JP2695951B2 - Manufacturing method of vacuum airtight device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for manufacturing a vacuum-tight device, and more particularly to an improvement in a brazing structure.

(Prior Art) As is well known, a bonding material conventionally used for bonding a plurality of components has been required to have excellent workability and high bonding strength.

For example, a semiconductor manufacturing apparatus, an image pickup tube, a magnetron, a vacuum valve, and the like have an internal pressure 10
^It consists of a vacuum container of ^-4 Torr or less and highly cleaned members. That is, for example, since the inner surface of the device provided with the above-mentioned vacuum-sealed attachment portion needs to limit unnecessary deposits, the manufacturing process and the selection of members are highly controlled.

Conventionally, silver brazing materials used for brazing such vacuum-tight devices include 72Ag-Cu, 65Ag-15Pd-Cu, 6
4.8Ag-10Sn-Cu or the like is used, and is heated to a predetermined temperature (for example, about 800 ° C.) in a vacuum or hydrogen to perform brazing. The reason is that since these brazing materials do not contain elements having a particularly high vapor pressure, such as Zn, Cd, and Pb, the function as a brazed vacuum hermetic device can be maintained for a long time. .

That is, an element having a high vapor pressure easily becomes a vapor state, penetrates and adheres to minute gaps in the internal space of the vacuum hermetic apparatus, and as a result, becomes a supply source of dust in a semiconductor manufacturing apparatus, and In a tube, the resolution is reduced, in a magnetron, the oscillation of the microwave power is poor, and in a vacuum valve, the pressure resistance is poor.

By the way, from the viewpoint of hermetic sealing function, the vacuum valve is the most severe among various vacuum hermetic devices.

That is, the vacuum valve houses a contact that reaches the arc temperature inside, and the contact is frequently exposed to the arc.
Makes a large number of switching movements, and the opening and closing are accompanied by thermal and mechanical shocks; high voltage is applied between contacts where large currents flow; withstand voltage is required at the time of disconnection; low contact resistance This is because the contact surface must always be clean without foreign matter adhered in order to maintain the condition.

By the way, the vacuum valve is provided with a pair of contactable and detachable contacts opposed to each other in a vacuum vessel having an internal pressure of 10 ⁻⁴ Torr or less, and one of the contacts is provided with a fixed variable current-carrying shaft serving as an electric path. Is air-tightly guided to the outside, the other contact is provided with a movable variable conduction shaft serving as an electric furnace, and is attached to the other end plate via a bellows, and the contact is opened and closed in a vacuum state.

The main materials constituting the vacuum valve are alumina porcelain for the insulating container, copper for the current-carrying shaft, stainless steel for the bellows, and Kovar (Fe-Co- (Ni alloy) is used (alumina porcelain, copper, stainless steel, and Kovar are also used as materials for vacuum-tight containers other than vacuum valves).

Moreover, most of these components are mounted by silver brazing.

(Problems to be Solved by the Invention) As described above, the hermetic structure of the vacuum hermetic device is based on adhesion by silver brazing. Therefore, depending on the type of the silver brazing material used and the leakage between the members to be joined, etc. There is a possibility that the properties and strength will be reduced and the long-term function maintenance / life will be impaired.

For example, some brazing materials include phosphor copper brazing (JIS-Z-3
264), for example, 4.8-5.3% P-Cu (JIS symbol B CuP
-1), 6.8-7.7% P, 4.7-6.3% Ag-Cu (B CuP-4)
However, there are some which contain a large amount (5 to 8% by weight) of P as described above, and these are used for sealing a vacuum hermetic device which is symmetrical in the present invention. It cannot be used for long-term reliability maintenance due to contamination and weakening of internal P.

For example, if gas is released during brazing, metal particles and a large amount of metal vapor are also released in the same manner as the release, and penetrate and adhere to the inner surface and minute gaps of the vacuum-tight device.

Then, in the vacuum hermetic device, the electric field concentration of the adhered metal vapor on the metal particles not only causes a failure in pressure resistance, but also causes the condensed brazing material after discharge to locally include holes or surfaces to be joined. The non-wetting portion of the brazing material remains, and the bonding strength is reduced, which causes airtight leakage.

Therefore, an object of the present invention is to provide a method for manufacturing a highly reliable vacuum hermetic device capable of maintaining vacuum hermeticity and withstand voltage characteristics for a long period of time.

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a method for manufacturing a vacuum-tight device for joining a plurality of components by brazing, wherein 1 to 1
300 ppm boron, 1-15 ppm oxygen, 1-15 ppm nitrogen, 50
-99% by weight of silver, the balance being copper, and adding a silver solder of an alloy, and joining the components by brazing at a heating temperature not lower than the melting temperature of the alloy and not higher than 950 ° C. in a vacuum or hydrogen atmosphere. This is a method for manufacturing a vacuum airtight device.

(Function) Unlike the conventional brazing method using Ag-Cu, Ag-Pd-Cu, and Ag-Sn-Cu alloys, the number of particles adhered to the airtight interior is reduced, and not only properties such as electric withstand value are improved, but also The wettability between joints and the joint strength are increased, and high airtightness can be maintained for a long period of time.

That is, the point of the present invention is the composition and temperature of the brazing filler metal used. The composition is B (boron)
By controlling the presence of O (oxygen) and N (nitrogen),
It is possible to reduce the outgassing that is suddenly released at the moment when the brazing material melts during joining.

That is, when the amount of B is 1 to 300 ppm (0.001 to 0.03% by weight), by controlling other O and N in a predetermined range, the contamination as in the conventional case (that is, containing high vapor pressure components No), the embrittlement is eliminated, the management of O and N amounts within a predetermined range becomes easy, a stable brazing material can be obtained, and the withstand voltage characteristics and the like increase. If Ag, Cu or the like contains a high vapor pressure component such as P, it is not preferable as a brazing filler metal for a vacuum hermetic device. The present invention not only joins the hermetically sealed portion, but also applies
Since brazing material with controlled O and N is used, it is effective not only to suppress scattering and evaporation of high vapor pressure components during heating for adhesion, but also as a measure against heat generation by energizing when applying electricity to members .

Further, in the present invention, the brazing heating temperature is set to 950 ° C. or less. This is because when a bellows made of stainless steel is used for a vacuum hermetic device, it takes into account problems such as a reduction in vacuum hermeticity due to crystal coarsening due to heating at 950 ° C or more and a decrease in the fatigue life of the bellows, In order to equalize the obstacles due to the evaporation of Ag and the coefficient of thermal expansion, and to suppress the amount of brazing material entering the crystal grain boundaries of the Kovar material used in the vacuum sealing device, a material having a temperature of less than 950 ° C is selected.

(Example) Hereinafter, an example of the present invention will be described. First, the table shows a comparison between the composition of the silver brazing material, the joining conditions, and a few evaluation results when the method for manufacturing a vacuum-tight device of the present invention is applied to a vacuum valve. The assembly of the vacuum valve and the evaluation conditions are as follows.

Here, the vacuum valve used for the evaluation has a configuration as shown in the figure. That is, in FIG.
Means that both ends of a cylindrical insulating container 2 made of alumina porcelain are hermetically closed by end plates 3a and 3b made of Kovar material (Fe-NiCo alloy) having a thermal expansion coefficient close to that of alumina porcelain, and the internal pressure is reduced to 10 ^-4. Tor
r, a pair of electrodes 4a, 4b
Is installed.

A fixed-side conducting shaft 5a made of a copper material is attached to one of the electrodes 4a, penetrates one end plate in an airtight manner, and leads to the outside to form an electric circuit.

A movable-side conducting shaft 5b serving as an electric path is attached to the other electrode 4b, and the end plate is connected via a bellows 6 made of stainless steel.
The electrodes 4a and 4b are attached to and detachable from each other in a vacuum-tight state.

A cylindrical arc shield 7 is disposed around the electrodes 4a and 4b to prevent the inner wall surface of the insulating container 2 from being stained by metal vapor coming out of the electrodes 4a and 4b when current is interrupted.

The vacuum valve having this configuration was assembled as follows. That is, the electrode 4b and the conducting shaft 5b, and the electrode 4a and the conducting shaft 5a
Are previously joined with a brazing material having a higher melting temperature than the silver brazing material used for joining the hermetically sealed portions, for example, 5% Pd-Ag, and these joined members are composed of end plates 3a, 3b and insulating container 2. After each of the silver brazing materials shown in the same table was added between the end plate 3a and the insulating container 2 and between the end plate 3b and the insulating container 2 in the vacuum-tight container, the other bellows 6 While being heated in a vacuum together with, for example, it was hermetically sealed at the temperature shown in the same table.

The vacuum valve thus obtained was subjected to a withstand voltage test as an electrical evaluation, a leak test as an airtightness evaluation, and a strength test as an evaluation of the bonding strength of a bonding portion under the methods and conditions described below.

The evaluation of the hermetically sealed portion is based on the relative amount of gas remaining inside due to the magnitude of the discharge current when a predetermined voltage is applied to both ends of the vacuum valve immediately after assembling and bonding heat treatment as described above. I asked.

In addition, the compulsory evaluation of the joining strength is based on a 2 m
After applying a shock load by dropping a metal lump of 100 kg from the height of, the same discharge current as described above was obtained.

The bonding strength was directly 7 mm, 50 mm long copper material facing up and down in the axial direction, sandwiching the electrode manufactured in the specified shape and the silver brazing material shown in the table between them, under the bonding conditions shown in the table. Brazed. Then, the joining strength was measured with a tensile tester. In the same table, the results are shown as relative values with the value of Example 2 set to 1.0.

Further, with respect to the withstand voltage characteristics, the vacuum valve obtained as described above was cut off 100 times at the upper limit of the voltage of 84 kV, 50 Hz, and the cutoff current of 12 kA, and the recurrence occurrence probability was examined for three vacuum valves. Note that a Cu-Cr contact was bonded to the electrode material.

Examples 1-3, Comparative Examples 1-3 72% Ag-dissolved in an atmosphere with a degree of vacuum of ^10-4 to ^10-5 Torr.
A predetermined amount of a 2% B-Cu master alloy was put into a molten Cu alloy to produce a silver brazing material containing predetermined amounts of B, O, and N. The amounts of B, O, and N were changed by controlling the degree of vacuum, melting time, and melting temperature during melting, and the numerical values were confirmed by analysis. About 200μ
m, and sandwiched between an insulating container made of Al ₂ O ₃ porcelain and an end plate made of Kovar, which had been Ni metallized in advance and 810 ° C. × 30 in a vacuum of 4 × 10 ^-5 Torr. A vacuum sealing process was performed for a minute.

As a result, as shown in the table, the amount of B in the brazing silver was
In the case of 300 ppm or less (Examples 1 to 3), the airtightness, the bonding strength, and the probability of occurrence of re-sticking were all within the preferred ranges, but when the amount of B was 2420 ppm (Comparative Example 3), the hermetic sealing was performed. A small defect occurred in the part, the trouble increased after the impact test, and re-burning occurred frequently. On the other hand, when the amount of O in the silver brazing material was 75 ppm or 35 ppm, the re-lighting increased. In particular, when the amount of residual B in the silver brazing material is small (Comparative Example 1), the amount of O cannot be reduced sufficiently, re-incision increases, and the strength varies, which is not preferable. When the vacuum valve of Comparative Example 1 was disassembled after the evaluation of re-ignition characteristics, a granular brazing material (about 0.1 mm in diameter) was adhered to a part of the inner surface of the vacuum valve. It is desirable to avoid these as much as possible because they cause re-incarnation. Such adhesion of the brazing material is not observed in Examples 1 to 3 and Comparative Example 3 where the O amount is small, and it is considered that there is a relationship with the O amount.

Therefore, in the brazing silver material, it is necessary to control the amount of B and the amount of O in the same manner, and the amount of B must be 1 to 300 ppm, and the amount of O at that time must be 15 ppm or less. Examples 1-3,
Comparative examples 1 to 3).

Examples 4 to 7 and Comparative Example 4 The evaluation as shown in the table was performed on 72% Ag-Cu manufactured in the same manner as described above. Although the amount was small, cracks were observed in the brazing layer after the impact test, and re-burning occurred (Comparative Example 4), although the amount was small, but the N content was 15 ppm.
In the following (Examples 4 to 7), there was no problem. Therefore,
It is necessary to control the amount of N in the silver solder in the same manner as described above, and the amount is limited to 15 ppm (Examples 5 and 7).

Examples 8 to 17 and Comparative Examples 5 to 8 In Examples 1 to 7 described above, the amount of Ag in silver brazing was reduced to about 72%.
However, it is beneficial to control the amounts of B, O, and N at the same time even if the amount of Ag is 99% (Example 8) or 50% (Example 9). However, when the amount of Ag is 25% (Comparative Example 5), from the viewpoint of manufacturing a vacuum hermetic device, which is the gist of the present invention, a portion where the bonding portion is separated into two layers (uneven composition) is seen. Removed.

The silver brazing material used in the production of such a vacuum hermetic device can be made of Ag-Cu-Pd (Examples 10 to 12) in addition to the above-mentioned Ag-Cu by controlling the B, O, and N amounts described above. Adoption is beneficial. Also in this system, when the B content in the alloy is 1020 ppm (Comparative row 6), the O content is 85 ppm (Comparative example 7), and the N content is 65 ppm (Comparative example 8), the same tendency as described above is obtained. Leakage and re-arcing of the sealing portion frequently occur, which is not preferable.

Similarly, if the amounts of B, O and N are controlled, Ag-Cu-Sn, Ag-Cu-Sn
It is possible to manufacture a vacuum valve employing -Ni, Ag-Cu-Sn-In, Ag-Ni, Ag-Cu-In (Examples 13 to 17).

Example 18 The above-described Examples 1 to 17 and Comparative Examples 1 to 8 were all applied to the vacuum-sealed attachment portion, but the application of silver brazing in which B, O, and N were controlled was applied to a vacuum-tight device. The joining of the internal members is equally beneficial in reducing contamination inside the vacuum tight container.
Further, the bonding at such a portion can be performed in a hydrogen atmosphere (Example 18). When the silver brazing material used in Example 2 is applied to the bonding between the current-carrying shaft and the electrodes, re-burning occurs. I couldn't find any.

Note that Ni may be added to the silver brazing material. But Ni
Because the melting temperature of the brazing material rises significantly with the addition of a small amount,
Care must be taken that the temperature does not exceed 950 ° C.

[Effects of the Invention] As described above, according to the present invention, in the method of manufacturing a vacuum-tight device for joining a plurality of components by brazing, the contents of B, O, and N are controlled in a predetermined range. Using a silver solder, the components were joined by heating to above the melting temperature of the silver solder and below 950 ° C, and the release of gas during the melting of the silver solder was suppressed. It is possible to obtain a vacuum-tight device that is excellent and has a long life.

[Brief description of the drawings]

The figure is a longitudinal sectional view showing an application example of the manufacturing method of the vacuum airtight device of the present invention. 1 ... Vacuum valve, 2 ... Insulating container 3a, 3b ... End plate, 4a, 4b ... Electrode 5a, 5b ... Electrical shaft 6 ... Bellows

Claims (1)

(57) [Claims] 1. A method for manufacturing a vacuum-tight device for joining a plurality of components by brazing, wherein a bonding portion of the components has 1 to 300 ppm of boron, 1 to 500 ppm of oxygen, 1 to 15 ppm of nitrogen, 50 to 50 ppm of nitrogen. Adding 99% by weight of silver and silver braze of an alloy consisting of copper and joining the components by brazing in a vacuum or hydrogen atmosphere at a heating temperature not lower than the melting temperature of the alloy and not higher than 950 ° C. A method for manufacturing a vacuum tight device.