DE102011080352B4 - High-temperature glass solder and its use - Google Patents

High-temperature glass solder and its use Download PDF

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DE102011080352B4
DE102011080352B4 DE102011080352.1A DE102011080352A DE102011080352B4 DE 102011080352 B4 DE102011080352 B4 DE 102011080352B4 DE 102011080352 A DE102011080352 A DE 102011080352A DE 102011080352 B4 DE102011080352 B4 DE 102011080352B4
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glass
glass solder
temperature
solder
oxide
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DE102011080352A1 (en
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Bastian Schön
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Schott AG
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Schott AG
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0222Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/0036Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C29/00Joining metals with the aid of glass
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00Glass compositions
    • C03C3/04Glass compositions containing silica
    • C03C3/062Glass compositions containing silica with less than 40% silica by weight
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • C03C8/24Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/02Details
    • H01M8/0271Sealing or supporting means around electrodes, matrices or membranes
    • H01M8/028Sealing means characterised by their material
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00Fuel cells; Manufacture thereof
    • H01M8/10Fuel cells with solid electrolytes
    • H01M8/12Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293Fuel cells with solid oxide electrolytes
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30Hydrogen technology
    • Y02E60/50Fuel cells

Abstract

Glass solder for high temperature applications, having a thermal expansion coefficient α (20-300) of 6 · 10-6 K-1 to 12 · 10-6 K-1 and a glass formation temperature Tg> 600 ° C, containing (in% by weight on an oxide basis ) Al2O3 13- <35 SiO2 0- <15 CaO 5-45 MgO 0-25 BaO 0- <25 SrO 0-20 ΣBaO + SrO <25 Cs2O 0-5 B2O3 0-15 RO 0-5 RO2 0-20 ΣAl2O3 + R2O3 13-55 ΣLi2O + Na2O + K2O0- <1, where RO is at least one alkaline earth oxide selected from the group ZnO and / or BeO, R2O3 is an oxide selected from the group Ga2O3 and / or In2O3 and / or Y2O3 and / or La2O3 and / or Dy2O3, and RO2 an oxide selected from the group TiO2 and / or ZrO2 and / or HfO2.

Description

  • The present invention relates to glass solders, in particular amorphous and at least partially crystallizing or completely crystallizing glass solders, which are particularly suitable for high temperature applications, have a high electrical insulation effect high resistance to chemical attack, and their applications.
  • Glass solders are usually used for the production of joint connections, in particular to connect glass and / or ceramic components with each other or with components made of metal in an electrically insulating manner. In the development of glass solders, their composition is often chosen so that the thermal expansion coefficient of the glass solder corresponds approximately to that of the components to be joined together in order to obtain a permanently stable joint. Compared to other joining compounds, for example those made of plastic, such based on glass solders have the advantage that they are hermetically sealed and can withstand higher temperatures.
  • Glass solders are generally often made from a glass powder, which is melted during the soldering process and results in the heat transfer with the components to be joined the joint. The soldering temperature is usually chosen approximately equal to the so-called hemispherical temperature of the glass or can usually differ by ± 20 K from this. The hemisphere temperature can be determined in a microscopic procedure with a hot stage microscope. It indicates the temperature at which an originally cylindrical specimen has been melted together to form a hemispherical mass. The hemisphere temperature can be assigned a viscosity of about log η = 4.6, as appropriate literature can be found. If a crystallization-free glass in the form of a glass powder is melted and cooled again so that it solidifies, it can usually also be remelted at the same melting temperature. For a joint connection with a crystallization-free glass solder, this means that the operating temperature to which the joint connection can be permanently exposed must not be higher than the soldering temperature. In fact, in many applications, the operating temperature must still be significantly lower than the soldering temperature, since the viscosity of the glass solder decreases with increasing temperatures and a glass which can flow to some extent can be forced out of the joint at high temperatures and / or pressures, so that it can fail its service. For this reason, glass solders for high-temperature applications usually have a soldering temperature or hemispherical temperature which is still significantly above the later operating temperature.
  • A field of application of such glass solders are z. B. joining compounds in high-temperature fuel cells, which z. B. can be used as energy source in motor vehicles or for decentralized energy supply. An important type of fuel cell, for example, the so-called SOFC (solid oxide fuel cell), which can have very high operating temperatures of up to about 1100 ° C. The joint connection with the glass solder is usually used for the production of fuel cell stacks, d. H. used for the connection of several individual fuel cells to a stack. Such fuel cells are already known and are being continuously improved. In particular, the trend in current fuel cell development is generally to lower operating temperatures. Some fuel cells already reach operating temperatures below 800 ° C, so that a lowering of the soldering temperatures possible and due to the then low temperature load of the SOFC components in the soldering process is also desirable.
  • A major role in fuel cell development comes in the glass solders, which are already the subject of the following disclosures.
  • The DE 19857057 C1 describes an alkali-free glass-ceramic solder with a thermal expansion coefficient α (20-950) of 10.0 · 10 -6 K -1 to 12.4 · 10 -6 K -1 . The solder described there contains 40 to 50 mol% SiO 2 . However, an increasing content of SiO 2 leads to an increase in the melting temperature and thus also in the soldering temperature, which makes the processing of such a glass more difficult.
  • In the US 6 124 224 A alkali metal-free glass solders are proposed which contain 18 to 60 wt .-% SiO 2 . This amount of SiO 2 is required to obtain sufficient chemical resistance. The thermal expansion coefficients α (20-300) achieved are 4.8 × 10 -6 K -1 to 7.4 × 10 -6 K -1 , which is why the production of joining compounds of high-expansion steels with these glasses is hardly possible.
  • The DE 10 2005 002 435 A1 includes composite solders consisting of an amorphous glass matrix and a crystalline phase. The glass matrix has contents of SiO 2 of 27 to 28 wt .-%. No information is given about the physical properties of the glasses.
  • Subject of the US 2006/0172875 A1 are SOFCs that are bonded to glass frits that exhibit a thermal expansion α (20-300) of 10.0 · 10 -6 K -1 to 12.0 · 10 -6 K -1 . The glasses described have proportions of SiO 2 of 24 to 50 wt .-% and proportions of Al 2 O 3 from 4 to 6 wt .-%.
  • In the US 6,362,119 B1 Glass and glass ceramics are proposed for the isolation of electronic components, which have a high content of BaO of 25 to 75 wt .-%. Such high barium contents can lead to the formation of unwanted barium chromate phases, in particular when joining chromium-containing materials, for example chromium-containing steels which are often used in SOFC stacks, which weaken the joint connection and can therefore lead to damage of the component.
  • High levels of BaO and SiO 2 are also found in the DE 600 25 364 T2 proposed, which has a glass-ceramic connection material to the object. This material is intended for joining ceramic joining partners.
  • From the WO 2010/099939 A1 Again, a crystallizable glass solder for high temperature applications is known, which also contains 25 to 40 wt .-% SiO 2 .
  • The US 4,326,038 describes a sealing material which provides levels of Al 2 O 3 of at least 35% by weight. The same minimum salary will be paid by the DE 3012322 A1 proposed. The US 1 173 386 A provides a minimum content of Al 2 O 3 of 41.4 wt .-% before. Common to all these writings is that the object of the material is the closure of lamps. The invention has for its object to provide an amorphous or at least partially crystalline and / or completely crystallizing solder glass available for permanent use temperatures of more than 900 ° C and the joining of high-tensile materials such as oxide ceramics (esp. Al 2 O 3 - and or ZrO 2 based ceramics) and / or high-tensile alloys and / or steels and therefore has a thermal expansion coefficient α (20-300) in the range of 6 · 10 -6 K -1 to 12 · 10 -6 K -1 , Furthermore, the solder glass should have a very good resistance to the chemical attack of acids, alkalis and / or water to allow a long life of the components produced with the solder glass.
  • The object is achieved by the glass solders according to the independent claims. Preferred embodiments will be apparent from the dependent claims.
  • All other percentages mentioned are, unless stated otherwise, in% by weight based on oxide.
  • The glass solders according to the invention have a linear thermal expansion coefficient α (20-300) of 6 · 10 -6 K -1 to 12 · 10 -6 K -1 and a glass formation temperature T g of more than 600 ° C. For this reason, they can be soldered in the glassy state at temperatures of less than 1000 ° C. In embodiments of the glass solders according to the invention, there is the option of converting them into a glass ceramic by means of a partial or at least almost complete ceramization connected to the soldering process at the crystallization temperature. This has a relation to the amorphous state increased melting temperature, so that the thus treated glass solders can be used in this way permanently at temperatures of more than 1000 ° C.
  • The gas solder according to the invention contains 13% to less than 35% Al 2 O 3 . The content of Al 2 O 3 is decisive for achieving the required high value of T g . Furthermore, it contributes to the fact that the glass solder is very resistant to chemical attack. In addition, according to the invention, the crystallization behavior of the glass solder is controlled via the Al 2 O 3 content. With Al 2 O 3 contents of more than 50% and in particular 55%, the crystallization tendency increases sharply and it is increasingly possible to deposit phases which contain Al 2 O 3 . On the other hand, if too little Al 2 O 3 is present in the glass solder in the simultaneous presence of BaO, in turn, more BaO-containing phases can deposit. Both Al 2 O 3 and BaO-containing phases are undesirable because these phases can weaken the bond between the glass solder and the components of the component to be joined thereto. At contents of less than 13% Al 2 O 3 could be observed that the crystallization tendency is also increased again in an undesirable manner.
  • According to the invention, the glass solder includes optional and less than 15% SiO 2 . This includes glass solders that do not contain SiO 2 . SiO 2 is considered as a network former, which contributes to improving the meltability. As already mentioned in the discussion of the prior art, it was previously also the opinion that higher contents than 15% of SiO 2 are necessary in order to achieve a good chemical resistance. The inventors have realized that this is not necessary with the present glass composition. The low shares of SiO 2 now make it possible to achieve the stated thermal expansion values. As the proportion of SiO 2 increases, the thermal expansion coefficient of the glass solder is reduced. Also, at higher levels of SiO 2, quartz crystals can form in their various modifications, which cause large volume changes at the individual phase transitions and thus lead to strong stresses in the joint formed with the glass solder.
  • Another necessary component in the glass solder according to the invention is CaO, which is contained at 5% to 45%. According to the invention, CaO contributes to the increase in the thermal expansion and control of the crystallization. At levels above 45%, the tendency to crystallize would increase greatly. At contents of less than 5% in conjunction with the inventively low BaO contents, the thermal expansion would decrease to values of α (20-300) smaller than 6 · 10 -6 K -1 . Also, if the contents are too low in the downstream crystallization, insufficient formation of the crystal phase may occur, as a result of which the glass ceramic obtained would no longer be stable at high temperatures.
  • To control the crystallization is provided as an optional component MgO. MgO may be included from 0% to 25% in the glass solder of the present invention. Apart from that, it serves to increase the thermal expansion similar to CaO. Higher contents than 25%, however, can lead to unwanted crystallization already during the melting process, which would adversely affect the wetting and the flow behavior of the glass solder when it is used in component production.
  • Another optional component is BaO at a level of 0% to less than 25%. Also BaO is used in the glass according to the invention for adjusting the thermal expansion. The value of α (20-300) increases with the proportion of BaO. Higher contents than those stated may, however, lead to increased crystallization. In this case too, barium chromium phases, which weaken the compound and are therefore undesirable, can form during the joining of chromium-containing materials. High BaO-containing glasses have a lower glass formation temperature in comparison. The tendency to crystallize in high BaO-containing glasses glasses which are also low in alkali metals and have a low content of SiO 2 high, which is why these can already occur during the melting process undesirably strong crystallization.
  • Optionally, SrO is also included in the glass solder according to the invention, namely from 0% to at most 20%. As the content of SrO increases, so does the value of α (20-300) . At levels higher than those stated, the tendency to crystallize may undesirably increase and the joining temperatures may shift towards higher values, which in turn may make it difficult to produce joining components.
  • However, the proportions of BaO and SrO are chosen so that the sum of BaO and SrO is less than 25%. It has been found that at higher levels of these two components, the crystallization tendency of the glass solder during the soldering process can increase undesirably.
  • In the case of a glass solder according to the invention, optionally at least one further alkaline earth oxide RO selected from the group ZnO and / or BeO up to 5% is also contained.
  • The crystallization properties of the glass solder can also be controlled by the content of the further alkaline earth oxides RO. Another positive effect is that the dielectric loss can be reduced by glasses containing RO. Furthermore, the melting temperatures and the glass transition temperature can be reduced by the network-converting alkaline earth oxides. The content of RO also causes an increase in the coefficient of thermal expansion and thus provides a simple way to adapt the glass solder to the components to be fused.
  • Another optional component in the glass solder according to the invention is Cs 2 O with a content of 0% to 5%. However, less than 5% are preferred. By adding Cs 2 O, the melting temperatures can be lowered. At contents of more than 5%, the thermal stability and the electrical insulation effect decrease sharply. Also, a high content can lead to increased crystallization.
  • Also optionally contained in the glass according to the invention is B 2 O 3 with a content of 0% to 15%. This component acts as a network builder. Its presence increases the meltability of the glass and reduces the melting temperature. Furthermore, the contents of B 2 O 3 contribute to reducing the segregation tendency of the glass solder. The presence of B 2 O 3 improves the chemical resistance of the glass solder. At higher levels of B 2 O 3 than those indicated, the chemical resistance decreases as well electrical isolation ability but again. This is the case in particular for low-alkali glasses, since B 2 O 3 has no alkalines for charge balance for the coordination change into the tetrahedral structure as a result of the boric acid anomaly. Also, at higher levels due to crystallization residual glass phases can form with an increased proportion of boron. Such residual glass phases can adversely affect the physical properties. Likewise, such residual glass phases can react with the connection partners and thus weaken the joint connection. Further, as optional components, further oxides R 2 O 3 are selected from the group Ga 2 O 3 and / or In 2 O 3 and / or Y 2 O 3 and / or La 2 O 3 and / or Dy 2 O 3 in the glass solder according to the invention. For their content is that they are included in total together with Al 2 O 3 from 13% to 55% in the glass solder according to the invention. These additional oxides R 2 O 3 are also able to control the crystallization behavior of the glass solder during the soldering process. At the same time they can increase the glass formation temperature. The higher the glass formation temperature T g , the higher the application temperature of the glass solder. Likewise, they can help to improve chemical resistance.
  • Further optional components are the oxides RO 2 selected from the group TiO 2 and / or ZrO 2 and / or HfO 2 with a content of 0% to 20%. In particular, these oxides can act as nucleating agents for the partial crystallization and / or complete crystallization desired in certain embodiments. In addition, they can improve the strength of a joint connection with the glass solder according to the invention.
  • The required according to the task very good resistance to chemical attack reaches the glass solder according to the invention in addition to the contents of said components in the amounts also mentioned by its at most very low proportion of the alkali metals Li 2 O and / or Na 2 O and / or K 2 O, which in total are less than 1% in total.
  • In a preferred embodiment, the glass solder according to the invention consists of the abovementioned components with the stated proportions.
  • In a further preferred embodiment, the glass solder according to the invention is free of Li 2 O and / or Na 2 O and / or K 2 O except for at most unavoidable impurities.
  • The non-existent or at most only very small proportion of Li 2 O and / or Na 2 O and / or K 2 O in the glass solder according to the invention not only leads to the glass solder having a very good chemical resistance, but also very good electrical insulation properties to own.
  • In a further preferred embodiment, the glass solder according to the invention is also free of Cs 2 O (except for at most impurities). This embodiment is particularly resistant to chemical attack.
  • Likewise preferably, the glass solder according to the invention is also free (except for impurities) of Rb 2 O and Fr 2 O. Preferably, the glass solder according to the invention (except impurities) is free of TeO 2 , inter alia because the raw material is considered hazardous to health for the human body , This means that TeO 2 is preferably present at less than 0.3% by weight and more preferably at less than 0.2% by weight in the glass solder according to the invention.
  • Other additives are of course possible and also covered by the invention. For the purposes of the invention, the term glass solder includes both the amorphous base glass, which is used as solder glass before the soldering process, and the material resulting from the base glass during the soldering process, which may preferably be amorphous and / or at least partially crystallized. In the amorphous one speaks of a glassy state, at least partially crystalline of a glass-ceramic. Accordingly, the glass solder according to the invention may be a glass and / or a glass ceramic.
  • In a preferred embodiment, a glass solder according to the invention contains 13% to 29% Al 2 O 3 , 0% to 13% SiO 2 , 0% to 11% B 2 O 3 , 0% to 6% MgO, 5% to 24% CaO, 0% to less than 21% BaO and 0% to less than 10% SrO.
  • Furthermore, by raw materials or by refining agents such as As 2 O 3 and / or BaCl caused impurities of up to 0.2% may be contained in the glass solder according to the invention.
  • The glass solder according to the invention is preferably present after the soldering process as an amorphous glass. This means that it has essentially no crystalline regions.
  • In an alternative preferred embodiment, however, the glass solder according to the invention is in an at least partially crystalline state (including a completely crystallized state). This can be achieved by subsequent temperature treatment of the amorphous glass solder. The glass solder according to the invention is thus crystallizable. In the partially crystalline state, which also refers to a glass ceramic, the crystalline fraction is preferably at most 50%, based on the total weight.
  • In the glass solder according to the invention, the ratio of Al 2 O 3 , CaO and MgO is preferably chosen such that it is located on a low-melting eutectic in which the crystal phase Ca 3 Al 4 MgO 10 precipitates. As a result, glasses with a low melting temperature of less than 1000 ° C can be realized, which can be partially or completely crystallized after the joining process. The crystal phases formed are still thermally stable up to temperatures of 1000 ° C and more, which allows a high permanent use temperature of the compounds thus prepared. Preferably, however, no trydimite is formed during the crystallization, which can be achieved by the corresponding content of CaO.
  • In the partially crystalline and / or crystalline embodiment, the composition of the glass solder according to the invention is preferably adjusted so that it crystallizes slowly. If it already crystallized very strongly during soldering, adequate wetting of the components to be joined is often not given. In particular, the solder glass is to be introduced during the manufacture of a joint in general in non-crystallized or partially crystallized form in the joint to be soldered, since the temperature required for the wetting of the components to be fused is then lower.
  • The glass solder according to the invention preferably has a hemispherical temperature of 820 ° C to 1100 ° C, and can be used according to about this temperature for the joint compound. Due to this possible temperature range, the glass solder is also suitable for processing in laser joining processes.
  • The glass solder according to the invention is generally prepared by melting the ingredients into a glass in a conventional molten glass and then grinding this into a glass powder. The glass powder can, for. B. in the form of a dispensible paste or a pre-sintered molded body are introduced into the joint connection.
  • Optimum strengths of a joint connection are achieved if the glass solder in the thermal expansion is optimally adapted to the materials to be fused. Furthermore, even a change in the thermal expansion coefficient due to the crystallization process should not result in excessive stresses in the solder. The glass solder according to the invention ensures this, inter alia, by avoiding unwanted crystal phases.
  • Due to its physical properties, the glass solder according to the invention is particularly suitable for the production of high-temperature-resistant joint compounds. High-temperature-resistant in the sense of the invention means a temperature range of more than about 650 ° C. They have a glass formation temperature T g of more than 600 ° C and can be soldered in the glassy state at temperatures <1000 ° C. By a partial or complete ceramization connected to the soldering process at the crystallization temperature, the ceramic or glass ceramic thus obtained can be used permanently at temperatures> 1000 ° C.
  • Such joining compounds can be used particularly advantageously in fuel cells, in particular SOFC (Solid Oxide Fuel Cell). An example of an application in fuel cells is to connect individual SOFCs to a SOFC stack. Further fields of application are sensors in combustion units, for example automotive applications, marine engines, power plants, aircraft or in space technology. A preferred application is the use of the inventive glass solder and sensors in the exhaust system of motor vehicles with internal combustion engines.
  • However, the glass solder according to the invention can also be used for the production of sintered bodies with high temperature resistance. Production methods of sintered bodies are well known. In general, while the starting material of the glass solder according to the invention in powder form is mixed together, mixed with a generally organic binder and pressed into the desired shape. Instead of the powders of the starting materials, an already molten glass according to the invention can also be ground and mixed with the binder. The pressed glass-binder body is then brought to sintering temperature whereby the binder can burn out and sinter the glass components together at the sintering temperature. The sintered body thus obtained may then be in contact with the Components are brought and connected by a soldering this and / or connected to these.
  • The use of sintered bodies during soldering has the advantage that the sintered body is a shaped component and can be brought into almost any desired geometries. An example frequently used form is a hollow cylinder, which can be introduced together with an electrical contact pin in lead-through openings of metal components in order to obtain by soldering a preferably hermetically sealed glass-metal leadthrough with an electrically insulated contact pin. Such glass-metal bushings are used in many electrical components and are known in the art.
  • A further preferred application of the glass solder according to the invention is the production of films which include the glass solder. Such films are similar to the sintered body described above, but can be made largely flexible. From them shapes can be punched out and used in an advantageous manner to connect flat components together.
  • The invention will be described in more detail below with reference to the properties of glass solders according to the invention as well as comparative examples.
  • First, the solder glass was melted in a molten glass. The following properties were measured on the solder glass, which is usually in block glass, at least in solid form.
  • The composition of an exemplary solder glass according to the invention and its physical properties are summarized in the table.
  • It means:
  • α (20-300)
    linear thermal expansion coefficient from 20 ° C to 300 ° C
    T g
    Glass transition temperature, or short transition temperature
  • After the characterization of the solder glass, the powder glass solder is generally produced from the solder glass by a grinding process. In the present examples, a powder having a particle size distribution with a D (50) of approx. 10 μm and a D (99) <63 μm was prepared from the molten solder glasses and processed to a dispensable paste with a binder. Powder and binder were homogenized with a three-roll mill. The binder is generally organic substances such. B.
  • Nitrocellulose, ethylcellulose or acrylate binder. It generally has no further influence on the properties of the crystallized glass solder, but should be selected so that it can be completely burned out during the heating process. Composition in% by weight SiO 2 12.2 Al 2 O 3 24.7 B 2 O 3 10 MgO 4.9 CaO 20.4 BaO 20.8 SrO 7 Physical readings amorphous crystallized sintered beginning 739 1086 softening 865 1092 spherically temperature 890 1105 Hemisphere temperature 938 1132 flow temperature 970 1174 α (20-300) 10 -6 K -1 8.53 8.81 T g [° C] 658 918 Dilatometric softening point [° C] 718 1024 Crystallization temperature [° C] 800 -
  • Subsequently, the thermal characterization of the glass solders by means of a Heiztischmikroskopes. From the solder glass to be characterized in powder form, a cylindrical specimen is pressed, which is heated on a ceramic base plate at 10 K / min. The changes in shape of the specimen are observed, with the temperature increasing for a non-crystallizing sample usually giving the following characteristic points, to which certain viscosities can be assigned:
    Start of sintering: also called sintering temperature. At this temperature, the grains of powder begin to fuse. As a result, the height of the sample body decreases. The logarithm of the viscosity is about 10 +/- 0.3.
  • Softening temperature: This temperature EW is characterized by an incipient rounding of the edges of the sample cylinder. The logarithm of the viscosity is about 8.2.
  • Dilatometric softening point: This is measured with a dilatometer and is the temperature at which the sample no longer expands but begins to shrink. The temperature of the dilatometric softening point is similar to the sintering temperature.
  • Spherical Temperature: The logarithm of viscosity is about 6.1.
  • Hemisphere temperature: The specimen has approximately the shape of a hemisphere at this temperature. The logarithm of viscosity is about 4.6 +/- 0.1.
  • Flow temperature: At this temperature, the height of the specimen is about 1/3 of the initial height. The logarithm of the viscosity is about 4.1 +/- 0.1.
  • Crystallization temperature T C : Peak crystallization temperature determined by differential thermal analysis (DTA), exothermic reaction
  • These tests were conducted for the exemplary glass in the amorphous state and in a partially crystallized state in which the glass-ceramic had an amorphous content of at least 10% and a crystal phase content of at least 90% by total weight.
  • This hemispherical temperature of the amorphous glass differs significantly from that of the partially crystallized. In the present example, it was before crystallization, ie in the amorphous state, at 938 ° C. After crystallization, also called ceramification, the hemisphere temperature was much higher, namely at 1132 ° C. The hemisphere temperature is also often referred to as the sealing temperature. Ie. it is the temperature at which a joint can be made using the glass solder. The location of the hemispherical temperature of the glass solder according to the invention makes them particularly suitable for laser joining processes, since at larger process temperatures the ceramic to be joined and / or sealed with the glass solder will couple under the laser due to the change of optical properties (increase the absorption coefficient) and thus become one unwanted jump in temperature can occur.
  • When using laser radiation for joining the joint assembly is usually heated very quickly, with crystallization is largely suppressed. Within a few seconds to minutes, a stable joining compound can be obtained. Positive joining experiments were carried out with a diode laser (power 3 kW) and emission wavelengths of 808 nm and 940 nm. The starting glasses are stirred into a suspension as a powder and brushed onto the joining compound and then irradiated with the laser. It has been found that the glalones according to the invention are very well suited for laser joining processes.
  • The glass solders according to the invention combine all the positive properties according to the object of the invention. The solder glass as a precursor can be with conventional fusion with good Melting and not too high melting temperatures produce. The crystallization behavior of the glass solder according to the invention is within the specified composition and by the choice of suitable process parameters, in particular the temperature control during heating and cooling, within wide ranges adjustable. Therefore, the glass solder according to the invention can be used for a variety of applications.
  • The glass solder according to the invention has a thermal expansion coefficient of at least 6 ppm / K, a glass formation temperature T g of more than 600 ° C and can be soldered in the glassy state at temperatures of less than 1000 ° C. By a connected to the soldering process, partial or complete crystallization at the crystallization temperature, the ceramic and / or glass ceramic thus obtained can be used permanently at temperatures of 1000 ° C and more.
  • A glass solder according to the invention can be used for the production of a gas-tight, high-temperature stable, electrically insulating compound of materials with a thermal expansion of 6 · 10 -6 K -1 to 12 · 10 -6 K -1 . Such materials are, for example, high-tensile steels, high chromium alloys and oxide ceramics, in particular ZrO 2 .
  • In particular, joining compounds of ZrO 2 with ZrO 2 and ZrO 2 and other materials with high thermal expansion, high-expansion alloys such as CFY, Durcolloy, Inconel or Crofer22APU can be realized.
  • In high temperature stable glasses of the prior art, which are adapted by means of a high-expansion crystalline filler such as wollastonite or barium silicates in their thermal expansion, the inert filler can hinder the flow of the glass. In the realization of thin joint gaps, this filler can prevent a uniform distribution of the glass. A further disadvantage of using fillers to match the thermal expansion of solder glasses is that micro-stresses can occur during rapid temperature changes as a result of the different thermal expansion of the filler and the surrounding glass matrix, which in the worst case can lead to failure of the joint connection.
  • In contrast, the invention provides high-expansion amorphous and / or at least partially crystallizing glasses, which by themselves have a thermal expansion with a thermal expansion coefficient of 6 · 10 -6 K -1 to 12 · 10 -6 K -1 and therefore can dispense with the disadvantageous filler. In this way, the manufacturability of joint connections and their reliability is significantly improved with the glass solder according to the invention.
  • Due to the composition of the glass solder according to the invention, the formation of undesired crystal phases is effectively prevented, which permanently enables low-stress joint connections.
  • The glass solder according to the invention has at most very small proportions of the alkali metals lithium, sodium and / or potassium (or their oxides) and are preferably free of these. Lithium, sodium and / or potassium (or their oxides) containing glass solders have a worse electrical insulation effect. Also, the chemical resistance decreases with increasing alkali content. Larger proportions of lithium, sodium and / or potassium (or their oxides) containing glasses usually have a lower glass formation temperature, which facilitates the melting and processing operation. The inventors have recognized that crystallizing glass compositions, however, can form an alkali-rich residual glass phase which can weaken the load-bearing capacity and the chemical resistance of the joint compound. When used in a corrosive environment, this residual glass phase can dissolve, which consequently leads regularly to the failure of the joint. A lithium, potassium and / or sodium (or their oxides) rich residual glass phase can continue to act highly corrosive at high temperatures, react with the connection partners of the joint compound and adversely affect their physical properties or dissolve in the worst case. A lithium, potassium and / or sodium (or their oxides) rich residual glass phase can also drastically reduce the electrical insulation effect, especially at high application temperatures.
  • The glass solders of the invention have a very good resistance to chemical attack of water and / or alkalis. In particular, the glass solder according to the invention corresponds to a water resistance class HGB1 according to ISO 719 and an alkali resistance class of A2 or better according to ISO 695.
  • The inventors have succeeded in achieving the high resistance of the glass solder according to the invention to water and alkalis without having to contain high proportions of SiO 2 in the glass solder. According to the invention, the proportion of SiO 2 is less than 15%. As the SiO 2 content increases, the thermal expansion can drop to lower values. On the other hand, high SiO 2 contents can lead to increased and difficult-to-control crystallization. A high proportion of SiO 2 . may result in excretion of cristobalite or tridymite crystals, depending on the temperature. Beta tridymite changes to beta quartz at about 870 ° C and then to alpha quartz at the so-called quartz jump at 573 ° C in the low-temperature modification. These phase transformations are reversible and associated with large volume changes. This change in volume causes very high stresses in the material, which can greatly weaken the joint connection or even lead to its complete failure. In addition, high SiO 2 contents can adversely affect the wetting properties on basic oxides such as ZrO 2 , which is disadvantageous in the production of joint compounds with the ZrO 2 ceramics which are often used for SOFCs.
  • Another contribution to the very good resistance to chemical attack and the excellent electrical insulation properties. even at high temperatures, the at most very low content of Li 2 O and / or Na 2 O and / or K 2 O.

Claims (10)

  1. Glass solder for high-temperature applications , having a thermal expansion coefficient α (20-300) of 6 · 10 -6 K -1 to 12 · 10 -6 K -1 and a glass formation temperature T g > 600 ° C, containing (in% by weight oxide) Al 2 O 3 13- <35 SiO 2 0- <15 CaO 5-45 MgO 0-25 BaO 0- <25 SrO 0-20 ΣBaO + SrO <25 Cs 2 O 0-5 B 2 O 3 0-15 RO 0-5 RO 2 0-20 ΣAl 2 O 3 + R 2 O 3 13-55 ΣLi 2 O + Na 2 O + K 2 O 0- <1,
    where RO is at least one alkaline earth oxide selected from the group ZnO and / or BeO, R 2 O 3 is an oxide selected from the group Ga 2 O 3 and / or In 2 O 3 and / or Y 2 O 3 and / or La 2 O 3 and / or Dy 2 O 3 , and RO 2 is an oxide selected from the group TiO 2 and / or ZrO 2 and / or HfO 2 .
  2. Glass solder according to claim 1, which is free of Li 2 O and / or Na 2 O and / or K 2 O.
  3. Glass solder according to at least one of the preceding claims, containing (in% by weight based on oxide) Al 2 O 3 13-29 SiO 2 0-13 B 2 O 3 0-11 MgO 0-6 CaO 5-24 BaO 0- <21 SrO 0- <10
  4. Glass solder according to at least one of the preceding claims, wherein the glass solder is present as an amorphous glass after the soldering process.
  5. Glass solder according to at least one of claims 1 to 3, wherein the glass solder after the soldering process in an amorphous or in an at least partially crystallized state.
  6. Glass solder according to claim 5, wherein the crystalline phase contains Ca 3 Al 4 MgO 10 and preferably no tridymite.
  7. Glass solder according to at least one of the preceding claims with a hemispherical temperature of 820 ° C to 1200 ° C.
  8. Use of a glass solder according to at least one of the preceding claims for the production of joint connections, in particular for fuel cells and / or exhaust gas sensors and / or spark plugs.
  9. Use of a glass solder according to at least one of claims 1 to 7 for the production of sintered bodies and / or films with high temperature resistance.
  10. Use of a glass solder according to at least one of Claims 1 to 7 for joining high-tensile steels and / or steels containing high chromium content and / or alloys containing high chromium content and / or Al 2 O 3 and / or ZrO 2 ceramics.
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FR3002531B1 (en) * 2013-02-26 2015-04-03 Electricite De France Process for the synthesis of a sealing glass by sol-gel path
DE102013209970B3 (en) 2013-05-28 2014-07-24 Schott Ag Glassy or at least partially crystalline joining material and its use and jointing
EP3650415A1 (en) 2018-11-07 2020-05-13 Schott Ag Joint connection comprising a crystallised glass, its use, crystallisable and at least partially crystallised glass and its use
DE102018127748A1 (en) 2018-11-07 2020-05-07 Schott Ag Joining compound comprising a crystallized glass, its use and crystallizable and at least partially crystallized glass and its use

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DE3012322A1 (en) * 1979-04-02 1980-10-09 Gen Electric Object with a sealant with calcium oxide, barium oxide and aluminum oxide
US4326038A (en) * 1977-06-29 1982-04-20 Ngk Insulators, Ltd. Sealing composition and sealing method
DE19857057C1 (en) * 1998-12-10 2000-04-13 Fraunhofer Ges Forschung Use of an alkali-free silicon, magnesium and heavy alkaline earth metal oxide mixture as a high thermal expansion coefficient glass-ceramic joint material, especially for high temperature fuel cells
US6124224A (en) * 1998-09-02 2000-09-26 Ferro Corporation High temperature sealing glass
US6362119B1 (en) * 1999-06-09 2002-03-26 Asahi Glass Company, Limited Barium borosilicate glass and glass ceramic composition
DE102005002435A1 (en) * 2005-01-19 2006-07-27 Forschungszentrum Jülich GmbH Composite material for producing high temperature joint connections, e.g. in fuel cells, comprising amorphous glass matrix and crystalline phase of precrystallized glass and/or ceramic powder
DE60025364T2 (en) * 1999-07-30 2006-08-03 Battelle Memorial Institute, Richland Ceramic compound material and compound process
US20060172875A1 (en) * 2005-02-03 2006-08-03 Cortright Jeffrey E Low alkali sealing frits, and seals and devices utilizing such frits
WO2010099939A1 (en) * 2009-03-04 2010-09-10 Schott Ag Crystallizing glass solder and use thereof

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GB1173386A (en) * 1966-06-30 1969-12-10 Westinghouse Electric Corp Sealing Compositions for Sealing Ceramics to Ceramics or to Refractory Metals
US4326038A (en) * 1977-06-29 1982-04-20 Ngk Insulators, Ltd. Sealing composition and sealing method
DE3012322A1 (en) * 1979-04-02 1980-10-09 Gen Electric Object with a sealant with calcium oxide, barium oxide and aluminum oxide
US6124224A (en) * 1998-09-02 2000-09-26 Ferro Corporation High temperature sealing glass
DE19857057C1 (en) * 1998-12-10 2000-04-13 Fraunhofer Ges Forschung Use of an alkali-free silicon, magnesium and heavy alkaline earth metal oxide mixture as a high thermal expansion coefficient glass-ceramic joint material, especially for high temperature fuel cells
US6362119B1 (en) * 1999-06-09 2002-03-26 Asahi Glass Company, Limited Barium borosilicate glass and glass ceramic composition
DE60025364T2 (en) * 1999-07-30 2006-08-03 Battelle Memorial Institute, Richland Ceramic compound material and compound process
DE102005002435A1 (en) * 2005-01-19 2006-07-27 Forschungszentrum Jülich GmbH Composite material for producing high temperature joint connections, e.g. in fuel cells, comprising amorphous glass matrix and crystalline phase of precrystallized glass and/or ceramic powder
US20060172875A1 (en) * 2005-02-03 2006-08-03 Cortright Jeffrey E Low alkali sealing frits, and seals and devices utilizing such frits
WO2010099939A1 (en) * 2009-03-04 2010-09-10 Schott Ag Crystallizing glass solder and use thereof

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