material as described in a catalog of Saes Corporation.
[0008]
In this embodiment, for example, an alloy of titanium and molybdenum was used as the metal wire 1 having a thickness of 200 μm.
The operation and action of the alloy used as the metal wire 1 has been known for a long time, but will be briefly described below.
When a current is applied to the metal wire 1 in a vacuum to generate heat by its electric resistance, titanium starts to evaporate from about 1000 ° C. Titanium evaporated in a vacuum binds to air molecules remaining in the vacuum vessel and adheres to the surroundings, or forms an active titanium film on the surrounding wall without bonding, and then captures flying air molecules I do. Note that the current application to the metal wire is often performed in a pulsed manner.
[0009]
In the present embodiment, the tube 2 is covered around the metal wire 1. That is, it has a structure in which the metal wire 1 passes through the internal space of the tube 2.
This structure is similar in structure to the coating called "glass sheath" used for connection of the heater wire, but the glass sheath has a heat-resistant temperature of only about 500 ° C, and melts at the getter evaporation temperature in the present invention, Not a coating material. Therefore, in this example, a material obtained by knitting alumina ceramic fibers into a tube having a diameter of 1 mm was used.
[0010]
Examples of the alumina ceramic fiber include “Almax” (trade name of Mitsubishi Mining Materials Co., Ltd.) and “Muff Tech Fiber” (trade name) of Mitsubishi Chemical Corporation. When the getter material is titanium, a heat-resistant temperature up to about 1400 ° C. is practically sufficient, and the above-mentioned substances have sufficient durability.
It should be noted that any material other than alumina fiber can be used as long as it has electrical insulation at high temperatures and does not dissolve.
[0011]
The getter 3 composed of the metal wire 1 and the tube 2 generates heat by applying a current. Therefore, it is necessary to electrically connect the metal wire 1 at the connection portion (the end of the getter) between the metal wire 1 and the current supply terminal. When the metal wire 1 is exposed, when the metal wire 1 is heated, the vaporized material is released to the outside of the tube 2 and adheres to the insulating material to insulate the current supply terminal from the peripheral portion. May decrease.
2A and 2B are views showing a structure for addressing the above-described problem, FIG. 2A is a perspective view, and FIG. 2B is a cross-sectional view.
[0012]
As shown in FIG. 2, the end 41 of the tube 2 is caulked using a metal fitting 4 like a crimp terminal, and the metal wire 1 is also caulked at another location 42 to be electrically connected to the metal fitting 4. And it connects to a current supply terminal using the said metal fittings 4. In addition, as a material of the metal fitting 4, for example, a 4-2 alloy can be used. That is, the tube 2 located in a region of the metal wire 1 which is not desired to be evaporated is brought into close contact with the metal wire 1. With such a configuration, it is possible to prevent a decrease in insulation due to the getter material evaporating near the current supply terminal and attaching near the current supply terminal.
[0013]
Next, a method of using the getter will be described by taking as an example a case where the getter is mounted on a disk-shaped vacuum container.
FIG. 3 is a perspective view showing a state where the cap of the vacuum container is removed, that is, a portion of the stem 6 to which the sensor chip 5 and the getter 3 are attached. The upper part is covered with a cap 63 indicated by a broken line, and the inside is evacuated to form a vacuum container.
This vacuum container is formed by using a material having low gas permeability such as Kovar, stainless steel, 4-2 alloy, aluminum for vacuum, etc., in order to keep the inside vacuum, and by forming the stem 6 and the cap 63 in an airtight manner. I have.
A sensor chip 5 formed by using, for example, a silicon semiconductor process is die-bonded to the center of the stem 6 on which the hermetic terminal 61 is disposed, and is electrically connected to the hermetic terminal 61 around the sensor chip 5 by wire bonding 7. Connection was made.
[0014]
In this embodiment, the getter 3 is arranged around a hermetic terminal 61 used for electrical connection of the sensor chip. It was connected to a hermetic current supply terminal 62 installed around it by ultrasonic welding. The hermetic terminal 61 and the current supply terminal 62 are naturally electrically insulated from the stem 6.
[0015]
Thereafter, a cap 63 (in FIG. 3, the outer shape of the cap is shown by a broken line and the outer wall surface is drawn in a transparent manner to illustrate a getter in FIG. 3) is hermetically welded around the stem 6 to complete the container.
At the time of welding in a vacuum or after the above-mentioned hermetic welding, a current is applied to the getter 3 via the current supply terminal 62 to evaporate the titanium and activate the getter.
At this time, in the case of a tube made of a woven fabric, by selecting the length of the tube 2, the getter 3 is curved in a circular shape as shown in FIG. 21). At this time, if the fiber density is set so that the closed portion 21 cannot be seen from the outside, when the titanium of the metal wire 1 evaporates, the inside of the sensor chip 5 where the sensor chip 5 is disposed will have titanium vapor. It adheres to the fibers of the tube 2 and does not move around. On the other hand, since the outer peripheral side of the tube becomes rough (22), the evaporated titanium vapor adheres to the fiber of the tube and also passes through the eye of the fiber of the tube and is also deposited on the inner peripheral wall of the vacuum vessel. Note that, in FIG. 4, only the fibers in one direction are drawn among the vertical and horizontal fibers constituting the tube 2 so that the above-described operation can be easily understood.
[0016]
Due to the above action, the evaporated titanium is mainly attached on the fiber. Since the fiber has a very large surface area with respect to its volume, the deposition area of titanium is very large. According to the adsorption principle of the evaporative getter, the larger the metal deposition area, the higher the efficiency of adsorption. Therefore, the getter can secure a pumping speed despite using a thin tube.
In addition, the vapor that jumps out of the outer periphery of the tube is not only a vapor deposition film on the outer peripheral wall and contributes to adsorption, but also the vapor deposition surface is advantageous in maintaining a vacuum degree because gas emission from the base material is suppressed.
Note that the metal fitting 4 shown in FIG. 2 is not always necessary, and the metal wire 1 may be directly joined to the current supply terminal as long as a countermeasure against metal vapor can be taken.
[0017]
As described above, since the getter according to the present invention is basically composed of a metal wire serving as a getter and a tube made of heat-resistant insulating fiber, a fine powder of a getter material alloy is prepared like a non-evaporable getter. There is no need for it, so it can be manufactured with inexpensive materials and easy methods, so the cost is basically low. In addition, the vacuum vessel required for installation is complicated, and the process for insulation, which tends to be complicated, is not required, so the cost of getters is reduced. In addition, the cost of the vacuum container can be reduced at the same time.
[0018]
Next, FIG. 5 is a perspective view showing a second embodiment of the present invention. In this embodiment, the getter 3 described in the first embodiment is mechanically supported, and a three-dimensional vacuum mounting of a sensor chip or the like is performed.
Since the getter 3 according to the present invention is used in a small vacuum vessel, it is desired to minimize the heat capacity in order to use the getter 3 so as not to affect the surroundings during activation. Therefore, the metal wire 1 is inevitably very thin as in the first embodiment. Therefore, the mechanical strength tends to be insufficient, so that when the getter 3 is installed above the sensor chip or the like, it is necessary to mechanically support the getter 3. For example, this embodiment is applied to a case where the getter 3 is installed away from a portion where the getter 3 is not to be touched, such as a case where the getter 3 is to be installed away from the surface of the stem 6.
[0019]
FIG. 5 shows the stem with the getter 3 attached before the cap is welded. The support 8 is made of, for example, metal, and has a shape in which a plurality of branch-like support members extend from an annular portion along the inner periphery of the stem 6 toward the inside of the circle. A getter 3 is disposed on the plurality of branch-like support members by bending the getter 3 into a circular shape.
The getter 3 must have a dense mesh so that the metal vapor does not scatter to the outside of the tube 2, but since it is a woven fabric, there is no confidentiality and vacuum evacuation is performed without any problem.
Also, since it is in a vacuum, the heat from the metal wire 1 which becomes high temperature by energization is only radiant heat. However, since this is cut off by the tube 2 made of a heat-resistant insulating material, the sensor chip 5 in another container or the like can be used. There is no harm to the parts.
Further, in this case, since the metal wire 1 is electrically insulated by the tube 2, the metal wire 1 can be mechanically supported together with the insulation simply by being placed on the support 8, so that the mechanical reliability such as the earthquake resistance of the vacuum vessel can be improved. Easy to achieve. Therefore, an inexpensive vacuum vessel having a simple structure can be realized.
[0020]
In Examples 1 and 2, the tube 2 is provided with a portion having a fiber density such that the metal wire 1 inside cannot be seen through from the outside. In other words, when the getter is bent and placed in a circular shape, the inner fibers become dense and the eyes become clogged, that is, it becomes impossible to see through. When the evaporated metal is released from the metal wire, the vapor moves linearly. In a vacuum container, a built-in component such as a sensor chip is generally arranged on the center side of the container, and the peripheral portion is only a wall surface. Therefore, if the getter 3 is installed in a circular shape along the outer periphery of the container, the fiber density of the circular tube 2 automatically increases on the inner peripheral side, the metal vapor is captured by the tube 2, and the fiber density decreases on the outer peripheral side. The metal vapor is released from the weave, and the inner wall of the vacuum vessel is coated with Ti to serve as a deposition surface, and gas release from the wall surface can be suppressed. In other words, the vapor density is increased in the direction of hitting a site where there is a problem with metal vapor deposition, so that the vapor is entirely adhered to the tube 2, and the region where there is no problem is also adhered to the inner wall of the surrounding vacuum vessel.
[0021]
Next, FIG. 6 is a perspective view showing a third embodiment of the present invention. In order to explain the internal structure, about a quarter of the front part of the cap 63 is cut out and shown, and the cap 63 is displayed in a transparent state.
In the present embodiment, the getter 3 is installed in a shielded space, and emphasis is placed on preventing the metal vapor from coming around. In FIG. 6, the shielding plate 9 has an annular shape along the circumference of the stem 6 so as to separate a central portion (a mounting portion of the sensor chip 5) in the stem 6 from an outer peripheral portion. A step is provided in the middle of the ring in the vertical direction. This step has a function similar to that of the support 8 in FIG.
The shielding plate 9 shields the central portion from the metal vapor scattered from the getter 3, and does not have an airtight structure.
[0022]
Also in this embodiment, since the getter 3 wraps the metal wire 1 with the insulating tube 2, an insulating structure is not required, and the getter 3 may be directly placed on the step.
Further, in the case of this embodiment, the shielding plate 9 is provided to shield the central portion from the metal vapor scattered from the getter 3, so that the fiber of the tube 2 is cut off as in the embodiment of FIG. There is no need to control the fineness of the eyes, and a highly reliable vacuum vessel can be realized at low cost.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a getter according to a first embodiment of the present invention.
FIGS. 2A and 2B are views showing a connection portion of a getter according to the first embodiment of the present invention, wherein FIG. 2A is a perspective view of a getter end, and FIG.
FIG. 3 is a perspective view showing a stem of a vacuum vessel provided with a getter according to the first embodiment of the present invention.
FIG. 4 is a perspective view for explaining a change in a fiber eye of a getter tube according to the first embodiment of the present invention.
FIG. 5 is a perspective view showing a vacuum vessel according to a second embodiment of the present invention.
FIG. 6 is a perspective view showing a vacuum vessel according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal wire 2 ... Tube 21 ... The part where the fiber of the tube was clogged 22 ... The part where the fiber of the tube was coarse 3 ... Evaporation type getter 4 ... The metal fitting 41 ... The crimping part 42 of the tube 2 on the metal fitting 4. ... Caulked portion of metal wire 1 on metal fitting 5 Sensor chip 6 Stem 61 Hermetic terminal 62 Hermetic current supply terminal 63 Vacuum vessel cap 7 Wire bonding 8 Supporting tool 9 Shield plate

Claims (8)

A conductive metal wire, and a tube using a fiber made of a heat-resistant insulating material that does not melt at the evaporating operation temperature of the metal, comprising a structure in which the metal wire is passed through the inner space of the tube; An evaporable getter, wherein a current is applied to a wire to evaporate the material, and the material is attached to at least the tube. The evaporable getter according to claim 1, wherein the conductive metal wire is a metal wire containing Ti as a main component. The evaporable getter according to claim 1, wherein the tube located in a region of the metal wire that is not desired to be evaporated is brought into close contact with the metal wire. 4. The evaporable getter according to claim 3, wherein the tube is closely attached to the metal wire by caulking an end of the metal wire and the tube located at the portion with the metal fitting. The evaporable getter according to any one of claims 1 to 4, wherein the tube includes a portion having a fiber density such that a metal wire inside the tube cannot be seen from the outside. A vacuum-equipped container, and a current supply terminal hermetically sealed to the container and penetrating inside and outside of the container, and electrically insulated from the container. A vacuum container having a structure in which the evaporable getter according to any one of claims 1 to 5 is joined. 7. The vacuum according to claim 6, wherein a support portion for mechanically supporting the evaporable getter is provided in the container, and the evaporable getter is supported by the support portion and housed in the container. container. The vacuum container according to claim 6, wherein a shielded space is provided in the container, and the evaporable getter is stored in the space.

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