JP2005139057A - Method for metallizing powder sintered ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for metallization applicable to oxide-based, nitride-based, carbide-based, and machinable ceramics. <P>SOLUTION: The material constituting a metallized layer is a mixture comprising one kind among Ti, TiH, and TiH<SB>2</SB>with a particle diameter of ≤50 μm and one kind among Fe, Ni, Cu, Ag, Au, Ta, and W with the same particle diameter, where the weight ratio of Ti is 10-60%. The material without or with an addition of less than 50 wt.% of the same material as a ceramic to be metallized, which is ground to have a particle diameter of ≤50 μm, is painted on the surface of the ceramic to be metallized and sintered in vacuum or in an inert gas atmosphere not containing or containing hydrogen at a temperature of ≥500°C and below the melting point of the metal bulk material mixed with Ti. When the sintering temperature is ≥900°C under the same conditions, TiO<SB>2</SB>powder is used in place of Ti, TiH, or TiH<SB>2</SB>powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention mainly comprises oxide ceramics typified by alumina ceramics (Al ₂ O ₃ ), nitride ceramics such as silicon nitride (Si ₃ N ₄ ), carbide ceramics such as silicon carbide (SiC), and fluorine. In order to join a free-cutting ceramic, which is one of the components, to a metal, a method of metallizing the joining portion of these ceramic surfaces is provided.

  A molybdenum-manganese method (Mo-Mn) method is generally used as a method for melatalizing oxidized ceramics. This is made by applying a small amount of titanium (Ti), titanium hydride, or a mixture of titanium oxide and glass with Mo and Mn as the main component to the ceramic surface and sintering at about 1400-1500 ° C using a redox furnace. This is a method of using the processed metallization layer. The tensile stress of the metallized layer is said to be the highest as compared with other methods.

  However, this method cannot be applied to nitride-based and carbide-based ceramics. This is because there is no oxygen on the ceramic side that binds to the reduced Mo particles. This is because the free-cutting ceramic is melted because its melting point is 1200 to 1300 ° C. Also, quartz, which is a kind of oxide ceramics, cannot be metallized. The reason is that the thermal expansion coefficient of quartz is much smaller than that of the Mo—Mn layer. Of course, joining with quartz is impossible for the same reason as the brazed metal.

Non-oxide ceramics or free-cutting ceramics and metal can be joined directly by a silver solder in which Ti is mixed into the brazing material without providing a preliminary metallization layer such as a Mo-Mn layer. In recent years, materials have become commercially available. A typical silver brazing material is a BAg-8 (Ag—Cu alloy) brazing material containing 2% by weight of Ti.
Patent document 1 etc. are mentioned as an example which joins a metal to nitride type ceramics using such a brazing material.
Japanese Patent No. 1826790

  The shape of the brazing material is a plate, a wire or a powder. Ti diffuses into the ceramic at a high temperature above the melting point of the brazing material and improves the wettability of the brazing material to its surface. However, it is extremely difficult to braze the metal member and the ceramic with high accuracy using an active brazing material when there are many joints. This is because a carbon jig that is commonly used for positioning metal members and ceramics cannot be used for normal inactive (Mo-Mn method) brazing. This is because silver solder wets the carbon jig well, and the silver solder leaked during brazing brazes the carbon jig with a metal member or ceramic cloth. A carbon jig once brazed cannot be removed.

As the jig material, a boron nitride material having poor wettability of silver raw material may be used. However, this material itself is very expensive, and its use as a jig material is limited.
In the joining of quartz and metal members, the difference in thermal expansion between silver brazing and quartz is large, so that many fine cracks are generated on the surface of quartz wetted by the brazing material during cooling immediately after brazing.

  The problem to be solved by the present invention is that, in the vacuum field and the high-temperature and high-pressure fluid processing field, as a specification required for a joint portion between a metal and a ceramic, it can withstand a heat treatment of at least 200 ° C. Also, helium leak tight and geometrically accurate joining are required.

As a result of intensive studies, the inventor has found that Ti fine particles and metal fine particles having a size of 50 μm or less can be used as the material and form of the metallized layer. It is known that the melting point of metal fine particles decreases as the size thereof decreases. This is because atoms on the surface have weaker binding energy with adjacent atoms than atoms in the bulk of the fine particles. Therefore, the smaller the size of the fine particles, the higher the ratio of the number of surface atoms to the number of atoms in the bulk, and the lower the melting point of the fine particles.
For example, the melting point of a gold bulk material is 1064 ° C., but when the particle size is reduced to the nm order, the melting point drops to about room temperature.

  Using this principle, the present method sinters metal particles below the bulk melting point. At the same time, the mixed Ti atoms diffuse into the ceramic and also into the metal particles. Thus, the metal particle group forms a metallized layer by forming a metal bond with the ceramic.

Based on the above principle, the means for solving this problem is as follows.

The first means of the invention corresponds to claim 1 and is any one of powders of Ti, TiH or TiH ₂ and particles of Fe, Ni, Cu, Ag, Au, T2, and W each having a particle size of 50 μm or less. Apply a mixture of one kind so that the weight ratio of Ti powder is 10% or more and 60% or less, and apply it to the surface of the ceramic surface to be metallized, in a vacuum or in an inert gas atmosphere, or inert containing hydrogen The metallized layer is formed on the sintered ceramic by sintering at a temperature of 500 ° C. or higher and lower than the melting point of the metal mixed with Ti in a gas atmosphere.

  The second means of the present invention corresponds to claim 2, and in addition to claim 1, in addition to the mixing ratio of claim 1, the weight of the metallized ceramic powder having a particle size of 50 μm or less is 50% by weight. A metallized layer is constructed on the sintered ceramic by mixing them at the following ratio.

The third means of the present invention corresponds to claim 3, and when the sintering temperature is 900 ° C. or higher in the first and second means of the present invention, TiO instead of the use of Ti, TiH, TiH ₂ powder is used. _Two powders are used to build a metallized layer on sintered ceramics.

  According to the first means of the present invention, since the metallized layer is formed at a temperature lower than the melting point of the metal bulk, the stress due to the difference in thermal expansion to the underlying ceramic is reduced. Moreover, since it is powder sintering, unlike the metal bulk melt solidification, the ceramic surface stress after sintering can be reduced. For this reason, the effect that metallization to quartz with extremely small thermal expansion is possible has been achieved.

  According to the second means of the present invention, a part of the Ti particles before sintering is atomically diffused into the ceramic and metal particles. If the Ti particles on the surface of the metallized layer have a small particle size, they will diffuse with each other to form a uniform alloy on the ceramic surface. It seems that Ti atoms on the metallized surface are easily oxidized to form a stable oxide. Therefore, even if the metallized layer touches the carbon jig disposed during brazing, there is no concern that Ti atoms will diffuse from the metallized layer outside the BAg-8 silver solder and the ceramics and carbon jig will be brazed. There is an effect.

  In the metallization of quartz, the metallization can be directly performed by the method of claim 1, but it is also possible to simultaneously sinter by mixing quartz powder having the same size or less as the metal fine particles into the constituent metal fine particle group. Then, the thermal contraction rate at the time of the temperature fall of a metallization layer becomes small, and the stress between quartz and a metallization layer is relieved.

  As the part to be metal-bonded to quartz becomes larger, further stress relaxation measures are required. As a countermeasure, first, metal particles having a low Young's modulus are heated on the existing metallized layer below the melting point of the bulk metal and sintered. In the case where the metallized layer is required to be helium / leak tight, the sintered metal surface is plated. This is heated and baked in a vacuum. The baking temperature is equal to or lower than the bulk melting point of the sintered metal. What is necessary is just to braze a to-be-joined metal member on this.

The following eight examples are given as the best mode for carrying out the present invention.

FIG. 1 is a cross-sectional view showing a first example of an embodiment of the present invention. FIG. 2 is a partially enlarged view showing details of a portion A of FIG. 1, that is, metallization and brazing portions.
In FIGS. 1 and 2, reference numeral 1 denotes a copper plate to be brazed. Reference numeral 2 denotes an alumina ceramic ring which is another brazing body. The upper part of the copper plate 1 is disk-shaped, and the lower side in contact with the upper surface of the alumina ceramic ring 2 is processed into a cylindrical shape having an outer diameter of 21.65 mm and an inner diameter of 20.35 mm to facilitate brazing. The alumina ceramic ring 2 is processed to have an outer diameter of 24 mm, an inner diameter of 18 mm, and a thickness of 6 mm, and all corners are chamfered to 0.5 mm. The materials were purchased from Nippon Ceratech Co., Ltd. and used for experiments.

Metallization is a mixture of Ti: 20-30 μm particle size powder and ˜50 μm square copper foil pieces mixed in a weight ratio of 4 to 6, dissolved in an organic binder, applied to the joint surface, dried and vacuumed. The metallized layer 4 was completed by sintering in an oven at 1000 ° C. for 20 minutes. An annular portion of a copper plate was placed thereon as shown in the figure and adhered by a known method using BAg-8 silver solder.
The result of this test was that the metallized surface of the alumina ceramic ring 2 had no defects such as scratches and was in a very good adhesion state. Silver low was also in very good adhesion.

A second embodiment will be described with reference to FIGS. FIG. 3 is a sectional view showing a second example of the embodiment of the present invention. FIG. 4 is a partially enlarged view showing the details of the B portion of FIG. 3, that is, the metallized layer and the brazed portion.
In FIG. 3, 10 is a Kovar plate. Unlike the copper plate 1, the Kovar plate 10 is a disc having a thickness of 1 mm and an outer diameter of 25 mm.
5 is a silicon nitride ring. The silicon nitride ring 5 has an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 9 mm. Materials were purchased from Nippon Ceratech Co., Ltd. and used for experiments.

A metallized material having the same specifications as in Example 1 was used for the silicon nitride ring 5, and the metallized layer 4 was completed under the same temperature conditions. The Kovar plate 10 was bonded onto the metallized layer 4 with the silver row 3 using the above BAg-8 silver row.
As a result, the silver row 3 firmly adhered the Kovar plate 10 to the metallized layer 4 that was firmly formed on the silicon nitride ring 5.

It was confirmed that the silver row 3 welded to the metallized layer 4 according to the present invention did not adhere carbon even when the melting temperature of the silver row 3 was exceeded. FIG. 5 is a sectional view showing a third example of the embodiment of the present invention. FIG. 6 is a partially enlarged view showing details of a portion C of FIG. 5, that is, a metallized layer and a brazed portion.
In FIG. 5, 11 is a carbon plate. The carbon plate 11 is a disc having a thickness of 3 mm and an outer diameter of 18 mm. 5 is a silicon nitride ring. As the silicon nitride ring 5, a ring having the same material and dimensions as those used in Example 2 was used. Reference numeral 12 denotes a weight. The weight 12 is made of iron having an outer diameter of 12 mm and a weight of 500 g, and is placed on the ring 5 so as to directly apply a load to the silicon nitride ring 5.

For this purpose, a metallized layer is completed on the upper end surface of the silicon nitride ring 6 under the same procedure and conditions as in Example 2, and a carbon plate is placed on the one obtained by depositing silver solder on it and cooling and solidifying it as shown in FIG. The sample was pressed with a weight 12 and held at 900 ° C. for 20 minutes in a vacuum furnace. As a result of visual confirmation after cooling, no marks of adhesion were found on the surface of the silver row 3 on the metallized layer 4 and the carbon plate 11.
From the above experiment, it was confirmed that a carbon jig can be used for silver brazing of ceramics and metal by the Ti and copper sintered metallization method.

A fourth embodiment will be described with reference to FIGS. FIG. 7 is a sectional view showing a fourth example of the embodiment of the present invention. FIG. 8 is a partially enlarged view showing details of a portion D in FIG.
In FIG. 7, reference numeral 10 denotes a Kovar plate. 13 is a free-cutting ceramic. As the size of the free-cutting ceramic 13, an outer diameter of 20 mm, an inner diameter of 14 mm, and a thickness of 11 mm were purchased and used for experiments.
The free-cutting ceramic 13 was made of a metallized material having the same specifications as in Example 1, and the metallized layer 4 was completed under the same temperature conditions. Further, the Kovar plate 10 was bonded to the metallized layer 4 with BAg-8 silver solder 3 under the same materials and conditions as described in Example 2.
As a result, the Kovar plate 10 was firmly bonded to the metallized layer 12 that was firmly formed on the free-cutting ceramic ring 13.

  A fifth embodiment will be described with reference to FIG. FIG. 9 shows a fifth embodiment of the Ti metallization method according to the present invention. Reference numeral 20 denotes a quartz cylinder. The quartz cylinder 20 has a cylindrical shape with an outer diameter of 10 mm, an inner diameter of 7.4 mm, and a height of 19 mm. Reference numeral 21 denotes an oxygen-free copper tube. The oxygen-free copper tube 21 is a compression tool by enlarging the inner diameter of the portion accommodating the quartz cylinder 20. Here, a method of flowing BAg-8 silver solder through the joint and a method of melting and joining aluminum powder in the joint gap without using a brazing material in a vacuum below the melting point of aluminum were attempted. As a result, except for the case where the ceramic was brazed with aluminum, the ceramic could be joined firmly without cracks. It was helium tight.

FIG. 10 is a sectional view showing a sixth example of the embodiment of the present invention. FIG. 11 is a partially enlarged view showing a state of an adhesive portion formed by the E portion of FIG. 10, that is, a metallized layer. In this example, the brazing in Example 1 is omitted and the metallized layer is directly bonded. Accordingly, the parts described in FIGS. 1 and 2 are denoted by the same reference numerals and the description thereof is omitted.
In FIG. 10, reference numeral 1 denotes a copper plate to be brazed. 2 also experimented with a combination of a free-cutting ceramic 13 instead of the alumina ceramic ring 2 and the alumina ceramic ring 2 which are other brazed bodies. The specifications of the copper plate 1 and the alumina ceramic ring 2 or the free-cutting ceramic 13 are parts having the same specifications as those described in the first and fourth embodiments.
As shown in FIG. 11, the material of the metallization is a mixture of Ti: 20-30 μm particle diameter powder and ˜50 μm square copper foil pieces in a weight ratio of 4 to 6, and this is dissolved in an organic binder. The metallized layer 4 was completed by coating and drying so as to rise up to the joint between the lower end of the copper tube 1 and the alumina ceramic ring 2 and sintering in a vacuum furnace at 1000 ° C. for 20 minutes. The joint was securely joined as in BAg-8 silver solder.
As a result of this test, the metallized surface of the alumina ceramic ring 2 had no defects such as scratches, and was in a very good adhesion state together with the copper-side joint, and was helium leak tight.
Also, the metallized surface of the free-cutting ceramic ring 13 was free from defects such as scratches, and the joint portion along with the copper side was in a very good adhesion state, and helium leak tight.

A seventh embodiment will be described with reference to FIGS. FIG. 12 is a sectional view showing a seventh example of the embodiment of the present invention. FIG. 13 is a partially enlarged view showing the details of the F portion of FIG. 12, that is, the metallized layer. In this example, the brazing in Example 2 is omitted and the metallized layer is directly bonded. Therefore, the same reference numerals are given to the portions described in FIG. 3 and FIG.
In FIG. 7, reference numeral 10 denotes the Kovar plate. 5 is the silicon nitride ring. Reference numeral 13 denotes the free-cutting ceramic.
As the free-cutting ceramics 13, a metallized material having the same specifications as in Example 2 was used, and the Kovar plate 10 was bonded by the metallized layer 4 under the same temperature conditions. As a result, the Kovar plate 10 was firmly bonded to the metallized layer 4 firmly formed on the free-cutting ceramic ring 13. The metallized layer 4 was helium liquefied.

Example 8 will be described with reference to FIG. FIG. 14 shows an example of the shape of the Ti metallization method according to the present invention. In this embodiment, the quartz tube and the non-oxidized copper tube are to be bonded by the metallized layer 4 instead of the silver row 3 described in the fifth embodiment. Accordingly, the same parts and materials as those described in the fifth embodiment are designated by the same reference numerals and description thereof is omitted.
In FIG. 14, 20 is the quartz cylinder. 21 is copper oxide free. Reference numeral 23 denotes a metallized layer.

  As a result, the ceramics could be joined firmly without cracks. It was helium leak tight.

  We have opened the way to metallization of nitrides, carbides, and free-cutting ceramics and quartz, which have been difficult to bond. This has opened the way for adhesion between metals and these ceramics. As a result, a product using these ceramics can be manufactured with high reliability and excellent durability.

It is sectional drawing explaining Example 1 of this invention. It is the A section enlarged view of FIG. It is sectional drawing explaining Example 2 of this invention. It is the B section enlarged view of FIG. It is sectional drawing explaining Example 3 of this invention. It is the C section enlarged view of FIG. It is sectional drawing explaining Example 4 of this invention. It is the D section enlarged view of FIG. It is sectional drawing explaining Example 5 of this invention. It is sectional drawing explaining Example 6 of this invention. It is the E section enlarged view of FIG. It is sectional drawing explaining Example 7 of this invention. It is an enlarged view of the F section of FIG. It is sectional drawing explaining Example 8 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copper plate 2 Alumina ceramic ring 3, 22 BAg-8 silver low 4, 23 Sintered metallization layer of Ti and Cu 5 Silicon nitride ceramic ring 10 Kovar plate 11 Carbon plate 12 Weight 13 Free-cutting ceramic ring 20 Quartz tube 21 Non-oxidized copper tube

Claims (3)

Any one of Ti, TiH or TiH ₂ powders with a particle size of 50 μm or less and Fe, Ni, Cu, Ag, Au, Ta, and W powders. The weight ratio of Ti powder is 10% to 60%. A metal bulk material that is applied to a portion of the ceramic surface to be metallized so as to become the following, and is mixed with Ti at 500 ° C. or higher in a vacuum or in an inert gas atmosphere or an inert gas atmosphere containing hydrogen. A sintered ceramics metallization method characterized by sintering at a temperature lower than the melting point of the sintered ceramics.   2. The method of metallizing sintered ceramics according to claim 1, wherein powders of metallized ceramics having a particle size of 50 μm or less are mixed so as to be 2% to 50% by weight. 3. The sintered ceramics metallization according to claim 1, wherein TiO ₂ is used instead of Ti, TiH, or TiH ₂ powder when the sintering temperature is 900 ° C. or more. Law.

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