Optical Component Assembly With CTE-Matched Spacer and Compressive Joint
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Solution Overview
Problem
The mismatch in coefficients of thermal expansion (CTEs) between optical components and support components in free-space optical modules leads to high tensile stresses, potentially causing catastrophic failure or performance degradation due to thermal cycling, shock, or vibration.
Innovation Solution
An assembly comprising a first component with a first CTE, a second component with a second CTE, and a spacer with a third CTE matched to the first component, featuring a protrusion and complementary opening to create a compressive joint, along with an air gap to minimize thermo-mechanical distortion, thereby reducing tensile stresses and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If optical components are joined to a support component using adhesive, then the assembly is simple to manufacture, but CTE mismatch leads to high tensile stresses and potential catastrophic failure
Solution Approach 1:
A spacer component with intermediate CTE is introduced between the optical component (first CTE) and the support component (second CTE). The spacer's CTE is substantially matched to the optical component, creating a CTE gradient that reduces thermal stress. This intermediary element acts as a buffer that accommodates differential thermal expansion while maintaining reliable joints.
Solution Approach 2:
The invention changes the CTE parameter of the spacer material to be substantially matched to the optical component's CTE, rather than using a material with low CTE like traditional support components. This parameter selection reduces the CTE mismatch and associated tensile stresses in the adhesive joints.
2Reliability
If a spacer with intermediate CTE is used between optical component and support component, then CTE mismatch is reduced, but the device complexity increases
Solution Approach 1:
The spacer integrates multiple functions: it provides mechanical support, accommodates thermal expansion differences, and positions the optical component. By combining these functions into a single component with protrusions and complementary openings, the design reduces overall assembly complexity despite adding a spacer element.
Solution Approach 2:
The spacer features localized geometric variations including protrusions and complementary openings at specific locations. These local structural features enable precise positioning and secure mechanical attachment while maintaining the overall simple spacer geometry. The local quality variations allow the spacer to perform multiple functions without requiring a complex overall structure.
3Ease of manufacture
If planar adhesive joints are used to join spacers and components, then the assembly is simple to manufacture, but the joints are vulnerable to tensile stress from CTE mismatch
Solution Approach 1:
The spacer includes pre-formed protrusions and complementary openings that are designed to create compressive stress in the adhesive joints during assembly. This preliminary structural design ensures that the joints are pre-stressed in compression, which strengthens them against subsequent tensile stresses from thermal cycling before the actual thermal loading occurs.
Solution Approach 2:
The geometric features of the spacer (protrusions and complementary openings) are designed to generate compressive stress that counteracts the anticipated tensile stress from CTE mismatch. This preliminary anti-action prepares the joints to resist the harmful tensile forces that will arise during thermal cycling, preventing catastrophic failure.
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 high thermo-mechanical stability by reducing tensile stresses and maintaining the central wavelength of optical channels within a narrow band over varying temperatures, minimizing insertion loss and preventing performance degradation.
Implementation Method 1
The CTE mismatch between the optical components and the support component may lead to high tensile stresses in the optical components... The spacer, disposed between the first component and the second component, having a third CTE substantially matched to the first CTE
Implementation Method 2
one of a protrusion and a complementary opening for receiving the protrusion... such that a joint between the protrusion and the complementary opening is under compressive stress
Implementation Method 3
an air gap, disposed between the first component and the protrusion
Data Source
AI summary
A component assembly includes a first component, such as an optical component, and a second component, such as a support component, having different coefficients of thermal expansion (CTEs). The component assembly also includes a spacer having a CTE matched to that of the first component, disposed between the first component and the second component. When the CTE of the first component is greater than that of the second component, the second component includes a protrusion, and the spacer includes a complementary opening for receiving the protrusion, such that a joint between the protrusion and the complementary opening is under compressive stress. The spacer also includes a mounting area for receiving the first component, and an air gap disposed between the first component and the protrusion.