Glass Substrate LED Package Thermal Expansion Match
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Solution Overview
Problem
Glass-sealed LED packages face reliability issues due to cracks caused by differences in linear expansion coefficients between the sealing glass and ceramic or glass substrates, leading to potential heat and light deterioration.
Innovation Solution
A glass substrate with a linear expansion coefficient matching 0.9 to 1.1 times that of the sealing glass is used, along with a higher softening point than the sealing glass, to prevent cracking and ensure accurate sealing, while allowing for easy glass sealing and light emission in all directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a ceramic substrate is used, then the substrate provides good mechanical strength and electrical insulation, but cracks occur in the sealing glass or ceramic substrate due to difference in linear expansion coefficient
Solution Approach 1:
The patent changes the material parameter of the substrate from ceramic to glass, and specifically selects glass with a linear expansion coefficient within 0.9 to 1.1 times that of the sealing glass. This parameter matching resolves the thermal expansion mismatch that causes cracking during temperature cycling, while maintaining mechanical strength through proper glass material selection.
Solution Approach 2:
The patent uses glass substrate and sealing glass made of the same or similar material composition, creating material homogeneity. This ensures compatible thermal expansion characteristics and chemical stability, eliminating the interfacial cracking problem that occurs between dissimilar materials like ceramic and glass.
2Reliability
If glass substrate is used, then cracks are suppressed due to matched linear expansion coefficient, but the softening point must be higher than sealing glass for accurate sealing
Solution Approach 1:
The patent carefully selects glass materials with specific parameter combinations: linear expansion coefficient within 0.9 to 1.1 times that of sealing glass for crack suppression, and softening point higher than sealing glass for sealing accuracy. This dual parameter optimization resolves the apparent contradiction between reliability and manufacturing precision.
Solution Approach 2:
The substrate is designed with pre-determined material properties before the sealing process. The glass substrate is selected in advance with the appropriate softening point and expansion coefficient characteristics, ensuring that when sealing occurs, the material parameters are already optimized for both crack prevention and sealing accuracy.
3Reliability
If wiring pattern is formed on substrate, then electrical connection is achieved, but substrate shape and structure are constrained
Solution Approach 1:
The patent separates the electrical connection function from the substrate structure by using distinct wiring patterns formed on the glass substrate surface. This segmentation allows the substrate to maintain its flexible glass material properties and various shapes, while the wiring pattern provides the necessary electrical connectivity without constraining the substrate's form.
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 reliability and durability of the LED package by preventing cracks and ensuring consistent light emission in all directions without heat or light-induced deterioration.
Implementation Method 1
the linear expansion coefficient of the substrate is 0.9 times to 1.1 times the linear expansion coefficient of the sealing glass
Implementation Method 2
the softening point of the substrate is higher than that of the sealing glass
Data Source
AI summary
To prevent cracks on a sealing glass or a substrate in a LED package in which a light-emitting device is sealed with a sealing glass. The LED package comprises a substrate, a LED mounted on the substrate, and a sealing glass for sealing a LED formed on the substrate. A wiring pattern being connected to an electrode of the LED is formed on the surface of the substrate. A back electrode pattern is formed on the rear surface of the substrate. A columnar via is formed in the substrate. Thus, the wiring pattern on the surface of the substrate and the back electrode pattern on the rear surface of the substrate are electrically connected. A softening point of the substrate is set higher than softening point of the sealing glass.