Hermetic Laser Emitter Module Thermal Stress Management
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Solution Overview
Problem
The assembly and packaging of laser diode bars in hermetically sealed enclosures are challenging due to heat dissipation and optical alignment requirements, particularly in systems where hermetic sealing is necessary, as conventional mounting methods like epoxy adhesive can contaminate the system and fail to manage thermal stresses effectively.
Innovation Solution
The use of a laser chip with a low coefficient of thermal expansion (CTE) and a submount member with high thermal conductivity, along with a CTE-matched spacer and housing base, secured with thermally conductive soft or hard adhesives to minimize stress transmission and ensure efficient heat dissipation, while maintaining hermetic sealing through conductive pins and ceramic heat dissipation plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy adhesive mounting is used to secure optical components in a hermetically sealed unit, then the assembly can be hermetically sealed, but organic getters are required because outgassing from the epoxy material may contaminate the system or optics within the system
Solution Approach 1:
The patent removes epoxy adhesive from the hermetic sealing process entirely, extracting the harmful outgassing source. Instead, it uses alternative mounting methods such as mechanical retention features, brazing, or welding that do not involve organic materials, thereby eliminating contamination while maintaining hermetic sealing capability
Solution Approach 2:
The patent introduces intermediary components such as hermetic seals, retention structures, or metallic bonding materials that mediate between the optical components and the hermetic enclosure. These intermediaries provide both mechanical support and hermetic sealing without the outgassing problems of epoxy adhesives
2Temperature
If laser diode bars are spaced to allow sufficient cooling, then heat dissipation is improved, but the device size and complexity increase
Solution Approach 1:
The patent replaces complex mechanical cooling systems with thermally conductive materials that passively conduct heat away from the laser diode bars. By using materials with high thermal conductivity in the mounting structure and housing, the system achieves effective heat dissipation without elaborate active cooling mechanisms
Solution Approach 2:
The patent changes the thermal parameters of the mounting structure by selecting materials with optimized thermal conductivity and designing thermal pathways that efficiently conduct heat from the laser diode bars to heat sinks or the housing, thereby improving heat dissipation while maintaining a compact design
3Reliability
If CTE matched materials are used to minimize thermal stress, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses materials with homogeneous and matched coefficients of thermal expansion (CTE) across different components. By selecting materials whose CTE values are closely matched (such as using Kovar for both the housing and mounting structures), the system minimizes thermal stress during temperature variations while maintaining reasonable manufacturing tolerances
Solution Approach 2:
The patent employs composite material structures that combine materials with complementary properties to achieve effective CTE matching. For example, it may use metal-ceramic composites or layered structures that provide both the desired thermal expansion characteristics and the necessary mechanical properties, thereby reducing thermal stress without requiring extremely tight manufacturing precision
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
This configuration provides a thermally stable, cost-effective, and reliable optical module that effectively manages thermal stresses and maintains hermetic sealing, ensuring efficient heat dissipation and precise optical alignment.
Implementation Method 1
a thermally conductive soft adhesive may be disposed between CTE matched elements of this subassembly
Implementation Method 2
stresses generated by a CTE mismatch between adjacent members are not transmitted to the laser chip through the thermally conductive soft adhesive
Implementation Method 3
A submount member having high thermal conductivity and a low CTE that substantially matches the low CTE of the laser chip
Implementation Method 4
a hard adhesive may be used to secure adjacent members with a substantial CTE mismatch
Data Source
AI summary
Embodiments are directed to laser emitter modules, or subassemblies thereof, and methods and devices for making or using the modules. Some module embodiments are configured to provide hermetically sealed enclosures that are thermally stable during use, highly reliable in adverse environments, convenient and cost effective to manufacture or any combination of the foregoing.