Application of Laser Welding Technology in Thermal Management

Laser welding holds significant application value in the field of thermal management, primarily leveraging its high-precision and low-heat-input characteristics to enable the design and fabrication of efficient heat dissipation structures. The following outlines its main application areas and technical advantages.

Laser welding is an efficient and precise welding method that utilizes a high-energy-density laser beam as a heat source. In its early stages of development, it was primarily used for welding thin-walled materials and low-speed welding. The process is typically of the heat conduction type, where the laser radiation heats the surface of the workpiece, and the surface heat diffuses inward through thermal conduction. By controlling parameters such as laser pulse width, energy, peak power, and repetition frequency, the workpiece material is melted to form a specific molten pool. Due to its unique advantages, it is now widely applied in thermal management. The key parameters of laser welding are as follows:

(1) Power Density: Power density is one of the most critical parameters in laser processing. With higher power density, the surface layer can be heated to boiling point within microseconds, generating significant vaporization. Therefore, high power density is advantageous for material removal processes such as drilling, cutting, and engraving. With lower power density, it takes several milliseconds for the surface temperature to reach the boiling point. Before surface vaporization occurs, the underlying layer reaches the melting point, which facilitates the formation of a good fusion weld. Thus, in conduction-mode laser welding, the power density typically ranges from 10⁴ to 10⁶ W/cm².

(2) Laser Pulse Waveform: The laser pulse waveform is a critical issue in laser welding, particularly important for thin sheet welding. When a high-intensity laser beam strikes the material surface, 60% to 98% of the laser energy is lost due to reflection from the metal surface, and the reflectivity varies with surface temperature. During a single laser pulse, the reflectivity of the metal changes significantly.

(3) Laser Pulse Width: Pulse width is a crucial parameter in pulsed laser welding. It serves as a key differentiator between material removal and material melting and is also a decisive factor affecting the cost and volume of the processing equipment.

(4) Effect of Defocus Amount on Weld Quality: Laser welding typically requires a certain defocus amount because the power density at the center of the laser spot at the focal point is too high, which can easily cause evaporation and keyhole formation. On planes away from the laser focal plane, the power density distribution is relatively uniform. There are two types of defocusing: positive defocus and negative defocus. Positive defocus occurs when the focal plane is above the workpiece, and negative defocus occurs when it is below.

(5) Welding Speed: The welding speed affects the heat input per unit time. If the welding speed is too slow, the heat input is excessive, leading to burn-through of the workpiece. If the welding speed is too fast, the heat input is insufficient, resulting in incomplete penetration.

• Micro-channel Heat Sinks: Laser welding enables precise joining of ultra-thin wall (0.1–0.5 mm) micro-channels, avoiding blockages or deformations caused by traditional brazing, thereby improving coolant flow efficiency.
• Copper/Aluminum Dissimilar Material Welding: Through laser oscillating welding or hybrid welding techniques, issues related to brittle intermetallic compounds at the copper-aluminum interface are mitigated, optimizing the heat conduction path.

• Liquid Cooling Plate Welding: Laser welding of battery pack liquid cooling plates (often made of aluminum alloy) achieves high weld hermeticity, ensuring zero coolant leakage.
• Busbar Welding: Welding of copper/aluminum busbars in battery modules features a small heat-affected zone, preventing thermal damage to battery cells.

• Chip-to-Heat Spreader Attachment: Used for welding CPU/GPU heat sink bases (e.g., copper posts to aluminum fins). Localized heat input is low, preventing thermal failure of semiconductor devices.
• Vapor Chamber Sealing: Laser hermetic sealing of vapor chamber (VC) cavities maintains high vacuum levels, enhancing phase-change heat dissipation efficiency.

• Satellite Heat Dissipation Panels: Welding of titanium alloy/aluminum alloy heat pipes to radiator panels, adapted to extreme temperature variations in space. Weld strength can reach over 90% of the base material.
• Engine Cooling Channel Repair: Laser cladding repair of internal cooling channels in turbine blades, restoring heat dissipation functionality.

Low Heat Input and Deformation Control

• The width of the heat-affected zone can be controlled within 0.1–0.3 mm, minimizing welding deformation and making it suitable for assembling precision heat dissipation structures (e.g., micro-channels).

High Hermeticity Requirements

• Weld depths can reach 0.5–3 mm, with hermeticity superior to traditional welding methods, meeting the high-pressure (≥1 MPa) leak-proof requirements of liquid cooling systems.

Compatibility with Dissimilar Materials

• Through laser-arc hybrid welding or the addition of intermediate layers (e.g., nickel, silver foil), high-strength joining of dissimilar materials such as copper-aluminum and steel-aluminum is achieved, optimizing thermal conduction/dissipation design.

Automation Integration

• When integrated with robots and vision positioning systems, complex three-dimensional flow channels (e.g., serpentine cooling tubes) can be welded, increasing production efficiency by 30%–50%.

• New Energy Vehicle Battery Liquid Cooling Plate: A 3 kW fiber laser was used to weld 0.8 mm thick aluminum alloy at a welding speed of 8 m/min, achieving a leakage rate below 5×10⁻⁴ Pa·m³/s.
• 5G Base Station AAU Heat Sink: Nanosecond pulsed laser welding was employed to join copper heat pipes and aluminum fins, resulting in a 15% increase in thermal conductivity and a 20% reduction in weight.

1. Intelligent Process Monitoring: Integration of infrared thermal imagers and spectral monitoring for real-time feedback on weld penetration depth and defects.
2. Ultrafast Laser Welding: Application of femtosecond/picosecond lasers for welding ceramic heat dissipation substrates (e.g., aluminum nitride), overcoming bottlenecks in joining non-metallic materials.
3. Multi-Material Integrated Heat Dissipation: Combining 3D printing with laser welding to achieve integrated manufacturing of heat sinks with functionally graded materials.

The core value of laser welding in the field of thermal management lies in enabling the highly reliable fabrication of thermally conductive, lightweight, and compact heat dissipation structures. As the demand for heat dissipation efficiency continues to rise in new energy vehicles, high-power electronics, and aerospace sectors, laser welding technology will persistently evolve towards multi-material compatibility, low-damage processing, and intelligentization, establishing itself as a key enabling technology for the advancement of thermal management systems.