JPS586279B2 - Manufacturing method for airtight terminals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing airtight terminals used in compressors such as refrigerators, freezers, and air conditioners.

In this type of airtight terminal, for example, as shown in FIGS. 1 and 2, a lead conductor 12 made of chromium alloy is inserted into a plurality (for example, three) of through holes in a cap-shaped metal outer ring 10 made of iron. are hermetically and insulatively sealed with glass 14.

As shown in FIG. 3, the lead conductor 12 is prepared by performing a pretreatment to clean the surface of the conductor 121 serving as the base, and then heating it in a humid high-temperature hydrogen atmosphere to form an iron-chromium alloy. A chromium oxide layer 16 is deposited and formed on the entire surface of the conductor 121 by performing selective oxidation of chromium.

The reason for using an iron-chromium alloy for the basic conductor 121 here is that the iron-chromium alloy has a coefficient of thermal expansion similar to that of the glass 14 and has high mechanical strength, and the chromium oxide layer 16 is This is because it has extremely good sealing properties with the glass 14.

However, of the chromium oxide layer 16 of the conductor 121, only the chromium oxide layer 161 at the center is useful for sealing the glass 14, and the chromium oxide layers 162 at both ends are unnecessary and are useful for glass sealing. Need to be removed afterwards.

However, since the chromium oxide layer 162 is very stable and firmly adheres to the conductor 121, it is usually removed by mechanical methods such as barrel polishing or homing.
Alternatively, the generated chromium oxide (trivalent Cr) is further oxidized (hexavalent Cr) using an oxidizing agent (e.g. potassium permanganate) in an alkaline solution, and then the normal pickling process (e.g. A chemical method of dissolving in a sulfuric acid bath - hydrochloric acid bath immersion) is employed.

All of these methods not only require a large number of man-hours, but also have the drawbacks of causing cracks in the glass 14, complicating the treatment of the chromium-containing waste liquid generated in the removal process, and increasing the cost of waste liquid treatment.

Therefore, the present applicant separately prints a plating resist film on the central part of an iron-chromium alloy conductor, performs electroless nickel plating on both exposed ends, and forms a nickel plating layer. The plating resist film is dissolved and removed, and chromium in the iron-chromium alloy is selectively oxidized.
A lead conductor is produced in which a chromium oxide layer is formed only on the exposed part of the conductor from which the plating resist film has been removed, that is, the central part, and then this lead conductor is sealed to the metal outer ring via glass. A method for manufacturing airtight terminals was proposed.

In this method, the chromium oxide layer exists only on the surface of the nickel plating layer at the center of the lead conductor, and there is no chromium oxide layer on the surface of the nickel plating layer at both ends. The sealing property for
This is an extremely excellent method because it is as good as the conventional method due to the chromium oxide layer, and eliminates the need to remove the chromium oxide from the exposed portions at both ends of the lead conductor after sealing.

However, before sealing the lead conductor, various processes are required in addition to the selective oxidation process, such as a partial formation process of a plating resist film, a nickel plating process, and a process of removing the plating resist film, making the work complicated. There is a point.

Therefore, it would be advantageous if there was a method that would not require the removal of the chromium oxide layer on the exposed portion of the lead conductor after glass sealing and would be a simpler process.

The main object of the present invention is to maintain the thermal expansion coefficient, mechanical strength, and good sealing properties with glass of the chromium oxide layer of the lead conductor made of iron-chromium alloy without sacrificing any of them.
It is an object of the present invention to provide a method for manufacturing an airtight terminal which does not require removal of a chromium oxide film after sealing and which simplifies pre-sealing treatment of lead conductors.

According to another aspect of the present invention, an improved method for processing the lead conductor is provided in an airtight terminal in which a metal outer ring and a lead conductor are hermetically and electrically insulated sealed via molten glass. be done.

This lead conductor processing method includes the steps of coating a conductor prepared as a base of the lead conductor, at least the surface layer of which is an iron-chromium alloy, with another metal in a thinner film at the center than at both ends; It consists of a step of heating the coated conductor in a predetermined atmosphere and forming a chromium oxide layer in the central part by selective oxidation of chromium deposited from the surface layer of the conductor,
A feature is that a selective chromium oxide layer is formed only in the central portion of the lead conductor.

In the lead conductor obtained through such treatment, the center portion, which has been selectively oxidized in advance, is firmly bonded to the molten glass, and the both end portions, which have not been selectively oxidized, are used as electrical terminals for introduction and extraction, making it easy to manufacture airtight terminals. Make it.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

The present invention is based on the knowledge that when a nickel layer is formed by electroplating on the entire surface of a conductor made of an iron-chromium alloy, the layer is formed thinner than the central part or both ends of the nickel plating layer, and the central part By setting a specific relationship between the thickness of the nickel plating layer and the thickness of the nickel plating layer at both ends, that is, the thickness values and their ratios, and performing selective oxidation treatment under certain conditions, the thin part of the nickel plating layer becomes the thick part. In comparison, there are more pinholes and less rust prevention effect on the underlying conductor made of iron and chromium alloy, so chromium in the conductor made of iron and chromium alloy is selectively oxidized to form chromium oxide, and the above-mentioned Based on the knowledge that chromium oxide is precipitated and formed on the surface of the thin film part of the nickel plating layer for the same reason, chromium oxide layer is not deposited and formed on the surface of the thick film part. The purpose is to form metal layers with different thicknesses on the metal layer and perform selective oxidation treatment under specific conditions such that a chromium oxide layer is formed only on the surface of the thin metal layer.

FIG. 4 shows a longitudinal sectional view of an embodiment of a hermetic terminal for a compressor manufactured by the method of the present invention.

8, 20 is a metal outer ring made of iron and having a hat shape, which includes a cylindrical side wall portion 22, a flange portion 24, a top plate portion 26, and a plurality of metal outer rings ( In the illustrated example, there are three through holes 28 for sealing lead conductors.

One lead conductor 30 is inserted through each of the through holes 28, and is hermetically and electrically insulated sealed with a sealing glass 40 such as soda barium glass or soda lime glass.

FIG. 5 shows a block diagram of each step in the second method of the present invention.

Referring to FIG. 5, the metal outer ring 20 is manufactured by press-molding an iron plate of a certain thickness, and is prepared using an organic solvent such as trichlorethylene (CHCl2-CCI2) or tetrachlorethylene (CCl2-CCl2). Pretreatment is performed to remove oils, fats, chemicals, etc. adhering to the surface.

Furthermore, for surface cleaning and decarbonization, annealing is performed at high temperature in a hydrogen stream.

The metal outer ring 20 is then heated to 600 to 700 in an oxidizing atmosphere furnace.
℃ to form an iron oxide layer on its surface.

This iron oxide layer enables good sealing with the sealing glass 40 in the glass sealing process described later.

Figure 6 shows the lead conductor 3 in each process according to the method of the present invention.
0 is shown in a vertical cross-sectional view.

5. Referring to FIG. 5 and FIG. 6, a long iron-chromium alloy wire, for example No. 1 containing 25 to 28% chromium. 446 iron・
A conductor 31 is manufactured by cutting a chromium alloy wire to a desired length, and after organic cleaning is performed in the same manner as described above, a metal layer that is difficult to oxidize in a hydrogen atmosphere, such as a nickel layer, is formed by electroplating.

According to the electroplating method, a thinner nickel plating layer is formed on the central portion 32 of the conductor 31 than on both end portions 34.

For example, when a conductor 31 with a diameter of 2.3 mm and a length of 32.54 mm is plated for 90 minutes at a current density of IA/dm2 using a barrel in a strongly acidic nickel chloride bath,
The thickness of the nickel plating layer 32 at the center portion is approximately 5 μm, and the thickness of the nickel plating layer 34 at both end portions is approximately 12 μm.

After that, the nickel-plated conductor is subjected to selective oxidation treatment of chromium, and the central portion of the nickel-plated conductor is
That is, the chromium oxide layer 36 is deposited and formed only on the surface of the relatively thin nickel plating layer 32.

The selective oxidation of chromium is carried out by adding water vapor to hydrogen in a high-temperature hydrogen atmosphere furnace, taking advantage of the differences in the equilibrium oxygen partial pressures of the various metal oxides contained in the iron-chromium alloy. The oxygen partial pressure of the system is made higher than the equilibrium oxygen partial pressure of chromium oxide, and the dew point of the atmospheric gas is set to 50°C by controlling the water temperature of the humidifier by electric heating, for example,
℃ or higher for 40 minutes to selectively oxidize the chromium in the iron-chromium alloy and to form the lead conductor 30 until the chromium oxide is precipitated only on the surface of the relatively thin nickel plating layer 32. To manufacture.

Further, referring to FIG. 5, a sealing glass material, for example, soda barium glass, is made into a fine glass powder that passes through a 150 mesh sieve and 1/2 passes through a 350 mesh sieve. Add an organic binder, such as carbowax, stir thoroughly, mix, and granulate.
A cylindrical glass tablet 40 having a predetermined capacity is formed using a press machine.

Thereafter, the glass tablet 40 is heated to a temperature at which the organic binder completely disappears, for example 500°C, and then heated to about 7750°C in the same atmosphere to sinter the glass fine powder.

Next, the metal outer ring 20, the lead conductor 308, and the glass tablet 40 are assembled in predetermined positions using a graphite-based sealing jig (not shown), and heated at 1000° C. for about 10 minutes in a neutral or weakly reducing atmosphere. Heat for a minute.

Then, the glass tablet 40 melts, the chromium oxide layer 36 at the center of each lead conductor 30 gets wet well with the molten glass, and the lead conductor 30 contacts each through hole 28 of the metal outer ring 20 through the molten glass. Hermetically and electrically insulatingly sealed.

Thereafter, this sealed body, ie, the hermetic terminal, is taken out of the sealing furnace and cooled.

Finally, the airtight terminal thus obtained is immersed in a relatively weak acid capable of removing the iron oxide layer of the metal outer ring 20, for example, a 10 to 20% hydrochloric acid solution, and the metal outer ring 20 and The oxide film is removed from the exposed portions of the lead conductors 30, that is, the portions other than the portions sealed by the sealing glass 40.

At this time, there may be no stable chromium oxide layer at all on the relatively thick nickel plating layer 34, 34 that is the exposed portion of the lead conductor 30, or even if there is some chromium oxide layer, the relatively thick nickel plating layer 34. The exposed portion of the lead conductor 30 can be damaged even by a relatively weak acid that can remove the iron oxide layer of the metal outer ring 20 because the quartz oxide layer is very fragile and is deposited through the plating layer 34.34. The chromium oxide layer is completely removed.

Note that after this, a metal layer such as nickel is plated on the exposed portions of the metal outer ring 20 and the lead conductor 30 for the purpose of rust prevention or the like.

Alternatively, terminal plates (not shown) for connecting lead-in shells and lead-out wires may be welded and fixed to both ends of each lead conductor 30, respectively.

In the above embodiment, the conductor 31 made entirely of an iron-chromium alloy is used as the base of the lead conductor 30. However, since the iron-chromium alloy has a relatively low conductivity, the current of the lead conductor 30 is The drawback is that the capacity is small.

Therefore, when a large current capacity is required, as shown in Figure 7, the axial center part is made of a metal with high conductivity, such as copper 302, and the outer periphery is made of a cylindrical shape made of iron-chromium alloy. A lead conductor 300 using a composite conductor 301 made of a copper-core iron/chromium alloy coated with a body 304 may also be used.

3. According to 8 of the present invention, the thickness of the nickel plating layer formed on the conductor 31 or 301 is the same as that of the conductor 31 or 30.
It is appropriate that the ratio of the film thickness to the central portion of 1 is within the range of 1=2 to 1:3, and the appropriate film thickness values are approximately 3 to 8 μm at the center portion and approximately 8 to 15 μm at both end portions.

In such a case, the chrome oxide layer 36 can be easily formed on the surface of the nickel plating layer 32 in the central portion in the subsequent selective oxidation process of chromium, and the nickel plating layer 34 on both end portions can be easily formed. It is possible to avoid forming a chromium oxide layer.

As described above, according to the present invention, a metal layer that is difficult to oxidize in a later selective oxidation process is applied to a conductor whose surface layer is made of an iron-chromium alloy, so that the central portion is thinner than the end portions. The lead conductor thus obtained is sealed with glass by heating in a humid hydrogen atmosphere to precipitate a chromium oxide layer only on the surface of the relatively thin metal layer in the central portion. Therefore, hermetic terminals can be manufactured without sacrificing the various advantages of the iron-chromium alloy, such as its thermal expansion coefficient, mechanical strength, and good sealing properties to sealing glass due to the chromium oxide layer.

Moreover, since there is no or substantially no chromium oxide layer in the glass-sealed portion of the lead conductor, there is no need to remove the chromium oxide layer after hermetically sealing the terminal.
It can be easily removed in the process of removing the iron oxide layer on the metal outer ring, and it contains no or substantially no chromium, which is a source of pollution in wastewater, so there is no chromium pollution and wastewater treatment is extremely easy. This effect is achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an example of an airtight terminal for a compressor, which is the background of the present invention. FIG. 2 is a longitudinal sectional view taken along line 1-1 in FIG. 1. FIG. 3 is a longitudinal sectional view of the lead conductor of each culm in the conventional manufacturing method of the airtight terminal shown in FIG. FIG. 4 is a longitudinal sectional view of an embodiment of a hermetic terminal for a compressor manufactured by the method of the present invention. FIG. 5 is a block diagram showing each step in the method of the present invention. FIG. 6 is a longitudinal sectional view of a lead conductor at each step in the method of the present invention. FIG. 7 is an enlarged longitudinal cross-sectional view of a main part of another example of a lead conductor that can be used in the present invention. 20...Metal outer ring, 30,300...
Lead conductor, 31, 301... Conductor, 32.
...Relatively thin nickel plating layer in the center, 3
4,306...Relatively thick nickel plating layer at both ends, 36...Chromium oxide layer, 40...
...Sealing glass, 302...Copper, 304...
...A cylindrical body made of iron and chromium alloy.

Claims (1)

[Scope of Claims] 1. A step of preparing a conductor at least whose surface layer is made of an iron-chromium alloy, and applying a metal layer on the surface of the conductor that is different from the surface layer of the conductor so that the center portion thereof is thinner than both end portions. a selective oxidation treatment step of heating the metal-coated conductor in a predetermined atmosphere to deposit and form a chromium oxide layer only on the surface of the metal layer in the central portion; a step of assembling the lead conductor, the metal outer ring on which the oxide film is formed, and the sintered glass tablet in a predetermined relationship using a sealing jig; and heating the assembly in a neutral or weakly reducing atmosphere. and melting the sintered glass tablet and sealing the lead conductor to the metal outer ring through the glass in an airtight and electrically insulating manner. 2. Claim 1, wherein the metal layer is a nickel layer.
2. Method for manufacturing airtight terminals as described in Section 1. 3 The thickness ratio between the central portion and both end portions of the metal layer is 1.
The method for manufacturing an airtight terminal according to claim 1 or 2, wherein the ratio is within the range of :2 to 1:3. 4. Manufacture of an airtight terminal according to any one of claims 1 to 3, wherein the thickness of the metal layer is within the range of 3 to 8 μ at the center and 8 to 15 μ at both ends. Method. 5. The method of manufacturing an airtight terminal according to any one of claims 1 to 4, wherein the metal layer is formed by electroplating. 6. The airtight device according to any one of claims 1 to 5, wherein the atmosphere in the selective oxidation step is a hydrogen stream containing water vapor, and the oxygen partial pressure thereof is equal to or higher than the equilibrium oxidation partial pressure of chromium oxide. Terminal manufacturing method. 7. The selective oxidation step is performed at a temperature of 1000° C. or higher for a sufficient time to precipitate and form a chromium oxide layer only on the surface of the relatively thin metal layer in the central portion of the conductor. A method for manufacturing an airtight terminal according to any one of Items 1 to 6. 8. The method of manufacturing an airtight terminal according to any one of claims 1 to 7, wherein the conductor is entirely made of an iron-chromium alloy mainly composed of iron. 9. The conductor has a center portion made of a highly conductive metal, and a periphery thereof covered with an iron-chromium alloy mainly composed of iron. A method for manufacturing airtight terminals. 10. The method of manufacturing an airtight terminal according to claim 9, wherein the highly conductive metal in the center is copper.