JP2024076250A - Laser welding method and laser welding device - Google Patents

Abstract

To obtain, for instance, a laser welding method and a laser welding device which are improved and new.SOLUTION: A laser welding method includes, for instance, a step of irradiating a first surface facing a first direction at an opposite side to a conductor of a terminal part with a laser beam to form a molten pool penetrating the terminal part from the first surface and reaching the conductor, and a step of cooling and solidifying the molten pool to form a welded part. In the step of forming the molten pool, a non-molten part of the conductor is intervened between a first portion and a tip part in an opposite direction to the first direction of the molten pool, and the first surface is irradiated with a laser beam in a condition that Dp as a depth along the first direction of the molten pool satisfies the following formula (1-1) Dp<T1+T2-Tmax...(1-1). [Here, T1 is a thickness of the terminal part along the first direction; T2 is a thickness of the conductor along the first direction; and Tmax is a maximum value of a thickness of the non-molten part causing a characteristic change of the first portion by heat conducted to the first portion from the molten pool via the non-molten part.]SELECTED DRAWING: Figure 1

Description

The present invention relates to a laser welding method and a laser welding device.

Conventionally, semiconductor devices have been known that have conductor connection parts that are joined internally by laser welding (for example, see Patent Document 1).

Patent No. 5633581

When welding conductors together, it is important not only to ensure the required joint strength, but also to avoid causing thermal damage to the parts that come into contact with the conductors.

Therefore, one of the objectives of the present invention is to provide a new and improved laser welding method and laser welding apparatus that, for example, makes it possible to suppress the thermal effects on the parts in contact with the conductors when joining the conductors by laser welding.

The laser welding method of the present invention is, for example, a welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the method including the steps of overlapping the terminal portion with the conductor in a state of contacting the conductor in the first direction, irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool that penetrates the terminal portion from the first surface to the inside of the conductor, and cooling and solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, a non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction, and a depth Dp of the molten pool along the first direction is determined to be greater than or equal to the following formula (1-1):
Dp<T1+T2-Tmax ... (1-1)
(where T1 is the thickness of the terminal portion along the first direction, T2 is the thickness of the conductor along the first direction, and Tmax is the maximum thickness of the non-melted portion at which a change in characteristics of the first portion occurs due to heat conducted from the molten pool to the first portion via the non-melted portion). The laser light is irradiated to the first surface under the condition that satisfies the following:

In the laser welding method, in the step of forming the molten pool, the Dp is expressed by the following formula (2-1):
Dp>Dmin ... (2-1)
The first surface may be irradiated with the laser light under the condition that Dmin is the minimum depth at which a required joining strength between the conductor and the terminal portion by the weld is obtained.

In the laser welding method, the Tmax may be 20 μm.

In the laser welding method, the Dmin may be 50 μm.

In the laser welding method, the conductor may be made of a copper-based material.

In the laser welding method, the first portion may be made of ceramic, and Tmax may be a thickness at which the maximum temperature of the first portion during the process of forming the molten pool is the thermal shock resistance temperature of the ceramic.

In the laser welding method, the circuit board may be a silicon nitride board.

In the laser welding method, the first portion may include a synthetic resin material, and Tmax may be a thickness at which the maximum temperature of the first portion during the process of forming the molten pool is the heat resistance temperature of the synthetic resin material.

In the laser welding method, the circuit board may be a glass epoxy resin board.

In the laser welding method, in the step of forming the molten pool, the irradiation energy E of the laser light on the first surface is expressed by the following formula (3-1):
E = (Dp + C1) / C2 ... (3-1)
The first surface may be irradiated with the laser light under the condition that satisfies the following formula: (where C1 and C2 are coefficients).

In the laser welding method, when the width of the laser light spot formed on the first surface is 100 [μm], the irradiation energy is E [J], and the depth is Dp [μm], C1 may be 21 and C2 may be 135.

In the laser welding method, the laser light may be scanned on the first surface, and the scanning speed of the laser light on the first surface may be 100 mm/s or more and 800 mm/s or less.

In the laser welding method, the scanning speed may be 300 mm/s or more and 600 mm/s or less.

In the laser welding method, the laser light may include a first laser light having a wavelength of 800 nm or more and a second laser light having a wavelength of 550 nm or less.

In the laser welding method, the wavelength of the laser light may be 400 nm or more.

Further, the laser welding method of the present invention is, for example, a welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the method including the steps of overlapping the terminal portion in a state of contact with the conductor in the first direction, irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool that penetrates the terminal portion from the first surface to the inside of the conductor, and cooling and solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, a non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction, and a depth Dp of the molten pool along the first direction is determined to be smaller than the depth Dp of the molten pool as shown in the following formula (1-2):
Dp<T1+T2-20 ... (1-2)
The first surface is irradiated with the laser light under the condition that T1 is the thickness of the terminal portion along the first direction, and T2 is the thickness of the conductor along the first direction.

In the laser welding method, in the step of forming the molten pool, the Dp is expressed by the following formula (2-2):
Dp>50 ... (2-2)
The first surface may be irradiated with the laser light under the condition that:

In the laser welding method, the laser light may include a first laser light having a wavelength of 800 nm or more and a second laser light having a wavelength of 550 nm or less.

In the laser welding method, the wavelength of the laser light may be 400 nm or more.

The laser welding apparatus of the present invention is, for example, a welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the welding method including the steps of overlapping the terminal portion with the conductor in a state of contacting the conductor in the first direction, irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool that penetrates the terminal portion from the first surface to the inside of the conductor, and cooling and solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, a non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction, and a depth Dp of the molten pool along the first direction is determined to be greater than or equal to the following formula (1-1):
Dp<T1+T2-Tmax ... (1-1)
(where T1 is the thickness of the terminal portion along the first direction, T2 is the thickness of the conductor along the first direction, and Tmax is the maximum value of the thickness of the non-melted portion at which a change in characteristics of the first portion occurs due to heat conducted from the molten pool to the first portion via the non-melted portion), the laser welding apparatus performs a welding method in which the laser light is irradiated to the first surface under conditions satisfying the following:

The present invention provides a new and improved laser welding method and laser welding apparatus that, for example, can suppress the thermal effects on the area in contact with the conductors when joining conductors together by laser welding.

FIG. 1 is a schematic diagram illustrating an example of a configuration of a laser welding apparatus that performs a laser welding method according to a first embodiment. FIG. 2 is a graph showing the light absorptance of each metal material versus the wavelength of the irradiated laser light. FIG. 3 is a schematic plan view showing an example of the shape of a laser light spot on the surface of a processing object formed by the laser welding device of the first embodiment. FIG. 4 is an exemplary flowchart showing the steps of the laser welding method according to the embodiment. FIG. 5 is an exemplary schematic cross-sectional view of a molten pool formed by the laser welding method of the first embodiment. FIG. 6 is an exemplary graph showing the relationship between the irradiation energy of the laser beam and the depth of the molten pool in the laser welding method according to the embodiment. FIG. 7 is an exemplary schematic diagram of a laser welding apparatus that performs the laser welding method according to the second embodiment. FIG. 8 is an explanatory diagram showing the concept of the principle of the diffractive optical element included in the laser welding apparatus of the second embodiment. FIG. 9 is a schematic plan view showing an example of the shape of a laser light spot on the surface of a processing object formed by the laser welding device of the second embodiment.

Below, exemplary embodiments of the present invention are disclosed. The configurations of the embodiments shown below, and the actions and results (effects) brought about by said configurations, are merely examples. The present invention can also be realized with configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

The embodiments shown below have similar configurations. Therefore, according to the configuration of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, below, the similar configurations are given the same reference numerals, and duplicate explanations may be omitted.

In addition, in each figure, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect with each other and are perpendicular to each other. The Z direction is, for example, the normal direction of the surface (machining surface) of the workpiece W.

In addition, in this specification, ordinal numbers are used for convenience to distinguish parts, directions, etc., and do not indicate priority or order, nor do they limit the number.

[First embodiment]
[Laser welding equipment]
1 is a schematic diagram of a laser welding apparatus 100A (100) according to a first embodiment. As shown in FIG. 1, the laser welding apparatus 100 includes laser devices 111 and 112, an optical fiber 130, an optical head 120A (120), and a position adjustment mechanism 140.

The laser device 111 has a laser oscillator as a light source. As an example, the laser device 111 is configured to be able to output laser light with a power of several kW. The laser device 111 may also be configured to have multiple semiconductor laser elements therein, for example, and to be able to output multi-mode laser light with a power of several kW as the total output of the multiple semiconductor laser elements. The laser device 111 may also be equipped with various laser light sources such as a fiber laser, a YAG laser, a disk laser, etc.

The laser device 111 outputs laser light having a wavelength of, for example, 800 nm or more and 1200 nm or less. The laser device 111 may also be referred to as a first laser device, and the laser oscillator of the laser device 111 may also be referred to as a first laser oscillator. The laser light output by the laser device 111 may also be referred to as a first laser light.

The laser device 112 also has a laser oscillator as a light source. As an example, the laser device 112 has multiple semiconductor laser elements inside and is configured to output multi-mode laser light with a power of several kW as the total output of the multiple semiconductor laser elements.

The laser device 112 outputs laser light with a wavelength of, for example, 550 nm or less. The wavelength of the laser light is preferably 400 nm or more and 500 nm or less. The laser device 112 may also be referred to as a second laser device, and the laser oscillator of the laser device 112 may also be referred to as a second laser oscillator. The laser light output by the laser device 112 may also be referred to as a second laser light.

The optical fiber 130 guides the laser light output from the laser devices 111 and 112 to the optical head 120.

The optical head 120 is an optical device for irradiating the laser light input from the laser devices 111 and 112 via the optical fiber 130 toward the workpiece W. The optical head 120 includes a collimator lens 121 (121-1, 121-2), a mirror 123, a filter 124, a galvanometer scanner 126, and a condenser lens 122. The collimator lens 121, the mirror 123, the filter 124, the galvanometer scanner 126, and the condenser lens 122 may also be referred to as optical components.

The collimating lens 121 collimates the laser light input via the optical fiber 130. The collimated laser light becomes parallel light.

Mirror 123 reflects the laser light that has been collimated by collimator lens 121-1. The laser light reflected by mirror 123 travels toward filter 124. Depending on the layout of the optical components in optical head 120, mirror 123 may not be necessary.

Filter 124 is a high-pass filter that transmits the laser light output by laser device 111 and reflects the laser light output by laser device 112 without transmitting it.

The laser light that passes through the filter 124 travels toward the galvanometer scanner 126. The galvanometer scanner 126 has two mirrors 126a and 126b, and is a device that can control the angles of the two mirrors 126a and 126b to move the irradiation position of the laser light L on the surface of the workpiece W and scan the surface with the laser light L. The angles of the mirrors 126a and 126b can each be changed by an actuator (not shown) including, for example, a motor.

The focusing lens 122 focuses the laser light that has passed through the galvano scanner 126 and irradiates it as laser light L (output light) onto the workpiece W. The laser light output from the optical head 120 and irradiated onto the workpiece W contains two laser lights with different wavelengths, i.e., the laser light output by the laser device 111 and the laser light output by the laser device 112.

The position adjustment mechanism 140 is configured to be able to change the relative position of the optical head 120 with respect to the workpiece W.

The laser welding device 100 can scan a spot of laser light L on the surface of the workpiece W by operating at least one of the galvanometer scanner 126 and the position adjustment mechanism 140. The galvanometer scanner 126 and the position adjustment mechanism 140 can also be referred to as a scanning mechanism.

[Processing target]
The processing object W includes a conductor 12 provided on a circuit board 10 and a terminal portion 21 of a conductive member 20. The conductor 12 and the terminal portion 21 are integrated by a welding process using the laser welding device 100 to form a circuit board assembly 1. The circuit board assembly 1 includes the circuit board 10 provided with the conductor 12 and the conductive member 20 having the terminal portion 21.

The circuit board 10 has an insulator 11 and a conductor 12. The circuit board 10 is, for example, a printed wiring board.

The insulator 11 is made of, for example, a ceramic such as silicon nitride or a glass epoxy resin. That is, the circuit board 10 is, for example, a ceramic board or a glass epoxy resin board. However, the insulator 11 is not limited to this and may be made of other materials.

The conductor 12 is made of a material having a relatively high electrical conductivity. As an example, the conductor 12 is made of a copper-based metal material such as pure copper or a copper alloy. However, the conductor 12 is not limited to this, and may be made of other metal materials.

The insulator 11 has a plate-like shape and crosses the Z direction and is perpendicular to it. The insulator 11 also has a surface 11a and a surface 11b. The surface 11a faces in the opposite direction to the Z direction, crosses the Z direction and is perpendicular to it. The surface 11b faces the Z direction, crosses the Z direction and is perpendicular to it. The insulator 11 is an example of a first portion.

The conductor 12 is integrated with the insulator 11 and has a surface 12a exposed in the Z direction. The surface 12a faces the Z direction and crosses and is perpendicular to the Z direction. The surface 12a is approximately flush with the surface 11a or protrudes in the Z direction from the surface 11a. The portion of the conductor 12 that is welded to the terminal portion 21 overlaps with the insulator 11 in the Z direction. Note that the conductor 12 is not limited to this, and may be a semiconductor device such as a switching element mounted on the circuit board 10, or a conductor of an electrical component or electronic component. In this case, the surface 12a becomes the surface of the conductor of the semiconductor device, electrical component, or electronic component mounted on the circuit board 10.

The conductive member 20 has a terminal portion 21. The terminal portion 21 has a plate-like shape with a substantially constant thickness, and intersects with and is perpendicular to the Z direction. The terminal portion 21 also has a surface 21a and a surface 21b. Surface 21a faces in the opposite direction to the Z direction, and intersects with and is perpendicular to the Z direction. Surface 21b faces in the Z direction, and intersects with and is perpendicular to the Z direction. Surface 21b is an example of a first surface.

The conductive member 20 is made of a material having relatively high electrical conductivity and relatively high thermal conductivity. As an example, the conductive member 20 is made of a copper-based metal material such as pure copper or a copper alloy. However, the conductor 12 is not limited to this and may be made of other metal materials. The conductive member 20 may also be referred to as a bus bar.

[Wavelength and light absorption rate]
Here, the light absorptance of metal materials will be described. Fig. 2 is a graph showing the light absorptance of each metal material with respect to the wavelength of the irradiated laser light. The horizontal axis of the graph in Fig. 2 is the wavelength, and the vertical axis is the absorptance. Fig. 2 shows the relationship between wavelength and absorptance for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

Although the characteristics differ depending on the material, it can be seen that for each metal shown in Figure 2, the energy absorption rate is higher when using blue or green laser light (second laser light) than when using general infrared (IR) laser light (first laser light). This characteristic is particularly noticeable in copper (Cu), gold (Au), etc.

When laser light is irradiated onto a workpiece W that has a relatively low absorption rate for the wavelength used, most of the light energy is reflected and does not affect the workpiece W as heat. Therefore, a relatively high power must be applied to obtain a melted region of sufficient depth. In this case, the sudden input of energy to the center of the beam causes sublimation and the formation of a keyhole.

On the other hand, when laser light is irradiated onto a workpiece W that has a relatively high absorption rate for the wavelength used, most of the input energy is absorbed by the workpiece W and converted into thermal energy. In other words, since there is no need to apply excessive power, it is possible to achieve thermal conduction-type melting that does not involve the formation of a keyhole.

In this embodiment, a keyhole is formed in the workpiece W by the first laser light included in the laser light L, so that a molten pool of the required depth can be formed quickly. In addition, by efficiently heating a wide area of the workpiece W including the molten pool by the second laser light included in the laser light L, it is possible to suppress a sudden temperature change depending on the location of the workpiece W, to further stabilize the molten pool, and to suppress the scattering of spatter from the molten pool to the surroundings. When the laser light L is scanned on the surface of the workpiece W, it is preferable that at least a part of the irradiation area of the second laser light is located forward in the scanning direction relative to the irradiation area of the first laser light. Laser welding by irradiation of the laser light L including the first laser light and the second laser light as in this embodiment is suitable for welding the workpiece W having a conductor part around it, such as welding the conductor 12 of the circuit board 10 and the terminal portion 21 of the conductive member 20.

[spot]
3 is a plan view of a spot S of the laser light L formed on the surface 21b. The laser light L includes a beam Bm1 of the laser light output by the laser device 111 and a beam Bm2 of the laser light output by the laser device 112, and an irradiation area (power area) corresponding to the beams Bm1 and Bm2 is formed on the surface 21b. The irradiation area by the beam Bm2 is wider than the irradiation area by the beam Bm1 and at least partially includes the irradiation area by the beam Bm1. The irradiation area by the beam Bm1 is an example of a first power area, and the irradiation area by the beam Bm2 is an example of a second power area.

The width Wb (maximum width, maximum diameter) of the spot S can be defined as the width of a region having an intensity equal to or greater than 1/ ^e2 of the peak intensity in the spot S. When the spot S is scanned on the surface 21b, the width Wb can be defined as the width in a direction perpendicular to the scanning direction.

[Laser welding method procedure]
4 is a flow chart showing the procedure of the laser welding method. As shown in FIG. 4, first, the circuit board 10 and the conductive member 20 are set in a state in which the conductor 12 and the terminal portion 21 overlap in the Z direction and the terminal portion 21 is in contact with the conductor 12 in the Z direction as shown in FIG. 1 (S1). Next, the surface 21b of the terminal portion 21 is irradiated with laser light L to form a molten pool that penetrates the terminal portion 21 from the surface 21b to the inside of the conductor 12 (S2). Next, the molten pool is solidified by natural cooling or forced cooling (S3). The solidified molten pool becomes a welded portion (welded metal), and the conductor 12 and the terminal portion 21 are joined by the welded portion, thereby electrically connecting the conductor 12 and the terminal portion 21. The conductor 12, the conductive member 20, and the welded portion constitute a part of an electrical circuit. The Z direction is an example of a first direction.

[Depth of molten pool]
Fig. 5 is a cross-sectional view of the molten pool M formed in S2. As shown in Fig. 5, the molten pool M penetrates the terminal portion 21 from the surface 21b and reaches the inside of the conductor 12. Here, in this embodiment, the conditions of the laser welding are set in S2 so that the tip end of the molten pool M, i.e., the end Ma on the opposite side in the Z direction, does not reach the insulator 11, and the portion of the conductor 12 between the end Ma and the insulator 11 becomes a non-melted portion 12b.

Here, if the depth of the molten pool M in the Z direction is Dp, the thickness of the terminal portion 21 in the Z direction is T1, the thickness of the conductor 12 in the Z direction is T2, and the thickness of the non-molten portion 12b in the Z direction is T3, the following equation (1-0) holds.
Dp=T1+T2-T3 (1-0)
As a result of the inventors' intensive research, it was found that in S12, the temperature of the point P of the insulator 11 closest to the end Ma becomes the highest, and the temperature becomes higher as the thickness T3 of the non-melted portion 12b becomes thinner (smaller). Therefore, if the thickness T3 of the non-melted portion 12b is made thick so that the heat conducted from the molten pool M to the point P of the insulator 11 does not cause a change in characteristics, the heat-induced change in characteristics will not occur in almost the entire insulator 11. Since the temperature of the boundary portion of the molten pool M with the conductor 12 is the melting point of the conductor 12, the relationship between the thickness of the non-melted portion 12b and the temperature of the point P can be obtained by simulation or experiment. That is, it is sufficient to obtain the maximum value Tmax of the thickness of the non-melted portion 12b at which the characteristics change occurs at the point P due to the heat conducted from the molten pool M to the point P of the insulator 11 through the non-melted portion 12b by simulation or experiment, and then form the molten pool M with a depth Dp that satisfies the following formula (1-1).
Dp<T1+T2-Tmax ... (1-1)
When the insulator 11 is a ceramic such as silicon nitride, the maximum value Tmax may be a thickness at which the maximum temperature in the insulator 11 at S2, i.e., the temperature at point P, is the thermal shock temperature (e.g., about 800°C). When the insulator 11 includes a synthetic resin material such as glass epoxy resin, the maximum value Tmax may be a thickness at which the maximum temperature in the insulator 11 at S2, i.e., the temperature at point P, is the heat resistance temperature (e.g., about 240°C). Through intensive research by the inventors, it has been found that the maximum value Tmax that satisfies such conditions is 20 μm. In this case, formula (1-1) becomes the following formula (1-2).
Dp<T1+T2-20 ... (1-2)

Furthermore, the depth Dp is premised on the fact that a required joint strength can be obtained. In other words, if the minimum depth of the molten pool M at which the required joint strength between the conductor 12 and the terminal portion 21 by the welded portion 30 solidified from the molten pool M is defined as Dmin, then it is sufficient to form the molten pool M with a depth Dp that satisfies the following formula (2-1).
Dp>Dmin ... (2-1)
Through extensive research by the inventors, it has been found that the minimum value Dmin that satisfies these conditions is typically 50 μm. In this case, formula (2-1) becomes the following formula (2-2).
Dp>50 ... (2-2)

[Irradiation energy]
The greater the irradiation energy of the laser beam, the deeper the depth Dp of the molten pool M. Fig. 6 is a graph showing an experimentally determined relationship between irradiation energy E and depth Dp. Through intensive research by the inventors, it was found that there is a linear relationship between the irradiation energy E and depth Dp as shown in Fig. 6, and one can be approximately expressed as a linear function of the other. In the case of Fig. 6,
Dp = C2 × E - C1 ... (3-0)
(where C1 and C2 are coefficients) By modifying equation (3-0), the irradiation energy E can be expressed by the following equation (3-1).
E = (Dp + C1) / C2 ... (3-1)
Through extensive research by the inventors, it was found that when the width Wb of the spot S on the surface 21b is 100 [μm], the irradiation energy E [J] can be expressed by the following formula (3-2) according to the depth Dp [μm].
E = (Dp + 21) / 135 ... (3-2)
In this case, C1 = 21 and C2 = 135. By using the formulas (3-1) and (3-2), the irradiation energy E for obtaining the required depth Dp can be determined in S2.

[Scanning speed]
When the spot S of the laser light L is scanned on the surface 21b, if the scanning speed is too slow, the irradiation energy of the laser light L becomes excessive, the molten pool M becomes deep, and a change in characteristics occurs at the point P of the insulator 11. Conversely, if the scanning speed is too fast, the irradiation energy of the laser light L becomes insufficient, the molten pool M becomes shallow, and the required joint strength of the welded portion 30 cannot be obtained. From this viewpoint, the inventors have conducted extensive research and found that, under typical irradiation conditions of the laser light L that satisfy the formulas (3-1) and (3-2), the scanning speed is preferably 100 [mm/s] or more and 800 [mm/s] or less, and more preferably 300 [mm/s] or more and 600 [mm/s] or less.

As described above, according to this embodiment, when the conductor 12 and the terminal portion 21 are joined by laser welding, it is possible to obtain a new and improved laser welding method and laser welding apparatus 100 that can suppress the thermal effects on the portion in contact with the conductor 12, such as the insulator 11.

[Second embodiment]
FIG. 7 is a schematic diagram of the laser welding apparatus 100B (100) of the second embodiment. As shown in FIG. 7, the laser welding apparatus 100B does not include optical components such as the laser device 112 and the collimator lens 121-2 and the filter 124 for transmitting the laser light (second laser light) outputted by the laser device 112, which were included in the laser welding apparatus 100A of the first embodiment. In addition, in this embodiment, the optical head 120B (120) has a diffractive optical element 125 (hereinafter referred to as DOE 125) between the collimator lens 121 and the mirror 123. Except for these points, the laser welding apparatus 100B has the same configuration as the laser welding apparatus 100A of the first embodiment.

The DOE 125 shapes the shape of the laser light beam (hereinafter referred to as the beam shape). FIG. 8 is an explanatory diagram showing the concept of the principle of the DOE 125. As shown in FIG. 8, the DOE 125 has a configuration in which, for example, multiple diffraction gratings 125a with different periods are superimposed. The DOE 125 can shape the beam shape by bending the parallel light in a direction influenced by each diffraction grating 125a or by superimposing the light. The DOE 125 can also be called a beam shaper.

9 is an exemplary and schematic plan view of a spot S of the laser light L formed on the surface 21b of the workpiece W. As shown in FIG. 9, the laser light L can form an irradiation area of multiple beams Bm on the surface 21b by the action of the DOE 125. In the example of FIG. 9, the multiple beams Bm form a power area formed by at least one beam Bm1 (Bm) in the center on the surface 21b and a substantially annular power area formed by multiple beams Bm2 (Bm) surrounding the central area (16 beams in the example of FIG. 9). By appropriately designing the DOE 125, various power areas with different specifications such as the number of beams, beam arrangement, shape, size, and power density can be formed on the surface 21b, not limited to the example of FIG. 9. In addition, in a configuration having the DOE 125, it is easier to form a wider spot S on the surface 21b than in a configuration without the DOE 125, and it is easier to heat a wider area of the peripheral part of the molten pool. Therefore, this embodiment also suppresses sudden temperature changes depending on the location of the workpiece W, stabilizes the molten pool, and suppresses spattering from the molten pool to the surrounding area. The width Wb of the spot S can be defined as the distance between the most distant outer edges of the beams Bm that are most distant from each other. In this case, too, when the spot S scans the surface 21b, the width Wb can be defined as the width in a direction perpendicular to the scanning direction.

Although the above is an example of an embodiment of the present invention, the above embodiment is merely an example and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of each configuration, shape, etc. (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be modified as appropriate.

For example, as long as irradiation that satisfies the above-mentioned conditions can be performed, the laser light does not need to include the first laser light and the second laser light, and does not need to be beam mode controlled by the DOE.

1... Circuit board assembly 10... Circuit board 11... Insulator (first part)
11a... surface 11b... surface 12... conductor 12a... surface 12b... non-melted portion 20... conductive member 21... terminal portion 21a... surface 21b... surface (first surface)
30...welded portion 100, 100A, 100B...laser welding device 111, 112...laser device 120, 120A, 120B...optical head 121, 121-1, 121-2...collimator lens 122...condenser lens 123...mirror 124...filter 125...DOE (diffractive optical element)
125a...diffraction grating 126...galvanometer scanner (scanning mechanism)
126a, 126b...mirror 130...optical fiber 140...position adjustment mechanism (scanning mechanism)
Bm, Bm1, Bm2...Beams C1, C2...Coefficient Dmin...Minimum value Dp...Depth E...Irradiation energy L...Laser light M...Molten pool Ma...End (tip)
P... point S... spot S1 to S3... process T1, T2, T3... thickness Tmax... maximum value W... processing object Wb... width X... direction Y... direction Z... direction (first direction)

Claims (20)

A laser welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the method comprising:
placing the terminal portion on the conductor in a state of contact with the conductor in the first direction;
irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool extending from the first surface through the terminal portion into the conductor;
cooling the molten pool to solidify and form a weld;
Equipped with
In the step of forming the molten pool,
A non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction,
The depth Dp of the molten pool along the first direction is expressed by the following formula (1-1):
Dp<T1+T2-Tmax ... (1-1)
(wherein T1 is the thickness of the terminal portion along the first direction, T2 is the thickness of the conductor along the first direction, and Tmax is the maximum thickness of the non-melted portion at which a characteristic change in the first portion occurs due to heat conducted from the molten pool to the first portion via the non-melted portion), In the step of forming the molten pool, the Dp is expressed by the following formula (2-1):
Dp>Dmin ... (2-1)
2. The laser welding method according to claim 1, wherein the laser light is irradiated onto the first surface under conditions satisfying the following: (wherein Dmin is the minimum value of the depth at which a required joining strength between the conductor and the terminal portion is obtained by the welded portion). The laser welding method according to claim 1 or 2, wherein Tmax is 20 μm. The laser welding method according to claim 2, wherein the Dmin is 50 [μm]. The laser welding method according to claim 1 or 2, wherein the conductor is made of a copper-based material. the first portion is made of ceramic;
3. The laser welding method according to claim 1, wherein the Tmax is a thickness at which the maximum temperature of the first portion in the step of forming the molten pool becomes a thermal shock resistance temperature of ceramic. The laser welding method according to claim 6, wherein the circuit board is a silicon nitride board. the first portion includes a synthetic resin material;
3. The laser welding method according to claim 1, wherein the Tmax is a thickness at which a maximum temperature of the first portion in the step of forming the molten pool becomes a heat-resistant temperature of a synthetic resin material. The laser welding method according to claim 8, wherein the circuit board is a glass epoxy resin board. In the step of forming the molten pool, the irradiation energy E of the laser beam on the first surface is expressed by the following formula (3-1):
E = (Dp + C1) / C2 ... (3-1)
3. The laser welding method according to claim 1, wherein the first surface is irradiated with the laser light under a condition satisfying: (where C1 and C2 are coefficients). The laser welding method according to claim 10, wherein, when the width of the spot of the laser light formed on the first surface is 100 [μm], the irradiation energy is E [J], and the depth is Dp [μm], C1 is 21 and C2 is 135. The laser light is scanned on the first surface,
3. The laser welding method according to claim 1, wherein a scanning speed of the laser light on the first surface is 100 mm/s or more and 800 mm/s or less. The laser welding method according to claim 12, wherein the scanning speed is 300 mm/s or more and 600 mm/s or less. The laser welding method according to claim 1 or 2, wherein the laser light includes a first laser light having a wavelength of 800 nm or more and a second laser light having a wavelength of 550 nm or less. The laser welding method according to claim 14, wherein the wavelength of the laser light is 400 nm or more. A laser welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the method comprising:
placing the terminal portion on the conductor in a state of contact with the conductor in the first direction;
irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool extending from the first surface through the terminal portion into the conductor;
cooling the molten pool to solidify and form a weld;
Equipped with
In the step of forming the molten pool,
A non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction,
The depth Dp of the molten pool along the first direction is expressed by the following formula (1-2).
Dp<T1+T2-20 ... (1-2)
(wherein T1 is a thickness of the terminal portion along the first direction, and T2 is a thickness of the conductor along the first direction), In the step of forming the molten pool, the Dp is expressed by the following formula (2-2):
Dp>50 ... (2-2)
The laser welding method according to claim 16 , wherein the first surface is irradiated with the laser light under a condition that satisfies the following: The laser welding method according to claim 16 or 17, wherein the laser light includes a first laser light having a wavelength of 800 nm or more and a second laser light having a wavelength of 550 nm or less. The laser welding method according to claim 18, wherein the wavelength of the laser light is 400 nm or more. A laser welding method for welding a conductor of a circuit board having a first portion and a conductor overlapping the first portion in a first direction to a terminal portion of a conductive member, the method comprising:
placing the terminal portion on the conductor in a state of contact with the conductor in the first direction;
irradiating a first surface of the terminal portion facing the first direction on an opposite side to the conductor with a laser beam to form a molten pool extending from the first surface through the terminal portion into the conductor;
cooling the molten pool to solidify and form a weld;
Equipped with
In the step of forming the molten pool,
A non-melted portion of the conductor is interposed between the first portion and a tip end of the molten pool in a direction opposite to the first direction,
The depth Dp of the molten pool along the first direction is expressed by the following formula (1-1):
Dp<T1+T2-Tmax ... (1-1)
(where T1 is a thickness of the terminal portion along the first direction, T2 is a thickness of the conductor along the first direction, and Tmax is a maximum value of a thickness of the non-melted portion at which a characteristic change in the first portion occurs due to heat conducted from the molten pool to the first portion via the non-melted portion),
A laser device that outputs the laser light;
an optical head that irradiates the first surface with a laser beam output from the laser device;
A laser welding device comprising:

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