EP1173877B1 - Field emission device using a reducing gas and method for making same - Google Patents

Description

Technical area

The present invention relates to a generally a device using a source field effect electrons (for example micropoints) and more particularly a device to field emission for example a flat screen of visualization by cathodoluminescence excited by field emission, or cold emission, using microdots. It also concerns the manufacture such a device.

More precisely, the invention is relates to the constitution of a reducing atmosphere inside the device in order to fight oxidation of microtips (or other elements electron emitters) during the operation of this device.

State of the art

Microtip screens are tubes flat cathodes that operate under vacuum. These screens comprise a cathode (formed in particular of cathode conductors, grids and microtips) and an anode (formed of conductors and phosphors). To maintain the vacuum, we use a element known as getter, as is done for conventional cathode ray tubes. A getter is a element which, when activated under vacuum by heating, is likely to fix the gases desorbed by the device and maintain the necessary level of vacuum to the proper functioning of it.

FIG. 1 is a partial view, in section cross-section, a microtip screen 1 according to art prior. It includes two glass slides 2 and 3 placed next to each other. Blades 2 and 3 are sealed around their edges by means of a paste of 4 glass with low melting point. The blade 3 supports, on its internal part on the screen, the cathode which is consisting of microtips 5 formed preferably on a resistive layer, such as a silicon layer 6 deposited on cathode conductors 14, and of grid electrodes 7 separated from the layer resistive 6 by a layer 8 of dielectric material. The blade 2 supports, on its internal part on the screen, the anode which consists of one or more conductive layers 9 supporting one or more 10. Between the blades 2 and 3 is thus defined a space 11 isolated from the outside. This space 11 is kept under vacuum. The vacuum was obtained by means of a bumper 12 provided in the blade 3. The 12th is initially opened and connected to a vacuum pump. he also allows the introduction of one or more getters such as the getter 13. Once the emptiness is realized, the tube 12 is closed as shown in figure 1.

The life of these devices depends, among others, that of the cathodes which is related to the electron current drop as a function of time. This life of the cathodes depends a lot on the quantity and the nature of the residual gases present in the closed structure constituting the screen.

When operating such a screen at micropoints, the electronic bombardment of the anode produces gases by a very dependent degassing effect of the nature of the phosphors that includes the anode. he is now well demonstrated that the fall of the current of electrons emitted by the cathode is essentially caused by oxidation of the emissive material constituting the microtips. This oxidation caused by the desorbed gases is particularly evident when the microtips are in molybdenum.

Depending on the nature of the phosphors used, this oxidation is more or less intense. In the case color screens that use three phosphors different to obtain emissions in the red, the green and blue, oxidation is usually important and leads to short life spans, less than 100 hours.

We therefore try to avoid the oxidation of emissive material. Three approaches to try to solve this problem are possible.

According to a first approach, we can think to use an emissive material insensitive to oxidation. It's a long-term approach because today only molybdenum allows the realization of functional cathodes.

According to a second approach, one can use a material that is sensitive to oxidation, such as molybdenum in the presence of non-oxidizing phosphors. This is possible in the case of monochrome screens in using ZnO as the phosphor. However, in the case color screens this imposes very constraints severe on the choice of phosphors and proves today very penalizing.

According to a third approach, one can use a material that is sensitive to oxidation (such as molybdenum) in the presence of oxidizing phosphors but creating in the interior volume of the screen a reducing atmosphere likely to combat this oxidation and maintain the emissive material in its most favorable state. This third approach is particularly interesting because it allows to use molybdenum as an emissive material while retaining many possibilities of choice among phosphors.

In its classic applications, the role of a getter is to maintain the vacuum that is to say of replace a vacuum pump. In the case of a flat screen field emission, it has been proposed to use a getter to perform a dual function: to pump the oxidizing gases (which is its usual role) and maintain a hydrogen partial pressure.

• à faire absorber à un getter une quantité suffisante et contrôlée d'hydrogène dans une enceinte spéciale,
• à introduire le getter ainsi hydrogéné dans l'écran plat avant la phase d'assemblage de cet écran, et
• à assembler l'écran en le chauffant pendant environ 20 minutes à environ 450°C pour relâcher l'hydrogène à l'intérieur de l'écran.

The company SAES GETTERS SPA, which specializes in the manufacture of getters, has developed and qualified materials capable of playing this dual role. Thus, its international patent application WO-A-96/01492 discloses a method of implementation consisting of:

• to make a getter absorb a sufficient and controlled quantity of hydrogen in a special chamber,
• introducing the thus hydrogenated getter into the flat screen before the assembly phase of this screen, and
• to assemble the screen by heating it for about 20 minutes at about 450 ° C to release the hydrogen inside the screen.

Document FR-A-2 755 295 describes a refinement to this process to remedy the loss of hydrogen during the assembly phase of the screen.

An atmosphere of hydrogen allows actually stabilize the current in the screens trichromes for a few thousand hours. This However, the hydrogen-based process has the following disadvantages.

Getters likely to maintain a sufficient hydrogen pressure are specific and have a relatively low pumping capacity vis-à-vis other oxidizing gases. The quantity of getter to introduce is important (about 0.5 g for a 5-inch screen), which can cause problems cost and congestion, especially in the area of big screens.

In addition, the amount of hydrogen that the getter must first adsorb is quite considerable (1333 cm ³ Pa to 13330 cm ³ .Pa, ie 10 to 100 cm ³ .Torr per gram of getter) which, taking into account the volume of the screen, can cause the manufacturer to assemble the screen under a hydrogen pressure close to the atmosphere.

These conditions are difficult to work on an industrial level and pose in particular difficult security issues that can not be controlled only by a significant extra cost.

Presentation of the invention

It is proposed according to the present invention to overcome the drawbacks of the prior art, by the use of a gas of the type N _x H _y as claimed in claim 1, preferably ammonia NH ₃ , as reducing gas at instead of hydrogen. A partial pressure of NH ₃ makes it possible to avoid the oxidation of the tips and thus to ensure a long life for the cathodes.

This gas N _x H _y is not pumped or very little pumped getters and is therefore compatible with getters known to the skilled artisan that have very good pumping characteristics. It also has the advantages of being very low in toxicity, non-explosive and not posing any safety problem. It can therefore be easily used industrially.

A first object of the invention consists of a device comprising at least one field-effect electron source in a closed structure delimiting an internal space which contains a reducing gas intended to combat the oxidation of the emissive material of the source of energy. electrons, characterized in that the reducing gas comprises a gas of formula N _x H _y or a gaseous mixture based on N _x H _y with x = 1 and y = 3 or x = 2 and y = 4. Advantageously, the gas The reducing agent is at a pressure of between 10 ^-8 mbar and 10 ^-3 mbar and, preferably, at a pressure of between 10 ^-8 mbar and 10 ^-5 mbar.

Preferably, the gas of formula N _x H _y is NH ₃ .

The device may further comprise a or several getters in communication with the space internal device.

The closed structure can be constituted of a first blade supporting a cathode to microtips on its internal face to the structure, a second blade placed vis-à-vis the first blade and supporting an anode on its inner side to the structure, and means of sealing the first blade to the second blade on their periphery. of the phosphors can be further spread over the anode. This is for example a flat screen of viewing.

• assemblage des différents éléments constituant le dispositif pour obtenir ladite structure fermée, au moins un queusot de pompage communiquant avec ledit espace interne étant prévu ;
• raccordement du queusot de pompage à un appareil comprenant des moyens pour faire le vide et des moyens pour injecter ledit gaz réducteur ;
• mise sous vide dudit espace interne par les moyens pour faire le vide ;
• étuvage du dispositif à une température et pour une durée permettant son dégazage, la mise sous vide dudit espace interne étant poursuivie ;
• arrêt des moyens pour faire le vide ;
• introduction dudit gaz réducteur dans ledit espace interne par les moyens pour injecter le gaz réducteur sous la pression désirée ;
• fermeture du queusot.

A second object of the invention consists in a method of manufacturing such a device, comprising the following steps:

• assembling the various elements constituting the device to obtain said closed structure, at least one pumping tube communicating with said internal space being provided;
• connecting the pump tube to an apparatus comprising means for evacuating and means for injecting said reducing gas;
• evacuating said internal space by the means for evacuating;
• stoving the device at a temperature and for a duration allowing its degassing, the evacuation of said internal space being continued;
• stopping the means to evacuate;
• introducing said reducing gas into said internal space by the means for injecting the reducing gas under the desired pressure;
• closing of the queusot.

• assemblage des différents éléments constituant le dispositif pour obtenir ladite structure fermée, au moins un queusot de pompage communiquant avec ledit espace interne étant prévu ;
• raccordement du queusot de pompage à un appareil comprenant des moyens pour faire le vide et des moyens pour injecter ledit gaz réducteur ;
• mise sous vide dudit espace interne par les moyens pour faire le vide ;
• étuvage du dispositif à une température et pour une durée permettant son dégazage, la mise sous vide dudit espace interne étant poursuivie ;
• introduction dudit gaz réducteur dans ledit espace interne sous la pression désirée par les moyens pour injecter le gaz réducteur, les moyens pour faire le vide fonctionnant toujours ;
• fermeture du queusot.

A third object of the invention consists of another method of manufacturing such a device, comprising the following steps:

• assembling the various elements constituting the device to obtain said closed structure, at least one pumping tube communicating with said internal space being provided;
• connecting the pump tube to an apparatus comprising means for evacuating and means for injecting said reducing gas;
• evacuating said internal space by the means for evacuating;
• stoving the device at a temperature and for a duration allowing its degassing, the evacuation of said internal space being continued;
• introducing said reducing gas into said internal space under the pressure desired by the means for injecting the reducing gas, the means for evacuating still operating;
• closing of the queusot.

• introduction d'au moins un getter dans le queusot avant son raccordement sur ledit appareil,
• activation du getter avant ou après l'introduction du gaz réducteur.

For these two processes, if the device comprises sealing means acting hot, the assembly step takes place under vacuum or controlled atmosphere, by heating to the action temperature of the sealing means. Advantageously, once the baking step is over, the device is brought back to ambient temperature and is put into operation for a predetermined period of time before the other steps are carried out. The methods may further include the steps of:

• introducing at least one getter into the exhaust pipe before it is connected to said apparatus,
• activation of the getter before or after the introduction of the reducing gas.

The getter can also be activated after the closing of the queusot.

• une canalisation susceptible d'être raccordée audit queusot par l'une de ses extrémités,
• des moyens pour faire le vide communiquant avec l'autre extrémité de la canalisation grâce à une première vanne,
• une source de N_xH_y communiquant avec ladite canalisation grâce à des moyens intermédiaires,
• des moyens de mesure de la pression régnant dans l'espace interne du dispositif.

A fourth object of the invention consists of an apparatus for implementing these two methods, comprising:

• a pipe capable of being connected to said pipe by one of its ends,
• means for evacuating communicating with the other end of the pipe through a first valve,
• a source of N _x H _y communicating with said pipe through intermediate means,
• means for measuring the pressure prevailing in the internal space of the device.

For the implementation of the first method mentioned above, the intermediate means may comprise a gas tank communicating with said pipe through a second valve and with the source of N _x H _y through a third valve, measuring means being provided for measuring the pressure in the tank.

For the implementation of the second method cited above, intermediate means may just understand a valve.

• positionnement relatif, dans une enceinte étanche, des différents éléments constituant le dispositif en vue d'obtenir ladite structure fermée, le dispositif comportant des moyens de scellement agissant à chaud ;
• mise sous vide de l'intérieur de l'enceinte étanche par des moyens pour faire le vide ;
• étuvage des différents éléments constituant le dispositif positionnés dans l'enceinte étanche, la mise sous vide de l'enceinte étanche étant poursuivie, l'étuvage étant mené à une température et pour une durée permettant le dégazage desdits différents éléments ;
• éventuellement, arrêt des moyens pour faire le vide ;
• introduction dudit gaz réducteur à l'intérieur de l'enceinte étanche sous la pression désirée pour l'espace interne du dispositif ;
• assemblage du dispositif par scellement en élevant la température des moyens de scellement.

A fifth object of the invention consists of another method of manufacturing such a device, comprising the following steps:

• relative positioning, in a sealed chamber, of the various elements constituting the device to obtain said closed structure, the device comprising sealing means acting hot;
• evacuating the interior of the sealed enclosure by means for evacuating;
• steaming of the various elements constituting the device positioned in the sealed enclosure, the evacuation of the sealed chamber being continued, the stoving being conducted at a temperature and for a duration permitting the degassing of said various elements;
• possibly, stop means to evacuate;
• introducing said reducing gas into the sealed enclosure at the desired pressure for the internal space of the device;
• assembly of the device by sealing by raising the temperature of the sealing means.

• positionnement relatif, dans une enceinte étanche, des différents éléments constituant le dispositif en vue d'obtenir ladite structure fermée, le dispositif comportant des moyens de scellement agissant à chaud, un trou prévu dans le dispositif étant destiné à mettre en communication l'espace interne de la structure fermé et l'intérieur de l'enceinte étanche ;
• mise sous vide ou sous atmosphère contrôlée de l'intérieur de l'enceinte étanche par des moyens appropriés ;
• étuvage des différents éléments constituant le dispositif positionnés dans l'enceinte étanche, la mise sous vide ou sous atmosphère contrôlée de l'intérieur de l'enceinte étanche étant poursuivie, l'étuvage étant mené à une température et pour une durée permettant le dégazage desdits différents éléments ;
• assemblage du dispositif par scellement en élevant la température des moyens de scellement, la mise sous vide ou sous atmosphère contrôlée de l'intérieur de l'enceinte étanche étant poursuivie ;
• éventuellement, mise sous vide de l'intérieur de l'enceinte étanche si celle-ci n'était pas sous vide ;
• introduction dudit gaz réducteur à l'intérieur de l'enceinte étanche pour obtenir la pression désirée dans l'espace interne du dispositif ;
• bouchage dudit trou de communication. Dans ce cas, les étapes d'étuvage et d'assemblage peuvent être menées simultanément.

A sixth object of the invention consists of yet another method of manufacturing such a device, comprising the following steps:

• relative positioning, in a sealed enclosure, of the various elements constituting the device to obtain said closed structure, the device comprising sealing means acting hot, a hole provided in the device being intended to put in communication the internal space the closed structure and the interior of the sealed enclosure;
• evacuation or controlled atmosphere of the interior of the sealed enclosure by appropriate means;
• baking the various elements constituting the device positioned in the sealed chamber, the vacuum or controlled atmosphere of the interior of the sealed chamber being continued, the baking being conducted at a temperature and for a period allowing degassing said different elements;
• assembly of the device by sealing by raising the temperature of the sealing means, the evacuation or under controlled atmosphere of the interior of the sealed chamber being continued;
• optionally, evacuation of the interior of the sealed enclosure if it was not under vacuum;
• introducing said reducing gas into the sealed enclosure to obtain the desired pressure in the internal space of the device;
• plugging said communication hole. In this case, the parboiling and assembly steps can be carried out simultaneously.

• une enceinte étanche apte à recevoir ledit dispositif,
• des moyens pour faire le vide communiquant avec l'intérieur de l'enceinte grâce à une première vanne,
• une source de N_xH_y communiquant avec l'intérieur de l'enceinte grâce à une deuxième vanne,
• des moyens de mesure de la pression régnant à l'intérieur de l'enceinte.

A seventh object of the invention consists of an apparatus for implementing the latter two methods, comprising:

• a sealed enclosure adapted to receive said device,
• means for evacuating communicating with the interior of the enclosure through a first valve,
• a source of N _x H _y communicating with the interior of the enclosure through a second valve,
• means for measuring the pressure prevailing inside the enclosure.

If necessary, this device may also include means of producing a controlled atmosphere communicating with the interior of the enclosure thanks to a third valve connected to means of production of the controlled atmosphere, example an appropriate gas bottle.

Brief description of the drawings.

• la figure 1, déjà décrite, est une vue partielle et en coupe transversale schématique d'un écran de visualisation à micropointes selon l'art antérieur,
• la figure 2 est une vue schématique d'un premier appareil pour la mise en oeuvre d'un procédé de fabrication d'un dispositif selon la présente invention,
• la figure 3 est une vue schématique d'un deuxième appareil pour la mise en oeuvre d'un autre procédé de fabrication d'un dispositif selon la présente invention.

The invention will be better understood and other advantages and particularities will appear on reading the following description, given by way of non-limiting example, accompanied by the appended drawings among which:

• FIG. 1, already described, is a partial schematic cross-sectional view of a microtip display screen according to the prior art,
• FIG. 2 is a schematic view of a first apparatus for implementing a method of manufacturing a device according to the present invention,
• Figure 3 is a schematic view of a second apparatus for carrying out another method of manufacturing a device according to the present invention.

Detailed description of embodiments of the invention

According to the invention, the particular choice of gas N _x H _y , or of a gaseous mixture based on N _x H _y , makes it possible at the same time to combat the oxidation of the emissive material of the electron-emitting source while avoiding deposits on the emissive material. Indeed, the possible decomposition of this gas is in gaseous form unlike other types of reducing gases (CH ₄ , H ₂ S for example).

Several examples of manufacturing a device according to the invention will now be described.

• le getter "flashable" au baryum référencé sous la marque déposée ST 14,
• le getter au zirconium activable à haute température (environ 800°C), référencé sous la marque déposée ST 171,
• le getter au zirconium-fer activable à basse température (environ 400°C), référencé sous la marque déposée ST 122.

Among the getters that will eventually be used, mention may be made of those marketed by SAES GETTERS SpA, for example:

• the "flashable" barium-type getter referenced under the trademark ST 14,
• the zirconium getter which can be activated at high temperature (approximately 800 ° C.), referenced under the trademark ST 171,
• the zirconium-iron getter which can be activated at low temperature (approximately 400 ° C.), referenced under the trademark ST 122.

Example 1

A microtip screen 20, of the type shown in Figure 1, for example 6 inches (15.25 cm) diagonal is assembled under vacuum or under controlled atmosphere by heating at a temperature between 450 and 500 ° C for a period of approximately 1 hour. It is equipped with at least one pumping pipe 21 open. The sealing wall 22 of the two blades of the device consists of a low-point glass fusion called "fried glass".

After sealing and return to the atmosphere, at least one getter 23, for example of type ST 171, is introduced inside the queuing 21.

The device 20 is then placed in a zone 30 of the apparatus shown in FIG. allowing to steam it. The queusot 21 is connected to a pipe 41 which makes it possible to connect it to a vacuum pump 42 turbomolecular type via a pipe 43 equipped with a valve 44 on the one hand and the outlet of a gas tank 45, volume known (for example 0.7 ℓ), via a pipe 46 fitted with a valve 47 on the other hand.

A bottle of NH ₃ 48 is connected to the inlet port of the tank 45 via a pipe 49 equipped with a valve 50. This valve 50 is a needle valve which allows easy adjustment of the flow rate.

The apparatus thus constituted still comprises a gauge 51, for measuring the pressure of the gas contained in the tank 45, and a gauge 52 to measure the pressure at the exit of the screen 20.

The procedure is as follows.

The screen 20 and the tank 45 are put under empty, the valves 44 and 47 being open and the valve 50 being closed, thanks to the vacuum pump 42. The screen 20 is then parboiled at 360 ° C for 16 hours. After cooling to room temperature, the screen 20 is operated for 20 hours. After stopping this phase of operation which allowed the degassing of the phosphors, the getter 23 (or getters) is enabled by radiofrequency heating to a temperature of 800 ° C for 4 minutes.

The reservoir 45 is then isolated by closing the valve 47. Ammonia is introduced in the tank 45.

The screen 20 is then isolated from the vacuum pump 42 by closing the valve 44. The valve 47 is then opened and the ammonia is introduced into the screen 20 at an equilibrium pressure which depends on the quantity introduced. in the reservoir 45 and which is preferably between 10 ^-8 and 10 ^-5 mbar. The screen 20 can then be separated from the apparatus by closing the exhaust pipe 21.

Example 2

According to a variant of Example 1, NH ₃ can be introduced into the screen in dynamic mode.

For this, after the activation phase of the getter, a partial pressure of NH ₃ is regulated by the valve 50, the valves 44 and 47 being open.

The partial pressure of NH ₃ is preferably between 10 ^-8 and 10 ^-5 mbar. After a period of dynamic scanning from a few minutes to a few tens of minutes, the screen is separated from the device by closing the exhaust.

Example 3

According to another method of implementation, the assembly of the screen can be of integral type, this which means that the screen is degassed then sealed under empty or controlled atmosphere. The process is such after sealing it remains under vacuum, or under Controlled atmosphere, by difference with the case (Examples 1 and 2) for which, after sealing, the screen is put back to the pressure atmospheric and then repumped and parboiled.

We can then proceed in the same way next.

The different elements of the screen (blade supporting the cathode, blade supporting the anode, glass sealing, getters, etc.) are positioned under empty then parboiled at a temperature of the order of 300 to 450 ° C for one or more hours. Getters can be positioned either inside the screen, either in an outgrowth of the type that is closed or box to getter. During the parboiling phase, the anode can be pressed against the cathode or maintained at a certain distance from the cathode. In this last case, degassing is more efficient.

These operations take place in a apparatus diagrammatically shown in FIG. which includes a waterproof enclosure 60 allowing parboiling and assembly of the emission device field. This enclosure 60 is equipped with means appropriate electrical and mechanical the assembly of the device and its parboiling.

The apparatus of FIG. 3 also comprises a turbomolecular vacuum pump 62 which communicates with the interior of the enclosure 60 by means of a pipe 63 equipped with a valve 64. A bottle of NH ₃ 65 communicates with the interior of the the enclosure 60 through a pipe 66 equipped with a valve 67. A gauge 68 makes it possible to measure the pressure prevailing in the sealed enclosure 60. A pipe 71 equipped with a valve 72 also makes it possible to communicate the interior of the the chamber 60 with a bottle 73 in the case where we want to put the interior of the chamber under controlled atmosphere.

After the stoving phase, a pressure of NH ₃ of between 10 ^-8 and 10 ^-3 mbar is introduced into the enclosure 60 containing the screen.

The anode and cathode plates are brought into contact by means of the sealing glass, if they were not already in use, and the screen is sealed under the pressure of NH ₃ previously established at a temperature of between 450.degree. ° C and 500 ° C.

Depending on the type of getter used, this one must be "flashed" or activated after closing and return to room temperature. He can be advantageous to use a ST type 122 getter that can activate during the assembly phase.

Example 4

According to a variant of the embodiment described in example 3, one of the elements of the screen (cathode blade, anode blade, getter box) has a hole, of a diameter of the order of millimeter or a few millimeters, which allows porting the inside of the screen and the inside of the waterproof enclosure 60.

As for example 3, the different screen elements are positioned under vacuum then steamed.

The sealing phase can be done here under controlled atmosphere, which is advantageous when using a borosilicate glass for the blades of the screen, the speaker being repompered after the assembly of the screen.

This embodiment can be advantageous even when the sealing is done under vacuum because all degassed products inside the screen during sealing are evacuated, which allows to have a empty better inside the screen.

After the sealing phase, cooling and eventual repumping, an NH ₃ pressure of a few 10 ^-8 to 10 ^-3 mbar is introduced into the enclosure and therefore in the screen. The communication hole between the screen and the enclosure is then closed by any appropriate means.

In this embodiment, it can be advantageous to use getters of the same type as those of Example 3.

Claims (21)

1. A device (1) comprising at least one field effect electron source (5) within a sealed structure, which encompasses an internal space (11) that contains a reducing gas whose purpose is to prevent oxidation of the emissive material of the electron source, characterized in that the reducing gas comprises a gas with the formula N_xH_y or a gaseous mixture based on N_xH_y with x = 1 and y = 3 or x = 2 and y = 4.
2. A device according to claim 1, characterized in that the reducing gas is under a pressure of between 10^-8 and 10^-3 mbar.
3. A device according to claim 2, characterized in that the reducing gas is under a pressure of between 10^-8 and 10^-5 mbar.
4. A device according to any of claims 1 to 3, characterized in that the gas with formula N_xH_y is NH₃.
5. A device according to any of claims 1 to 4, characterized in that it comprises, in addition, one or several getters (13) that are connected to the internal space (11) of the device (1).
6. A device according to any of claims 1 to 5, characterized in that the said sealed structure comprises a first strip (3) bearing a microdot cathode (5) on its internal structural face, a second strip (2) placed opposite the first strip (3) and bearing an anode (9) on its internal structural face, and the means (4) of sealing the first strip to the second strip around their edges.
7. A device according to claim 6, characterized in that it comprises, in addition, luminophors (10) spread out over the anode (9).
8. A manufacturing process for a device according to any of claims 1 to 7, comprising the following stages:

   the various parts that make up the device (20) are assembled in order to obtain the said sealed structure, it being provided with at least one evacuation exhaust tube (21) that is connected to the said internal space,

   the evacuation exhaust tube (21) is connected to an apparatus that is equipped with the means of providing a vacuum (42) and the means for injecting the said reducing gas (48),

   the said internal space is placed under vacuum by means of the vacuum apparatus (42),

   the device (20) is heated to a temperature and for sufficient time to allow it to be de-gassed, while the vacuum in the said internal device is maintained,

   the vacuum apparatus (42) is stopped,

   the said reducing gas is introduced to the desired pressure into the said internal space by the apparatus for injecting the reducing gas,

   the exhaust tube (21) is sealed off.
9. A manufacturing process for a device according to any of claims 1 to 7, comprising the following stages:

   the various parts that make up the device (20) are assembled in order to obtain the said sealed structure, with at least one evacuation exhaust tube (21) connected to the said internal space being provided,

   the evacuation exhaust tube (21) is connected to an apparatus that is equipped with the means of providing a vacuum (42) and the means for injecting the said reducing gas (48),

   the said internal space is placed under vacuum by means of the vacuum apparatus (42),

   the device (20) is heated to a temperature and for sufficient time to allow it to be de-gassed, while the vacuum (42) in the said internal device is maintained,

   the said reducing gas is introduced to the desired pressure into the said internal space by means of the apparatus for injecting the reducing gas (48), with the vacuum apparatus (42) still operating,

   the exhaust tube (21) is sealed off.
10. Process according to either of claims 8 or 9, characterized in that, with the device provided with the means for sealing at high temperature, the assembly stage takes place under vacuum or under a controlled atmosphere, through heating up to the temperature at which the means used for sealing is activated.
11. Process according to any of claims 8 to 10, characterized in that, once the heating stage is finished, the device (20) is cooled down to ambient temperature and operated for a given period before carrying out the other stages.
12. Process according to any of claims 8 to 11, characterized in that it comprises, in addition, the following stages:

    the introduction of at least one getter (23) into the exhaust tube (21) before it is connected up to the said apparatus,

    the activation of the getter (23) before or after the introduction of the reducing gas.
13. Process according to claim 12, characterized in that the getter is activated after the exhaust tube has been sealed off.
14. An apparatus for implementing the process according to any of claims 8 to 13, comprising:

    a pipe (41) that can be connected up to the said exhaust tube (21) by one of its ends,

    means for providing a vacuum (42), connected up to the other extremity of the pipe (41) by means of a first valve (44),

    a source of N_xH_y (48), connected to the said pipe (41) via intermediary devices,

    an apparatus (52) for measuring the pressure within the internal space of the device.
15. An apparatus according to claim 14, characterized in that the intermediate devices comprise a gas reservoir (45) connected to the said pipe (41) via a second valve (47) and to the source of N_xH_y (48) by means of a third valve (50), with an apparatus (51) for measuring the pressure within the reservoir being provided.
16. An apparatus according to claim 14, characterized in that the intermediate devices comprise a valve.
17. A manufacturing process for a device according to any of claims 1 to 7, comprising the following stages:

    the various parts making up the device are put in position in relation to each other within an airtight enclosure (60), in order to obtain the said sealed structure, with the device provided with the means for sealing at high temperature,

    the interior of the airtight enclosure (60) is placed under vacuum using the vacuum apparatus (62),

    the various parts making up the device, placed in position within the airtight enclosure (60), are heated with the airtight enclosure being kept under vacuum, and the heating being up to a temperature and for sufficient time to allow the various parts to be de-gassed,

    if necessary, the vacuum apparatus (62) is stopped,

    the said reducing gas is introduced into the interior of the airtight enclosure (60) at the pressure desired for the internal space of the device,

    the device is assembled by sealing by heating up the means used for sealing.
18. A manufacturing process for a device according to any of claims 1 to 7, comprising the following stages:

    the various parts making up the device are placed in position in relation to each other within an airtight enclosure (60), in order to obtain the said sealed structure, with the device provided with the means for sealing at high temperature, and a hole being provided in the device whose purpose is to connect the internal space of the sealed structure and the airtight enclosure (60),

    the interior of the airtight enclosure (60) is placed under vacuum or a controlled atmosphere using appropriate means,

    the various parts making up the device, placed in position within the airtight enclosure (60), are heated with the airtight enclosure being kept under vacuum or under a controlled atmosphere, and the heating being up to a temperature and for sufficient time to allow the various parts to be de-gassed,

    the device is assembled by sealing by heating up the means used for sealing, with the vacuum or controlled atmosphere within the interior of the airtight enclosure (60) being maintained,

    if necessary, the interior of the airtight enclosure (60) is placed under vacuum,

    the said reducing gas is introduced into the interior of the airtight enclosure (60) in order to obtain the desired pressure within the internal space of the device,

    the connecting hole is sealed off.
19. Process according to claim 18, characterized in that the heating and assembly stages are carried out simultaneously.
20. An apparatus for implementing the process according to claims 17 to 19, comprising:

    an airtight enclosure (60) capable of encompassing the said device,

    a vacuum apparatus (62) connected to the interior of the enclosure via a first valve (64),

    a source of N_xH_y (65) connected to the interior of the enclosure (60) via a second valve (67),

    an apparatus (68) for measuring the pressure within the interior of the enclosure (60).
21. An apparatus according to claim 20, characterized in that it comprises, in addition, the means for producing a controlled atmosphere, which is connected to the interior of the enclosure (60) via a third valve.

Images