JOINT OF COPPER TERMINAL AND ALUMINIUM CONDUCTOR AND PLASMA WELDING METHOD THEREFOR

Abstract

Provided is a joint of a copper terminal and an aluminum conductor. A copper terminal connecting member of the joint is connected to a conductive core of the aluminum conductor by means of a transition welding layer, and the joint can also be provided with a reinforcing welding layer. Further provided is a method for preparing the joint using plasma arc welding. According to the invention, the connection portion of the copper terminal with the aluminum conductor is filled with solder in a plasma arc welding manner, such that copper and aluminum are connected by means of the solder. Damage to an aluminum oxide layer during welding increases the conductivity and can also isolate the copper terminal and the aluminum conductor, thus preventing an electrochemical reaction between the copper and the aluminum.

Claims

1. A joint of a copper terminal and an aluminum wire, wherein the copper terminal comprises a connecting member and a functional member connected with the connecting member of the copper terminal, a conductive core of the aluminum wire is connected with the connecting member of the copper terminal, and at least the conductive core of the aluminum wire is connected with the connecting member of the copper terminal through a transition welding layer.

2. The joint of a copper terminal and an aluminum wire according to claim 1, wherein the joint of the copper terminal and the aluminum wire comprises a crimping region, an area of the crimping region accounts for at least 1% of an overlapping area of the aluminum wire and the copper terminal; and preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal.

3. The joint of a copper terminal and an aluminum wire according to claim 1, wherein the transition welding layer is composed of solder, a depth of penetration of the solder accounts for 3% to 100% of a length of the connecting member of the copper terminal; and preferably, the depth of penetration of the solder accounts for 30% to 100% of the length of the connecting member of the copper terminal.

4. The joint of a copper terminal and an aluminum wire according to claim 2, wherein the transition welding layer is composed of solder, and a depth of penetration of the solder accounts for 5% to 100% of the length of the whole crimping region; and preferably, the depth of penetration of the solder accounts for 35% to 100% of the length of the whole crimping region.

5. The joint of a copper terminal and an aluminum wire according to claim 3, wherein a metal material of the solder is a metal or alloy having a melting point not higher than a melting point of aluminum; preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of a total weight of the solder; and more preferably, the zinc accounts for more than 60% of the total weight of the solder.

6. The joint of a copper terminal and an aluminum wire according to claim 1, wherein the joint of the copper terminal and the aluminum wire further comprises a reinforcing welding layer; preferably, the reinforcing welding layer wraps an end surface of the conductive core of the aluminum wire; preferably, the reinforcing welding layer has a thickness of 0 mm to 15 mm; and more preferably, the thickness of the reinforcing welding layer is 1.5 mm to 5.5 mm.

7. The joint of a copper terminal and an aluminum wire according to claim 1, wherein the copper terminal is made of copper or copper alloy; and preferably, the connecting member of the copper terminal has a flat shape, an arc shape or a hollow column shape with openings at both ends, and a side surface of the hollow column is closed or unclosed.

8. The joint of a copper terminal and an aluminum wire according to claim 1, wherein a surface of the copper terminal is further applied with a coating; preferably, the coating has a thickness of 3 m to 5000 m; more preferably, the thickness of the coating is 5 m to 1000 m; preferably, the coating is applied to the copper terminal by means of electroplating, electromagnetic welding, arc spraying or pressure welding; and preferably, a metal material of the coating is one or any combination of metals of chromium or chromium alloy, zinc or zinc alloy, tin or tin alloy, titanium or titanium alloy, zirconium or zirconium alloy, nickel or nickel alloy, silver or silver alloy, and gold or gold alloy; and more preferably, the metal material of the coating is one or any combination of metals of zinc or zinc alloy, tin or tin alloy, and nickel or nickel alloy.

9. The joint of a copper terminal and an aluminum wire according to claim 1, wherein a material of the conductive core of the aluminum wire is aluminum or aluminum alloy; and preferably, the aluminum wire is a solid conductor or a multi-strand wire.

10. A plasma welding method for preparing the joint of a copper terminal and an aluminum wire according to claim 1, comprising: step 1), assembling the conductive core of the aluminum wire to the connecting member of the copper terminal; step 2), pressing the conductive core of the aluminum wire and the connecting member of the copper terminal tight by means of crimping to form the crimping region; and step 3), conveying the solder to the copper terminal; preferably, conveying the solder to the connecting member of the copper terminal; preferably, conveying the solder to the crimping region of the aluminum wire and the copper terminal, melting the solder by plasma arc welding, and filling the solder to a connection gap between the copper terminal and the aluminum wire through capillary action to form the transition welding layer.

11. The plasma welding method for preparing the joint of a copper terminal and an aluminum wire according to claim 1, comprising: step 1), wrapping the conductive core of the aluminum wire by the solder, or wrapping at least a portion where the connecting member of the copper terminal is connected with the conductive core of the aluminum wire by the solder, and then assembling the conductive core of the aluminum wire to the connecting member of the copper terminal; step 2), pressing the conductive core of the aluminum wire, the solder and the connecting member of the copper terminal tight by means of crimping to form the crimping region; and step 3), melting the solder between the copper terminal and the aluminum wire by the plasma arc welding, and filling the solder to the gap between the copper terminal and the aluminum wire by the capillary action to form the transition welding layer.

12. The method according to claim 10, wherein, in step 3), the solder is first melted by the plasma arc welding to form the reinforcing welding layer, and then the welding process is continued to fill the solder to the gap between the copper terminal and the aluminum wire to form the transition welding layer; preferably, the reinforcing welding layer has a thickness of 0 mm to 15 mm; and more preferably, the thickness of the reinforcing welding layer is 1.5 mm to 5.5 mm.

13. The method according to claim 10, wherein, in step 2), the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 1% of the overlapping area of the aluminum wire and the copper terminal; preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal; preferably, in step 2), a compression ratio of the conductive core of the aluminum wire is between 70% and 90%, after crimping the joint of the copper terminal and the aluminum wire; and more preferably, the compression ratio of the conductive core of the aluminum wire is between 75% and 85% after crimping; preferably, in step 3), ionized and protective gases of the plasma welding are nitrogen, argon, helium, neon, krypton or xenon; and more preferably, the ionized and protective gas of the plasma welding is argon; preferably, in step 3), a welding current of the plasma welding is between 5 A and 100 A; and more preferably, the welding current of the plasma welding is between 20 A and 80 A; preferably, in step 3), a flow rate of the ionized gas is 1 to 5 liters/minute, and a flow rate of the protective gas is 3 to 12 liters/minute; and more preferably, the flow rate of the ionized gas is 2 to 3 liters/minute and the flow rate of the protective gas is 5 to 10 liters/minute; preferably, in step 3), an angle between a plasma welding torch and an axial direction of the copper terminal is less than 45 degrees and more preferably less than 20 degrees; preferably, in step 3), the depth of penetration of the solder accounts for 3% to 100% of the length of the connecting member of the copper terminal, after the joint of the copper terminal and the aluminum wire is plasma welded; and more preferably, the depth of penetration of the solder accounts for 30% to 100% of the length of the connecting member of the copper terminal; preferably, in step 3), the depth of penetration of the solder accounts for 5% to 100% of the length of the whole crimping region, after the joint of the copper terminal and the aluminum wire is plasma welded; and more preferably, the depth of penetration of the solder accounts for 35% to 100% of the length of the whole crimping region; and preferably, in step 3), the metal material of the solder is a metal or an alloy having a melting point not higher than that of aluminum; more preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of the total weight of the solder; and more preferably, the zinc accounts for more than 60% of the total weight of the solder.

14. The joint of a copper terminal and an aluminum wire according to claim 4, wherein a metal material of the solder is a metal or alloy having a melting point not higher than a melting point of aluminum; preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of a total weight of the solder; and more preferably, the zinc accounts for more than 60% of the total weight of the solder.

15. The method according to claim 11, wherein, in step 3), the solder is first melted by the plasma arc welding to form the reinforcing welding layer, and then the welding process is continued to fill the solder to the gap between the copper terminal and the aluminum wire to form the transition welding layer; preferably, the reinforcing welding layer has a thickness of 0 mm to 15 mm; and more preferably, the thickness of the reinforcing welding layer is 1.5 mm to 5.5 mm.

16. The method according to claim 11, wherein, in step 2), the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 1% of the overlapping area of the aluminum wire and the copper terminal; preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal; preferably, in step 2), a compression ratio of the conductive core of the aluminum wire is between 70% and 90%, after crimping the joint of the copper terminal and the aluminum wire; and more preferably, the compression ratio of the conductive core of the aluminum wire is between 75% and 85% after crimping; preferably, in step 3), ionized and protective gases of the plasma welding are nitrogen, argon, helium, neon, krypton or xenon; and more preferably, the ionized and protective gas of the plasma welding is argon; preferably, in step 3), a welding current of the plasma welding is between 5 A and 100 A; and more preferably, the welding current of the plasma welding is between 20 A and 80 A; preferably, in step 3), a flow rate of the ionized gas is 1 to 5 liters/minute, and a flow rate of the protective gas is 3 to 12 liters/minute; and more preferably, the flow rate of the ionized gas is 2 to 3 liters/minute and the flow rate of the protective gas is 5 to 10 liters/minute; preferably, in step 3), an angle between a plasma welding torch and an axial direction of the copper terminal is less than 45 degrees and more preferably less than 20 degrees; preferably, in step 3), the depth of penetration of the solder accounts for 3% to 100% of the length of the connecting member of the copper terminal, after the joint of the copper terminal and the aluminum wire is plasma welded; and more preferably, the depth of penetration of the solder accounts for 30% to 100% of the length of the connecting member of the copper terminal; preferably, in step 3), the depth of penetration of the solder accounts for 5% to 100% of the length of the whole crimping region, after the joint of the copper terminal and the aluminum wire is plasma welded; and more preferably, the depth of penetration of the solder accounts for 35% to 100% of the length of the whole crimping region; and preferably, in step 3), the metal material of the solder is a metal or an alloy having a melting point not higher than that of aluminum; more preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of the total weight of the solder; and more preferably, the zinc accounts for more than 60% of the total weight of the solder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 illustrates an exemplary pattern of a copper terminal;

[0055] FIG. 2 illustrates an exemplary pattern of an aluminum wire;

[0056] FIG. 3 illustrates an exemplary pattern of the aluminum wire connecting with the copper terminal;

[0057] FIG. 4 illustrates an exemplary pattern of a top view of the copper terminal and the aluminum wire after the connection is completed;

[0058] FIG. 5 illustrates an exemplary pattern of a longitudinal section of the copper terminal and a multicore aluminum wire after the welding is completed;

[0059] FIG. 6 illustrates an exemplary pattern of a longitudinal section of the copper terminal and a solid aluminum wire after the welding is completed;

[0060] FIG. 7 illustrates an exemplary pattern of a cross section of the copper terminal and the aluminum wire after the welding is completed;

[0061] FIG. 8 illustrates a bucket-shaped copper terminal applicable in the present application;

[0062] FIG. 9 illustrates an exemplary pattern of the copper terminal in FIG. 8 after the copper terminal is welded according to the method of the present application; and

[0063] FIG. 10 illustrates an exemplary pattern of a side view of a flat copper terminal and the aluminum wire after the connection is completed.

[0064] Reference numerals in FIGS. 1 to 10 are listed as follows:

TABLE-US-00001 1 copper terminal; 1.1 functional member; 1.2 connecting member; 2 aluminum wire; 2.1 insulation layer; 2.2 aluminum core conductor; 3 transition welding layer; 4 reinforcing welding layer; 5 terminal coating.

DETAILED DESCRIPTION OF EMBODIMENTS

[0065] The technical solutions of the present application are further illustrated by specific embodiments. The specific embodiments are not intended to limit the scope of protection of the present application. Some non-essential modifications and adaptations made by others according to the concept of the present application still fall within the scope of protection of the present application.

[0066] First embodiment: a joint of a copper terminal and an aluminum wire

[0067] As shown in FIGS. 1 and 8, the copper terminal 1 includes a connecting member 1.2 and a functional member 1.1 at a rear end thereof.

[0068] As shown in FIG. 2, the aluminum wire 2 is a multi-strand wire, which includes an aluminum core conductor 2.2 and an insulation layer 2.1.

[0069] The conductive core of the aluminum wire 2 is connected with the connecting member 1.2. Specifically, a longitudinal sectional view of the joint is shown in FIG. 5. A transition welding layer 3 is provided in a gap between a front end of the aluminum wire and the connecting member. A reinforcing welding layer 4 is further provided at the front end of the aluminum wire. The reinforcing welding layer 4 completely wraps an end face of the front end of the aluminum wire and is integrated with the transition welding layer.

[0070] As shown in FIG. 3, the reinforcing welding layer has a thickness of 0 mm to 15 mm, and preferably, the thickness of the reinforcing welding layer is 1.5 mm to 5.5 mm.

[0071] As shown in FIG. 5, a crimping region is provided between the copper terminal and the conductive core of the aluminum wire, and an area of the crimping region accounts for at least 1% of an overlapping area between the aluminum wire and the copper terminal. Preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area between the aluminum wire and the copper terminal.

[0072] Second embodiment: a joint of a copper terminal and an aluminum wire

[0073] Compared with the first embodiment, the present embodiment has the following difference: the joint does not have a reinforcing welding layer.

[0074] Third embodiment: a joint of a copper terminal and an aluminum

[0075] Compared with the first embodiment, the present embodiment has the following difference: as shown in FIG. 10, the connecting member of the copper terminal is flat, the aluminum wire is pre-pressed onto the copper terminal by a tool or a die, the solder is melted between the copper terminal and the aluminum wire by the plasma arc welding and is filled to the gap between the copper terminal and the aluminum wire by capillary action to form the transition welding layer.

[0076] Fourth embodiment: a joint of a copper terminal and an aluminum

[0077] Compared with the first embodiment, the present embodiment has the following difference:

[0078] As shown in FIG. 5, a surface of the copper terminal further includes a coating 5.

[0079] Preferably, the coating has a thickness of 3 m to 5000 m, and more preferably, the thickness of the coating is 5 m to 1000 m.

[0080] Preferably, the coating is applied to the copper terminal by means of electroplating, electromagnetic welding, arc spraying or pressure welding.

[0081] Electroplating process includes the following steps: step 1, providing a plated metal at an anode; step 2, providing a substance to be plated at a cathode; step 3, connecting the cathode and the anode with an electrolyte solution containing metal positive ions to be plated; step 4, oxidizing (losing electrons) the metal of the anode, reducing (obtaining electrons) the positive ions in the solution at the cathode into atoms and accumulating the atoms on a surface layer of the cathode, after the cathode and the anode are energized by a direct current power supply.

[0082] Electromagnetic welding process includes the following steps: step 1, stacking two kinds of metals to be pressure-welded; step 2, forming a high voltage magnetic in the welding area through electromagnetic welding equipment, enabling the two kinds of metals to collide at an atomic energy level driven by an electromagnetic force, thereby welding the two kinds of metals together.

[0083] Arc spraying process includes: conveying the spacer metal to an arc area and atomizing the spacer metal, and then spraying the atomized spacer metal onto a surface of a workpiece at a high speed under the action of the compressed gas to form an arc spraying coating.

[0084] Pressure welding process includes the following steps: step 1, stacking two kinds of metals to be pressure-welded; step 2, applying pressure to fully diffuse surfaces to be welded to realize interatomic bonding; step 3, improving the welding effect and shortening the welding time by increasing the temperature, according to the metal and the pressure source.

[0085] Preferably, the metal material of the coating is one or any combination of metals of chromium or chromium alloy, zinc or zinc alloy, tin or tin alloy, titanium or titanium alloy, zirconium or zirconium alloy, nickel or nickel alloy, silver or silver alloy, and gold or gold alloy. More preferably, the metal material of the coating is one or any combination of metals of zinc or zinc alloy, tin or tin alloy, and nickel or nickel alloy.

[0086] Fifth embodiment: a joint of a copper terminal and an aluminum

[0087] Compared with the first embodiment, as shown in FIG. 6, the present embodiment has the following difference: the aluminum wire is a solid conductor.

[0088] Sixth embodiment: a plasma welding method for a copper terminal and an aluminum wire

[0089] As shown in FIG. 1, the copper terminal 1 of the present application has the functional member 1.1 and the connecting member 1.2 connected to the functional member. In the present embodiment, the connecting member is wing-shaped, and an end face of the connecting member has a U-shaped structure.

[0090] As shown in FIG. 2, the aluminum wire 2 of the present application has a multicore aluminum wire 2.2 and an outer insulation layer 2.1. Part of the insulation layer is peeled off according to the size of the copper terminal before crimping.

[0091] The following are the steps for preparing the joint of the copper terminal and the aluminum wire:

[0092] As shown in FIG. 3, the insulation layer of the aluminum wire is peeled off, then the aluminum wire is placed in the wing-shaped connecting member of the copper terminal, and then the aluminum wire and the wing-shaped connecting member of the copper terminal are crimped by a crimping die, wherein the area of the crimping region accounts for at least 1% of the overlapping area between the aluminum wire and the copper terminal. Preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area between the aluminum wire and the copper terminal.

[0093] After crimping, the compression ratio of the conductive core of the aluminum wire is between 70% and 90%. Preferably, the compression ratio of the conductive core of the aluminum wire is between 75% and 85% to ensure the mechanical performance and electrical conductivity of the joint of the copper terminal and the aluminum wire, and the joint of the copper terminal and the aluminum wire after crimping is shown in FIG. 4.

[0094] Specifically, the solder is conveyed to the copper terminal. Preferably, the solder is conveyed to the connecting member of the copper terminal. Preferably, the solder is conveyed to the crimping region of the aluminum wire and the copper terminal, and then the solder is melted by plasma arc welding and filled to the connection gap between the copper terminal and the aluminum wire by capillary action to form the transition welding layer.

[0095] The ionized and protective gas of the plasma welding may be nitrogen, argon, helium, neon, krypton or xenon, and more preferably argon; a flow rate of the ionized gas is 1 to 5 liters/minute, and a flow rate of the protective gas is 3 to 12 liters/minute. Preferably, the flow rate of the ionized gas is 2 to 3 liters/minute, and the flow rate of the protective gas is 5 to 10 liters/minute; in the welding process, an angle between a plasma soldering gun and an axial direction of the copper terminal is less than 45 degrees, and more preferably less than 20 degrees; and a welding current of the plasma welding is between 5 A and 100 A, and more preferably between 20 A and 80 A.

[0096] In the welding process, the welding temperature at a center area can reach 400 Celsius to 550 Celsius, so that the solder is melted to form the reinforcing welding layer 4 first, and then as the welding process continues, the solder is filled to the gap between the copper terminal and the aluminum wire to form the transition welding layer 3. The longitudinal section view of a final state of the joint of the copper terminal and the aluminum wire is shown in FIG. 5. The depth of penetration of the solder accounts for 3% to 100% of the length of the connecting member of the copper terminal. More preferably, the depth of penetration of the solder accounts for 30% to 100% of the length of the connecting member of the copper terminal; and preferably, the depth of penetration of the solder accounts for 5% to 100% of the length of the whole crimping region, and more preferably, the depth of penetration of the solder accounts for 35% to 100% of the length of the whole crimping region.

[0097] The metal material of the solder is a metal or alloy having a melting point not higher than that of aluminum, so that the conductive core of the aluminum wire is not melted during welding, and the solder can infiltrate into the gap between the conductive core of the aluminum wire and the copper terminal by capillary action, to form the transition welding layer or form, in the present embodiment, the reinforcing welding layer first, and then form the transition welding layer.

[0098] FIG. 7 shows a cross section view of the crimping region of the connecting member of the copper terminal and the aluminum wire, wherein the solder is tightly fused between the connecting member of the copper terminal and the aluminum wire, which insulates the conductive core of the aluminum wire from the corrosion of air and water, effectively avoids the electrochemical corrosion of the joint of the copper terminal and the aluminum wire caused by air and water, and well conducts conductivity with copper and aluminum, thereby ensuring the mechanical performance, electrical performance, and service life of the joint of the copper terminal and the aluminum wire.

[0099] Seventh embodiment: a plasma welding method for a copper terminal and an aluminum wire

[0100] Compared with the sixth embodiment, the present embodiment has the following difference: the connecting member of the copper terminal is flat and arc-shaped, and when welding, the solder is first conveyed to the copper terminal. Preferably, the solder is conveyed to the connecting member of the copper terminal. Preferably, the solder is conveyed to the crimping region of the aluminum wire and the copper terminal, and then the solder is melted by plasma arc welding and filled to the connection gap between the copper terminal and the aluminum wire by capillary action, to form the transition welding layer. The melted solder is only filled into the connection gap between the connecting member of the copper terminal and the aluminum wire, so as to form the transition welding layer, but not to form the reinforcing welding layer.

[0101] Eighth embodiment: a plasma welding method for a copper terminal and an aluminum wire

[0102] Compared with the sixth embodiment, the present embodiment has the following difference:

[0103] 1. After the insulation layer of the aluminum wire is peeled off, the conductive core of the aluminum wire without the insulation layer is wrapped by a solid thin layer of solder, and then is placed into the connecting member of the copper terminal for crimping.

[0104] 2. The connecting member of the copper terminal has a hollow column structure with openings at both ends, and a side surface of the connecting member is closed or unclosed.

[0105] Ninth embodiment: a method for connecting a copper terminal and an aluminum wire

[0106] Compared with the sixth embodiment, the present embodiment has the following difference:

[0107] After the insulation layer of the aluminum wire is peeled off, at least a portion where the connecting member of the copper terminal is connected with the conductive core of the aluminum wire is wrapped by the solid thin layer of solder, and then the conductive core of the aluminum wire is placed into the connecting member of the copper terminal for crimping.

[0108] Tenth embodiment: effects of different connection methods on a voltage drop and drawing force of a joint of a copper terminal and an aluminum wire

[0109] Copper terminals and aluminum wires of a same specification and structure are used to prepare joints of copper terminals and aluminum wires in the following five methods. Ten samples are prepared for each method, that is, a total of 50 samples.

[0110] First method: crimping

[0111] The aluminum wire is directly crimped into the copper terminal by a die.

[0112] Second method: plasma arc welding [0113] The copper terminal is directly welded together with the aluminum wire by plasma arc welding. A welding current of the plasma arc welding is 40 A, a flow rate of the ionized gas argon is 2.5 liters/minute, a flow rate of the protective gas argon is 7.5 liters/minute, and an angle between a plasma soldering gun and an axial direction of the copper terminal is 15 degrees.

[0114] Third welding method: crimping plus plasma arc welding [0115] Referring to the sixth embodiment, the aluminum wire is crimped into the copper terminal by a die, and then the copper terminal is welded with the aluminum wire by plasma arc welding. After crimping, a compression ratio of the aluminum wire is 80%. A welding current of the plasma arc welding is 40 A. A flow rate of the ionized gas argon is 2.5 liters/minute, a flow rate of the protective gas argon is 7.5 liters/minute, and an angle between a plasma soldering gun and an axial direction of the copper terminal is 15 degrees.

[0116] Fourth welding method: plasma arc welding plus solder [0117] The solder is conveyed to the connecting member of the copper terminal, and the copper terminal is welded with the aluminum wire by plasma arc welding. A welding current of the plasma arc welding is 40 A. [0118] The solder contains 90% zinc and 10% aluminum, a flow rate of the ionized gas argon is 2.5 liters/minute, a flow rate of the protective gas argon is 7.5 liters/minute, and an angle between a plasma soldering gun and an axial direction of the copper terminal is 15 degrees.

[0119] Fifth welding method: crimping plus plasma arc welding plus solder [0120] The aluminum wire is crimped into the connecting member of the copper terminal by a die. The solder is conveyed to the connecting member of the copper terminal, and the copper terminal is welded with the aluminum wire by plasma arc welding. A welding current of the plasma arc welding is 40 A. The solder contains 90% zinc and 10% aluminum. After crimping, a compression ratio of the aluminum wire is 80%. A flow rate of the ionized gas argon is 2.5 liters/minute, a flow rate of the protective gas argon is 7.5 liters/minute, and an angle between a plasma soldering gun and an axial direction of the copper terminal is 15 degrees.

[0121] After the joints of the copper terminals and the aluminum wires are prepared in the above five methods, the voltage drop and drawing force of the 50 samples in 5 groups are tested in a same test method, and test parameters of each group of samples are averaged. The test results are shown in Table 1.

TABLE-US-00002 TABLE 1 A comparison of voltage drops and drawing forces of the joints of the copper terminals and aluminum wires prepared in five different preparing methods Voltage Drawing Welding method drop(mV ) force (N) First method Crimping 6.65 1687.3 Second method Plasma arc welding 5.39 1745.5 Third method Crimping plus plasma 5.13 3058.1 arc welding Fourth method Plasma arc welding 3.32 3072.5 plus solder Fifth method Crimping plus plasma 3.01 3356.5 arc welding plus solder

[0122] It can be seen from Table 1 that for the joints of the copper terminals and the aluminum wires prepared only by crimping or only by plasma arc welding (the first method and the second method), the drawing force of the joint is small and the voltage drop is large, which cannot meet the requirements of the mechanical performance and electrical performance that the joint of the copper terminal and the aluminum wire should reach in use. Although the drawing force of the joint of the copper terminal and the aluminum wire can be improved by using the third method, the voltage drop thereof is still large, which still cannot meet the requirements of the electrical performance that the joint of the copper terminal and the aluminum wire should reach in use. The joints of the copper terminals and the aluminum wires prepared by the fourth method and the fifth method of the present application meet the requirements of the mechanical performance and electrical performance that the joint of the copper terminal and the aluminum wire should reach in use. It is obvious that the mechanical performance and electrical performance of the joint prepared by the crimping plus plasma arc welding plus solder preparing method of the joint of the copper terminal and the aluminum wire of the present application are the best among the above five methods.

[0123] Eleventh embodiment: effects of solders with different zinc-base ratios on performance of the joint of the copper terminal and the aluminum wire

[0124] The welding method refers to the sixth embodiment. With the variable control method, the welding current is 40 A, the flow rate of the ionized argon is 3 liters/minute, the flow rate of the protective argon is 8 liters/minute, the compression ratio of the aluminum wire is 80%, and the angle between the soldering gun of the plasma welding and the axial direction of the copper terminal is 15 degrees. The solders are at different zinc-base ratios, and the joints are prepared by the manufacturing method of the joint of the copper terminal and the aluminum wire of the third embodiment. The drawing force and voltage drop of the prepared joints are tested according to the same test method, 100 samples are prepared for each zinc-base ratio, and test parameters are averaged. The test results are shown in Table 2.

TABLE-US-00003 TABLE 2 Effects of solders with different zinc- base ratios on performance of the joint Voltage Drawing NO. Metal material of solder drop(mV) force(N) 1 100%Zn 2.72 3238.3 2 90% Zn 10% Al 2.81 3236.7 3 80% Zn 20% Al 2.95 3229.5 4 70% Zn 30% Al 3.08 3224.6 5 60% Zn 40% Al 3.59 3012.7 6 50% Zn 50% Al 3.68 2956.3 7 40% Zn 60% Al 3.79 2875.3 8 30% Zn 70% Al 3.91 2765.1 9 20% Zn 80% Al 4.78 2497.6 10 10% Zn 90% Al 5.75 2401.2

[0125] It can be seen from Table 2, the higher the weight ratio of zinc, the lower the voltage drop of the copper terminal and the aluminum wire, that is, the better the electrical performance of the joint of the copper terminal and the aluminum wire.

[0126] When a joint of a copper terminal and an aluminum wire is made of a solder having a zinc-base ratio of 30% or more of the total weight of the solder, the drawing force performance of the joint can meet the requirements of the use mechanical performance of most of the joint of the copper terminal and the aluminum wire. When a joint of a copper terminal and an aluminum wire is made of a solder having a zinc-base ratio of 60% or more of the total weight of the solder, the drawing force performance of the joint can fully meet the requirements of the use mechanical performance of the joint of the copper terminal and the aluminum wire.

[0127] Twelfth embodiment: effect of compression ratio of the conductive core of the aluminum wire on the performance of the joint of the copper terminal and the aluminum wire

[0128] In order to test the effects of different compression ratios of the conductive core of the aluminum wire on the performance of the joint of the copper terminal and the aluminum wire, the variable control method is used in the present embodiment. Different joints as shown in Table 3 are prepared by using the manufacturing method of the joint of the copper terminal and the aluminum wire of the sixth embodiment. The welding current is 40 A, the flow rate of the ionized argon is 3 liters/minute, the flow rate of the protective argon is 8 liters/minute, the solder contains 90% zinc and 10% aluminum, and the angle between the plasma soldering gun and the axial direction of the copper terminal is 15 degrees. 10 samples of the joint are obtained by each method, and test parameters are averaged. The compression ratios and test results are shown in Table 3.

TABLE-US-00004 TABLE 3 Effects of different compression ratios of the conductive core of the aluminum wire on the performance of the joint of the copper terminal and the aluminum wire Compression ratio of the aluminum Voltage Drawing NO. wire drop(mV) force(N) 1 65% 3.96 2059.1 2 70% 3.56 2638.4 3 75% 3.27 2997.5 4 80% 3.05 3261.2 5 85% 3.19 2918.7 6 90% 3.51 2575.4 7 95% 4.36 2095.3

[0129] According to the test results in this table, if the compression ratio of the conductive core of the aluminum wire is between 70% and 90% after crimping, the electrical performance and mechanical performance of the joint of the copper terminal and the aluminum wire are better. More preferably, if the compression ratio of the conductive core of the aluminum wire is between 75% and 85% after crimping, the electrical performance and mechanical performance of the joint of the copper terminal and the aluminum wire are more prominent.

[0130] Thirteenth embodiment: effects of different thicknesses of the reinforcing welding layer on the drawing force and the voltage drop of the joint of the copper terminal and the aluminum wire

[0131] In order to prove the effects of different thicknesses of the reinforcing welding layer on the performance of the joint of the copper terminal and the aluminum wire, 17 groups of samples with different thicknesses of the reinforcing welding layer are prepared, and each group includes 10 samples. The average values of the test results of each thickness of the reinforcing welding layer are filled in the table 4, after the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire are tested.

[0132] The welding method refers to the sixth embodiment. The solder contains 90% zinc and 10% aluminum, the flow rate of the ionized gas argon is 2.5 liters/minute, the flow rate of the protective gas argon is 7.5 liters/minute, and the angle between the plasma soldering gun and the axial direction of the copper terminal is 15 degrees.

[0133] It can be seen from the data in Table 4 that the performance of the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire begins to decrease significantly, if the thickness of the reinforcing welding layer of the joint of the copper terminal and the aluminum wire exceeds 15 mm. Therefore, the thickness of the reinforcing welding layer is preferred to be 0 mm to 15 mm, and the performance of the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire is better, if the thickness of the reinforcing welding layer is 1.5 mm to 5.5 mm,

TABLE-US-00005 TABLE 4 Effects of different thicknesses of the reinforcing welding layer on the performance of the joint of the copper terminal and the aluminum wire Thickness of the reinforcing Drawing Voltage NO. welding layer (mm) force (N) drop (mV) 1 0 3220.8 2.95 2 1 3217.4 3.01 3 1.5 3224.5 3.12 4 2 3229.8 3.28 5 2.5 3249.7 3.41 6 3 3256.4 3.52 7 3.5 3187.8 3.67 8 4 3126.6 3.72 9 5.5 3062.4 3.76 10 6 3028.7 3.82 11 8 3016.5 3.94 12 10 2897.6 4.05 13 12 2901.4 4.18 14 14 2745.6 4.22 15 15 2726.4 4.31 16 16 2672.5 4.58 17 17 2591.3 4.67

[0134] Fourteenth embodiment: effects of different depths of penetration of the solder on the performance of the joint of the copper terminal and the aluminum wire

[0135] In order to verify the effect of the depth of penetration on the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire, 44 groups of welding samples with different depths of penetration are prepared, and each group includes 10 samples.

[0136] The welding method refers to the sixth embodiment. The solder contains 90% zinc and 10% aluminum, the flow rate of the ionized gas argon is 2.5 liters/minute, the flow rate of the protective gas argon is 7.5 liters/minute, and the angle between the plasma soldering gun and the axial direction of the copper terminal is 15 degrees.

[0137] It can be seen from Table 5 that the greater the ratio of the depth of penetration to the length of the connecting member or the length of the crimping region, the better the mechanical performance and electrical performance of the joint of the copper terminal and aluminum wire. However, the mechanical performance and electrical performance of the joint of the copper terminal and the aluminum wire are decreased significantly, if the welding depth accounts for less than 5% of the length of the crimping region, or if the welding depth accounts for less than 3% of the length of the connecting member. The mechanical performance and electrical performance of joint of the copper terminal and the aluminum wire are better, if the depth of penetration of the solder accounts for 35% to 100% of the crimping region of the joint of the copper terminal and the aluminum wire, or if the depth of penetration of the solder accounts for 30% to 100% of the length of the connecting member.

TABLE-US-00006 TABLE 5 Effects of different depths of penetration of the solder on the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire Ratio of depth of Ratio of depth of penetration to the Drawing Voltage penetration to the Drawing Voltage length of the force drop length of the force drop NO. crimping region (N) (mV) connecting (N) (mV) 1 100% 3354.1 3.18 100% 3249.8 3.52 2 95% 3327.5 3.24 95% 3217.4 3.64 3 90% 3304.3 3.37 90% 3194.2 3.72 4 85% 2994.8 3.49 85% 3146.8 3.89 5 80% 2973.4 3.52 80% 3021.6 3.97 6 75% 2956.7 3.66 75% 2992.4 4.05 7 70% 2934.9 3.71 70% 2988.3 4.11 8 65% 2907.5 3.88 65% 2971.4 4.16 9 60% 2892.4 3.94 60% 2916.7 4.21 10 55% 2878.4 4.08 55% 2901.3 4.28 11 50% 2864.2 4.16 50% 2882.9 4.29 12 45% 2849.4 4.24 45% 2773.4 4.35 13 40% 2834.7 4.39 40% 2749.6 4.42 14 35% 2829.4 4.52 35% 2728.7 4.59 15 30% 2811.7 4.66 30% 2699.5 4.71 16 25% 2786.9 4.71 25% 2671.8 4.86 17 20% 2763.8 4.79 20% 2618.4 4.98 18 15% 2751.6 4.82 15% 2586.4 5.18 19 10% 2737.4 4.94 10% 2574.2 5.29 20 5% 2681.2 5.27 5% 2541.8 5.47 21 3% 2513.7 6.08 3% 2519.4 6.48 22 1% 2428.1 6.49 1% 2498.2 6.74

[0138] Fifteenth embodiment: effects of different areas of the crimping region on the performance of the joint of the copper terminal and the aluminum wire

[0139] In order to verify the effect of the area of the crimping region of the joint of the copper terminal and the aluminum wire on the drawing force and voltage drop of the joint, 12 groups of welding samples with different areas of the crimping region are prepared, and each group includes 10 samples.

[0140] The welding method refers to the sixth embodiment. The solder contains 80% zinc and 20% aluminum, the flow rate of the ionized gas argon is 2.5 liters/minute, and the flow rate of the protective gas argon is 7.5 liters/minute, and the angle between the plasma soldering gun and the axial direction of the copper terminal is 20 degrees.

TABLE-US-00007 TABLE 6 Effects of different ratios of the area of the crimping region to the overlapping area of the aluminum wire and the copper terminal on the drawing force and voltage drop of the joint of the copper terminal and the aluminum wire Ratio of the area of the crimping region to the overlapping area of the aluminum wire and the copper Voltage Drawing NO. terminal drop(mV) force(N) 1 100% 2.71 3157.2 2 90% 2.61 3211.8 3 80% 2.75 3194.7 4 70% 2.84 3027.6 5 60% 2.92 2974.4 6 50% 3.01 2964.3 7 40% 3.11 2945.8 8 30% 3.28 2918.4 9 20% 3.41 2846.7 10 10% 3.88 2819.8 11 1% 4.21 2726.4 12 <1% 5.07 2434.8

[0141] It can be seen from the Table 6 that the greater the ratio of the area of the crimping region of the joint of the copper terminal and the aluminum wire to the overlapping area of the aluminum wire and the copper terminal, the better the mechanical performance and electrical performance of the connecting member. However, the mechanical performance and electrical performance of the connecting member are significantly decreased, if the ratio of the area of the crimping region to the overlapping area of the aluminum wire and the copper terminal is less than 1%. Therefore, it is preferred that the area of the crimping region accounts for at least 1% of the overlapping area of the aluminum wire and the copper terminal, and preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal.