LED Packages With Insulated Emitter Surfaces
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Solution Overview
Problem
Existing LED packages fail to meet UL 8750 class 4 ratings due to inadequate lens adhesion and electrical insulation, leading to potential shock and fire hazards, especially when the lens is removed or sheared off, as they do not maintain sufficient electrical insulation and physical integrity under applied forces.
Innovation Solution
Incorporating an insulating layer between the emitter and the encapsulant, and potentially on the submount surfaces, to ensure electrical isolation and retain the insulating layer even if the encapsulant or lens is removed, using materials like SiO2, SiN, or parylene, which are transparent to light and provide sufficient thickness for electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an LED emitter with conductive substrate (e.g., SiC) is used, then electrical conductivity and light emission are achieved, but electrical insulation and safety are compromised when lens is removed
Solution Approach 1:
An insulating layer is introduced as an intermediary between the conductive emitter substrate and the external environment. This layer mediates the electrical insulation requirement while allowing the conductive substrate to maintain its light-emitting function, thereby eliminating shock hazards without compromising electrical performance
Solution Approach 2:
A thin insulating film is applied to the emitter substrate surface. This thin film provides sufficient electrical insulation to prevent shock hazards while maintaining the structural integrity and light-emitting capabilities of the LED package
2Ease of manufacture
If lens adhesion is weakened to use cheaper materials, then manufacturing cost is reduced, but lens retention and safety rating are compromised
Solution Approach 1:
The insulating layer serves as an intermediary between the emitter and encapsulant, providing a stable interface that maintains lens retention without requiring expensive high-adhesion materials. This layer ensures the lens remains securely attached while allowing the use of cost-effective encapsulant materials
3Reliability
If insulating layer thickness is increased to improve electrical isolation, then safety is enhanced, but light transmission and optical efficiency are reduced
Solution Approach 1:
The thickness of the insulating layer is optimized to a specific parameter range that provides sufficient electrical isolation (meeting safety standards) while maintaining adequate light transmission. This parameter optimization balances safety requirements with optical efficiency, preventing excessive thickness that would block light
4Device complexity
If conventional LED packaging without insulating layer is used, then device complexity is reduced, but UL 8750 class 4 rating and safety are not achieved
Solution Approach 1:
The LED package structure is segmented into distinct functional layers: the conductive emitter substrate, the insulating layer, and the encapsulant. This segmentation allows each layer to perform its specific function (light emission, electrical insulation, and protection) while collectively achieving the UL 8750 class 4 safety rating without excessive 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 insulating layer prevents electrical conduction and shock hazards, enabling LED packages to pass the UL 8750 class 4 rating by maintaining insulation and adhesion, even under mechanical stress, thus enhancing safety and efficiency by allowing the use of cheaper, more optically efficient materials in fixtures.
Implementation Method 1
an electrically insulating layer between the emitter and the encapsulant
Implementation Method 2
materials like SiO2, SiN, or parylene, which are transparent to light
Data Source
AI summary
Emitter packages are disclosed that can include an insulating layer covering the emitter, such as between the emitter's primary emission surface and a lens or encapsulant. The packages can comprise a submount with an emitter flip-chip mounted such that the diode region is between the emitter's non-insulating and/or conductive substrate and the submount. The submount can then be covered with a thin insulating layer. The same or another insulating layer can cover other electrically active surfaces on the submount. By insulating the electrically active surfaces of the emitter and, in some embodiments, other electrically active surfaces, the package can meet UL8750 class 4 enclosure standards even if it does not meet the lens adhesion criteria. This can enable the use of cheaper and/or more optically efficient materials at the fixture level, since the package itself meets class 4 standards.