Optical Component Bond Structure for Thermal Stress Relief
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Solution Overview
Problem
Optical components face issues with thermal stress-induced cracking and peeling at the bonded interface between transparent sealing members and substrates due to differences in thermal expansion coefficients, particularly during high-temperature operations like reflow processes.
Innovation Solution
Incorporation of stress relaxation layers with a Young's modulus of less than or equal to 150 GPa and a thickness of at least 1.2 μm, accompanied by diffusion prevention layers on both sides, to prevent metal interdiffusion and maintain effective stress relaxation, thereby enhancing the durability of the bonded interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallized layer is provided on quartz glass and substrate to bond with solder, then bonding is achieved, but sufficient stress relaxation effect cannot be obtained
Solution Approach 1:
The metallized layer is divided into multiple functional layers: a base layer for bonding and a stress relaxation layer with specific properties (Young's modulus of 50-150 GPa, thickness of 1-10 μm) positioned between the base layer and the transparent sealing member. This segmentation allows each layer to perform its specific function independently, achieving both strong bonding and effective stress relaxation.
Solution Approach 2:
Different regions of the metallized layer have different properties: the base layer provides bonding strength while the stress relaxation layer provides stress relief. The stress relaxation layer is specifically positioned at the interface where thermal stress occurs, providing localized stress management without compromising overall bonding strength.
2Reliability
If a Au film is provided as a stress relaxation layer to avoid cracking, then cracking is prevented, but interdiffusion with Sn-containing solder causes deterioration
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the stress relaxation layer and the solder layer. This barrier layer prevents interdiffusion between the Au film and Sn-containing solder, maintaining the compositional stability of the stress relaxation layer while allowing it to continue providing crack prevention functionality.
Solution Approach 2:
The metallized layer is constructed as a composite structure combining multiple materials: Au or Ag for stress relaxation, diffusion barrier materials (such as Pd, Pt, or Ni) to prevent interdiffusion, and solder-compatible layers. This composite structure achieves both stress relaxation and compositional stability simultaneously.
3Reliability
If the transparent sealing member is bonded to substrate, then sealing is achieved, but thermal stress causes peeling off or damage
Solution Approach 1:
The Young's modulus of the stress relaxation layer is specifically controlled to be between 50-150 GPa, which is lower than typical metallized layers. This parameter change allows the layer to deform more easily under thermal stress, absorbing expansion differences between the transparent sealing member and substrate, thereby preventing peeling and damage while maintaining sealing integrity.
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 effectively suppresses peeling and damage to the transparent sealing member by maintaining a sufficient stress relaxation effect, even under thermal stress conditions, ensuring the integrity of the optical component.
Implementation Method 1
a bonded portion in which a plurality of metal films are laminated, and which is configured to bond the transparent sealing member and the substrate, wherein the bonded portion includes one or more stress relaxation layers constituted by one or more metal films having a Young's modulus of less than or equal to 150 GPa
Implementation Method 2
a diffusion prevention layer disposed on each of both sides in a thickness direction of each of the stress relaxation layers, and configured to prevent diffusion of metal constituting the stress relaxation layer
Data Source
AI summary
An optical component including: a substrate on which an optical element is mounted; a transparent sealing member disposed above the substrate and configured to seal the optical element; and a bonded portion in which a plurality of metal films are laminated, and which is configured to bond the transparent sealing member and the substrate. The bonded portion includes: one or more stress relaxation layers constituted by one or more metal films having a Young's modulus of less than or equal to 150 GPa, the one or more stress relaxation layers having a total thickness of greater than or equal to 1.2 μm; and a diffusion prevention layer disposed on each of both sides in a thickness direction of each of the one or more stress relaxation layers, and configured to prevent diffusion of metal constituting the stress relaxation layer.