KR20210106566A - Methods and systems for welding copper and other metals using blue lasers - Google Patents

Abstract

A visible light laser system and operation for welding materials together is described. Blue laser systems form essentially perfect welds on copper-based materials. A blue laser system and operation for welding conductive elements, particularly thin conductive elements, together for use in energy storage devices such as battery packs are described.

Description

Methods and systems for welding copper and other metals using blue lasers

This application claims the benefit of filing date of U.S. Provisional Application Serial No. 62/786,511, filed December 30, 2018, under 35 USC §119(e), the entire disclosure of which is incorporated herein by reference. .

The present invention relates to laser processing of materials, particularly laser bonding of copper materials using a laser beam having a wavelength of from about 350 nm to about 500 nm or greater.

Laser welding of copper has proven very difficult due to its high reflectivity, high thermal conductivity and high heat capacity. Numerous methods of welding copper have been developed, from ultrasonic welding to IR laser welding. However, these conventional copper welding methods have many disadvantages and limitations. One market where these limitations are seen, for example, is the high-performance electronics sector for the growing e-vehicle market. The production of high-performance batteries and electronics for the growing automotive market requires better weld quality at a faster rate than can be achieved by these prior art technologies.

When using an IR laser source at 1030 nm, the high reflectivity of copper at these wavelengths makes it difficult to heat and weld by coupling power to the material. One way to overcome the high reflectivity is to use a high-power level (> 1 kW) IR laser to initiate keyhole welding and then couple the power source to the material. First of all, the problem with this welding method is that the vapors in the keyhole can lead to micro-explosions where molten copper can be sprayed all over the part to be welded, or the micro-explosion can cause the hole to completely penetrate the part to be welded. As a result, the researchers had to rely on rapidly modulating the laser power to prevent these defects during welding. It was discovered that the defect was a direct result of the process itself, as when a laser attempted to weld copper, the laser first heats the copper to its melting point and then rapidly evaporates the copper. If the copper vaporizes to form keyholes and the laser coupling rises rapidly from the initial 5% to 100%, this transition occurs so rapidly that the amount of combined heat quickly exceeds the amount of heat required to weld the part, resulting in the described micro-explosion. causes

Laser welding of copper using current infrared laser methods and systems is challenging and problematic due to its high reflectivity, high thermal conductivity, low vaporization point and high heat capacity. Numerous methods have been tried for welding copper with an IR laser, ranging from combining an IR laser with a green laser, oscillating a spot in a weld puddle, operating in a vacuum, and modulating the laser at high frequencies. . Although these approaches are currently used in some copper welding applications, they tend to have narrow processing windows, uncontrolled spatter, and unpredictable variability in the weld and have generally proven undesirable or suboptimal. One of the more difficult copper welding processes is how to weld copper foil stacks to each other and to thicker bus bars. Today, this cannot be done using an IR laser or in a way that produces the weld quality required by manufacturers. Therefore, manufacturers have relied on ultrasonic welding methods to bond these foils together. These ultrasound methods are also not optimal and are problematic. For example, with ultrasonic welding methods, sonotrodes can wear out during production, resulting in process variations ranging from incomplete welds to residual welds. These defects limit the manufacturing yield, the internal resistance of the battery, the resulting energy density of the battery, and in many cases the reliability of the battery.

The term "copper-based material", unless expressly provided otherwise, is to be given in the broadest possible sense and contains copper, copper material, copper metal, material electroplated with copper, at least about 10% to 100% copper by weight. metal materials containing, metals and alloys containing at least about 10% to 100% copper by weight, metals and alloys containing at least about 20% to 100% copper by weight, metals and alloys containing at least about 10% to 100% copper by weight, metals and alloys containing at least about 50% to 100% copper by weight, metals and alloys containing at least about 70% to 100% copper by weight, and at least about 90% to 100% copper by weight. It may include metals and alloys containing

The terms "laser processing", "laser processing of materials" and similar terms, unless expressly provided otherwise, are to be given the broadest possible meaning and are to be welded, brazed, smelted, joined, annealed, softened, tackified, surface may include reprocessing, peening, heat treatment, fusing, sealing and stacking.

As used herein, unless explicitly stated otherwise, the terms "UV", "ultraviolet light", "UV spectrum", and "UV portion of the spectrum" and similar terms are to be given their broadest meaning and are to be about It may include light of a wavelength between 10 nm and about 400 nm, and between 10 nm and 400 nm.

As used herein, unless expressly stated otherwise, the terms "visible light," "visible spectrum," and "visible portion of the visible spectrum," and similar terms, are to be given their broadest meaning and are from about 380 nm to about 380 nm. 750 nm, and light having a wavelength between 400 nm and 700 nm.

As used herein, unless expressly stated otherwise, the terms "blue laser beam", "blue laser" and "blue" are to be given their broadest meaning and are generally to a laser beam, or about 400 Refers to a system that provides, for example, a propagating laser beam, laser beams, a laser source, such as a laser and a diode laser, that provides light having a wavelength of between about 500 nm and about 500 nm. A typical blue laser has a wavelength in the range of about 405 to 495 nm. Blue lasers include wavelengths of 450 nm, about 450 nm, 460 nm, and about 470 nm. The blue laser may have a bandwidth of from about 10 pm (picometer) to about 10 nm, about 5 nm, about 10 nm, and about 20 nm, as well as larger or smaller bandwidths.

As used herein, unless expressly stated otherwise, the terms "green laser beam", "green laser" and "green" are to be given their broadest meaning, generally a laser beam, or about 500 nm to a system that provides light having a wavelength of from to about 575 nm, eg, a propagating laser beam, laser beams, a laser source, eg a laser and a diode laser. Green lasers include wavelengths of 515 nm, about 515 nm, 532 nm, about 532 nm, 550 nm, and about 550 nm. The green laser may have a bandwidth of about 10 pm to 10 nm, about 5 nm, about 10 nm, and about 20 nm, as well as larger or smaller bandwidths.

As used herein, unless explicitly stated otherwise, terms such as "at least", "greater than" mean "not less than". That is, such terms exclude lower values unless otherwise specified.

As used herein, unless explicitly stated otherwise, ambient temperature is 25°C, and standard temperature and pressure are 25°C and 1 atmosphere. Unless expressly stated otherwise, all tests, test results, physical properties and temperature dependent, pressure dependent or temperature dependent and pressure dependent values are given at standard temperature and pressure.

In general, as used herein, unless expressly stated otherwise, the term "about" and the symbol "~" mean a deviation or range of ±10%, experimental or instrumental error associated with obtaining the specified value, preferably It is meant to include the larger of these.

As used herein, unless expressly stated otherwise, recitation of ranges of values, ranges from about “x” to about “y,” and similar terms and quantifications refer to individual values within the range individually. It is used as a simple abbreviation method referred to as . Accordingly, each item, function, value, quantity or quantity falling within its scope is included. As used herein, unless otherwise specified, each and every individual point within a range is included herein and is a part of this specification as if they were individually recited herein.

The Background section of the present invention is intended to introduce various aspects of the technology that may be associated with embodiments of the present invention. Accordingly, the foregoing discussion in this section provides a basis for a better understanding of the present invention and should not be regarded as an admission of prior art.

In metal welding, especially copper metal welding for electronic components and batteries, the demand for better weld quality, faster welding speed, as well as greater reproducibility, reliability, higher tolerances and greater robustness continues to increase. Included in these needs is a need for improved welding methods for copper itself and other metals; There is a need to solve stacks of copper foils and the problems associated with welding these stacks to thicker copper or aluminum components. The present invention addresses these needs by providing, among other things, the improvements, articles of manufacture, apparatus and processes taught and disclosed herein.

A system and method for laser welding a plurality of copper foils together is provided, the method comprising: placing a plurality of pieces of copper foil on a welding stand, the foil containing at least about 50% copper; applying a clamping force to the plurality of pieces of copper foil to clamp the pieces of foil together at a welding stand; Directing a blue laser beam along a laser beam path at a plurality of pieces of copper foil, the laser beam having the following characteristics: i. an output of at least 500 watts, ii. Beam parameter product of about 44 mm mrad or less, iii. A spot size of about 400 μm or less, iv. an average strength of at least about 400 kW/cm ^{2 , v.} having a peak intensity of at least about 800 kW/cm ^{2 ;} lap welding a plurality of copper foil pieces together at a welding speed; and injecting a non-oxidizing beam cleaning gas in a space along a laser beam path through which the laser beam travels in free space from the optical element to the plurality of copper foil pieces. providing a cleaning gas that removes plume material from the laser beam path and prevents oxidation of the plurality of pieces of copper foil; The welding speed, clamping force, and flow rate of the non-oxidizing cleaning gas are predetermined to provide a needle-needle weld with no visible splatter and no visible porosity.

Also provided are these welding, laser systems and welding methods having one or more of the following features, wherein the beam is a CW beam, the beam is a pulsed beam, the beam has a wavelength of about 450 nm, and the optical element comprises: wherein the cleaning gas is selected from the group consisting of argon, argon-CO ² , air, helium and nitrogen, and the laser beam is not fluctuated so that it fluctuates and wherein the plurality of pieces of copper foil has 10 to 50 pieces of foil, wherein the pieces of copper foil have a thickness of between about 80 μm and 500 μm, and wherein each of the plurality of pieces of copper foil has between about 80 μm and 500 μm. It has a thickness of μm, and the welding speed is at least 10 m/min.

Also provided are systems and methods for laser welding a plurality of metal pieces together, the method comprising: placing the plurality of metal pieces on a welding stand; applying a clamping force to the plurality of metal pieces to clamp the metal pieces together at a welding stand; Directing a blue laser beam along a laser beam path at a plurality of pieces of metal, the laser beam having the following characteristics: i. an output of at least 500 watts, ii. Beam parameter product of about 44 mm mrad or less, iii. A spot size of about 400 μm or less, iv. an average strength of at least about 400 kW/cm ^{2 , v.} having a peak intensity of at least about 800 kW/cm ^{2 ;} blue laser beam welding a plurality of metal pieces together at a welding speed; and providing a non-oxidizing beam cleaning gas in a space along a laser beam path through which the laser beam travels from the optical element to the plurality of copper foil pieces in free space. comprising: the cleaning gas removing plume material from the laser beam path and preventing oxidation of the plurality of pieces of copper foil; The welding speed, clamping force and flow rate of the non-oxidizing cleaning gas are predetermined to provide a weld free of visible splatter and visible porosity.

Still further, provided are these welding, laser systems and welding methods having one or more of the following features, wherein the welding stand has an air gap under the piece of metal, and wherein the metal is aluminum, stainless steel, copper, an aluminum-based metal. , is selected from the group consisting of stainless steel-based metals, copper-based metals, aluminum alloys, stainless steel alloys and copper alloys, the wavelength of the laser beam is about 450 nm, and the laser beam is not fluctuated to provide a fluctuation-free laser welding process, The weld is selected from the weld group consisting of lap weld, butt weld, bead on plate weld, and conduction mode weld.

A system and method are provided for laser welding a plurality of copper foils together, the method comprising: placing a plurality of pieces of copper foil on a welding stand, wherein the copper foil contains at least about 50% copper and wherein the copper foil contains about 50% copper; having a thickness of 80 μm to 500 μm; applying a clamping force to the plurality of pieces of copper foil to clamp the pieces of foil together at a welding stand; Directing a blue laser beam along a laser beam path at a plurality of pieces of copper foil, the laser beam having the following characteristics: i. an output of at least 600 watts, ii. Beam parameter product of about 44 mm mrad or less, iii. a spot size of about 200 μm to about 400 μm, iv. an average strength of at least about 2.1 MW/cm ^{2 , v.} having a peak intensity of at least about 4.5 MW/cm ^{2 ;} blue laser beam welding a plurality of metal pieces together at a welding speed of at least 10 m/min; providing a beam cleaning gas, the cleaning gas removing plume material from the laser beam path and preventing oxidation of the plurality of pieces of copper foil; The welding speed, clamping force and flow rate of the non-oxidizing cleaning gas are predetermined to provide a weld free of visible splatter and visible porosity.

A method of forming a perfect weld in a copper-based material is provided, the method comprising: placing a workpiece in a laser system, the workpiece placing a first piece of copper-based material in contact with a second piece of copper material; comprising a step; and directing a blue laser beam at the workpiece to form a weld between the first piece of copper-based material and the second piece of copper-based material; The weld includes a HAZ and a re-solidification zone; The microstructure, HAZ and re-solidification region of the copper-based material are identical.

Further provided are these welds, systems, and methods having one or more of the following systems, wherein the same microstructure does not exhibit discernible differences in the weld indicative of weakness in the weld; Identical microstructures contain similarly sized crystal growth regions; Welds are formed by conduction mode welding; Welds are formed by keyhole mode welding; the thickness of the first and second pieces is between about 10 μm and about 500 μm; the first piece comprises a plurality of layers of copper foil; The first piece is copper metal; the first piece is a copper alloy having from about 10 to about 95 weight percent copper; The laser beam is directed to the workpiece as a focused spot with a power density of ^{less than 800 kW/cm 2 ;} The laser beam is directed to the workpiece as a focused spot having a power density of less than ^{500 kW/cm 2 ;} The laser beam is directed to the workpiece as a focused spot having a power density of about 100 kW/cm ² to about 800 kW/cm ^{2 ;} The laser beam is directed to the workpiece as a focused spot ^{with a power density greater than 100 kW/cm 2 ;} The laser beam has a power of less than 500 W; The laser beam has a power of less than 275 W; The laser beam has a power of less than 150 W; The laser beam has a power ranging from 150 W to about 750 W; The laser beam has a power ranging from about 200 W to about 500 W; The laser beam is directed to the workpiece as a focused spot having a spot size of about 50 μm to about 250 μm; the laser beam has a wavelength between about 405 nm and about 500 nm; The weld being formed is splatter free; The laser does not vaporize the workpiece.

Still further provided is a method of forming a perfect weld in a copper-based material, the method comprising placing a workpiece in a laser system, the workpiece contacting a first piece of copper-based material with a second piece of copper material Including arranging the step; and directing the blue laser beam to the workpiece to form a weld between the first piece of copper-based material and the second piece of copper-based material, wherein the weld includes a HAZ and a re-solidification region, the hardness range for the HAZ is within the hardness range for the copper-based material.

Still further, provided are these welding, systems and methods having one or more of the following characteristics: wherein the hardness range for the re-solidification region is within the hardness range for the copper-based material; The microstructure, HAZ and resolidification zone of the copper-based material are the same; The same microstructure shows no discernible difference in the weld indicative of weakness in the weld; The same microstructure shows no discernible difference in the weld indicative of weakness in the weld; The same microstructure contains similarly sized crystal growth regions.

Also provided is a method of forming a perfect weld in a copper-based material, the method comprising placing a workpiece in a laser system, the workpiece bringing a first piece of copper-based material into contact with a second piece of copper material. comprising disposing; and directing the blue laser beam to the workpiece to form a weld between the first piece of copper-based material and the second piece of copper-based material, the weld comprising a HAZ and a re-solidified region, the weld comprising a HAZ and a re-solidified region for the re-solidified region. The hardness range includes steps, which are within the hardness range for copper-based materials.

In addition, copper is welded with a blue laser having a wavelength range of 405 nm to 500 nm, and welds and articles produced by such welding are provided.

Moreover, provided are these welding, methods, and systems comprising one or more of the following features: welding copper in a conduction mode; welding copper in conduction mode without vaporization of the weld puddle during the welding process; welding copper in a conduction mode that produces a base metal-like microstructure with crystal growth regions that are similar in size to the base material; welding copper in a conduction mode that creates a microstructure similar to the base material in a heat affected zone (HAZ); welding the copper in a conduction mode that creates a microstructure similar to the base material of the weld bead; welding the copper in a conduction mode that produces a hardness similar to the base material in the heat affected zone; welding the copper in a conduction mode that produces a hardness similar to the base material of the weld bead; welding copper whose microstructure is different from that of the base material; and welding copper in which the microstructure of the HAZ is similar to the base material.

Moreover, provided are these welding, methods, and systems comprising one or more of the following features: welding copper in a keyhole mode; welding copper in a keyhole mode in which very low spatter occurs during welding and little or no spatter is observed on the copper surface after welding; welding copper having a power density of at least 500 kW/cm ² and a welding speed at which the keyhole can remain open; welding copper having a power density of at least 400 kW/cm ² and a welding speed at which the keyhole can remain open; welding copper having a power density of at least 100 kW/cm ² and having a welding speed fast enough to prevent conversion to a keyhole welding method; welding copper with preheat to improve penetration depth during welding; Welding copper with Ar-CO _{2 auxiliary gas;} welding copper with Ar-H _{2 auxiliary gas;} welding copper with Ar assist gas; welding copper with air; welding copper with He assist gas; and welding the copper with _{N 2 auxiliary gas;} and welding the copper with an auxiliary gas.

Furthermore, provided are these welding, methods, and systems comprising one or more of the following features: wherein the laser power is modulated from 1 Hz to 1 kHz; The laser power is modulated from 1 kHz to 50 kHz; uses a long blue laser spot to keep the keyhole open; moving the spot rapidly in a circular, oscillating or rectangular oscillating motion; It uses a mirror mounted on a galvanometer to vibrate the spot parallel to the welding direction; It uses a mirror mounted on a galvanometer to vibrate the spot perpendicular to the welding direction; It uses a pair of mirrors mounted on a pair of galvanometers to quickly move the spot in a circular, vibrating or rectangular vibrating motion.

Also provided is a method of forming a keyhole weld in a copper-based material, the method comprising: placing a workpiece in a laser system, the workpiece to contact a first piece of copper-based material with a second piece of copper material; comprising disposing; and directing a blue laser beam at the workpiece to form a keyhole mode weld between the first piece of copper-based material and the second piece of copper-based material, the weld comprising a HAZ and a resolidification zone. do.

Moreover, provided are these welding, methods, and systems comprising one or more of the following features: wherein the laser power is less than 1000 kW for keyhole welding; The laser power is less than 500 kW for keyhole welding; The laser power is less than 300 kW for keyhole welding; extending the laser beam to suppress spatter from the keyhole; modulating the laser output to suppress spatter from the keyhole; rapidly scanning the beam to suppress spatter during keyhole mode of welding; sharply reducing the laser power after welding is initiated automatically or manually; using low atmospheric pressure to reduce entrapped gases and spatter during the welding process; applying a shielding gas; applying a shielding gas selected from the group consisting of He, Ar, N _{2 ;} applying a shielding gas mixture selected from the group consisting of Ar-H ₂ , N ₂ , N ₂ -H _{2 ;} and applying a shielding gas and adding hydrogen to the shielding gas to remove the oxide layer and promote wetting of the weld.

1 is a photograph of an embodiment of a spatter-free conduction mode welding of copper in accordance with the present invention.
2 is a photograph of an embodiment of a keyhole weld on copper in accordance with the present invention.
3 is a chart showing penetration depth versus velocity for an embodiment of the present invention for 127 μm thick copper, with copper fully penetrated up to a velocity of 8 m/min.
FIG. 4 is a chart showing penetration depth versus velocity for an embodiment of the present invention for 254 μm thick copper, with copper fully penetrated to a velocity of 0.5 to 0.75 m/min.
5 is a chart showing penetration depth versus velocity for an embodiment of the present invention.
6 is a chart showing the depth of penetration at various different velocities for an embodiment of the present invention.
7 is an annotated photograph showing an embodiment of conduction mode welding to a 70 μm thick copper foil according to the present invention.
8 is an annotated photograph of an embodiment of a keyhole mode weld section in accordance with the present invention.
9 is absorption curves for various metals and shows the difference in absorption between IR lasers and visible lasers.
10 is a schematic diagram of an embodiment of conduction mode weld propagation with a material according to the present invention;
11 is a schematic diagram of an embodiment of a keyhole weld propagation with a material according to the present invention;
12 is a perspective view showing an embodiment of a component holder for laser welding according to the present invention.
Fig. 12a is a cross-sectional view of the part holder of Fig. 12;
13 is a perspective view of an embodiment of a part holder for holding thin parts for making lap welds in accordance with the present invention;
Fig. 13a is a cross-sectional view of the component holder of Fig. 13;
14 is a photograph of an embodiment of a bead on a plate for conduction mode welding in accordance with the present invention.
15 is a photograph of an embodiment of a foil stack welded in conduction welding mode in accordance with the present invention.
16 is a photograph of an embodiment of a bead-on-plate for keyhole mode welding according to the present invention.
17 is a photograph of an embodiment of a stack of 40 copper foils welded in keyhole mode in accordance with the present invention.
18 is a graph of depth of penetration of copper for various power levels and various speed embodiments in accordance with the present invention.
19 is a schematic diagram of an embodiment of a 150 watt blue laser system for use in performing an embodiment of the present laser welding method in accordance with the present invention.
20 is a schematic ray tracing diagram of an embodiment using two 150 watt blue laser systems to make a 300 watt blue laser system in accordance with the present invention.
21 is a schematic ray tracing diagram of an embodiment using four 150 watt blue laser systems to make an 800 watt blue laser system in accordance with the present invention.
22 is an embodiment of displacement from focus (μm) versus beam pseudoradius (microns (μm)) using a 100 mm focal length lens at 600 watts for a circular aperture containing 95% of the enveloping power according to the present invention. It is a graph.
23 is a graph of an embodiment of a copper 110 bead on plate (BOP) test showing penetration (μm) versus velocity (m/min) in accordance with the present invention.
24 is a graph of an embodiment of a copper 110 butt weld test showing penetration (μm) versus velocity (m/min) in accordance with the present invention.
25 is a graph of an embodiment of conduction mode welding showing the effect of plate thickness on depth of penetration in accordance with the present invention.
26 is a graph of an embodiment of an aluminum 1100 BOP test showing penetration (μm) versus velocity (m/min) in accordance with the present invention.
27 is a graph of an embodiment of an aluminum 110 butt weld test showing penetration (μm) versus velocity (m/min) in accordance with the present invention.
28 is a graph of an embodiment of a stainless steel 304 BOP test showing penetration (μm) versus velocity (m/min) in accordance with the present invention.
29 is a photograph of an embodiment of a longitudinal cross-section of an embodiment of a keyhole welded copper 110 plate showing the beginning of a full penetration region.
30 is a photograph of an embodiment of 1.016 mm thick copper welded at 1.1 m/min with minimal porosity and spatter in accordance with the present invention.
31 is a graph showing penetration depth (μm) versus velocity (m/min) of an embodiment of a BOP test for copper 110 welded to 600 watts and 200 μm spot size in accordance with the present invention.
32 is a photograph of an embodiment of keyhole lap welding of four stainless steel 304 sheets in accordance with the present invention.
33 is a graph of an embodiment of a lap weld test on a stack of copper 110 foils in accordance with the present invention.
34 is a photograph of an embodiment of a 40, 10 mm thick copper 110 foil stack welded with a 500 watt, 400 μm spot blue laser in accordance with the present invention.

In general, the present invention relates to lasers, laser beams, systems and methods for welding metals, particularly aluminum, stainless steel, copper, aluminum-based metals, stainless steel-based metals, copper-based metals and alloys thereof. In general, the present invention also relates to a method of applying a laser beam, a beam size, a beam power, a method of holding a component and a method of introducing a shielding gas to aid in the welding process, preventing oxidation of the component and preventing plume interference with the laser beam This includes managing the plume to

In embodiments, the present invention provides high quality welding, high welding speed, and both to copper-based materials in many areas including electronic components and further including batteries. In embodiments, the present invention provides high quality welding, high welding speed, and both to copper-based materials for automotive parts, including automotive electronic components, including batteries.

In embodiments, the present invention provides high quality welding, high welding speed, and both to stainless steel based materials in many areas including electronic components and further including batteries. In an embodiment, the present invention provides high quality welding, high welding speed, and both to stainless steel based materials for automotive parts including automotive electronic components including batteries.

In embodiments, the present invention provides high quality welding, high welding speed, and both, to aluminum-based materials in many areas including electronic components and further including batteries. In embodiments, the present invention provides high quality welding, high welding speed, and both to aluminum-based materials for automotive parts, including automotive electronic parts, including batteries.

In an embodiment of the present invention, a high power blue laser source (eg, ˜450 nm) solves the problems of conventional copper welding techniques. The blue laser source provides a blue laser beam, and the absorption of copper at these wavelengths is ~65%, allowing efficient coupling of laser power to materials at all power levels. These systems and methods provide reliable welding in many welding techniques, including conduction and keyhole welding modes. Such systems and methods minimize, reduce, and preferably eliminate vaporization, spatter, microblast, and combinations and deformations thereof.

Blue laser welding of copper at power levels ranging from 150 watts to 275 watts with a spot size of ˜200 μm in an embodiment achieves stable and low spatter welding over all power ranges. In this embodiment of the welding system and method, the weld is in a conduction mode with the resulting weld microstructure similar to the base material.

Preferably, in an embodiment the laser wavelength may be at a wavelength of 350 nm to 500 nm, and the spot size (diameter or cross-section) may range from 100 microns (μm) to 3 mm, larger spot sizes are also contemplated. . The spots may be circular, oval, linear, square or other pattern. Preferably, the laser beam is continuous. In embodiments, the laser beam may be pulsed at, for example, about 1 microsecond or longer.

Referring to FIG. 6 , penetration depth versus power is plotted at various welding speeds. Welding was performed using a system of the type described in Example 1. Welding was done on 500 μm copper at 275 W power against a laser beam without auxiliary gas.

The photo in Fig. 7 shows conduction mode welding on a 70 μm thick copper foil showing the microstructure through HAZ and welding. Welds were made using the parameters described in Example 1. The penetration depth of each sample was determined by first cutting a cross section and then etching the sample to reveal the microstructure of the weld and HAZ regions. Also one of the samples had a cross-sectional area and had a Vickers hardness across the base metal ranging from 133 to 141 HV, the weld bead was about 135 HV and HAZ ranging from 118 to 132 HV. The conclusion is that the hardness of the base material, HAZ and weld bead, eg the re-solidification zone, is close to that of the original material. In addition, the microstructures for the conduction mode weld bead, HAZ and base material are very similar except for minute differences in microstructure. Welds with these properties have never been previously observed in copper when welding by laser or other means. This weld quality is shown in FIG. 7 , in which a sample is cut cross-section with respect to the weld and etched to reveal the microstructure.

Accordingly, embodiments of the present invention include methods of welding copper-based materials to obtain subsequent welds and the resulting weld itself. Since these methods and welding involve welding two or more copper-based materials together, the hardness of the material (measured by an approved and established hardness test, e.g., Vickers hardness, ASTM test, etc.) in the area surrounding the weld is: . When the weld bead hardness is within the hardness of the base material, the weld bead hardness is within 1% of the base material hardness, and the weld bead hardness (e.g., re-solidification area) is within 5% of the base material hardness, the base material; The weld bead hardness is within 10% of the basic hardness. These methods and welds involve welding two or more copper-based materials together, wherein the hardness of the material (measured by an approved and established hardness test, e.g., Vickers hardness, ASTM test, etc.) in the area surrounding the weld is: . When the HAZ hardness is within the hardness of the base material, the HAZ hardness is within 1% of the base material hardness, the HAZ hardness is within 5% of the base material hardness, and the HAZ hardness is within 10% of the base material hardness.

Since these methods and welding involve welding two or more copper-based materials together, the microstructure, bead (eg, re-solidification region) and HAZ of the base material in the region surrounding the weld are identical. That is, there is no discernible difference in the microstructure that suggests or indicates the weakness of the welded structure of the weld zone or the weakness of the weld zone.

Referring to FIG. 8 , the microstructure observed for a 500 μm thick copper sheet sample when operating in keyhole welding mode. During the keyhole welding process, steam pools were clearly visible and the molten copper was slowly evacuated along the length of the weld. There are no signs of spatter in the welding process normally observed when welding with an IR laser during or after welding. This represents a stable and well-controlled keyhole process suitable for producing high-quality welds on electrical components. A keyhole mode weld cross section with very high quality and uniformity of the type shown in FIG. 8 can be obtained for low power densities of ^{800 kW/cm 2 or less.} The re-solidification region [1] - [2] is 442 μm to 301 μm and HAZ[2] is 1314 μm.

Embodiments of the present invention provide efficient heat transfer rates for copper materials; achieve the benefits of including a stable weld puddle; It relates to methods, apparatus and systems for welding copper to copper or other materials using a visible laser system having these advantages, particularly in conduction mode or keyhole mode of welding. Copper has high absorption in the blue wavelength range as shown in FIG. 9 . Currently preferred blue laser beams and laser beam systems and methods combine laser power to copper in a highly efficient manner. Current laser beam systems and methods heat the base material (the material to be welded, eg copper) faster than heat can be conducted in the laser spot. This provides very efficient and good welding properties for conduction mode laser welding. That is, the material of the laser beam is rapidly heated to the melting point and maintained at the melting point by the continuous laser beam to form a stable weld bead. In current conduction mode welding, the metal melts rapidly, but the penetration depth of the weld is governed by thermal diffusion into the material and proceeds spherically into the material. This is shown in FIG. 10 , which shows a schematic diagram of an embodiment of a conductive mode weld 1000 , with the welding direction indicated by arrow 1004 . For example, a laser beam 1001 of blue wavelength focuses and maintains the weld pool 1002 . Behind the weld pool 1002 is the solid weld material 1003 . A base material, for example copper metal or alloy, is underneath the weld. A shielding gas stream 1005 is also used.

An embodiment of the present invention relates to keyhole welding of copper using a blue laser system. These methods and systems open up new possibilities for the welding of thick copper materials as well as copper foil stacks including thick stacks. This keyhole welding mode occurs when the laser energy is absorbed so quickly that it melts and vaporizes the material to be welded. The vaporized metal creates a high pressure in the metal to be welded, opening a hole or capillary through which the laser beam can propagate and be absorbed. When the keyhole mode is initiated, deep penetration welding can be achieved. The absorption of the laser beam changes from an initial absorption of 65% for a blue laser in copper to 100% absorption in the keyhole. The high absorption may be due to multiple reflections out of the wall of the keyhole where the laser beam undergoes continuous absorption. When combined with the high absorption of copper at the blue wavelength, the power required to initiate and hold the keyhole is significantly lower than when using an IR laser. Referring to FIG. 11 , which shows a schematic diagram of an embodiment of a keyhole mode weld 2000 showing the welding direction by arrow 2007 . In the keyhole 2006 there is a metal/vapor plasma. Blue laser beam 2002 produces plasma cloud 2002 , weld pool 2003 , and solid weld metal 2004 . A shielding gas stream 2005 is also used.

Comparing the keyhole weld of FIG. 11 to the conduction mode weld of FIG. 10 , in the keyhole weld the wall of the final weld resolidification zone is more vertical through the part or base material than the conduction mode weld.

Preferably, the high power laser beams (eg, visible, green and blue laser beams) for embodiments of the present systems and methods are focused or have the ability to be focused through the optics of the system to a spot size of about 50 μm or greater and have at least 10 It has a power greater than W. The power for a laser beam comprising a blue laser beam may be 10 W, 20 W, 50 W, 100 W, 10-50 W, 100-250 W, 200-500 W and 1,000 W, higher and lower The output and all wavelengths within these ranges are considered. The spot size (longest cross-sectional distance, diameter for a circle) for these powers and laser beams is from about 20 μm to about 4 mm, less than about 3 mm, less than about 2 mm, from about 20 μm to about 1 mm, from about 30 μm to about 50 μm, about 50 μm to about 250 μm, about 50 μm to about 500 μm, about 100 μm to about 4000 μm, large and small spots and all sizes within these ranges are contemplated. The power density of the laser beam spot is about 50 kW/cm ² to 5 MW/cm ² , about 100 kW/cm ² to 4.5 MW/cm ² , about 100 kW/cm ² to 1000 kW/cm ² , about 500 kW/ cm ² to 2 MW/cm ² , greater than about 50 kW/cm ² , greater than about 100 kW/cm ² , greater than about 500 kW/cm ² , greater than about 1000 kW/cm ² , greater than about 2000 kW/cm ² and higher and lower power densities and all power densities within these ranges are contemplated. Welding speeds of about 0.1 mm/sec to about 10 mm/sec for copper, and slower and faster speeds, depend on various conditions and all speeds within these ranges. Since the speed is dependent on the thickness of the material to be welded, the speed per thickness (mm/sec) in mm of thickness may be, for example, 0.1/sec to 1000/sec for 10 μm to 1 mm thick copper.

Embodiments of the method and system may use one, two, three or more laser beams to form a weld. The laser beam can be focused on the same general area to initiate welding. The laser beam spots can overlap and coincide. A plurality of laser beams may be used simultaneously and in coincidence and simultaneity. A single laser beam can be used to initiate welding and then a second laser beam can be added. A plurality of laser beams may be used to initiate welding and then fewer beams may be used, for example a single beam. The laser beams of these plurality of laser beams may have different powers or the same power, the power densities may be different or the same, the wavelengths may be different or the same, and combinations and variations thereof. The use of additional laser beams may be simultaneous or sequential. Combinations and variations of these embodiments using multiple laser beams may also be used. The use of multiple laser beams can suppress spatter in welding and can do so in deep penetration penetration welding methods.

In an embodiment, hydrogen gas, H _{2 ,} may be mixed with an inert gas to remove the oxide layer from the base material during the welding process. Hydrogen gas flows over the welding area. Hydrogen gas also promotes wetting of the weld. Hydrogen gas may be added to or form a mixture with the shielding gas and applied to the weld as part of the shielding gas. These mixtures may include, for example, Ar-H ₂ , He-H ₂ , N ₂ -H ₂ .

18 provides examples of penetration depth of copper, laser beam power, and welding speed for various embodiments of laser system configurations and material thicknesses ranging from 127 μm to 500 μm.

Conduction of copper, copper alloys and other metals using blue laser systems mode welding method

The present system overcomes the problems and difficulties associated with IR welding when applied to copper-based materials. The high absorption (65%) of copper at the blue wavelength of the present laser beam and beam spot overcomes the material's thermal diffusivity and allows it to do so at a relatively low power level of ~150 W. The interaction of the copper with the present blue laser beam allows the copper to easily reach its melting point and allows a wide processing range.

In an embodiment, normal conduction mode welding is performed and a high quality weld is obtained at a stable and high speed through the use of a part fixture or fixture.

A welding fixture is used to hold the material to be welded in place during a thermal transient induced in the part by a laser beam. 12 and 12A are perspective and cross-sectional views, respectively, of an embodiment of a linear section of a welding clamp that may be used for overlap, butt and even edge welding. Welding fixture 4000 has a base plate or support structure 4002 . Two clamp members or hold downs 4001 are attached to the base plate 4002 . The hold down 4001 has a tab that rests on the surface of the base plate 4002 and a free end that contacts and retains the workpiece(s) to be welded. The base plate 4002 in the area between the free ends for the hold down 4001 has a slot 4003, for example 2 mm wide by 2 mm deep. Four bolts (eg, 4004) (other types of adjusting fasteners may also be used) adjust, tighten, and secure the clamp to the work piece to hold or secure the work piece.

A preferred material for such fixtures is a low thermal conductivity material such as stainless steel because it is strong enough to apply the clamping pressure necessary to hold the part in place during welding. In embodiments, the clamp, baseplate, and both may have an insulating quality or effect on the workpiece during the welding process. The use of materials with low thermal conductivity for the fixture prevents, minimizes, and reduces heat deposited on the part shape from being rapidly conducted by the fixture itself. This provides additional advantages when welding materials with high thermal conductivity, such as copper. Thus, the material chosen for the clamp, the width of the clamp and the gap under the part are all parameters that determine the penetration depth of the weld, the width of the weld bead and the overall quality of the weld bead. Referring to FIG. 14 , a cross-section (after etching) is shown in which conduction mode welding can be identified by the circular shape 6001 of a weld bead in a base material, eg, a workpiece. Welding takes on this shape due to the isotropic nature of the heat transfer process of copper or any material when heat is applied to the upper surface of the part.

In a preferred embodiment, the base plate 4002 of the fixture 4000 is constructed of stainless steel, and a 2 mm wide gap 4003 is cut into the base plate and positioned directly below the weld area (as a cover gas or shielding gas). ) Filled with an inert gas such as argon, helium or nitrogen to minimize oxidation of the backside of the weld. The cover gas may be a mixture of hydrogen and an inert gas. The clamp 4001 is designed to apply pressure to the part to be welded at a point 2 mm from the edge of the gap 4003 of the base plate 4002 . Thus, in this embodiment a 6 mm wide area of the part to be welded is open to the laser beam (recognizing that the laser beam is slightly away from the clamp). The positioning of the clamp allows the laser beam to easily access the surface as well as to hold the part securely. This type of clamp is the preferred method for butt welding two foil or copper sheets varying in thickness from 50 μm to several mm. This fixture is also suitable for laminating together two thick copper plates ranging from 200 μm to several mm. The amount of clamping pressure is very important, and depending on the amount of laser power, welding speed, part thickness and type of welding to be performed, clamping bolts can have a torque of 0.05 Newton-m (Nm), up to 3 Nm or more, for thick materials, more. can be tightened with These torque values are highly dependent on the bolt size, thread engagement, and distance from the bolt center to the clamping point.

In an embodiment, good quality welds are obtained by providing sufficient clamping force to prevent movement of the part during welding while minimizing parasitic heat loss to the fixture itself. 12 and 12A show a cross-section of a straight portion of a welding fixture and can be used in any 2-D path (eg, -S - , -C -. - W - etc.). In other embodiments, the fixture may be preheated or heated during the welding process to increase the penetration rate or depth of the weld while reducing parasitic heat loss to the fixture. When heated to several 100 °C, fixtures can improve welding speed or penetration depth and quality by a factor of 1 or more. The shielding gas for the upper side of the weld is delivered in the longitudinal direction from the front of the welding running direction to the rear of the welding running direction as shown in FIG. 10 . Bead on plate conduction mode welding is shown in FIG. 14 and is performed for this fixture 4000 in a 254 μm thick copper sheet. The freeze pattern of the weld bead shows a spherical melt pattern typical for this type of weld.

Lap welding of two parts using a conduction mode welding process requires that the parts be placed and held in close contact. The two parts (collectively the work piece) can preferably be placed in a fixture of the type shown in FIGS. 13 and 13A , respectively, in perspective and cross-sectional views of fixture 5000 . The fixture 5000 has a base plate 5003 and two clamps 5002 . The clamp has four slots (eg, 5010) corresponding to hold down bolts (eg, 5001). In this way, the position of the clamps with respect to the workpiece relative to each other as well as the amount of clamping force or pressure is adjusted and fixed. The clamp may have magnets to assist in positioning and securing. Clamp 5002 has an inner channel for carrying the shielding gas, for example 5004 . Channel 5004 is in fluid communication with a shielding gas outlet (eg, 5005 ). The shielding gas outlet and shielding gas channel of the shielding gas delivery system within the clamp. Thus, the gas delivery system is through a series of holes along the length of the clamp that deliver an inert gas such as argon, helium or nitrogen. Argon is the preferred gas because it is heavier than air and deposits on the part to displace oxygen and prevent oxidation of the top surface. A small amount of hydrogen can be added to the inert gas to facilitate removal of the oxide layer of the part and to promote wetting of the part in the melting process.

Insert 5006 is also used to force the individual foils of the foil stack to maintain and maintain contact with each other in the stack. Inserts 5006 can be stretched and forcefully applied to the foil to make firm and uniform contact with each other. 13 and 13A, insert 5006 is inverted-V shaped. Depending on the stack and individual thickness of the foils, they can be curved, humps or other shapes. Also, in the embodiment of FIGS. 13 and 13A , insert 5006 is adjacent to clamp 5002 but not covered by clamp 5002 . The insert may be removed from the end of the clamp, or one or both of the clamps may partially cover the insert.

In a preferred embodiment, the base plate 5000, like the clamp 5002, is made of stainless steel. The fixing device may be made of ceramic or insulating material. A hump 5006 provides pressure from the weld bottom to keep the overlapping plates (two, three, ten, etc.) in close contact. In this embodiment, a device for shielding the gas in the form of a series of holes along the length of the clamp carrying an inert gas such as argon, helium, or nitrogen is built into the clamp 2 . Argon is the preferred gas because it is heavier than air and deposits on the part to displace oxygen and prevent oxidation of the top surface. The insert hump 5006 of the base plate 5003 may also have a series of channels, holes, or slots to deliver a cover or shielding gas to the backside of the weld to prevent oxidation. The fixture 5000 represents a cross-section of a straight portion of a weld, as shown in the drawing, and may be designed in any two-dimensional path to weld any shape together. In this application, the torque value of the bolt may be too high a torque value, for example 0.1 Nm, depending on the nature of the work piece, and if the torque value is too high, for example > 1 Nm, the part may not be able to keep in contact. and parasitic heat transfer reduces the efficiency of the welding process, reducing penetration and weld bead width.

Welding copper, copper alloys and other metals using a blue laser system keyhole mode Way

Blue laser light has a much higher absorption level (65%) than IR lasers and can initiate keyhole welding at a relatively low power level of 275 W (in addition to the 2,000 to 3,000 W required for an IR system to initiate the keyhole welding process). Prepared, IR systems will face more runaway issues, among other issues, upon launch). The absorption increases as the keyhole mode begins with the blue laser system, increasing from 65% to about 90% and then to 100%, so it is no longer a runaway process. Therefore, the present keyhole welding process has a very different absorption time profile from IR. The present blue keyhole welding process has an absorption time profile shape onset for welding progress of 35% or less. Initiation of the blue laser welding process and transition to continuous welding using the present laser welding system is accomplished without rapidly changing the laser's power level or welding speed, as is necessary when using an IR laser to prevent spatter. A high-speed video of initiating keyhole welding when using a blue laser shows a reliable process capable of welding multiple layers of copper foil and plate with minimal or no spatter emitted from the keyhole. Cross-sections of two keyhole weld samples are shown in FIGS. 16 and 17 , where the material freezing pattern is clearly different from the shape of the conduction mode weld sample shown in FIG. 14 . As can be seen in Figures 16 and 17, the formation of a material freezing pattern perpendicular to the surface of the material is conducted in conduction mode welding because heat transfer occurs along the entire length of the keyhole extending through the surface of the part to the final weld depth. different from This is in contrast to conduction mode welding, where all the laser energy is deposited on the material surface.

Keyhole welding processes, such as conduction mode welding processes, require the part to be held in a fixture to prevent any movement during welding. The keyhole mode is typically used in lap welding configurations where a keyhole penetrates the part to weld two or more stacks of parts together (see, eg, FIG. 17 ).

The laser system of FIG. 20 can generate a 275 W blue laser beam with a power density at a point ^{of 800 kW/cm 2 .} The laser system of FIG. 20 has a first laser module 1201 and a second laser module 1202 , the laser beam leaving the laser module and following the laser beam path as shown by ray tracing 1200 . The laser beam passes through a focusing lens configuration 1205 and redirecting mirrors 1203 and 1205 having a 100 mm focusing lens and a 100 mm protective window. The focusing lens of configuration 1205 creates a spot 1250 .

The laser system shown in FIG. 21 can be used to create either a 400 μm spot or a 200 μm spot. The laser system of FIG. 21 is composed of four laser modules 1301 , 1302 , 1303 , and 1304 . The laser modules may each be of the type disclosed and taught in US Patent Publication No. 2016/0322777, the entire disclosure of which is incorporated herein by reference. For example, the module may be of the type shown in FIG. 19 , in which the composite beam from each laser diode sub-assembly 210 , 210a , 201b , 210c produces a beam from four laser diode sub-assemblies. It redirects into a single beam and propagates to a pattern mirror (eg, 225 ) that is used to combine. A polarizing beam folding assembly 227 folds the beam in half in the slow axis to double the brightness of the composite laser diode beam. The telescope assembly 228 expands the combined laser beam on the slow axis or compresses the fast axis to allow the use of smaller lenses. The telescope 228 shown in this example expands the beam by a factor of 2.6, increasing its size from 11 mm to 28.6 mm while reducing the divergence of the slow axis by the same factor of 2.6. When the telescope assembly compresses the high-speed axis, it becomes a double telescope, reducing the high-speed axis from a 22 mm high (total composite beam) to an 11 mm high, resulting in an 11 mm x 11 mm composite beam. This is a preferred embodiment because of its lower cost. Aspheric lens 229 focuses the composite beam.

It should be understood that at 500 watts and a 200 μm spot, the power density is >1.6 MW/cm ² , which is substantially higher than the keyhole welding threshold at this wavelength. At these power densities, even blue lasers have the potential to create spatter and porosity in the weld. However, since the absorption is well controlled, it has the ability to suppress, control or eliminate spatter. The first way to suppress spatter is to reduce the output level when the spatter process starts while keeping the welding speed constant. A second method of suppressing spatter is to extend the weld puddle to allow shielding gas and vaporized metal to escape from the keyhole, resulting in a spatter-free and defect-free weld. A third method of suppressing spatter is to shake the blue laser beam using a set of galvanometer motors or a set of mirrors mounted on a robot. A fourth method of suppressing spatter is to reduce the pressure of the welding environment using a vacuum. Finally, a fifth method of suppressing spatter is to modulate the laser beam output in the range of 1 Hz to 1 kHz or up to 50 kHz. Preferably, the welding parameters are optimized to minimize spatter during the process.

In general, embodiments of the present invention include laser processing of materials, laser processing, particularly lasers with high absorption by the material, by matching a preselected laser beam wavelength to the material to be processed to have a high or increased level of absorption by the material. It relates to laser welding of materials using a beam.

An embodiment of the present invention relates to welding or bonding a material having a higher absorption for these wavelengths through laser processing using a laser beam having a visible laser beam having a wavelength of 350 nm to 700 nm. In particular, the laser beam wavelength is at least about 30%, at least about 40%, at least about 50%, and at least about 60% or more and between about 30% and about 65%, between about 35% and 85%, between about 80%, about 65%, It is predetermined based on the material to be laser processed to have an absorption of about 50, and about 40%. Thus, for example, a laser beam having a wavelength of from about 400 nm to about 500 nm is used to weld gold, copper, brass, silver, aluminum, nickel, alloys of these metals, stainless steel and other metals, materials and alloys. do.

Blue lasers for welding materials such as gold, copper, brass, silver, aluminum, nickel, nickel plated copper, stainless steel and other materials, plated materials and alloys, for example lasers with wavelengths from about 405 to about 495 nm Use is preferred because of the high absorption of the material at room temperature, for example greater than about 50%. One of the many advantages of the present invention is the ability of a preselected wavelength laser beam, such as a blue laser beam, to better couple laser energy to a material during laser operation, for example a welding process. By better coupling the laser energy to the material to be welded, the possibility of a runaway process is greatly reduced and preferably eliminated. The better coupling of laser energy also allows the use of low power lasers, providing cost savings. A better bond also provides more positive control, higher tolerances and thus greater weld reproducibility. These capabilities, not found in IR lasers and IR laser welding operations, are important for products in the electronics and power storage sectors, among other products.

In an embodiment, a blue laser operating in CW mode is used. CW operation may be preferred over pulsed lasers in many applications because of its ability to rapidly and fully modulate the laser power and control the welding process in a feedback loop, resulting in a highly repeatable process with optimal mechanical and electrical properties.

In an embodiment of the present invention, laser processing of one, two or more components is included. The component may be made of any type of material that absorbs the laser beam, such as laser beam energy, plastics, metals, composites, amorphous materials, and other types of materials. In an embodiment, laser machining includes soldering two metal components together. In an embodiment, laser machining includes welding two metal components together.

In an embodiment, the laser welding operation is a tool selected from the group consisting of automatic welding, laser-hybrid welding, keyhole welding, lap welding, filet welding, butt welding, and non-autogenous welding; Systems and methods are provided.

Laser welding techniques can be useful in many different situations, particularly where welding is required to form electrical connections, particularly power storage devices such as batteries. In general, embodiments of the present laser welding operations and systems include visible wavelength, preferably blue wavelength lasers, which means that only the base material is used and is common in keyhole welding, conduction welding, lap welding, fillet welding and butt welding. It may be an autogenous laser. Laser welding can be non-autogenous, in which filler material is added to the molten puddle to “fill” gaps or to create raised beads for weld strength. Laser welding techniques may also include laser material deposition (“LMD”).

Embodiments of the present laser welding operation and system include a visible wavelength, preferably blue wavelength laser, which may be a hybrid welding in which an electric current is used in conjunction with a laser beam to provide a faster supply of fill material. Laser hybrid welding is by definition non-spontaneous.

Preferably, in some embodiments an active weld monitor, such as a camera, is used to check weld quality on the fly. These monitors may include, for example, X-ray examination and ultrasound examination systems. In addition, stream beam analysis and output monitoring can be utilized to fully understand system characteristics and operating characteristics.

Embodiments of the present laser system may be hybrid systems that combine novel laser systems and methods with existing milling and machining equipment. In this way materials may be added and removed during manufacturing, construction, re-finishing or other processes. Examples of such hybrid systems using other embodiments of laser systems invented by one or more of the inventors are disclosed and taught in US Patent Application Serial No. 14/837,782, the entire disclosure of which is incorporated herein by reference. Included.

Typically, in embodiments, laser welding uses a very low gas flow to keep the optics clean, an air knife to keep the optics clean, or an inert environment to keep the optics clean. Laser welding may be performed in air, an inert environment or other controlled environment, for example N ₂ .

Embodiments of the present invention include copper, pure copper, copper alloys and all materials having a sufficient amount of copper to have about 40% to 75% absorption at a blue laser wavelength, preferably from about 400 nm to about 500 nm. Great advantages can be found in welding materials.

There are two preferred autogenous welding modes performed with embodiments of the present laser system and process, conduction welding and keyhole welding, and the autogenous welding they produce. Conduction welding is when two pieces of metal are welded together using a laser beam of low intensity (< 100 kW/cm ^{2 ).} Here, two pieces of metal are placed against each other, so that one can be overlapped and completely overlapped. Conduction welding does not tend to penetrate as deeply as keyhole welding and generally produces a characteristic "spherical" shape weld joint for butt welding, which is very strong. However, keyhole welding occurs with relatively high laser beam intensities (> 500 kW/cm ² ) and these welds can penetrate deep into the material and often penetrate multi-layered materials when the materials overlap. Although the exact threshold for transition from conduction mode to keyhole mode has not yet been determined for blue laser sources, keyhole welding has a characteristic "v" on top of the material with nearly parallel channels of re-frozen material penetrating deep into the material. have a shape The keyhole process relies on reflecting a laser beam from the side of a metal molten pool to deliver laser energy deep into the material. Although these types of welding can be performed with any laser, blue lasers are expected to have significantly lower thresholds for initiating these types of welding than infrared lasers.

Electroplating using a blue laser operation to weld these materials, including blue laser welding of electroplated materials, such as materials electroplated with copper, materials electroplated with platinum, and materials electroplated with other conductive materials. Welding of used materials is considered.

Welding processes for copper require that power be efficiently coupled to the part, and that the welding process be capable of producing stable, low porosity, low spatter welds. The present invention achieves these and other objects. Blue lasers achieve the first part of these requirements at wavelengths that are more absorbed by copper (65%) compared to IR lasers (<5%). The second requirement is a function of laser absorption as well as processing ramp or time profile, fixture, beam profile and quality, and the clamping pressure used on the part. This embodiment provides that both keyhole mode and conduction mode welding is possible by using a blue laser as a heat source. Conduction mode welding does not create any spatter or porosity of the part during the process. The keyhole mode of welding allows for greater penetration. This high-power blue CW laser source embodiment is ideal for welding copper parts with very low porosity and very low in-process spatter.

Full penetration is based on bead-on-plate testing of 1 mm thick copper plates using a 600-watt blue laser with normal spatter remaining on the surface. A 600-watt, CW laser is focused at a spot size of about 200 μm, resulting in an average intensity ^{of 2.1 MW/cm 2 at the surface of the part.} This strength is much higher than the power density required to initiate and hold the keyhole of the part. During the welding process, if keyholes are formed quickly and full penetration is achieved, the melt puddle presents a very stable surface that exhibits low turbulence in the weld puddle as the weld progresses. A stable welding process is observed at various welding speeds and, among other things, the Ar-CO ₂ cover gas suppresses surface oxidation during the welding process. This ability to produce stable keyhole welds can be attributed, among other things, to the high absorption of copper in blue. The blue laser light is uniformly absorbed by the wall of the keyhole during the welding process, but when instability occurs in the keyhole due to the turbulence of the melt puddle, the input heat is maintained and the keyhole remains stable.

The following examples are provided to illustrate various embodiments of the present laser system and operation, in particular a blue laser system for welding components, including components of electronic storage devices. These examples are for the purpose of illustration, and may be prophetic, and should not be considered as the scope of the present invention, and are not otherwise limiting.

Example 1

The laser source is a high power blue direct diode laser capable of 0 to 275 watts. The beam is delivered through a 1.25X beam expander and focused by a 100 mm aspherical lens. The spot diameter of the workpiece is 200 μm x 150 μm, which produces a power density at a ^{maximum power of 1.2 MW/cm 2 .} A stainless steel fixture was used to hold the sample in place _{and tests were performed with He, Ar, Ar-CO 2} and nitrogen, all of which were beneficial and gave the best results with _{Ar-CO 2 .}

Example 1A

Using the system of Example 1, initial test results produced high quality conduction mode welds at a power level of 150 watts on a copper surface. A series of Bead on Plate (BOP) tests were performed to characterize the welds produced by the high-power blue laser source. Figure 1 shows a chevron pattern for conduction mode welding, the unique properties of this welding are that no spatter occurs in the welding process, and the microstructure and weld hardness similar to that of the base material are similar to those of the base material. 1 shows the BOP formed when welding with a blue laser of 150 W to 70 μm thick copper foil.

Example 1B

Using the system of Example 1 and scaling the laser's power output to 275 watts, the power density increased to ^{1.2 MW/cm 2 , which is sufficient for initial keyhole welding of copper.} 2 shows an example of keyhole welding on a 500 μm thick copper sample. During the keyhole process, the vapor pressure generated in the keyhole pushes the molten copper out of the weld bead. This can be seen in Figure 4 where the ejected copper is lined with the edge of the weld bead. This evacuation process is stable and does not cause micro-explosives in the material, resulting in no spatter patterns observed when welding copper with an IR laser source.

Example 1C

Welding experiments were performed on copper thicknesses ranging from 127 to 500 μm using the system of Example 1. 3-5 summarize the results of these BOP tests. Figure 3 shows the decrease in penetration depth at the expected rate following full penetration at 275 W up to 9 m/min. FIG. 4 shows BOP results for complete penetration of up to 0.6 m/min for no-assist gas and 0.4 m/min for Ar-CO _{2 cover gas.} Figure 5 shows penetration depth versus velocity for 500 μm copper at 275 W.

Example 2

The fixture 5000 of FIGS. 13 and 13A is used to successfully lap weld two stacks of copper foils with a thickness of 178 μm with conduction mode welding. When heated to a few 100°C, the fixture improves welding speed and quality by a factor of two or more because the energy lost to heating the part during welding is now provided by preheating. The shielding gas for the upper side of the weld is delivered from the front in the welding running direction to the rear in the welding running direction as shown in FIG. 10 .

Example 3

Two 125 μm thick copper plates were lap welded together using fixture 5000 with conduction mode welding. This weld is shown in the cross-sectional photograph of FIG. 15 .

Example 4

Using the fixture 5000 shown in FIGS. 13 and 13A , a stack of 40 copper foils 10 μm thick were welded without porosity and defects. A cross-section of this weld is shown in FIG. 17 . The welding of these stacks depends on the method of preparing the foil, the method of securing the foil, and the torque applied to the clamp. The foil is sheared and flattened, then washed with alcohol to remove any manufacturing or handling oil and finally wrapped in a fixture. The clamping bolt 5001 is tightened with a torque of 1 Nm to ensure that the part is held securely in place during the welding process. The lasers used to weld these parts consisted of four 150-watt lasers shown in FIG. 19 optically combined as shown in FIG. 21 to create a 500 watt laser system. This laser produces a 400 μm spot with an average power density of 400 kW/cm ² , and a peak power density sufficient to initiate a keyhole welding process.

Example 5

An example of the present laser beam welding technique is evaluated using a first full penetration, bead on plate (BOP) welding of a 1 mm thick copper plate with a 600 watt blue laser leaving nominal spatter on the surface. A 600-watt, CW laser is focused on a spot size of about 200 μm resulting in an average intensity of ^{2.1 MW/cm 2 at the surface of the part.} This strength is much higher than the power density required to initiate and hold the keyhole of the component. Rapid formation of keyholes in the welding process is observed and once full penetration is achieved, the melt puddle exhibits a very stable surface that exhibits low turbulence in the weld puddle as the weld progresses. Stable welding process can be seen in a wide range of welding speeds by suppressing surface oxidation during welding by using AJ-CO _{2 cover gas.} This ability to produce stable keyhole welds can be attributed to the high absorption in blue copper and the uniformity and high quality of the laser beam. The blue laser light is uniformly absorbed by the wall of the keyhole during the welding process, but when instability occurs in the keyhole due to the turbulence of the melt puddle, the input heat is maintained and the keyhole remains stable.

Example 6

Embodiments of the present invention use the present high power visible lasers, particularly blue lasers, blue green lasers and green lasers for industrial applications such as welding. In embodiments of these processes, power levels of 500 to 600 W and spot sizes of 200 to 400 μm are used. The wavelengths for these examples are in the blue range. Stable conduction mode welding of copper is observed over a wide range of speeds for both 400 and 200 um spot sizes in oxygen-free copper (OFC). This welding mode is completely dense with no spatter and no signs of porosity throughout the welded part. Stable keyhole mode welding is only observed for 200 μm spot size copper, but 400 μm spot size can also achieve keyhole welding in less conductive materials such as Inconel and stainless steel. The modeling of the welding process shows significant differences in the shape and size of the weld puddle when welding copper compared to stainless steel. Stainless steel with low thermal conductivity exhibits a typical teardrop-shaped weld puddle, while copper with high thermal conductivity exhibits a much smaller circular weld puddle at the same power level used to weld stainless samples.

Example 7

Laser welding of metals using a blue, blue-green or green laser beam is performed without shaking the beam. These welds have deep penetration. Thus, wobble free welding of metals including copper foil copper plates using these laser beams is provided. Wobble-free welding is provided for aluminum, stainless steel, copper, aluminum-based metals, stainless steel-based metals, copper-based metals and alloys thereof.

In this embodiment of wobble-free laser welding, blue laser welding is performed with copper having a thickness of less than 1 mm and a blue laser beam having a wavelength of 450 nm.

In this embodiment of wobble-free laser welding, blue laser welding is performed on aluminum using a blue laser beam having a thickness of less than 1 mm and a wavelength of 450 nm.

In this embodiment of wobble-free laser welding, blue laser welding is performed on stainless steel using a blue laser beam having a thickness of less than 1 mm and a wavelength of 450 nm.

Example 8

In an embodiment the 00-watt laser has four 200-watt blue laser modules that provide a laser beam with a wavelength of 450 nm. The laser diodes are individually collimated and the beam divergence is circularized as shown in FIG. 19 , resulting in a beam parameter product of 22 mm mrad for each module. The laser beams from the four blue laser modules are optically sheared in both horizontal as well as vertical directions, filling the aperture of the 100 mm diameter focusing optics as shown in FIG. This composite beam (450 nm) has a beam parameter product of 44 mm mrad and is suitable for firing into a 400 μm optical fiber. For Examples 8A-8K and 9, no optical fiber is used and this blue laser beam is delivered through free space to the workpiece.

For these examples, an optical breadboard with a 4' x 6' optical bench that can incorporate real-time beam diagnostics into the setup is used. The composite output beam is sampled with a 1% beam sampler and a portion of the beam is sent to a far-field profile camera and power meter. The far-field is created with the same focal length lens (100 mm F/1 lens or 200 mm F/2 lens) as the welding lens. Both lenses are BK7 spherical lenses from ThorLabs. The lens is underfilled to about 80 mm, and the spot of the workpiece is about 200 μm for a 100 mm FL lens and about 400 μm for a 200 mm FL lens.

Beam caustic is measured by transforming the Ophir beam profiler through the focus of a 100 mm FL lens in the beam sampling arm of the setup and measuring the diameter of the beam at the 95% enveloped power point. A graph of beam pseudonym is shown in FIG. 22 . These measurements show a relatively short depth of focus for a 100 mm FL lens.

A Fanuc 6-axis robot (FANUC M-16iB) is used to focus the free space beam with cover gas provided by a 3/8" diameter sparger tube mounted on a robot adapter and oriented along the welding direction. It is used to move the sample through

For Examples 8A-8K and 9, an embodiment of a welding fixture of the type shown in FIGS. 12 and 12A is used. Welding fixtures are part of the welding process and can affect the depth of penetration, welding speed, and both, that can be achieved when welding highly thermally conductive materials. 12 and 12A are views of an embodiment of a welding fixture. Aluminum (6061 series) is used in one embodiment. In another embodiment, stainless steel 316 is used. Aluminum welding fixtures tend to dissipate heat from the part quickly, whereas stainless steel fixtures retain most of the heat within the part. Both materials are evaluated with different methods of clamping the sample (eg, workpiece, part). An inert gas such as Ar-CO ₂ flows over the top of the part placed in the fixture to inhibit any oxidation of the part during the welding process. A small gap 4003 is located below the center of the sample to minimize the heat sink at the bead point of the plate example and allow auxiliary gas to be added to the backside of the weld.

In the keyhole mode of welding, it is possible to create a strong plume when welding. Since the atoms and ions of the plume readily absorb light at 450 μm, these plumes must be controlled and preferably suppressed. A 3/8" diameter tube sparger is used to suppress plume by delivering 50 scfh of argon or argon-CO ₂ across the top of the part. To control plume and prevent oxidation of the part, argon, argon-CO ₂ Welding can be performed or made with a variety of gases including , air, helium and nitrogen.First of all, the goal of optimizing the welding process is to achieve maximum penetration at the fastest possible rate.Data presented in examples 8A to 8K uses argon as the cover gas, and plume management is desirable and preferred in other laser welding and machining applications such as butt welding.

For the 500 watt weld tests of Examples 8A-8F, focusing the beam to a 400 μm spot size using a 200 mm focal length lens resulted in an average intensity of ~400 kW/cm ² and a peak intensity of 800 kW/cm ² . come close

For the 600 watt weld tests of Examples 8G through 8K, focusing the beam to a 200 μm spot size using a 100 mm focal length lens resulted in an average intensity of about 2.1 MW/cm ² and a peak intensity of 4.5 MW/cm ² . come close

Example 8A

500 watts, 400 μm spot size and 400 kW/cm ^{2 using the laser, process, and setup of Example 8.} Bead-on-plate welding was performed and evaluated on copper (OFC), stainless steel 304 and aluminum (1100 series) using average power density. The samples were all cut into sizes of 10 mm x 45 mm with a shearing machine and washed with acetone before processing. The surface finish is as supplied from McMaster Carr and has a rolled finish for thinner samples and a mill finish for thicker samples. These evaluations characterize the full penetration capability of the welding process of Example 8 for a given sheet thickness.

Bead on plate evaluations were performed with oxygen-free copper (99.99% - 110) samples ranging in thickness from 80 μm to 500 μm using the laser, process and setup of Example 8. 23 shows the welding speed at which a fully penetrated bead was observed on the back side of a welded sample.

Prior to evaluation, the sample was wiped with acetone and clamped to the fixture with bolts torqued to 1 Newton-meter. The fixture and sample were held at an angle of 20 degrees to the beam normal to prevent retroreflection to the laser, resulting in a spot stretch of 400 μm x 540 μm for the 200 mm FL lens. The beam angle is from the beam normal to the trailing side of the part to be welded. This inclination of the sample is likely to reduce the maximum welding speed that can be achieved due to the lower strength of the part. The welding sequence is when the robot is commanded to translate the part with a sufficient distance between the part and the laser beam to ensure that the robot has reached the programmed speed, and the laser is initiated when the welding fixture intersects the position of the laser beam. will become The part is translated through the beam at a constant speed, and when it reaches the end of the welding fixture, the laser beam is turned off and the robot is commanded to return to its home position. The sample is cross-sectioned, polished and etched to reveal the microstructure. All welds exhibit a spherical melt-freeze pattern indicative of conduction mode welding.

Example 8B

Butt welding of samples was also evaluated using the laser, process and setup of Examples 8 and 8A. The part was prepared as in Example 8A and clamped with the same clamping force. The edge of the sample produced by shear is the basis of the butt welded part. Some of the results of these tests are shown in FIG. 24 . Weld speed is the speed at which two parts can be joined by a full penetration weld indicated on the reverse side of the welded part. No spatter was observed during welding or on the welded parts, indicating a conduction mode welding process.

Example 8C

During evaluation of the copper 110 series samples of Example 8A, a dependence on the penetration depth of the weld as a function of sample thickness was observed. 25 shows how penetration depth can decrease with increasing copper sample thickness. This dependence is due to the greater thermal mass of the part and the high thermal conductivity of copper to dissipate heat quickly from the weld bead. This is due, in part, to copper's high thermal conductivity and ability to effectively dissipate laser energy in the welding process. As can be seen in FIG. 25 , the depth of penetration can be reduced by a factor of 4 or more as the material thickness increases by a factor of 2 at a given rate. The penetration depth of the upper case does not decrease as dramatically as in the other two cases, as it is much slower and saturates the copper's ability to dissipate laser energy. Therefore, when designing the welding process of copper using the conduction mode process, the finite thickness of the part to be welded must be considered.

Yes 8D

Using the laser, process and setup of Examples 8 and 8A, aluminum 1100 series samples were welded and evaluated. An aluminum 1100 series sample was prepared and mounted on the same welding fixture as the copper part of Example 8A. The welding process is similar to the copper welding process of Example 8A, except that only the robot speed is changed. The welding speed shown in Fig. 26 is a case where a completely penetrating bead is observed on the back side of the thickness portion. No spatter was observed in the melt puddle observed during the welding process.

Example 8E

Butt welds and weld tests were performed on two aluminum 1100 samples placed side-by-side in a welding fixture using the laser, process, and setup of Examples 8 and 8A. The sample was prepared with a shearing machine and the two edges had no special preparation before welding was performed. Samples are wiped with acetone before welding. The welding process is the same as described for the copper part in Example 8A except for the welding speed. The final weld rates shown are the rates at which fully penetrating beads are obtained over the entire length of the sample to be welded. A summary of this data is shown in FIG. 27 .

Example 8F

BOP welding and welding tests were performed on 304 stainless steel samples using the laser, process and setup of Examples 8 and 8A. The sample was cut to a size of 10 mm x 45 mm to fit the fixture, wiped with acetone, and the robot speed was adjusted until a full penetration weld was obtained on the test sample. In addition, no spatter or porosity was observed in the welded samples. The results of these tests are shown in FIG. 28 .

Yes 8G

Welding and evaluation of the 600 watt system and process of Example 8 was performed. 100 mm focal length lens the beam using focusing a 200 μm spot size, with an average intensity of about 2.1 MW / cm ^2, and is the peak intensity reached 4.5MW / cm ^2. A series of welds were made and tests were performed with these higher power levels and shorter focal length lenses (100 mm) to further evaluate and demonstrate the penetrating ability of these lasers at various speeds. The average strength in these tests is 2.1 MW/cm ² and the power density is within the requirements for vaporizing copper and making keyholes. The component is tilted 20 degrees, reducing the effective power density to 1.4 MW/cm ^{2 .} This is sufficient strength to initiate keyhole welding modes in copper, aluminum and stainless steel.

The first indication of the keyhole process in copper is a significant increase in spatter during the welding process. These spatters are observed with an on-axis camera while monitoring the weld puddle. Weld samples were sectioned, polished, and etched to reveal a microstructural freezing pattern typical of keyhole welding. The cross-section also exhibits a significant amount or porosity that the beam does not completely penetrate the part. However, the cross-section with full penetration of the beam showed nominal porosity.

Yes 8H

Using the laser, process and setup of Example 8 and Example 8G, longitudinal cross-sectioning of keyhole mode welds on a 500 μm thick copper 110 plate was performed to determine the porosity along the entire length of the weld, as shown in the photograph of FIG. . The leading 1 cm of the weld on the right side of the figure indicates a significant amount of porosity and lack of penetration through the sample. As heat builds up in the part during welding, the keyhole process completely penetrates the copper plate. These results indicate that when the keyhole process is stabilized, welds with nominal spatter and porosity can be produced.

Example 8I

Using the laser, process and setup of Examples 8 and 8G and based on the results of Example 8H, welding and testing were performed to first allow the keyhole to stabilize before moving the part. The welding process is modified by allowing a laser beam to stay on the part for a short time, then the robot is accelerated to drag a keyhole through the part. After a series of tests in which the dwell time was changed from 0.6 seconds to 1.5 seconds, the desired results were obtained with a dwell time of 0.6 seconds. 30 is a cross-sectional photograph of the bead-on-plate welding of copper 110 performed while the sample is translated at a speed of 1.1 m/min after dwelling in the sample for 0.6 seconds. A series of welds are performed at this rate to ensure that the process is stable and well controlled. All samples show similar results, very low porosity and very stable keyhole welds.

Yes 8J

Using the laser, process and setup of Examples 8 and 8G, welds were made and evaluated at various copper 110 material thickness ranges. A graph of the maximum welding speed achieved for full penetration of each sample is shown in FIG. 31 . Keyhole mode welding, translational mode welding, and conduction mode welding are all observed at these welding rates. The result is a significant increase in welding speed and penetration depth compared to the 500 watt, 400 μm system.

Yes 8K

Using the laser, process and setup of Examples 8 and 8G, stainless steel samples were welded and evaluated. The result is an overlap welding of four 304 stainless steel sheets at a speed of 1.2 m/min. The cross-sectional view shown in FIG. 32 shows the classical profile of a keyhole welded sample. The porosity of the bottom of the keyhole may occur due to the spacing between the 3rd and 4th sheets of the stack. This porosity can be eliminated by optimization of this welding process.

Example 9

Using the laser, process, and setup of Examples 8 and 8A, a series of tests were performed on an oxygen-free copper foil stack to determine how many sheets of foil can be lap-welded in a single pass. The experimental setup is the same as Example 8, but now the fixture is changed and a small steel insert is used in the gap below the center of the part. The foil is clamped in place and the sample tilted at an angle of 20 degrees to the beam normal is passed through the beam with ^{Ar-CO 2 cover gas.} The results of these tests are summarized in FIG. 33 for up to 40 foils in a stack. Two different lens configurations can be used to achieve very good results over a wide range of foil thicknesses and stacks.

34 is a photograph of an example of successful welding of 40 copper foils free of porosity and spatter on the top surface. This foil stack was welded at 500 watts with a 200 mm FL lens corresponding to a 400 μm spot size. The welding speed was 0.5 m/min. The way the seat is clamped can affect the weld quality, and good and consistent clamping of the seat provides consistently high quality welds.

Title and Examples

It is to be understood that the use of headings herein is for the sake of clarity and is not intended to be limiting in any way. Accordingly, the processes and disclosures described below the headings are to be read in the context of the entire specification, including various examples. The use of headings herein should not limit the scope of protection provided by the present invention.

It is noted that there is no need to provide or cover the theory underlying the subject matter of, or any novel and innovative processes, materials, performance, or other beneficial features and properties related thereto of the embodiments of the present invention. Nevertheless, various theories are provided herein to further advance the art in this field. The theory presented in this specification does not limit, limit or narrow the scope of protection accorded to the claimed invention, unless expressly stated otherwise. Many of these theories are not required or practiced in order to utilize the present invention. It is also to be understood that the present invention may lead to new and hitherto unknown theories for describing the function-features of embodiments of the methods, articles, materials, devices and systems of the present invention; Theories developed thereafter do not limit the scope of protection provided for the present invention.

The various embodiments of the systems, equipment, techniques, methods, activities, and operations described herein may be used in a variety of other activities and other fields than those described herein. Among other things, embodiments of the present invention describe the methods of Patent Application Publication Nos. WO 2014/179345, US 2016/0067780, US 2016/0067827, US 2016/0322777, US 2017/0343729, 2017/0341180, and US 2017/0341144, may be used with the apparatus and system, the entire disclosure of each of which is incorporated herein by reference. In addition, these embodiments may be used, for example, with other equipment or activities that may be developed in the future, and with existing equipment or activities that may be modified in part based on the teachings herein. In addition, the various embodiments described herein can be used with each other in different and various combinations. Thus, for example, the configurations provided in the various embodiments of the present specification may be used with each other. For example, an element of an embodiment having A, A' and B and an element of an embodiment having A'', C and D may be combined in various combinations, e.g., A, C, D, in accordance with the teachings herein. and A and A'' C and D, and the like. The scope of protection provided in the present invention should not be limited to the specific embodiments, configurations or arrangements described in specific embodiments, examples, or embodiments of specific drawings.

The present invention may be embodied in other forms than those specifically disclosed herein without departing from the spirit or essential characteristics thereof. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

Claims (20)

A method of laser welding a plurality of copper foils together, comprising:
a. placing a plurality of pieces of copper foil on a welding stand, wherein the foil contains at least about 50% copper;
b. applying a clamping force to the plurality of pieces of copper foil to clamp the pieces of foil together at a welding stand;
c. Directing a blue laser beam along a laser beam path at a plurality of pieces of copper foil, the laser beam having the following characteristics:
i. power of at least 500 watts,
ii. Beam parameter product of about 44 mm mrad or less,
iii. spot size of about 400 μm or less,
iv. an average strength of at least about 400 kW/cm ^{2 ,}
ⅴ. having a peak intensity of at least about 800 kW/cm ^{2 ;}
d. lap welding a plurality of pieces of copper foil together at a welding speed; and
e. providing a non-oxidizing beam cleaning gas in a space that follows a laser beam path in which the laser beam travels in free space from the optical element to the plurality of pieces of copper foil, wherein the cleaning gas removes plume material from the laser beam path and removes the plume material from the plurality of pieces of copper foil. preventing oxidation of the copper foil piece;
f. The welding speed, clamping force, and flow rate of the non-oxidizing cleaning gas are predetermined to provide a needle-needle weld without visible splatter and visible porosity;
A method of laser welding a plurality of copper foils together. The method of claim 1,
the beam is a CW beam,
A method of laser welding a plurality of copper foils together. The method of claim 1,
the beam is a pulsed beam,
A method of laser welding a plurality of copper foils together. The method of claim 1,
the beam has a wavelength of about 450 nm,
A method of laser welding a plurality of copper foils together. The method of claim 1,
the optical element is selected from the group consisting of a lens, a fiber face and a window;
A method of laser welding a plurality of copper foils together. The method of claim 1,
the cleaning gas is selected from the group consisting of argon, argon-CO ₂ , air, helium and nitrogen;
A method of laser welding a plurality of copper foils together. The method of claim 1,
The laser beam is not oscillated, thus providing a oscillation-free laser welding process.
A method of laser welding a plurality of copper foils together. The method of claim 1,
the plurality of copper foil pieces having 10 to 50 foil pieces;
A method of laser welding a plurality of copper foils together. The method of claim 1,
The copper foil piece has a thickness of about 80 μm to 500 μm,
A method of laser welding a plurality of copper foils together. 9. The method of claim 8,
each of the plurality of pieces of copper foil having a thickness of about 80 μm to 500 μm;
A method of laser welding a plurality of copper foils together. The method of claim 1,
the welding speed is at least 10 m/min,
A method of laser welding a plurality of copper foils together. A method of laser welding a plurality of metal pieces together, comprising:
a. positioning a plurality of metal pieces on a welding stand;
b. applying a clamping force to the plurality of metal pieces to clamp the metal pieces together at a welding stand;
c. Directing a blue laser beam along a laser beam path at a plurality of pieces of metal, the laser beam having the following characteristics:
i. power of at least 500 watts,
ii. Beam parameter product of about 44 mm mrad or less,
iii. spot size of about 400 μm or less,
iv. an average strength of at least about 400 kW/cm ^{2 ,}
ⅴ. having a peak intensity of at least about 800 kW/cm ^{2 ;}
d. blue laser beam welding a plurality of metal pieces together at a welding speed; and
e. providing a non-oxidizing beam cleaning gas in a space that follows a laser beam path in which the laser beam travels in free space from the optical element to the plurality of pieces of copper foil, wherein the cleaning gas removes plume material from the laser beam path and removes the plume material from the plurality of pieces of copper foil. preventing oxidation of the copper foil piece;
f. The welding speed, clamping force and flow rate of the non-oxidizing cleaning gas are predetermined to provide a weld free of visible splatter and visible porosity;
A method of laser welding multiple pieces of metal together. 13. The method of claim 12,
The welding stand has an air gap under the piece of metal;
A method of laser welding multiple pieces of metal together. 13. The method of claim 12,
the metal is selected from the group consisting of aluminum, stainless steel, copper, aluminum-based metals, stainless steel-based metals, copper-based metals, aluminum alloys, stainless steel alloys and copper alloys;
A method of laser welding multiple pieces of metal together. 15. The method of claim 14,
The wavelength of the laser beam is about 450 nm,
A method of laser welding multiple pieces of metal together. 16. The method of claim 15,
The laser beam is not fluctuated, providing a fluctuating laser welding process.
A method of laser welding multiple pieces of metal together. 17. The method of claim 16,
the welding is selected from the welding group consisting of lap welding, butt welding, bead on plate weld and conduction mode welding;
A method of laser welding multiple pieces of metal together. 13. The method of claim 12,
The laser beam is not fluctuated, providing a fluctuating laser welding process.
A method of laser welding multiple pieces of metal together. 13. The method of claim 12,
the welding is selected from the welding group consisting of lap welding, butt welding, bead on plate weld and conduction mode welding;
A method of laser welding multiple pieces of metal together. A method of laser welding a plurality of copper foils together, comprising:
a. placing a plurality of pieces of copper foil on a welding stand, wherein the copper foil contains at least about 50% copper and the copper foil has a thickness of between about 80 μm and 500 μm;
b. applying a clamping force to the plurality of pieces of copper foil to clamp the pieces of foil together at a welding stand;
c. Directing a blue laser beam along a laser beam path at a plurality of pieces of copper foil, the laser beam having the following characteristics:
i. power of at least 600 watts,
ii. Beam parameter product of about 44 mm mrad or less,
iii. a spot size of about 200 μm to about 400 μm,
iv. an average strength of at least about 2.1 MW/cm ^{2 ,}
ⅴ. having a peak intensity of at least about 4.5 MW/cm ^{2 ;}
d. blue laser beam welding the plurality of metal pieces together at a welding speed of at least 10 m/min; and
e. providing a non-oxidizing beam cleaning gas in a space that follows a laser beam path in which the laser beam travels in free space from the optical element to the plurality of pieces of copper foil, wherein the cleaning gas removes plume material from the laser beam path and removes the plume material from the plurality of pieces of copper foil. preventing oxidation of the copper foil piece;
f. The welding speed, clamping force and flow rate of the non-oxidizing cleaning gas are predetermined to provide a weld free of visible splatter and visible porosity;
A method of laser welding a plurality of copper foils together.

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