LED Lighting Device with Metal Substrate Slit for Stress Relief
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Solution Overview
Problem
LEDs mounted on metal substrates face issues with heat expansion coefficients, leading to solder stress and potential cracking, which can result in a non-luminescent LED due to the difference in thermal expansion between the metal substrate and the LED components.
Innovation Solution
A lighting device using a metal substrate with a ceramic LED package, where the LED chip is mounted on a ceramic substrate with anode and cathode electrodes on the front surface and heat release electrodes on the back, and a resin insulation film is applied between the LED packages, with conductive patterns formed on the metal substrate for brazing connections, and a slit is formed between electrodes to reduce stress and enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal substrate is employed to improve heat dissipation and reduce LED surface temperature, then the amount of light increases due to lower temperature, but the difference in heat expansion coefficient between the metal substrate and LED components causes solder stress and potential cracking
Solution Approach 1:
The patent employs a composite substrate structure consisting of a metal substrate (aluminum or aluminum alloy) combined with a ceramic layer or coating. This composite structure leverages the high thermal conductivity of metal for heat dissipation while the ceramic component provides a lower thermal expansion coefficient that better matches LED components, thereby reducing solder stress and improving joint reliability.
Solution Approach 2:
The patent modifies the thermal expansion coefficient parameter of the substrate by selecting specific aluminum alloys with controlled composition or by applying ceramic coatings with tailored thermal properties. This parameter adjustment allows the substrate to maintain low thermal expansion near the LED mounting area while preserving high thermal conductivity for heat dissipation, thus resolving the contradiction between temperature control and reliability.
2Illumination intensity
If the driving current is increased to increase the amount of light, then the light output increases, but the surface temperature of LED rises which limits further current increase
Solution Approach 1:
The patent extracts the heat generation problem from the LED operation by implementing an enhanced heat dissipation system through the metal substrate with optimized thermal pathways. This allows the LED to operate at higher currents for increased light output while the extracted heat is efficiently removed through the substrate, preventing temperature rise that would otherwise limit current increase.
3Ease of manufacture
If a printed substrate is employed to mount LED, then the manufacturing cost is reduced, but the surface temperature rises significantly due to low thermal conductivity
Solution Approach 1:
The patent applies local quality by using a metal substrate with high thermal conductivity specifically in the LED mounting area where heat dissipation is critical, while other areas of the substrate can maintain cost-effective designs. This localized approach to thermal management provides superior heat dissipation where needed without requiring the entire substrate to be expensive metal construction.
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 effectively reduces the surface temperature of the LED, allowing for increased driving current and light output while minimizing solder stress and the risk of cracking, thereby enhancing the reliability and performance of the LED module.
Implementation Method 1
a coefficient of thermal conductivity of metal substrate is large. This means that a metal substrate effectively works as a heat sink and radiator plate, and the surface temperature of LED is decreased
Implementation Method 2
a brazing material is disposed between the conductive patterns and the electrodes, and the conductive patterns and the electrodes are bonded by brazing
Data Source
AI summary
A lighting device including a metal substrate to prevent temperature rise of LED chip is offered. The lighting device includes the metal substrate, an anode or cathode electrode of the LED chip disposed on the metal substrate, brazing materials connecting the LED chip and the metal substrate, and a groove formed in the anode or cathode electrode. Forming the groove can prevent an occurrence of a crack in the brazing materials.Also, a lighting device includes the metal substrate, an anode and cathode electrode of the LED chip disposed on the metal substrate and brazing materials connecting the LED chip and the metal substrate. Further, a slit is formed in the metal substrate between the anode and cathode electrode. Forming the slit in the metal substrate can prevent an occurrence of a crack in the brazing materials.