JP2008137047A - High electrically conductive object to be joined and its diffusion welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high electrically conductive object to be joined having a structure by which a welding result with a high welding strength can be easily obtained at a low cost and also to provide a diffusion welding method. <P>SOLUTION: The high electrically conductive object to be joined forms a diffusion welding face by being diffusion welded with other object to be joined. This high electrically conductive object is equipped with an annular projection projecting from its joining side face. In the center region surrounded with the annular projection, there are provided a recess or an inner peripheral groove that houses a plastically fluidized metallic material of the annular projection when the high electrically conductive object and other object are diffusion welded. The high electrically conductive object to be joined is characterized in that the recess or the inner peripheral groove has a depth which becomes lower than the joining side face of the high electrically conductive object, making the annular projection be diffusion welded. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a highly conductive joints made of various kinds of metal materials of the same or different types, particularly highly conductive copper members and copper members that have been considered to be extremely difficult to join by conventional welding methods such as copper members, Alternatively, the present invention relates to a highly conductive workpiece having a projection structure suitable for diffusion-bonding a highly conductive workpiece and another workpiece having lower conductivity than that and a diffusion bonding method thereof.

  The same kind of metal materials, iron-based material and stainless steel material, or iron-based material and copper material, or iron-based material and aluminum material, and further copper material or aluminum material and iron-based material, stainless steel material, brass, etc. Various methods of joining dissimilar metal materials having different characteristics such as conductivity have been proposed. Joining of dissimilar metal materials can be achieved by joining by hard soldering, ultrasonic joining, or mechanical joining such as caulking and bolting. Often joined. In addition, even when joining the same kind of metal materials, the joining of copper materials and copper materials having very good electrical conductivity, or joining between aluminum materials and aluminum materials has been performed by the same means. In the method, from the viewpoint of using a copper material or an aluminum material having a very good conductivity, the resistance of the junction cannot be made small enough to be ignored. For these reasons, it is considered that diffusion bonding between copper materials with very good electrical conductivity, aluminum materials, or copper materials and aluminum materials is particularly difficult. Efforts have already been made, and an improved technique is disclosed that enables resistance welding between a copper material and an aluminum material by performing the following processing steps in advance (see, for example, Patent Document 1).

Since this method cannot directly resistance weld a copper material and an aluminum material, a tin film is previously formed on the bonding surface of the copper material before resistance welding, and further processing is performed to obtain an interface between the copper material and tin. After forming a tin coating layer in which a solid solution of copper and tin is formed, the tin coating layer is brought into contact with the aluminum material, and the tin coating layer formed in the solid solution is placed between the copper material and the aluminum material. Pressure is applied in a state of being interposed between the electrodes and resistance welding is performed by passing a welding current. This resistance welding method is realized by using an inverter-type welding machine instead of a capacitor-type welding machine to flow a high-frequency welding current between the copper material and the aluminum material, thereby melting the joint between the copper material and the aluminum material. Then, welding is performed by forming a nugget in which molten copper and aluminum are mixed with each other. In addition, when bonding dissimilar metals, a diffusion bonding method and a bonding apparatus have been already reported in which good bonding results can be obtained by processing a diffusion bonding portion of dissimilar metals into an optimal special shape in advance (for example, patents). Reference 2-5). Also, in order to eliminate the need for pretreatment such as pickling to remove the oxide film or dirt on the bonding surface such as aluminum or magnesium during diffusion bonding, projections are formed on both of the objects to be bonded, and the tops of the projections are connected to each other. A method of joining by abutting is also disclosed (for example, see Patent Document 6).
JP 2001-087866 A Japanese Patent Laid-Open No. 08-1118040 Japanese Patent Laid-Open No. 10-128550 Japanese Patent Laid-Open No. 10-156548 Japanese Patent Laid-Open No. 11-033737 JP 2002-103056 A

  However, in the resistance welding method disclosed in Patent Document 1, the tin film is formed on the bonding surface of the copper material, and the solid solution layer of copper and tin is further formed, and then the copper material and the aluminum material are formed. Therefore, a tin film, which is a low melting point metal film, must be formed before welding. This means that a step of forming a solid solution layer of copper and tin after forming a tin film by plating or the like is necessary, and because the tin material is mixed into the welded portion of the copper material and the aluminum material, There is a drawback in that the resistance at the weld becomes large. In addition, a very large welding current must be passed to form a nugget by melting highly conductive metals, and this point is also a major problem, but the heat of the nugget formed by melting There is also a problem that tin in the molten part becomes dust and scatters vigorously.

  The structures of the joints described in the above-mentioned patent documents 2 to 5 are suitable for objects to be joined made of different kinds of metal materials having a specific structure, but in particular, copper materials and copper materials, or aluminum materials and aluminum materials, or It is difficult to apply as it is to diffusion bonding between a copper material and an aluminum material, or between a copper material or an aluminum material and a metal material having a lower conductivity, and disclosed in Patent Document 4 or Patent Document 5 described above. It is difficult to obtain a stable bonding result even with a bonding apparatus. As described in the above-mentioned Patent Document 6, even if projections are provided on both a copper material and an aluminum material and they are butt-joined to each other, a time lag occurs in the plastic fluidization of the aluminum material and the copper material. Therefore, a sufficiently stable joining result cannot be obtained, and there is a problem that the projections must be aligned, and the bonding must be performed while maintaining the alignment state. It is often difficult to use the diffusion bonding method described in.

  The present invention solves the above-described problems, and a highly conductive object such as a copper material or an aluminum material has a very high conductivity without forming a low melting point metal film such as a tin film on the diffusion bonding surface. Diffusion bonding between each other, or diffusion bonding between such highly conductive objects to be bonded and other objects made of metal materials such as stainless steel, iron, or brass having lower conductivity is possible and simple. The main object of the present invention is to provide a highly conductive object to be bonded and a diffusion bonding method having a structure capable of obtaining a bonding result with high bonding strength at low cost.

  The first invention is a highly conductive object that is diffusion bonded to another object to form a diffusion bonding surface, and the high conductivity bonding object has an annular projection protruding from the bonding side surface. A metal material that is plastically fluidized in the annular projection when the highly conductive object to be bonded and the other object to be bonded are diffusion-bonded to a central surface area surrounded by the annular projection. A recess or an inner peripheral groove, the recess or the inner peripheral groove has a depth lower than the bonding side surface of the highly conductive workpiece, and a base surface area of the projection is the diffusion Provided is a highly conductive object to be bonded.

  According to a second invention, in the first invention, the highly conductive object to be bonded is copper or a copper alloy, or aluminum or an aluminum alloy.

  According to a third aspect of the present invention, there is provided the highly conductive bonded object according to the first aspect or the second aspect, wherein an opening angle of a longitudinal section of the annular projection is in a range of 60 to 120 degrees. provide.

  According to a fourth aspect of the present invention, a bonding current is passed between a highly conductive object having an annular projection protruding from a bonding side surface and another object to be bonded, and the highly conductive object to be bonded and the other object. A diffusion bonding method in which a diffusion bonding surface is formed by diffusion bonding with a bonded object, and a pressure is applied so that a root surface area of the annular projection becomes the diffusion bonding surface area. Provided is a diffusion bonding method for a highly conductive object to be bonded, wherein the bonding current is applied while being applied to the other object to be bonded.

  According to a fifth aspect of the present invention, in the fourth aspect, the junction current is a pulsed current having a time required for the current to rise to a peak value of 10 ms or less. A diffusion bonding method is provided.

  According to a sixth invention, in the fourth invention or the fifth invention, the applied pressure is a pressure on which an elastic force is superimposed, and the required pressure is not affected by the plastic fluidized annular projection. Provided is a diffusion bonding method for a highly conductive object to be bonded, wherein a pressure is applied to the diffusion bonding surface.

  According to the first and second aspects of the invention, the plastic fluidized metal material is accommodated in the recess or inner peripheral groove of the central surface area surrounded by the annular projection, so that the highly conductive coating is provided. Since the diffusion bonding surface between the bonded object and the other object to be bonded becomes the base surface area of the annular projection, the diffusion bonding surface becomes large, and a required pressure can be applied to the diffusion bonding surface. Therefore, it is possible to efficiently improve the bonding strength of the diffusion bonding portion and to provide a highly conductive object that can stabilize the bonding strength. Moreover, it is applicable to copper, copper alloy, aluminum, and aluminum alloy.

  Further, according to the third invention, in addition to the effects obtained by the first invention or the second invention, the highly conductive object to be bonded and the other object to be bonded are more securely diffusion bonded. By selecting a small opening angle of the longitudinal cross section of the annular projection in the range of 60 to 120 degrees, it is possible to connect between a highly conductive object to be bonded and another object to be bonded without reducing the bonding strength. The applied pressure can be further reduced.

  According to the fourth invention, regardless of the shape of the projection, when energizing the junction current, the diffusion junction surface between the highly conductive object to be bonded and the other object to be bonded is in the root surface area of the annular projection. In order to make them equal, the diffusion bonding surface can be enlarged, and the required pressure can be applied to the diffusion bonding surface because the pressure area is not dispersed in the plastic fluidized metal material of the projection. Therefore, the bonding strength of the diffusion bonding portion can be improved efficiently, and the bonding strength can be stabilized.

  According to the fifth invention, in addition to the effects obtained in the fourth invention, the pulsed junction current reaches a peak value in a very short time of about 10 ms or less, so that copper or copper having very high conductivity can be obtained. Even a highly conductive object such as aluminum can be diffusion-bonded more stably and satisfactorily. Further, since the diffusion bonding portion does not change color, the appearance of the bonded material is not impaired.

  According to the sixth invention, in addition to the effects obtained in the fourth invention or the fifth invention, the required pressure can be applied to the diffusion bonding surface without being affected by the metal material of the plastic fluidized projection. Therefore, the highly conductive object to be bonded can be diffusion-bonded stably and satisfactorily.

[Embodiment 1]
In diffusion bonding of metal materials, when the bonding current flows, the contact resistance between the metal materials and the heat generated by the resistance of the metal material cause plastic fluidization, that is, softening at the contact surfaces of both metal materials. Occurs and bonding takes place. However, since the resistivity of copper material or aluminum material is extremely small, the amount of heat generated due to the resistance and contact resistance is insufficient, and satisfactory diffusion bonding strength is obtained unless the required bonding strength is extremely small. Is difficult. Diffusion bonding with extremely low required bonding strength is possible, but in order to satisfy the actual required bonding strength, the shape and surface of the joint of a highly conductive workpiece made of copper material or aluminum material It was difficult to apply to an actual production line because various restrictions such as conditions, conditions of the junction current, and various characteristics of the bonding apparatus were severe.

  In the present invention, as a result of research on diffusion bonding between highly conductive objects to be bonded or diffusion bonding between a highly conductive object to be bonded and other metal materials such as stainless steel, brass (brass), iron, etc. It was confirmed that the diffusion bonding strength can be improved under certain bonding conditions. This point will be described with reference to FIG. 1 while explaining Embodiment 1 of the highly conductive object W1 according to the present invention. FIG. 1A is a view of the highly conductive object W1 as viewed from above, and FIG. 1B is a view showing a longitudinal section taken along a cutting line X-X ′ in FIG. First, the range to which the present invention can be applied is diffusion bonding such as bonding objects made of various common metal materials or bonding objects made of various different metal materials. For example, diffusion bonding of a highly conductive workpiece W1 made of copper or a copper alloy (hereinafter referred to as a copper material) or aluminum or an aluminum alloy (hereinafter referred to as an aluminum material), which is considered to be extremely difficult to perform diffusion bonding. This will be described below.

  In FIGS. 1A and 1B, an annular projection P protruding from the bonding side S1 is formed on the bonding side S1 of the highly conductive object W1. The annular projection P has a top surface P1, an inner peripheral inclined surface P2, and an outer peripheral inclined surface P3 having a small annular width. In the case of the annular projection P, even if the contact area between the annular top surface P1 and the other object W2 is the same size as the conventional frustoconical projection, the annular projection P has an annular shape. The line contact area is substantially wider than that of the conventional dot area, the diffusion bonding area can be increased, and the heat balance is good, so that the bonding strength can be improved. Therefore, in the first embodiment, an annular projection P having a trapezoidal longitudinal section is formed on the highly conductive workpiece W1.

  In the surface area surrounded by the annular projection P, a cylindrical recess A deeper than the joint side surface S1 is formed in the vicinity of the inner peripheral inclined surface P2. The recess A has a volume sufficient to accommodate the annular projection P metal material that is plastically fluidized during diffusion bonding. The shape of the recess A is not limited as long as the metal material of the annular projection P that is plastically fluidized at the time of diffusion bonding can easily enter the recess A by the applied pressure. Preferably, almost all of the metal material of the annular projection P that plastically fluidizes during diffusion bonding is accommodated in the recess A, and the recess A has a volume that does not cause a void.

  Here, the annular projection P will be described in a little more detail. The angle at which the extension line of the inner peripheral inclined surface P2 and the extension line of the outer peripheral inclined surface P3 intersect shown by the broken line in FIG. 1B is referred to herein as the opening angle θ of the longitudinal section of the annular projection P. The opening angle θ is preferably in the range of 60 to 120 degrees. When the opening angle θ is less than 60 degrees, the area of the root surface area P4 (shown by a broken line) and the top face P1 of the annular projection P in the same horizontal plane as the joining side surface S1 of the highly conductive workpiece W1. Therefore, even when the peak value of the junction current is adjusted, diffusion bonding is not performed satisfactorily at the root surface area P4 of the annular projection P, and the desired diffusion junction strength is obtained. There is a problem that it is difficult to obtain.

  When the opening angle Θ exceeds 120 degrees, the area of the root surface area P4 (shown by a broken line) and the top surface P1 of the annular projection P on the same horizontal plane as the bonding side surface S1 of the highly conductive workpiece W1. Is too large, the required pressure may not be applied in the process of plastic fluidization of the projection P. Even if the peak value of the junction current is adjusted, the root surface area P4 of the annular projection P There is a problem that diffusion bonding is not performed well and it is difficult to obtain desired diffusion bonding strength. Therefore, the highly conductive workpiece of the first embodiment preferably includes an annular projection P having a relatively small angle in such a range, and is recessed in a surface area surrounded by the annular projection P. Since the metal A of the projection P plasticized and fluidized at the time of diffusion bonding is accommodated in the recess A and good diffusion bonding is performed, the diffusion bonding strength can be improved.

[Embodiment 2]
Embodiment 2 of the highly conductive object W1 according to the present invention will be described with reference to FIG. FIG. 2 shows a longitudinal section of the highly conductive workpiece W1. Since it is basically the same as the highly conductive workpiece W1 of the first embodiment, different points will be described. An annular projection P formed on the highly conductive workpiece W1 has an annular small top portion P1, a substantially vertical inner peripheral surface P2 ′, and an outer peripheral inclined surface P3. An inverted conical recess A is formed in the highly conductive workpiece W1 surrounded by the annular projection P. The recess A preferably has a volume that can accommodate almost all the plastic fluidized metal material of the annular projection P.

  The annular projection P according to the second embodiment has a conical opening angle with the inner peripheral surface P2 'being substantially vertical and the opening angle formed by the outer peripheral inclined surface P3, that is, the point where the extended lines of the outer peripheral inclined surface P3 intersect. Is an inclined surface within a range of 60 to 120 degrees, and therefore, the inner peripheral side is more easily plastically fluidized than the outer peripheral side of the annular projection P during diffusion bonding, and the plastic fluidized metal material of the annular projection P Can easily enter the recess A, so that almost all of the plastic fluidized metal material is accommodated in the recess A. Therefore, the highly conductive workpiece of the second embodiment can achieve the desired bonding strength by performing the diffusion bonding well in the annular surface area that is equal or closer to the base surface area P4 of the annular projection P. Can do. The highly conductive object of Embodiment 2 is suitable when it is desired to keep the applied pressure relatively small, or when the bonding strength may be relatively small.

[Embodiment 3]
Embodiment 3 of the highly conductive object W1 according to the present invention will be described with reference to FIG. FIG. 3 shows a cross section of the highly conductive workpiece W1. The first and second embodiments are suitable when the outer diameter of the annular projection P is approximately 10 mm or less, preferably 7 mm or less, but the third embodiment requires a large bonding strength, and an annular shape is required to meet the demand. This is suitable when the outer diameter of the projection P exceeds approximately 10 mm. Since the highly conductive object W1 of the third embodiment is basically the same as the highly conductive object W1 of the first and second embodiments, different parts will be described. The annular projection P formed on the highly conductive workpiece W1 has an opening angle formed by the top surface P1, the substantially vertical inner peripheral surface P2 ′, and the outer peripheral inclined surface P3, that is, the outer peripheral inclined surface P3. An outer peripheral inclined surface P3 having a relatively large inclination angle with a cone-shaped opening angle within a range of 60 to 120 degrees having a vertex at a point where the extension lines intersect. An annular inner peripheral groove A ′ is formed along the annular projection P in the highly conductive workpiece W1 surrounded by the annular projection P.

  The annular inner circumferential groove A ′ is formed to have a volume that can accommodate almost all the plastic fluidized metal material of the annular projection P. Accordingly, also in the third embodiment, the metal material of the annular projection P that is plastically fluidized by energization of the joining current easily enters the annular inner peripheral groove A ′ and is accommodated therein. The diffusion bonding between the object W1 and the object to be bonded W2 is performed in an annular base surface area P4 of the annular projection P that is substantially equal to the bonding side surface S1 of the highly conductive object W1. In the third embodiment, since the diameter of the annular projection P and the opening angle of the outer peripheral inclined surface P3 are larger than those in the first and second embodiments, the annular root surface area P4 of the annular projection P is set to be larger. Therefore, the third embodiment is suitable when it is desired to obtain a larger bonding strength than the first and second embodiments. In this case, naturally, it is necessary to increase the junction current and the applied pressure.

  The shapes of the annular projection P, the recess A, and the inner circumferential groove A ′ shown in the above first to third embodiments are examples, and are not limited to these shapes. For example, the annular projection P may be composed of a two-stage projection, that is, a first-stage projection that determines the bonding strength on the lower side and a second-stage projection that easily plastically fluidizes on the projection. Good. When the other workpiece W2 is made of the same metal material as the highly conductive workpiece W1, a low melting point such as a tin film having a relatively large resistance value is formed on the diffusion bonding surface of the workpiece W2. If the metal film is formed, diffusion bonding can be performed more easily. Further, when the other work piece W2 is made of a metal material such as stainless steel, brass, or iron having lower conductivity than the copper material or the aluminum material, at least the annular projection P of the highly conductive work piece W1. If a low melting point metal film as described above is formed in advance on the top surface P1, diffusion bonding can be performed more easily.

[Embodiment 4]
Next, an example of diffusion bonding of the highly conductive workpiece W1 including the annular projection P having the shape described in the second embodiment will be described with reference to FIG. A highly conductive object W1 having an annular small top surface P1, an almost vertical inner peripheral surface P2 ′, an annular projection P having an outer peripheral inclined surface P3, and a cylindrical recess A on the joint side S1. However, as shown in FIG. 4 (A), it is disposed on the lower bonding electrode 1, and the other object W2 is disposed so as to contact the annular projection P. The other workpiece W2 may be a copper material or an aluminum material, but may be stainless steel, brass, iron or the like having a lower conductivity than these. When the bonding electrode 2 on the upper side is lowered or the bonding electrode 1 is raised, pressure is applied between the highly conductive workpiece W1 and the other workpiece W2. This applied pressure is initially applied to a surface area corresponding to the top surface P1 of the projection P, and the junction current naturally flows through the projection P in a concentrated manner in the surface area corresponding to the top surface P1 of the projection P.

  Heat generated by the junction current flowing through the contact resistance between the top surface P1 of the annular projection P and the surface of the other workpiece W2 in contact with the top surface P1, and plastic fluidization is first generated from the top surface P1 of the annular projection P. At first, since the annular projection P protrudes from the joining side surface S1, the heat does not escape in the lateral direction. Therefore, heat generated by the resistance of the annular projection P also acts, and the metal material of the annular projection P is plastically fluidized. . The plastic fluidized metal material spreads in the lateral direction of the drawing by the applied pressure, enters the recess A, and is accommodated. Since almost all the metal material of the plastic projection annular projection P is accommodated in the recess A, in the state in which diffusion bonding is performed, as shown in FIG. The joint W2 comes into contact with at least the inner and outer surfaces of the annular projection P. At this time, the required pressure is applied to the annular projection P until just before the contact.

  Eventually, in this diffusion bonding, a junction current having a large current density flows from the beginning of energization of the junction current until the diffusion bonding is performed, and the required pressure is applied to the root surface of the annular projection P. In the region P4, diffusion bonding is performed between the root surface region P4 of the annular projection P and the workpiece W2 in contact therewith. In the highly conductive workpiece W1 of the present invention, the root surface area P4 of the annular projection P is an annular surface area, and an annular diffusion bonding surface substantially equal to the annular root surface area P4. Since diffusion bonding is performed at U, a large diffusion bonding surface can be obtained and a large bonding strength can be obtained. Diffusion bonding is not performed on the contact surface between the metal material accommodated in the recess A and the workpiece W2, and the function of substantially increasing the bonding strength is not performed. In this diffusion bonding process, the surface area of the workpiece W2 that comes into contact with the projection P of the highly conductive workpiece W1 is naturally fluidized by heat generation, and the highly conductive workpiece W1 and the workpiece W2 are joined. Both of them are plastically fluidized at the abutting portion, so that good diffusion bonding is performed between the highly conductive workpiece W1 and the workpiece W2. Specific examples capable of performing good diffusion bonding will be described later.

  Here, if the recess A is not formed in the highly conductive workpiece W1, and it is flat, as shown in FIG. 4C, the annular projection formed by plastic fluidization as described above. The metal material of P expands in the horizontal direction of the drawing by the applied pressure. Since there is no recess that accommodates the plastic fluidized annular projection P metal material, the plastic fluidized annular projection P metal material is raised on the joining side S1 of the highly conductive workpiece W1. Pw is formed. In the process as shown in FIG. 4C, the junction current having a large current density flows from the initial stage of energization of the junction current until the diffusion junction is performed, and the root plane area P4 of the annular projection P flows. This is a surface area in the middle of not reaching, and the surface area becomes an annular diffusion bonding surface Z.

  Considering that the annular projection P includes the top surface P1, the inner peripheral inclined surface P2, and the outer peripheral inclined surface P3, the area of the annular diffusion bonding surface Z is naturally larger than that of the diffusion bonding surface U in FIG. Since the effective diffusion bonding time is shortened as a result, the bonding strength is greatly reduced as compared with the bonding strength obtained with the highly conductive workpiece W1 of the present invention. When the state shown in FIG. 4C is reached, since the junction current and the applied pressure are dispersed in the deposited layer Pw, the junction current and the applied pressure per unit area are significantly reduced. Therefore, in the state shown in FIG. 4C, diffusion bonding does not substantially progress, and diffusion bonding is not substantially performed on the contact surface of the deposited layer Pw excluding the annular diffusion bonding surface Z, and the bonding strength is high. Does not substantially contribute to improvement. As described above, in the present invention, the annular projection P having a trapezoidal cross section is formed on the highly conductive workpiece W1, and the high conductivity is obtained in a surface area substantially equal to the root surface area P4 of the annular projection P. Since the diffusion bonding between the bonding object W1 and the other bonding object W2 is performed, a large bonding strength can be obtained and the flatness of the bonding surface can be improved.

[Embodiment 5]
Next, FIG. 5 showing an example of a capacitor-type bonding apparatus suitable for realizing diffusion bonding between a highly conductive object W1 formed with such an annular projection P and another object W2. A specific diffusion bonding embodiment 5 will be described. The high-conductivity object W1 and the other object W2 described above are disposed between the bonding electrode 1 and the bonding electrode 2 as shown in FIG. A support mechanism 4 is fixed to a floor or base member 3 on which the joining device is installed. A pressurizing mechanism 5 made of a cylinder device or the like is attached to the support mechanism 4, and a movable block 6 made of a metal material is attached to the tip of the pressurizing mechanism 5. A pressurizing auxiliary member 7 such as a spring or an electromagnetic pressurizing device is provided between the movable block 6 and the support member 8 to perform an auxiliary role of improving the pressurization response of the joining electrode. The pressure auxiliary member 7 has a shape in which an elastic force is superimposed on the pressure applied by the pressure mechanism 5, and a pressure in which the elastic force is superimposed is applied between the highly conductive workpiece W <b> 1 and the workpiece W <b> 2. .

  The function of the pressure auxiliary member 7 is large in diffusion bonding of the highly conductive workpiece W1. Here, the support member 8 is made of a metal material such as copper which is directly or indirectly coupled to the lower end portion of the pressure assisting member 7 and also functions as a power feeding portion. The upper joining electrode 2 is supported by the support member 8, and the lower joining electrode 1 exists at a position facing the joining electrode 2. An L-shaped intermediate connecting member 9 is fixed to the movable block 6 located at a height that is not affected by the expansion and contraction of the pressure assisting member 7. A flexible first flexible conductive member 10 is provided to connect between the support member 8 and the L-shaped intermediate connection member 9, and a second flexible conductor is provided between the L-shaped intermediate connection member 9 and one power supply conductor 12. They are connected by the conductive member 11. The joining electrode 1 and the joining electrode 2 are made of brass, which is a copper alloy, for example.

  The secondary winding N2 of the junction transformer 14 is connected between the power supply conductor 12 and the other power supply conductor 13 connected to the bonding electrode 1, and the primary winding N1 magnetically coupled thereto is connected to the primary winding N1. A discharge circuit 15 such as an inverter circuit or a semiconductor switch circuit is connected. Connected to the discharge circuit 15 are an energy storage capacitor 16 and a charging circuit 17 for charging the capacitor. In the diffusion junction, most of the junction current that contributes to the junction is the current from the rise to the vicinity of the peak value. Therefore, in the diffusion junction of the fourth embodiment, the time for the junction current to rise to the vicinity of the peak value is about 10 ms or less. It is preferable that it is 7 ms or less. In this bonding apparatus, the upper bonding electrode 2 is supported by the support member 8 that can move up and down with a slight external force, and at the same time, the pressure assisting member 7 that can provide highly responsive elastic force. Therefore, the bonding electrode 2 can immediately respond to a slight change in the applied pressure between the bonding electrode 2 and the workpiece W2 due to plastic fluidization of the annular projection P. Symbols 18 to 20 represent three-phase AC input terminals.

  Next, a method of diffusion bonding the highly conductive object W1 shown in FIG. 1 or 2 and another object W2 using this bonding apparatus will be described. First, the highly conductive workpiece W1 is placed on the lower joining electrode 1, and the workpiece W2 is placed thereon. In this state, the pressurizing mechanism 5 shown in FIG. 5 operates downward, and accordingly, the entire upper joining head composed of the movable block 6, the pressurizing auxiliary member 7, the support member 8, and the upper joining electrode 2 is lowered. Then, the bonding electrode 2 applies a required pressure to the workpiece W2. At this time, a partial surface area of the lower surface of the workpiece W2 contacts the top surface P1 of the annular projection P of the highly conductive workpiece W1. The joining electrode 2 and the support member 8 stop at that position, but as the pressurizing mechanism 5 further descends, the pressurizing auxiliary member 7 is contracted, and the movable block 6 is moved together with the pressurizing mechanism 5. Descend. Further, as the movable block 6 descends, the second flexible conductive member 11 bends and the first flexible conductive member 10 moves together with the movable block 6, so that the support member 8 is stopped as described above. Thus, when the movable block 6 is lowered while contracting the pressure assisting member 7, it is deformed from the initial state. However, as described above, since the first flexible conductive member 10 is made to be more easily bent than the second flexible conductive member 11, resistance to movement between the support member 8 and the upper joining electrode 2 is reduced. The Therefore, the responsiveness of the bonding electrode 2 on the upper side is improved.

  In this manner, the pressure assisting member 7 contracts during the downward movement of the pressure mechanism 5 and the pressure between the bonding electrode 1 and the bonding electrode 2 increases at a predetermined inclination. During the operation, or when the applied pressure becomes substantially constant, the discharge circuit 15 is turned on, and the charge already stored in the energy storage capacitor 16 by the charging circuit 17 is transferred to the primary of the junction transformer 14. Release to winding N1. Along with this, a large current is generated in the secondary winding N2 having one or two turns, which has a significantly smaller number of turns than the primary winding N1, and is sandwiched between the junction electrode 1 and the junction electrode 2. A steep pulsed junction current flows through the highly conductive workpiece W1 and the workpiece W2.

  The pulse-like junction current as described above is first concentrated on the top surface P1 of the annular projection P2 of the highly conductive workpiece W1 and the surface area of the workpiece W2 in contact therewith for a short time. Flowing. Since the junction current flowing through the annular projection P has a high current density, the annular projection P starts plastic fluidization at the top surface P1 due to heat generated by the contact resistance at the top surface P of the projection P, and the annular projection P Since the heat generated in the projection P2 is not substantially transferred in the lateral direction, the temperature of the annular projection P2 is raised and plastic fluidized. As described above, the plastic fluidized metal material of the annular projection P2 enters the recess A by the applied pressure and is accommodated. This is because the pressure assisting member 7 always applies an elastic force to the upper joining electrode 2, that is, a pressure including elasticity is applied between the highly conductive object W <b> 1 and the object W <b> 2. Since it is applied, it is performed promptly, and diffusion bonding can be performed in a short time of about 10 ms or less when the bonding current rises to the vicinity of the peak value, and diffusion bonding with high bonding strength is possible.

  The faster the pressure assisting member 7 has a higher response speed, the shorter the pulse width of the pulse junction current, that is, the current energy is concentrated in a short time between the highly conductive workpiece W1 and the workpiece W2. Even a material having a very good thermal conductivity such as a copper material can be plastically fluidized to a preferable state, and this can be performed between the highly conductive objects to be bonded or between the highly conductive objects to be bonded and other materials. This is one of the reasons why a satisfactory diffusion bonding can be achieved with an object to be bonded made of a metal material. In addition, this diffusion bonding method is not limited to diffusion bonding between highly conductive objects to be bonded or between a highly conductive object to be bonded and an object to be bonded made of another metal material, other metal materials, for example, normal steel plates. It can be applied to the same or different metal materials such as stainless steel members and steel plates, and satisfactory diffusion bonding results can be obtained. Further, the highly conductive object to be joined is not limited to a plate-like member, and high joint strength can be obtained even in various shapes such as a pipe shape, a round bar shape, and a square bar shape.

It is a figure which shows the highly conductive to-be-joined object which concerns on Embodiment 1 of this invention. It is a figure which shows the cross section of the highly conductive to-be-joined object which concerns on Embodiment 2 of this invention. It is a figure which shows the cross section of the highly conductive to-be-joined object which concerns on Embodiment 3 of this invention. It is a figure for demonstrating the diffusion bonding method which concerns on this invention. It is a figure which shows an example of the actual joining apparatus for implement | achieving the concrete diffusion bonding method which concerns on this invention.

Explanation of symbols

W1... Highly conductive object W2. Another object to be bonded P... Annular projection P1... Top surface of projection P P2 .. inner peripheral inclined surface of projection P P2 '. P inner peripheral surface P3 ··· An outer peripheral inclined surface of the projection P P4 ··· A base surface area of the projection P Pw ··· a deposition layer of the projection P U · · · diffusion bonding surface region Z · · · diffusion bonding surface region S1 ... Joint side surface of highly conductive workpiece W1 A ... Recess A '... Annular inner circumferential groove 1 ... Lower side joining electrode 2 ... Upper side joining electrode 3. ··· Base member 4 ··· Support mechanism 5 ··· Pressurizing mechanism 6 ··· Movable block 7 · · · Pressurizing auxiliary member 8 · · · Support member 9 · · · L-shaped intermediate connection member 10 ···・ First flexible conductive member 11... Kishiburu conductive members 12, 13 ... feeding conductor 14 ... bonding transformer 15 ... discharge circuit 16 ... energy storage capacitor 17 ... charging circuit 18-20 ... 3-phase AC input terminal

Claims (6)

A highly conductive object that is diffusion-bonded with another object to form a diffusion bonding surface, and the high-conductive object includes an annular projection that protrudes from the bonding side surface.
The central surface area surrounded by the annular projection accommodates the metal material obtained by plastic fluidization of the annular projection when the highly conductive object to be bonded and the other object to be bonded are diffusion bonded. Provided with a recess or inner circumferential groove,
The recess or inner circumferential groove has a depth that is lower than the bonding side surface of the highly conductive workpiece.
A highly conductive object to be bonded, wherein a base area of the projection is the diffusion bonding area. In claim 1,
The highly conductive object to be bonded is copper or a copper alloy, or aluminum or an aluminum alloy. In claim 1 or claim 2,
An opening angle of a longitudinal section of the annular projection is in a range of 60 to 120 degrees. A junction current is passed between a highly conductive object having an annular projection protruding from the joining side surface and another object to be bonded, and the highly conductive object and the other object to be bonded are diffusion bonded. A diffusion bonding method for forming a diffusion bonding surface,
The joining current is applied in a state where a pressure is applied between the highly conductive object to be joined and the other object to be joined so that the base surface area of the annular projection becomes the diffusion joining surface area. A diffusion bonding method for a highly conductive object to be bonded. In claim 4,
A diffusion bonding method for a highly conductive object to be bonded, wherein the bonding current is a pulsed current having a time required for the current to rise to a peak value of 10 ms or less. In claim 4 or claim 5,
The pressurizing force is a pressure in which an elastic force is superimposed, and a high conductive covering is applied to the diffusion bonding surface without being affected by the plastic fluidized annular projection. Diffusion bonding method for joints.

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