LED Package Cap Phosphor Layer for Hot Spot Suppression
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Solution Overview
Problem
Light-emitting diode (LED) packages face challenges in suppressing the hot spot phenomenon and achieving a wider beam angle due to poor adhesive force between the phosphor film and the LED element, leading to color deviation and limited luminance.
Innovation Solution
A phosphor layer formed in the shape of a cap with uniform thickness is arranged to surround the LED element, gold wires, and bonding pads, with a filler filling the space between the phosphor layer and the LED element, enhancing the beam angle and suppressing hot spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphor film is attached to the LED element using electrostatic force or adhesive force, then the phosphor film can be applied on the surface, but the adhesive force is poor and the phosphor film cannot be effectively attached at the desired position, leading to color deviation and reliability issues
Solution Approach 1:
A resin layer is introduced as an intermediary between the LED element and the phosphor film. The resin layer is applied in advance on the LED element surface, providing a bonding interface that improves adhesive force and enables precise positioning of the phosphor film without relying solely on electrostatic or adhesive forces between the phosphor material and resin material.
Solution Approach 2:
The resin layer is applied in advance (pre-coating) on the LED element surface before attaching the phosphor film. This preliminary action ensures that the bonding surface is properly prepared, improving both adhesive strength and positioning accuracy when the phosphor film is subsequently attached.
2Device complexity
If a lead frame is used in the LED element, then the structure is simple, but the light-emitting region is limited due to reflection at side walls, intensifying the hot spot phenomenon and reducing beam angle
Solution Approach 1:
The phosphor layer is formed with non-uniform thickness, being thicker at the center and thinner at the edges, to locally adjust the light conversion characteristics. This local quality variation helps distribute the luminance more evenly and suppress hot spots while maintaining the lead frame structure.
Solution Approach 2:
The phosphor layer is extended to surround not only the top surface but also the side surfaces of the LED element, adding a vertical dimension to the phosphor distribution. This three-dimensional arrangement increases the effective light-emitting region and beam angle by utilizing side wall emission that would otherwise be lost to reflection.
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 the beam angle and reduces the hot spot phenomenon, improving the reliability and luminance distribution of the LED package while maintaining efficient manufacturing throughput.
Implementation Method 1
a phosphor layer formed in a shape of a cap having side and top portions of a uniform thickness and being configured to surround side surfaces and a top surface of the LED element
Data Source
AI summary
The present invention provides a light-emitting diode (LED) package including: a substrate on which a set of bonding pads are formed; an LED element configured to provide light of a predetermined wavelength region, having a set of chip pads formed on a top surface thereof and being attached on a top surface of the substrate; a set of gold wires connecting the bonding pads of the substrate with the chip pads of the LED element; a phosphor layer formed in a cap shape having side and top portions of a uniform thickness and being configured to surround sides and a top surface of the LED element while being spaced apart therefrom; and a filler disposed to fill a space formed between the phosphor layer and the LED element, wherein the LED element, the gold wires, and the bonding pads of the substrate are under the phosphor layer cap.