Light Emitting Package with Conformal Shell and Air Gap
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Solution Overview
Problem
Existing light emitting packages are prone to damage, complex in manufacturing, and costly due to soft encapsulants and separately fabricated microlenses, and multiple chip packages increase complexity without desired illumination focus.
Innovation Solution
A light emitting package design featuring a light transmissive encapsulant over light emitting chips on a board, with a conformal shell having an air gap and remote phosphor for wavelength conversion, and enhanced heat sinking using thermally conductive materials to manage thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If soft molded encapsulants are used, then light extraction is improved, but reliability deteriorates due to damage from abrasion and corrosive chemicals
Solution Approach 1:
The encapsulation system is divided into two distinct layers: a hard molded encapsulant providing mechanical protection and chemical resistance, and a soft conformal layer providing light extraction enhancement. This segmentation allows each layer to specialize in its respective function without compromising the other.
Solution Approach 2:
The encapsulation structure uses a composite of a hard molded material (such as epoxy or silicone) and a soft conformal material (such as a gel or adhesive with higher refractive index), combining the advantages of both materials to achieve simultaneous mechanical durability and optical performance.
2Strength
If separately fabricated microlenses are used, then robustness is improved, but device complexity increases due to careful placement requirements
Solution Approach 1:
The microlens function is merged into the conformal encapsulant layer itself, which is applied directly over the chip array. This eliminates the need for separate microlens fabrication and placement steps, reducing manufacturing complexity while maintaining the optical focusing benefits.
Solution Approach 2:
The conformal encapsulant layer serves multiple functions simultaneously: it provides mechanical protection, enhances light extraction through its optical properties, and acts as the microlens structure for focusing light. This multi-functionality reduces the overall device complexity.
3Illumination intensity
If multiple chip packages are used, then illumination output is improved, but device complexity increases
Solution Approach 1:
Multiple light-emitting chips are combined into a single package with a common molded encapsulant and conformal layer, allowing them to function as an integrated illumination unit. This approach increases total light output while managing complexity through standardized packaging.
Solution Approach 2:
The single molded encapsulant and conformal layer structure serves all chips simultaneously, providing unified mechanical protection, optical enhancement, and thermal management. This multi-functional approach handles multiple chips without proportionally increasing package complexity.
4Shape
If focusing lens is used, then light directionality is improved, but ease of operation deteriorates as focusing is not desired for illumination
Solution Approach 1:
The conformal encapsulant layer provides localized optical enhancement at each chip location, improving light extraction efficiency without creating strong directional focusing. This local quality approach maintains illumination uniformity while enhancing overall light output.
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 design improves manufacturability, reliability, and reduces thermal degradation while maintaining efficient light extraction and conversion, achieving robust and efficient illumination with improved thermal management.
Implementation Method 1
the chip or chips emit ultraviolet or violet radiation, and the remote phosphor converts the radiation to visible light that approximates white light
Implementation Method 2
A light transmissive generally conformal shell is disposed over the light transmissive encapsulant and has an inner surface spaced apart by an air gap from and generally conformal with an outer surface of the light transmissive encapsulant
Data Source
AI summary
In a light emitting package (8), at least one light emitting chip (12, 14, 16, 18) is supported by a board (10). A light transmissive encapsulant (30) is disposed over the at least one light emitting chip and over a footprint area (32) of the board. A light transmissive generally conformal shell (40) is disposed over the encapsulant and has an inner surface (44) spaced apart by an air gap (G) from, and generally conformal with, an outer surface (34) of the encapsulant. At least one phosphor (50) is disposed on or embedded in the conformal shell to output converted light responsive to irradiation by the at least one light emitting chip. A thermally conductive filler material disposed in the generally conformal shell (40) is effective to enhance a thermal conductivity of the composite shell material to a value higher than 0.3 W/(m·K).