PLCC Red LED Assembly with Refractive Index Filler
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Solution Overview
Problem
Red LEDs for plant lighting fixtures packaged using the PLCC method have low light transmittance, failing to meet the requirements for effective red light promotion of plant growth due to their inferior light efficiency compared to ceramic packages.
Innovation Solution
A red LED assembly with a plastic leaded chip carrier package that includes a substrate, an LED module with a chip holder and optical encapsulant, and a filler material with a refractive index greater than air, which enhances light transmittance by reducing total internal reflection and improving heat dissipation through a vertical package structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PLCC packaging method is used for red LEDs, then manufacturing cost is reduced, but light transmittance deteriorates
Solution Approach 1:
A filler material with refractive index between 1.4 and 1.7 is introduced as an intermediary substance between the LED chip and lens. This filler material mediates the optical interaction by reducing total internal reflection at interfaces, thereby improving light extraction efficiency and transmittance while maintaining the cost-effective PLCC packaging structure.
Solution Approach 2:
The refractive index parameter of the medium surrounding the LED chip is optimized by selecting filler materials with specific refractive indices (1.4-1.7). This parameter change reduces the refractive index difference between the optical encapsulant and surrounding medium, minimizing total internal reflection and improving light transmittance without changing the basic PLCC packaging structure.
2Ease of manufacture
If PLCC packaging method is used for red LEDs, then manufacturing cost is reduced, but light efficiency deteriorates
Solution Approach 1:
The filler material acts as an optical intermediary that reduces energy loss by minimizing total internal reflection. This allows more light energy to be extracted from the LED chip and transmitted through the lens, improving overall light efficiency while maintaining the economical PLCC packaging approach.
Solution Approach 2:
The invention converts the harmful effect of total internal reflection (which causes light energy loss) into a beneficial outcome by using the filler material to control refraction. The refractive index mismatch that initially causes reflection is optimized to improve light extraction, turning a potential loss mechanism into an efficiency-enhancing feature.
3Temperature
If vertical package structure is used, then heat dissipation is improved, but structural complexity increases
Solution Approach 1:
The invention adopts a vertical package structure that changes the thermal conduction direction from horizontal to vertical. The heat dissipation path is extended in the vertical dimension through the substrate and heat sink structure, improving thermal management effectiveness without significantly increasing horizontal structural complexity.
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 increases light efficiency and luminous flux, making it suitable for plant growth promotion while maintaining the cost advantages of PLCC packaging.
Implementation Method 1
a filler material which has a refractive index greater than that of air and which fills the space between the LED module and the inner surface of the lens portion
Implementation Method 2
enhances light transmittance by reducing total internal reflection
Implementation Method 3
an LED chip for emitting red light mounted on the chip holder
Implementation Method 4
Light emitting diodes (referred to below as LEDs) are widely used in lighting fixtures for promoting the growth of plants
Data Source
AI summary
An LED assembly includes a substrate, an LED module mounted on the substrate, and a lens plate disposed on the substrate. The lens plate has a lens portion disposed atop the LED module and defining a space between an inner surface of the lens portion and the LED module. A filler material having a refractive index greater than air fills the space between the LED module and the inner surface of the lens portion. The LED module includes a chip holder mounted on the substrate, a red LED chip mounted on the chip holder, and an optical encapsulant covering the top surface of the LED chip. The LED module is a plastic leaded chip carrier package. The refractive index of the filler material preferably differs from the refractive index of the optical encapsulant by at most ±0.3.