Beveled Chip Reflector for CSP LED Light Extraction
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Solution Overview
Problem
The manufacturing techniques for chip-scale packaging (CSP) LEDs face challenges in achieving high luminous efficacy due to light energy loss caused by the reflective structure design, which results in reduced overall efficiency and larger thermal resistance.
Innovation Solution
A CSP LED design incorporating a flip-chip light-emitting semiconductor die, a photoluminescent layer, a chip-side-spacer structure with a beveled side-spacer-edge surface, and a reflective structure that covers the side-spacer-edge surface, optimized for batch mass-production, enhances light extraction and reduces thermal impact through a remote phosphor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reflective structure is added to surround the light-emitting semiconductor die in CSP LED, then light extraction efficiency is improved, but manufacturing complexity and thermal resistance increase
Solution Approach 1:
The patent merges the reflective structure formation into the mold compound injection process itself. The mold compound is injected to automatically form the reflective structure with the cavity wall, eliminating the need for separate reflective structure fabrication and assembly steps. This integration reduces manufacturing complexity while maintaining the light extraction efficiency benefits.
Solution Approach 2:
The mold compound serves multiple functions: it provides structural packaging, thermal management, and simultaneously forms the reflective structure that enhances light extraction. This multi-functionality reduces the number of separate components needed, simplifying manufacturing while improving luminous efficacy.
2Use of energy by moving object
If a reflective structure is added to surround the light-emitting semiconductor die in CSP LED, then light extraction efficiency is improved, but thermal resistance increases
Solution Approach 1:
The reflective structure is formed locally at the cavity wall where it is most needed for light extraction, rather than as a comprehensive thermal barrier. The mold compound material is selected to provide adequate thermal conduction while the reflective geometry is optimized to minimize interference with thermal pathways from the semiconductor die to the heat sink.
Solution Approach 2:
The patent optimizes the geometric parameters of the reflective structure (angle, depth, surface area) to maximize light extraction efficiency while minimizing thermal resistance. By carefully controlling the cavity geometry and reflective surface properties, the design achieves high luminous efficacy without significant thermal penalty.
3Volume of moving object
If the package size is reduced to achieve chip-scale packaging, then material cost and thermal resistance are reduced, but light extraction efficiency decreases
Solution Approach 1:
The patent utilizes the three-dimensional cavity structure created by the mold compound injection to provide reflective surfaces that extract light from multiple angles and depths. This 3D reflective geometry compensates for the reduced package size by creating more efficient light extraction pathways within the limited volume, maintaining high luminous efficacy in a compact form factor.
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 increases luminous efficacy by guiding laterally radiated light towards the top surface, reducing light loss, and improving thermal management, while maintaining a small form factor and low production costs.
Implementation Method 1
a reflective structure that covers the side-spacer-edge surface... guiding laterally radiated light towards the top surface
Implementation Method 2
a photoluminescent layer... covering the light-emitting semiconductor die
Data Source
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Figure 3A
AI summary
A chip-scale packaging (CSP) light-emitting device (LED), including a light-emitting semiconductor die, a photoluminescent layer, a chip-side-spacer structure, and a beveled chip reflective structure, is disclosed. The beveled reflective structure is disposed surrounding the chip-edge surfaces of the light-emitting semiconductor die, wherein the chip-side-spacer structure is disposed between the beveled reflective structure and the chip-edge surfaces of the light-emitting semiconductor die. A manufacturing method to fabricate the CSP LED is also disclosed. The CSP LED with a beveled chip reflector can effectively reflect the light radiated from the light-emitting semiconductor die toward the photoluminescent layer so that the light extraction efficiency is improved.