WO2000028568A1 - Dispositif getter evaporable avec perte reduite des particules, et son procede de production - Google Patents

Dispositif getter evaporable avec perte reduite des particules, et son procede de production Download PDF

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Publication number
WO2000028568A1
WO2000028568A1 PCT/IT1999/000359 IT9900359W WO0028568A1 WO 2000028568 A1 WO2000028568 A1 WO 2000028568A1 IT 9900359 W IT9900359 W IT 9900359W WO 0028568 A1 WO0028568 A1 WO 0028568A1
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WO
WIPO (PCT)
Prior art keywords
container
metallic member
powders
wall
cylindrical side
Prior art date
Application number
PCT/IT1999/000359
Other languages
English (en)
Italian (it)
Inventor
Daniele Martelli
Giuseppe Urso
Original Assignee
Saes Getters S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saes Getters S.P.A. filed Critical Saes Getters S.P.A.
Publication of WO2000028568A1 publication Critical patent/WO2000028568A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
    • H01J7/186—Getter supports

Definitions

  • the present invention deals with an evaporable getter device with reduced loss of particles and a process for producing the same.
  • the evaporable getter devices are known and since long used for the maintenance of the vacuum within TV picture tubes or computer displays.
  • .an evaporable getter device comprises a mixture of powders of nickel (Ni) and of the compound BaAl 4 .
  • the device introduced in the picture tube before evacuation and sealing thereof, is then heated from the outside by means of radiofrequencies; during this operation, barium evaporates and deposits onto the inner walls of the picture tube in the form of a very thin film being the active element of the maintenance of vacuum.
  • Evaporable getter devices are described in a number of patents, among which for example the US patents 2,824,640; 2,907,451; 3,225,911; 3,381,805; 3,558,962; 3,719,433; 4,077,899; 4,134,041; 4,154,162; 4,665,343; 4,642,516; 4,961,040 and 5,118,988.
  • the devices disclosed by these patents are different from each other by construction of details, but are all essentially formed of a circular metallic holder (generally of steel) open at the upper side, wherein a seat of the mixture of powders is provided.
  • a seat may occupy all the surface available, thus resulting in a cylindrical volume to be filled with the powders, or may define a circular crown, generally of rectangular cross-section, whereby the volume available for the filling with the powders has the shape of an annular channel.
  • the desired quantity of powder mixture Ni-BaAl 4 is poured into the corresponding seat of the metallic holder and is compressed in this seat by means of a special shaped punch at pressure values of some tons per square centimeter, thus forrning a compact packet.
  • the punch has a diameter slightly smaller than the inner diameter of the holder, otherwise its lateral surface would seize up against the inner walls of the holder, with consequent difficulties in removing the finished device from the punch; therefore there is a "elegance", generally of about 100 ⁇ m, between the side surface of the punch and the corresponding surfaces of the seat of the powders.
  • the nickel powders used in the production of evaporable getter devices have generally a particle size of less than 60 ⁇ m, and those of BaAL generally lower than 250 ⁇ m; consequently it may happen that grains of powder remain sticking to the side walls of the device, without being dragged downwards by the punch, and in any case the most external portion of the packet surface, corresponding to the "clearance" between punch and holder, proves to be very little compressed and of poor mechanical stability; these loose grains of powder or an inadequately compressed portion of the packet can give rise to a loss of particles from these devices at the inside of the picture tubes.
  • Particles of powder at the inside of a picture tube cause a number of problems: the particles may deposit onto the electron gun of the picture tube, thus altering its correct operation, or they may interfere with the high electric fields generated when the picture tube is working, or finally may obstruct some of the holes in the mask at the inside of picture tubes in the proximity of the screen, thus producing dark spots in the image formed thereon. Particularly felt by the manufacturers of picture tubes is the latter problem, essentially due to the particles having sizes of more than 50 ⁇ m.
  • an evaporable getter device comprising:
  • an upperly open metallic container formed of an essentially flat bottom wall and at least a cylindrical side wall essentially perpendicular to said bottom wall;
  • FIGURE 1 shows a first device according to the invention
  • FIGURE 2 shows a cross-section view along a diameter of the device illustrated in Fig. 1 ;
  • FIGURE 3 shows a perspective view of a possible metallic member to be employed in the devices of the invention
  • FIGURE 4 shows a perspective view of a second possible metallic member to be employed in the devices of the invention
  • FIGURE 5a shows a cross-section view along a diameter of a device according to the invention comprising the metallic member of Fig. 4 in an intermediate step of production;
  • FIGURE 5b shows a finished device of the invention in a view similar to that of Fig. 5a;
  • FIGURE 6 shows a second possible device of the invention
  • FIGURE 7 shows a cross-section view along a diameter of a device of the type shown in Fig. 6
  • FIGURE 8 shows a perspective view of a metallic member to be used in a device of the type shown in Fig. 6;
  • FIGURE 9 schematically shows a system for measuring the loss of particles from evaporable getter devices.
  • a first possible evaporable getter device 10 of the invention is shown, respectively in a perspective and a cross-sectional view, being of the type wherein the packet of powders of nickel and BaAl 4 occupies the whole surface of the device in a top plan view.
  • This device comprises a container 11, generally formed by cutting and cold pressing a metal sheet; sheet steel AISI 304 is generally employed, with a thickness between about 0.08 and 0.35 mm.
  • the container is formed so as to have an essentially flat bottom wall 12 and a cylindrical side wall 13 perpendicular to the wall 12, thus defining a seat of essentially cylindrical geometry for the packet 14 of mixed powders of nickel and BaAl 4 .
  • a metallic member generally defined as member 16 in all the possible geometrical variations described in the following.
  • member 16 Two possible embodiments of the member 16 are shown in Figs. 3 and 4.
  • this member in a top plan view, has the shape of a circular crown, whereas its cross-section may be essentially flat as shown in Fig. 3, but preferably has the shape of Fig. 4, essentially defined by two main surfaces, one flat and one frustoconical, with the portion having a flat surface joined to the one with frustoconical surface along the smaller circumference of the latter.
  • the longer diameter of the member 16 has the same length as the inner diameter of container 11, while its smaller diameter is slightly shorter than the longer one, generally 1 mm less, whereby the surface 15 results to be almost completely free and the barium evaporation is not obstructed.
  • Figs. 5a and 5b show a device of the invention in two different production steps, as an example of use of member 16 of Fig. 4 having the preferred shape.
  • member 16 is inserted into the container 11 after having introduced in the latter the desired quantity of powdered nickel and BaAl 4 , before compressing the powders to form packet 14.
  • the member 16, pushed downwards by a punch scrapes the inner surface of wall 13, dragging together with it the particles, if any, which on the contrary would not be contacted by the punch, the diameter of which, as stated above, is slightly shorter than the inner diameter of container 11.
  • member 16 is compressed into the packet 14 with the portion with planar surface emerging with respect to the free surface 15 of packet 14 and parallel thereto, with the outer edge contacting the side wall 13; with this arrangement member 16 occupies the area corresponding to the "clearance" between the side surface of punch and wall 13, thus eliminating the zone of powders poorly compressed existing in the known devices, which is the main source of loose particles.
  • the metallic member 16 of Fig. 3, of flat geometry, is capable of carrying out the functions of cleaning the inner surface of the container and holding down the powders, but it could be detached from the device in consequence of knocks (for example during transportation); the preferred member 16, shown in Fig.
  • the member 16 is made of metal: among the preferred metals there are steel, e.g. the same AISI 304 steel employed for the production of the container, or nickeled iron, nickel or its alloys.
  • Figs. 6 and 7 show, respectively in perspective and cross-sectional view, a second possible evaporable getter device 60 of the invention; in this type of device, in a plan top view, the packet of powders of nickel and BaAl 4 occupies only an outer zone, having a circular crown shape.
  • the device comprises a container 61, made of materials and with size similar to those adopted for the container 11; the seat for the powders is defined in this container by an essentially flat bottom wall 62 and two cylindrical walls 63 and 64, essentially WHAT IS CLAIMED IS:
  • a method of fabricating an MIS transistor comprising the steps of: a) providing a monocrystalline silicon substrate having a major surface, b) cleaning said major surface, c) placing the substrate in an atmosphere of a nitrogen compound at a pressure above one atmosphere, d) heating the substrate and forming a nitride layer on said major surface,
  • step c) includes a nitrogen compound selected from the group consisting of nitric oxide (NO) and ammonia (NH 3 ).
  • step d) includes heating the substrate at a temperature in the range of 600° - 900°C for a period of time in the range of 5 - 20 minutes.
  • step f) includes heating the substrate at a temperature in the range of 600° - 900°C for a period of time in the range of 10 - 60 minutes.
  • step g) includes forming a layer of doped polysilicon on the nitride layer and etching the layer of polysilicon , nitride layer, and the silicon dioxide layer to form the gate electrode.
  • step g) includes forming a layer of doped polysilicon on the nitride layer and etching the layer of polysilicon , nitride layer, and the silicon dioxide layer to form the gate electrode.
  • non-limiting examples show some embodiments designed to teach those skilled in the art how to put in practice the invention and to represent the best considered way for the accomplishment of the invention.
  • EXAMPLE 1 Ten devices of the type shown in Fig. 1 are manufactured. Each device comprises a container made of AISI 304 steel 0.18 mm thick and shaped so as to have an inner diameter of 20 mm and the side wall 13 of 4 mm in height.
  • each device Into each device a mixture is introduced comprised of 550 mg of nickel in powder having a particle size of less than 60 ⁇ m and 550 mg of powdered BaAl 4 with particle size of less than 250 ⁇ m.
  • a metallic member 16 having a planar- frustoconical geometry of the type shown in Fig. 4 is placed into each container.
  • the devices are prepared by causing the powders in the container to be compressed by a punch under a pressure of 9700 kg/cm .
  • EXAMPLE 2 (COMPARATIVE)
  • Ten evaporable getter devices are prepared, absolutely similar to the devices of Example 1, except for non comprising the metallic member 16 of planar- frustoconical geometry placed at the intersection between the free surface of the packet of powders and the inner wall of the container.
  • EXAMPLE 3 This example describes a test relating to the particles being lost from the devices of the invention prepared as in Example 1.
  • a testing apparatus schematically represented in Fig. 9, has been made, comprising a glass vessel 90 open at the top and connected, through a lower port and a rubber sleeve (not shown), to a glass conduit 91, in turn connected to a rotary pump 92.
  • a laser counter 93 of particles model SYSTEM 3116 of the German firm PAMAS GmbH; this counter of particles is capable of measuring the number of particles passing through its laser ray, separated by grains size fraction.
  • the vessel 90 is also connected, through an arm 94, to a motor 95.
  • Example 1 the ten samples prepared as in Example 1 are put into the container 90, the upper opening of which is closed by means of a filter which keeps all the particles having a size greater than 0.3 ⁇ m.
  • the pump 92 is operated so as to establish a gas flow towards the latter from the vessel 90, and subsequently the motor 95 is operated which, through arm 94, causes the vibration of vessel 90, so as to produce a loss of particles from the samples under test.
  • the particles counter 93 is put into action for detecting number and size of the particles lost from the test samples.
  • the test lasts 4 minutes, because during previous tests for the setting up of the method it has been found that after such a duration the loss of particles is negligible.
  • Table 1 wherein the number of particles is given as measured by the counter 93 in correspondence with the fraction of particles size.
  • Example 3 The test of Example 3 is repeated on samples prepared as in Example 2. The results of this test are listed in Table 1.
  • the devices of the invention have a loss of particles clearly lower than the samples of the prior art; in particular, the loss reduction is of more than 60% for the particles having a size greater than 50 ⁇ m (and more than 75% for the particles of a size greater than 100 ⁇ m), which are those causing the biggest problems in the production of picture tubes.

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  • Physical Or Chemical Processes And Apparatus (AREA)
  • Powder Metallurgy (AREA)

Abstract

L'invention concerne des dispositifs getter évaporables (10) avec une perte réduite des particules, ces dispositifs étant constitués d'un récipient métallique au sommet ouvert, ce récipient étant destiné à contenir un paquet de poudres du mélange nickel-BaA14. Les dispositifs susmentionnés comportent également un ou plusieurs éléments métalliques (16) en forme de couronne, placés en contact avec les parois latérales (13) dudit récipient au niveau de l'interface séparant ces parois et la surface libre (15) des poudres, de sorte que lesdits éléments métalliques font saillie par rapport à cette surface libre. Cette invention concerne également un procédé de préparation de ces dispositifs.
PCT/IT1999/000359 1998-11-10 1999-11-10 Dispositif getter evaporable avec perte reduite des particules, et son procede de production WO2000028568A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI98A002436 1998-11-10
ITMI982436 IT1303731B1 (it) 1998-11-10 1998-11-10 Dispositivo getter evaporabile con ridotta perdita di particelle eprocesso per la sua produzione.

Publications (1)

Publication Number Publication Date
WO2000028568A1 true WO2000028568A1 (fr) 2000-05-18

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IT (1) IT1303731B1 (fr)
WO (1) WO2000028568A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003010790A1 (fr) * 2001-06-26 2003-02-06 Saes Getters S.P.A. Dispositif getter evaporable pour tubes cathodiques
US10232302B2 (en) * 2014-06-24 2019-03-19 Panasonic Intellectual Property Management Co., Ltd. Gas-adsorbing device and evacuated insulating material using same

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB736475A (en) * 1952-09-27 1955-09-07 Apparechi Elettrici E Scient S Improvements in getter containers and a method of manufacturing such containers
GB1186581A (en) * 1966-04-28 1970-04-02 Getters Spa Improved Exothermic Getters
US3558962A (en) * 1968-12-11 1971-01-26 Union Carbide Corp High yield getter device
US3560788A (en) * 1968-12-11 1971-02-02 Union Carbide Corp R-f energizable, pan-shaped getter for television tube
US5443410A (en) * 1993-07-24 1995-08-22 Goldstar Co., Ltd. Getter fixing device for a cathode ray tube
WO1997050107A1 (fr) * 1996-06-24 1997-12-31 Philips Electronics N.V. Appareil d'aspiration a dispositif getter
EP0853328A1 (fr) * 1997-01-10 1998-07-15 SAES GETTERS S.p.A. Dispositif dégazeur frittable et évaporable à haut rendement de barium

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB736475A (en) * 1952-09-27 1955-09-07 Apparechi Elettrici E Scient S Improvements in getter containers and a method of manufacturing such containers
GB1186581A (en) * 1966-04-28 1970-04-02 Getters Spa Improved Exothermic Getters
US3558962A (en) * 1968-12-11 1971-01-26 Union Carbide Corp High yield getter device
US3560788A (en) * 1968-12-11 1971-02-02 Union Carbide Corp R-f energizable, pan-shaped getter for television tube
US5443410A (en) * 1993-07-24 1995-08-22 Goldstar Co., Ltd. Getter fixing device for a cathode ray tube
WO1997050107A1 (fr) * 1996-06-24 1997-12-31 Philips Electronics N.V. Appareil d'aspiration a dispositif getter
EP0853328A1 (fr) * 1997-01-10 1998-07-15 SAES GETTERS S.p.A. Dispositif dégazeur frittable et évaporable à haut rendement de barium

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003010790A1 (fr) * 2001-06-26 2003-02-06 Saes Getters S.P.A. Dispositif getter evaporable pour tubes cathodiques
US6873102B2 (en) 2001-06-26 2005-03-29 Saes Getters S.P.A. Evaporable getter device with metallic nets
US10232302B2 (en) * 2014-06-24 2019-03-19 Panasonic Intellectual Property Management Co., Ltd. Gas-adsorbing device and evacuated insulating material using same

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Publication number Publication date
ITMI982436A1 (it) 2000-05-10
IT1303731B1 (it) 2001-02-23

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