Joints, fastening parts, insulators and current feedthroughs

Abstract

To provide a joined body that is less likely to crack and in which no brazing fillet is formed externally, even after repeated heating and cooling; and to provide a fastening component, insulator, and current introduction terminal including the same.SOLUTION: A joined body of the present disclosure includes: a base body made of a ceramic and having a step part; and a columnar body made of metal and standing on the step part, wherein: the columnar body includes a shaft part and a flange part that is integrally formed with the shaft part at one end of the shaft part and whose thickness is smaller than a depth of the step part; the columnar body has a gap between an outer peripheral surface of a flange part and an inner peripheral surface of the step part; the columnar body is joined to an inner bottom surface of the step part via a brazed section; and the brazing section has a first fillet that contacts an outer peripheral surface of the flange part and an inner bottom surface of the step part and a second fillet that contacts the inner peripheral surface and the inner bottom surface of the step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a joint between a ceramic substrate and a metal columnar body, a fastening part such as a screw, and an insulator and a current input terminal including the fastening part. [Background technology]

[0002] Fastening parts such as screws are made of metal, plastic, ceramics, etc., and metal screws are often used in applications requiring strong fastening. On the other hand, ceramic screws are used in applications requiring insulation or high temperatures. However, when ceramic screws are used in applications requiring strong fastening, their threads can be damaged when tightened, making them unusable due to their low toughness.

[0003] To solve these problems, Patent Document 1 proposes a composite screw in which the head of the screw is made of ceramic and the threaded part is made of metal, with the metal of the threaded part inserted into a recess in the ceramic head part, and the two are brazed together using an active metal method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-303358 Summary of the Invention [Problem to be solved by the invention]

[0005] In the examples of Patent Document 1, it is described that the head portion of the composite screw is made of silicon nitride ceramics and the thread portion is made of stainless steel (SUS304), but there is a large difference in the average linear expansion coefficient between them. With such a large difference in the average linear expansion coefficient, the brazing material is filled without any gaps between the inner bottom surface of the ceramic recess and the end face of the thread portion, and between the inner circumferential surface of the ceramic recess and the outer circumferential surface of the thread portion, so there is a problem that cracks are likely to occur in the head portion and the thread portion when heated and cooled repeatedly.

[0006] In addition, at the boundary between the head and threads of the screw, some of the brazing material tends to spill out of the recess, forming a fillet between the end face of the head and the outer periphery of the thread. Therefore, when attempting to fasten a compound screw to a female thread, the fillet becomes an obstacle, making it impossible to fully fasten the screw to the female thread, resulting in insufficient fastening.

[0007] Therefore, an object of the present disclosure is to provide a joint that is less likely to crack even when repeatedly heated and cooled and in which a fillet of the brazing material is not formed on the outside, as well as a fastening part, an insulator, and a current introduction terminal that include the joint. [Means for solving the problem]

[0008] The joined body of the present disclosure, which solves the above-described problems, comprises a base made of ceramic having a step portion on its surface, and a columnar body made of metal erected on the step portion, the columnar body having a shaft portion and a flange portion formed integrally with the shaft portion at one end of the shaft portion and having a thickness smaller than the depth of the step portion, there is a gap between the outer peripheral surface of the flange portion and the inner peripheral surface of the step portion, and the columnar body is joined to the inner bottom surface of the step portion via a brazing portion, and the brazing portion has a first fillet in contact with the outer peripheral surface of the flange portion and the inner bottom surface of the step portion and a second fillet in contact with the inner peripheral surface and inner bottom surface of the step portion.

[0009] A fastening part of the present disclosure includes the above-described joint, and the shank has a threaded portion. An insulator of the present disclosure includes the above-described fastening part. A current input terminal of the present disclosure includes the above-described fastening part. [Effects of the Invention]

[0010] According to the joint of the present disclosure, the brazed portion has the first fillet and the second fillet, which makes it less likely to come into contact with the shaft portion. Therefore, even if heating and cooling are repeated, internal stress is less likely to accumulate in the base body or the columnar body, and cracks are less likely to occur in either of them. In addition, since the fillet of the brazing material is not formed outside the step portion, when a threaded portion is provided on the shank and fastened to a female screw or to a joined body, the entire axial length can be used (i.e., the entire length of the shank that protrudes from the base can be used), thereby obtaining a high joining force. Furthermore, since the female screw or the joined body can be abutted against the outer peripheral end face of the step portion, a higher joining force can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a bonded body according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of part A in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present disclosure will now be described: Fig. 1 shows a cross section of a bonded body according to an embodiment of the present disclosure, and Fig. 2 is an enlarged view of part A thereof.

[0013] 1, a bonded structure 1 according to this embodiment includes a substrate 3 having a step portion 2 on its surface, and a metal pillar 4 standing on the step portion 2. In this embodiment, the step portion 2 forms a recess. The substrate 3 is made of ceramics such as alumina (Al2O3), zirconia (ZrO2), aluminum nitride (AlN), silicon nitride (Si3N4), silicon carbide (SiC), etc. The columnar body 4 is made of metal such as Fe-Co alloy, Fe-Co-C alloy, Fe-Ni alloy, Fe-Ni-Co alloy, etc.

[0014] The columnar body 4 includes a shaft portion 41 and a flange portion 42 formed integrally with the shaft portion 41 at one end of the shaft portion 41. The flange portion 42 is formed in an annular shape around the shaft portion 41, and has a thickness smaller than the depth of the stepped portion 2. A gap 5 is formed between the outer peripheral surface of the flange portion 42 and the inner peripheral surface of the stepped portion 2.

[0015] The step portion 2 preferably has a circular cross section perpendicular to the surface of the base 3 or the inner peripheral surface of the step portion 2. The shaft portion 41 is cylindrical, for example, with a radius of 2 mm or more and 4 mm or less, and the difference between the radius of the flange portion 42 and the radius of the shaft portion 41 is preferably 0.8 mm or more and 1.4 mm or less. This increases the bonding strength between the columnar body 4 and the base 3. A thread portion 6 is formed on the outer peripheral surface of the shaft portion 41. The radius of the flange portion 42 is preferably 2.8 mm or more and 5.4 mm or less.

[0016] 2, the columnar body 4 is joined to the inner bottom surface of the stepped portion 2 via a brazing portion 7. The brazing portion 7 has a first fillet 71 that contacts the outer peripheral surface of the flange portion 42 and the inner bottom surface of the stepped portion 2, and a second fillet 72 that contacts the inner peripheral surface and inner bottom surface of the stepped portion 2.

[0017] In this way, the brazing portion 7 has the first fillet 71 and the second fillet 72, which makes it difficult for the brazing material to come into direct contact with the shaft portion 41. Therefore, even if heating and cooling are repeated, internal stress is unlikely to accumulate in the base 3 or the columnar body 4, making it difficult for cracks to occur in both.

[0018] In order to form the first fillet 71 and the second fillet 72 along the outer peripheral surface of the flange 42 and the inner peripheral surface of the stepped portion 2, respectively, it is necessary to provide a gap 5 of a predetermined length between the outer peripheral surface of the flange 42 and the inner peripheral surface of the stepped portion 2. The gap 5 between the outer peripheral surface of the flange 42 and the inner peripheral surface of the stepped portion 2 is preferably 0.8 mm or more and 2 mm or less. This allows the stress between the base 3 and the columnar body 4 to be dispersed by the first fillet 71 and the second fillet 72, improving durability and enabling use over a long period of time.

[0019] To keep the length of the gap 5 constant, it is preferable to have a positioning means so that the pillars 4 are erected at predetermined positions within the stepped portion 2. In this embodiment, the base 3 has a receiving portion 8 recessed in the stepped portion 2, and the pillars 4 have pins 9, which are inserted into the receiving portion 8, on the surface facing the inner bottom surface of the stepped portion 2 (see FIG. 1). This allows the pillars 4 to be positioned within the stepped portion 2 and also makes it easy to improve the coaxiality between the base 3 and the pillars 4. The latter is a necessary characteristic when the joined body 1 is used as a fastening part such as a screw.

[0020] Furthermore, it is preferable that the surface of the brazing portion 7 is exposed on the side of the columnar body 4. In other words, it is preferable that the surface of the brazing portion 7 opposite to the inner bottom surface of the step portion 2 is exposed. In other words, this means that the brazing portion 7 is not covered with glass or the like. For example, the adhesion of glass to the columnar body 4, which tends to occur with covering, is eliminated, making it easier to fasten the shank 41 to a female screw (not shown) or to a body to be connected (not shown).

[0021] Next, a method for joining the ceramic substrate 3 and the metal columnar body 4 will be described. In this embodiment, a first metallized layer 10a is provided on the inner bottom surface (e.g., the entire inner bottom surface) of the stepped portion 2 of the substrate 3, and a second metallized layer 10b is provided on the inner peripheral surface. Providing the first and second metallized layers 10a and 10b allows the use of a relatively inexpensive brazing filler metal, such as a silver brazing filler metal (Bag-8, Bag-9).

[0022] It is preferable that a first plating layer (not shown) is provided on the first metallization layer 10a, and a second plating layer (not shown) is provided on the second metallization layer 10b. This prevents oxidation of the first and second metallization layers, allowing for long-term use. The first and second plating layers may be, for example, well-known Ni plating layers. The first and second plating layers can be formed, for example, by supplying a plating current to the exposed surface of the metallized layer in a plating solution to perform electroplating.

[0023] In the brazing, the columnar body 4 is joined to the first metallized layer 10a, the second metallized layer 10b, and the first and second plating layers via the brazing material. As a result, the base body 3 made of ceramic and the columnar body 4 made of metal are joined via the brazing portion 7.

[0024] The first and second metallization layers 10a, 10b are primarily composed of high-melting-point metals such as W, Mo, and Mn, or are composed of Ag-Cu-Ti layers. For example, a metal paste for the metallization layers is applied to the ceramic substrate 3 by screen printing or the like, and then fired in a high-temperature atmosphere at 1300°C to 1600°C, thereby adhering and forming the metallization layers on the surface of the substrate 3. The first and second metallization layers 10a, 10b may be formed of the same or different components, and may have the same or different thicknesses. Similarly, the first and second plating layers may be formed of the same or different components, and may have the same or different thicknesses.

[0025] The length of the second metallized layer 10b in the depth direction of the step portion 2 is preferably shorter than the length of the inner peripheral surface of the step portion 2 in the depth direction. Specifically, it is preferably 60% or less and 80% or more of the length of the inner peripheral surface of the step portion 2 in the depth direction. This reduces the risk of the brazing material forming a fillet on the outer end surface (or the inner surface on the upper edge side) of the step portion 2, allowing the female screw or the object to be joined to be inserted deeper into the shaft portion 41 without being obstructed by the fillet, thereby obtaining a high joining force.

[0026] Examples of brazing materials that can be used to form the brazing portion 7 include Au brazing material, Ag brazing material, Cu brazing material, Au-Cu brazing material, Ag-Cu brazing material, and Au-Ni brazing material. Preferably, brazing materials with solidus temperatures of 900°C or higher, such as Au brazing material, Cu brazing material, Au-Cu brazing material, and Au-Ni brazing material, are used. This configuration allows the material to withstand long-term use without melting even at temperatures of 400°C or higher, thereby achieving highly reliable bonding.

[0027] The brazing material may be in a solid form, such as a sheet, block, or granule, or may be prepared in a paste form. To join the base 3 and the columnar body 4, for example, the columnar body 4 is erected in the step portion 2 of the base 3 having the first and second metallized layers 10a and 10b formed on its surface, and then the brazing material is placed around the columnar body 4 and melted, allowing it to penetrate and diffuse between the base 3 and the columnar body 4 by capillary action, and then cooled and solidified to form the brazed portion 7.

[0028] The first fillet 71 and the second fillet 72 can be formed, for example, by placing linear or granular brazing material at the boundary between the outer circumferential surface of the flange 42 and the inner bottom surface of the stepped portion 2, and at the boundary between the inner circumferential surface and the inner bottom surface of the stepped portion 2, or by applying a paste-like brazing material to these boundaries. The first fillet 71 and the second fillet 72 may be formed simultaneously with the formation of the brazed portion 7, or may be formed after the brazed portion 7 is formed.

[0029] In the above embodiment, the columnar body 4 is brazed via the first and second metallization layers 10a, 10b, but it is also possible to directly braze the columnar body 4 using an active metal method without using the first and second metallization layers 10a, 10b. In the active metal method, an active metal brazing filler metal such as Cu-Ag, Cu-Au, Cu-Ni, or Au-Ni is used, to which an active metal such as Ti or Zr is added.

[0030] The joined body 1 of the present disclosure can be used as a fastening component having a threaded portion 6 on a shaft portion 41. The fastening component includes a threaded component as defined in JIS B 0101:2013. The fastening component of the present disclosure is made of a composite material of ceramics and metal, and therefore can be suitably used, for example, as an insulator used to insulate between an electric wire and its support.

[0031] Furthermore, the fastening component of the present disclosure can also be suitably used as a current input terminal. A current input terminal is generally a terminal for supplying a large current, such as for power supply or heating, from the outside (atmospheric side) to the inside of a vacuum or pressure vessel. Since one side is at atmospheric pressure and the other side is at vacuum or high pressure, a leak-free airtight sealing structure is essential, and ceramics are commonly used to seal the insulating parts.

[0032] Although the embodiments of the present disclosure have been described above, the joined bodies, fastening parts, insulators, and current introduction terminals of the present disclosure are not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the present disclosure. [Explanation of symbols]

[0033] 1 zygote 2 Step 3 Base 4 columnar body 41 Shaft 42 Tsuba 5 Gap 6 Threaded section 7 Brazed part 71 First fillet 72 Second fillet 8 Storage section 9-pin 10a First metallized layer 10b Second metallized layer

Claims

1. a ceramic substrate having a stepped portion on its surface; a metal pillar provided upright on the step portion, The columnar body includes a shaft portion and a flange portion that is integrally formed with the shaft portion at one end of the shaft portion and has a thickness smaller than the depth of the step portion, and there is a gap between the outer peripheral surface of the flange portion and the inner peripheral surface of the step portion, the columnar body is joined to the inner bottom surface of the step portion via a brazing portion, the brazing portion having a first fillet in contact with the outer circumferential surface and the inner bottom surface and a second fillet in contact with the inner circumferential surface and the inner bottom surface, The bonded body, wherein the first fillet and the second fillet are concavely rounded.

2. 2. The joined body according to claim 1, wherein the shaft portion is cylindrical, and the difference between the radius of the flange portion and the radius of the shaft portion is 0.8 mm or more.

3. The bonded body according to claim 1 or 2, wherein the gap is 0.8 mm or more.

4. 4. The joined body according to claim 1, wherein a first metallized layer is provided on the inner bottom surface and a second metallized layer is provided on the inner circumferential surface.

5. 5. The joined body according to claim 4, wherein a first plated layer is provided on said first metallized layer, and a second plated layer is provided on said second metallized layer.

6. The bonded body according to claim 4 or 5, wherein the second metallized layer has a length shorter than the length of the inner circumferential surface in the depth direction.

7. 7. The joined body according to claim 1, wherein the surface of the brazed portion is exposed on the side of the columnar body.

8. The bonded body according to any one of claims 1 to 7, wherein the base has a recessed storage portion in the inner bottom surface, and the columnar body has a pin on an opposing surface facing the inner bottom surface, the pin being inserted into the storage portion.

9. A fastening component comprising the joined body according to any one of claims 1 to 8, wherein the shank has a threaded portion.

10. An insulator comprising the fastener of claim 9.

11. A current input terminal comprising the fastening component according to claim 9.

Images