Light Emitting Device Loop-Shaped Ceramic Stress Relief
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Solution Overview
Problem
Existing light-emitting device packages face reliability issues due to thermal stress caused by heat generation from light-emitting elements, leading to potential breakage or separation of glass members and degradation of hermetic properties, especially when multiple elements are mounted.
Innovation Solution
A light-emitting device package design featuring a metal package with a loop-shaped side wall, a ceramic member with a loop-shape, and a light-transmitting member bonded using a glass bonding material, where the ceramic member's loop-shape configuration reduces stress concentration and the bonding material is strategically placed to enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light-emitting elements are mounted in the package to increase functionality, then the device performance is improved, but thermal stress increases causing glass members to break or separate
Solution Approach 1:
A stress relief layer is introduced as an intermediary component between the glass member and the package substrate. This layer acts as a mediator that absorbs and distributes thermal stress, preventing direct stress transmission to the glass member and bonding interfaces, thereby maintaining hermetic sealing reliability even when multiple light-emitting elements generate significant heat
Solution Approach 2:
The package structure employs composite material design with multiple layers having different mechanical and thermal properties. The combination of glass member, stress relief layer, and package substrate creates a composite structure that balances thermal expansion coefficients and distributes stress, allowing the device to handle increased heat generation from multiple light-emitting elements without compromising sealing integrity
2Temperature
If metal package material is used to improve heat dissipation, then thermal conductivity is improved, but thermal expansion stress increases causing bonding material to separate
Solution Approach 1:
The package utilizes material parameter optimization by selecting metals with specific thermal expansion coefficients that match or closely align with the glass member and bonding material. This parameter matching reduces differential thermal expansion stress during temperature cycles, preventing bonding interface separation while maintaining effective heat dissipation through the metal package structure
Solution Approach 2:
The stress relief layer serves as a buffer intermediary between the metal package substrate and the glass member. This layer compensates for thermal expansion mismatches by deforming elastically under thermal stress, thereby protecting the bonding interfaces from stress-induced separation while allowing the metal substrate to perform its heat dissipation function
3Device complexity
If glass member is bonded directly to metal frame to simplify structure, then device complexity is reduced, but stress concentration occurs at bonding corners causing breakage
Solution Approach 1:
The stress relief layer is positioned as an intermediary between the metal frame and the glass member, specifically at the bonding interfaces. This layer distributes stress uniformly across the bonding area and eliminates stress concentration at corners, preventing glass member breakage while adding minimal structural complexity to the package design
Solution Approach 2:
The stress relief layer is strategically placed only at critical bonding regions where stress concentration occurs, rather than throughout the entire package structure. This localized approach provides stress relief where needed while minimizing additional complexity and material usage in non-critical areas
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 design improves the reliability of light-emitting devices by reducing stress on the bonding material and glass members, maintaining hermetic sealing and preventing dust ingress, even under increased heat generation from multiple light-emitting elements.
Implementation Method 1
bonded using a glass bonding material
Implementation Method 2
metal package with good thermal conductivity
Implementation Method 3
metal has a high thermal expansion coefficient. Thus, heat generated by operation of the light-emitting element causes thermal expansion of the package
Data Source
AI summary
A light-emitting device includes: a package made of a metal material and defining a recess, the package comprising a side wall defining a side of the recess; a plurality of light-emitting elements disposed in the recess; and a cover member disposed so as to close an opening of the recess, the cover member including: a light-transmitting member having a primary surface, a ceramic member having a loop-shape and having a first surface and a second surface opposite the first surface, the first surface bonded to the primary surface of the light-transmitting member via a bonding material, and a metal member having a loop-shape and including: a first portion bonded to the second surface of the ceramic member, and a second portion located outward of the first portion in a plan view and joined to an upper surface of the side wall of the package.