JPH0113177B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field of the Invention The present invention relates to a method for manufacturing a reed switch in which reed pieces made of magnetic material are enclosed in a glass tube from both ends, and contacts are opened and closed at mutually overlapping portions of the reed pieces. (b) Background of the technology As shown in Figure 1A, a typical reed switch has a pair of reed pieces 2',
3' is inserted and sealed in an inert gas atmosphere. When the excitation coil 4 placed outside the glass tube 1 is energized, both lead pieces 2',
The magnetic flux passing through 3' closes the gap 5 at the overlapping contact portion of the reed piece and turns on the switch. Next, when the excitation coil 4 is made conductive, the magnetic attraction force of the contact gap 5 disappears, the contact gap 5 opens, and the switch is turned off. The contact portion at the inner end of the lead piece is a contact point 6' made of a noble metal material at the tip of the lead piece 3', 2' as shown in FIG.
is provided to reduce the contact resistance. As the magnetic material for the reed piece, permalloy, especially an alloy of 52% nickel and 48% iron called 52 alloy, is widely used. Contact materials include gold, silver, rhodium, copper, or gold-based alloys (Au-
Materials such as Co, Au-Ni) are used. (c) Prior art and its problems However, when a soft material such as gold or silver is used as a contact material, the excitation coil 4 is de-energized and the excitation magnetic field is turned off due to the adhesion phenomenon between the contact materials. Even if removed, the contact gap 5 tends to remain closed. To prevent this, after plating the contact material on the lead piece, heat treatment is performed for about 20 minutes in an electric furnace in a hydrogen atmosphere to diffuse the base metal and contact material, so that the base metal is uniformly coated on the surface of the contact. I try to separate the parts. However, although this method reduces adhesion to some extent, it has the following drawbacks. (1) Due to the Fe in permalloy, the surface of the contact is easily oxidized and the contact resistance is likely to become unstable. That is,
Since a Fe-Ni oxide film is formed and iron and oxygen coexist, the boundary resistance (film resistance) increases, resulting in a higher level of contact resistance than rhodium (Rh) contacts. (2) Due to the small amount of residual oxygen in the glass tube of the reed switch, an oxide film is formed due to the collision energy when the contact closes during no-load operation, and increases with the number of operations. In other words, as the number of operations increases, bridge wear, or pips and craters, occur, causing contact failures such as increased contact resistance and sticking. The reason is that when current flows between closed contacts, the temperature rises due to Joule heat, softening the contact surface and reducing viscosity. Moreover, since the positive side becomes hotter than the negative side, the softened contact material on the positive side sticks to the cold negative side contact, causing bridge wear on the positive side and creating a depression.
In addition, ions generated on the negative side by shot arc during energization collide with the positive side contact surface, and the powder generated at that time is deposited on the negative side contact surface, further promoting depressions and protrusions. If the protuberance fits into this recess, it becomes locked and adheres, making it difficult to separate the contacts when the excitation magnetic field is removed. These phenomena are especially noticeable at 50V and 100m.
It is likely to occur in the area of A level. In addition to this method of diffusion treatment, by mixing approximately 3% Co into the gold plating solution and performing alloy plating, 3% Co will be added to the gold surface of the contact material.
So-called hard gold mixed with Co is obtained, and the adhesion resistance is improved. Moreover, the contact surface is easily oxidized.
Since Fe does not appear, the contact resistance is also improved compared to the case where diffusion treatment is performed between the 52 alloy and the gold plating. However, unlike the diffusion-treated contacts, the bond between the alloy-plated contacts and the underlying 52 alloy is weak, and the contacts tend to peel off due to repeated temperature changes. In particular, the electrical resistivity of 52 alloy is as high as 35 μΩ·cm, so the current passing through the contacts generates a large amount of heat and is subjected to high temperature cycles, making it even more likely to peel off. In order to solve this problem, the applicant of the present invention proposed an Fe (10-18%)-Co (remainder) alloy as a lead piece material in which the base itself contains a large amount of Co. Since this magnetic material contains 82 to 90% Co, if it is gold-plated as a contact material and then subjected to diffusion treatment, Fe, which is easily oxidized, will not precipitate.
Since Co precipitates, it does not oxidize and increase the contact resistance, and the adhesion between the contact material and the lead piece also improves. However, when Fe (10-18%) - Co (remainder) alloy is used, another problem is that if the deburring performed before the plating process is done by electrolytic polishing, the contact material and lead piece The adhesion of the product deteriorates, and the desired effect cannot be obtained. That is, as shown in FIG. 2, the lead piece is formed into a plate by flattening a part of the round bar 7 with a press, and a contact point is provided at the tip of this plate-shaped part 71. Burr generated 7
If 2 or burrs remain on the tip of the lead piece, it will interfere with the opening/closing operation of the contact, reducing the reliability of the contact operation. In order to remove this burr, there is a barrel polishing method in which the burr is stirred together with an abrasive, but this method may cause the reed piece itself to be deformed. Furthermore, during barrel polishing, the reed pieces are broken up and mixed with the abrasive material, making it difficult to handle during the transition from barrel polishing to the plating process, resulting in poor workability. On the other hand, the electrolytic polishing method requires only immersion in an electrolytic solution, so the reed pieces do not collide with each other and deform, unlike barrel polishing that uses mechanical stirring, and can be held in a constant state. It is easy to handle and has excellent workability when moving on to the next plating process. By the way, when electropolishing 52 alloy, the phosphoric acid concentration is
A 50-70% phosphoric acid solution (H ₃ PO ₄ ) is used as an electrolytic polishing solution, but a similar phosphoric acid solution with 20% Fe
When the following Fe (10-18%)-Co (remainder) alloy is electrolytically polished, the polished surface tends to be rough and electrolytic pits, that is, minute depressions, are likely to occur. Therefore, even if a Fe (10-18%)-Co (remainder) alloy containing a large amount of Co is used, it will inhibit the adhesion between the contact material and the lead piece during the next plating process, and the intended purpose will not be achieved. Can not. (d) Purpose of the Invention The present invention solves these problems in conventional reed switches, and realizes a reed switch that has good adhesion between the reed piece and the contact, is less prone to adhesion, and has low contact resistance. The purpose is to (e) Structure of the invention In order to achieve this object, the present invention
After deburring a lead piece made of a ferromagnetic material of 18%)-Co (residual) alloy by electrolytic polishing with a phosphoric acid solution with a phosphoric acid concentration of 90% or more, the contact part of the lead piece is A method is used in which the contacts are attached and sealed in a sealed container. (f) Embodiments of the Invention Next, examples will explain how the reed switch according to the present invention is actually implemented. Third
The figure is a sectional view showing a reed switch manufactured according to the present invention. The lead pieces 2 and 3 were made of Fe (10 to 18%)-Co (remainder) alloy instead of 52 alloy. After pressing, these lead pieces 2 and 3 are electrolytically polished using a phosphoric acid solution with a phosphoric acid concentration of 90% or more to remove burrs and improve the surface condition, and then the contact material is plated and diffused. ing. Reference numeral 6 denotes a contact point made by gold plating and diffusion treatment at the tips of the lead pieces 2 and 3 of Fe (10 to 18%)-Co (remainder) alloy. Furthermore, argon is sealed in the glass tube 1 as an inert gas. FIG. 4 is a block diagram showing the method for manufacturing this reed switch in the order of steps. Firstly, Fe (10-18%)
-Press a round bar of Co (residual) alloy to create a glass tube 1.
The portion enclosed within is flattened to obtain predetermined elastic properties. Next, after cutting to a predetermined length, heat treatment (annealing) is performed under predetermined conditions in order to recover the deterioration of magnetic properties caused by pressing. Then, the lead pieces 2 and 3 are electrolytically polished using the method of the present invention. The conditions for electrolytic polishing are a phosphoric acid concentration of 90
% or more of phosphoric acid solution. In other words, the reason why the surface condition deteriorates when electrolytically polished under the same conditions as 52 alloy is that the oxide film produced by anodizing is less uniform in Fe-Co alloy than in 52 alloy, and the elution of Co becomes more intense. it is conceivable that. Therefore, the composition of the electrolytic polishing solution was changed to a phosphoric acid concentration of 90%.
% or more concentrated phosphoric acid solution (H ₃ PO ₄ ), and if necessary, add additives whose main component is ethylene glycol or the like. Electrolytic polishing is then performed using the lead piece as an anode. Fe (10-18%) - Co with such concentrated phosphoric acid solution
When the (remaining) alloy was electrolytically polished to remove burrs,
Compared to those electrolytically polished using conventional electrolytic polishing liquid,
A uniform condition with no pits and no surface roughness was obtained. The deburred lead pieces are then plated with a contact material such as gold. As mentioned above, since the surface of the reed piece is made uniform by the concentrated phosphoric acid solution, the adhesion of the plating is sufficient. The lead piece plated with the contact material is further heat treated to cause diffusion between the contact material and the lead piece. That is, the lead pieces 2 and 3 plated with contact material are placed in a furnace and heated to 800±
Heat treatment is performed in hydrogen (H ₂ ) at a temperature of 100° C. for 15 to 60 minutes to diffuse 3 to 10% atomic weight of Co onto the contact surface. Deburring with a concentrated phosphoric acid solution as described above improves the adhesion of the plating, and since the space between the lead piece and the contact material is subjected to diffusion treatment, the adhesion between the lead piece and the contact material becomes even more reliable. Finally, the entire manufacturing process is completed by sealing in a glass tube in an argon gas atmosphere and inspecting it. FIG. 5 shows the relationship between the amount of Co precipitated, the adhesion properties, and the contact resistance when the Co in the lead piece is diffused to the surface of the gold contact as described above. The horizontal axis is the amount of Co deposited on the gold contact surface (%), and the vertical axis is the adhesive property (magnetostriction test open value change rate) and contact resistance value. When the Co diffusion amount is 3% or more, the magnetostriction test open value change rate is 20% or less, and the adhesiveness is greatly improved. On the other hand, the contact resistance is preferably all gold because the amount of Co diffused is small, but if the amount of precipitation is 6% or less, the contact resistance is almost the same as 30Ω in the case of only gold. Ten
% or less, it is less than 60Ω, which does not pose much of a problem in practice. Figure 6 is a diagram showing the relationship between the diffusion treatment temperature and time of Fe (10 to 18%) - Co (remainder) alloy and the amount of Co precipitation.
The horizontal axis is the annealing temperature, and the vertical axis is the Co precipitation amount.
As mentioned above, both adhesion and contact resistance show acceptable values.
The amount of Co precipitated is about 3 to 10%;
In order to obtain the amount of Co precipitated, a temperature of approximately 700 to 900°C is appropriate when the annealing time is 15 minutes, and a temperature of 760°C or less is appropriate when the annealing time is 60 minutes. Figure 7 is a diagram showing the coefficient of thermal expansion of Fe-Co alloy.
The horizontal axis is the content of iron (Fe) in cobalt (Co),
The vertical axis is the coefficient of thermal expansion. Since the Fe-Co alloy lead pieces 2 and 3 are directly sealed to the glass tube 1, cracks will not occur in the glass tube when the lead pieces 2 and 3 are sealed to the glass tube 1 in the same way as conventional 52 alloy. In order to prevent this from occurring, it is required that the coefficients of thermal expansion of the lead pieces 2 and 3 and the glass tube 1 be equal. Fe
In the case of a -Co alloy, a coefficient of thermal expansion approximately equal to that of a glass tube can be obtained depending on the Fe content. In other words, the coefficient of thermal expansion of the glass tube is 117.5±2.5×10 ^-7 /
℃, but the Fe-Co alloy used in the present invention has a coefficient of thermal expansion comparable to that of glass in the range of Fe content of 8.5 to 20%. Figure 8 is a diagram showing the electrical resistivity of Fe-Co alloy.
The horizontal axis is the content of iron (Fe) in cobalt (Co),
The vertical axis is electrical resistivity. In the region of 8.5-20% Fe, where the coefficient of thermal expansion is equal to that of glass, the electrical resistivity is 12
~14 μΩcm, which is the electrical resistivity of 52 alloy, the most commonly used lead material.
Much better than 35μΩcm. In this way Fe
-Co alloy has low electrical resistivity, so the temperature rise when electricity is applied is small, and it was confirmed that it is superior to 52 alloy. Figure 9 shows the combination of 12%Fe-88%Co alloy and 52 alloy.
This is a diagram showing the rate of change in resistance with respect to the current value.
-88% Co alloy is better than 52 alloy.
FIG. 10 is a hysteresis curve showing the magnetic properties of a 12%Fe-88%Co alloy. The above characteristics are summarized in Table 1.

[Table] Figure 11 shows the conventional 52 alloy and the Fe according to the present invention.
FIG. 3 is a diagram comparing the life characteristics of lead pieces made of (10 to 18%)-Co (remainder) alloy in the case of nitrogen (N ₂ ) encapsulation and the case of argon (Ar) encapsulation according to the present invention.
As is clear from this figure, Fe (10-18
%) - Reed switch using Co (remainder) alloy,
Even when sealed with nitrogen, it is superior to the conventional one sealed with argon, demonstrating the effects of the various properties of the Fe (10-18%)-Co (balance) alloy. Also, reed switches made of Fe (10-18%)-Co (remainder) alloy sealed with argon have a longer lifespan than those sealed with nitrogen. (g) Effect of the invention As is clear from the above characteristic diagrams, Fe(10
~18%) - Co (remainder) alloy has good sealing properties with glass tubes,
It has extremely excellent electrical and magnetic properties, and its properties as a lead piece are more promising than 52 alloy. The present invention utilizes such Fe (10~
18%) - Co (residual) alloy lead piece is deburred by electrolytic polishing with concentrated phosphoric acid solution, and the contact material is plated and diffused on the lead piece with a uniform surface condition. Therefore, unlike 52 alloy, the amount of precipitated Fe that worsens contact resistance is small, and Co, which is stable against oxidation, is precipitated, so contact resistance is extremely low, and oxidation is further suppressed by argon sealing, resulting in an extremely long life. becomes. In addition, since cobalt is precipitated to the contact surface, the adhesion of the contact is improved, the surface roughness during deburring of the lead piece is improved, and the lead piece and the contact material are diffused, so the contact material and the lead piece are It also has excellent adhesion with other materials, resulting in an even longer lifespan.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the general structure and contact portion of a conventional reed switch, Fig. 2 is a sectional view showing the deburring process of the reed piece, and Fig. 3 is a sectional view showing a reed switch manufactured by the method of the present invention. , FIG. 4 is a process diagram showing the manufacturing process of the reed switch according to the present invention. Figure 5 and subsequent figures show various characteristics of the reed switch according to the present invention. Figure 5 is a diagram showing adhesive properties and contact resistance characteristics, Figure 6 is a diagram showing the relationship between annealing temperature and time and Co precipitation amount, Figure 7 is a diagram showing the relationship between Fe content and thermal expansion coefficient, Figure 8 is a diagram showing the relationship between Fe content and electrical resistivity, and Figure 9 is a diagram showing the relationship between Fe content and electrical resistivity.
A diagram showing the resistance change rate of 12Fe, Co alloy, Figure 10 is a diagram showing the hysteresis curve of 12Fe, Co alloy,
FIG. 11 is a diagram showing the life characteristics depending on the difference in filler gas. In the figure, 1 is a glass tube, 2 and 3 are lead pieces, 4 is an excitation coil, 5 is a contact gap, 6 is a gold contact, 71 is a flat plate portion of the lead piece, and 72 is a burr.

Claims (1)

[Claims] 1. A lead piece made of a ferromagnetic material of Fe (10 to 18%)-Co (remainder) alloy is deburred by electrolytic polishing with a phosphoric acid solution having a phosphoric acid concentration of 90% or more. 1. A method for manufacturing a reed switch, characterized in that after the reed piece has aged, a contact is attached to the contact part of the reed piece, and the reed piece is sealed in a sealed container. 2. The method for manufacturing a reed switch according to claim 1, wherein argon gas is sealed when the reed piece is sealed in the sealed container.