WO2006010179A1

WO2006010179A1 - Non-evaporable getter

Info

Publication number: WO2006010179A1
Application number: PCT/AT2005/000270
Authority: WO
Inventors: Harald Londer
Original assignee: Alvatec Alkali Vacuum Technologies Gmbh
Priority date: 2004-07-30
Filing date: 2005-07-13
Publication date: 2006-02-02
Also published as: AT501616B1; AT501616A4

Abstract

The invention relates to a container for an NEG, for introducing getter layers into a closed system. Said container comprises a housing (1) which is provided with at least one opening (2, 3) closed in a vacuum-tight manner and optionally integrated elements, and contains the getter layers to be introduced. Said container is characterised in that the getter layers to be introduced are applied to the inner wall of the housing and/or optionally to the integrated elements, and the at least one closed opening is closed by means of a temperature-dependent metal seal and can be opened by heating or mechanically.

Description

Non-evaporative getter

The present invention relates to a non-evaporating getter (hereinafter NEG) in the form of pre-evaporated getter layers in the interior of a container for introducing the same into a closed system, and to a method for its production. The NEG container is a housing with at least one vacuum-tight opening and optionally includes internals for surface enlargement. Furthermore, the container is provided with a gas or vacuum-tight closure. This closure can be opened mechanically or consist of a temperature-dependent metal seal. After opening the closure in a vacuum or inert system, the pre-evaporated getter layer inside the container is accessible and the NEG can develop its sorption capacity at room temperature.

The introduction of highly pure reactive or stable materials, such as. B. non-evaporative getter in bulk form, is nowadays without saturation by contact with the ambient atmosphere or a load on the atmosphere of the closed system by loose particles today usually can not cope. Numerous applications therefore require complicated transfer systems, complex processes or special pre-processing of the substances to be introduced. On the one hand, the materials to be introduced often have to be elaborately protected against contamination by contamination or mixing with the ambient atmosphere and, on the other hand, the release of the material in the highest purity in the vacuum range or in an inert atmosphere at a certain time must be ensured by a corresponding opening mechanism. The direct vapor deposition of active getter layers in the getter - application environment, as is common today with the display tubes, is not feasible in many applications due to the required high temperatures and the sometimes difficult to control Aufdampfvorganges or excluded for these or other reasons.

These requirements are usually solved by weaker material combinations with lower sorption capacity, complex and costly sorption pumps or transfer chambers, which, in addition to a not inconsiderable cost factor, also requires several time-consuming assembly or process steps:

Non-evaporating getters (NEGs) use different starting materials today. Alkali / alkaline earth metals are powerful sources of gettering, but are difficult to handle due to their high reactivity. (Scientific Foundations of Vacuum Technique, John Willey & Sons, New York (1962), p. 622; Della P. ₅ Vacuum, 1996; 47: 771). Therefore, in the NEG environment mainly Zr, V and Fe mixtures are used which, in addition to a low sorption capacity, have only a low sticking rate (retention time) of the absorbed residual gases (see, for example, P. della Porta, Technical Paper TP 202, 1992; US 6,506,319, US 6,672,819, US 6,420,002, US 6,514,430, US 6,322,720, US 6,200,494, B. Ferrario, Vacuum 47 (1996), p 363, US 6,322,720).

Mention should also be made of developments in which comminuted, very active barium alloys as NEG materials are introduced into vacuum chambers in solid, lumpy form which need not be activated. Their sorption performance of residual gases is described as very high, but their introduction into the field of application is complicated and the problem of loose particles is not solved.

US Pat. No. 5,312,607 (1994) US Pat. No. 5,312,606 (1994)

The invention thus has the object to overcome the above-mentioned problems and difficulties of the prior art and to provide an NEG (container with pre-vaporized getter layers and opening mechanism) of the type mentioned, with the help of highly active pre-evaporated getter, in sealed systems and Applications, vacuum chambers, pressure chambers, etc., can be easily introduced in predetermined amounts at an arbitrary time and made accessible at an arbitrary time, without jeopardizing the purity of the system. In addition, this container should be relatively inexpensive and can be produced without time-consuming and labor-intensive production steps.

This object is achieved in the aforementioned NEG according to the invention, which is that the getter is layered on the inner wall of the container and / or optionally on the internals and that at least one sealed opening is closed either with a temperature-dependent seal made of metal and opened by heating can be opened or mechanically opened.

Upon heating the NEG according to the invention to a certain temperature, which results depending on the material of the seal, the metal of the seal is melted and the transferred substance is released to the environment, ie in the closed system. The NEG according to the invention can thus be used in the entire field of vacuum technology, in which different getter effects are required to improve the vacuum.

Depending on the desired release temperature, different metals or alloys can be used for the seal. Preferably, the temperature dependent seal is selected from metals of the group consisting of Ga, In, Sn, Pb and their alloys.

According to a preferred embodiment of the invention, the temperature-dependent seal has a melting point in the range of 50 ⁰ C to 350 ° C.

Advantageously, the temperature-dependent seal in the non-pressed state has an average thickness in the range of 2-5 mm.

A further preferred embodiment is characterized in that the container after the temperature-dependent seal comprises a further section which is provided with gas-permeable, but solids-impermeable openings, preferably slots. Suitably, the openings are closed with a fine-meshed network or a gas-permeable membrane.

Preferably, the interior and its possible deposits with one or more getter materials coated by vapor deposition. The pre-evaporated getter layers preferably consist of the metals barium, lithium, calcium, cesium or combinations thereof. The metal layer or mass to be evaporated can be varied depending on the application.

It is furthermore particularly advantageous if the NEG container is of cylindrical or cuboidal design. However, other forms are conceivable.

The material of the NEG container is chosen according to the application. In the field of vacuum and overpressure applications, stainless steel, ceramic or glass containers are particularly suitable due to the low outgassing and high tightness. The shape of the NEG container is not subject to any restriction as long as appropriate pressing tools guarantee the exact pressing and thus the tightness of the container.

The tightness and the load capacity of the temperature-dependent seal depends on the starting material, the material density in the raw state and the compression during the pressing process and the surface to be sealed or the respective inner diameter of the Freisetzungsauslasses. Preferred sealing materials are Ga, In, Sn, Pb or their alloys, such as. B. InSn.

For the test series with a steel tube with an internal diameter of 7.2 mm and a wall thickness of 0.5 mm, between 35 mg and 45 mg in pure or a homogeneous InSn alloy were used. For larger sealing surfaces, even with stable spacers (rings, discs or rectangles made of steel, ceramic, glass) additional stabilization of the seal can be achieved.

The other opening of the container is closed after filling with the substance to be transferred so as to ensure that it can not open when the container is heated. Different materials can be used. Depending on the application, different techniques can be used. In the examples, the end was e.g. mechanically pressed to 1.5 mm by means of a screw press and then welded off electrically vacuum-tight.

Principle and function of the invention:

1.) Depending on the desired release temperature, a seal of appropriate

Pure metals, such as Ga, In, Sn, Pb, or produced from their alloys.

2.) With a pressing device, the NEG container, which has two openings - e.g. is open at both ends in a cylindrical housing -, mechanically sealed at an opening or an end with the preformed, temperature-dependent seal.

3.) Then the desired getter evaporator source and components for surface enlargement is introduced. This can be done, if necessary, in a protective gas atmosphere or in a vacuum (glove box or the like).

Then, the getter in the container evaporator source is evaporated under vacuum by external heat, thereby coating the inside of the NEG container and the components (sheets / nets) were introduced to increase the surface area.

4.) Thereafter, the container is either evacuated or tightly sealed with the atmosphere in the container while preventing contamination of the contents, mechanically (tight interference fit) or chemically sealed in the form of an adhesive. 5.) By directly or indirectly heating the NEG to the selectable release temperature, the seal melts and the getter layers become accessible. The opening of the seal for the development of the S orptions effect can also be assisted by a preloaded spring mechanism or an inner container.

6.) In many getter applications, it is desirable and meaningful that the getter material remains in the getter housing after melting the seal and is connected by a gas-permeable, but loose particle-containing opening with the atmosphere in the application. The opening (s) is (are) located in a region of the getter housing that was not previously protected by the seal.

The invention thus has the following advantages:

The introduction of highly active NEGs in vacuum, normal and overpressure environments;

• the release of the getter layers by thermal opening of the seal at a precise, freely selectable time;

• a control of the release time by heating the container, the chamber, the component or the application;

• Precise control of the thermal release mechanism with selectable temperatures in the range of 50 ° C to 350 ° C;

A process sequence without special opening of the vacuum chamber, the pressure chamber, the application or the component;

A preferred embodiment of the invention is explained below with reference to examples and the drawings.

1 a), a cylindrical preformed temperature-dependent gasket 4 made of metal, for example of Ga, In, Sn, Pb or alloys thereof, is arranged on an opening 2 of a cylindrical housing 1. Thereafter, the seal 4 by a pressing device 8, which simultaneously exerts pressure on the two opposite base surfaces of the sealing cylinder, pressed (Fig. 1 b)). By compression and lateral expansion of the seal 4, a vacuum-tight closure of the opening 2 of the housing 1 is achieved. The one-sided sealed container with the pressed seal 4 is shown in Fig. 1 c). 2 shows the infestation of the NEG housing 1, which has the seal 4, with getter material 3, that is, for example, Ba, Li, etc. The reference numeral 5 schematically denotes internals in the housing, that is, for example, a folded, non-rusting thin sheet metal with holes which are about 2 mm in diameter.

FIG. 3 illustrates the vaporization of the getter material 3 by externally heating the housing 1 in the region in which the getter material 3 is located. That portion of the housing 1 having the pressed gasket 4 is desirably cooled.

FIG. 4 shows the getter material 6 vapor-deposited in layer form on the internals. After complete vapor deposition, the end 7 of the container is squeezed and electrically welded in order to close it. This NEG container can be placed in the room in which the getter material is to be used.

In this space, the gasket 4 is heated (Fig. 5). When the melting temperature is reached, the metal melts, whereby the housing opens (FIG. 6). FIG. 7 shows the state in which the getter material is active and can take up substances from the space in which the container is located. This is indicated in Fig. 7 with a double arrow.

Example 1 :

To produce the NEG according to the invention, a tubular Gettergehäuse stainless steel was used with a length of 100 mm, a wall thickness of 0.5 mm and an inner diameter of 7.2 mm.

The sealant used was a fit of pure indium (50 mg).

The indium fitting was positioned at the desired location (10 mm from a pipe end) and then evenly compacted from both sides by simultaneous pressing with tools. Due to the resulting material expansion of the indium at the sealing edge, there was a tight connection with the container inner wall and thus to a vacuum-tight seal.

The sealed tube was filled in a glove box with a getter evaporator source and the surface enlarging components. The open end of the tube was sealed by means of a hose clamp, removed from the glove box and attached to a vacuum pump evacuated in the range of 10-5 mbar. Subsequently, the getter material was evaporated by heat from the outside and has deposited on the inside of the container and the oberflächenvergrößernden material. Then, the hose clamp was closed again to secure the vacuum, and the pipe end was pressed with a screw press 3 cm after the hose clamp and then electrically welded.

Subsequently, the thus sealed NEG was fixed to the inner wall of a vacuum chamber. After establishing the initial vacuum, the NEG container was externally heated to 168 ° C over a period of 2 minutes by means of an industrial furnace via the heat transfer of the vacuum chamber wall.

The pressed indium seal then melted, i. the getter layers became accessible and the NEG could now fulfill its task, the sorption of residual gases, successfully.

Example 2:

Same construction as in Example 1. As a sealing material, however, an alloy of

InSn used, whose mass was 80 mg.

After establishing the initial vacuum, the NEG was externally heated to 137 ° C via heat transfer of the vacuum chamber wall over a period of 2 minutes by means of an industrial furnace. The pressed InSn seal then melted, which opened the container and made the getter layers accessible.

Claims

claims:

1. NEG container for introducing getter material into a closed system, which container comprises a housing (1) with at least one vacuum-tightly sealed opening (2, 3) and possibly internals and contains the getter material (5) to be introduced,

characterized,

in that the getter material to be introduced is layered on the inner wall of the housing and / or optionally on the internals and that the at least one sealed opening is either closed with a temperature-dependent metal seal and can be opened by heating or can be opened mechanically.

2. NEG container according to claim 1, characterized in that the temperature-dependent seal (4) is selected from metals of the group consisting of Ga, In ₅ Sn, Pb and their alloys.

3. NEG container according to claim 1 or 2, characterized in that the temperature-dependent seal (4) has a melting point in the range of 50 ° C to 350 ° C.

4. NEG container according to one of claims 1 to 3, characterized in that the temperature-dependent seal (4) in the non-pressed state has an average thickness in the range of 2-5 mm.

5. NEG container according to one of claims 1 to 4, characterized in that the housing (1) following the temperature-dependent seal (4) comprises a further section (6) which with gas-permeable, but solids-impermeable openings (7), preferably Slits, is provided.

6. NEG container according to claim 5, characterized in that the openings (7) are closed by a fine mesh or a gas-permeable membrane.

7. NEG container according to one of claims 1 to 6, characterized in that the substance to be introduced (5) is a getter material and is preferably vapor-deposited in the inner part of the container and the surface-enlarging components.

8. NEG container according to one of claims 1 to 7, characterized in that the vapor-deposited getter preferably consists of the metals of the group of group IA ₅ IIA ₅ IIIB or combinations thereof.

9. NEG container according to one of claims 1 to 8, characterized in that the vapor deposited getter preferably consists of the metals Ba, Li ₅ Ca, Cs or combinations thereof.

10. Container according to one of claims 1 to 9, characterized in that the housing (1) is cylindrical or cuboidal.