Asymmetric LED Package Reflector for Thin Backlighting
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Solution Overview
Problem
Conventional LED devices face challenges in achieving further downsizing while maintaining high output and preventing package discoloration due to light emission, which shortens their lifespan.
Innovation Solution
The LED device incorporates a reflector portion on one side wall with a greater inclined angle than the other, allowing efficient light reflection and emission, and features a thinner side wall without a reflector to reduce package thickness, along with a lead frame design that includes projecting portions for heat dissipation and improved resin sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflector portions are provided on both opposite side walls to prevent discoloration and improve light extraction, then reliability and output are improved, but device thickness increases
Solution Approach 1:
The invention extracts the reflector function from both side walls and concentrates it on only one side wall. The reflector portion is provided on one of the opposite side walls while the other side wall is made thinner without a reflector, thereby preventing package discoloration while reducing overall package thickness.
Solution Approach 2:
The invention applies different structural qualities to different parts of the package. One side wall has a reflector portion with specific inclined angles for light reflection, while the opposite side wall is made thinner without a reflector, creating asymmetric local qualities that optimize both protection and thickness reduction.
2Length of stationary object
If the package is made thinner to achieve downsizing, then device thickness is reduced, but light directly incidents on the package inner wall causing discoloration and shortened lifetime
Solution Approach 1:
The reflector portion acts as an intermediary element that intercepts light before it can directly incident on the package inner wall. By positioning the reflector on one side wall, it redirects light away from the package interior, preventing discoloration while allowing the package to be made thinner.
3Productivity
If reflector portions are provided on opposite side faces to maintain high output, then light extraction efficiency is improved, but device complexity and thickness increase
Solution Approach 1:
The invention extracts the reflector function from both side faces and retains it only on one side face. This simplifies the package structure by eliminating the need for symmetric reflectors on both sides, while the single reflector portion maintains high light extraction efficiency through optimized inclined angles.
4Length of stationary object
If the side wall without reflector is made thinner to reduce package thickness, then device thickness is reduced, but structural strength may be compromised
Solution Approach 1:
The invention employs asymmetric design where one side wall is made thinner without a reflector while the opposite side wall retains the reflector portion. The asymmetric distribution of structural and optical functions allows the thinner side wall to suffice for mechanical support without compromising overall package strength.
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 enables the LED device to achieve high output while being thinner, preventing resin discoloration and improving heat radiation, making it suitable for compact applications like thin backlights for liquid crystal displays.
Implementation Method 1
the light is reflected by the reflector portion and is emitted through an opening of the recess
Implementation Method 2
a lead frame design that includes projecting portions for heat dissipation
Data Source
Figure 1~2B
Figure 3~4
Figure 5A~5B
AI summary
The present invention provides a light emitting device (1), comprising: a package (10) which is formed of a resin and has a recess (9) which is provided with a bottom face (11) and two pairs of opposite inner walls surrounding the bottom face (11), the package having two pairs of opposite side walls made of the inner walls and corresponding outer walls; a lead frame (20) exposed at the bottom face; a light emitting element (30) which is provided on the lead frame (20); and a sealing resin (40) provided in the recess (9) for sealing the light emitting element (30), wherein the lead frame (20) has a bottom portion (21) and a reflector portion (22) exposed along one of the pair of opposite inner walls, and a first angle (¸ 1 ) between the reflector portion (22) and the bottom face (11) is greater than a second angle (¸ 2 ) between another one of the pair of opposite inner walls which is opposite to the reflector portion (22) and the bottom face (11).