Laser welding process solution for power battery module PACK
Release time: 2021-07-07
Laser Welding Solutions for Power Battery Module PACK
Published on: 2021-07-07
Laser welding is widely used in power battery modules, with aluminum alloy being the primary material, supplemented by red copper, nickel, and occasionally stainless steel for battery casings. Among these materials, laser welding processes for nickel and stainless steel are relatively simple and mature. However, welding aluminum alloy and red copper remains challenging. In addition to material properties, the condition of the welding joints also significantly impacts welding quality.
1. Types and Conditions of Materials to Be Welded
Materials to Be Welded:
When aluminum alloy and red copper are used as welding materials, the main reasons for poor laser welding results are:
1. Both materials are highly reflective to fiber lasers, resulting in low absorption rates and unstable welding processes.
2. Their high thermal conductivity makes it difficult to form welds, often leading to porosity.
While these materials share similarities, there are differences:
- Aluminum alloy has a higher absorption rate for fiber lasers compared to red copper.
- Red copper has better thermal conductivity than aluminum alloy.
Solutions for Aluminum Alloy:
1. Use a relatively small focus spot (0.1mm-0.3mm).
2. Maintain a welding speed above 60mm/s.
3. Employ fiber-semiconductor composite laser welding.
4. Utilize oscillating welding.
Solutions for Red Copper:
1. Use a smaller focus spot (0.02mm-0.2mm).
2. Maintain a high welding speed (above 100mm/s).
3. Utilize oscillating welding.
Material Conditions:
The condition of the materials, such as surface cleanliness and pre-treatment, can significantly affect weld quality.
1. Surface Contaminants:
- Issues: Porosity, poor sealing, and insufficient strength.
- Solution: Remove oil, water stains, and other impurities before welding.
2. Aluminum Oxide on Surface:
- Issues: Excessive porosity, poor sealing, and reduced strength.
- Solution: Remove the oxide layer before welding and proceed promptly.
3. Rough Welding Surfaces:
- Issues: Uneven weld formation and poor sealing.
- Solution: Ensure surfaces are machined flat and free from deformation.
2. Types and Requirements of Welded Components
The mainstream power batteries for vehicles include prismatic, cylindrical, and pouch cells. Prismatic cells are the most commonly used and require the most laser welding. The other two types have smaller market shares and fewer welding requirements.
Common welding issues include insufficient strength, poor sealing, and uneven weld formation. These problems often arise from incorrect welding processes and structural challenges at the welding site.
1. Pouch Cell Components - Tabs/Busbars:
- Challenges: Thin materials, multi-layer welding leading to weak joints and poor conductivity.
- Solutions: Ensure material flatness; design high-performance fixtures to control clamping gaps.
2. Cylindrical Cell Components - 21700 Battery Caps:
- Challenges: Thin materials prone to burn-through and insufficient strength.
- Solutions: Ensure material consistency; design high-performance fixtures; use small-core fiber lasers with high-speed (above 300mm/s) welding.
3. Power Battery Modules:
- Challenges: Deep penetration requirements and poor weld formation.
- Solutions: Use fiber lasers with 50μm～100μm cores and high power for fast welding (above 80mm/s).
4. Prismatic Cell Components:
- Challenges: Porosity and burn spots leading to poor sealing.
- Solutions: Improve surface cleanliness; use 50μm core fiber lasers with increased welding speed.
5. Casing Sealing:
- Challenges: Porosity, burn spots, and uneven weld formation.
- Solutions: Improve surface cleanliness; use 50μm core fiber lasers; employ composite welding with small-core fiber and semiconductor lasers.
6. Busbars:
- Challenges: Thin materials, weak joints, and poor conductivity.
- Solutions: Ensure material flatness; design high-performance fixtures; use small-core fiber lasers with oscillating welding.
7. Side Plates:
- Challenges: Multiple welding points and high efficiency requirements.
- Solutions: Use high-power fiber lasers for remote scanning welding.
8. Flexible Connectors:
- Challenges: Thin materials, weak joints, and poor conductivity.
- Solutions: Ensure material flatness; design high-performance fixtures; use small-core fiber lasers with oscillating welding.
This solution provides a comprehensive approach to addressing the challenges of laser welding in power battery modules, ensuring high-quality and efficient production.
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