Semiconductor LED Lid Sealing with Eutectic Solder
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Solution Overview
Problem
The semiconductor light-emitting device experiences peeling of the glass lid from the inorganic material substrate due to a significant difference in thermal expansion coefficients, leading to reliability issues over time.
Innovation Solution
A semiconductor light-emitting device is designed with a substrate and a lid member having different thermal expansion coefficients, where a eutectic alloy solder, specifically AuSn solder, is used as a joining member to seal the semiconductor light-emitting element, and heat-treated at 160° C. to 210° C. for a predetermined time to mitigate thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass lid made of silica glass is used to seal the LED element on an inorganic material substrate, then the sealing function is achieved, but the glass lid peels from the substrate over time due to thermal expansion coefficient mismatch
Solution Approach 1:
A joining member comprising a eutectic alloy solder is introduced as an intermediary between the glass lid and the inorganic material substrate. This joining member has a thermal expansion coefficient that is intermediate between those of the glass lid and substrate, and its melting point is lower than both their thermal expansion differential stress thresholds. The joining member absorbs thermal stress through plastic deformation and phase transition, preventing peeling while maintaining sealing reliability.
2Device complexity
If the glass lid is directly attached to the inorganic material substrate, then the structure is simple, but residual stress causes peeling after a certain time
Solution Approach 1:
The joining member acts as a mediator that accommodates the thermal expansion mismatch between the glass lid and inorganic substrate. By selecting a eutectic alloy solder with appropriate mechanical properties and intermediate thermal expansion characteristics, the joining member absorbs residual stress through controlled deformation, thereby maintaining bonding reliability without significantly increasing structural complexity.
Solution Approach 2:
The invention changes the material parameter (thermal expansion coefficient) of the joining layer to be intermediate between the glass lid and substrate. Additionally, the joining member's melting point parameter is selected to be lower than the thermal stress threshold, enabling stress relief through phase transition at elevated temperatures, thus preventing peeling while maintaining structural integrity.
3Adaptability or versatility
If materials with different thermal expansion coefficients are used for the substrate and lid member, then functional requirements are met, but thermal stress accumulates over time
Solution Approach 1:
The joining member serves as a stress-absorbing intermediary that decouples the thermal expansion mismatch between the glass lid and inorganic substrate. The eutectic alloy solder's intermediate thermal expansion coefficient and low melting point enable it to absorb thermal stress through plastic deformation and phase transition, protecting the bonded structure from stress-induced failure while preserving material selection flexibility.
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 prevents peeling of the glass lid from the inorganic material substrate, ensuring the semiconductor light-emitting device's reliability by releasing residual stress caused by thermal expansion differences.
Implementation Method 1
the joining member comprises a eutectic alloy solder
Implementation Method 2
heat-treating an AuSn solder as the eutectic alloy solder at a temperature of 160° C. to 210° C.
Implementation Method 3
heat-treating an AuSn solder as the eutectic alloy solder at a temperature of 160° C. to 210° C. for a predetermined time
Implementation Method 4
residual stress due to a difference in thermal expansion coefficient acts between the glass lid and the inorganic material substrate
Data Source
AI summary
A semiconductor light-emitting device includes a substrate on which a semiconductor light-emitting element is mounted, the substrate having a first coefficient of thermal expansion, a lid member that covers the semiconductor light-emitting element, the lid member having a second coefficient of thermal expansion smaller than the first coefficient of thermal expansion, and a joining member that joins the lid member to the substrate to seal the semiconductor light-emitting element. The joining member includes a eutectic alloy solder.