LED Mounting Board Clearance and Resin Gradient for Wire Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-power LED devices face reliability issues due to thermal expansion causing cracks and peeling in the sealing resin, and subsequent breakage of bonding wires, which reduces the device's reliability.
Innovation Solution
The design includes a metal-made reflector and mounting board with an insulating board having a window hole larger than the LED chip, where the bonding wires straddle a narrower clearance and are optionally formed in a coil shape or filled with a resin of lower expansion coefficient, and the sealing resin is applied to cover the LED and conductor, minimizing expansion-induced stress on the wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicone-based resin is used for sealing material to avoid cracks and peeling, then reliability against thermal expansion is improved, but bonding wires are pulled and broken due to large expansion in the direction away from the board
Solution Approach 1:
The patent applies different properties to different regions of the sealing resin. The resin has high elasticity (large coefficient of linear expansion) in regions away from the board to accommodate thermal expansion without cracking, while having lower elasticity (smaller coefficient of linear expansion) in regions near the board to minimize pulling force on bonding wires. This local differentiation resolves the contradiction between preventing resin cracks and protecting bonding wires.
Solution Approach 2:
The patent changes the physical parameters of the sealing resin by creating a gradient in its elastic properties. By controlling the coefficient of linear expansion to vary with distance from the board, the resin transitions from a highly elastic state far from the board to a less elastic state near the board, optimizing performance for both crack prevention and wire protection.
2Stability of the object's composition
If the sealing resin has large coefficient of linear expansion to match thermal expansion, then cracks and peeling are avoided, but bonding wires are pulled and broken due to expansion away from the board
Solution Approach 1:
The sealing resin is designed with spatially varying elastic properties. Regions farther from the board maintain high elasticity to prevent cracking under thermal expansion, while regions closer to the board have reduced elasticity to minimize expansion forces acting on bonding wires, thereby protecting wire reliability.
Solution Approach 2:
The sealing resin acts as an intermediary material with graded properties between the rigid board structure and the expanding reflector. By transitioning from high to low elasticity with decreasing distance from the board, it mediates the thermal expansion forces, preventing both resin failure and wire damage.
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 reduces the likelihood of bonding wire breakage and enhances the reliability of the LED device by managing thermal expansion and stress on the wires effectively.
Implementation Method 1
when heat is generated while the LED is turned on, it is anticipated that sealing resin material 5 fitted within reflector 3 will largely expand in the direction in which it moves away from board 2
Data Source
AI summary
A light emitting device includes a light emitting element (LEE) on a mounting board, a metal reflector surrounding the side surfaces of the LEE on the mounting board, a conductor electrically connecting the LEE with the mounting board, and a sealing resin fitted within the reflector to cover and seal the LEE and the conductor. The mounting board includes a metal baseboard, and an insulating board laminated on the base board with a window hole larger than the outer periphery of the LEE. A mount for the LEE is on the base board within the window hole with a clearance defined from window hole side surfaces. The conductor straddles the clearance, and electrically connects the wiring pattern on the insulating board with the LEE and mount. Part of the clearance associated with the area that projects from the conductor to the mounting board is narrower than the remainder.