Blue Light + Infrared Composite Welding Technology

Blue Light + Infrared Composite Welding Technology

The inevitability of blue light development.

In laser processing applications, the laser absorption rate of metals is of decisive significance for processing applications. With the growing market demand for cutting high-reflective materials such as Copper, Aluminum and their alloys, blue lasers are widely used in the field of micro-processing of copper and other metals. Copper, Gold and other materials have extremely low absorption rates for infrared and other wavelength lasers due to their high reflectivity, and they also have good thermal conductivity. When the laser is irradiated on these materials, most of the energy will be reflected, and the irradiated part of the energy will be quickly transferred to the surroundings. This makes the laser cutting of materials such as Copper, Aluminum and Alloys extremely difficult or even impossible to process.

The figure shows the comparison of the absorption rate of different materials to lasers of different wavelengths. Different types of laser light sources have different application ranges, processing objects and purposes. A large amount of practical data shows that infrared laser source perform well in many industrial applications, but are not ideal in high-reflective metal processing. High-reflective materials have extremely high laser absorption rates in the blue band emitted by blue laser source, which can reach 8-10 times that of infrared light for common high-reflective materials such as Aluminum and Copper.

Basic properties of blue laser source

  Blue laser source is a semiconductor laser source. According to the standard packaging form, semiconductor lasers are mainly single tube, bar, and stacked array.

The upper left picture shows the single tube structure of semiconductor laser. Each laser source is an independent unit. Since it is not affected by thermal crosstalk, it has good heat dissipation characteristics, long life, and can work for up to 200,000 hours; the luminous width is generally 5um-10um. The current commercial 9xx single tube semiconductor laser source has a maximum power of up to 15w. The upper right picture shows a one-dimensional single tube array semiconductor laser Bar structure. Generally, each single tube of the bar will be arranged at a certain interval, and the number of single tubes in the Bar may be 19, 24, or 49. Each Bar is equivalent to multiple single tubes arranged and packaged. In general, the width of the Bar is 1 cm, so it is also called a centimeter Bar, in recent years, a Mini-Bar has been studied and used, mainly composed of 5 single-tube light-emitting units. The high-power red laser module currently produced by DILAS in Germany is developed using this Mini-Bar. At present, the output power of a single bar can reach 1000W, and the commercial bar power can achieve 200W output, which requires water cooling. The following two figures show a two-dimensional single-tube array semiconductor laser chip. Since there are more light-emitting points than bars and single tubes, it has a higher output power. At present, the maximum power of the stacked array produced by DILAS in Germany is 8000W. Since the light-emitting points in the stacked array are arranged more compactly, the heat dissipation requirements are very high.

As a semiconductor laser, its working principle is that the electrons in the internal semiconductor material undergo transitions to stimulate photon radiation, thereby causing light oscillation and amplification. The basic conditions for a laser to produce lasers are: an excitation source, a gain medium, and a stable resonant cavity. The generation of blue light is also done by combining single diodes into bars and then into stacks, and finally synthesizing into lasers.

It can be clearly seen from the surface morphology of the weld that copper "loves" blue light. The weld is smooth and uniform, with no defects or unevenness. This smooth surface morphology shows that the copper material can be well integrated during the welding process and forms a continuous and uniform interface after cooling. This smooth and uniform weld surface not only improves the strength of the welded joint, but also makes the entire weld area more beautiful.

                      Near-infrared wavelength - 2000W                                                                              Blue wavelength - 500W

The figure shows the tensile curves of the base material and the welded joint. It can be seen that the tensile strength of the base material is about 300 MPa. When infrared fiber laser welding is used, under the optimal process parameters, the tensile strength of the welded joint is 156 MPa, which is about 50% of the base material, and the elongation is about 55% of the base material. When blue light semiconductor laser welding is used, under the optimal process parameters, the tensile strength of the welded joint is 246 MPa, which is about 30% higher than that of the infrared fiber laser welded joint, and the elongation is about 40% higher.

When near-infrared fiber laser welding is used, under the conditions of 2000W power and 20mm/s welding speed, the cross section of the weld is shown in the left figure. It can be seen that the weld is conical, the front width of the weld is wide, the back width of the weld is narrow, and there is a relative bending on both sides of the weld, and the deformation is large. This is because copper has a low absorption rate of near-infrared wavelength lasers, only 4%, and a higher laser power is required to reach the melting point of copper. Higher laser energy input causes the material to deform more. When blue light semiconductor laser welding is used, under the conditions of 500W power and 20mm/s welding speed, the cross section of the weld is shown in the right figure. It can be seen that the weld is trapezoidal, the front width of the weld is narrow, the back width of the weld is wide, and there is no obvious bending on both sides of the weld, and the deformation is small. This is because copper has a high absorption rate of blue light wavelength lasers, reaching 40%, and only a lower laser power is required to reach the melting point of copper. The lower laser energy input allows the upper material to quickly transmit the laser energy to the lower material after absorbing the laser energy, resulting in a wider back width of the weld and less material deformation under lower laser energy input.

Necessity of blue light + infrared composite welding

For infrared: For the welding of high-reflective materials, infrared laser processing has high-temperature steam pressure, obvious spatter, and severe molten pool fluctuations.

Regarding blue light

The power of a single semiconductor chip is low. Under the same core diameter, the number of light beams that can be coupled in is fixed, so the overall power density must be low. Therefore, blue light can only be used as an auxiliary function.

Advantages of blue light + infrared composite:

(1) Based on the greatly improved absorption rate of non-ferrous metals, especially Cu at blue light wavelengths, low-power blue light can be used to effectively process Cu-based materials;

(2) Based on the power amplification principle of blue light lasers, the energy distribution of blue light sources is more uniform, which has unique advantages in achieving uniformity in the processing area and suppressing splashes caused by uneven energy distribution;

(3) Based on the current development of blue light technology, the kilowatt-level technical level and cost are already relatively high. Combining it with relatively mature fiber lasers can greatly improve processing scenarios and efficiency.

Blue light + infrared composite realization

The following is a detailed explanation of the optical path diagram of the dual-wavelength coaxial system. This system has designed a unique optical path through precise optical lens coating technology. The core idea is that through a specific optical lens arrangement and coating design, two beams of light with different wavelengths can enter and focus on the parent material at the same time. The advantage of this optical path design is that it can converge light beams of different wavelengths to the same focus, thereby realizing the parallel processing of dual wavelengths or more wavelengths. In addition, this design can also improve the stability and reliability of the optical system because all optical components are located on the same axis, reducing errors and distortion. In the process of realizing this design, the key technologies include the precise selection, precise assembly and precise coating of optical lenses. First, it is necessary to select lenses with the required optical properties in order to correctly guide and focus light of different wavelengths. Secondly, these lenses need to be assembled together in a high-precision manner to ensure the accurate alignment of the light. Finally, it is necessary to use precise coating technology to ensure that the lenses can accurately reflect and transmit the required light. In general, the optical path design of the dual-wavelength coaxial system is an innovative technology that can realize the parallel processing of light of different wavelengths and improve the stability and reliability of the optical system. This design is achieved through sophisticated optical lens coating technology and high-precision assembly technology, providing technical support for various applications.

Blue light + infrared composite application

1) Square shell battery pole welding

The battery pole is a key component for connecting the inside and outside of the battery. Pole welding is an indispensable link in the production process of power battery cover. In order to ensure excellent electrical performance, copper and aluminum alloy are commonly used materials in pole welding. By adopting blue light composite welding technology, excellent welding quality can be obtained.

2) Soft connection of square shell battery

The adapter welding process is a key step in the production of power batteries. Its purpose is to reliably connect the battery cell tabs with the top cover poles. However, since the tabs made of multi-layer foil cannot directly achieve high-quality connection with the poles, adapter technology is required. In recent years, with the continuous development of blue light related technologies, this process has made certain breakthroughs and is expected to lead the technological innovation of power battery production processes. In traditional laser welding technology, due to the special structure of multi-layer foil, high-quality connection between the tabs and the poles cannot be achieved. Therefore, adapter welding technology is needed to solve this problem. Adapter welding technology achieves reliable connection between the tabs and the poles by setting a adapter between the tabs and the poles. With the continuous development of blue light related technologies, this process has made certain breakthroughs. Blue light related technology is a new type of welding technology with the advantages of fast speed, high precision and low cost. In the production of power batteries, the use of blue light related technology can achieve high-quality connection between the tabs and the poles, and improve the energy density and safety of the battery. In short, the adapter welding process is a key step in the production of power batteries. With the continuous development of blue light related technologies, this process has made certain breakthroughs and is expected to lead the technological innovation of power battery production processes.

3) Flat wire motor

The current laser technology used to weld flat copper wire mainly uses infrared lasers, but because copper has a very low absorption rate for infrared lasers, high-power lasers are required during the welding process, which makes the equipment cost high. In addition, high-power welding will cause excessive heat, which is very easy to damage the enameled layer of the flat copper wire. At the same time, the spatter generated during the welding process is large, and the spatter will scatter inside the motor, resulting in reduced product performance. However, the use of blue light composite welding technology can reduce the power used by the equipment, significantly reduce welding spatter, and improve product quality. This new welding technology not only reduces equipment costs, but also improves welding efficiency and quality. Therefore, blue light composite welding technology is a more attractive and readable welding method.

4) Copper/brass radiator

Copper is widely used in the radiator industry because of its good heat dissipation performance and lower cost than gold and silver. Since copper has a very poor absorption rate for infrared light, its welding usually requires a very high laser power density. During the welding process, extremely high power density can form keyhole welding, but the flow characteristics of liquid copper cause the keyhole opening to close quickly. The high-pressure gas inside the keyhole can easily open the keyhole opening, forming welding spatter, which seriously leads to weld hole defects.

Outlook

In the future, with the continuous development of materials science and micro-nano manufacturing technology, blue lasers will continue to be improved and optimized. It is expected that more efficient blue lasers will be available in the future, with higher output power, smaller size, and lower cost, which can meet the application needs of more fields. At the same time, with the continuous development of artificial intelligence and machine learning technology, the intelligence of blue lasers will also become one of the important trends in the future. By introducing artificial intelligence technology, intelligent control and optimization of lasers can be achieved to improve their performance and efficiency. In short, as a new type of laser that has developed rapidly in recent years, the development of blue lasers is full of challenges and opportunities. With the continuous advancement of technology and the continuous growth of application needs, blue lasers will continue to be improved and optimized, making more contributions to the development of human society.