Laser Phosphor Tile Assembly With Liquid Metal Thermal Interface
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Solution Overview
Problem
Existing laser light sources with phosphor conversion face challenges in heat management, particularly due to thermal delamination or destruction caused by mismatched thermal expansion coefficients between the ceramic phosphor tile and the heat sink.
Innovation Solution
A laser lighting device is designed with a ceramic phosphor tile and a heat sink, where a metal layer with a melting point below 120°C is used between the heat sink and the reflective coating on the phosphor tile, ensuring good thermal contact and preventing force exertion on the phosphor tile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic phosphor tile is soldered onto a heat sink using traditional soldering methods, then good thermal contact is achieved, but thermal delamination or destruction occurs due to mismatched thermal expansion coefficients during temperature cycling
Solution Approach 1:
The patent changes the physical state parameter of the bonding material from solid to liquid by using a low melting point metal (melting point below 120°C). This allows the bonding material to remain liquid during operation, accommodating thermal expansion differences between the ceramic phosphor tile and heat sink, thereby preventing delamination while maintaining thermal contact.
Solution Approach 2:
The patent utilizes phase transition of the bonding metal from solid at room temperature to liquid at operating temperature. The metal layer melts during operation to provide compliant thermal bonding that absorbs thermal stress, and can resolidify when cooled, creating a self-adjusting bonding mechanism that prevents delamination during temperature cycling.
2Stability of the object's composition
If a rigid soldered connection is used between the heat sink and reflective coating, then structural stability is achieved, but stress builds up on the phosphor tile during temperature cycling causing delamination
Solution Approach 1:
The patent changes the mechanical property parameter of the bonding layer from rigid to compliant by using a low melting point metal that remains liquid during operation. This compliant liquid metal layer absorbs thermal stress through its fluidity, preventing stress buildup on the phosphor tile while maintaining structural integrity of the overall assembly.
Solution Approach 2:
The patent introduces a low melting point metal layer as an intermediary between the heat sink and the reflective coating on the phosphor tile. This intermediary layer acts as a stress buffer that decouples the rigid connection, allowing differential thermal expansion without transmitting damaging stresses to the phosphor tile, while still providing thermal conduction path.
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 use of a low-melting-point metal layer maintains efficient thermal contact and reduces stress on the ceramic phosphor tile, preventing delamination and extending the device's lifetime by ensuring reliable operation across a wider temperature range.
Implementation Method 1
The interconnector and the substrate together may still provide high reflectivity
Implementation Method 2
a ceramic phosphor tile configured to receive laser light emitted by the laser light source, wherein the ceramic phosphor tile is configured for at least partly converting the laser light into the phosphor-converted light
Implementation Method 3
The thermal expansion coefficient of YAG is 8 × 10 -6
Data Source
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Figure 5~6
AI summary
A laser light source comprises a laser source and a ceramic phosphor tile having a light entry face for receiving laser light from the laser source for laser pumping by the laser light. A reflective coating is formed over a face opposite the light entry face. A metal layer is provided between a heat sink and the ceramic phosphor tile, wherein the metal layer has a melting point below 120oC. The metal layer thus becomes a liquid during operating temperatures, and this reduced strain on the phosphor layer while maintaining thermal contact.