Laser welding process

Abstract

In this laser welding method, a laser beam LB is irradiated from a Z direction onto a workpiece (200) having a region where a copper wire (220) and a copper plate (210) are superimposed. The laser welding method includes a welding step in which the laser beam LB is advanced along a welding direction WD at a welding speed V through a central axis CC of the copper wire (220). At the same time, the laser beam LB is scanned to reciprocate in a Y direction intersecting the welding direction WD and the Z direction, respectively, to irradiate the laser beam LB onto the copper wire (220) and the copper plate (210). In the welding step, the laser beam LB is irradiated onto the workpiece 200 so as to form a sine curve extending along the X direction with the central axis CC as a line of symmetry.

Description

[Technical field]

[0001] The present disclosure relates to a laser welding process. [Technical background]

[0002] Previously, a resistance welding process was frequently used in the assembly of electronic components and electronic devices to electrically connect copper wires to flat copper terminals or copper conductors mounted on circuit boards.

[0003] In the resistance welding process, the copper wire and copper terminals are clamped from above and below with a pair of welding electrodes connected to a resistance welding machine, and by allowing a welding current to flow between the welding electrodes, the copper wire and copper terminals are welded together.

[0004] However, with resistance welding, the workpieces to be welded must be clamped from above and below with the welding electrodes, requiring space and time to move the electrodes. This also increases the cycle time required for welding. Furthermore, when resistance welding copper wire and copper terminals, the electrical resistance of copper is low, and the electrical resistance of the junction between the copper wire and copper terminal is roughly equivalent to that of the welding electrodes. For this reason, the current behavior at the junction is unstable, causing the welding electrodes to wear out quickly. This means that the welding electrodes require more frequent replacement and maintenance.

[0005] Therefore, in recent years, laser welding has been used for the aforementioned overlap welding of copper wire and copper terminals (see, for example, patent documents 1 and 2). Patent document 1, for instance, describes a part in the form of a flange around which a copper wire is wound as a coil. A part is provided for holding and fixing the coil end, and the coil end is positioned against a part of the flange, while the flange is clamped to hold the coil end to the part. In this state, laser light is directed onto the part from above to achieve laser welding of the coil and the part. [State of the art] [Patent literature] [Patent Document 1] JP 2008-010753 A [Patent Document 2] JP 2008-006472 A [Summary of the invention]

[0006] However, when laser welding copper wire onto sheet materials such as copper terminals, insufficient melting of the workpiece can lead to a reduction in the weld width, resulting in a smaller than desired contact area between the copper terminal and the copper wire.

[0007] Laser welding often uses near-infrared laser light, but copper absorbs light of this wavelength poorly, requiring increased laser power to melt the workpiece sufficiently. However, the light absorption of metals generally increases significantly in the liquid phase compared to the solid phase. Therefore, increasing the laser power can cause the copper to melt and the molten metal to become highly turbulent in the weld pool, potentially leading to spatter. Furthermore, the workpiece melts very rapidly from the inside. This can create holes or even cut through the laser point, preventing a reliable electrical connection between the copper wire and the copper terminal.

[0008] In the conventional method disclosed in patent document 1, an additional part had to be attached to the copper terminal plate, which served as a component, and an additional crimping process had to be performed. Furthermore, due to variations in the crimping during this step, gaps could occur between the copper terminal part and the end of the coil, which was the copper wire. If such gaps exist, the heat from the part struck by the laser beam is not sufficiently transferred to the end of the coil, which can lead to welding defects. Moreover, it is difficult to stabilize the quality of the welds.

[0009] The present disclosure was prepared taking these points into consideration and aims to provide a laser welding process which, when laser welding workpieces consisting mainly of copper, enables a simplification of the workpiece structure while simultaneously enabling low-power welding.

[0010] To achieve the aforementioned goal, the laser welding method according to this disclosure is a laser welding method in which a workpiece with an area where a wire material and a sheet material are superimposed is irradiated with laser light from the surface of the wire material to join the sheet material and the wire material together, wherein a welding direction of the workpiece is an X-direction, a normal direction of the bearing surface of the wire material on the sheet material is a Z-direction, and a direction intersecting the X- and Z-directions is a Y-direction, wherein the laser welding method comprises at least one welding step in which the laser beam is moved at a predetermined speed along the X-direction and through the central axis of the wire in the longitudinal direction of the wire, wherein the laser beam is scanned back and forth along the Y-direction so that it crosses the wire.and the laser beam irradiates the wire material and the plate material, wherein in the welding step the laser radiation irradiates the workpiece in such a way that it forms a sine or triangular wave extending along the X-direction with the central axis of the wire material as a line of symmetry, wherein a proportion of the time in which the laser beam hits the overlap area of ​​wire material and plate material, in relation to a predetermined scan period of the irradiation path of the laser beam hitting the wire material and the plate material, is expressed by a predetermined wire irradiance α.

[0011] According to this disclosure, when laser welding workpieces that mainly contain copper as the metal, the structure of the workpiece can be simplified and low-power welding can be enabled. This can stabilize the quality of the weld. [Brief description of the drawings] [ Fig. Figure 1] is a schematic representation of the laser welding device according to the embodiment. [ Fig. Figure 2] is a schematic representation of the laser scanners. [ Fig. Figure 3 shows the wavelength dependence of the light absorption rate of different metals. [ Fig. Figure 4] is a schematic representation of the workpiece during laser welding. [ Fig. [5A] is a top view showing the path of the laser light to the workpiece. [ Fig. [5B] is a top view showing a different path of the laser light onto the workpiece. [ Fig. [6] is a photograph showing the appearance of the workpiece after laser welding. [ Fig. [7A] is a schematic cross-sectional representation along the line VIIA-VIIA in Fig. 6. [ Fig. [7B] is a schematic cross-sectional representation along the line VIIB-VIIB in Fig. 6. [ Fig. 7C] is a schematic cross-sectional representation along the line VIIIC-VIIIC in Fig. 6. [ Fig. [7D] is a schematic cross-sectional view along line VIIID-VIIID in Fig. 6. [ Fig. Figure 8] is a schematic representation of the workpiece in conventional laser welding. [ Fig. Figure 9] is a schematic representation of the workpiece after completion of conventional laser welding. [ Fig. Figure 10 shows an example of the appearance of the workpiece after laser welding. [ Fig. Figure 11] is a diagram showing the relationship between the scan frequency and the height of the weld in the middle position. [ Fig.

[12] is a diagram showing the relationship between the scan frequency and the width of the weld in the middle position. [Embodiments of the invention]

[0012] The present invention is explained below with reference to the drawings. The following explanations of preferred embodiments serve only for illustration and are not to be understood as limiting the present invention, its possible applications, or its uses. (Design)[Setup of a laser welding device]

[0013] Fig. Figure 1 shows a schematic representation of the laser welding device according to the present embodiment, and Fig. Figure 2 shows a schematic representation of the laser scanner.

[0014] As in Fig. As shown in Figure 1, the laser welding device 100 comprises a laser oscillator 10, an optical fiber 20, a laser head 30, a robot 70, and a control unit 80. The propagation direction of the laser beam LB directed from the laser head 30 onto the workpiece 200 is referred to below as the Z-direction. Fig.In this embodiment, the direction from the laser oscillator 10 to the laser head 30 is designated as the X-direction, and the direction that intersects the X-direction and the Z-direction is designated as the Y-direction. The X-direction corresponds to the welding direction WD of the workpiece 200. The welding direction WD, in this case the X-direction, is also the longitudinal direction of the weld seam 230 described later (see Figure 1). Fig. 6 and Fig. 7D). The Z-direction corresponds to the direction that intersects the surface of the copper plate (plate material) 210 of the workpiece 200. The Y-direction corresponds to the direction that intersects the welding direction WD (X-direction). In other words, the Y-direction corresponds to the direction that runs perpendicular to the welding direction WD (X-direction). As in Fig. Figure 1 shows the “surface of the copper plate (plate) 210” as the bearing surface of the copper wires (wire material) 220 on the copper plate 210.

[0015] The laser oscillator 10 outputs the laser beam LB upon command from the control unit 80. In this embodiment, the wavelength of the laser beam LB is 445 nm. However, this is not specifically limited, and the wavelength range of the laser beam LB can also lie in the green to blue wavelength range. In other words, the wavelength of the laser beam LB is preferably 350 nm or more and 550 nm or less, and more preferably 400 nm or more and 500 nm or less.

[0016] The laser oscillator 10 and the laser head 30 are connected to each other via an optical fiber 20. The laser light radiation LB is transmitted from the laser oscillator 10 to the laser head 30 via the optical fiber 20.

[0017] The laser head 30 receives the laser beam LB emitted by the optical fiber 20 and emits it onto the workpiece 200. The optical fiber 20 has, for example, a core (not shown) that serves as an optical waveguide and is surrounded by a light-enclosing layer (not shown) called the cladding.

[0018] The laser head 30 has a collimator lens 40, a laser scanner 50 and an fθ lens 60.

[0019] The collimator lens 40 converts the laser beam LB exiting the optical fiber 20 into parallel light beams. In other words, the collimator lens 40 parallelizes the laser beam LB.

[0020] The laser scanner 50, for example, is a galvanic scanner with a first galvanic mirror 51 and a second galvanic mirror 52. The first galvanic mirror 51 comprises a first mirror 51a, a first rotation axis 51b, and a first drive 51c, while the second galvanic mirror 52 comprises a second mirror 52a, a second rotation axis 52b, and a second drive 52c. The laser beam LB passing through the collimator lens 40 is reflected by the first mirror 51a, then reflected by the second mirror 52a, and directed into the fθ lens 60.

[0021] For example, the first drive unit 51c and the second drive unit 52c are electroplating motors, and the first rotary axis 51b and the second rotary axis 52b are the output shafts of the electroplating motors. A control signal from the control unit 80 sets the first drive unit 51c in rotation, causing the first mirror 51a, which is attached to the first rotary axis 51b, to rotate about the axis of the first rotary axis 51b. Similarly, a control signal from the control unit 80 sets the second drive unit 52c in rotation, causing the second mirror 52a, which is attached to the second rotary axis 52b, to rotate about the axis of the second rotary axis 52b.

[0022] By rotating the first mirror 51a around the axis of the first rotation axis 51b by a specific angle, the laser beam LB is scanned in the X direction. By rotating the second mirror 52a around the axis of the second rotation axis 52b by a specific angle, the laser beam LB is scanned in the Y direction. This means that the laser scanner 50 is designed to scan the laser beam LB two-dimensionally in the XY plane and direct it onto the workpiece 200.

[0023] The design of the Laserscanner 50 is not based on the in Fig. The 2 shown is limited. The laser scanner 50 can, for example, also consist of a two-axis MEMS mirror.

[0024] The fθ lens 60 focuses the laser beam LB at the point where the laser beam LB enters the workpiece. The laser beam LB, focused by the fθ lens 60, is directed onto the workpiece 200. The laser output aperture of the laser head 30 is covered by a protective glass (not shown).

[0025] The robot 70 has a robot arm 71. The laser head 30 is attached to the tip of the robot arm 71. The robot arm 71 has several joints 72.

[0026] The robot 70 moves the laser head 30 in a predetermined welding direction WD, in this case in the X direction, on command from the control unit 80, thus changing the position of the laser head 30 relative to the workpiece 200. This shifts the irradiation position of the laser beam LB relative to the workpiece 200 and performs the laser welding.

[0027] The structure of the robot 70 is not specifically designed for the in Fig.The mechanism shown in Figure 1 is limited; any mechanism that moves the laser head 30 along the X, Y, and Z axes can be used. For example, instead of a robot 70, an actuator that moves the laser head 30 in the X direction, an actuator that moves it in the Y direction, and an actuator that moves it in the Z direction can be arranged as the robotic mechanism of a Cartesian robot.

[0028] Alternatively, a holding platform (not shown) that holds the workpiece 200 can be provided with a movement mechanism (not shown) that moves the holding platform in the X and Y directions, and the actuator that moves the laser head 30 in the Z direction, and the movement mechanism can be arranged as a robot mechanism consisting of several mechanical units instead of the robot 70.

[0029] The control unit 80 is connected to the laser oscillator 10, the robot 70, and the laser head 30. The control unit 80 controls the operation of the laser oscillator 10, the robot 70, the laser head 30, and, in particular, the laser scanner 50. In addition to controlling the movement speed of the laser head 30, the control unit 80 also has functions for controlling the radiation path of the laser beam LB on the surface of the workpiece 200, the start and stop of the laser beam LB output, and the power of the laser beam LB.

[0030] The control unit 80 consists of one or more CPUs (Central Processing Units) or MCUs (Microcontroller Units). The functions mentioned above, which are performed by the control unit 80, are realized by executing a predefined welding program on the CPU or MCU. The welding program is stored in memory (not shown). This memory can be integrated into the control unit 80 or located externally.

[0031] Furthermore, the control unit that controls the operation of the laser oscillator 10, the control unit that controls the operation of the laser head 30, and the control unit that controls the operation of the robot 70 can be arranged separately. In this case, however, the respective control units jointly control the operation of the laser welding device 100.

[0032] By irradiating the workpiece 200 with the laser beam LB along a predetermined path described later, a weld seam 230 is formed on the workpiece 200. The structure and material of the workpiece 200 as well as the shape of the weld seam 230 will be described later. [Laser welding process]

[0033] Fig. Figure 3 shows the wavelength dependence of the light absorption rate of different metals. Fig. Figure 4 is a schematic representation of the workpiece during laser welding. Fig. 5A is a top view showing the path of the laser beam to the workpiece. Fig. 5B is a top view showing a different path of the laser beam onto the workpiece.

[0034] Fig. Figure 6 shows a photograph of the workpiece after laser welding. Fig. 7A is a schematic cross-sectional representation along the line VIIA-VIIA in Fig. 6. Fig.7B is a schematic cross-sectional representation along the line VIIB-VIIB in Fig. 6. Fig. 7C is a schematic cross-sectional representation along the line VIIIC-VIIIC in Fig. 6. Fig. 7D is a schematic cross-sectional representation along the line VIIID-VIIID in Fig. 6. Fig. 7A is a cross-sectional view near the starting point of the weld 230 described later, and Fig. 7C is a cross-sectional view near the endpoint of the weld 230 described later. Fig. 7B is a cross-sectional view in the middle between the starting point and the end point of the weld 230.

[0035] The following description details the features in the Fig.The heights Ha, Hb, and Hc of the weld 230 shown in Figures 7A to 7C are each referred to as weld height Ha, Hb, and Hc, respectively. The weld heights Ha, Hb, and Hc are collectively referred to as weld height H. The weld height H is the height in the Z-direction, measured from the surface of the copper plate 210 at any point along the longitudinal direction of the weld 230.

[0036] The widths Wa, Wb and WC of the weld seam 230 in the Fig. 7A to 7C are each designated as weld width Wa, Wb and Wc, respectively. The weld widths Wa, Wb and Wc are collectively designated as weld width W. The weld width is the width in the Y-direction at any point along the longitudinal direction of the weld 230.

[0037] In general, the proportion of light absorbed by a metal when light strikes it, i.e., the light absorption rate, changes depending on the wavelength of the light. Furthermore, the wavelength dependence of the light absorption rate is strongly influenced by the properties of the metal.

[0038] For example, the light absorption rate of iron and nickel increases with decreasing wavelength, as shown in Fig. Figure 3 illustrates this, however, the degree of change in the light absorption rate depending on the wavelength is small. Using iron as an example, the light absorption rate for laser light in the near-infrared range (typical wavelength in the near-infrared range: 1000 nm) is approximately 40%, and for laser light LB (typical wavelength of laser light LB: 445 nm) it is approximately 45%.

[0039] In this description, the term "near-infrared range" refers to the wavelength range from 900 nm to 2000 nm, where in Fig.3. The representative wavelength of the near-infrared range, 1000 nm, is represented by a dashed line. The wavelength of the laser beam LB is shown in Fig. 3 is also represented by a dashed line.

[0040] In contrast, the light absorption rate of copper increases rapidly at wavelengths below 800 nm. While the light absorption rate of laser light in the near-infrared range is below 10%, it rises to approximately 60% in the wavelength range of the laser beam LB.

[0041] This means that for workpieces 200 whose material is copper or an alloy with copper as the main component (hereinafter collectively referred to as copper-containing materials), the power of the laser light in the near-infrared range must be significantly increased during laser welding with near-infrared laser light due to the low light absorption rate. For copper-containing materials, a copper alloy with a copper content of at least 90% is preferable.

[0042] In this case, however, as already mentioned, there is a risk of severe spattering or of holes and cuts occurring at the welding point.

[0043] Therefore, in the present embodiment, the structure of the workpiece 200 can be simplified by laser welding according to the method described below, and the laser welding can be performed with low power of the laser beam LB. Furthermore, the connection quality at the joints can be improved and stabilized. The laser welding method described in the present embodiment is used, for example, for electrically connecting a motor winding and a conductor wire. Therefore, an increase in electrical resistance at the joints must be prevented, and high connection reliability must be ensured. In other words, the connection quality between the coil and the conductor must be high and stable. It is understood, however, that the laser welding method presented in this embodiment is not specifically limited to this application but can also be used for other applications.

[0044] In this embodiment, a workpiece 200 with a structure comprising a copper plate (plate material) 210 and a copper wire (wire material) 220 is directed onto the surface of the copper plate 210 by laser beams LB from the side of the surface of the copper wire 220 facing the bearing surface of the copper wire (wire material) 220 in the copper plate 210, in order to join the copper plate 210 and the copper wire 220.

[0045] First, a workpiece 200 is produced in which the copper wire 220 is attached in close contact with the surface of the copper plate 210, as shown in Fig. Figure 4 is shown. Subsequently, the workpiece 200 is arranged on a stage (not shown) of a laser welding device 100.

[0046] The laser oscillator 10 is activated to emit the laser beam LB from the laser head 30 while the laser head 30 is moved at a speed V along the welding direction WD. In this way, the laser beam LB moves along the longitudinal axis CC of the copper wire 220 at a speed V and is projected from the surface of the copper wire 220 onto the workpiece 200, striking the copper plate 210 and the copper wire 220. Hereinafter, the aforementioned speed V is referred to as the welding speed V.

[0047] The laser beam LB is not only moved at the welding speed V in the welding direction WD (X-direction), but is also scanned by the laser scanner 50 at the scan frequency fs in the Y-direction. For this reason, the laser beam LB, as in Fig.Figure 5A shows a sinusoidal scan of the surface of workpiece 200, viewed from the Z-direction. In the following description, the scan path of the laser beam LB directed at workpiece 200 is referred to as scan path ST.

[0048] In this case, the scan path ST of the laser beam LB is a sine wave with a scan amplitude A and a period T, whose line of symmetry (center line) is the central axis CC of the copper wire 220 in the Y direction. The scan amplitude A is set so that it is at least equal to the radius (D / 2) of the copper wire 220, i.e., equal to or greater than this radius (D / 2). In the Fig. In the example shown in 5A, the scan amplitude A is set so that it is larger than the radius (D / 2) of the copper wire 220.

[0049] The in Fig.The period T1 shown in Figure 5A corresponds, viewed from the Z-direction, to the half-life of the period during which the center of the laser beam LB passes only through the copper wire 220. If the period 2T1 is defined as the irradiation time of the copper wire section (2T1), the following equation (1) applies. Here, the period 2T1 is the period during which the laser beam LB passes only through the copper wire 220, or in other words, the irradiation time of the copper wire section 2T1 during which the laser beam LB illuminates the overlapping area between the copper wire 220 and the copper plate 210. α=100×(2T1) / (T / 2)=400×(T1 / T)(%)

[0050] Here, α is defined as the degree of irradiation of the copper wire.

[0051] The copper wire irradiation rate α is determined during a welding process in which the laser beam LB is scanned at a predetermined speed along the longitudinal axis of the copper wire 220 so that it travels back and forth several times, thereby crossing the width of the copper wire 220, and the laser beam LB is irradiated onto the copper plate 210 and the copper wire 220, and indicates the proportion of time in which the laser beam LB hits the overlap area between the copper plate 210 and the copper wire 220, relative to the predetermined scan period of the irradiation path on which the laser beam LB hits the copper plate 210 and the copper wire 220. More precisely, the copper wire irradiation rate α, as can be seen from equation (1), is the proportion of the time in which the laser beam LB shines onto the overlap area between the copper plate 210 and the copper wire 220 in relation to half the period (T / 2) of the sine wave (irradiation path of the laser).

[0052] The scan path ST of the laser beam LB irradiated onto the workpiece 200 is not on the in Fig. 5A shown is limited. For example, the scan path ST, as shown in Fig. As shown in Figure 5B, it can also be a triangular wave. In this case, the scan path ST of the laser beam LB is a triangular wave with a scan amplitude A and a period T, where the central axis CC of the copper wire 220 serves as the line of symmetry (center line) in the Y direction. The ratio between the scan amplitude A of the triangular wave and the radius (D / 2) of the copper wire 220 is as shown in Figure 5B. Fig. 5A is shown. If the scan path ST in question is a triangular wave, the copper wire irradiation rate α is understood as the fraction of the time in which the laser beam LB, in relation to half the period (T / 2) of the triangular wave (laser beam path), is essentially only irradiated on the overlapping area between the copper plate 210 and the copper wire 220.

[0053] When workpiece 200 is laser-welded using the method described above, the result is as shown in Fig. Figure 6 shows a weld seam 230 along the welding direction WD (X-direction). In the Fig. In the example shown in Figure 6, the most important welding parameters are as follows. First, the scan path ST of the laser beam LB is a triangular wave, the welding speed V is 10 mm / s, and the power of the laser beam LB is 400 W. The thickness t of the copper plate is 210 (see Figure 6). Fig. 4) is 0.2 mm and the diameter D of the copper wire is 220 (see Fig. 4) is 0.7 mm. The scan amplitude A was 1.4 mm, the scan frequency fs 100 Hz and the copper wire irradiation rate α 50 %.

[0054] As in the Fig. As shown in Figures 7A to 7C, fillets 231 were formed at both side ends of the weld 230 in the Y-direction, i.e., in the width direction of the weld 230. As shown in Fig.As shown in Figure 7D, fillets 232 were formed at the end sections along the welding direction WD of the weld 230, i.e. in the longitudinal direction of the weld 230 and near the end point.

[0055] As in Fig. As shown in Figure 7D, if the starting point of the laser beam LB irradiation of the workpiece 200 is taken as the starting point, the fillet 232 is formed in the welding direction WD from the starting point to the end point of the weld seam 230 such that the seam height H gradually decreases (see also Fig. 7A to 7C). Furthermore, as in Fig. Figure 6 shows that the outline of the edge region of weld 230 gradually becomes smoother from the periphery outwards. Furthermore, no tapering was observed near the starting point of weld 230. In other words, the appearance of weld 230 was very good (see Figure 6). Fig. 10).

[0056] This means that, in the present description, it is advantageous that the shape of the weld 230 is designed such that the previously mentioned rounding 232 gradually decreases in height from the starting point to the end point of the weld 230. Furthermore, as in the Fig. As shown in Figures 7A to 7C, it is advantageous that the previously mentioned rounding 231 at the lateral ends of the weld 230 is designed in the width direction of the weld 230 in such a way that it gradually decreases in height from the center of the weld 230 to the ends (Ha > Hb > Hc).

[0057] In the cross-section of the weld seam 230 along the welding direction WD, as in the example in Fig. As shown in Figure 7D, the angle between an imaginary line connecting the aforementioned start and end points and the surface of the copper plate 210 is defined as the weld inclination angle θ. Hereinafter, the cross-section in the XZ plane is referred to as the cross-sectional view.

[0058] The weld inclination angle θ is acute, and in the example in Fig. 7D, the weld inclination angle θ was more than 10 degrees and less than 20 degrees. [Effect etc.]

[0059] As explained above, the laser welding process according to this embodiment joins the copper wire (wire material) 220 and the copper plate (plate material) 210 at the point where they overlap, with a laser beam LB directed from the surface of the copper wire 220 onto the copper plate 210 and the copper wire 220.

[0060] The welding direction WD of the workpiece 200 is in the X direction, the normal direction of the bearing surface of the copper wire 220 on the copper plate 210 is in the Z direction and the direction that intersects the X and Z directions respectively is in the Y direction.

[0061] The laser beam LB is moved at a predetermined speed V (welding speed V) along the X-direction and through the central axis CC, which runs along the longitudinal direction of the copper wire 220, while the laser beam LB is moved back and forth along the Y-direction to beam the laser beam LB onto the copper wire 220 and the copper plate 210.

[0062] In the welding step, the laser beam LB is directed onto the workpiece 200 in such a way that it forms a sine or triangular wave which moves along the X-direction with the central axis CC of the copper wire 220 as the line of symmetry (center line).

[0063] The copper plate 210 and the copper wire 220 each consist of a copper material, i.e., copper or an alloy whose main component is copper. The wavelength of the laser beam LB is 445 nm. The wavelength of the laser beam LB should preferably be between 350 nm and 550 nm, even better between 400 nm and 500 nm.

[0064] According to this embodiment, by setting the wavelength of the laser beam LB to the aforementioned range, the light absorption rate for workpieces 200 made of copper materials can be increased. Therefore, a low-power laser beam LB can be used to perform an overlap weld between the copper wire 220 and the copper plate 210. For example, when laser light with a wavelength in the near-infrared range is used, a power of 1 kW or more is required, whereas with the laser beam LB of the wavelength used in this embodiment (445 nm), the power can be limited to a few hundred watts. This enables a thermally conductive connection and suppresses spatter formation. Furthermore, the heat input can be kept low, thereby reducing the thermal deformation of the workpiece 200.

[0065] By scanning the laser beam LB in the Y direction, as previously described, the molten metal in the weld pool can be distributed in the Y direction. This creates a fillet 231 on the side edges of the weld 230, the height of which gradually decreases from the center of the weld 230 to the ends.

[0066] Investigations by the inventors of this invention have revealed that using the scan path ST as a spin wave is not advantageous. A spin wave is a path generated by circular scanning of the laser beam LB in the welding direction WD. In this case, there is a period during which the laser beam LB moves backward along the welding direction WD. If, during this period, the copper plate 210 and the copper wire 220 are laser-welded to form the weld 230, the laser beam LB is again directed onto the previously formed weld 230. This disrupts the shape of the weld 230, which is undesirable.

[0067] Furthermore, the copper plate 210 and the copper wire 220 are at room temperature immediately before the start of welding. During the welding process, the laser beam LB is applied in the direction of the aforementioned endpoint. The laser beam LB is not only moved at the welding speed V in the welding direction WD (X-direction) but is also scanned in the Y-direction, so that it describes a sinusoidal or triangular wave on the surface of the workpiece 200. This causes heat to be stored in the workpiece 200, and the temperature rises. This means that during laser welding, the temperature is highest near the endpoint of the weld seam 230.As a result, the weld seam 230, melted and formed by the scanning of the laser beam LB described above, gradually spreads in the cross-sectional view near the endpoint of the weld seam 230, so that a fillet 232 is formed from the starting point to the endpoint of the weld seam 230, the height of which gradually decreases. That is, fillets 231 and 232 are formed at the edges of the weld seam 230, so that the height of the weld seam gradually decreases.

[0068] This prevents an area with a sudden narrowing from forming at the junction between the copper wire 220 and the copper plate 210, thus preventing an increase in electrical resistance at this junction.

[0069] Furthermore, according to this embodiment, the structure of workpiece 200 can be simplified compared to the conventional design disclosed in patent specification 1, and the quality of the joint can be improved and stabilized. This will be explained in more detail below.

[0070] Fig. Figure 8 is a schematic representation of the workpiece in conventional laser welding, and Fig. Figure 9 is a schematic representation of the workpiece after completion of conventional laser welding.

[0071] In the method disclosed in patent application 1, the copper terminals 240, between which the copper wire 220 is arranged, are pressed together and fixed, and then the laser beam LB is directed from above onto the copper terminals 240. Compared to simply placing the copper wire 220 onto the copper terminal 240, the amount of melt is increased at the contact point between the two, resulting in a larger weld bead 250 (see Fig. 9) forms and the copper wire 220 and the copper connection 240 can be reliably welded together.

[0072] However, this procedure can, as in Fig.Figure 8 shows that a gap forms between the copper wire 220 and the copper terminal 240. If the laser beam LB is shone down onto the copper terminal 240 in this state, the heat transfer from the copper terminal 240 to the copper wire 220 is insufficient, so that the two cannot be welded properly and welding defects may occur.

[0073] Furthermore, when laser welding the copper wire 220 and the copper terminal 240 using the method disclosed in patent document 1, the weld quality may be impaired, even if a large weld bead 250 is formed externally. For example, as in Fig. As shown in Figure 9, an internal gap 250a forms at the connection point between the copper wire 220 and the copper terminal 240, which, however, was not recognizable from the appearance of the weld bead 250, so that the connection quality was difficult to check.

[0074] According to the present embodiment, however, a good connection structure can be achieved with a simple construction in which the copper wire 220 is arranged on the surface of the copper plate 210. A method such as the pressing method disclosed in patent document 1 is not required. In addition, fillets 231, 232 are formed at the edge regions of the weld seam 230, the height of which gradually decreases. This prevents the formation of an internal gap 250a, as described in Fig. As shown in Figure 9, this can be prevented. Furthermore, the formation of areas that suddenly narrow at the junction between the copper wire 220 and the copper plate 210 can be prevented, thus preventing an increase in electrical resistance at this junction.

[0075] If the scan period of the laser beam LB is denoted by T and the time during which the laser beam LB illuminates the overlap region between the copper wire 220 and the copper plate 210 is denoted by 2T1, the copper wire irradiation rate α satisfies the relationship given in formula (1). The copper wire irradiation rate α is defined as the scan path ST of the laser beam LB and represents the fraction of the time during which the laser beam LB is essentially only illuminated in the overlap region between the copper plate 210 and the copper wire 220, based on one half-period (T / 2) of a sine or triangle wave. α=400×(T1 / T)(%)

[0076] In the aforementioned welding step, the laser beam LB is directed onto the workpiece 200 such that the copper wire irradiation rate α is between 33% and 75%. It is advantageous to direct the laser beam LB onto the workpiece 200 such that the copper wire irradiation rate α is between 50% and 75%.

[0077] In this way, the overlap area between the copper wire 220 and the copper plate 210 can be reliably melted. Since the molten metal spreads in the Y direction, a fillet 231 can also be reliably formed at both ends of the weld seam 230.

[0078] The scan amplitude A of the laser beam LB in the Y direction during the welding step is at least the radius (D / 2) of the copper wire 220. Furthermore, the scan frequency fs in the Y direction is preferably at least 100 Hz and at most 300 Hz, preferably at least 100 Hz and at most 200 Hz.

[0079] This prevents the formation of a suddenly tapered area at the junction between the copper wire 220 and the copper plate 210. Furthermore, the heat input at the reversal points of the scan path ST in the Y-direction is greater than at other points, thus preventing the ends of the fillets 231 at the edges of the weld 230 from becoming too steep. This prevents an increase in electrical resistance at the junction. If the scan frequency fs is too high, a point of sudden diameter reduction forms at the junction between the copper wire 220 and the copper plate 210. As a result, the electrical resistance at the junction between the copper plate 210 and the copper wire 220 rises above the permissible value. Conversely, if the scan frequency fs is too low, the ends of the fillets 231 at the edges of the weld 230 become too steep.This reduces the electrical conductivity at the junction between the copper plate 210 and the copper wire 220, and the electrical resistance at this junction increases above the permissible value. Furthermore, the connection strength at the junction deteriorates.

[0080] In the cross-sectional view, the angle between an imaginary line connecting the start and end points of the weld 230 and the surface of the copper plate 210 is called the weld inclination angle θ. In this case, it is advantageous to direct the laser beam LB onto the workpiece 200 such that the weld inclination angle θ is between 10 degrees and 20 degrees.

[0081] In this way, the electrical resistance of the connection point between the copper plate 210 and the copper wire 220 can be increased and a stable connection between the two can be established.

[0082] If the weld angle θ is too large, a fillet 232 cannot form, or a section of the copper wire 220 may become thinner. In this case, the electrical resistance at the junction between the copper plate 210 and the copper wire 220 will exceed the permissible value. Conversely, if the weld angle θ is too small, the weld height H will be too shallow. Again, in this case, the electrical resistance at the junction between the copper plate 210 and the copper wire 220 will exceed the permissible value.

[0083] In this embodiment, an example has been shown in which the cross-section of the copper wire 220 is circular, but the cross-section of the copper wire 220 can also have a different shape. For example, the cross-section can be elliptical or n-sided (where n is an integer greater than 3). Furthermore, the copper plate 210 must be flat at the junction with the copper wire 220, while the shape of the other parts is arbitrary.

[0084] The following section explains the present technology in more detail using exemplary embodiments. These exemplary embodiments serve only for illustration and do not represent a limitation of the present technology. [Examples of implementation]<Erstes Ausführungsbeispiel>

[0085] A workpiece 200 was prepared, in which a copper wire 220 was placed on the surface of a copper plate 210 made of pure copper (with a purity of at least 99.9%). The laser beam LB was moved at a welding speed V along the welding direction WD in the X-direction and through the central axis CC, which runs along the longitudinal direction of the copper wire 220, and was scanned back and forth in the Y-direction to direct the laser beam LB onto the copper wire 220 and the copper plate 210. This created a weld seam 230 on the surface of the workpiece 200.

[0086] The shape parameters of the workpiece 200 in the first embodiment were as follows. Initially, the thickness t of the copper plate 210 was 0.2 mm and the diameter D of the copper wire 220 was 0.7 mm. The parameter values ​​for the laser beam LB were as follows. Initially, the scan path ST of the laser beam LB was a sine wave and the welding speed V was 10 mm / s. The wavelength of the laser beam LB was 445 nm and the power 400 W. The scan amplitude A was 1.4 mm. Using these parameters, the copper wire irradiation rate α was 33%.

[0087] The scan frequency fs was set in three steps of 100 Hz, 200 Hz and 300 Hz, and in each case the laser beam LB was directed at the workpiece 200. <Zweites Ausführungsbeispiel>

[0088] With the exception that the scan path ST of the laser beam LB was a triangular wave, the workpiece 200 was irradiated with the laser beam LB using the same method and parameters as in the first embodiment, and weld seams 230 were formed on the surface of the workpiece 200. Since the scan path ST was changed from a sine wave to a triangular wave, the copper wire irradiation rate α was 50%. <Drittes Ausführungsbeispiel>

[0089] With the exception of the scan amplitude A of the laser beam LB, which was set to 0.934 mm, the laser beam LB was directed at the workpiece 200 using the same method and parameters as in the first embodiment, where the scan path ST was a sine wave, to create a weld seam 230 on the surface of the workpiece 200. Since the scan amplitude A was changed, the copper wire irradiation rate α was 54%. <Viertes Ausführungsbeispiel>

[0090] With the exception of the scan amplitude A of the laser beam LB, which was set to 0.934 mm, the laser beam LB was directed onto the workpiece 200 with a triangular wave using the same method and parameters as in the second embodiment to form a weld seam 230 on the surface of the workpiece 200. Since the scan amplitude A was changed, the copper wire irradiation rate α was 75%. <Erstes Vergleichsbeispiel>

[0091] In contrast to the first embodiment, the laser beam LB was not scanned in the Y direction, but was directed in a straight line (in a straight line) onto the workpiece 200 near the end of the copper wire 220 along the welding direction WD (X direction) in order to form a weld seam 230 on the surface of the workpiece 200.

[0092] The parameters that differ from the first embodiment are as follows. First, the scan path ST is a straight line, and the scan amplitude A and the scan frequency fs are both zero. In this case, the previously mentioned period T and the duration T1 are equal, so the copper wire irradiance α, which indicates the proportion of time during which the laser beam LB shines practically only on the overlapping area between the copper plate 210 and the copper wire 220, is 100%. The remaining parameters, including the shape and material of the workpiece 200, were the same as in the first embodiment, where the diameter D of the copper wire 220 was 0.7 mm. <Vergleich der Ergebnisse des ersten bis vierten Ausführungsbeispiels mit dem ersten Vergleichsbeispiel >

[0093] Fig.Figure 10 shows an example of the appearance of the workpiece after laser welding, and Table 1 shows the results of the evaluation of the appearance of the workpiece in the first four embodiments and the first comparison example.

[0096] [Table 1] Example 1 Example 2 Example 3 Example 4 Comparative example 1 Laser beam scanlocus sine wave Triangular wave sine wave Triangular wave Straight line (no scan) Scan amplitude A (mm) 1,4 1,4 0,934 0,934 0 Copper irradiance α (%) 33 50 54 75 100 Welding speed V (mm / sec) Frequency (Hz) Appearance rating result 10 0 - - - - Δ 100 × ⊚ ⊚ ⊚ - 200 × ⊚ ⊚ ⊚ - 300 × × Δ Δ -

[0094] Thickness of copper plate 210 t: 0.2 mm, diameter of copper wire 220 D: 0.7 mm

[0095] As in Fig. As shown in Figure 10, the appearance of workpiece 200 after laser welding was divided into four categories and evaluated. The top side in Fig. Figure 10 shows the surface of the copper plate 210, on which the copper wire 220 is arranged, as seen in the Z-direction. The side view shows the surface of the copper plate 210, on which the copper wire 220 is arranged, as seen at a certain angle in the Z-direction (oblique view).

[0096] In Fig.In the evaluation column on the far left, 10 examples of a deficient (×) appearance rating are shown. As can be clearly seen from the side view, in a deficient (×) appearance rating, the transition from the copper wire 220 to the weld seam 230 is suddenly narrower. This means that the electrical resistance can increase considerably at the connection point between the copper wire 220 and the copper plate 210.

[0097] In Fig. In the second column of the rating column, number 10 is shown as an example of an acceptable (Δ) result of the external assessment. Fig.10 is abbreviated as "acceptable". As can be clearly seen in the side view, the height H of the weld seam is lower with an acceptable (Δ) result of the external evaluation than in the cases described later (good (◯) and very good (⊚)). Compared to cases where the result of the external evaluation is "deficient" (×), however, the width of the transition area from the copper wire 220 to the weld seam 230 is greater. This means that although there is a risk of an increase in electrical resistance at the connection point between the copper wire 220 and the copper plate 210, this is within the permissible range in practical use and does not represent a significant impairment of the connection reliability.

[0098] In Fig.Figure 10 in the third column from the left shows an example of a good (◯) rating for external appearance. As can be clearly seen from the top and side views, the edge area of ​​weld 230 exhibits a contour with irregularities of the same size when the external appearance is rated good (◯). This is due to the laser beam LB being periodically moved back and forth in the Y direction.

[0099] In this case, however, there is no area where the transition from the copper wire 220 to the weld 230 becomes locally and abruptly thinner, nor is there an area where the weld height H drops off locally and abruptly, including the area in question. That is to say, although the weld 230 is not particularly visually appealing, it exhibits a periodic, uniform change in shape from beginning to end, so that no increase in electrical resistance above the permissible value is to be expected at the junction between the copper wire 220 and the copper plate 210, and the reliability of the connection is ensured.

[0100] In Fig. Number 10, on the far right of the rating field, shows an example of a very good (⊚) rating for physical appearance. This example corresponds to the one in Fig. 6.

[0101] As can be clearly seen from the top and sides, with a very good (⊚) result in the external evaluation, the contour of the weld 230 is gradually sloping and smooth towards the edges. Furthermore, at the transition point from the copper wire 220 to the weld 230, there are no points where the weld tapers abruptly, nor are there any points where the weld height H drops off locally. This means that the weld 230 is visually appealing and also ensures that the electrical resistance at the connection point between the copper wire 220 and the copper plate 210 does not exceed the permissible value, thus guaranteeing the reliability of the connection.

[0102] For example, the permissible value for the increase in electrical resistance is "5% for general applications and 1% for precision applications", with any increase above this permissible value being considered faulty.

[0103] Based on the in Fig. The results listed in Table 1 are explained using the 10 examples shown for the external appearance.

[0104] As shown in Table 1, the result of the external evaluation of the weld 230 in the first comparative example was within the permissible range (Δ). In the first embodiment, however, the result of the external evaluation of the weld 230 was unsatisfactory (×), regardless of the scan frequency fs. For the workpiece 200 with the structure described above, under the laser welding conditions specified in the first embodiment, the fusion of the overlap area between the copper wire 220 and the copper plate 210 was insufficient, and the copper wire irradiation rate α was also insufficient, so that the molten metal could not spread sufficiently in the Y direction. For this reason, areas with a sudden taper formed at the point where the copper wire 220 transitions into the weld 230, leading to a poor result (×) in the external evaluation.

[0105] Under the conditions of the second embodiment, however, the result of the optical evaluation was very good (⊚) at a scan frequency fs of 100 Hz and 200 Hz, while it was poor (×) at a scan frequency fs of 300 Hz. As already mentioned, an excessively high scan frequency fs leads to a significant narrowing at the point where the weld thread 220 transitions into the weld seam 230. At the irradiation intensity of the copper wire used in this case (α = 50%), a scan frequency fs of 300 Hz is too high for a satisfactory appearance.

[0106] Under the conditions shown in the third and fourth embodiments, however, the results of the optical evaluation were very good (⊚) at a scan frequency fs of 100 Hz and 200 Hz and within the permissible range (Δ) at a scan frequency fs of 300 Hz.

[0107] In summary, under the conditions of the first to fourth embodiments, with a diameter D of the copper wire 220 of 0.7 mm and a welding speed V of 10 mm / s, the laser welding conditions with a scan frequency fs in the range of 100 Hz to 200 Hz and a copper wire irradiation rate α of at least 50% and 75% or less are very good. Under these conditions, the weld seam 230 of the workpiece 200 has a very good appearance.

[0108] To evaluate the shape of the weld seam 230 after laser welding, the weld thickness H and the weld width W were evaluated.

[0109] Fig. Figure 11 shows the relationship between the scan frequency and the height of the weld in the middle position, and Fig. Figure 12 shows the relationship between the scan frequency and the width of the weld in the middle position.

[0110] Specifically, in Fig. 11 the height Hb of the weld (see Fig. 7B) in the middle position of the weld seam 230, which was formed under the conditions of the first to fourth embodiments and under the conditions of the first comparative example, applied as a function of the scan frequency fs of the laser LB.

[0111] Fig. Figure 12 is a diagram showing the weld seam 230 formed in the first to fourth embodiments and in the first comparative example under the specified conditions in the middle position (see Figure 12). Fig. 7B) as a function of the scan frequency fs of the laser LB. In the figures, the individual points are labeled with symbols classified according to the copper wire irradiation rate α.

[0112] In the Fig. 11 and Fig.12. The areas outlined with dashed lines correspond to the cases where the appearance of the weld 230 was very good (⊚). That is, if the diameter D of the copper wire 220 is 0.7 mm, the weld 230 should be formed such that the weld thickness Hb in the middle position is at least 0.30 mm and at most 0.60 mm, and the weld width Wb in the middle position is at least 1.20 mm and at most 1.80 mm.

[0113] In other words, the height of the weld 230, relative to the surface of the copper plate (plate material) 210, wherein the height of the weld 230 at the midpoint between its start and end points is referred to as weld height Hb and the diameter of the copper wire (wire material) is referred to as diameter D, preferably satisfies the relationship 0.43D≤Hb≤0.86D

[0114] If the width of the weld seam 230 in the Y-direction at the midpoint between the starting point and the end point of the weld seam 230 is designated as weld width Wb, then 1.71D≤Wb≤2.57D

[0115] If the height Hb and the width Wb of the weld at the middle position are outside the above-mentioned range, the electrical resistance at the junction between the copper wire 220 and the copper plate 210 may increase above the permissible value, which may lead to an electrical connection fault.

[0116] The data obtained actually show that, with a diameter D of the copper wire 220 of 0.7 mm, the weld 230 is preferably designed such that the height Hb of the weld in the middle position is at least 0.38 mm and at most 0.51 mm and the width Wb of the weld in the middle position is at least 1.39 mm and at most 1.70 mm.

[0117] In other words, it is advantageous if the respective relationships are fulfilled: 0.54D≤Hb≤0.74D 1.99D≤Wb≤2.43D

[0118] For workpieces 200 with different conditions, as shown in embodiments 1 to 4, weld seams 230 were formed on the surface of the workpieces 200 by changing the laser welding conditions and their appearance was evaluated. <Fünftes Ausführungsbeispiel>

[0119] A workpiece 200 was prepared, in which a copper wire 220 was placed on the surface of a copper plate 210. The laser beam LB was moved at a welding speed V along the welding direction WD in the X-direction and through the central axis CC, which runs along the longitudinal direction of the copper wire 220, while being scanned back and forth in the Y-direction to direct the laser beam LB onto the copper wire 220 and the copper plate 210. This created a weld seam 230 on the surface of the workpiece 200.

[0120] The workpiece 200, i.e., the materials of the copper plate 210 and the copper wire 220, were the same in the fifth embodiment as in the first embodiment. The shape parameters were as follows: The thickness t of the copper plate 210 was 0.2 mm and the diameter D of the copper wire 220 was 0.3 mm. The parameter values ​​for the laser beam LB were as follows: First, the scan path ST of the laser beam LB was a sine wave and the welding speed V was 20 mm / s. The wavelength of the laser beam LB was 445 nm and the power 270 W. The scan amplitude A was 0.6 mm. Using these parameters, the copper wire irradiation rate α was 33%.

[0121] The scan frequency fs was set in three steps of 100 Hz, 200 Hz and 300 Hz, and in each case the laser beam LB was irradiated onto the workpiece 200. <Sechstes Ausführungsbeispiel>

[0122] With the exception that the scan path ST of the laser beam LB was a triangular wave, the laser beam LB was irradiated onto the workpiece 200 using the same methods and parameters as in the fifth embodiment to form a weld seam 230 on the surface of the workpiece 200. Since the scan path ST was changed from a sine wave to a triangular wave, the copper wire irradiation rate α was 50%. <Siebtes Ausführungsbeispiel>

[0123] With the exception of the scan amplitude A of the laser beam LB, which was set to 0.4 mm, the laser beam LB was directed at the workpiece 200 using the same method and parameters as in the fifth embodiment, where the scan path ST of the laser beam LB was a sine wave, to create a weld seam 230 on the surface of the workpiece 200. Due to the change in scan amplitude A, the copper wire irradiation rate α was 54%. <Achtes Ausführungsbeispiel>

[0124] With the exception of the scan amplitude A of the laser beam LB, which was set to 0.4 mm, the laser beam LB was directed onto the workpiece 200 with a triangular wave using the same method and parameters as in the sixth embodiment to create a weld seam 230 on the surface of the workpiece 200. Due to the change in the scan amplitude A, the copper wire irradiation rate α was 75%. <Neuntes Ausführungsbeispiel>

[0125] With the exception of the welding speed V of 30 mm / s, the laser beam LB was directed onto the workpiece 200 with a sine wave using the same method and parameters as in the fifth embodiment to form a weld seam 230 on the surface of the workpiece 200. Therefore, the copper wire irradiation rate α in this case was also 33%, as in the fifth embodiment. <Zehntes Ausführungsbeispiel>

[0126] With the exception of the welding speed V of 30 mm / s, the laser beam LB was directed onto the workpiece 200 with a triangular wave using the same method and parameters as in the sixth embodiment to form a weld seam 230 on the surface of the workpiece 200. Therefore, the copper wire irradiation rate α in this case was also 50% as in the sixth embodiment. <Elftes Ausführungsbeispiel>

[0127] With the exception of the welding speed V of 30 mm / s, the laser beam LB was directed onto the workpiece 200 with a sine wave using the same method and parameters as in the seventh embodiment to form a weld seam 230 on the surface of the workpiece 200. Therefore, the copper wire irradiation rate α in this case was also 54% as in the seventh embodiment. <Zwölftes Ausführungsbeispiel>

[0128] With the exception of the welding speed V of 30 mm / s, the laser beam LB was directed onto the workpiece 200 with a triangular wave using the same method and parameters as in embodiment 8 to form a weld seam 230 on the surface of the workpiece 200. Therefore, the copper wire irradiation rate α was also 75% in this case, as in embodiment 8. <Zweites Vergleichsbeispiel>

[0129] In contrast to the fifth embodiment, the laser beam LB was not scanned in the Y direction, but was directed in a straight line (in a straight line) onto the workpiece 200 near the end of the copper wire 220 along the welding direction WD (X direction) in order to form a weld seam 230 on the surface of the workpiece 200.

[0130] The parameters that differ from the fifth embodiment are as follows. First, the scan path ST is rectilinear, and the scan amplitude A and the scan frequency fs are both zero. In this case, the previously mentioned period T and the duration T1 are identical, so the copper wire irradiation rate α is 100%. The remaining parameters, including the shape and material of the workpiece 200, are identical to those of the fifth embodiment, where the diameter D of the copper wire 220 is 0.3 mm. <Drittes Vergleichsbeispiel>

[0131] With the exception of the welding speed V of 30 mm / s, the same procedures and parameters as in the second comparative example were used to project a linear (straight) line with the laser beam LB onto the workpiece 200 near the end of the copper wire 220 along the welding direction WD (X-direction) and to form a weld seam 230 on the surface of the workpiece 200. Therefore, the irradiation rate α of the copper wire was also 100% in this case, as in the second comparative example. <Vergleich der Ergebnisse der Ausführungsbeispiele 5 bis 8 mit denen des zweiten Vergleichsbeispiels und der Ausführungsbeispiele 9 bis 12 mit denen des dritten Vergleichsbeispiels>

[0132] Table 2 shows the results of the optical evaluation of the workpieces in embodiments 5 to 8 and the second comparative example. Table 3 shows the results of the optical evaluation of the workpieces in embodiments 9 to 12 and the third comparative example. The optical evaluation was performed using the following methods: Fig. The classification shown in section 10 is used.

[0135] [Table 2] Example 5 Example 6 Example 7 Example 8 Comparative example 2 Laser beam scanlocus sine wave Triangular wave sine wave Triangular wave Straight line (no scan) Scan amplitude A (mm) 0,6 0,6 0,4 0,4 0 Copper irradiance level α (%) 33 50 54 75 100 Welding speed V (mm / sec) Frequency (Hz) Appearance rating result 20 0 - - - - × 100 ⊚ ◯ △ △ - 200 ⊚ ⊚ ⊚ △ - 300 ⊚ ⊚ ⊚ ⊚ -

[0133] Thickness of copper plate 210 t: 0.2 mm, diameter of copper wire 220 D: 0.3 mm

[0136] [Table 3] Example 9 Example 10 Example 11 Example 12 Comparative example 3 Laser beam scanlocus sine wave Triangular wave sine wave Triangular wave Straight line (no scan) Scan amplitude A (mm) 0,6 0,6 0,4 0,4 0 Copper irradiance α (%) 33 50 54 75 100 Welding speed V (mm / sec) Frequency (Hz) Appearance rating result 30 0 - - - - × 100 ◯ ◯ ◯ ◯ - 200 ⊚ ⊚ ⊚ ⊚ - 300 △ ⊚ ⊚ ⊚ -

[0134] Thickness of copper plate 210 t: 0.2 mm, diameter of copper wire 220 D: 0.3 mm

[0135] As shown in Tables 2 and 3, the result of the external evaluation of weld 230 was unsatisfactory (×) under the conditions specified in comparison examples 2 and 3. This means that the external condition of weld 230 did not improve in either case, at welding speeds V of 20 mm / s and 30 mm / s, if no reciprocating motion in the Y direction was performed.

[0136] Under the conditions specified in the fifth embodiment, the result of the optical evaluation of the weld 230 was very good (⊚), regardless of the scan frequency fs. However, under the conditions specified in the sixth to eighth embodiments, the result of the optical evaluation of the weld 230 tended to change depending on the scan frequency fs. At a scan frequency fs of 100 Hz, the results of the optical evaluation of the weld 230 were good (◯) under the conditions shown in the sixth embodiment, while under the conditions shown in the seventh and eighth embodiments, they were only within the acceptable range (△). At a scan frequency fs of 200 Hz, the results of the optical evaluation of the weld 230 were very good (⊚) under the conditions of Examples 6 and 7, while under the conditions of Example 8, they were within the permissible range (△).At a scan frequency fs of 300 Hz, the results of the optical evaluation of weld 230 were very good under all conditions shown in examples 6 to 8 (⊚).

[0137] These results indicate that at a welding speed V of 20 mm / s, the results of the optical evaluation of weld 230 tended to improve with an increasing scan frequency fs from 100 Hz to 300 Hz. Considering the copper wire irradiation rate α, it was found that the results of the optical evaluation of weld 230 tended to improve with a decreasing copper wire irradiation rate α from 75% to 33%.

[0138] For a copper wire diameter D of 0.3 mm and a welding speed V of 20 mm / s, a copper wire irradiation rate α of 50% or less is advantageous at a scan frequency fs of 100 Hz, with a copper wire irradiation rate α of 33% being even more advantageous. At a scan frequency fs of 200 Hz, a copper wire irradiation rate α of 33% or more and 75% or less is advantageous, with a copper wire irradiation rate α of 33% or more and 54% or less being even more advantageous. At a scan frequency fs of 300 Hz, a copper wire irradiation rate α of 33% or more and 75% or less is advantageous.

[0139] Under the conditions shown in the ninth embodiment, the results of the optical evaluation of the weld 230 changed depending on the scan frequency fs. As can be seen from Table 3, the evaluation of the appearance of the weld 230 was good (◯) at a scan frequency fs of 100 Hz, while it was very good (⊚) at a scan frequency fs of 200 Hz, indicating a tendency towards improvement in the appearance evaluation. However, at a scan frequency fs of 300 Hz, the evaluation of the appearance of the weld 230 was in the acceptable range (△) and thus deteriorated slightly.

[0140] Furthermore, under the conditions specified in Examples 10 to 12, a tendency was observed for the results of the external evaluation of weld 230 to change depending on the scan frequency fs. At a scan frequency fs of 100 Hz, the results of the external evaluation of weld 230 were good under all conditions specified in Examples 10 to 12 (◯). Increasing the scan frequency fs to 200 Hz resulted in very good results for the external evaluation of weld 230 under all conditions of embodiments 10 to 12 (⊚), and a tendency for the external evaluation results to improve was observed. At a scan frequency fs of 300 Hz, the same results were obtained as at a scan frequency fs of 200 Hz. That is, under all conditions shown in embodiments 10 to 12, the result of the external evaluation of weld 230 was very good (⊚).

[0141] These results indicate that the evaluation of the optics of the weld seam 230 with a diameter D of the copper wire 220 of 0.3 mm and a welding speed V of 30 mm / s is not significantly influenced by the copper wire irradiation rate α.

[0142] Furthermore, for a copper wire diameter D of 0.3 mm and a welding speed V of 30 mm / sec at a scan frequency fs of 100 Hz and 200 Hz, it can be assumed that the copper wire irradiation rate α is better at a scan frequency fs of 200 Hz than at a scan frequency fs of 100 Hz, and more favorable at a scan frequency fs of 200 Hz than at a scan frequency fs of 100 Hz. At a scan frequency fs of 100 Hz, a copper wire irradiation rate α of 33% or more and 75% or less is advantageous, and at a scan frequency fs of 300 Hz, a copper wire irradiation rate α of 50% or more and 75% or less is more advantageous.

[0143] The evaluation results of embodiments 5 to 12 show that, with a diameter D of the copper wire 220 of 0.3 mm, the external evaluation of the weld 230 is generally very good (⊚) when the scan frequency fs is set to 200 Hz or more and 300 Hz or less. It was also suspected that if the scan frequency fs is too high compared to this range, a point of significant diameter reduction occurs at the junction between the copper wire 220 and the copper plate 210. Consequently, it was suspected that the electrical resistance at the junction between the copper plate 210 and the copper wire 220 would exceed the permissible value. Conversely, if the scan frequency fs was too low, it was assumed that the ends of the fillet 231 at the edges of the weld 230 would become too steep.

[0144] Furthermore, under the conditions shown in Examples 1 to 12, the external evaluation of weld 230 was very good (⊚) when the previously mentioned weld inclination angle θ was between 11 degrees and 17 degrees. That is, the preferred range for the weld inclination angle θ is between 10 degrees and 20 degrees, with a weld inclination angle θ between 11 degrees and 17 degrees being even more favorable. [Commercial Applicability]

[0145] The laser welding process described here allows for a simplification of the workpiece structure and welding at lower power levels when laser welding copper alloys. This stabilizes the quality of the welds, which is advantageous for commercial applications. [Explanation of symbols] 10 Laser oscillator 20 Optical fiber 30 laser heads 40 Collimator lens 50 laser scanners 51 First electroplating mirror 52 Second electroplating mirror 60 fθ lens 70 robots 71 robot arm 72 joint 80 Control unit 100 laser welding devices 200 workpieces 210 copper plate (plate material) 220 copper wire (wire material) 230 weld seam 231 Fillet (Latitude) 232 Fillet (lengthwise) 240 copper connections 250 sweat beads 250a Inner gap LB Laser Light ST Scan path of the laser beam QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2008-010753 A

[0005] JP 2008-006472 A

[0005]

Claims

[1] Laser welding process in which a workpiece with an area where a wire material and a sheet material are superimposed is irradiated with laser light from the surface of the wire material in order to join the sheet material and the wire material together, wherein The welding direction of the workpiece is an X-direction, the normal direction of the contact surface of the wire material on the plate material is a Z-direction, and a direction intersecting with the X- and Z-directions is a Y-direction. wherein the laser welding process comprises at least one welding step in which the laser beam is moved at a predetermined speed along the X-direction and through the central axis of the wire in the longitudinal direction of the wire, wherein the laser beam is scanned back and forth along the Y-direction so that it crosses the wire, and the laser beam irradiates the wire material and the sheet material, characterized by, that in the welding step the laser radiation irradiates the workpiece in such a way that it forms a sine or triangular wave which extends along the X-direction with the central axis of the wire material as a line of symmetry, wherein a proportion of the time in which the laser beam hits the overlap area of ​​wire material and plate material, in relation to a predetermined scan period of the irradiation path of the laser beam hitting the wire material and the plate material, is expressed by a predetermined wire irradiance α. [2] Laser welding method according to claim 1, wherein if the scan period of the laser light is T and the time in which the laser light beam hits the overlap area of ​​wire material and plate material is 2T1, the wire irradiance α is given in formula (1) α=400×(T1 / T)(%) The specified relationship is fulfilled. [3] Laser welding method according to claim 1 or 2, wherein in the welding step the wire irradiance α is set to be 33% or more and 75% or less. [4] Laser welding method according to claim 1 or 2, wherein in the welding step the wire irradiance α is set to be 50% or more and 75% or less. [5] Laser welding method according to claims 2 to 4, wherein in the welding step a scan amplitude of the laser beam in the Y direction is greater than the radius of the wire and a scan frequency of the laser beam in the Y direction is at least 100 Hz and at most 300 Hz. [6] Laser welding method according to claim 5, wherein the scan frequency in the welding step is 100 Hz or more and 200 Hz or less. [7] Laser welding method according to claim 1, wherein after completion of the welding step a weld seam is formed on the surface of the workpiece, wherein a starting point of the irradiation of the workpiece with the laser beam serves as the starting point and an end of the weld seam as the end point, a fillet is formed in the vicinity of the end point of the weld seam, wherein the fillet is designed in the cross-sectional view such that its height gradually decreases from the starting point to the end point. [8] Laser welding process according to claim 7, where, from a cross-sectional perspective, an angle between a virtual line connecting the start point and the end point and the surface of the plate material is defined as a weld inclination angle θ, wherein the laser beam is directed onto the workpiece in such a way that the weld seam inclination angle θ is 10 degrees or more and 20 degrees or less. [9] Laser welding method according to claim 8, wherein the laser beam is directed onto the workpiece such that the weld angle θ is 11 degrees or more and 17 degrees or less. [10] Laser welding process according to claim 7, where the height of the weld seam, relative to the surface of the plate material, at an intermediate position between the starting point and the end point of the weld seam is called weld height Hb and the diameter of the wire material is called diameter D. 0.43D≤Hb≤0.86D applies. [11] Laser welding method according to claim 7, wherein the width of the weld seam in the Y direction at an intermediate position between the starting point and the end point of the weld seam is called the weld width Wb and the diameter of the wire material is called the diameter D. 1.71D≤Wb≤2.57D (3) applies. [12] Laser welding method according to any one of claims 1 to 11, wherein the sheet material and the wire material each consist of copper or an alloy containing copper as the main component, and where the wavelength of the laser light is 350 nm or more and 550 nm or less. [13] Laser welding method according to claim 12, wherein the wavelength of the laser light is 400 nm or more and 500 nm or less.

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