Raised LED Substrate with Relief Surface for Phosphor Meniscus Control
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Solution Overview
Problem
Conventional methods for applying phosphor and other optical materials to semiconductor devices, such as LEDs, face challenges including increased cost, complexity, non-uniformity, and difficulty in controlling the geometry and thickness of phosphor layers, leading to inconsistent emission characteristics and color temperature variations with viewing angle.
Innovation Solution
A substrate with a mounting surface and a relief surface around the perimeter, where the relief surface is lower than the mounting surface, allowing the encapsulant to form a meniscus without contacting the substrate, and a conformal layer with a higher coefficient of thermal expansion than the LED, providing thermal expansion relief and maintaining uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphor-containing encapsulant material is dispensed over the LED to cover the LED, then the LED emits both blue and yellow light combining to provide white light, but it is difficult to control the geometry and thickness of the phosphor layer resulting in non-uniform color temperature as a function of viewing angle
Solution Approach 1:
The patent introduces a vertical dimension by forming a raised mounting surface on the substrate. This elevation creates a controlled spatial relationship between the LED and substrate, allowing the encapsulant to form a consistent meniscus shape with uniform thickness around the LED perimeter, thereby achieving uniform color temperature across different viewing angles.
Solution Approach 2:
The patent modifies the physical parameters of the mounting surface by raising it to a specific height above the substrate plane. This parameter change (vertical positioning) enables precise control over encapsulant thickness and geometry, directly addressing the manufacturing precision issue while maintaining color temperature uniformity.
2Ease of manufacture
If conventional dispensing methods are used to apply phosphor encapsulant, then the LED can be covered with phosphor material, but the geometry and thickness of the phosphor layer cannot be consistently reproduced
Solution Approach 1:
The patent performs preliminary action by pre-forming the raised mounting surface on the substrate before dispensing the encapsulant. This preparatory step establishes a fixed geometric reference that guides the encapsulant formation, ensuring consistent meniscus shape and thickness without requiring complex control during the dispensing process itself.
Solution Approach 2:
The raised mounting surface structure enables the encapsulant to self-form into a consistent meniscus shape through capillary action and surface tension. The geometry is determined by the fixed mounting surface height and LED position rather than requiring precise control of dispensing parameters, achieving reliability through self-organizing physical processes.
3Device complexity
If the encapsulant contacts the substrate directly, then the structure is simpler, but the meniscus shape cannot be maintained and sagging occurs reducing uniformity
Solution Approach 1:
The patent segments the substrate surface into two distinct levels: a raised mounting surface for the LED and a lower surrounding substrate plane. This segmentation creates a physical barrier that prevents the encapsulant from contacting the main substrate, maintaining the meniscus shape and preventing sagging while adding minimal 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
This configuration ensures consistent emission performance by maintaining the meniscus shape of the encapsulant, reducing sagging, and preventing contact with the substrate, thereby enhancing the uniformity and reproducibility of light emission characteristics across different angles.
Implementation Method 1
The phosphor material absorbs and 'downconverts' some of the blue light generated by the LED. That is, the phosphor material generates light, such as yellow light, in response to absorbing the blue light.
Implementation Method 2
Some embodiments include a meniscus formed by an encapsulant around the LED and having a consistent geometry
Data Source
AI summary
Methods are disclosed including generating a substrate surface topography that includes a mounting portion that is higher than a relief portion that defines a perimeter of the mounting portion.