DE102012203261A1 - Production method for a multilayer composite and component for high-voltage insulation - Google Patents

Abstract

A manufacturing method (100) for a multilayer composite (20) comprises the following steps (110, 120, 130, 140): providing (110) a first glass layer body (11g), applying (120) a first metal layer (11m) to a surface (11s ) of the first glass layer body (11g), arranging (130) a second glass layer body (12g) on the at least partially metallized surface (11ms2) of the first glass layer body (11g) and applying (140) a pressure (p) to the arrangement of the glass layer bodies arranged to one another (11g, 12g).
A high-voltage insulation component (20) comprises a first glass layer body (11g), a second glass layer body (12g), and a first metal layer (11m) disposed between the first (11g) and second (12g) glass layer bodies, wherein a first side (11s ) of the first metal layer (11m) is diffusion welded to the first glass layer body (11g) and a second side (11ms1) of the first metal layer (11m) facing away from the first side (11ms1) is diffusion bonded to the second glass layer body (12g).

Description

The invention relates to a production method for a multilayer composite and a component for high-voltage insulation.

From the high voltage technology controlled feedthroughs are known. In this case, the course of one or more equipotential surfaces along a high-voltage conductor is fixed by means of one or more conductive layers in order to distribute a radial potential difference in the axial direction at the end of the implementation and thus to reduce field strength peaks at the end of the implementation (cf. Küchler, Hochspannungstechnik, ISBN 978-3-540-78412-8, page 100 ).

Dahms, S. et al., Estonian Journ. Eng., 2009, 15, 2, 131-142: "Substance-to-substance-joining of quartz glass" describes a method of diffusion welding glass that has long been used to join metal to metal. Diffusion welding of glass makes it possible to manufacture temperature-resistant, mechanically strong, vacuum-tight composites. By applying pressure and heat, a surface diffusion and material reaction is effected in the contacted surfaces, which joins the contacted parts into a composite.

In high-voltage engineering insulating materials with high electrical strength are needed to avoid electrical breakdowns. For many applications, in addition to a high dielectric strength, further demands are placed on the insulating material. For example, for use in X-ray tubes only high vacuum suitable insulating materials are used because the substances in the vacuum may not outgas and reduce the quality of the vacuum. In addition, thermal insulation up to 600 ° C is required of the insulators to withstand welding and annealing processes unimpaired during assembly. These requirements are met only inorganic insulating materials such as ceramics or glasses. Currently, ceramic insulating materials are predominantly used in X-ray tube construction.

Currently, uncontrolled feedthroughs made of ceramic insulating materials are used. Here, complex structures / geometries are used to extend the creepage distance at the interface. In conjunction with comparatively large dimensions and complex structures for Kriechwegverlängerung electrical feedthroughs from these technologically demanding materials are complex to manufacture and have a large space requirement.

For internal field control, external taxation of the electric field can be provided. In doing so, metallic potential controls are installed near the feedthrough in order to homogenize local field strength maxima. This method is used to optimize the field profile of the implementation and requires additional space, since the Hochspannungsisolierstrecken must be adjusted and also the functionality of the tube may not be affected. In particular, electrical fields should not be changed in terms of their strength and spatial geometry and the function of electron grids should not be impaired.

In the production of a controlled implementation of metallic Steuerbeläge must be introduced with mutually defined distances in these inorganic substances. Until now, there were no insulating materials or processes in which metallic control coatings can be introduced that are highly vacuum-compatible and can withstand the temperatures and electrical stresses that occur in the X-ray tube. For the realization of the material composite bonding methods are still unsuitable, at least from today's perspective, since they do not meet the above requirements such as thermal stability up to 600 ° C.

The object of the present invention is to provide a manufacturing method for a multilayer composite, the use of space and / or manufacturing costs for high-voltage bushings are lower when using it than with the use of known high-voltage guides.

• – Bereitstellen eines ersten Glasschichtkörpers;
• – Aufbringen einer ersten Metallschicht auf eine Oberfläche des ersten Glasschichtkörpers;
• – Anordnen eines zweiten Glasschichtkörpers auf der zumindest bereichsweise metallisierten Oberfläche der ersten Glasschichtkörpers; und
• – Beaufschlagen eines Drucks auf die Anordnung der zueinander angeordneten Glasschichtkörper.

According to the invention, this object is achieved in that the production method comprises the following steps:

• - Providing a first glass layer body;
• Applying a first metal layer to a surface of the first glass layer body;
• Arranging a second glass layer body on the at least partially metallized surface of the first glass layer body; and
• - Applying a pressure on the arrangement of the mutually arranged glass layer body.

• – einen ersten Glasschichtkörper;
• – einen zweiten Glasschichtkörper; und
• – eine zwischen dem ersten und dem zweiten Glasschichtkörper angeordnete erste Metallschicht, wobei eine erste Seite der ersten Metallschicht mit dem ersten Glasschichtkörper diffusionsverschweißt ist und eine von der ersten Seite abgewandte zweite Seite der ersten Metallschicht mit dem zweiten Glasschichtkörper diffusionsverschweißt ist.

In addition, a component according to the invention for high-voltage insulation comprises:

• A first glass layer body;
• A second glass layer body; and
• A first metal layer arranged between the first and the second glass layer body, wherein a first side of the first metal layer with the first glass layer body is diffusion-welded and a second side facing away from the first side of the first metal layer with the second glass layer body is diffusion welded.

For example, diffusion bonding can be accomplished in a hot press process to enhance diffusion at elevated temperatures and pressures. For the production of the glass-metal multilayer composite, highly insulating glass layer bodies with a local surface metallization (metal foil or metal layers applied directly) are homogeneously and flushly added at temperature treatment close to the glass transformation temperature and with corresponding pressure force application. The joining is not done by viscous flow of the glass, but mainly by thermally intensified diffusion at the contact points. The glass body used remain dimensionally stable. Macroscopic shrinkage or deformation is completely or at least largely avoided. This technique makes it possible to realize homogeneously joined glass-metal composite layers. Preferred for this purpose are glass layer bodies which have a layer thickness between 100 μm and 300 μm. After application and / or after application of the compressive force, the metal layer may have a layer density of, for example, between 90 nm and 1200 nm. The pressure at the application of the pressing force may be, for example, between 5 MPa and 20 MPa. A hold time of pressurizing may be, for example, between 2 and 20 hours. One or more of the metal layers arranged between the glass layer bodies can be used as a high voltage supply (high voltage conductor).

In order to achieve a high dielectric strength, high density glass glass body can be used. Preferably, at least one of the glass layer body consists of a glass which has a dielectric strength of at least 10 kV / mm when the AC voltage is applied. Alkali-free aluminoborosilicate glasses AF 45 or AF 32 from Schott AG are suitable for this purpose, for example. These glasses show a dielectric strength of up to 30 kV / mm with a layer thickness of 200 μm when the AC voltage is applied.

In one embodiment variant of the production method, the first and / or the second glass layer body is a glass sheet. By using a glass layer body, which is very flat in film form, a particularly space-saving construction of the high-voltage insulation is possible.

For high voltage feedthroughs can also be advantageous if the first and / or the second glass layer body is a glass tube. As a result, a cylindrically symmetrical, space-saving construction of a high-voltage feedthrough with a well predictable circumference-independent field strength distribution is possible.

A variant embodiment provides that uniaxial hot pressing takes place in the step of pressurizing the pressure. By uniaxial hot pressing a planar glass-metal multilayer composite can be realized, which can be referred to as 'planar glass-metal multilayer'. In this case, several metallized glass layer bodies are placed on each other and uniaxially pressurized at a temperature close to the glass transition temperature (which is typically about 720 ° C). Thus, by choosing an optimum pressing time and an optimal pressing pressure a planar glass insulating body can be produced with several conductive control panels.

A further embodiment provides that hot isostatic pressing takes place in the step of pressurizing the pressure. In hot isostatic pressing (HIP) in a protective gas atmosphere, all-sided pressure is applied to the workpiece at temperatures close to the glass transition temperature. To fabricate a concentric glass-metal multilayer composite ring (for example, as a controlled high-voltage feedthrough for X-ray tubes), several metallized glass tubes are centered and joined together using the hot isostatic pressing process. The nested metallized glass tubes are thus homogeneously joined together by means of a thermally intensified diffusion process. The concentric glass-metal multilayer composite ring may be referred to as a 'cylindrical glass-metal multilayer'. Thus, by selecting and applying an optimal pressing time and an optimal pressing pressure, a cylindrically symmetrical insulating glass body with several conductive control surfaces and / or live coatings can be produced. Hot isostatic pressing may alternatively or additionally be used during the pressurizing step to fabricate a planar multilayer body.

It is advantageous if the application of the metal layer by means of screen printing, electroplating, sputtering, vapor deposition and / or in sol-gel technique. With these methods, a good adhesion of the metal layer to the glass layer body can be achieved.

A further development provides that during application of the first metal layer, the first metal layer is not applied in an edge region of the glass layer body, so that in the edge region a lining edge of the first metal layer is completely embedded in glass after performing the process. Thus, a lining edge of a control layer can be enclosed by means of an additional glass rim which encloses the lining edge in a high-voltage-resistant and vacuum-tight manner after the diffusion bonding and / or fusing of the edge region.

It is preferable that the pressurization is performed at a temperature near a transformation temperature of the glass of the glass laminates. It is preferable that a temperature change rate after the step of disposing the second glass laminate body, particularly after a start of the pressurizing step, is between 1 K / min and 5 K / min. Slow heating and cooling reduce the generation of thermal stress and thus the risk of deformation or breakage.

It is particularly preferable if the method after the step of pressurizing also includes a step of tempering near the transformation temperature of the glass of the glass layer bodies. As a result, residual thermal stresses (thermal residual stresses) which may still be present in the multilayer composite, in particular in its glass layers, may be removed after the step of applying the pressure.

The invention is explained in more detail with reference to the accompanying drawings, in which:

1 Components of a planar multilayer composite in an exploded view before the step of applying a pressure to the arrangement of the mutually arranged glass layer body,

2 a flow chart for a production process for a multilayer composite,

3 a planar multi-layer composite after the step of applying a pressure to the arrangement of the superimposed glass layer body,

4 Components of a cylindrical multilayer composite in an exploded view before the step of applying a pressure to the arrangement of glass laminate body arranged to each other and

5 a cylindrical multilayer composite after the step of applying a pressure to the arrangement of glass laminate bodies arranged to one another.

The embodiments described in more detail below represent preferred embodiments of the present invention.

The exploded view of the 1 shows four glass laminates 11g . 12g . 13g . 14g in the form of glass foils. The glass foils 11g . 12g . 13g . 14g consist of glass with a high dielectric strength, for example, an alkali-free aluminoborosilicate glass (for example, from AF 45 or AF 32 Schott AG, Mainz). With applied alternating voltage and a layer thickness of 200 μm, such glasses have a dielectric strength of up to 30 kV / mm. In addition, the embodiment includes a metallic conductor 12m and two metal layers 11m . 13m , which are intended as Steuerbeläge.

The 2 shows a flowchart of a manufacturing process 100 for a multi-layer composite 20 (please refer 3 ), who in 1 comprises components shown. To prepare for in 1 shown arrangement, are in a first step 110 the glass foils 11g . 12g . 13g . 14g provided. As insulating circular, thin glass sheets can be used with a thickness of for example 200 microns. The glass sheets have a diameter d of, for example, 100 mm. The glass foils 11g . 12g . 13g . 14g be for 15 min in an ultrasonic bath in a cleaning solution cleaned. The cleaning solution can consist of equal parts of isopropanol and acetone.

In a second step 120 becomes both a surface area of the first glass sheet 11g as well as a surface area of the third glass sheet 13g each coated with a metal or a metal alloy. The resulting metal layer 11m . 13m is for example between 100 nm and 1 μm thick. The application of the metal layers 11m . 13m is preferably done by sputtering. It is on the glass sheets 11g . 13g an alloy of 95 percent by weight tungsten and 5 percent by weight titanium is applied. This alloy is refractory and therefore suitable for use at elevated temperatures. On the other hand, the composition of the alloy is such that it has a coefficient of thermal expansion which differs only slightly from a coefficient of thermal expansion of the glass used as a percentage. This minimizes thermal stresses. To achieve good adhesion of the metal to the glass sheet, methods such as screen printing, electroplating, vapor deposition or sol-gel may also be used to apply the metal or metal alloy.

In a third step 130 become the glass foils 11g . 12g . 13g . 14g arranged approximately parallel to each other surface, wherein between the second 12g and the third 13g Glass foil as metallic Head a slide 12m is inserted from a metal or a metal alloy. Thereafter, the arrangement is placed in a press die of the same size. In order to prevent adhesion to the pressing tool, molybdenum foils are placed between the die and the glasses and between the die and the die, ie along an inner circumferential surface (not shown in the figures).

In a fourth step 140 this arrangement is used in a uni-axial hot press. Slow heating and cooling at 1 K / min to 5 K / min minimize the occurrence of thermal stresses and thus a risk of deformation and / or breakage. At temperatures close to the glass transition temperature Tg, a pressure p (compressive force per area) is applied. The glass transition temperature Tg is for example between 700 ° C to 750 ° C, typically about 720 ° C. The quality of the combination depends strongly on the strength and the time course of the three parameters temperature level, holding time and pressure p. For example, the pressure p may vary between 5 MPa and 20 MPa and the hold time between 2 hours and 20 hours. By stacking several (at least partially metallized) glass sheets 11g . 12g . 13g . 14g and uniaxial hot pressing at a temperature close to the glass transition temperature Tg (typically 720 ° C) results in a planar glass-metal multilayer composite 20 , Thus, optimal temporal course of the process parameters (such as temperature level, holding time, compressive force) a monolithic glass-metal composite 30 with several conductive control panels 11m . 13m and with or without an embedded high voltage conductor 12m getting produced. By means of the pressure and temperature effect, for example, a surface of the first glass layer body 11g with a first surface 11ms1 the first metal layer 11m and a surface of the second glass laminate body 12g with a second surface 11ms2 the first metal layer 11m diffusion bonded. The layer sequences described with reference to the figures are only examples. Depending on the intended use, several glass layers or several metal layers can be directly diffusion welded together in the sequence, for example.

In a fifth step 150 becomes the glass-metal composite 20 annealed in the oven (for example for 30 minutes at 700 ° C to 720 ° C) to after the hot pressing process in the glass-metal composite 20 , in particular in its glass layers, to eliminate any residual thermal stresses still present.

The 3 shows a multilayer composite 20 after the step of applying a pressure p to the arrangement of the stacked glass sheets 11g . 12g . 13g . 14g , The pavement edges 22 are completely embedded in glass, because before compression, an additional edge of the film 24 next to the metal layers 11m . 13m (Metallizations) was released. Of course, this does not apply to the faces of inserted metallizations or metal foils 12m , which are intended as a high voltage supply (high voltage conductor).

The 4 shows components of a cylindrical multilayer composite 20 in an exploded view before applying 140 a pressure p on the arrangement of the mutually arranged cylindrical glass layer body 11g . 12g , In this case, a hot isostatic pressing method will preferably be used. By hot isostatic pressing (HIP) in a protective gas atmosphere all-round pressure is applied to the workpiece at temperatures close to the glass transition temperature Tg. For the production of a concentric glass-metal multilayer composite ring 20 (For example, as a controlled high-voltage bushing for X-ray tubes) are several glass rings 11g . 12g which are at least partially metallized, arranged centrally one inside the other and joined together using the hot isostatic process. By a thermally intensified diffusion process, the metallized glass rings 11g . 12g homogeneously joined together. The cylindrical glass layer body 11g . 12g can be tube sections made of glass.

The 5 shows the cylindrical multilayer composite 20 after the step 140 the application of a pressure p to the arrangement of the mutually arranged cylindrical glass layer body 11g . 12g ,

Both the multilayer composite produced by means of the uniaxial and also by means of the hot isostatic pressing method 20 can be suitable for high vacuum and withstand temperatures up to 600 ° C. In the welded by diffusion bonding glass body 20 can capacitively coupled tax deposits 11m . 13m be embedded. A complete embedding of the pavement edges 22 the tax rates 11m . 13m can through border areas 24 be realized, which remain released from metallization and after the diffusion bonding or merging of the exposed edge areas 24 the pavement edges 22 enclosing high voltage resistant and vacuum tight.

A high-voltage insulator made of a glass-metal multilayer composite 20 With suitable dimensioning / design, the following advantages can be achieved: high vacuum-tightness, high thermal stability up to 600 ° C, high dielectric strength in the interior and controlled electric edge fields.

The use of diffusion welding to produce glass-to-metal joints brings many advantages. The high quality of the joining zone, the thermal stability, the mechanical strength and the vacuum resistance make the method very suitable for meeting high demands on workpieces for high-voltage insulation.

In particular, for use in the X-ray tubes results in the following further advantage due to the compact design. By internal tax fittings 11m . 13m can carry electrical resistance 20 be increased overall. As a result, significantly smaller diameters than in the case of known bushings can be realized for the implementation. In addition to a saving in installation space, a probability of discharge effects at boundary layers can be reduced as a result of a more uniform (preferably linear) potential reduction. Thus, the controlled implementation of a more reliable operation can be realized in a smaller space.

Crucial for the realization of these multi-layered networks 20 is the manufacturing process to metallic coverings 11m . 13m to assemble with glass. For their application as an insulator in the high voltage range, the quality of the joint, ie the homogeneity and the occurrence of bubbles, cracks and other material defects is decisive for the dielectric strength. For the production has proved to be advantageous, the metallized glass sheets 11g . 12g . 13g . 14g or rings 11g . 12g . 13g . 14g in a hot press process.

The multilayer composite 20 is prepared by a pressure p is applied at a corresponding temperature near the glass transition temperature Tg. The pressure p (compressive force per area) creates a forced contact of the adjacent surfaces. It comes to thermally activated surface diffusion and material interaction. In order to reduce the surface energy, the process of joining is energetically preferred. Germs form a fügeschicht that spreads via island growth. In the course of a corresponding residence time, a homogeneously bonded glass-metal composite is formed by a diffusion-controlled process 20 ,

It has been described above how diffusion bonding for the production of glass-metal multilayer composites can be used as a high-voltage insulator. One embodiment contemplates that diffusion bonding be applied in a hot press process to enhance diffusion through application of elevated temperatures and pressures. To produce glass-metal multilayer composites, highly insulating glass foils with a local surface metallization (metal foil 12m or directly applied metal layers 11m . 13m ) is added homogeneously and flush by applying pressure p at temperatures close to the glass transformation temperature Tg. The joining is not done primarily by viscous flow of the glass, but mainly by thermally intensified diffusion at the contact surfaces. The glasses used remain dimensionally stable. There is no macroscopic shrinkage or deformation. This technique makes it possible to realize homogeneously joined glass-metal composite layers.

A preferred embodiment provides that the arrangement, which is subjected to the pressure, comprises at least two glass layer body, on the surface of each of which a metal layer is applied. Control layers may be implemented in the form of a thin metallization of the glass layer bodies, the individual control layer having a layer thickness between, for example, 100 nm and 1 μm. The internal control fittings increase the overall electrical strength of the bushing. As a result, significantly smaller diameter can be realized. This is particularly advantageous for use in x-ray tubes. In addition to saving space, a reduction in the likelihood of discharge effects at the interface between the metal conductor and the insulating material (in this case, the glass) can be achieved due to a linear potential degradation. Thus, by means of a controlled implementation in a smaller space, a more reliable operation than with known high-voltage bushings can be realized.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Küchler, Hochspannungstechnik, ISBN 978-3-540-78412-8, page 100 [0002]
• Dahms, S. et al., Estonian Journ. Eng., 2009, 15, 2, 131-142: "Substance-to-substance-joining of quartz glass" [0003]

Claims (10)

Production method ( 100 ) for a multilayer composite ( 20 ), characterized in that the method ( 100 ) following steps ( 110 . 120 . 130 . 140 ) comprises: - providing ( 110 ) of a first glass layer body ( 11g ); - application ( 120 ) a first metal layer ( 11m ) on a surface ( 11s ) of the first glass layer body ( 11g ); - arrange ( 130 ) of a second glass layer body ( 12g ) on the at least partially metallized surface ( 11ms2 ) of the first glass layer body ( 11g ); and - supplying ( 140 ) of a pressure (p) on the arrangement of the mutually arranged glass layer body ( 11g . 12g ). Production method ( 100 ) according to claim 1, characterized in that the first ( 11g ) and / or the second ( 12g ) Glass layer body is a glass sheet. Production method ( 100 ) according to claim 1 or 2, characterized in that the first ( 11g ) and / or the second ( 12g ) Glass layer body is a glass tube. Production method ( 100 ) according to one of claims 1 to 3, characterized in that in step ( 140 ) applying the pressure (p) a uniaxial hot pressing takes place. Production method ( 100 ) according to one of claims 1 to 4, characterized in that in step ( 140 ) of pressurizing (p) hot isostatic pressing. Production method ( 100 ) according to one of claims 1 to 5, characterized in that the application ( 120 ) of the first metal layer ( 11m ) by screen printing, electroplating, sputtering, vapor deposition and / or in sol-gel technique. Production method ( 100 ) according to one of claims 1 to 6, characterized in that during application ( 120 ) of the first metal layer ( 11g ) the first metal layer ( 11g ) in a peripheral area ( 24 ) of the first glass layer body ( 11g ) is not applied so that in the edge region ( 24 ) a lining edge ( 22 ) of the first metal layer ( 11m ) after the implementation of the procedure ( 100 ) is completely embedded in glass. Production method ( 100 ) according to one of claims 1 to 7, characterized in that the charging ( 140 ) of the pressure (p) at a temperature near a transformation temperature (Tg) of the glass of the glass laminate body ( 11g . 12g ) is carried out. Production method ( 100 ) according to one of claims 1 to 8, characterized in that after step ( 140 ) of pressurizing (p) also a step ( 150 ) annealing near the transformation temperature (Tg) of the glass of the glass layer body ( 11g . 12g ) carried out. Component ( 20 ) for high-voltage insulation, characterized in that the component ( 20 ) comprises: - a first glass layer body ( 11g ); A second glass layer body ( 12g ); and - one between the first ( 11g ) and the second ( 12g ) Glass layer body arranged first metal layer ( 11m ), where a first page ( 11ms1 ) of the first metal layer ( 11m ) with the first glass layer body ( 11g ) is diffusion-welded and one from the first side ( 11ms1 ) facing away from the second page ( 11ms2 ) of the first metal layer ( 11m ) with the second glass layer body ( 12g ) is diffusion welded.

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