Laser Diode Assembly Steel-Copper Housing Thermal Management
Solution Overview
Problem
Current laser diodes in standard TO housings are limited to optical powers of less than 3 watts, which is insufficient for many applications, and attempts to increase power by using copper-based housings or thicker solder layers have not resulted in significant improvements.
Innovation Solution
A laser diode assembly with a copper-based housing having a steel sheath and thick solder layers, combined with a crystalline protective layer, to enhance thermal conductivity and compensate for thermally induced strains, allowing for higher optical output power and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard steel TO housings are used, then manufacturing cost and standardization are improved, but optical power is limited to less than 3 watts
Solution Approach 1:
The patent applies composite materials by combining steel and copper in a hybrid housing structure. The housing consists of a steel base plate providing mechanical strength and a copper mounting part providing high thermal conductivity. This composite approach allows the housing to simultaneously offer standardization benefits of steel TO housings and the high power capability needed for optical powers exceeding 3 watts through improved heat dissipation.
2Temperature
If copper-based housings are used, then thermal conductivity is improved, but manufacturing complexity increases due to steel sheathing requirement
Solution Approach 1:
The housing is segmented into distinct functional parts: a steel base plate for mechanical support and a separate copper mounting part for thermal management. This segmentation allows each material to be optimized for its specific function while simplifying the manufacturing process compared to attempting to create a fully copper housing with steel sheathing. The copper mounting part can be separately manufactured and then assembled to the steel base plate.
Solution Approach 2:
Different regions of the housing are assigned different materials based on local requirements: the base plate region requires steel for structural integrity and welding compatibility, while the mounting part region requires copper for high thermal conductivity. This local quality approach ensures that each part of the housing has the optimal material properties for its specific function, resolving the contradiction between thermal performance and manufacturing complexity.
3Loss of energy
If thin solder layers are used, then thermal resistance is reduced, but thermally induced strains are not compensated
Solution Approach 1:
The solder layer thickness is optimized to a specific range (2-10 micrometers) that balances two competing requirements: it is thick enough to compensate for thermally induced strains between the copper housing and the laser diode chip, yet thin enough to maintain low thermal resistance. This parameter optimization resolves the contradiction by finding the optimal thickness value that satisfies both thermal and mechanical requirements.
4Power
If optical power is increased beyond 3 watts, then application suitability is improved, but component reliability deteriorates due to thermal management challenges
Solution Approach 1:
The hybrid steel-copper housing provides the high thermal conductivity needed to manage heat from optical powers exceeding 3 watts, while the steel base plate ensures mechanical stability and welding compatibility for reliable assembly. This composite structure enables the laser diode assembly to operate at high optical powers without compromising component reliability through improved thermal management.
Solution Approach 2:
The solder layer thickness is specifically optimized to compensate for thermally induced strains that increase with higher optical powers. By adjusting the solder layer parameter to an optimal thickness range, the housing can reliably accommodate high power operation while maintaining component integrity and preventing failure due to thermal expansion mismatches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves optical output powers exceeding 3 watts and improves conversion efficiency of electrical input power to optical output power, while maintaining component reliability and protecting against environmental influences.
Implementation Method 1
the housing described here has a higher thermal conductivity on account of the copper of the steel-sheathed housing part
Implementation Method 2
thick solder layers, combined with a crystalline protective layer, to enhance thermal conductivity and compensate for thermally induced strains
Data Source
AI summary
A laser diode assembly includes a housing having a housing part and a mounting part, which is connected to the housing part and which extends away from the housing part along an extension direction. A laser diode chip is disposed on the mounting part. The laser diode chip has, on a substrate, semiconductor layers with an active layer for emitting light. The housing part and the mounting part have a main body composed of copper and at least the housing part is steel-sheathed. A first solder layer having a thickness of greater than or equal to 2 μm is arranged between the laser diode chip and the mounting part. The laser diode chip has a radiation coupling-out area, on which a crystalline protective layer is applied.