JP2013214519A - Method of manufacturing joint structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint structure for thermally calk-joining a coated copper wire and a copper terminal, having suitable mechanical reliability.SOLUTION: The method of manufacturing a joint structure includes a step for forming a joint structure by calk-joining a strip copper terminal subjected to tin plating to a rod-like copper wire coated with a resin insulator, a step for fusing and removing the coating by holding the joint structure from both side by means of two electrodes and then applying a voltage thereto, and a step for compressing the copper wire until the diameter is reduced to 55-65% of initial diameter, by electrifying the joint structure while pressing from both sides by means of two electrodes, following the fusing and removing step.

Description

  The present invention relates to a joint structure that requires good mechanical quality, and in particular, a copper wire coated with a resin insulator, and a strip-shaped copper terminal disposed so as to surround the copper wire. It is related with the structure of the junction part which carried out the heat caulking joining.

  Bonding part that heats and joins a copper wire covered with a resin insulator and a strip-shaped copper terminal that surrounds the copper wire in the connection process and terminal bonding process of motors, speakers, etc. Structure is used. For this heat caulking, a method called fusing is used. The coated copper wire cannot be welded by ordinary resistance welding because its surface is insulated. Therefore, after crimping so that a copper terminal may be wound around a copper wire, a copper terminal is inserted | pinched with a pair of electrodes, a 1st electric current and a 2nd electric current are sent between electrodes, and it pressurizes, heating. Thereby, the coating of the copper wire is melted and the core wire is exposed, and the copper wire and the copper terminal are directly joined. In such a fusing method, no coating removal work is required, and no screws or adhesives are used. Therefore, the fusing method is used as a low cost and high production efficiency joining method.

  Conventionally, structural and manufacturing processes have been studied to ensure the reliability of the fusing joint. For example, Patent Document 1 proposes a configuration in which a plurality of wires are stranded and connected by a plurality of hooks. Further, Patent Document 2 proposes a structure in which the shape of the terminal is notched and the amount of collapse of the terminal and the wire is stabilized.

Japanese Patent Laid-Open No. 5-38583 JP 2000-348785 A

  However, although such a structural device has been seen in the past, there has been no provision regarding what kind of state is desirable mechanically and electrically as a bonding interface after heat caulking and high reliability. Even if bonding is performed using the structure of the prior art, a highly reliable bonding state cannot be obtained unless the state of the bonding interface is controlled.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a joint structure in which a coated copper wire and a copper terminal are joined by heat caulking and having suitable mechanical reliability.

  In order to solve the above-described problems and achieve the object, the manufacturing method of the joint structure of the present invention includes a strip-shaped copper terminal obtained by tin-plating a rod-shaped copper wire coated with a resin insulator. After the step of caulking to form a joint structure, the step of melting and removing the coating by sandwiching the joint structure between two electrodes from both sides and applying a voltage, and the step of melting and removing, the joint portion And a step of pressing the structure while pressing it with two electrodes from both sides to pressurize the copper wire to 55 to 65% of the initial diameter.

  According to the joint structure according to the present invention, a joint structure that is mechanically and electrically suitable and has high reliability can be obtained.

It is a perspective view which shows the mode of the copper terminal wound around the copper wire which shows embodiment of the junction part structure concerning this invention, and being crimped. It is the schematic diagram seen from the arrow A direction of FIG. 1 which shows the procedure in which a copper terminal is wound around a copper wire and crimped. It is a schematic diagram which shows a mode that a voltage is applied while a junction structure is pressurized and a 1st electric current flows. It is a schematic diagram which shows a mode that a pressure is further applied and a 2nd electric current flows while a copper terminal is further pressurized by the junction part structure, and a copper wire is crimped to a copper wire. 3 is an electron micrograph of a cross section of a joint portion of the joint portion structure of Example 1. FIG. 2 is a view showing a composition of tin at a bonding interface in Example 1. FIG. It is a figure which shows the electricity supply profile in Example 1. FIG. It is a figure which shows the position of the junction interface of a junction part structure, and a terminal base part. It is a figure which shows the state which set up the tension test. 2 is a view showing a composition of tin at a bonding interface in Example 1. FIG. It is a schematic diagram which shows a mode that the vibration load by a vibration degradation apparatus is given. 6 is an electron micrograph of a cross section of a joint portion of a joint structure of Comparative Example 1. FIG. 4 is a view showing a composition of tin at a bonding interface in Comparative Example 1. FIG. 7 is an electron micrograph of a cross section of a joint portion of a joint structure of Comparative Example 2. FIG. 6 is a view showing a composition of tin at a bonding interface in Comparative Example 2. FIG. FIG. 4 is a view showing a composition of tin at a bonding interface in Example 2. It is a figure which shows the electricity supply profile in Example 2. FIG. It is a figure which shows the stress-displacement characteristic (after an initial stage, vibration deterioration) of the junction part in Example 2. FIG. 4 is a view showing a composition of tin at a bonding interface in Example 3. FIG. It is a figure which shows the electricity supply profile in Example 3. FIG. It is a figure which shows the stress-displacement characteristic (after an initial stage, vibration degradation) of the junction part in Example 3. FIG. It is a figure which shows the composition of the tin of the joining interface of Example 4. It is a figure which shows the electricity supply profile in Example 4. FIG. It is a figure which shows the stress-displacement characteristic (after an initial stage, vibration degradation) of the junction part in Example 4. FIG. 6 is a view showing a composition of tin at a bonding interface in Example 5. FIG. It is a figure which shows the electricity supply profile in Example 5. FIG. It is a figure which shows the stress-displacement characteristic (after an initial stage, vibration degradation) of the junction part in Example 5. FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a joint structure according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
[Embodiment]

  FIG. 1 is a perspective view showing a state of a copper terminal wound around a copper wire and showing an embodiment of the joint structure according to the present invention. In the joint structure 100 of the present embodiment, a long bar-shaped copper wire (first joining member) 1 provided with a coating 1b that melts by heating, and tin plating is applied to the copper wire 1 to be heat staked. It has a long thin plate-like copper terminal (second joining member) 2. The copper terminal 2 is wound around the copper wire 1 so that the end of the copper terminal 2 is bent into a U-shape and surrounds the copper wire 1. The joint structure 100 composed of the copper wire 1 and the copper terminal 2 joined by such a structure is used for connection parts and terminal joint parts such as motors and speakers.

  FIG. 2 is a schematic view seen from the direction of arrow A in FIG. 1 showing a procedure in which the copper terminal 2 is wound around the copper wire 1 and caulked. FIG. 3 is a schematic diagram showing a state in which a first current flows when a voltage is applied while the junction structure 100 is pressurized. FIG. 4 is a schematic view showing a state in which a second current flows when a voltage is applied while the copper terminal 2 is crimped to the copper wire 1 by being further pressurized to the joint structure 100. The copper wire 1 is configured by covering a copper wire core 1a with a resin insulator such as polyimide or polyurethane. On the other hand, the copper terminal 2 is configured by tin-plating a strip-shaped core material. In the joint structure 100 having such a configuration, the copper wire 1 cannot be welded by normal resistance welding because the surface thereof is insulated by the coating 1b. Therefore, as described in the background art, a method called fusing that heats the copper wire 1 and the copper terminal 2 is used. In this method, as shown in FIG. 2, after crimping a copper terminal 2 on a copper wire 1, the pressure is applied while heating.

  The above construction method is divided into two steps. First, as shown in FIG. 3, as shown in FIG. 3, a joint structure 100 in which a copper terminal 2 is crimped on a copper wire 1 is sandwiched between two electrodes 30, 30, and a power source 20 is connected between both electrodes 30, 30. Apply a voltage of. At this time, first, a desired current (first current) flows as shown by an arrow B in FIG. Then, the coating 1b of the copper wire 1 is melted by Joule heat generated by the first current. Thereby, the coating 1b is removed, the wire core wire 1a is exposed, and the wire core wire 1a and the copper terminal 2 are in direct contact.

  About the next process, as shown in FIG. 4, it presses further from both sides with the two electrodes 30 and 30 with respect to the junction structure 100 from which the coating 1b of the copper wire 1 was removed. By this pressurization, the copper wire 1 and the copper terminal 2 are crushed, and the copper wire 1 and the copper terminal 2 are brought into close contact with each other. At this time, a desired current (second current) flows between the copper wire 1 and the copper terminal 2 as indicated by an arrow C in FIG. Then, the diffusion of the bonding interface between the copper wire 1 and the copper terminal 2 is promoted by the Joule heat generated by the second current.

  And the junction part structure 100 of this Embodiment is an integrated value which the tin composition ratio of the interface of the copper wire 1 and the copper terminal 2 after heat caulking joining integrated with the distance of the orthogonal | vertical direction of the interface. 4.95 atomic percent micrometer. Due to this feature, the joint structure 100 according to the present embodiment has suitable mechanical reliability.

  For example, in the case of a copper wire 1 used for a motor lead wire or coil winding, the diameter is about 0.2 to 2.0 mm, and the thickness of the copper terminal 2 is about 0.4 to 3.0 mm. is there. Moreover, the film thickness of tin plated mainly for the purpose of preventing rust of the copper terminal 2 is about 1 to 5 micrometers.

  In order to obtain the desired interface state (interface composition) as described above depending on the dimensions of the copper wire 1 and the copper terminal 2, the melting point of the coating material, the thermal conductivity coefficient, etc., the current-carrying heating amount at the time of bonding is determined by the current. It is necessary to adjust the value and energization time. These parameter values need to be optimized in each process. However, the important point is how the composition of the joining interface is finished after joining, and if the desired tin composition ratio is obtained, the dimensions of the member, the type of coating material, and the current heating The joining conditions are not particularly limited to the embodiment.

The configuration and effects will be described below with reference to specific examples and comparative examples.
[Example 1]

  FIG. 5 is an electron micrograph of a cross-section of the joint portion of the joint structure of Example 1. In FIG. 5, the copper wire 1 was coated with a resin insulator before bonding, but after bonding, the coating was melted and vaporized, and the bonding interface D between the copper terminal 2 and the copper wire 1 was made directly between metals. It can be seen that they are joined.

  The composition of the bonding interface D in FIG. 5 was measured as follows. The cross section of sample 101 is embedded and polished, and conductive treatment (gold sputtering) is performed, and the composition line analysis of the main components copper and tin is performed by Auger Electron Spectroscopy (AES), which can measure a sub-micron micro area. It was. The composition line analysis was performed in the measurement direction (direction perpendicular to the interface) indicated by an arrow F with the region E (longitudinal center position of the interface) E enclosed by a broken line in FIG. The measurement location was determined from the center of the long diameter of the copper wire 1.

  6 is a view showing the composition of tin at the bonding interface in Example 1. FIG. In FIG. 6, the vertical axis represents the tin composition ratio (unit: atomic percent), and the horizontal axis represents the distance across the interface (unit: μm). In this example, attention was focused on the composition ratio (composition distribution) G of tin at the center position of the interface shown in FIG. The AES measurement apparatus used was SMART-200 manufactured by ULVAC-PHI, and the AES measurement conditions were primary incident electrons of 15 kV-10 nA and an etching rate of about 6 nm / min.

  An amount (integrated value) H obtained by integrating the tin composition distribution G shown in FIG. 6 by the distance in the direction across the interface was determined and defined as an integrated composition value, which was used as an index of the remaining amount of tin at the bonding interface. The integrated value H of the composition in FIG. 6 was 3.53 (unit: atomic percent · μm, the same applies hereinafter).

  The sample 101 of this example was manufactured by the following material and bonding process according to the procedure shown in FIGS. 1 and 2 of the embodiment. First, a copper terminal (plate thickness 1 mm) 2 having copper as a base material with tin plating (thickness of about 3 μm) on the surface is bent into a U-shape, and copper is used as the wire core wire 1a on the inner side. A coated copper wire (diameter φ 1.2 mm) 1 was placed. And from the outer surface of the copper wire 1, it was preliminarily formed by mechanically caulking with a forming jig (not shown).

  Next, as shown in FIGS. 3 and 4 of the embodiment, the current-carrying electrode 30 (made of tungsten) is pressed with a force of about 350 N from both sides of the outer surface portion of the copper terminal 2, and the profile of FIG. 1 current I1 and 2nd current I2 are applied, and the position of the electrode is controlled so that the collapse amount of the copper wire 1 is about 60% of the initial diameter (1.2 mm × 0.6 = 0.72 mm). The pressure was applied. After the energization was completed, the energization electrode 30 was cooled to a sufficiently low temperature (Cu—Sn eutectic temperature of 227 ° C. or lower) while water-cooling the energization electrode 30 while maintaining the pressure applied by the energization electrode 30. The cooling time after the end of energization was 500 ms.

  The tensile test of the sample 101 was performed as follows. A sample 101 composed of the copper wire 1 and the copper terminal 2 is arranged as shown in FIG. 9, the lower end portion of the sample is fixed to the wire lower gripping chuck 202, and the upper end portion is engaged with the fixing jig 204. The sample 101 was urged to move upward, and a tensile load was applied to the sample 101. As the tensile test apparatus, Shimadzu Autograph DCS-25T was used, and the tensile speed was 20 mm / min. By the above method, a load was applied until the joint structure of the sample 101 was broken, and a load-displacement characteristic (initial stress-displacement characteristic) 41 before vibration deterioration as shown in FIG. 10 was obtained. Here, the maximum value of the load was defined as a tensile strength of 40.

  Next, a vibration load is applied to a sample equivalent to the sample 101 subjected to the tensile test before vibration deterioration by the method described later, and then a tensile test is performed to determine load-displacement characteristics (stress-displacement characteristics after vibration deterioration). 42 was obtained. In the sample of this example, there is no significant change in the load-displacement characteristic before and after the vibration deterioration, and, of course, the joint interface D (FIG. 8) and the terminal base J ( There was no breakage of the copper wire 1 in FIG. For this reason, even when the product is put on the market and is subjected to vibration and shock disturbances, it is expected that good bonding quality equivalent to that at the time of shipment is obtained.

  Even when the variation of tin plating thickness (1 to 5 μm) was taken into account and n = 24 was repeated, the range of the tin composition integrated value was 2.64 to 4.95. All of these samples had the same mechanical quality as the representative sample.

[Comparative Example 1]
Hereinafter, the effect of Example 1 is demonstrated by contrast with a comparative example. Generally, when joining the copper wire 1 and the copper terminal 2 of a conductor, in order to obtain initial strength, the state where an interface becomes a metal bond of tin and copper or copper and copper is preferable. For example, in Patent Document 3 (Japanese Patent Application Laid-Open No. 11-176552), a structure in which the tin of the copper terminal 2 and the copper of the copper wire 1 are metallicly bonded by heat diffusion under current conduction to prevent a decrease in strength. It is said.

  However, such a joint structure that excessively energizes and heats and crushes the copper wire 1 excessively, especially when subjected to vibration and shock disturbance in the market, especially at the terminal base J (FIG. 8). It turned out that it became easy to fracture | rupture and it turned out that reliability falls remarkably.

  In order to simulate a state in which a product having the joint structure of this comparative example 1 is put on the market and receives vibration and impact from the outside, a spring constant k and mass m are applied to the copper terminal 2 of the sample 101 as shown in FIG. The lower end of the sample 101 is fixed to the vibrator 206, and is vibrated as indicated by an arrow L from the outside to give a vibration load. The vibration conditions were a vibration acceleration of 8G, a vibration time of 5 minutes, and a vibration frequency matched with the eigenvalue of the system composed of the sample 101 and inertia.

  12 is an electron micrograph of a cross section of the joint portion of the joint structure of Comparative Example 1. FIG. FIG. 13 is a view showing the composition of tin at the bonding interface in Comparative Example 1. In the joint structure 108 as shown in FIG. 12, in order to obtain a strong metal joint at the joint interface, the copper wire 1 is crushed to 50% or less of the initial diameter, and the terminal base portion J (FIG. 8). ) Wire diameter has also been reduced accordingly. As shown in FIG. 13, in the composition showing the structure of this comparative example 1, tin is mechanically pushed out or diffused from the joint, and is not detected at all (tin composition integral value 0.00). In such a joint structure 108, the copper wire 1 was broken at the terminal root portion J (FIG. 8) during application of the same vibration load as in Example 1. Since the fracture was a completely defective product, the tensile test of the sample was omitted.

  Even when the variation of tin plating thickness (1 to 5 μm) was taken into consideration and n = 24 was repeated, the range of the tin composition integral value was 0.00 to 0.10. All of these samples were broken at the terminal base J (FIG. 8) during application of the vibration load in the same manner as the representative sample. As described above, a suitable bonded state must not only have a high initial strength, but also take into account the effects of vibration and shock disturbances. On the contrary, when the current heating is insufficient and the heat caulking is insufficient and the joint strength is not sufficiently obtained, the joint interface D (see FIG. It was found that in 8) the fracture was easily caused and the reliability was remarkably lowered.

[Comparative Example 2]
FIG. 14 is an electron micrograph of a cross section of a joint portion of the joint structure of Comparative Example 2. FIG. 15 is a view showing the composition of tin at the bonding interface in Comparative Example 2. In the joint structure 109 as shown in FIG. 14, the energization heating amount is insufficient, and the copper wire 1 is crushed only about 70% of the initial diameter. As shown in FIG. 15, in the composition showing the structure of the present comparative example 2, a relatively large number of tin composition integral values are detected (tin composition integral value 9.25). Such a joint structure 109 was broken at the joint interface D (FIG. 8) while applying the same vibration load as in Example 1. Since the fracture was a completely defective product, the tensile test of the sample was omitted.

  Even when n = 24 was repeated in consideration of the variation in tin plating thickness (1 to 5 μm), the range of the tin composition integral value was 6.48 to 11.1. All of these samples, like the representative sample, fractured at the bonding interface D (FIG. 8) while applying a vibration load.

  In Patent Document 3, a thermal cycle test is carried out as an evaluation of reliability. However, when the base material of the terminal and the wire (both are copper) are the same, there is a difference in linear expansion coefficient at the joint interface. Therefore, it is not suitable for evaluating the mechanical strength of the joint itself.

  Furthermore, in Patent Document 3, the electrical resistance of the joint is measured as a reliability index. However, since electrical continuity can be obtained even when the interface is merely in contact, the sensitivity and accuracy of discrimination are low. It is inappropriate as an index of reliability. If the wire coating is completely melted and the metals are bonded with mechanical strength, electrical continuity is obtained with a sufficiently low electrical resistance. Evaluation was performed. That is, for samples that do not have a complete break as in Comparative Examples 1 and 2, by performing a tensile test on the samples before and after vibration degradation, it is superior or inferior by seeing whether there is a decrease in strength before and after vibration degradation. Was evaluated.

  The relationship between the amount of energization heating and the amount of tin at the time of joining, and the relationship between the amount of energization heating and the mechanical quality of the joint can be considered as follows. In the state where the heat input due to energization heating at the joint is insufficient, the insulation coating remains at the joint interface, so the joint area is not sufficient, or the mutual diffusion of metals at the joint interface is insufficient. The bonding strength is not sufficiently obtained.

  The increase in heat input due to energization overheating 1) sufficiently removes the insulation coating, 2) promotes physical removal and diffusion of tin at the joint interface, reduces the tin content at the center of the interface, and 3) By accelerating the collapse of the wire, the conductive contact area is increased and the interdiffusion of copper at the bonding interface is promoted. These increase the mechanical strength at the joint interface as the heat input increases.

  However, if the amount of heat input due to energization overheating exceeds the upper limit, 1) tin at the center of the interface is almost completely removed, 2) the wire collapse becomes excessive at the same time, the terminal root becomes thin, and 3) Increase in particle size and work hardening by promoting recrystallization growth are promoted. These are factors that reduce the fatigue strength of the terminal base. In other words, the tin content at the center of the joint interface and the mechanical quality of the joint can be correlated by the common cause of heat input by energization heating.

As described above, it is possible to know the degree of energization and heating amount to the joint part according to how much tin initially plated on the terminal remains after joining, and as a result, the mechanical quality of the joint part can be determined. It was found that it can be defined by the remaining amount of.
[Example 2]

  FIG. 16 is a diagram showing the composition of tin at the bonding interface in Example 2. The composition integral value of the composition shown in FIG. 16 was 1.80. This example was realized by the following bonding process. The joint structure of the present embodiment has the same configuration as that of the first embodiment. The applied pressure of the energizing electrode is about 460 N, the energization is performed according to the profile of FIG. 17, and the collapse amount of the copper wire has the initial diameter. The electrode was pressed while controlling the position of the electrode so that it was about 60% (0.72 mm). After completion of energization, the electrode was cooled with water while cooling the electrode until the temperature of the copper terminal was sufficiently low. Other configurations are the same as those of the first embodiment.

The load-displacement characteristics of the sample before and after vibration deterioration in this example are as shown in FIG. 18, and there was no significant change in tensile strength before and after vibration deterioration. There was no breakage during vibration deterioration. 24 samples (n = 24 ranges) were analyzed under the same conditions as above when there was variation (1-5 μm) in tin plating thickness. As a result, the range of the tin composition integrated value was 1.25 to 2.35. In any sample, the same mechanical quality as that of the representative sample could be obtained.
[Example 3]

  FIG. 19 is a view showing the composition of tin at the bonding interface of Example 3. The composition integral value of the composition shown in FIG. 19 was 1.72. This example was realized by the following bonding process. The joint structure of the present embodiment has the same configuration as that of the first embodiment. The applied pressure of the energizing electrode is about 350 N, and energization is performed according to the profile of FIG. 20, and the collapse amount of the copper wire has the initial diameter. Pressurization was performed while controlling the position of the electrode so as to be about 60%. After completion of energization, the electrode was cooled with water while cooling the electrode until the temperature of the copper terminal was sufficiently low. Other configurations are the same as those of the first embodiment.

The load-displacement characteristics of the sample before and after vibration deterioration in this example are as shown in FIG. 21, and there was no significant change in tensile strength before and after vibration deterioration. There was no breakage during vibration deterioration. 24 samples (n = 24 ranges) were analyzed under the same conditions as above when there was variation (1-5 μm) in tin plating thickness. As a result, the range of the tin composition integral value was 1.54 to 2.32. In any sample, the same mechanical quality as that of the representative sample could be obtained.
[Example 4]

  FIG. 22 is a diagram showing the composition of tin at the bonding interface of Example 4. The composition integral value of the composition shown in FIG. 22 was 0.48. This example was realized by the following bonding process. The joint structure of the present embodiment has the same configuration as that of the first embodiment, and the diameter of the copper wire is φ1.5 mm. The pressure applied to the energizing electrode was about 350 N, and energization was performed with the profile shown in FIG. 23, and the electrode was pressed while controlling the position of the electrode so that the amount of collapse of the copper wire was about 55% of the initial diameter. After completion of energization, the electrode was cooled with water while cooling the electrode until the temperature of the copper terminal was sufficiently low. Other configurations are the same as those of the first embodiment.

The load-displacement characteristics of the sample before and after vibration deterioration in this example are as shown in FIG. 24, and there was no significant change in tensile strength before and after vibration deterioration. There was no breakage during vibration deterioration. 24 samples (n = 24 ranges) were analyzed under the same conditions as above when there was variation (1-5 μm) in tin plating thickness. As a result, the range of the tin composition integral value was 0.25 to 0.62. In any sample, the same mechanical quality as that of the representative sample could be obtained.
[Example 5]

  FIG. 25 is a view showing the composition of tin at the bonding interface in Example 5. The composition integral value of the composition shown in FIG. 25 was 0.57. This example was realized by the following bonding process. The joint structure of the present embodiment has the same configuration as that of the first embodiment, and the diameter of the copper wire is φ1.0 mm. The pressure applied to the energizing electrode was about 350 N, and energization was performed with the profile shown in FIG. 26. The electrode was pressed while controlling the position of the electrode so that the amount of collapse of the copper wire was about 65% of the initial diameter. After completion of energization, the electrode was cooled with water while cooling the electrode until the temperature of the copper terminal was sufficiently low. Other configurations are the same as those of the first embodiment.

  The load-displacement characteristics of the sample before and after vibration deterioration in this example are as shown in FIG. 27, and there was no significant change in tensile strength before and after vibration deterioration. There was no breakage during vibration deterioration. 24 samples (n = 24 ranges) were analyzed under the same conditions as above when there was variation (1-5 μm) in tin plating thickness. As a result, the range of the tin composition integral value was 0.45 to 0.86. In any sample, the same mechanical quality as that of the representative sample could be obtained.

  Table 1 compares the integrated composition values from the composition distributions of the joints in Examples 1 to 5 and Comparative Examples 1 and 2 collectively. According to Table 1, the range of the integral composition value of tin having a suitable bonded state has a lower limit (lower limit 0.25 of Example 4) and an upper limit (upper limit 4.95 of Example 1). I understood. If the integral composition value of tin is below the lower limit, the terminal root wire during vibration deterioration is likely to break, and if the integral composition value of tin exceeds the upper limit, It was found that breakage tends to occur.

  The joint structure of the present invention is suitable for application to a joint structure that requires good mechanical quality, and is particularly applicable to a joint structure in which a coated copper wire and a copper terminal are joined by heat caulking. Is the best.

  DESCRIPTION OF SYMBOLS 1 Copper wire (1st joining member), 1a Wire core wire, 1b Coating | cover (insulator), 2 Copper terminal (2nd joining member), 20 Power supply, 30 Current supply electrode, 40 Tensile strength, 41 Initial stress- Displacement characteristics, 42 Stress-displacement characteristics after vibration degradation, 100 Joint structure (Embodiment 1), 101 samples, 108 Joint structure (Comparative example 1), 109 Joint structure (Comparative example 2), 202 Lower part of wire Gripping chuck, 204 fixing jig, 206 vibrator, I1 first current, I2 second current.

Claims (2)

A step of forming a joint structure by caulking a strip-shaped copper terminal plated with tin on a rod-shaped copper wire coated with a resin insulator;
Melting and removing the coating by sandwiching the joint structure between two electrodes from both sides and applying a voltage;
After the melting and removing step, applying the current while pressing the joint structure with two electrodes from both sides, and pressurizing until the copper wire is 55 to 65% of the initial diameter;
A method for manufacturing a joint structure, comprising: The method for manufacturing a joint structure according to claim 1, wherein the resin insulator is one of polyimide and polyurethane.