Light Emitting Device Through-Hole Reflective Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light emitting devices suffer from degraded light extraction efficiency due to absorption of emitted light by inner peripheral walls of through-holes in wiring boards and are prone to bonding wire failure from thermal stress caused by light-reflecting resins with low thermal expansion coefficients.
Innovation Solution
A light emitting device design featuring a heat dissipative board, a wiring board with a through-hole, a light-emitting element, and a light-reflecting member that covers the inner peripheral wall of the through-hole excluding the light-emitting element and bonding wire, preventing light absorption and thermal stress on the bonding wire, while using high optical reflectance and thermal conductivity materials to enhance light extraction and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the inner peripheral wall of the through-hole is left exposed, then the structure is simple, but light emitted from the side surface of the light-emitting element is absorbed by the inner peripheral wall surface, degrading light extraction efficiency
Solution Approach 1:
The patent converts the harmful light-absorbing inner peripheral wall into a beneficial light-reflecting surface by coating it with a light-reflecting material. This transforms the originally harmful absorption effect into a useful reflection effect that redirects light toward the extraction direction, thereby improving light extraction efficiency while maintaining the simplicity of the through-hole structure.
Solution Approach 2:
The patent applies light-reflecting material specifically to the inner peripheral wall surface of the through-hole, creating a localized functional area with different optical properties. This local modification targets precisely where light absorption occurs, improving light extraction efficiency without requiring changes to the entire device structure.
2Productivity
If light-reflecting resin with low thermal expansion coefficient is used to cover the inner peripheral wall, then light extraction efficiency is improved, but thermal stress is applied to the bonding wire when heated, causing the bonding wire to be easily cut off
Solution Approach 1:
The patent extracts the light-reflecting function from the bonding wire's environment by applying light-reflecting material only to the inner peripheral wall surface, deliberately excluding the bonding wire from this coating. This separation allows the bonding wire to remain free from thermal stress caused by the light-reflecting resin, preventing wire cutoff while still achieving improved light extraction efficiency.
Solution Approach 2:
The patent creates a localized light-reflecting coating on the inner peripheral wall that deliberately excludes the bonding wire area. This localized application ensures that the light-reflecting material improves light extraction where needed while avoiding contact with the bonding wire, thereby preventing thermal stress-induced wire failure.
3Productivity
If the light-reflecting member covers the entire inner peripheral wall including bonding wire area, then light extraction efficiency is maximized, but the bonding wire is exposed to thermal stress and may be cut off
Solution Approach 1:
The patent extracts the bonding wire from the light-reflecting coating area, creating an exclusion zone around the wire. This allows the light-reflecting member to cover the maximum possible inner peripheral wall surface for optimal light extraction while deliberately leaving the bonding wire area uncovered, thereby eliminating thermal stress exposure.
Solution Approach 2:
The patent creates a non-uniform light-reflecting coating distribution where the inner peripheral wall surface has high light-reflecting coverage for maximum light extraction efficiency, while the bonding wire area maintains a light-reflecting-free zone to protect the wire from thermal stress. This localized differentiation resolves the contradiction between maximizing light extraction and protecting the bonding wire.
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 significantly improves light extraction efficiency by reflecting light outward and prevents bonding wire failure, ensuring reliable operation by reducing thermal stress and effectively dissipating heat generated by the light-emitting elements.
Implementation Method 1
the light is reflected by the light-reflecting member and is emitted outwardly from an opening side of the through-hole of the wiring board
Implementation Method 2
a heat dissipative board, a wiring board adhering to and fixed to the heat dissipative board
Data Source
AI summary
A light emitting device includes: a heat dissipative board; a wiring board which adheres and is fixed to the heat dissipative board and in which a through-hole is formed; a light-emitting element which is mounted on a front surface of the heat dissipative board which is exposed through the through-hole of the wiring board; a bonding wire which connects the light-emitting element and the wiring board; and a light-reflecting member which covers a surface of an inner peripheral wall of the through-hole excluding disposition places of the light-emitting element and the bonding wire.