NL1023174C2 - Bonding ceramic substrate containing silicon to metallic material, by providing intermediate, reactive solder and metal layers on substrate and then heating - Google Patents

Abstract

Intermediate layer, reactive solder material and metallic material are provided on the ceramic substrate and the assembly is then heated to melt the solder. Permanently bonding a ceramic substrate comprising silicon with a metallic material using a reactive solder material comprises: (a) providing a ceramic substrate comprising silicon; (b) providing an intermediate layer on the substrate; (c) providing reactive solder material on the intermediate layer; (d) providing metallic material on the solder material; and (e) heating the assembly to a temperature above the melting point of the solder material so that a permanent bond is formed between the substrate and metallic material. An independent claim is also included for an assembly prepared by this method, the substrate containing 1-40 vol.% free silicon.

Description

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Brief indication: Method for the durable connection of a substrate with a metallic material, as well as an assembly obtained therewith.

The present invention relates to a method for the durable joining of a ceramic substrate containing Si with a metal-like material using a reactive soldering material. The present invention furthermore relates to an assembly made up of, successively, a ceramic substrate containing Si, an intermediate layer and a metal-like material permanently connected thereto via a solder measure.

The properties that make ceramic materials suitable for high temperature applications include the excellent high temperature strength and creep resistance, good strength retention as a function of time and the excellent properties in the field of resistance to oxidation and wear. In addition to the aforementioned properties, the silicon nitride and silicon carbide families of the ceramic materials have low thermal expansion coefficients and thus good thermal shock resistance. For certain applications, it is desirable that ceramic materials with metal-like components be permanently bonded. Three aspects play an important role in the interconnection of metals with ceramic materials, namely 1) chemical reaction between the two materials, 2) poor wetting of the ceramic material by liquid metals and 3) the difference in coefficient of expansion between the metal and the ceramic material. Chemical reactions between the metal and the ceramic material can result in the formation of undesirable components in the final product. Moisture problems only arise when a liquid phase is used to interconnect the two materials. Coefficients of thermal expansion that do not coincide with each other result in the development of high stresses at the metal-ceramic material interface, particularly during the cooling phase from the temperatures where the materials are interconnected, and this effect can cause a decrease in bonding strength or even a decrease in bonding strength. cause the connection on the interface 5 to break.

U.S. Pat. No. 6,440,590 discloses a method in which an active metal-containing metallization layer is connected to a ceramic substrate. The structure obtained by such a method comprises a silicon-containing ceramic body, an active metal-containing top layer bonded to and applied to the surface of the ceramic body, and a reaction layer on the interface of the ceramic body and the top layer. The reaction layer comprises a first reaction layer which comprises a connection of a non-metallic element of one of the forming elements of the ceramic body and the active metal 15 as the main component, which first reaction layer is located near the surface of the ceramic body. The reaction layer also comprises a second reaction layer containing a silicon compound of the ceramic body forming elements and an active metal as a main component, which second reaction layer is located in the vicinity of the top layer. Silicon nitride has been mentioned as a suitable ceramic body, Ti, Zr, Hf, Nb, Al, V and Ta being mentioned as the active metal. In a particular embodiment, the ceramic body is silicon nitride and the active metal is titanium. According to this US patent specification, silicon carbide would also be suitable as a ceramic body. However, research has shown that free silicon-containing silicon carbide cannot be soldered according to the method known from this US patent specification, while it can furthermore be stated that the example shown in this US patent specification relates only to silicon nitride as a ceramic body on which a alloy with a composition of 67.7% by weight of Ag, 27.4% by weight of Cu and 4.9% by weight of Ti is applied by melting at a high temperature and a reduced pressure lower than 10-3 Pa. Heating is carried out at temperatures around the melting point of this alloy, namely 1183 K or higher.

A first aspect of the present invention thus comprises providing a method for permanently joining a substrate containing Si with a metallic material.

Another aspect of the present invention is to provide a method for durably joining an Si-containing substrate with a metal-like material, whereby a tear-free joint is obtained which exhibits good adhesion to the substrate.

The method as stated in the preamble is characterized in that the method comprises the following steps: i) providing the ceramic substrate containing Si, ii) applying an intermediate layer to the substrate according to step i), iii) applying it to the intermediate layer according to step ii) applying the reactive solder size, iv) applying the metal-like material to be permanently joined to the reactive solder material according to step iii), and v) subsequently heating the thus obtained assembly of successively substrate, intermediate layer, solder material and metal-like material up to a temperature above the melting temperature of the solder material that a durable connection between the substrate and metal-like material is obtained.

Using the present method, a durable connection is established between an Si-containing substrate and a metallic material, with a helium leak-proof connection, i.e., leakage <10-9 mbar. Γ1. s'1.

A suitable ceramic substrate is selected from 1 i; 7 r4 1 7 Λ

silicon nitride, sialon and silicon carbide, preferably an SiC

I-containing substrate is used which contains free silicon.

The free silicon content in the substrate containing SiC is preferably 1-40 vol%, in particular 15-35 vol%.

If the free silicon content in the substrate containing silicon carbide I is less than 1% by volume, the bonding strength between the ceramic substrate and the metal-like material is sufficient. More in particular, a free silicon content in the ceramic substrate lower than 11% by volume leads to the fact that the intermediate layer according to step ii) can be dispensed with. On the other hand, if the content of free silicon in the substrate containing silicon carbide is more than 40% by volume, a compound will be obtained which is subject to cracking, in which the application of the intermediate layer according to step ii) is very problematic.

In the present method, a so-called intermediate layer is applied to the substrate according to step ii), which intermediate layer has the function that the substrate cannot come into direct contact with the reactive solder material to be applied according to step iii).

It is preferable that the intermediate layer according to step I ii) is selected from the group of carbides, nitrides and oxides of I elements belonging to Group IIIA, IVA, VIB, VB of the Periodic I System, in particular the intermediate layer according to step ii) is selected from the group of silicon carbide and aluminum nitride, or a combination thereof.

The method of applying the intermediate layer according to step ii) I is in particular not critical and can be applied, for example, via chemical vapor deposition (CVD) or via sputtering. However, it should be understood that the application of the intermediate layer according to step ii) is carried out in such a way that direct contact between the substrate and the soldering material is prevented. A dense intermediate layer must thus be provided.

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In a particular embodiment, it is desirable that the reactive solder size according to step iii) comprise one or more active elements selected from the group of Zn, Mn, Ni, In and Ti, with a solder in particular as reactive solder size. based on Ag-Cu-5 Zu-Mn-Ni.

The function of an active element in the solder sizes is to lower the contact angle between the ceramic substrate and the liquid solder sizes when the solder sizes has been transferred to the liquid phase by heating. Moreover, the active element can also take care of the removal of oxygen on the ceramic and metal surface, whereby the adhesion of the reactive solder sizes is further improved.

As a suitable metal-like material according to step iv), materials with a melting point higher than the melting point of the soldering materials are used, in particular a metal-like material being used selected from the group of stainless steel, titanium, molybdenum, tantalum-zirconium-molybdenum and cobalt-based metals.

The present inventors have found that changing both process pressures and process gas can lead to small adjustments in the soldering temperatures. It has thus been found that a good durable connection can be realized under atmospheric pressure, whereby argon is used as the protective gas. In addition, it is also possible in a special embodiment for vacuum (<10'4 mbar) or underpressure (10'4 - 10'1 mbar) to be used, in addition to which argon is used as the protective gas.

As indicated above in a special embodiment, however, the active element can not only be supplied via the soldering material, but in certain embodiments it may be preferable that an additional step vi) be carried out between step iii) and step iv), which step step vi) applying

1 Π 9 9 1 7 A

I of a Ti-containing intermediate layer.

In such an embodiment, for example, a foil of titanium is placed on the already applied layer of solder sizes of metal I, whereafter subsequently applied to the foil containing titanium and the metal-like material to be permanently bonded.

In another embodiment it may optionally be preferred that an additional step vii) I be carried out between step ii) and step iii), which step vii) comprises applying an intermediate layer containing Ti containing I, e.g. sputtering a thin layer of titanium or applying a foil of titanium.

The soldering material I used in the present method is in principle a eutectic soldering material based on silver-copper.

In certain embodiments, however, it is also possible that gold-based solder sizes are already being used. A drawback of such a type of soldering material, however, is the higher soldering temperature I (difference is approximately 100 ° C) with respect to the silver-copper-based soldering sizes. As a result of the higher soldering temperature, the reactivity of the soldering material to the substrate will increase considerably and tensions can possibly be built up in the soldered connection, in particular caused by the difference in coefficient of expansion of ceramic substrate and metal.

As indicated above, the active element I can thus be supplied via the soldering material, or a thin layer of titanium is applied to the soldering material, or a foil of titanium is placed on the intermediate layer, or the metallic material to be bonded. I material is itself made of titanium. In all the aforementioned I embodiments, titanium will bring about a reduction in the contact angle between the soldering material and the ceramic substrate and then I will enter into a chemical reaction with a part of the intermediate layer already applied to the substrate in step ii). Thus, in certain embodiments, it is possible to use a silver-copper based 7 solder sizes to which no further additives have been added.

The present invention further relates to an assembly made up of, successively, a ceramic substrate containing Si, an intermediate layer and a metal-like material permanently connected thereto via a solder size, which assembly is characterized in that the content of free silicon in the substrate is 1-40 volume%, preferably 15-35 volume%.

In a special embodiment the intermediate layer of the assembly shown above is selected from the group of carbides, nitrides and oxides of elements belonging to Group IIIA, IVA, VIB, VB of the Periodic Table, in particular the intermediate layer is selected from the group of silicon carbide and aluminum nitride, or a combination thereof.

The metal-like material used in the present assembly is a material with melting point higher than the melting point of the soldering material, preferably a material selected from the group consisting of stainless steel, titanium, molybdenum, tantalum-zirconium-molybdenum and cobalt-based metals .

The present invention will be explained below with reference to a number of examples, but it should be noted, however, that the present invention is by no means limited to such special examples.

Example 1

A substrate of silicon carbide, the free silicon content of which is 25% by volume, was provided with a thin layer of silicon carbide by evaporation. A film of solder material with a thickness of 100 microns was laid on the intermediate layer thus applied via evaporation. The composition of the film was: 44% silver, 30% copper, 24% zinc, 7% manganese, 5% nickel.

A titanium cylinder was then placed on the solder foil with 1 fl 9 * 3 1 7 4.

a diameter of 20 mm and a wall thickness of 1 mm. Subsequently, a weight with a mass of 200 grams was placed on the I cylinder of titanium, after which the whole was heated in an oven to 870 ° C under controlled conditions. The oven was flushed with argon and the pressure was 5 to 10 Pa. After reaching this temperature, the assembly was cooled and then taken out of the oven and used for further use.

Example 2 A thin layer of silicon carbide was applied to a silicon carbide substrate, the content of which was free silicon by 25 vol.%. Subsequently, a silicon solder film with a thickness of 100 microns was placed on the intermediate layer of silicon carbide thus applied via evaporation. The composition of the solder foil was: 68.8% by weight of silver, 26.7% by weight of copper and 4.5% by weight of titanium. A molybdenum cylinder with a diameter of 10 mm and a wall thickness of 1 mm was then placed on the solder foil. A weight of 200 grams I was applied to the ring, after which the whole was placed in an oven and heated to a temperature of 900 ° C. The oven was flushed with argon and the pressure I was 10 Pa. After reaching the aforementioned temperature, the assembly was immediately cooled, taken out of the oven and prepared for further use.

Example 3 A thin layer of silicon carbide was applied by chemical vapor deposition to a ceramic substrate of silicon carbide, the content of which was free silicon. A layer of 100 micrometres of thickness was applied to the intermediate layer thus applied via evaporation, the composition of which was: 44% by weight of silver, 20% by weight of copper, 24% by weight of zinc, 7% by weight % manganese and 5% nickel. A titanium foil was then placed on the solder foil, after which a cylinder of molybdenum I with a diameter of 10 mm and a wall thickness of 1 mm was subsequently installed.

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A weight of 200 grams was placed on the ring and the whole was transferred to an oven and heated to a temperature of 870 ° C. The oven was purged with argon gas and the pressure was 10 Pa. After the assembly had reached the aforementioned temperature, it was immediately cooled and taken out of the oven and made ready for further use.

Example 4

A ceramic substrate of silicon carbide, the free silicon content of which was 25% by volume, was provided with a thin layer of silicon carbide by chemical vapor deposition. A layer of 1 micron of titanium and 9 micron of silver was then sputtered on the intermediate layer thus applied. A titanium cylinder with a diameter of 20 mm and a wall thickness of 1 mm was then placed on the layer applied by sputtering. The ring was provided with a weight with a mass of 200 grams, after which the whole was transferred to an oven and heated to a temperature of 950 ° C. The oven was purged with argon and the pressure maintained at a constant value of 10 Pa. After the aforementioned temperature was reached, the oven was cooled and after cooling, the thus treated assembly was removed from the oven 20 and made ready for further use.

Example 1 for comparison

On a silicon carbide ceramic substrate, the free silicon content of which was 25% by volume, a foil of solder dimensions of 150 µm thickness was laid, the composition of which was: 44% silver, 20% copper 24% by weight of zinc, 7% by weight of manganese and 5% by weight of nickel. A titanium cylinder with a diameter of 20 mm and a wall thickness of 1 mm was then installed on the solder foil. A weight of 200 grams was placed on the ring and the whole was transferred to an oven, bringing the oven under reduced pressure, flushed with argon and maintaining the pressure at a value of 10 Pa. The oven was heated to a temperature of 1 V | I 870 * C and immediately cooled to H after reaching the aforementioned temperature. After cooling, the assembly was taken out of the oven and subjected to an I analysis, which analysis made it clear that the assembly I was found not to be vacuum tight. Additional investigation revealed that the silicon had reacted very violently with the metals from the solder foil and I the titanium, which led to many cracks in the ceramic substrate I under the applied ring of titanium.

Example 5 I A silicon carbide ceramic substrate, the free silicon content of which was 0.6% by volume, was provided with a thin layer of silicon carbide by chemical vapor deposition. A foil of solder dimensions with a thickness of 100 μιη was then applied to the intermediate layer thus applied. The composition of the solder foil was: 68.8% by weight of silver, 26.7% by weight of copper and 4.5% by weight of titanium. A molybdenum cylinder with a diameter of 10 mm I and a wall thickness of 1 mm was then placed on the solder foil. A weight of 200 grams was applied to the ring, after which the whole was placed in an oven and heated to a temperature of 900 ° C. The oven was flushed with argon and the pressure was 10 Pa. After reaching the aforementioned temperature, the assembly was immediately cooled, taken out of the oven and made ready for further use.

Comparative Example 2 The same operations as described in Example 5 were repeated except that no silicon carbide interlayer was applied. An assembly was obtained which had properties similar to the assembly obtained according to Example 5.

Example 6

A thin layer of silicon carbide was applied to a silicon carbide substrate, the content of which was free silicon by 1.2 vol.%. A foil of 11 solder material having a thickness of 100 µm was then placed on the intermediate layer of silicon carbide thus applied via evaporation. The composition of the solder foil was: 68.8% by weight of silver, 26.7% by weight of copper and 4.5% by weight of titanium. A molybdenum cylinder with a diameter of 10 mm and a wall thickness of 1 mm was then placed on the solder foil. A weight of 200 grams was applied to the ring, after which the whole was placed in an oven and heated to a temperature of 900 ° C. The oven was flushed with argon and the pressure was 10 Pa. After reaching the aforementioned temperature, the assembly was immediately cooled, taken out of the oven and made ready for further use.

Example 7

A thin layer of silicon carbide was applied to a silicon carbide substrate, the free silicon content of which was 9% by volume. A foil of solder material with a thickness of 150 µm was then placed on the intermediate layer of silicon carbide thus applied via evaporation. The composition of the solder foil was: 44% by weight of silver, 20% by weight of copper, 24% by weight of zinc, 7% by weight of manganese and 5% by weight of nickel. A titanium cylinder with a diameter of 20 mm and a wall thickness of 1 mm was then placed on the foil. A weight of 200 grams was applied to the ring, after which the whole was placed in an oven and heated to a temperature of 870 ° C. The oven was flushed with argon and the pressure was 10 Pa. After reaching the aforementioned temperature, the assembly was immediately cooled, taken out of the oven and made ready for further use.

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Claims (21)

A method for permanently joining a ceramic substrate containing Si with a metallic material using a reactive solder, characterized in that the method comprises the following steps: i) providing the ceramic substrate containing Si I, ii) applying an intermediate layer to the substrate according to step i), iii) applying the reactive solder material to the intermediate layer according to step ii), iv) applying it to the reactive solder material according to step I iii) applying the metal-like material to be permanently joined, and v) subsequently heating the thus obtained assembly of successively substrate, intermediate layer, solder material and metal-like material to a temperature above the melting temperature of the soldering material that a durable connection I between the substrate and metal-like material is obtained. I 20 A method according to claim 1, characterized in that the ceramic substrate is selected from silicon nitride, sialon and silicon carbide. Method according to claim 2, characterized in that an SiCI-containing substrate is used which contains free silicon. I 25 Method according to claim 3, characterized in that the content of free silicon is 1-40% by volume. A method according to claim 4, characterized in that the content of free silicon is 15-35% by volume. 6. A method according to claim 1, characterized in that the intermediate layer according to step ii) is selected from the group of carbides, nitrides and oxides of elements belonging to Group IIIA, IVA, VIB, VB of the Periodic Table. Method according to claim 6, characterized in that the intermediate layer according to step ii) is selected from the group of silicon carbide and aluminum nitride, or a combination thereof. Method according to one or more of the preceding claims, characterized in that the application of the intermediate layer according to step ii) is carried out in such a way that direct contact between the substrate and the solder sizes is prevented. 9. Method according to one or more of the preceding claims, characterized in that the reactive solder material according to step iii) comprises one or more active elements selected from the group of Zn, Mn, Ni, In and Ti. 10. Method according to one or more of the preceding claims, characterized in that the reactive solder material used is a solder based on Ag-Cu-Zu-Mn-Ni. Method according to one or more of the preceding claims, characterized in that materials with a melting point higher than the melting point of the soldering material are used as the metal-like material according to step iv). Method according to claim 11, characterized in that the metal-like material according to step iv) is a material selected from the group consisting of stainless steel, titanium, molybdenum, tantalum zirconium molybdenum and cobalt-based metals. 13. Method according to one or more of the preceding claims, characterized in that step v) is carried out under reduced pressure. 14. Method according to one or more of the preceding claims, characterized in that an additional step vi) is carried out between step iii) and step iv), said step vi) comprising applying an intermediate layer containing Ti. 15. Method according to one or more of the preceding 1 773 774. Claims, characterized in that an additional step vii) is carried out between step ii) and step iii), which step vii) comprises applying an intermediate layer containing Ti. 16. An assembly constructed from, successively, a ceramic substrate containing Si, an intermediate layer and a metal-like material permanently connected thereto via a soldering material, characterized in that the content of free silicon in the substrate is 1-40 vol. %. 17. An assembly according to claim 16, characterized in that the content of free silicon in the substrate is 15-35% by volume. Assembly according to one or more of claims 16-17, characterized in that the intermediate layer is selected from the group of carbides, nitrides and oxides of elements belonging to Group IIIA, IVA, VIB, VB I of the Periodic System. I 15 An assembly according to claim 18, characterized in that the intermediate layer is selected from the group consisting of silicon carbide and aluminum nitride, or a combination thereof. Assembly according to one or more of claims 16-19, characterized in that the metal-like material according to step iv) is material I with a melting point higher than the melting point of the soldering material. 21. An assembly according to claim 20, characterized in that the metal-like material used is a material selected from the group consisting of stainless steel, titanium, molybdenum, tantalum-zirconium-molybdenum and cobalt-based metals.