Light Source Frame Section Modulus for Thermal Stress Relief
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Solution Overview
Problem
The existing light source apparatuses face issues with the breakage or falling of light transmissive members due to thermal expansion mismatch between materials, leading to reliability concerns.
Innovation Solution
A light source apparatus design featuring a frame with a section modulus between 0.5 mm3 and 7.0 mm3, made of ceramic material, interposed between the base substrate and the light transmissive member, which reduces stress induced in the light transmissive member by having a coefficient of linear expansion intermediate to that of the base substrate and the light transmissive member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bonding is performed at high temperature using brazing or low-melting-point glass, then the components are bonded together, but the light transmissive member breaks or falls off due to thermal contraction
Solution Approach 1:
The patent changes the bonding method from high-temperature brazing or low-melting-point glass bonding to eutectic bonding at a lower temperature (400°C or lower). This parameter change in bonding temperature reduces the thermal contraction stress on the light transmissive member, preventing breakage while maintaining bonding strength through the eutectic reaction between the base substrate and frame.
Solution Approach 2:
The patent addresses thermal expansion mismatch by designing the frame with a specific cross-sectional shape that compensates for differential thermal contraction. The frame's geometry is optimized to reduce stress concentration on the light transmissive member during cooling from bonding temperature to operating temperature, preventing breakage due to thermal expansion differences between materials.
2Reliability
If the frame cross-sectional dimensions are increased to reduce stress, then the light transmissive member is protected from breakage, but the device size increases
Solution Approach 1:
The patent optimizes the frame cross-sectional dimensions to specific ranges (width: 0.5-3.0mm, height: 1.0-5.0mm) that provide sufficient stress reduction to prevent light transmissive member breakage while minimizing device size. These parameter values represent the optimal balance between mechanical protection and compact form factor.
Solution Approach 2:
The patent applies different cross-sectional dimensions to different portions of the frame based on local stress requirements. The frame cross-section is designed with varying width and height at different locations to provide enhanced stress reduction where needed while maintaining overall compactness, rather than uniformly increasing all dimensions.
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 effectively prevents the breakage or falling of the light transmissive member by maintaining stress below its maximum allowable stress, ensuring the reliability of the light source apparatus and subsequent projector systems.
Implementation Method 1
the frame is so dimensioned that a section modulus corresponding to a cross-sectional shape of the frame is greater than or equal to 0.5 mm3 but smaller than or equal to 7.0 mm3... a coefficient of linear expansion of the frame may be smaller than a coefficient of linear expansion of the base substrate but greater than a coefficient of linear expansion of the light transmissive member
Data Source
AI summary
A light source apparatus includes a base substrate made of a metal material, a plurality of light emitting devices provided on a first surface of the base substrate, a frame so provided on the first surface of the base substrate as to surround the plurality of light emitting devices, and a light transmissive member that is provided on a surface of the frame that is opposite the surface thereof on which the base substrate is provided and transmits light emitted from the plurality of light emitting devices, and the frame is so dimensioned that the section modulus corresponding to the cross-sectional shape of the frame is greater than or equal to 0.5 mm3 but smaller than or equal to 7.0 mm3.