Engineering application analysis of molybdenum foil in automotive lighting system
High reflectivity temperature resistant reflector: reconstruction of optical stability boundary
In the automotive lighting system, the traditional injection molding PBT reflector has obvious performance bottleneck. When the temperature reaches 150℃, the glass transition of the PBT reflector will occur, resulting in reflectivity attenuation of more than 30%, surface shape accuracy deviation of ±0.15mm, and stress cracking phenomenon will occur after 500 hours of xenon lamp aging test.
In order to solve this technical pain point, molybdenum strip reflector came into being. The magnetron sputtering coating process includes substrate pretreatment, molybdenum foil etching (line width accuracy up to ±5μm), Al target sputtering (deposition rate of 3μm/min), and plasma-enhanced SiO₂ protective layer preparation. In terms of key parameter control, the substrate temperature is controlled at 300±10℃ to ensure the density of the film layer; The working pressure is maintained at 0.25Pa to optimize the uniformity of the reflectivity. The bias current is set to 1.5A to inhibit the growth of columnar crystals. After performance verification, the initial reflectance of molybdenum foil aluminized reflector reaches 97.2%, which is much higher than 92.5% of PBT reflector. After the thermal cycle test (1000 times), the reflection retention rate of the molybdenum foil reflector was 98.7%, while the PBT reflector was only 68.4%. In terms of corrosion resistance, molybdenum foil reflectors reach Class 0, which is better than the Class 3 of PBT reflectors.
Second, drive system thermal management: crack the power density ceiling
Thermal failure is a key problem in the drive system of automotive lighting system. When the LED drive current density exceeds 8A/mm², the light decay rate will increase by 1.8 times for every 10 ° C increase in junction temperature. Due to the mismatch of thermal expansion coefficient of traditional Cu heat sink, micro-cracks will occur, resulting in decreased heat dissipation performance.
To solve this problem, molybdenum strip thermal topology optimization design provides a solution. The 0.3mm thick molybdenum foil fin array can effectively improve the heat dissipation performance. In the implementation of the project, the heat flux was increased from 19W/cm² to 35W/cm², and the junction temperature fluctuation was controlled at ±1.5℃, which met the requirements.
Third, technical and economic iteration and expansion suggestions
From the perspective of technology generation, the application of molybdenum foil in automotive lighting systems has experienced the evolution from the first generation of aluminum substrate to the second generation of molybdenum copper composite materials, and then to the third generation of all molybdenum foil materials. In terms of material costs, as material costs increase, the energy efficiency of the system also increases significantly. The system energy efficiency of the first generation of aluminum-based materials is 136lm/W, the second generation of molybdenum copper composite materials is increased to 158lm/W, and the third generation of all-moly foil materials reaches 182lm/W. In terms of maintenance rate, the maintenance rate of the first generation of aluminum based materials is 3.7%/ year, the second generation of molybdenum copper composite materials is reduced to 1.2%/ year, and the third generation of all molybdenum foil materials is only 0.4%/ year. The molybdenum foil scheme can reduce the weight of the vehicle lighting system by 300g and reduce CO₂ emissions by 1.2g/km.
In order to further expand the application of molybdenum foil in automotive lighting systems, it can be considered to increase the texture treatment process of molybdenum foil surface, such as laser hair, to improve the uniformity of light field.
Mosten Alloy can produce molybdenum sheet, molybdenum block, molybdenum foil, molybdenum rod, molybdenum wire, molybdenum processing workpiece according to customer demand.
