CN113543921A

CN113543921A - Method and system for welding copper and other metals using blue laser

Info

Publication number: CN113543921A
Application number: CN201980093318.XA
Authority: CN
Inventors: 马克·泽迪克; 马修·芬纽夫; 罗伯特·D.·弗里茨; 珍-米歇尔·佩拉普拉特
Original assignee: Nuburu Inc
Current assignee: Nuburu Inc
Priority date: 2018-12-30
Filing date: 2019-12-30
Publication date: 2021-10-22
Also published as: CA3125591A1; EP3902648A1; KR20210106566A; EP3902648A4; WO2020142458A1; JP2022518132A

Abstract

A visible laser system and operation for welding materials together. A blue laser system can form a substantially perfect weld for copper-based materials. A blue laser system and operation for welding together electrically conductive elements, particularly thin electrically conductive elements, for energy storage equipment such as battery packs.

Description

Method and system for welding copper and other metals using blue laser

The application: (i) according to 35u.s.c. § 119(e) (1), the benefit of filing date of U.S. provisional application serial No. 62/786,511, filed 12, 30, 2018, the entire disclosure of which is incorporated herein by reference.

Background

Technical Field

The present invention relates to laser processing of materials, and in particular to laser joining of copper materials using laser beams having wavelengths of about 350nm to about 500nm and greater.

Laser welding of copper has proven to be very challenging due to high reflectivity, high thermal conductivity, and high heat capacity. Various methods have been developed to weld copper, from ultrasonic welding to infrared laser welding. However, these existing brazing methods have many drawbacks and limitations. For example, one market in which these limitations exist is in the high performance electronics field for the growing electric vehicle market. Higher speeds and better weld quality than available in the prior art are needed to produce high performance batteries and electronic products for the ever-increasing automotive market.

The high reflectivity of copper at this wavelength makes it difficult to couple power into the material to heat and weld it when using an infrared laser source at 1030 nm. One way to overcome the high reflectivity is to use a high power level (>1kW) IR laser to initiate a keyhole weld (keyhole weld) and then couple the power into the material. One of the problems with this welding method is that the vapor in the small hole can cause a micro-explosion that sprays molten copper onto the part being welded, or the micro-explosion can cause a hole that completely penetrates the part being welded. Therefore, researchers have to rely on rapidly modulating the laser power in an attempt to prevent these defects from occurring during the welding process. It has been found that the defect is a direct result of the process itself, when the laser attempts to weld copper, it initially heats it to the melting point, and then it quickly transitions to vaporizing the copper. Once the copper has vaporized, a pinhole forms and the laser coupling rises rapidly from the initial 5% to 100%; this transformation occurs so rapidly that the heat coupled in rapidly exceeds the heat required to weld the parts, resulting in the micro-explosion described.

Laser welding of copper with existing infrared laser methods and systems is challenging and problematic due to high reflectivity, high thermal conductivity, low vaporization point, and high heat capacity. Various methods of welding copper using infrared laser have been attempted, including combining an infrared laser with a green laser, oscillating the spot in the weld pool, operating in a vacuum, and modulating the laser at high frequency. While these methods are currently used in some brazing applications, they tend to have narrow process windows, uncontrolled spatter, and unpredictable variability in the weld, and often prove to be less than ideal or optimal. One of the more difficult brazing processes is how to weld the stacked copper foils to each other, and to the thicker bus bars; these operations cannot now be done reliably with IR lasers, nor in a manner that produces the weld quality desired by the manufacturer. Manufacturers therefore rely on ultrasonic welding to bond the foils together. These ultrasonic methods are also not optimal and are problematic. For example, with ultrasonic welding methods, the sonotrode can wear during production, resulting in process variability from incomplete welds to welds with residual debris. These defects limit the yield, the internal resistance of the battery, the energy density of the resulting battery, and in many cases the reliability of the battery.

Unless specifically provided otherwise, the term "copper-based material" shall be given its broadest possible meaning and includes copper, copper materials, copper metals, materials electroplated with copper, metallic materials containing at least about 10% by weight copper to 100% by weight copper, metals and alloys containing at least about 20% by weight copper to 100% by weight copper, metals and alloys containing at least about 10% by weight copper to 100% by weight copper, metals and alloys containing at least about 50% by weight copper to 100% by weight copper, metals and alloys containing at least about 70% by weight copper to 100% by weight copper, and metals and alloys containing at least about 90% by weight copper to 100% by weight copper.

The terms "laser machining", "laser machining of materials" and similar such terms, unless expressly provided otherwise, shall have the broadest possible meaning and include welding, brazing, melting, joining, annealing, softening, tacking, resurfacing (resurfacing), peening, heat treating, fusing, sealing, and stacking.

As used herein, unless otherwise expressly specified, "UV," "ultraviolet," "UV spectrum," and "UV portion of the spectrum" and similar terms shall have the broadest meaning and include light having wavelengths of from about 10nm to about 400nm and from 10nm to 400 nm.

As used herein, unless otherwise expressly specified, the terms "visible light," "visible spectrum," and "visible portion of the spectrum" and similar terms are intended to have the broadest meaning and include light having a wavelength of from about 380nm to about 750nm and from 400nm to 700 nm.

The terms "blue laser beam," "blue laser," and "blue" as used herein, unless otherwise expressly specified, shall have the broadest meaning and generally refer to a system that provides a laser beam, a laser source (e.g., a laser and diode laser) that provides (e.g., propagates) a laser beam, or light having a wavelength of from about 400nm to about 500 nm. The wavelength range of a typical blue laser is about 405-495 nm. The blue laser includes wavelengths of 450nm, about 450nm, 460nm, and about 470 nm. The bandwidth of the blue laser may be about 10pm (picometers) to about 10nm, about 5nm, about 10nm, and about 20nm, and values greater or less.

The terms "green laser beam," "green laser," and "green" as used herein, unless otherwise expressly specified, shall have the broadest meaning and generally refer to a system that provides a laser beam, a laser source (e.g., a laser and a diode laser) that provides (e.g., propagates) a laser beam, or light having a wavelength of about 500nm to about 575 nm. The green laser light includes wavelengths of 515nm, about 515nm, 532nm, about 532nm, 550nm, and about 550 nm. The bandwidth of the green laser may be about 10pm to 10nm, about 5nm, about 10nm, and about 20nm, and values greater or less.

As used herein, terms such as "at least," "greater than," also mean "not less than," unless expressly specified otherwise, i.e., such terms do not include lesser values unless expressly specified otherwise.

Room temperature as used herein is 25 ℃ unless explicitly stated otherwise. And, the standard temperature and pressure were 25 ℃ and 1 atmosphere. Unless otherwise expressly stated, all tests, test results, physical characteristics, and values related to temperature, pressure, or both are provided at standard temperature and pressure.

In general, as used herein, unless otherwise indicated, the terms "about" and "to" are intended to encompass a variance or range of ± 10%, experimental or instrumental errors associated with obtaining the stated values, and preferably include the larger of these.

Recitation of ranges of values, ranges, from about "x" to about "y," and similar such terms and amounts used herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein. They include, therefore, each item, feature, value, quantity, or amount falling within the scope. Unless otherwise indicated, each and every individual point within the scope of ranges used herein is incorporated into and is a part of this specification as if it were individually recited herein.

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

Disclosure of Invention

In metal welding, particularly copper metal welding for electronic components and batteries, there is an increasing demand for better weld quality, faster welding speeds, as well as higher repeatability, reliability, higher tolerances (tolerance), and robustness. Among these needs is the need for an improved method of brazing to itself and other metals; also, there is a need to address the problems associated with soldering stacked copper foils and soldering these stacked copper foils to thicker copper or aluminum parts. The present invention addresses these needs by providing improvements, articles, devices, processes, and the like, taught and disclosed herein.

Thus, it is proposedA system and method for laser welding together a plurality of sheets of copper foil is provided, the method comprising the steps of: positioning a plurality of copper foils in a soldering station; wherein the foil comprises at least about 50% copper; applying a clamping force to the plurality of copper foils to clamp the plurality of foils together in the soldering station; directing a blue laser beam along a laser beam path at the plurality of copper foils, wherein the laser beam has the following properties: (i) a power of at least 500 watts; (ii) a beam parameter product of about 44mmmrad (milliradians) and less; (iii) a spot size of about 400 μm and less; (iv) at least about 400kW/cm²Average intensity of (d); (v) at least about 800kW/cm²Peak intensity of (d); the blue laser beam is used for lap welding the plurality of copper foils together at a welding speed; and providing a non-oxidizing beam purge gas in space along the path of the laser beam, wherein the laser beam passes from the optical element to the plurality of copper foils in free space; wherein a purge gas removes plume material from the laser beam path and prevents oxidation of the plurality of copper foils; wherein the welding speed, clamping force, and flow rate of the non-oxidizing scavenging glass are predetermined to provide a lap weld free of visible spatter and visible porosity.

In addition, these welds, laser systems, and welding methods are provided having one or more of the following features: wherein the optical beam is a CW optical beam; wherein the light beam is a pulsed light beam; wherein the light beam has a wavelength of about 450 nm; wherein the optical element is selected from the group consisting of a lens, a fiber face (fiber face), and a window; wherein the scavenging gas is selected from argon, argon-CO₂Air, helium, and nitrogen; wherein the laser beam is free of wobble (wobbled), thereby providing a wobble-free laser welding process; wherein the plurality of copper foils have 10 to 50 foils; wherein the copper foil has a thickness of about 80 μm to 500 μm; wherein each of the plurality of copper foils has a thickness of about 80 to 500 μm; and wherein the welding speed is at least 10 m/min.

In addition, a system for laser welding a plurality of metal sheets together is providedAnd a method, the method comprising: positioning a plurality of pieces of metal in a welding station; applying a clamping force to the plurality of pieces of metal to clamp the pieces of metal together in the welding station; directing a blue laser beam along a laser beam path at the plurality of pieces of metal, wherein the laser beam has the following characteristics: (i) a power of at least 500 watts; (ii) a beam parameter product of about 44mmmrad and less; (iii) a spot size of about 400 μm or less; (iv) at least about 400kW/cm²Average intensity of (d); (v) at least about 800kW/cm²Peak intensity of (d); and, the blue laser beam welds the plurality of pieces of metal together at a welding speed; and providing a non-oxidizing beam purge gas in space along the path of the laser beam, wherein the laser beam passes from the optical element to the plurality of copper foils in free space; wherein a purge gas removes plume from the laser beam path and prevents oxidation of the plurality of copper foils; wherein the welding speed, clamping force, and flow rate of the non-oxidizing scavenging glass are predetermined to provide a weld free of visible spatter and visible porosity.

Still further, these welds, laser systems, and welding methods are provided with one or more of the following features: wherein the welding table has an air gap below the plurality of pieces of metal; wherein 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; wherein the laser beam has a wavelength of about 450 nm; wherein the laser beam is free of wobble, thereby providing a wobble-free laser welding process; and wherein the weld is selected from the group of welds consisting of a lap weld, a butt weld, a bead on plate weld, and a conduction mode weld.

Further, a system and method for laser welding together a plurality of copper foils is provided, the method comprising: positioning a plurality of copper foils in a soldering station; wherein the foil comprises at least about 50% copper; wherein the copper foil has a thickness of about 80 to 500 μm; applying a clamping force to the plurality of copper foils to hold a plurality of foils in the soldering stationClamping together; directing a blue laser beam along a laser beam path at the plurality of copper foils, wherein the laser beam has the following characteristics: (i) a power of at least 600 watts; (ii) a beam parameter product of about 44mmmrad and less; (iii) a spot size of about 200 μm to about 400 μm; (iv) at least about 2.1MW/cm²Average intensity of (d); (v) approaching at least about 4.5MW/cm²Peak intensity of (d); welding the plurality of copper foils together by a blue laser beam at a welding speed of at least 10 m/min; and providing a non-oxidizing beam purge gas in space along the path of the laser beam, wherein the laser beam passes from the optical element to the plurality of copper foils in free space; wherein a purge gas removes plume from the laser beam path and prevents oxidation of the plurality of copper foils; wherein the welding speed, clamping force, and flow rate of the non-oxidizing scavenging glass are predetermined to provide a weld with no visible spatter and no 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; wherein the workpiece comprises placing a first piece of copper-based material in contact with a second piece of copper material; 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; wherein the weld comprises a HAZ and a resolidified zone; wherein the microstructure of the copper-based material, the HAZ, and the resolidified region are the same.

These welds, systems, and methods are further provided with one or more of the following systems; wherein the same microstructure does not exhibit a discernable difference in the weld indicating a weak weld; wherein the same microstructure comprises similarly sized crystal growth regions; wherein the weld joint is formed by welding in a conduction mode; wherein the weld is formed by keyhole mode welding; wherein the first and second pieces have a thickness of about 10 μm to about 500 μm; wherein the first piece comprises a plurality of layers of copper foil; wherein the first piece is copper metal; wherein the first piece is a copper alloy having about 10 to about 95 weight percent copper; wherein saidThe power density of the laser beam is less than 800kW/cm²The focused light spot is guided to the workpiece; wherein the laser beam has a power density of less than 500kW/cm²The focused light spot is guided to the workpiece; wherein the laser beam as a power density is about 100kW/cm²To about 800kW/cm²The focused light spot is guided to the workpiece; wherein the laser beam has a power density of more than 100kW/cm²The focused light spot is guided to the workpiece; wherein the power of the laser beam is less than 500W; wherein the power of the laser beam is less than 275W; wherein the power of the laser beam is less than 150W; wherein the laser beam has a power in a range of 150W to about 750W; wherein the laser beam has a power in a range of about 200W to about 500W; wherein the laser beam is directed at the workpiece as a focused spot having a spot size of about 50 μm to about 250 μm; wherein the laser beam has a wavelength of about 405nm to about 500 nm; the weld formed therein is free of spatter; and wherein the laser does not vaporize the workpiece.

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; wherein the workpiece comprises placing a first piece of copper-based material in contact with a second piece of copper material; 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; wherein the weld comprises a HAZ and a resolidified zone; wherein the hardness range of the HAZ is within the hardness range of the copper-based material.

Further, these welds, systems, and methods are also provided having one or more of the following features: wherein the resolidified region has a hardness in a range of a hardness of the copper-based material; wherein the copper-based material, the HAZ, and the resolidified region have the same microstructure; wherein the same microstructure does not exhibit a discernable difference in the weld indicating a weak weld; wherein the same microstructure does not exhibit a discernable difference in the weld indicating a weak weld; and wherein the same microstructure comprises similarly sized crystal growth regions.

There is further provided a method of forming a perfect weld in a copper-based material, the method comprising: placing a workpiece in a laser system; wherein the workpiece comprises placing a first piece of copper-based material in contact with a second piece of copper material; 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; wherein the weld comprises a HAZ and a resolidified zone; wherein the resolidified region has a hardness within a hardness range of the copper-based material.

Further, laser welding of copper with blue light in the wavelength range of 405nm to 500nm is provided, as well as welds and products produced by the welding.

Further, these welds, methods, and systems are provided that include one or more of the following features: wherein copper is soldered in a conductive mode; welding copper in a conductive mode without bath vaporization during welding; welding copper in a conduction mode to generate a microstructure similar to the base material, wherein the size of a crystal growth area of the microstructure is similar to that of the base material; welding copper in a conduction mode, creating a microstructure similar to the parent metal in the Heat Affected Zone (HAZ); welding copper in a conduction mode, creating a microstructure similar to the base material in a weld bead (weld bead); welding copper in a conduction mode to generate hardness similar to that of the base metal in a heat affected zone; welding copper in a conductive mode, producing a hardness in the weld bead similar to that of the parent metal; welding copper, wherein the microstructure in the weld bead is different from the microstructure of the base metal; welding copper, wherein the microstructure in the HAZ is similar to the parent metal.

Further, these welds, methods, and systems are provided that include one or more of the following features: welding copper in a keyhole mode; welding copper in a keyhole mode, wherein little spatter is generated in the welding process, and the surface of the copper after welding has little or no spatter; at 500kW/cm²Or higher power density and welding speed that can keep the keyhole open; at 400kW/cm²Or higher power density and welding speed that can keep the keyhole open; at 100kW/cm²Or higher power density and a welding speed fast enough to prevent switching to keyhole welding mode; preheating is carried out during copper welding so as to improve the penetration depth in the welding process; accompanying Ar-CO in copper welding₂Assistance ofA gas; associated with Ar-H in copper welding₂An auxiliary gas; carrying out Ar auxiliary gas during copper welding; the copper is welded with air; he auxiliary gas is accompanied when copper is welded; accompanying N in copper soldering₂An auxiliary gas; the copper is soldered with an auxiliary gas.

Further, these welds, methods, and systems are provided that include one or more of the following features: the laser power is modulated from 1Hz to 1 kHz; the laser power is modulated from 1kHz to 50 kHz; keeping the aperture open using an elongated blue laser spot; using a robot to rapidly move the light spot in a circular, oscillating or elliptical oscillating motion; oscillating the spot parallel to the weld direction using a mirror mounted on a galvanometer; swinging the light spot perpendicular to the direction of the weld seam by using a mirror mounted on a galvanometer; and the spot is moved rapidly in a circular, oscillating or elliptical oscillating motion using a pair of mirrors mounted on a pair of galvanometers.

There is additionally provided a method of forming a keyhole weld in a copper-based material, the method comprising: placing a workpiece in a laser system; wherein the workpiece comprises placing a first piece of copper-based material in contact with a second piece of copper material; 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; wherein the weld includes a HAZ and a resolidified zone.

Further, these welds, methods, and systems are provided that include one or more of the following features: wherein, for the small hole welding seam, the laser power is less than 1000 kW; wherein the laser power is less than 500kW for the keyhole weld; wherein for a keyhole weld, the laser power is less than 300 kW; including an elongated laser beam to inhibit splattering from the pinhole; includes modulating laser power to suppress splatter from the pinhole; including rapid scanning of the beam during keyhole mode of welding to suppress spatter; including rapid reduction of laser power after automatic or manual start of welding; including the use of low gas pressures to reduce entrained gas and spatter during welding; comprises applying a protective gas; comprises applying a gas selected from He, Ar, N₂A shielding gas of the group; comprises applying a material selected from the group consisting of Ar-H₂、N₂、N₂-H₂A shielding gas mixture of the group; and, applying a shielding gas and adding hydrogen to the shielding gas to remove the oxide layer and promote wetting of the weld.

Drawings

FIG. 1 is a photograph of an example of a splash-free conduction mode weld of copper according to the present invention.

FIG. 2 is a photograph of an embodiment of a keyhole weld on copper in accordance with the present invention.

FIG. 3 is a graph showing penetration depth versus velocity for an embodiment of the present invention for copper having a thickness of 127 μm, wherein the copper is fully penetrated at a velocity of up to 8 m/min.

FIG. 4 is a graph showing penetration depth versus velocity for an embodiment of the present invention for copper having a thickness of 254 μm, wherein the copper is fully penetrated at a velocity of up to 0.5 to 0.75 m/min.

FIG. 5 is a graph showing penetration depth versus velocity for an embodiment of the present invention.

FIG. 6 is a graph showing penetration depth at several different speeds for an embodiment of the present invention.

FIG. 7 is a photograph showing an annotation of an embodiment of a conduction mode weld on a 70 μm thick copper foil according to the present invention.

FIG. 8 is a photograph of an annotation of an embodiment of a keyhole mode weld cross-section in accordance with the present invention.

Fig. 9 is an absorption curve of various metals, showing the difference in absorption between IR laser and visible laser.

FIG. 10 is a schematic view of an embodiment of a conduction mode weld extending into a material in accordance with the present invention.

FIG. 11 is a schematic view of an embodiment of a keyhole weld extending into a material in accordance with the present invention.

Fig. 12 is a perspective view of an embodiment of a part holder for laser welding according to the present invention.

Fig. 12A is a cross-sectional view of the parts holder of fig. 12.

FIG. 13 is a perspective view of an embodiment of a part holder for holding thin parts to form a lap weld according to the present invention.

Fig. 13A is a cross-sectional view of the parts holder of fig. 13.

FIG. 14 is a photograph of an embodiment of a weld overlay of a conduction mode weld according to the present invention.

Fig. 15 is a photograph of an embodiment of a stack of foils welded using a conduction welding mode according to the present invention.

FIG. 16 is a photograph of an example of weld overlay of a keyhole mode weld according to the present invention.

Fig. 17 is a photograph of an embodiment of a stack of 40 copper foils for aperture mode soldering according to the present invention.

FIG. 18 is a graph of penetration depth in copper for various power level and various speed embodiments in accordance with the present invention.

Fig. 19 is a schematic diagram of an embodiment of a 150-watt blue laser system for performing an embodiment of the present laser welding method in accordance with the present invention.

Fig. 20 is a schematic ray trace diagram of an embodiment of a 300 watt blue laser system fabricated using two 150 watt blue laser systems in accordance with the present invention.

FIG. 21 is a schematic ray trace diagram of an embodiment of an 800W blue laser system fabricated using four 150W blue laser systems in accordance with the present invention.

FIG. 22 is a graph of beam defocus (beam focal) radius (microns (μm)) versus focus displacement (μm) for a circular aperture containing 95% power around a 100mm focal length lens at 600W, in accordance with the present invention.

FIG. 23 is a graph of an example of a build-up welding (BOP) test of copper 110, showing the relationship between penetration (. mu.m) and velocity m/min, according to the present invention.

FIG. 24 is a graph of an example of a butt weld test of copper 110 showing the relationship between penetration (. mu.m) and velocity m/min according to the present invention.

FIG. 25 is a graph of an embodiment of a conduction mode weld according to the present invention illustrating the effect of plate thickness on penetration depth.

FIG. 26 is a diagram of an embodiment of a BOP test of aluminum 1100, showing the relationship between penetration (. mu.m) and velocity m/min, in accordance with the present invention.

FIG. 27 is a graph of an example of a butt weld test of aluminum 110 showing the relationship between penetration (. mu.m) and velocity m/min according to the present invention.

FIG. 28 is a graph of an example of a BOP test of stainless steel 304, showing the relationship between penetration (. mu.m) and velocity m/min, according to the present invention.

Fig. 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 zone.

FIG. 30 is a photograph of an example of 1.016mm thick copper with minimal porosity and spatter welded at 1.1m/min in accordance with the present invention.

FIG. 31 shows a graph of the relationship between penetration depth (μm) and velocity (m/min) for an embodiment of a BOP test of copper 110 soldered with 600 watts and a 200 μm spot size, in accordance with the present invention.

Fig. 32 is a photograph of an example of a small hole lap weld of four pieces of stainless steel 304 according to the present invention.

Fig. 33 is a diagram of an example of a lap weld test performed on multiple stacks of copper 110 foils in accordance with the present invention.

FIG. 34 is a photograph of an embodiment of a multi-stack 40, 10mm thick copper 110 foil laser welded with a 500 watt, 400 μm spot blue in accordance with the present invention.

Detailed Description

The present invention relates generally 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 of these metals. In general, the invention also relates to methods of applying the laser beam, beam size, beam power, methods of securing parts, and methods of introducing shielding gas to assist the welding process, including preventing oxidation of the parts and management of the plume to prevent the plume from interfering with the laser beam.

In one embodiment, the present invention provides high quality welds, high welding speeds, and both for copper-based materials in many areas, including electronic components, and further including batteries. In one embodiment, the present invention provides high quality welds, high welding speeds, and both for copper-based materials used for automotive components, including automotive electronic components, including batteries.

In one embodiment, the present invention provides high quality welds, high welding speeds, and both for stainless steel based materials (including electronic components, and further including batteries) in many areas. In one embodiment, the present invention provides high quality welds, high welding speeds, and both for stainless steel based materials used for automotive components, including automotive electronic components, including batteries.

In one embodiment, the present invention provides high quality welds, high welding speeds, and both for aluminum-based materials in many areas, including for electronic components, and further including batteries. In one embodiment, the present invention provides high quality welds, high welding speeds, and both for aluminum-based materials used for automotive components, including automotive electronic components, including batteries.

In one embodiment of the present invention, a high power blue laser source (e.g., -450 nm) solves the problems of existing copper bonding techniques. The blue laser source provides a blue laser beam at which the absorption of copper is about 65%, enabling efficient coupling of laser power into the material at all power levels. The system and method provide stable welding in a number of welding techniques, including conduction and keyhole welding modes. The system and method minimizes, reduces, and preferably eliminates evaporation, spatter, micro-explosions, and combinations and variations of these.

In one embodiment, blue laser welding of copper at spot sizes of about 200 μm achieves stable, low spatter welding over all power ranges at power levels from 150 watts to 275 watts. In one embodiment of the welding system and method, the weld is in a conduction mode, and the resulting weld has a microstructure similar to the parent material.

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

Turning to fig. 6, penetration depth versus power is shown for different welding speeds. Welding was performed using a system of the type described in example 1. On 500 μm copper, a weld was made with a laser beam at 275W power, without assist gas.

The photograph of fig. 7 shows a conduction mode weld on a 70 μm thick copper foil, showing the microstructure through the HAZ and the weld. Welds were made using the parameters described in example 1. The penetration depth of each sample was first determined by cross-section and then the samples were etched to reveal the microstructure of the weld and the HAZ region. In addition, when one of the samples was cut, the Vickers hardness of the entire base material ranged from 133-141HV, the weld bead was about 135HV, and the HAZ ranged from 118-132 HV. The conclusion is that the hardness of the parent material, HAZ and weld bead (e.g., resolidified area) is close to the original material. In addition, the microstructures of the conduction mode bead, HAZ, and base material are very similar, with slight differences in microstructure. When welded using a laser or any other means, welds with these characteristics have never been observed in copper before. This weld quality is shown in fig. 7, where the sample is sectioned transversely to the weld seam and etched to reveal the microstructure.

Accordingly, embodiments of the present invention include methods of welding copper-based materials to obtain the following welds, as well as the resulting welds themselves. These methods and welds would include welding two or more copper-based materials together such that the hardness of the materials in the area around the weld is as follows (as measured by recognized and established hardness tests, such as vickers hardness, ASTM tests, and the like): when the bead hardness is within the base material hardness range, the bead hardness is within 1% of the base material hardness, the bead hardness (e.g., resolidified area) is within 5% of the base material hardness, and the bead hardness is within 10% of the base material hardness. These methods and welds would include welding two or more copper-based materials together such that the hardness of the materials in the area around the weld is as follows (as measured by recognized and established hardness tests, such as vickers hardness, ASTM tests, and the like): when the HAZ hardness is within the base material hardness range, 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. These methods and welds will include welding together two or more copper-based materials such that the microstructures of the parent metal, the weld bead (e.g., the resolidified area), and the HAZ are the same in the area around the weld, i.e., there is no discernable difference in the microstructure that indicates or indicates the presence of a weak point in the welded structure or the presence of a weak point in the weld area.

Turning to fig. 8, it is the microstructure observed when a sample of copper plate having a thickness of 500 μm is operated in keyhole welding mode. During keyhole welding, the steam plume is clearly visible and molten copper is slowly sprayed along the length of the weld. There was no evidence of any spatter from the welding process during or after welding, as is typically observed when using IR laser welding. This demonstrates a stable, well-controlled keyhole process that is suitable for creating high quality welds on electronic components. Can be reduced to 800kW/cm²And lower power density, results in a keyhole mode weld cross-section (of the type shown in fig. 8) of very high quality and uniformity. Zone of resolidification [1]–[2]442 to 301 μm, HAZ 2]It was 1314 μm.

Embodiments of the present invention relate to methods, apparatus, and systems for joining copper to copper or other materials using a visible laser system to achieve benefits including an effective heat transfer rate to the copper material; a stable molten bath; and in particular in the conductive or keyhole mode of soldering. Copper has high absorption in the blue wavelength range, as shown in fig. 9. The presently preferred blue laser beam and laser beam system and method couple laser power into copper in a very efficient manner. The present laser beam system and method heats the parent material (the material to be welded, e.g., copper) faster than the heat is conducted away from the laser spot. This provides efficient and excellent weld properties for conduction mode laser welding, i.e., the material in the laser beam is rapidly heated to and maintained at the melting point by the continuous laser beam, thereby forming a stable weld bead. In current conduction mode welding, the metal melts rapidly, but the penetration depth of the weld is determined by heat diffusion into the material and progresses into the material in a spherical shape. This is shown in fig. 10. Fig. 10 shows a schematic diagram of an embodiment of a conduction mode weld 1000, with the direction of the weld shown with arrow 1004. A laser beam 1001 (e.g., blue wavelength) is focused onto and maintained on weld puddle 1002. Behind the weld pool 1002 is solid weld material 1003. A base metal (e.g., copper metal or alloy) is below the weld. A shielding gas flow 1005 is also used.

One embodiment of the present invention relates to the use of a blue laser system for keyhole welding of copper. These methods and systems open new possibilities for soldering thick copper materials as well as stacked copper foils (including thick stacks). This keyhole mode of welding occurs when the laser energy is absorbed so quickly as to melt and vaporize the material being welded. The evaporated metal creates a high pressure in the welded metal, opening a hole or capillary where the laser beam can travel and be absorbed. Once keyhole mode is activated, deep penetration welding can be achieved. The absorption of the laser beam changed from 65% of the initial absorption of the blue laser in copper to 100% absorption in the aperture. The high absorption can be attributed to multiple reflections off the walls of the pores where the laser beam undergoes continuous absorption. When combined with the high absorption of copper at blue wavelengths, the power required to initiate and maintain the pinhole is much lower than when using an IR laser. Turning to FIG. 11, FIG. 11 shows a schematic view of an embodiment of a keyhole mode weld 2000 with the weld direction shown by arrow 2007. The pores 2006 contain a metal/vapor plasma. The blue laser beam 2002 creates a plasma cloud 2002, a weld pool 2003, and solid weld metal 2004. A shielding gas flow 2005 is also used.

Compare the keyhole weld of FIG. 11 with the conduction mode weld of FIG. 10. The walls of the final weld resolidified zone in keyhole welds are more perpendicular through the part or parent material than in conduction mode welds.

Preferably, the high power laser beams (e.g., visible, green, and blue laser beams) used in embodiments of the present system and method are focused or have the ability to be focused by optics in the system and have a power of at least 10W or higher; the focusing is to a spot size of about 50 μm.The power of the laser beam (including the blue laser beam) may be 10W, 20W, 50W, 100W, 10-50W, 100-. The spot size (longest cross-sectional distance, diameter for a circle) of these powers and laser beams may be about 20 μm to about 4mm, less than about 3mm, less than about 2mm, about 20 μm to about 1mm, 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, with larger and smaller spots contemplated, and all sizes within these ranges. The power density of the laser beam spot may be about 50kW/cm²To 5MW/cm²About 100kW/cm²To 4.5MW/cm²About 100kW/cm²To 1000kW/cm²About 500kW/cm²To 2MW/cm²Greater than about 50kW/cm²Greater than about 100kW/cm²Greater than about 500kW/cm²Greater than about 1000kW/cm²Greater than about 2000kW/cm²And higher and lower power densities, and all power densities within these ranges. The copper is welded at speeds from about 0.1 mm/sec to about 10 mm/sec, with slower and faster welding speeds, and all speeds within these ranges, depending on the conditions. The speed depends on the thickness of the material to be soldered, so the speed per unit thickness (in mm) mm/s/thickness can be 0.1/s to 1000/s for 10 μm to 1mm thick copper.

Embodiments of the present method and system may use one, two, three, or more laser beams to form the weld. The laser beam may be focused on the same general area to initiate the weld. The laser beam spots may overlap or may coincide. A plurality of laser beams may be used simultaneously; and coincide and be simultaneous. A single laser beam may be used to initiate the weld and then a second laser beam may be added. Multiple laser beams may be used to initiate the weld and then fewer beams (e.g., a single beam) may be used to continue the weld. The laser beams in the plurality of laser beams may be of 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 of these. The use of additional laser beams may be simultaneous or sequential. Combinations and variations of these embodiments using a plurality of laser beams may also be used. The use of multiple laser beams can suppress spatter from the weld and can do so in the deep fusion welding method.

In the examples, hydrogen (H)₂) May be mixed with an inert gas to remove the oxide layer from the substrate during the soldering process. Hydrogen gas flows through the weld area. Hydrogen also promotes wetting of the weld. Hydrogen may be added to or mixed with the shielding gas and applied to the weld as part of the shielding gas. These mixtures will include, for example, Ar-H₂、He-H₂、N₂-H₂。

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

Method for conducting mode welding of copper, copper alloys and other metals with blue laser system

When applied to copper-based materials, the present system overcomes the problems and difficulties associated with IR welding. The high absorption of copper (65%) at the blue wavelength of the current laser beam and beam spot overcomes the thermal diffusivity of the material and can do so at relatively low power levels (about 150 watts). The interaction of the present blue laser beam with copper allows the copper to easily reach its melting point, allowing for a wide processing window.

In one embodiment, by using a part holder or fixture, a stable conduction mode weld is performed and a high quality weld is obtained at a stable and fast rate.

The welding fixture is used to secure the materials to be welded in place during thermal transients caused by the laser beam in the part. The clamps of fig. 12 and 12A are perspective and cross-sectional views, respectively, of an embodiment of a linear section (linear section) of a welding jaw that may be used to lap, butt, or even edge weld. The welding fixture 4000 has a floor or support structure 4002. Attached to the base plate 4002 are two clamp members or pinch pieces 4001. The pressing piece 4001 has a tab that rests on the surface of the base plate 4002 and a free end that contacts and secures the workpieces to be welded. In the base plate 4002, there is a slot 4003, for example 2mm wide by x2mm deep, at the area between the free ends of the pressure piece 4001. Four bolts, such as 4004, adjust, tighten, and secure the clamp to the workpiece (other types of adjustment fasteners may also be used) to hold or secure the workpiece.

The preferred material for the fixture is a low thermal conductivity material, such as stainless steel, because it is sufficiently rigid to apply the clamping pressure required to hold the parts in place during welding. In embodiments, the clamp, the base plate, and both may have an insulating property effect on the workpiece during the welding process. The use of a material with a low thermal conductivity for the fixture may prevent, minimize and reduce rapid conduction of heat deposited into the part away by the fixture itself. This provides an additional benefit when soldering highly thermally conductive materials such as copper. Therefore, the material selected for the jaws, the width of the jaws, 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. Turning to fig. 14, a cross section (after etching) is shown where a conduction mode weld can be identified by the circular shape 6001 of the weld bead in the substrate (e.g., in the workpiece). The weld has this shape due to the isotropic nature of the heat transfer process of copper or any other material when heat is applied to the top surface of the part.

In a preferred embodiment, the floor 4002 of the fixture 4000 is constructed of stainless steel, and a 2mm wide gap 4003 is cut in the floor to be positioned directly beneath the weld area and filled with an inert gas, such as argon, helium, or nitrogen (as a cover or shielding gas), 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 distance of 2mm from the edge of the gap 4003 in the base plate 4002. Thus, in this embodiment, a 6mm wide area of the part to be welded is open to the laser beam (recognizing that the laser beam will be a slight distance from the clamp). This positioning of the clamp allows easy access of the laser beam to the surface and tight clamping of the part. This type of clamp is the preferred method of butt welding together two foils or sheets of copper, varying in thickness from 50 μm to several millimeters. The fixture is also suitable for lap welding two thicker copper plates (ranging from 200 μm to several millimeters). The magnitude of the clamping pressure is very important and depending on the magnitude of the laser power, the welding speed, the thickness of the part and the type of weld being made, the torque of the clamping bolt may reach 0.05 newton-meters (Nm), up to 3Nm or more (for thicker materials). The torque value is highly dependent on the bolt size, the thread engagement and the distance from the bolt center to the clamping point.

In one embodiment, high quality and good welds are obtained by providing sufficient clamping force to prevent the parts from moving during the welding process while minimizing parasitic heat loss from the fixture itself. It should be understood that the embodiment of the fixture of fig. 12 and 12A represents a cross-section of a straight portion (straight portion) of a welding fixture, and may be designed as any arbitrary two-dimensional path (e.g., -S-, -C-, -W-, etc.) to weld any type of shape together. In another embodiment, the fixture may be preheated or heated during the welding process to increase the speed or penetration depth of the weld while reducing parasitic heat loss from the fixture. The welding speed, penetration depth and quality can be improved by one to two times (a factor or two) or more when the fixture is heated to 100 c. The shield gas on the top side of the weld is delivered longitudinally from the front of the weld travel direction to the back of the weld travel direction as shown in fig. 10. As shown in fig. 14, a conduction mode weld was deposited on a copper plate having a thickness of 254 μm using the jig 4000. The frozen-in pattern of the weld bead shows a typical spherical fusion pattern of such a weld.

Lap welding two parts using a conduction mode welding process requires placing the parts and maintaining intimate contact. The two parts (collectively referred to as the workpiece) may be placed in a fixture, preferably of the type shown in fig. 13 and 13A; fig. 13 and 13A are a perspective view and a sectional view of the jig 5000, respectively. The clamp 5000 has a base plate 5003 and two clamp jaws 5002. The clamp has four slots (e.g., 5010) that correspond to the hold-down bolts (e.g., 5001). In this way, the position of the clamps relative to the workpiece, the position of the clamps relative to each other, and the magnitude of the clamping or pressing force can be adjusted and fixed. The clamps may have magnets to assist in their positioning and securing. The clamp 5002 has an internal passage for delivering a shielding gas, e.g., 5004. The passage 5004 is in fluid communication with a shielding gas outlet, e.g., 5005. The shielding gas outlet and the shielding gas channel form a shielding gas delivery system in the clamp. Thus, the gas delivery system is and passes through an array 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 can sink on the parts, displacing oxygen and preventing oxidation of the top surface. A small amount of hydrogen may be added to the inert gas to promote the removal of oxide layers from the part and to promote wetting of the part during the melting process.

There is also an insert 5006 for forcing individual foils in a stack of foils to hold and maintain contact with each other in the stack. The inserts 5006 can stretch and force the foils into intimate and uniform contact with each other. In the embodiment of fig. 13 and 13A, insert 5006 is an inverted V-shape. It may be curved, ridged or otherwise shaped, depending on the thickness of the stack of foils, as well as the individual foils. Additionally, in the embodiment of fig. 13 and 13A, the insert 5006 is adjacent to the clamp 5002 but not covered by the clamp 5002. The insert may be removable from the ends of the jaws, or one or both of the jaws may partially cover the insert.

In a preferred embodiment, the base plate 5000 is made of stainless steel, as is the clamp 5002. The fixing means may be made of ceramic or heat insulating material. The bump 5006 provides pressure from the bottom of the weld to keep the overlapping plates (two, three, ten, etc.) in intimate contact. In this embodiment, the means for shielding gas is built into the clamp (2) in the form of a row of holes along the length of the clamp, which holes deliver an inert gas, such as argon, helium or nitrogen. Argon is the preferred gas because it is heavier than air and can sink on the parts, displacing oxygen and preventing oxidation of the top surface. The insert boss 5006 in the base plate 5003 may also have a series of channels, holes or grooves to deliver a cover or shielding gas to the back of the weld to prevent oxidation. As shown, the clamp 5000 represents a cross section of a straight portion of a weld and may be designed as any two-dimensional path for welding any shape together. In this application, the torque value of the bolt may be important, depending on the nature of the workpiece; parts may not remain in contact when the torque value is too low (e.g., 0.1Nm), too high a torque value >1Nm and parasitic heat transfer reduce the efficiency of the welding process, reducing penetration and bead width.

Method for welding copper, copper alloys and other metals using blue laser system in keyhole mode

The blue laser has a much higher absorption level than the IR laser (65%) and can initiate a keyhole weld at a relatively low power level of 275 Watts (compared to 2,000 to 3,000 Watts required for the IR system to initiate the keyhole welding process after start-up, the IR system will further face problems of run away and the like). Since the blue laser system initiates pinhole mode, the absorption increases and it is now not a runaway process because it increases from 65% to about 90% and 100%. Thus, the present keyhole welding process has a very different absorption time profile than the IR. The absorption time curve from the start to the advancing weld for this blue keyhole welding process is 35% or less. The use of existing laser welding systems enables the blue laser welding process to be initiated and transitioned to a continuous weld without the need to rapidly change the power level or welding speed of the laser to prevent spatter as is required when using an IR laser. High speed video at the beginning of keyhole welding using a blue laser shows a stable process, capable of welding multiple layers of copper foil and board with little to no spatter ejected from the keyhole. The cross-sections of the two-keyhole welded samples are shown in fig. 16 and 17, where the material freeze pattern is significantly different from the shape of the conduction mode welded sample shown in fig. 14. The formation of a frozen pattern of material normal to the surface of the material, as shown in fig. 16 and 17, is different from a conduction mode weld because heat transfer occurs along the entire length of the aperture through the surface of the part and extending to the depth of the final weld. This is in contrast to conduction mode welds, where all of the laser energy is deposited on the surface of the material.

Similar to the conduction mode welding process, the keyhole welding process requires that the part be secured in a fixture to prevent any movement during welding. Keyhole mode is commonly used for lap weld configurations where a keyhole penetrates a part to weld a stack of two or more parts together (e.g., as shown in fig. 17).

The laser system of FIG. 20 produced a 275W blue laser beam with a spot power density of 800kW/cm². The laser system of fig. 20 has a first laser module 1201 and a second laser module 1202, the laser beam exiting the laser modules and following a laser beam path as shown by ray trace 1200. The laser beam passes through turning

mirrors

1203, 1205 and through a focusing lens arrangement 1205 having a 100mm focusing lens and a 100mm protective window. The focusing lens in configuration 1205 produces a spot 1250.

The laser system shown in fig. 21 can be used to create a 400 μm spot or a 200 μm spot. The laser system of fig. 21 consists of 4

laser modules

1301, 1302, 1303, 1304. Each of the laser modules may be of the type disclosed and taught in U.S. 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, wherein the composite beam from each of the

laser diode subassemblies

210, 210a, 201b, 210c propagates to a patterned mirror, e.g. 225, which serves to redirect and combine the beams from the four laser diode subassemblies into a single beam. The polarization beam folding assembly 227 doubles the beam in half on the slow axis to double the brightness of the composite laser diode beam. A telescope assembly (tele assembly)228 enlarges the combined laser beam in the slow axis or compresses the fast axis to allow a smaller lens to be used. The telescope 228 shown in this embodiment enlarges 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 a factor of 2.6. If the telescope assembly compresses the fast axis, it will be a 2-fold telescope to reduce the fast axis from 22mm height (total composite beam) to 11 mm height, resulting in an 11 mm by 11 mm composite beam. This is a preferred embodiment because of the lower cost. The aspheric lens 229 focuses the combined beam.

It will be appreciated that at 500 watt and 200 μm spots, the power density is>1.6MW/cm²This is substantially above the keyhole weld threshold at that wavelength. At this power density, even a blue laser may generate a fly in the weldSplashing and blowholes. However, since absorption is well controlled, the ability to suppress, control or eliminate spatter is possible. A first method of suppressing spatter is to reduce the power level once the spattering process has started, while keeping the welding speed constant. A second method of suppressing spatter is to elongate the weld pool so that the shielding gas and vaporized metal are expelled from the keyhole, thereby producing a spatter-free, defect-free weld. A third method of suppressing the spatter is to oscillate the blue laser beam using a set of mirrors or a robot mounted on a set of galvanometer motors. A fourth method of suppressing spatter is to reduce the pressure of the welding environment, including the use of a vacuum. Finally, a fifth method to suppress spatter is to modulate the laser beam power to be in the range of 1Hz to 1kHz or up to 50 kHz. Preferably, the welding parameters are optimized to minimize spatter in the process.

Embodiments of the present invention generally relate to laser processing of materials by matching a preselected laser beam wavelength to the material to be processed to have a high or increased level of absorptivity of the material, and in particular laser welding the material using a laser beam for which the material has a high absorptivity.

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

Blue laser welding materials (e.g., gold, copper, brass, silver, aluminum, nickel-plated copper, stainless steel, and other materials), plated materials, and alloys with wavelengths of, for example, about 405 to about 495nm are preferably used because of the high absorptivity of the materials at room temperature, e.g., greater than about 50% absorptivity. One of the several advantages of the present invention is the ability to pre-select a wavelength laser beam (e.g., a blue laser beam) that better couples laser energy into the material during laser operations (e.g., welding processes). By better coupling the laser energy to the material being welded, the probability of a runaway process can be greatly reduced and preferably eliminated. Better coupling of laser energy also allows the use of lower power lasers, thus saving costs. Better coupling also provides better control, higher tolerances, and thus better weld reproducibility. These functions, which are not available in IR laser and IR laser welding operations, are very important for other products, including products in the electronics and power storage fields, among others.

In one embodiment, a blue laser operating in CW mode is used. In many applications, CW operation may be preferred over pulsed lasers because it enables rapid and complete modulation of the laser output and control of the welding process in a feedback loop, resulting in a highly repeatable process with optimal mechanical and electrical characteristics.

One embodiment of the invention relates to laser machining of one, two or more components. The components may be made of any type of material that absorbs the laser beam, such as laser beam energy, plastic, metal, composite materials, amorphous materials, and other types of materials. In one embodiment, laser machining involves welding two metal parts together. In one embodiment, laser machining involves welding two metal parts together.

In one embodiment, tools, systems, and methods are provided in which the laser welding operation is selected from the group consisting of autogenous welding, laser hybrid welding, keyhole welding, lap welding, fillet welding, butt welding, and non-autogenous welding.

Laser welding techniques can be used in many different situations, particularly where welding is required to form an electrical connection, particularly in power storage devices such as batteries. Generally, embodiments of the present laser welding operation and system include visible wavelengths, preferably blue wavelengths, and the laser may be autogenous (autogenous), meaning that only base materials are used and are common in keyhole welding, conduction welding, lap welding, fillet welding, and butt welding. Laser welding may be non-autogenous (non-autogenous) in which filler material is added to the weld puddle to "fill" the gap or form a raised weld bead in the weld bead for strength. Laser welding techniques will 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 weld, where an electrical current is used in conjunction with the laser beam to provide faster feeding of the filler material. Laser hybrid welding is by definition non-autogenous welding.

Preferably, in some embodiments, an active weld monitor (e.g., a camera) may be used to check weld quality on the fly. These monitors may include, for example, X-ray inspection and ultrasound inspection systems. In addition, the system characteristics and the operation characteristics can be sufficiently known by using on stream beam analysis (on stream beam analysis) and power monitoring.

Embodiments of the present laser system may be hybrid systems that combine the novel laser system and method with conventional milling and machining equipment. In this manner, material may be added and removed during manufacturing, construction, repair, or other processes. Examples of such hybrid systems using other embodiments of laser systems invented by one or more of the present inventors are disclosed and taught in U.S. patent application serial No. 14/837,782, the entire disclosure of which is incorporated herein by reference.

Generally, in embodiments, laser welding uses very low gas flow to keep the optics clean, uses a gas knife to keep the optics clean, or uses an inert environment to keep the optics clean. Laser welding may be in air, inert environment, or other controlled environment (e.g., N)₂) Is carried out in (1).

Embodiments of the present invention can be of great advantage in soldering copper materials, which will include copper, pure copper, copper alloys, and all materials with sufficient copper content to have about 40% to 75% absorption at blue laser wavelengths (preferably about 400nm to about 500 nm).

There are two preferred self-fluxing welding modes and the self-fluxing welds they produce, which are performed with embodiments of the present laser system and process, conduction welds and keyhole welds. Conduction welds refer to the use of low strength: (<100kW/cm²) The laser beam of (a) welds the two pieces of metal together. Here, the two pieces of metal may butt against each other, overlap on one side and completely overlap. Conduction welds tend not to penetrate as deeply as keyhole welds, which often produce a characteristic "ball" weld for a butt weld, which is very strong. However, at relatively high laser beam intensities (>500kW/cm²) Small hole welds will occur down, which can penetrate into the material and often melt through multiple layers of material when the materials overlap. The exact threshold for the blue laser source to transition from conduction mode to keyhole mode is not determined, but the keyhole weld has a characteristic "v" shape on top of the material, with nearly parallel re-frozen material channels penetrating deep into the material. The keyhole process relies on the reflection of a laser beam from the side of the molten metal bath to transmit laser energy deep into the material. While these types of welds can be performed with any laser, it is expected that a blue laser will have a significantly lower threshold for initiating both weld types than an infrared laser.

Welding of these materials using blue laser operations is contemplated, including blue laser welding of plated materials, such as copper plated materials, platinum plated materials, and other conductive material plated materials.

The welding process for copper requires efficient coupling of power into the part, and the welding process needs to be stable and capable of producing a low porosity, low spatter weld. The present invention achieves these and other objects. The wavelength of blue laser light is highly absorbed by copper (65%) compared to infrared laser light (< 5%), thus satisfying the first part of these requirements. The second requirement depends not only on the laser absorption but also on the processing ramp or time profile, the clamping fixture, the beam profile and quality and the clamping pressure used on the part. The present embodiment provides: both keyhole mode and conduction mode welds are possible using a blue laser as the heat source. Conduction mode welding does not produce any spatter or porosity in the part during the process. The keyhole mode of welding will allow greater penetration. The embodiment of the high-power blue CW laser source is very suitable for welding copper parts, and the parts have extremely low porosity and extremely low splashing in the process.

Full penetration of a 1mm thick copper plate using a 600 watt blue laser resulted in negligible spatter (nominal spatter) remaining on the surface of the weld deposit test. A600W CW laser was focused to a spot size of about 200 μm, resulting in an average intensity of 2.1MW/cm at the surface of the part². This intensity is much higher than the power density required to initiate and maintain the keyhole in the part. During welding, the keyhole forms rapidly and once full penetration is achieved, the weld pool presents a very stable surface, indicating that as the weld progresses, turbulence in the weld pool is low. A stable welding process was observed over a wide range of welding speeds, accompanied by Ar-CO₂And a shielding gas for suppressing surface oxidation and the like during welding. This ability to create a stable keyhole weld can be attributed to the high absorption of copper in the blue, among other things. The blue laser light is uniformly absorbed by the keyhole walls during welding, however, when the keyhole is unstable due to turbulence in the weld pool, the heat input is maintained and the keyhole remains stable.

The following embodiments are provided to illustrate various embodiments of the present laser system and operation, particularly a blue laser system for welding components, including components in an electronic storage device. These examples are for illustrative purposes, may be prophetic, and should not be viewed as and otherwise limit the scope of the invention.

Example 1

The laser source is a high power blue direct diode laser with a power of 0-275 watts. The beam was transmitted through a 1.25X beam expander and focused by a 100mm aspheric lens. The spot diameter on the work piece was 200 μm x 150 μm and the power density produced at maximum power was 1.2MW/cm². The samples were held in place using a stainless steel clamp and He, Ar-CO were used₂And nitrogen, all of which are beneficial, Ar-CO₂The best results are obtained.

Example 1A

Using the system of example 1, initial test results produced high quality conduction mode welds on copper surfaces at power levels of 150 watts. A series of build-up welding (BOP) tests were performed to characterize the welds produced by the high power blue laser source. FIG. 1 illustrates a Chevron-shaped pattern of conduction mode welds, the unique characteristics of which include: the welding process has no splash, the microstructure is similar to that of the base metal, and the hardness of the welding seam is similar to that of the base metal. Fig. 1 shows the BOP formed when using a 150 watt blue laser weld on a 70 μm thick copper foil.

Example 1B

Using the system of example 1, scaling the power output of the laser to 275 Watts resulted in an increase in the power density to 1.2MW/cm²This is a sufficient power density to initiate keyhole welding in copper. Fig. 2 shows an example of a small pore weld on a 500 μm thick copper sample. During the keyhole process, the vapor pressure generated in the keyhole forces the molten copper out of the weld bead. This can be seen in fig. 2, where the ejected copper is distributed along the bead edge. This spray process is stable and does not cause micro-explosions in the material and therefore does not produce the spatter pattern observed when welding copper using an IR laser source.

Example 1C

The system of example 1 was used to perform a soldering experiment on copper having a thickness in the range of 127-500 μm. Fig. 3-5 summarize the results of these BOP tests. FIG. 3 shows full penetration at 275W up to 9m/min, followed by a decrease in penetration depth with velocity, as expected. FIG. 4 shows BOP results, with full penetration up to 0.6m/min without auxiliary gas, using Ar-CO₂When gas is protected, the total penetration is as high as 0.4 m/min. FIG. 5 shows the penetration depth of 500 μm copper at 275W as a function of velocity.

Example 2

The fixture 5000 of fig. 13 and 13A was used for successful lap welding of a stack of 2 copper foils with a thickness of 178 μm using a conduction mode weld. When heated to 100 ℃, the fixture can result in a one to two fold or more improvement in welding speed and quality because the energy lost to heat the parts during welding is now provided by preheating. The shielding gas at the top of the weld passes from the front of the weld travel direction to the back of the weld travel direction as shown in FIG. 10.

Example 3

Two 125 μm thick copper plates were lap welded together using a jig 5000 in a conduction mode weld. The weld is shown in the cross-sectional photograph of fig. 15.

Example 4

The fixing device 5000 shown in fig. 13 and 13A is used. A stack of 40 copper foils 10 μm thick was soldered together without voids and defects. The cross-section of the weld is shown in figure 17. Welding the stack depends on how the foil is prepared, how the foil is clamped, and how much torque is applied to the fixture. The foil is cut and flattened, then cleaned with alcohol to remove any manufacturing or processing oil, and finally stacked in a jig. The torque of the clamp bolt 5001 is 1Nm to ensure that the part is securely held in place during the welding process. The lasers used to weld these parts consisted of four 150 watt lasers as shown in fig. 19, which were optically combined as shown in fig. 21 to create a 500 watt laser system. The laser produced a 400 μm spot with an average power density of 400kW/cm²The peak power density is sufficient to initiate the keyhole welding process.

Example 5

Embodiments of the present laser beam welding technique were evaluated by first fully penetrating, bead welding (BOP) welds with a 600 watt blue laser to a 1mm thick copper plate, with negligible spatter remaining on the surface. A600W CW laser was focused to a spot size of about 200 μm, resulting in an average intensity of 2.1MW/cm at the surface of the part². This intensity is much higher than the power density required to initiate and maintain the keyhole in the part. During welding, a rapid keyhole formation was observed and once full penetration was achieved, the weld pool exhibited a very stable surface, indicating that as the weld proceeded, turbulence in the weld pool was low. A stable welding process was observed over a wide range of welding speeds and AJ-CO2 shielding gas was used to inhibit surface oxidation during welding. This ability to create a stable keyhole weld can be attributed to the high absorption of copper in the blue and to the laser beamUniformity and high quality. The blue laser light is uniformly absorbed by the keyhole walls during welding, however, when the keyhole is unstable due to turbulence in the weld pool, the heat input is maintained and the keyhole remains stable.

Example 6

Embodiments of the present invention use the present high power visible lasers (particularly blue, cyan, and green lasers) for industrial applications such as welding. A power level of 500-600 watts and a spot size of 200-400 μm were used in embodiments of these processes. The wavelengths of these embodiments are in the blue range. For 400 and 200 μm spot sizes on Oxygen Free Copper (OFC), stable conduction mode soldering of copper was observed over a wide speed range. This welding mode was spatter free and fully dense with no evidence of porosity throughout the welded part. Stable keyhole mode welding was observed in copper with a spot size of only 200 μm, but for lower conductivity materials such as Inconel and stainless steel, even a spot size of 400 μm could achieve a keyhole weld. Modeling of the welding process shows that there are significant differences in the shape and size of the weld pool when welding copper as compared to stainless steel. The lower thermal conductivity stainless steel exhibited a classic tear drop shaped weld pool, however, for the same power levels used when welding the stainless steel samples, the copper with the high thermal conductivity exhibited a much smaller sized circular weld pool.

Example 7

Laser welding of metals is performed using blue, cyan, or green laser beams without wobbling the beams. These welds have a deeper penetration. Thus, the use of these laser beams provides a wiggleless welding of metals (including copper foils and copper plates). The non-weaving weld is provided on aluminum, stainless steel, copper, aluminum-based metals, stainless steel-based metals, copper-based metals, and alloys of these metals.

In this embodiment of the weaving-free laser welding, the blue laser welding is carried out on copper with a thickness of less than 1mm and a blue laser beam with a wavelength of 450nm is used.

In this embodiment of the weaving-free laser welding, the blue laser welding is carried out on aluminum having a thickness of less than 1mm and a blue laser beam having a wavelength of 450nm is used.

In this embodiment of the weaving-free laser welding, the blue laser welding is carried out on stainless steel with a thickness of less than 1mm and a blue laser beam with a wavelength of 450nm is used.

Example 8

An embodiment of a 600 watt laser with four 200 watt blue laser modules provides a laser beam with a wavelength of 450 nm. As shown in fig. 19, the laser diodes are individually collimated and the beam divergence is circular, resulting in a beam parameter product of 22mm mrad for each module. The laser beams from the four blue laser modules were optically sheared in both the horizontal and vertical directions to fill the aperture of the focusing optics with a diameter of 100mm, as shown in fig. 21. The beam parameter product for this composite beam (450nm) is 44mm mrad, suitable for launch (launch) into a 400 μm fiber. For examples 8A to 8K and 9, no optical fiber was used and the blue laser beam was delivered to the workpiece through free space.

These embodiments use an optical bread board with a 4'x6' optical bench that allows real-time beam diagnostics to be integrated into the setup. 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 (far-field profile camera) and a power meter. The far field is produced by a lens of the same focal length as the soldered lens, whether a 100mm F/1 lens or a 200mm F/2 lens. Both lenses are BK7 aspheric from ThorLabs. Lens under-filled (underfilled) to about 80 mm, the spot on the workpiece is about 200 μm for a 100mm FL lens and about 400 μm for a 200mm FL lens.

Beam caustic was measured by translating the Ophir beam profiler through the focus of a 100mm FL lens in a beam sampling arm positioned and measuring the diameter of the beam at the 95% ring power point. The beam caustic is shown in fig. 22. This measurement indicates that the depth of focus for a 100mm FL lens is relatively short.

A Fanuc6 axis robot (Fanuc M-16iB) was used to move the sample through the free space beam focus, and the shrouding gas was provided by a 3/8 "diameter sparger tube mounted on the robot adapter and directed in the direction of the weld.

Examples 8A to 8K and 9 use examples of welding jigs of the type shown in fig. 12 and 12A. The welding fixture is part of the welding process, which affects the achievable penetration depth, welding speed, and both, when welding high thermal conductivity materials. Fig. 12 and 12A are diagrams of an embodiment of a welding jig. In one embodiment, aluminum (6061 series) is used. In another embodiment, stainless steel (316) is used. Aluminum welding fixtures tend to quickly remove heat from the part, while stainless steel fixtures allow most of the heat to remain in the part. Both materials are evaluated using different methods of holding a sample (e.g., workpiece, part). Inert gas (e.g. argon-CO)₂) Flows over the top of the part placed in the fixture to inhibit any oxidation of the part during welding. A small gap 4003 is located below the center of the sample to minimize heat dissipation at the weld overlay and to allow addition of a secondary gas to the back of the weld.

When welding in the keyhole welding mode, a strong plume is generated. Since the 450 μm light is easily absorbed by the atoms and ions in the plume, the plume should be managed and preferably suppressed. An 3/8' diameter tubular injector was used to deliver 50scfh of argon or argon-CO across the top of the part₂To inhibit feathering. Welds may be made or created using a variety of gases to control plume and avoid part oxidation, including argon, argon-CO₂Air, helium and nitrogen. The goal of optimizing the welding process, etc., is to achieve maximum penetration at as high a rate as possible. The data provided in examples 8A to 8K used argon as the shielding gas. Plume management is desirable and preferred in other laser welding and machining applications (e.g., butt welding).

For the 500 watt weld test of examples 8A-8F, the beam was focused to a 400 μm spot size using a 200mm focal length lens, resulting in an average intensity of about 400kW/cm²And peak intensity near 800kW/cm²。

For the 600 watt weld test of examples 8G through 8K, the beam was focused to a 200 μm spot size using a 100mm focal length lens, resulting in an average intensity of about 2.1MW/cm²And the peak intensity is close to 4.5MW/cm²。

Example 8A

Using the laser, process and setup of example 8, 500 watts, a 400 μm spot, and 400kW/cm were used²Average power density of (a), the weld build-up was performed and evaluated with copper (OFC), stainless steel (304), and aluminum (1100 series). The samples were cut to 10mm x45 mm size using a guillotine and cleaned with acetone prior to processing. Surface treatment (surface finish) is provided by McMaster Carr, with thinner samples looking like roll processing (rolled finish) and thicker samples looking like mill processing (milled finish). For a given sheet thickness, these evaluations characterize the full penetration capability of the welding process of example 8.

Using the laser, process and setup of example 8, build-up evaluations were performed with oxygen-free copper (99.99% -110) samples ranging in thickness from 80 μm to 500 μm. Fig. 23 shows the welding speed when a full penetration bead was observed on the back surface of the welded sample.

The samples were wiped with acetone and clamped in a jig with a bolt with a torque of 1Nm before evaluation. The fixture and sample are angled at 20 degrees from the beam normal to prevent back reflection to the laser, resulting in an extension of the spot for the 200mm FL lens to 400 μm x 540 μm. The beam angle is from the beam normal to the back side (trailing side) of the part to be welded. This tilting 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 a command to the robot to translate the part with sufficient distance between the part and the laser beam to ensure that the robot reaches the programmed speed, the laser being activated when the welding fixture passes the position of the laser beam. The part is translated through the beam at a constant speed, and once the end of the welding fixture is reached, the laser beam is turned off and the robot is commanded to return to its original position. The sample was cross-sectioned, polished and etched to reveal the microstructure. All welds showed a spherical melt-freeze pattern (melt-freeze pattern) indicating a conduction mode weld.

Example 8B

The samples were also evaluated for butt welding using the lasers, processes and settings of examples 8 and 8A. The parts were prepared the same as in example 8A and clamped with the same clamping force. The edge of the specimen created by the shear is the basis for the butt weld. Some of the results of these tests are shown in fig. 24. The welding speed is the speed at which two parts can be joined by a full penetration weld shown on the back of the welded part. No spatter was observed during the welding process or on the welded parts, indicating a conduction mode welding process.

Example 8C

During the evaluation of the copper 110 series samples of example 8A, a dependence of the weld penetration depth as a function of the sample thickness was observed. Fig. 25 shows how the penetration depth decreases with increasing copper sample thickness. This dependence is due to the higher thermal mass of the part and the high thermal conductivity of copper, so that heat can be quickly dissipated from the weld bead. This is due in part to the high thermal conductivity of copper and the ability to efficiently dissipate the laser energy during the soldering process. As can be seen in fig. 25, at a given speed, the penetration depth can be reduced by more than four times as the material thickness is increased by two. The penetration depth of the top housing does not decrease as significantly as in the other two cases because its velocity is much lower and it saturates the copper's ability to dissipate the laser energy. Therefore, when designing a brazing process using a conduction mode process, the limited thickness of the parts to be brazed should be considered.

Example 8D

Using the lasers, processes and settings of examples 8 and 8A, aluminum 1100 series samples were welded and evaluated. An aluminum 1100 series sample was prepared and mounted in a welding fixture as the copper part of example 8A. The welding process was similar to the brazing process of example 8A, only varying the robot speed. The welding speed shown in fig. 26 corresponds to the case where a full penetration bead is observed on the back surface of the part having the thickness. No spattering of the weld pool was observed during welding.

Example 8E

Two aluminum 1100 samples placed side by side in a welding fixture were butt welded and weld tested using the laser, process and setup of examples 8 and 8A. The samples were prepared with a guillotine, and the two edges were not specially prepared before welding. The samples were wiped with acetone prior to soldering. The welding process is the same as described for the copper parts in exhibit 8A, except for the welding speed. The final welding speed plotted is the speed at which a full penetration weld bead is obtained across the entire length of the sample being welded. The outline of this data is shown in fig. 27.

Example 8F

BOP weld and weld tests were performed on 304 stainless steel samples using the lasers, processes and settings of examples 8 and 8A. The sample was cut to 10mm x45 mm dimensions to fit the jig, wiped with acetone, and the robot speed was adjusted until a full penetration weld was obtained on the test sample. Also, no spatter or blowholes were found in the welded samples. The results of this test are shown in fig. 28.

Example 8G

Welds and evaluations were performed for the 600 watt system and the process of example 8. A100 mm focal length lens was used to focus the beam to a 200 μm spot size, resulting in an average intensity of about 2.1MW/cm²The peak intensity is close to 4.5MW/cm². A series of welds were made and tested at this higher power level and shorter focal length lens (100mm) to further evaluate and account for the penetration capability of the laser at different speeds. In these tests, the average intensity was 2.1MW/cm²The power density is fully in line with the requirement of evaporating copper and forming pores. The part is tilted by 20 degrees to reduce the effective power density to 1.4MW/cm²This strength is sufficient to initiate a keyhole welding mode in copper, aluminum and stainless steel.

The first indication of the keyhole process in copper is a significant increase in spatter during soldering. This spatter was observed using a coaxial camera (on-axis camera) while monitoring the molten pool. The weld samples were cross-sectioned, polished, and etched to reveal a microstructure freeze pattern typical of keyhole welds. The cross-section also shows a large number of pores where the beam does not fully penetrate the part. However, the fully penetrated portion of the beam shows negligible porosity.

Example 8H

Using the lasers, processes and settings of examples 8 and 8G, a longitudinal cross-section of a keyhole mode weld was made on a 500 μm thick copper 110 plate to determine the porosity along the entire length of the weld, as shown in the photograph of FIG. 29. The first centimeter of the weld on the right side of the picture shows a large number of pores and no penetration of the sample. With the heat accumulation of parts in the welding process, the copper plate is fully melted through in the small hole process. The results indicate that if the keyhole process is allowed to stabilize, it is possible to produce welds with negligible spatter and porosity.

Example 8I

The lasers, processes and settings of examples 8 and 8G were used and based on the results of example 8H, welding and testing were performed in which the keyhole was first allowed to stabilize before moving the part. The welding process is modified by allowing the laser beam to dwell on the part for a short period of time, and then the robot accelerates, drawing the hole through the part. A residence time of 0.6 seconds gives the preferred results after a series of tests with residence times varying between 0.6 seconds and 1.5 seconds. FIG. 30 is a cross-sectional photograph of a weld bead of copper 110 performed with a 0.6 second dwell on the sample, and then translation of the sample at a speed of 1.1 m/min. A series of welds were performed at this speed to verify that the process was stable and well controlled. All samples showed similar results, very low porosity and very stable small bore welds.

Example 8J

Using the lasers, processes and settings of examples 8 and 8G, welds were prepared and evaluated on a range of different thicknesses of copper 110 material. The maximum weld speed achieved for full penetration of each sample is plotted in fig. 31. Keyhole mode welding, translational mode welding, and conductive mode welding are all observed at these welding speeds. The result is a significant increase in welding speed and penetration depth compared to the 500 watt, 400 μm system.

Example 8K

Stainless steel samples were welded and evaluated using the lasers, processes and settings of examples 8 and 8G. As a result, four sheets of 304 stainless steel plates were lap-welded at a speed of 1.2 m/min. The cross-section shown in fig. 32 shows a classic profile of a keyhole welded sample. The porosity at the bottom of the aperture may be caused by the gap between the third and fourth sheets in the stack. Such porosity can be eliminated by optimizing the welding process.

Example 9

Using the lasers, processes and settings of examples 8 and 8A, a series of tests were performed on stacks of oxygen free copper foil to determine how many foils can be lap welded in a single pass. The experimental setup was the same as in example 8, but now the fixture was replaced and a small steel insert was used in the gap below the center of the part. The foil is held in place and the sample at 20 degrees to the beam normal is accompanied by Ar-CO₂The shielding gas passes through the beam. The results of these tests are summarized in fig. 33 (up to a stack of 40 foils). Two different lens configurations work very well when used in a wide range of foil thicknesses and stacks.

Fig. 34 is an example photograph of a 40 copper foil successfully soldered with no porosity and no spatter on the top surface. The stack of foils was welded with a 500 watt and 200mm FL lens, which corresponds to a spot size of 400 microns. The welding speed was 0.5 m/min. The manner in which the sheets are clamped affects the quality of the weld, providing a consistently high quality weld for good and consistent clamping of the sheets.

Headings and examples

It should be understood that the use of subheadings in this description is for clarity purposes and is not limiting in any way. Accordingly, the processes and disclosures described under the subheadings should be read in conjunction with the entire content of this specification, including the various embodiments. The use of headings in this specification should not be construed as limiting the scope of the invention.

It is noted that there is no requirement to provide or address a theoretical basis for novel and inventive processes, materials, properties, or other beneficial features and characteristics that are the subject of or associated with embodiments of the present invention. However, various theories are provided in this specification to further advance the art. The theory presented in this specification, unless explicitly stated otherwise, does not in any way limit or narrow the scope of the claimed invention. These theories are not required or practiced using the present invention. It is also to be understood that the present invention may introduce new, heretofore unknown theories to explain the functional characteristics of embodiments of the methods, articles, materials, devices, and systems of the present invention; and such subsequently developed theories should not limit the scope of the present invention.

The various embodiments of systems, devices, techniques, methods, activities, and operations set forth in this specification can be used in various other activities and in other fields than those set forth herein. Embodiments of the present invention may be used, among other things, with the methods, apparatuses, and systems of patent application publication nos. WO 2014/179345, US 2016/0067780, US 2016/0067827, US 2016/0322777, US 2017/0343729, US 2017/0341180, and US 2017/0341144, the entire disclosures of each of which are incorporated herein by reference. Further, for example, these embodiments may be used to: other devices or activities that may be developed in the future; and accompanying existing equipment or activities, which may be modified in part in accordance with the teachings of the specification. Furthermore, the various embodiments set forth in this specification may be used in different and various combinations with one another. Thus, for example, the configurations provided in the various embodiments of the present specification may be used with each other. For example, components of embodiments having A, A ' and B and components of embodiments having A ', C and D can be used in various combinations with each other according to the teachings of this specification, e.g., A, C, D and A, A ', C and D, etc. The scope of protection afforded the invention should not be limited to the particular embodiments, configurations, or arrangements set forth in the particular embodiments, examples, or embodiments in the particular drawings.

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

Claims

1. A method for laser welding together a plurality of copper foils, the method comprising

a. Positioning a plurality of copper foils in a soldering station; wherein the foil comprises at least about 50% copper;

b. applying a clamping force to the plurality of copper foils to clamp the plurality of foils together in the soldering station;

c. directing a blue laser beam along a laser beam path at the plurality of copper foils, wherein the laser beam has the following properties:

i. a power of at least 500 watts;

a beam parameter product of about 44mm mrad and less;

a spot size of about 400 μm and less;

at least about 400kW/cm²Average intensity of (d);

v. at least about 800kW/cm²Peak intensity of (d);

d. the blue laser beam is used for lap welding the plurality of copper foils together at a welding speed; and the number of the first and second groups,

e. providing a non-oxidizing beam purge gas in space along the path of the laser beam, wherein the laser beam passes from the optical element to the plurality of copper foils in free space; wherein a purge gas removes plume from the laser beam path and prevents oxidation of the plurality of copper foils;

f. wherein the welding speed, clamping force, and flow rate of non-oxidizing scavenging glass are predetermined to provide a lap weld with no visible spatter and no visible porosity.

2. The method of claim 1, wherein the optical beam is a CW optical beam.

3. The method of claim 1, wherein the beam is a pulsed beam.

4. The method of claim 1, wherein the beam of light has a wavelength of about 450 nm.

5. The method of claim 1, wherein the optical element is selected from the group consisting of a lens, a fiber face, and a window.

6. The method of claim 1, wherein the purge gas is selected from argon, argon-CO₂Air, helium andnitrogen gas.

7. The method of claim 1, wherein the laser beam is free of wobble, thereby providing a wobble-free laser welding process.

8. The method of claim 1, wherein the plurality of copper foils has 10 to 50 foils.

9. The method of claim 1, wherein the copper foil has a thickness of about 80 μm to 500 μm.

10. The method of claim 8, wherein each of the plurality of copper foils has a thickness of about 80 μm to 500 μm.

11. The method of claim 1, wherein the welding speed is at least 10 m/min.

12. A method for laser welding a plurality of metal sheets together, the method comprising:

a. positioning a plurality of pieces of metal in a welding station;

b. applying a clamping force to the plurality of pieces of metal to clamp the pieces of metal together in the welding station;

c. directing a blue laser beam along a laser beam path at the plurality of pieces of metal, wherein the laser beam has the following properties:

i. a power of at least 500 watts;

a beam parameter product of about 44mmmrad and less;

a spot size of about 400 μm or less;

at least about 400kW/cm²Average intensity of (d);

v. at least about 800kW/cm²Peak intensity of (d);

d. the blue laser beam welds the plurality of pieces of metal together at a welding speed; and the number of the first and second groups,

f. wherein the welding speed, clamping force, and flow rate of non-oxidizing scavenging glass are predetermined to provide a weld with no visible spatter and no visible porosity.

13. The method of claim 12, wherein the welding station has an air gap beneath the pieces of metal.

14. The method of claim 12, wherein 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.

15. The method of claim 14, wherein the laser beam has a wavelength of about 450 nanometers.

16. The method of claim 15, wherein the laser beam is free of wobble, thereby providing a wobble-free laser welding process.

17. The method of claim 16, wherein the weld is selected from the group of welds consisting of lap welds, butt welds, weld overlay welds, and conduction mode welds.

18. The method of claim 12, wherein the laser beam is free of wobble, thereby providing a wobble-free laser welding process.

19. The method of claim 12, wherein the weld is selected from the group of welds consisting of lap welds, butt welds, weld overlay welds, and conduction mode welds.

20. A method of laser welding together a plurality of copper foils, the method comprising:

a. positioning a plurality of copper foils in a soldering station; wherein the foil comprises at least about 50% copper; wherein the copper foil has a thickness of about 80 to 500 μm.

i. a power of at least 600 watts;

a beam parameter product of about 44mmmrad and less;

a spot size of about 200 μm to about 400 μm;

at least about 2.1MW/cm²Average intensity of (d);

v. approaching at least about 4.5MW/cm²Peak intensity of (d);

d. the blue laser beam welds the plurality of copper foils together at a welding speed of at least 10 m/min; and the number of the first and second groups,