JPH02252682A - Metallization of ceramic and bonding of ceramic - Google Patents

Abstract

PURPOSE:To provide the title metallization intended for improving vacuum sealability by heating and baking in a vacuum or an inert gas atmosphere a ceramic coated with a specific paste followed by baking in a mixed atmosphere containing oxygen. CONSTITUTION:Active metal composition powder comprising Ag, Cu and Ti is incorporated with (A) 1-25wt.% of at least two metals selected from Al, Si, Pb, Ba, Zn, Bi, Cd and Tl, (B) an organic binder and (C) an oil to prepare a paste. Thence, the surface of a ceramic is either coated with this paste, or a ceramic and a second ceramic or the former ceramic and a metal plate are brought to mutual contact through said paste, followed by heating and baking in a vacuum or an inert gas atmosphere at temperatures not lower than the eutectic point of the active metal (800-900 deg.C) and then further baking in a 10-1000ppm oxygen contg. mixed atmosphere of N2, He or Ar at temperatures >=500 deg.C but not higher than the above baking temperature for 5-60min.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a ceramic metallization method and a joining method, and in particular, it is used to closely and firmly bond ceramics and ceramics, and ceramics and metals in equipment that requires vacuum sealability. This relates to metallizing and bonding methods for bonding.

(Prior art) When conventionally bonding ceramics to ceramics or ceramics to metals, a paste consisting of a metal and an organic solvent in which several percent of T1 is added to an Ag and Cu alloy is printed, and this is applied in a vacuum. The so-called active metal method, in which bonding is performed while holding the metal at a predetermined temperature (1-), is often used. However, this method has a drawback that the vacuum sealability of the interface is poor, and this method cannot be applied when the inside of the bonded parts is kept in a vacuum.

On the other hand, when joining parts that require vacuum sealability, a special joining method called the Mo-Mn method or the high melting point metal method is generally used. However, this method requires very complicated steps. That is, as a general method, a paste consisting of Mo, Mn, and an organic solvent is first printed on the surface of the ceramic, and then it is exposed to N at a temperature of 1400°C or higher.
After being held in a mixed atmosphere of 2 and N2 and metalized, Nl plating is performed. Furthermore, in order to stably fix Nl, sintering is performed in vacuum at 900°C. Next, in order to bond the metallized ceramic to metal, a brazing material is applied to the metallized surface, and brazing is performed by holding this at 800° C. in H2.

As described above, the active metal method does not satisfy the property of vacuum sealability, and the Mo-Mn method has problems such as a very long process and a high metallization temperature.

(Problems to be Solved by the Invention) The present invention provides a simpler method for joining ceramics-ceramics or ceramics-metal, which requires vacuum sealability, in devices such as vacuum switches and microwave ovens. By adopting a simple process that improves the active metal method described above, M
The object of the present invention is to provide a metallizing method and a joining method thereof that have performance equivalent to or better than the sealing property obtained by the o-Mn method.

(Means for Solving the Problems) The present invention provides active metal composition powder consisting of sAg*Cu, Tl, etc., with Ap, Sl, Pb, Ba, Zn.
.

A paste formed by adding at least two metals of Bi, Cd and Tfl, an organic binder and oil is applied to the ceramic surface, and then heated and heated in a vacuum or an inert gas atmosphere. After firing and cooling or in subsequent steps, nitrogen (N2), helium (He) or argon (Ar) containing 10 to 11000 pp of oxygen is added.
Metallizing by firing in a range from 500 ° C. or higher to the firing temperature or lower in an atmosphere of alone or in a mixture of
The paste is interposed between ceramics and ceramics or metals, and the ceramics and ceramics or metals are brought into contact with each other, and then the two-stage process described above is performed to join the ceramics and ceramics or the ceramics and metals. The gist of this is that

The present invention will be explained in detail below.

The active metal method conventionally used for joining ceramics and metals uses Ti and Zr, which are metals active against oxygen.
This is a bonding method that utilizes the reaction at the interface between , V, Nb, etc., and ceramics. However, at the bonding interface formed by this method, there are microscopic gaps through which gas passes.

This is hardly applicable to members that require vacuum sealability.

In other words, if we look at the amount of helium leak, for example, I
There are very few cases where it is possible to maintain LO-3 torrfI/sec or less. The present inventors focused on the micro gap,
As a method that does not mold this gap, we investigated a method in which glass powder that melts at the bonding temperature is added to the active metal and the gap is filled with glass. However, with this method, it was not possible to obtain a satisfactory bonding strength, and even if the firing temperature and the mixing ratio were changed, a satisfactory bonding strength could not be obtained. It was found that this was caused by the glass powder being reduced by active metals such as T1.

Therefore, the present inventors separated the period in which the active metal reacts and the period in which the glass fills the gap, held the active metal in a state in which it was not reduced to Ti in the reaction process, and then performed the gap filling process. It was found that by controlling the atmosphere to form a glass, a joint having high vacuum sealing properties comparable to the Mo-Mn method could be obtained, and the present invention was completed.

The ceramics targeted by the present invention may be oxide-based, nitride-based, or any other conventionally used ceramics. The active metal used as the bonding material is Ag-Cu-Ti powder (for example, Ag: 70vt%, Cu: 28vt%).
vL%, Ti:2wt,%), which is also commonly used in the active metal method, and there are no particular limitations regarding this. In the present invention, this active metal powder contains Al, Sl, and -Pb.

At least two of Ba, Zr, Bi, Cd and Tfl
Add seed metal. When these metals are vitrified, the glass concentration in the bonding material is 1 to 15%, preferably 3 to 5%.
Blend so that it becomes 26. The reason why two or more oxides are selected is that even if the oxide alone has a relatively high melting point, by blending two or more of them, the melting point can be lowered.

Examples of these two or more glass compositions and their melting points are as follows.

Glass composition (wt% in parentheses) Melting point Pb0 (8
3)-B203(25)-8in2(12) 60
0'CPb0(83)-8203(17)
555℃ Zn0 (83) B203 (37)
730"C, that is, in the present invention, it is preferable to employ a vitrification temperature of 800"C or less, although this varies somewhat depending on the combination of ingredients.

In the present invention, the paste is applied or interposed on the ceramic surface or between the ceramics or the ceramics or metals by mixing the powders of the active metal and vitrified metal described above, and adding an organic binder (for example, N) to the paste. Terpineol) and oil (for example ethyl cellulose) are added to form a paste, which is applied to the ceramic surface by a method known per se, such as screen printing, brushing or spraying. Afterwards, the ceramics coated with the paste are
Alternatively, after abutting and fixing another ceramic or metal to the ceramic using a jig or the like, these are placed in a vacuum firing furnace as a first stage treatment, and the paste is subjected to ceramic melting and joining treatment.

In this case, the firing temperature may be any higher than the eutectic point of the active metal, and is usually in the range of 800 to 900°C. In the present invention, the firing atmosphere is not limited to vacuum, and may be an inert gas. For example, a high purity Ar gas atmosphere (02≦1 ppm
), it becomes possible to continue to the next step of vitrification treatment.

The ceramics that have undergone the firing process are fired in a second stage treatment using an atmosphere of Ar=He and N2 gas alone or in a mixed atmosphere, and the greatest feature of the present invention is this firing treatment. That is, 10 to 11,000 pp of oxygen is contained in the gas atmosphere, and the treatment is performed for 5 to 60 minutes at a temperature lower than the firing temperature in the first stage treatment and in a temperature range of 500° C. or higher. Micro-gaps exist in the metallized surface or joint surface that has been subjected to the first-stage treatment as described above, but the added metals such as Si and PB are vitrified by the second-stage treatment to fill these gaps. oxygen to lO
~1000pp■ What is mixed in the atmospheric gas is Sl
This is because metals such as Pb react with oxygen and are necessary for glass formation. If the oxygen content is less than 10 ppm, the ceramic will not be bonded to other ceramics or metals, or the bond will be incomplete, and if the oxygen content is more than io00 ppm, the active metal will be oxidized and embrittlement will occur. Further, the reason why the firing temperature is set to 500° C. or higher is that if the firing temperature is lower than that, vitrification is insufficient and sufficient bonding strength cannot be obtained.

In addition, if fired at a temperature higher than the firing temperature of the first stage, it is inconvenient that the brazing material will melt.
The temperature shall be below ℃.

In the present invention, the above range was determined based on the following experimental results.

Height 1 made of A1120392% as ceramics
0mm, [7 A pipe with a diameter of 20mm was used, and active metals such as Ag 70vt%, Cu28vL%, Ti
Pb+B as a glass forming metal in powder consisting of 2wt%
Mix these powders and make a paste with a binder (ethyl cellulose and terpineol) and apply it to both ends of the vibrator, one end to the Kovar metal fitting with a bottom, and the other end to the copper vibrator according to the following requirements. It was joined with

As the first stage treatment, firing was performed in an atmosphere of N2 at a temperature of 850° C. for 80 minutes. After that, as a second stage treatment, the oxygen concentration was adjusted to 120 ppm in a N2 atmosphere as shown in Table 1. Temperature 750
°C x 20 minutes variable - In the second stage treatment in Table 2,
When the base atmosphere is N2 and the oxygen concentration is changed (75
Table 1 shows the bonding conditions under conditions of 0°C x 20 minutes, and when the atmospheric concentration - was changed (oxygen concentration 120 ppm +
) are shown in Table 2.

Table 1 The above sample was placed in a He atmosphere, the open upper end of the copper vibe was joined to a He leak detector, and H
The leakage of e-gas was measured.

Those with good evaluation in the table are lO″″” torrI/
sec, and the vacuum sealability was perfect. Other than that, there were many leaks. From the above results, the second stage treatment conditions of the present invention were clarified.

In the present invention, the processing atmosphere in the first stage is not limited to vacuum, but when the first stage and the second stage are processed consecutively, the same type of gas as the atmosphere in the second stage is used. It is preferable for the work.

In this case, the atmosphere in the first stage must be of high purity, that is, the oxygen concentration must be 1 ppm or less.

(Example) A ceramic (Ag203) cylinder 1 with a diameter of 20 mm,
A box-shaped joined body as shown in the attached figure was set using members made of Kovar 2 and Copper 3 as metals.

At both ends of the ceramic, terpineol (organic binder) and ethyl cellulose (
A paste 4 made by adding oil) was applied by screen printing, and the metal was fixed with a jig.

Active metal powder (Ag: 88vt%, Cu: 30%, Ti: 2%)
80% glass forming metal powder (Si: 30vt%, Pb: 40%, B: 30%
) was used to bond ceramics and each metal under the conditions shown in Table 3.

Table 3 Metallizing conditions Example 2 After metalizing the ceramic surface under the conditions of Example 1, insert a brazing filler metal (BAg-8) between the metallized surface 3 and each of Kovar 2 and Copper 3 using a jig. After these were fixed, brazing was performed at 800° C. for 10 minutes in a vacuum (10-6 torr).

The bonded members treated in Examples 1 and 2 were subjected to a vacuum sealing test and a tensile test. All vacuum sealing degree 10-”t
orrg/sees tensile strength of 300 kg f or more was obtained, confirming that it can be used satisfactorily for vacuum equipment such as vacuum switches.

(Effects) As described above, the present invention provides ceramic-ceramic or ceramic-metal bonding that achieves excellent vacuum sealing properties as possible with the Mn-Mo method using a simple process that improves the active metal method. It is extremely useful industrially.

[Brief explanation of drawings]

The drawing shows a cross section of a test material according to an example of the present invention. Sub-agent Patent Attorney ± IE Hiroaki Mura

Claims (1)

[Claims] 1. In active metal composition powder consisting of Ag, Cu, and Ti, A
A paste formed by adding two or more metals selected from L, Si, Pb, Ba, Zn, Bi, Cd, and Tl, an organic binder and oil is applied to the ceramic surface, and then heated in a vacuum. Alternatively, the method is characterized by heating and firing in an inert gas atmosphere, and further firing in a nitrogen, helium, or argon atmosphere containing 10 to 1000 ppm of oxygen, alone or in a mixed atmosphere, in a range of 500°C or higher and below the heating and firing temperature. Ceramics metallization method. 2.A to active metal composition powder consisting of Ag, Cu, and Ti
A paste formed by adding two or more metals from L, Si, Pb, Ba, Zn, Bi, Cd, and Tl, and an organic binder and oil is placed between ceramics or metals. Ceramics and ceramics or metals are brought into contact with each other, and then heated and fired in a vacuum or in an inert gas atmosphere.
A method for joining ceramics, characterized in that firing is carried out in an atmosphere of nitrogen, helium, or argon containing 0 to 1000 ppm, alone or in a mixture, in a range of 500° C. or more to the heating firing temperature or less.