Optical Semiconductor Sealing Structure for Thermal Stress Management
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Solution Overview
Problem
The challenge is to create a reliable sealing structure for optical semiconductor apparatuses where the package substrate and window member have different coefficients of thermal expansion, limiting the selection of materials and affecting the eutectic bonding process.
Innovation Solution
A sealing structure is implemented with a first metal layer on the package substrate and a second metal layer on the window member, where the narrower metal layer is positioned within the wider one, increasing the overlap area and bonding range, and using a gold-tin (AuSn) metal bonding part to prevent stress-induced cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If materials with different coefficients of thermal expansion are used for the package substrate and window member, then the transmittance of the emission wavelength can be optimized, but the sealing reliability deteriorates due to thermal stress
Solution Approach 1:
The sealing structure is divided into multiple metal layers (first metal layer on package substrate, second metal layer on window member) with a metal bonding part in between. This segmentation allows each layer to accommodate thermal expansion independently while maintaining overall sealing integrity, resolving the contradiction between using materials with different thermal expansion coefficients and maintaining sealing reliability.
Solution Approach 2:
The second metal layer is positioned within the region of the first metal layer, creating a nested configuration. This nesting ensures that the entire sealing interface is covered and bonded, maximizing the bonding area and distributing thermal stress evenly across the overlapping region, thereby maintaining sealing reliability despite differential thermal expansion.
2Ease of manufacture
If the metal layers are positioned out of alignment, then the manufacturing process is simpler, but the sealing performance deteriorates due to reduced overlap area
Solution Approach 1:
The design specifies that the entirety of one metal layer is positioned in a region where the other metal layer is provided, creating a nested doll configuration. This ensures maximum overlap area regardless of minor alignment variations, maintaining sealing performance while allowing for simpler manufacturing processes with less stringent alignment requirements.
Solution Approach 2:
The nested configuration of metal layers provides a built-in margin of error that cushions against alignment variations. By designing the layers to overlap completely rather than requiring precise edge-to-edge alignment, the structure beforehand compensates for potential misalignment, ensuring sealing performance is maintained.
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 enhances the sealing performance and reliability of the optical semiconductor apparatus by maximizing the overlap area of the metal layers, reducing the formation of thin fillets that can cause stress-related issues, and maintaining airtightness even with materials having different thermal expansion coefficients.
Implementation Method 1
a metal bonding part provided between the first metal layer and the second metal layer
Data Source
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AI summary
An optical semiconductor apparatus (10) includes: a package substrate (30); a light emitting device (20) housed in a recess (34) of the package substrate; a window member (40) provided to cover an opening of the recess (34); and a sealing structure (50) that seals a space between the package substrate (30) and the window member (40). The sealing structure (50) includes a first metal layer (51) provided on the package substrate, a second metal layer (52) provided on the window member (40), and a metal bonding part (53) provided between the first and second metal layers. An entirety of one of the first and second metal layers (51, 52) is positioned in a region where the other of the first and second metal layers (51, 52) is provided.