Laminate Sub-Mount for LED Thermal Management
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Solution Overview
Problem
High output LEDs generate significant heat, which can be destructive and reduce their lifespan, and existing thermal management solutions, such as heat sinks on printed circuit boards, are insufficient for effectively dissipating this heat as electrical currents increase.
Innovation Solution
A thin laminate sub-mount with a metal layer, dielectric layers, and a thermally conductive core is used, featuring a coefficient of thermal expansion matching the PCB, allowing for efficient heat dissipation and mounting via conventional reflow processes or mechanical attachment, with a reflective coating to enhance illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat sinks on the printed circuit board are used to dissipate heat from the LED, then thermal management is improved, but the heat dissipation effectiveness is insufficient for high output LEDs with increased electrical currents
Solution Approach 1:
The patent transitions from two-dimensional heat dissipation on the PCB surface to three-dimensional heat management by introducing a vertical heat conduction path through the sub-mount structure. The sub-mount creates a thermal pathway that extends perpendicular to the PCB plane, allowing heat to be conducted away from the LED in the vertical dimension rather than relying solely on lateral heat spreading on the PCB surface.
Solution Approach 2:
The sub-mount is constructed as a composite structure with a metal core providing high thermal conductivity for heat conduction, dielectric layers for electrical insulation and mechanical support, and a ceramic-filled polymer for enhanced thermal management properties. This composite material approach enables simultaneous optimization of thermal conduction, electrical isolation, and mechanical stability.
2Stability of the object's composition
If the sub-mount uses a metal layer with thickness between 17 microns and 70 microns, then thermal expansion matching with PCB is achieved, but mounting complexity increases compared to conventional methods
Solution Approach 1:
The patent specifies precise thickness parameters for the metal layer (17-70 microns) and top metal layer (17 microns to 1 mm) to achieve optimal thermal expansion matching with the PCB. By controlling these dimensional parameters, the sub-mount's coefficient of thermal expansion is tuned to match the PCB, ensuring stable thermal and mechanical performance during operation and temperature cycling.
Solution Approach 2:
The sub-mount structure serves multiple functions simultaneously: it provides electrical isolation between LED electrodes and the PCB, conducts heat away from the LED, offers mechanical support for the LED package, and enables thermal expansion matching with the PCB. This multi-functionality reduces the need for separate components and simplifies the overall assembly.
3Ease of manufacture
If conventional reflow processes are used for mounting, then manufacturing simplicity is maintained, but thermal management effectiveness may be compromised
Solution Approach 1:
The sub-mount is segmented into distinct functional layers: a bottom metal layer for PCB attachment and thermal conduction, dielectric layers for electrical isolation, and a top metal layer with conductive pads for LED mounting. This segmentation allows each layer to be optimized for its specific function while maintaining compatibility with conventional manufacturing processes.
Solution Approach 2:
The sub-mount acts as an intermediary component between the LED and the PCB, providing a transition structure that enables both mechanical attachment and thermal management. The metal core and bottom metal layer serve as thermal intermediaries conducting heat from the LED to the PCB, while the dielectric layers provide electrical isolation, allowing conventional reflow processes to be used without compromising thermal management.
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 manages heat dissipation, improving LED reliability and efficiency by matching thermal expansion coefficients and providing a robust thermal management system that complements conventional mounting methods, while enhancing light emission through reflective coatings.
Implementation Method 1
a metal core on which the LED is mounted. Vias are formed in the dielectric layer to electrically interconnect the conductive pads with electrically isolated portions of the bottom metal layer... The metal core may further comprise a multi-layer metal composite and may include an insulating layer sandwiched between the top portion and bottom portion of the sub-mount to further manage the heat dissipation
Implementation Method 2
A reflective coating may be deposited on the top layer to enhance the illumination of the LED
Implementation Method 3
The bottom metal layer is treated so that it solders to a PCB or MCPCB using conventional reflow processes... effectively manages heat dissipation, improving LED reliability and efficiency
Data Source
AI summary
An LED package is described that acts as a sub-mount between a printed circuit board and a diode. The sub-mount includes a laminate to thermally isolate the diode, for example an LED, from the PCB while providing a thermal heat dissipative sink for the diode.