This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of European Patent Application No. 21178293.3, filed on Jun. 8, 2021.
The invention relates to an assembly comprising a metal member and a glass member bonded to the metal member in a glass-to-metal seal.
Glass-to-metal seals are known in the art. A glass-to-metal seal is formed by a metal member and a glass member which are bonded to each other, in particular, chemically bonded. Glass to-metal seals are used for different purposes. They are, just by way of example, used when a wire is led through a glass element, such as a light bulb, in order to connect an element in the interior of the glass element to the outside. Another example for a glass-to-metal seal is a glass member covering a metal member, e.g. a wire, which is covered partly by the glass member for protection. Furthermore, the glass member can be used to mechanically fixate the wire to an additional element.
If the bond between glass and metal is insufficient, the bond may suffer from mechanical or thermal stress and, in the worst case, break. Thermal stress for a glass-to-metal seal may be induced by temperature changes, in particular fast temperature changes or changes over a wide temperature range. Mechanical stress may be induced by vibrations, tensile forces or other.
An assembly includes a metal member containing a glass-forming component and a glass member bonded to the metal member in a glass-to-metal seal.
The invention will now be described by way of example with reference to the accompanying Figures, of which:
In the following, the invention and its improvements are described in greater detail, using exemplary embodiments and with reference to the drawings. The various features shown in the embodiments may be used independently of each other in specific applications. In the following figures, elements having the same function and/or the same structure will be referenced by the same reference signs.
The improvements described with respect to the assemblies and their advantages also relate to the method according to the invention. Likewise, the improvements and the advantages mentioned with respect to the method also apply to the assemblies according to the invention. In other words, the method according to the invention is used for producing assemblies according to the invention.
In the following, an embodiment of an assembly 1 is described with respect to
The assembly 1 comprises a metal member 3 and a glass member 5. The glass member 5 is bonded to the metal member 3 in a glass-to-metal seal 7. The glass to metal seal 7 is depicted as an interface region 9 and indicated by the dashed line in
The main constituent of the metal member 3 is a metal. The metal of the metal member 3 may be at least one of the following: nickel, silver, platinum, rhodium, iridium, palladium, aluminum, copper, gold, or an alloy containing any composition of the aforementioned materials. The main constituent of the glass member 5 is glass. By way of example, the glass member 5 may predominantly contain a silicate or a borosilicate.
The metal member 3 comprises glass-forming components 11. The glass-forming components 11 are indicated as circles in
The material of the glass member 5 and the glass-forming components 11 are chosen to fit to each other. Hence, a chemical bond between the glass member 5 and the glass-forming components 11 may, firstly, be easier to be achieved and may, secondly, form a particular stable bond between the glass member 5 and the metal member 3. If the glass member 5 predominantly contains a silicate, the glass-forming components 11 may contain silicon. Said silicon may get oxidized and form silicate which can easily bond to the silicate from the glass member 5.
A concentration of the glass-forming components 11 in the metal member 3 may be higher than 0.4%, or higher than 4%. In other words, the glass-forming components 11 are intentionally added to the material of the metal member 3 and are not only traces in the material of the metal member 3.
The aforementioned concentration of the glass-forming components 11 in the metal member 3 at least exists in near surface regions 13 of the metal member 3, in particular in the near-surface regions 13 of the metal member 3 that are part of the transition region 9, in which the metal member 3 and the glass member 5 are in contact with each other. Other regions do not necessarily need to be provided with a large amount of glass-forming components 11. In addition, other regions of the metal member 3 may also contain no glass-forming components.
By way of example,
Alternative distributions of the glass-forming components 11 in the metal member 3 are described in further detail below with respect to
Due to the glass-forming components 11 in the metal member 3, the metal member 3 contains glass 17 which may be present in the form of glass networks or glass matrices 19 in the material of the metal member 3, at least in its near-surface regions 13. The glass matrices 19 are indicated as rectangular structures in
The glass may be formed when the glass-forming components 11 react chemically with each other and/or with other elements. The glass matrices 19 may be formed from oxidized glass-forming components 11 in the metal member 3. Hence, the majority of the glass matrices 19 are present in the near-surface regions 13, where the glass forming components 11 may have easier contact with oxides from the ambient atmosphere.
The glass matrices 19 which extend to the surface 21 of the metal member 3 are in direct contact with the glass member 5. Hence, these matrices 19 may form chemical bonds with the material of the glass member 5. Thereby, a continuous glass structure 23 shown in
The strong bond between the glass member 5 and the metal member 3 may allow omitting the matching of the coefficients of thermal expansion (CTE) of the glass member 5 and the metal member 3. The CTE the glass member 5 may differ from the CTE of the metal member 3, for example by more than 10%. The bond between the glass member 5 and the metal member 3 is strong enough to keep the members 5 and 3 bonded even when temperature changes lead to different expansions of the members 5 and 3. Omitting the matching of the CTE eliminates the risk of contaminating the members 5 and 3 with elements that may reduce the function of the assembly and lead to failures.
Another benefit with regard to the coefficient of thermal expansion is that the at least one glass-forming component 11 in the metal member 3 may alter the response of the metal member 3 to temperature changes. If, for example, the metal member 3 is made from a ferromagnetic material, such as nickel, the material usually has an anomaly in the CTE around the Curie temperature (Curie point), at which the material loses its ferromagnetic properties. This anomaly leads to rapid changes in the expansion and may compromise the structural integrity of the bond between the metal member 3 and the glass member 5. However, the addition of the glass-forming component 11 may turn the material of the metal member 3 into a paramagnetic material even below the Curie point. Hence, the anomaly in CTE may be eliminated or at least reduced and does not constitute a risk to the structural integrity of the bond between the glass member 5 and the metal member 3.
The glass formed from oxidized glass-forming components 11 is typically electrically insulating. However, since an electrically conductive connection between the metal member 3 and the glass member 5 is not intended, this is not a drawback.
It is, just by way of example, known to use oxidized nickel for metal members that are to be covered with glass. However, nickel is not a glass-forming component as nickel oxide is not a glass. The oxidized nickel is sometimes used to improve the wettability of the metal member 3 before the glass member 5 is deposited there on. However, this is to be distinguished from the invention, in which glass-forming components 11 are used to form glass in the metal member 3 that is then chemically bonded to the glass member 5.
The glass member 5 may be formed by depositing glass melt 44 onto the metal member 3, as shown in
Instead of or additional to using the heat of the glass melt, the metal member 3 may be thermally treated or, in other words, heated before or during the deposition of the glass melt 44. Thereby, the oxidation rate of the glass-forming components 11 in the metal member may be increased.
When the glass melt 44 cools down, or, in other words, anneals, a solid glass member 5 is formed. Just by way of example, the glass melt 44 may be heated up to a temperature around 800° C. and may be deposited with a temperature between 700 and 800° C. The temperatures needed for the application of the glass member 5 will vary by their glass compositions and should not limit the example.
In another embodiment, a mixture of glass and/or ceramic powders is applied with an organic binder agent to provide a dispensable paste, which is applied on the metal member 3, evenly covering the electrically conductive connection member 31 and being transformed with temperature treatment into a glass member 5 or glass ceramic or a glass composite, which is later representing the glass member 5.
In a further embodiment, a preform of the glass material can be joined with the metal member 3, evenly covering the electrically conductive connection member 31 and being transformed with temperature treatment into a glass member 5 or glass ceramic or a glass composite, which is representing later the glass member 5.
In all mentioned options next to the glass member 5 and metal member 3, also a third material type, e.g. ceramics, can be incorporated to this seal.
In the following, an application of an assembly 1 according to the invention, in particular an assembly 1 of the aforementioned type, is described with respect to
The metal member 3 may be a lead wire 29, as shown in
By way of example, the connection member 31 is a contact pad 37 that serves to electrically connect a temperature dependent resistive element 39 with the lead wire 29. The temperature dependent resistive element 39 may be part of a platinum measuring structure 40 of the temperature sensor element 41. The contact pad 37 is formed as at least one conductive layer arranged on the element 39 to provide a conductive connection between the measuring structure 40 and the lead wire 29 and the material joint 35. The resistive element 39 is directly or indirectly connected to the connection member 31 in an electrically conductive manner.
A common substrate 43 shown in
As mentioned before, the metal member 3 is connected to the contact pad 37. The contact pad 37 is electrically and mechanically connected to the element 39.
In order to increase the structural integrity of the electrical device 27 and to further fixate the lead wire 29 thereto, the glass member 5 is provided and bonded to the lead wire 3. The glass member 5 covers the metallic member 3, represented by the lead wire 29, in a region that also comprises the interface region 33. Thereby, the material joint 35 between the lead wire 3 and the contact pad 37 is protected. Furthermore, the glass member 5 also covers the contact pad 37 and thereby protects the contact pad 37.
The glass member 5 may be in contact with the element 39 and the substrate 43. The glass member 5 thereby serves to fixate the lead wire 29 to the remaining electrical device 27. Due to the bond between the glass member 5 and the lead wire 29, which represents the metal member 3, the lead wire 29 is mechanically fixated by the glass member 5. Hence, a pullout force that needs to be overcome to remove the lead wire 29 from the electrical device 27 is increased, improving structural integrity. In addition, the glass member 5 may protect the lead wire 29 from the environment.
The cross-sectional shape of the lead wire 29 providing the metal member 3, shown further in
To form the glass member 5, glass melt 44 shown in
A method for building the glass member 5 is to apply a mixture of glass and/or ceramic powders with an organic binder agent to provide a dispensable paste, which is applied on the metal member 3, evenly covering the electrically conductive connection member 31 and being transformed with temperature treatment into a glass member 5, glass ceramic or a glass composite, which is later representing the glass member 5.
As mentioned above with respect to
The metal body 47 may be provided with a sheath or shell 49 that contains the glass-forming components 11. Just by way of example, the metal body 47 can be inserted into the sheath 49. By providing the metal body 47 with the sheath 49, the metal member 3 is formed.
In the alternative, the metal body 47 may be provided with a coating that contains the glass-forming components 11, in particular a dispersive coating. Said coating may then be regarded as the sheath 49 shown in
Number | Date | Country | Kind |
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21178293.3 | Jun 2021 | EP | regional |