Copper Welding with
Blue High-Power Diode Laser

450 nm wavelength and 2000 W laser power (CW) open up new possibilities for spatter-free and high-quality laser welding of copper. It supports the effective processing of gold and other non-ferrous metals in industrial series production.

Copper, Gold and Other Non-Ferrous Metals

With previously available industrial laser beam sources, increased effort was required to process highly reflective metals such as copper satisfactorily in series production. Blue laser light opens up new opportunities because above all copper and gold absorb the blue light spectrum seven to twenty times better compared to laser radiation in the infrared range (see diagram).

Now a first high-power diode laser has been developed that considerably improves the laser material processing of non-ferrous metals. Especially thin foils and sheets can be processed much more effectively with the blue laser. But the blue LDM diode laser offers even more advantages.

In addition to the high absorption of blue light, which greatly simplifies the melting of copper, the use of the typical diode laser intensity profile also contributes to the optimum processing result. Furthermore, Laserline's proven diode laser technology allows a finely graduated regulation of the laser power within milliseconds and thus an optimal adaptation to the process requirements. The weld seams created during copper welding are extremely clean and very smooth – regardless of the surface quality of the material before the welding process. They have excellent electrical conductivity and only a few spatters on adjacent material areas. The material efficiency is also particularly high, as the blue laser does on the one hand not require any overlaps or material reinforcements in the seam area. On the other hand, liquid copper has a high gap bridging capacity when processing with blue laser radiation. The possibility of controlled heat conduction welding makes it possible for the first time to use copper as the upper joining component when welding different metals. Laser welding copper to aluminum or steel can even be achieved with copper powder and thin copper foils. When welding foils, considerable results have already been achieved in butt and edge welding.

The total energy consumption required for welding copper has been mathematically reduced by 84 percent compared to infrared lasers, and by as much as 92 percent for gold. This is due to the fact that 1 kW is now sufficient for welding copper and 0.5 kW for welding gold instead of 10 kW.

For the user, the LDM platform provides a familiar and industrially proven system technology that can be used in conjunction with processing optics optimized for the wavelength. Otherwise, only a few modifications are necessary to integrate the laser into production. Only the sight protection windows of processing cells and protective goggles have to be replaced due to the changed wavelength range in order to meet the requirements of laser safety for the employees in the company.

Laser Welding Copper

Laser welding of copper is revolutionized by the development of a new blue diode laser. The blue laser beam enables high-quality processing of copper and other non-ferrous metals in industrial processes.

Copper Laser Welding – The Process

With the blue laser, controlled heat conduction welding of copper and other non-ferrous metals with low material thickness is possible for the first time. Material thicknesses of less than one millimeter are no longer a problem. Whereas thin foils were previously cut rather than joined with an infrared laser, the blue laser can now be used to process the material in a targeted and controlled manner. With the help of the blue laser beam, the desired material is melted along the joints. The liquefied materials flow into each other and form the weld seam when they cool down. This process results in particularly smooth seams that are of outstanding quality and therefore highly stable. Basically, the process is the same as with an infrared laser – apart from the wavelength used.

Laser Welding of Copper Pins with Blue Diode Laser

Laser welding of two copper pins (approx. 0.5x1.5mm²) with 450nm wavelength and 100ms pulse time for electrical applications.  

Heat conduction welding with the blue diode laser LDMblue leads to a very stable, homogeneous molten pool without evaporation. The dominant surface tension of the liquid copper bridges gaps between the pins, resulting in a homogeneous connection.

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Excellent Results

Initial tests show that the structure of the surface has no influence on the welding process, especially when processing copper. No matter whether the copper has been finely brushed, oxidized or etched in advance – the positive properties of the seam are retained.

Heat Conduction Welding of Copper with 450nm Wavelength

Bead on plate weld on a pure copper sheet (0.5mm thickness) with the Laserline LDMblue500-60

Heat conduction welding with a wavelength of 450 nm and a focus diameter of 600 µm ensures a highly stable molten pool without spatters in the welding process.

Laser: LDMblue 500-60
Copper sheet: 0,5mm
Focus diameter: Ø0.6mm

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On welding copper components

In our series “diode lasers in their application”, we regularly present the most important applications based on diode lasers. One particular application field should not be forgotten: copper welding.

But why is this special application so important? Copper is one of the most important raw materials for electrical signal transmission and thus a key component of many modern technologies. In battery cells of mobile devices, in induction coils or in accumulators of electric cars, copper segments can today be found everywhere. Often the components are exposed to a high current, high operating temperatures and strong vibrations. This significantly affects the production process: When components are made of several parts, the joining seams must be highly solid and must not create additional resistances in the signal flow to prevent an increased temperature in the component. As brazed joints often lack the required head resistance, weld seams created by lasers are the best option here.

Why blue diode lasers?

However, not every diode laser is the same nor is every copper. What sounds trivial at first is, however, decisive. Because, when quickly taking a closer look at the copper components, the wide spectrum of the components becomes clear: Wafer-thin wires are used as well as sheets with thicknesses of several millimeters. This affects what kind of welding tool has to be used. When thin foils have to be joined, low-impact depths and moderate-energy inputs are essential. High intensities would separate the copper foil immediately, but since you need high intensities to fuse copper with the infrared laser, you are faced with a dilemma. Thus, the infrared diode laser is not suitable for processing filigree copper components; rather, the ideal is to weld with blue diode lasers, as with Laserline’s LDMblue, the world's first blue industrial laser in the multi-kilowatt range. The reason? Wavelengths in the blue spectrum can be absorbed outstandingly well by copper. With the 450 nm of the new LDMblue, an absorption rate of way above 50 percent is reached, and when talking about laser welding of thin non-ferrous metals this is a quantum leap. A direct comparison with this industry’s typical infrared lasers makes this strikingly clear: With identical process conditions at copper welding via IR radiation, only an absorption rate of 5 percent is attained. Therefore, infrared-based copper welding is only possible with high laser output powers. Additionally, the process is often unstable hence welding mistakes occur, mainly spatters. With the blue diode laser, these problems belong to the past. Thanks to clearly improved absorption with the LDMblue, a moderate energy input and thus a controlled heat conduction welding of copper can be realized for the first time. Low impact depths and low material vaporizations create homogeneous weld seams without spatters or pore formation. 

However, as soon as thicker copper components are to be joined, the blue diode laser finds its limit because joining thick sheets could only be realized with the deep welding process, a method that is only possible with very high radiation intensity due to the good thermal conductivity of copper. Here, the high absorption of the LDMblue did not offer much help: At 1,000 Watt it reaches typical welding penetration depths of 0.6 to 0.7 mm. Higher output powers — currently LDMblue lasers with up to 2 kW are available — improve the welding penetration depth. Since blue diode lasers are more expensive to produce than infrared systems, keyhole welding of copper is currently facing the question of economic efficiency. The use of a classic infrared laser would be much cheaper in this application, but the already mentioned process disadvantages - instability and welding defects - stand in the way of an efficient welding process here as well with the world's first blue industrial laser in the multi-kilowatt range.

Hybrid concept for deeper welding seams

So, Laserline has developed alternative approaches. The result was a completely new hybrid concept that combines both laser versions. Over a special focusing optics, the beam of a blue diode laser is joined with the beam of a classical infrared laser. The blue spot with a diameter of 0.6 - 1 mm is overlaid by a smaller infrared spot, on account of which, the advantages of both methods can be combined: To fuse the workpiece surface, the high absorption rate of the blue diode laser is used at the beginning. The connected infrared laser now opens the vapor capillary and realizes the actual deep welding process. During the whole process, the LDMblue stays connected and guarantees a calm and stable molten pool, hence an innovative approach with astounding success. In terms of welding penetration depth, seam quality and process calmness, the results are overall fairly convincing. At welding penetration depths of up to 3 mm, calm molten pools without visible spatters in the seam area and usually without pores as well can be fully realized. At the lap welding of two copper sheets as well as at the butt-joint, extraordinarily smooth joining seams are created and impurities are nowhere to be found. 

Laserline Hybrid Conzept: Blue + IR

Laser copper welding with Hybrid process

Copper Cladding

The initial tests show that with the blue laser, cladding with copper powder is also possible.

Copper Cladding – The Process

The blue laser was also able to convince in the first test runs of deposition welding with copper powder. In this process – also known as laser cladding – the blue laser beam creates a molten pool on the surface of the workpiece. With the aid of a powder nozzle, the copper is added at the same time so that it can be melted in the same beam. After a short cooling time, the workpiece and copper powder are now metallurgically bonded together. In addition, the welding process causes very little distortion and the coating is extremely durable. Here, too, the process is similar to that one of the laser in the infrared wave spectrum. Furthermore, the coating is electrically conductive due to the physical properties of copper.

Cladding with Copper Powder

Particularly good results were already achieved with the blue laser when cladding with copper powder on workpieces made of steel materials. Thanks to the high absorption of the blue laser beam, direct deposition welding of copper powder onto a copper substrate is now possible for the first time. Contact us to learn about more Laser welding copper applications that are possible.

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