CH720703A1 - glass feedthrough - Google Patents

Abstract

The invention relates to a glass feedthrough (11) with at least one contact pin (13), wherein the contact pin (13) has a core and the core comprises a metal or a metallic alloy. The core is surrounded by a protective layer. The protective layer comprises an alloy of nickel or cobalt and a noble metal. The invention also relates to a method for producing a glass feedthrough (11).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a glass feedthrough with at least one contact pin according to claim 1 and a method for producing a glass feedthrough according to claim 13.

BACKGROUND OF THE INVENTION

[0002] Glass feedthroughs have contact pins made of a metal, usually an iron-nickel alloy. The susceptibility to corrosion is counteracted by applying a layer to the contact pins, i.e. the contact pins are refined with a gold layer. In addition, due to this refinement, the contact pin is easy to solder, bond and plug in with low contact resistance. It is known from the prior art that a gold layer or a layer of another precious metal can be applied. The application of a gold layer can only take place after a melting process, since diffusion occurs during the heat treatment when the gold layer is applied and the gold tends to segregate. The subsequent refinement process is very costly, since the contact pins must be contacted individually and selectively coated in the frame electroplating process. Contacting the contact pins with wire also leads to the creation of areas with a less good coating, which form points of attack for corrosion. In addition, uncoated areas can form at the transition between the glass and the gold layer, where increased corrosion can occur.

[0003] US 6,274,252 B1 discloses, among other things, a glass feedthrough which has contact pins made of an iron-nickel alloy. A corrosion-resistant layer, for example made of precious metals, is provided for the outer surfaces of the contact pins. In a specific embodiment, the contact pin has a precious metal layer with a thickness of 50 to 300 microinches, equivalent to 1.27 to 7.62 micrometers. An intermediate layer made of nickel can be arranged below the precious metal layer, which has a thickness of 25 to 200 microinches, equivalent to 0.635 to 5.08 micrometers. A contact pin is thus formed from an iron-nickel alloy, on which a nickel layer is arranged, the nickel layer in turn being surrounded by a precious metal layer.

[0004] DE 10 2015 206 314 B4 shows a method for producing a glass feedthrough with contact pins. The method is intended to enable the contact pins to be coated before the glazing process, thereby reducing the production time of glass feedthroughs. To do this, contact pins made of an iron-nickel alloy are first provided, which are galvanized with a nickel layer in an electrolyte. The nickel layer is then formatted at 850 °C to 1050 °C in a protective gas atmosphere. The contact pins are coated with palladium, which in turn is formatted at 850 to 1050 °C. The contact pins are then mounted with preforms made of a sealing glass in a device made of graphite. The pins are fused with glass in a vacuum-tight manner in a protective gas atmosphere at 800 to 1100 °C. Applying the individual layers one after the other to the contact pin requires several intermediate steps in the form of heat treatments, which increases the effort and cost of producing the contact pins.

TASK

[0005] It is therefore an object of the present invention to provide an alternative glass feedthrough with high corrosion protection and low contact resistance of its contact pins and a more economical production.

DESCRIPTION

[0006] The object is achieved with a glass feedthrough having the features of patent claim 1.

[0007] The invention relates to a glass feedthrough with at least one contact pin, wherein the contact pin has a core and the core comprises a metal or a metallic alloy. The core is surrounded by a protective layer. The protective layer comprises an alloy of nickel or cobalt and a noble metal.

[0008] When using gold as a protective layer for the contact pin, the high temperatures during the melting process result in such a large diffusion and segregation of the materials of the contact pin that the corrosion protection of the contact pin is greatly reduced. The use of an alloy of nickel or cobalt with a precious metal leads to the surprising effect that the diffusion between the core material and the protective layer and the segregation are greatly reduced by applying only one layer. Since only one layer has to be applied to the contact pin, the production time is also reduced, which in turn enables more cost-effective production.

[0009] In the methods from the prior art and the glass feedthroughs produced with them, the coating must mostly be carried out after the heat treatment as an additional process step. If the heat treatment in the prior art is carried out after the coating, a segregation of the outer layer of the contact pins occurs, whereby the core material of the contact pins protrudes to the outer surface. This results in an uneven distribution of material on the surface of the contact pins, a segregation, which has a negative effect on the properties such as solderability and pluggability of the contact pins.

[0010] In addition, the use of a nickel-precious metal alloy or cobalt-precious metal alloy offers a cheaper alternative to the use of gold. This is not least due to the lower density of the precious metals and the nickel-precious metal alloy or cobalt-precious metal alloy, whereby the same volume can be achieved with a smaller mass.

[0011] The contact pin of the glass feedthrough serves to create a connection. The materials used in the contact pin are electrically conductive and can therefore create an electrical connection. Preferably, the glass feedthrough creates an electrical contact via the contact pin. The protective layer made of an alloy of nickel or cobalt and a precious metal offers both low electrical contact resistance and high corrosion protection.

[0012] The glass feedthrough has at least one contact pin. The contact pin can be used to create a connection, preferably an electrical connection. The contact pin should offer a convenient connection option. The contact pin can advantageously be plugged in, soldered and/or bonded.

[0013] In its simplest form, a glass feedthrough comprises a housing in which a glass body is arranged, in which in turn at least one contact pin is attached. As a rule, the glass body is connected to the housing and the contact pin in a melting process. This results in a vacuum-tight connection between the individual components of the glass feedthrough.

[0014] Preferably, the noble metal in the protective layer is a platinum metal. The following metals form the group of platinum metals: ruthenium, rhodium, palladium, osmium, iridium and platinum.

[0015] In a preferred embodiment, the noble metal in the protective layer is palladium. The use of palladium as a noble metal in the alloy which forms the protective layer shows very good properties with regard to inhibiting diffusion during heat treatment. No segregation of palladium takes place and the proportion of palladium on the surface remains high after heat treatment.

[0016] The protective layer advantageously comprises a nickel-palladium alloy. The combination of nickel and palladium as an alloy shows good performance in inhibiting diffusion in a heat treatment. At the same time, these materials offer good availability and are comparatively inexpensive to purchase and process.

[0017] Preferably, the proportion of palladium in the nickel-palladium alloy or cobalt-palladium alloy is between 30% and 90%, particularly preferably between 50% and 85%. This proportion forms the range in which the advantages of palladium as a component of the electrical contact layer are best apparent. A lower proportion of palladium than 30% has a negative effect on the properties of the contact pin for pluggability, solderability and bondability. At the same time, a proportion of more than 90% palladium has a higher probability of cracking under thermal stress and poorer properties as a plug contact.

[0018] In a further preferred embodiment, the core of the contact pin comprises a nickel-iron alloy or a nickel-iron-cobalt alloy. The use of contact pins made of a nickel-iron alloy or a nickel-iron-cobalt alloy leads to an advantageous design of the contact pin, since the contact pins have, among other things, a thermal expansion coefficient similar to that of glass, which enables vacuum-tight sealing.

[0019] An intermediate layer is preferably arranged between the core and the protective layer in the contact pin. The intermediate layer serves as a diffusion barrier for the core material so that diffusion is minimized during heat treatment. The reduction in diffusion can have a direct effect on the material distribution in the surface after heat treatment, since reduced diffusion leads to a smaller probability of segregation forming in the surface.

[0020] Advantageously, the intermediate layer comprises a metal, preferably copper or nickel. Tests have shown that metal is particularly suitable as a material for the intermediate layer for inhibiting diffusion.

[0021] In a further preferred embodiment, the protective layer has a thickness of 1 to 10 micrometers. The thickness of 1 micrometer is sufficient to maintain the required corrosion protection after the heat treatment. A thickness of more than 10 micrometers, on the other hand, does not lead to significantly better corrosion protection and leads to an increase in manufacturing costs due to the larger volume.

[0022] The glass in the glass feedthrough preferably comprises a sealing glass, more preferably borosilicate glass or barium-alkali glass. It is advantageous both for operation and for the manufacture of the contact pins if the thermal expansion coefficient of the glass is approximately as high as that of the contact pin and at the same time the sealing temperature of the glass is approximately 1000°C. These conditions are met by the sealing glass, in particular by borosilicate glass and barium-alkali glass.

[0023] A further aspect of the invention relates to a method for producing a glass feedthrough, wherein the glass feedthrough has a housing, a glass object and at least one contact pin. The method comprises the following method steps: - providing the housing, a glass body and the contact pin, - applying a nickel-noble metal alloy or cobalt-noble metal alloy as a protective layer to the contact pin, - clamping the housing and the contact pin in a tool, - melting the glass body at a temperature of 800 - 1100 °C to form a glass object which is connected to the housing and the contact pin, - cooling the glass feedthrough and removing it from the tool.

[0024] Applying a nickel-precious metal alloy or cobalt-precious metal alloy as a protective layer to the contact pin has the advantage that the protective layer on the contact pin does not diffuse so strongly during the melting process of the glass body and does not segregate to such an extent that the corrosion protection of the protective layer is reduced. The use of a nickel-precious metal alloy or cobalt-precious metal alloy as a protective layer leads to reduced diffusion between the core and the protective layer of the contact pin, even though the contact pin is exposed to temperatures of 800 to 1100 °C. At the same time, the glass feedthrough only has to be subjected to one heat treatment, which significantly reduces the cost of manufacturing.

[0025] Preferably, the melting of the glass body takes place under a protective atmosphere or in a high vacuum.

[0026] The protective atmosphere is preferably formed by a mixture of hydrogen and nitrogen or by an inert gas, for example noble gases.

[0027] The tool is advantageously made of graphite. Graphite has a high temperature resistance, which means that the temperatures occurring during the melting process do not cause structural deformations. At the same time, the glass does not adhere to the graphite during the melting process and can be dismantled after the melting process without great effort.

[0028] Ideally, the glass object is connected to the housing and the contact pin in a vacuum-tight manner. The vacuum-tight connection can be achieved by melting the glass body, whereby the glass body fills any openings in the housing and thus seals them.

[0029] Preferably, a nickel-palladium alloy is applied as a protective layer. The use of palladium as a noble metal in the alloy which forms the protective layer shows very good properties in terms of inhibiting diffusion during heat treatment. No segregation of palladium takes place and the proportion of palladium on the surface remains high after heat treatment.

[0030] The contact pin preferably comprises a nickel-iron alloy or nickel-iron-cobalt alloy. The use of contact pins made of a nickel-iron alloy or a nickel-iron-cobalt alloy leads to an advantageous design of the contact pin since, among other things, they have a thermal expansion coefficient similar to that of glass, which enables vacuum-tight sealing.

[0031] The optional features mentioned can be implemented in any combination, provided they are not mutually exclusive. In particular, where preferred ranges are specified, further preferred ranges result from combinations of the minima and maxima mentioned in the ranges.

BRIEF DESCRIPTION OF THE CHARACTERS

[0032] The invention is described in more detail below with reference to the figures in a schematic representation. The preferred features mentioned can be implemented in any combination - as long as they do not exclude each other. They show in a non-scale, schematic representation: Figure 1: a front view of a glass feedthrough with 4 contact pins; Figure 2: a cross section through the glass feedthrough from Figure 1; Figure 3: a front view of a glass feedthrough with several contact pins and a glass object; Figure 4: a cross section through the glass feedthrough from Figure 3; Figure 5: a cross section through the edge zone of a contact pin with a protective layer of gold before and after heat treatment; Figure 6: a cross section through the edge zone of a contact pin with a protective layer of palladium-nickel alloy before and after heat treatment; Figure 7: a cross section through the edge zone of a contact pin with a protective layer of palladium-nickel alloy and a pronounced intermediate layer before and after heat treatment.

DETAILED DESCRIPTION OF THE FIGURES

[0033] In the following, the same reference numerals refer to the same or functionally identical elements (in different figures).

[0034] Figure 1 shows a front view of a glass feedthrough 11 according to the invention. The glass feedthrough 11 has four contact pins 13. The glass feedthrough 11 also comprises a housing 15 with a circular outline. Four holes 17 are arranged in the housing 15, which are evenly distributed in the circumferential direction and are equidistant from the center of the housing 15. A glass object 19 is mounted in the holes 17. A contact pin 13 is arranged in each glass object 19. The longitudinal axis of the contact pin 13 is arranged perpendicular to the plan plane of the glass feedthrough 11. The longitudinal axis of the contact pin 13 lies on top of the center axis of the cylindrical hole 17.

[0035] Figure 2 shows a cross section through the middle of the glass feedthrough 11 from Figure 1, wherein the cross section intersects two contact pins 13 of the glass feedthrough 11. The glass feedthrough 11 comprises a housing 15, which has a cylindrical structure with a height that is many times shorter than its diameter. The housing 15 of the glass feedthrough 11 ideally comprises a metal, wherein the housing 15 has through holes 17 parallel to the cylinder axis of the housing 15. The contact pins 13 are each aligned parallel to the cylinder axis and protrude in both directions over the edge of the housing 15. The glass object 19 is intended to be introduced into the feedthrough 17 in the housing 15 by melting it in and to enclose the contact pin 13 arranged therein. Thus, the bore in the glass object 19 has a diameter which is as large as that of a contact pin 13, resulting in a force-fitting connection between the glass body 19 and the contact pin 13.

[0036] Figures 3 and 4 show a further embodiment of a glass feedthrough 11 according to the invention in a front view and in cross section. In contrast to the embodiment in Figure 1, the glass feedthrough 11 in Figure 2 has a glass object 19 through which several contact pins 13 are guided. The diameter of the glass object 19 and the bore 17 in the housing 15 in which the glass object 19 is arranged is correspondingly larger. In this embodiment, the housing 15 forms an outer frame of the glass feedthrough 11. In the middle of the housing 15 there is a bore 17 that is so large that the glass object 19 can accommodate several contact pins 13 therein.

[0037] Figure 5 shows a cross-section showing the material distribution in the outermost layers of a contact pin 13 before and after heat treatment, with the protective layer 21 in Figure 5 being made of gold. The left image shows the state before heat treatment and the right image after heat treatment. Before heat treatment, the boundary of the gold layer as the outermost layer is clearly visible. Furthermore, the gold layer covers the entire surface before heat treatment. In the right image, after heat treatment, a boundary of the protective layer 21 made of gold can still be seen. However, after heat treatment, a changed layer structure and an uneven distribution of gold in the outermost layer can be seen, which is evidence of segregation. This means that the material 23 below the protective layer 21 has diffused outwards and thus forms the surface in places. This in turn has a negative effect on the solderability and pluggability of the contact pins and should therefore be avoided.

[0038] Figure 6 shows a cross-section through the edge of a contact pin 13 which is coated with a protective layer 21 made of a nickel-palladium alloy. The left picture shows the state before and the right picture shows the state after the heat treatment. Before the heat treatment, as with the protective layer 21 made of gold in Figure 5, there is a clear demarcation of the protective layer 21 from the underlying core material 23. In contrast to the design in Figure 5, numerous pores and non-metallic inclusions 25 can be seen below the protective layer 21 in the design in Figure 6. After the heat treatment, no clear demarcation of the layers can be seen in Figure 6. The interface between the protective layer and the core material is blurred due to the diffusion that occurs during the heat treatment. The pores and inclusions 25 remain after the heat treatment. In contrast to the design in Figure 5, no segregation occurs when using a protective layer 21 made of a nickel-palladium alloy. This means that the protective layer 21 is homogeneous and uniform and the proportion of material 23 diffused from the core to the surface is negligible. Thus, the material composition and the material distribution on the surface experience little to no change as a result of the heat treatment.

[0039] Figure 7 shows a comparison of the material distribution in the edge zone of a contact pin using cross sections before and after heat treatment, with the material distribution after heat treatment providing a desirable result. The protective layer 21 comprises a nickel-palladium alloy and has a thickness of approximately 3.6 micrometers. A nickel layer is arranged on the inside of the protective layer 21, which serves as an intermediate layer 27 and has a thickness of approximately 0.8 micrometers, so that the nickel layer together with the protective layer is approximately 4.4 micrometers thick. The nickel layer 27 of 0.8 micrometers counteracts the diffusion of the core material 23 into the surface. The material distribution in Figures 6 and 7 is similar, since before heat treatment a clear demarcation of the protective layer 21 with an interface can be seen, which largely dissolves after heat treatment. This shows that diffusion takes place in the protective layer 21 and in the areas underneath, but that the surface is minimally or not at all affected. To quantify the diffusion of materials to the surface, the proportion of palladium in the surface after heat treatment can be used as an indicator and measurement value. With the structure of the protective layer 21 and intermediate layer 27 shown in Figure 7, the weight proportion of palladium in the surface drops from 82.3% to just 72% as a result of the heat treatment. This value is still so high that the contact pins do not experience any loss in their properties.

[0040] The test samples, the results of which are shown in Figures 6 and 7, have a protective layer 21 made of a nickel-palladium alloy. The test results should serve as an example of the effect of a nickel-noble metal alloy or cobalt-noble metal alloy as a protective layer on a contact pin, since the same qualitative result can be expected when using any other noble metal, in particular a platinum metal, in the alloy instead of palladium or when using cobalt instead of nickel.

[0041] In general, it can be said that the invention has been described above with reference to specific embodiments, but it is obvious that changes, modifications, variations and combinations can be made without departing from the spirit of the invention.

REFERENCE SYMBOL LIST:

[0042] 11 Glass feedthrough 13 Contact pins 15 Housing 17 Hole in the basic structure 19 Glass object 21 Protective layer 23 Core material 25 Pores and inclusions 27 Intermediate layer

Claims (19)

1. A glass feedthrough (11) with at least one contact pin (13), wherein the contact pin (13) has a core (23) and the core (23) comprises a metal or a metallic alloy, and the core (23) is surrounded by a protective layer (21), characterized in that the protective layer (21) comprises an alloy of nickel or cobalt and a noble metal. 2. Glass feedthrough according to claim 1, characterized in that the contact pin (13) is pluggable, solderable and/or bondable. 3. Glass feedthrough according to claim 1 or 2, characterized in that the glass feedthrough creates an electrical contact via the contact pin (13). 4. Glass feedthrough according to one of claims 1 to 3, characterized in that the noble metal in the protective layer (21) is a platinum metal. 5. Glass feedthrough according to claim 4, characterized in that the platinum metal in the protective layer (21) is palladium. 6. Glass feedthrough according to claim 5, characterized in that the protective layer (21) comprises a nickel-palladium alloy. 7. Glass feedthrough according to claim 5 or 6, characterized in that the proportion of palladium in the nickel-palladium alloy or cobalt-palladium alloy is between 30% and 90%. 8. Glass feedthrough according to one of claims 1 to 7, characterized in that the core (23) of the contact pin comprises a nickel-iron alloy or nickel-iron-cobalt alloy. 9. Glass feedthrough according to one of claims 1 to 8, characterized in that an intermediate layer (27) is arranged in the contact pin (13) between the core (23) and the protective layer (21). 10. Glass feedthrough according to claim 9, characterized in that the intermediate layer (27) comprises a metal, preferably copper or nickel. 11. Glass feedthrough according to one of claims 1 to 10, characterized in that the protective layer (21) has a thickness of 1 to 10 micrometers. 12. Glass feedthrough according to one of claims 1 to 11, characterized in that the glass (19) in the glass feedthrough (11) comprises an ice-melting glass, in particular borosilicate glass, soda-lime glass or barium-alkali glass. 13. Method for producing a glass feedthrough (11) comprising the following method steps, wherein the glass feedthrough (11) has a housing (15), a glass object (19) and at least one contact pin (13); - providing the housing (15), a glass body and the contact pin (13), - applying a nickel-noble metal alloy or cobalt-noble metal alloy as a protective layer (21) to the contact pin (13), - clamping the housing (15) and the contact pin (13) in a tool, - melting the glass body at a temperature of 800 - 1100 °C to form a glass object (19) which is connected to the housing (15) and the contact pin (13), - cooling the glass feedthrough (11) and removing it from the tool. 14. Method according to claim 13, characterized in that the melting of the glass body takes place under a protective atmosphere or in a high vacuum. 15. The method according to claim 13 or 14, characterized in that the protective atmosphere is formed by a mixture of hydrogen and nitrogen or by an inert gas. 16. Method according to one of claims 13 to 15, characterized in that the tool consists of graphite. 17. Method according to one of claims 13 to 16, characterized in that the glass object (19) is connected to the housing (15) and the contact pin (13) in a vacuum-tight manner. 18. Method according to one of claims 13 to 17, characterized in that a nickel-palladium alloy is applied as the protective layer (21). 19. Method according to one of claims 13 to 18, characterized in that the contact pin (13) comprises a nickel-iron alloy.