LED Package Radiator Thermal Expansion Mismatch
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Solution Overview
Problem
Conventional light emitting diode (LED) packages face reliability issues due to thermal expansion differences between materials, leading to planarity deterioration of the radiator and subsequent tilting of the light emitting device, affecting heat dissipation and light emission angle.
Innovation Solution
The LED package design incorporates a radiator with a Cu layer as the lower layer and a Cu alloy layer, such as Cu-W or Cu-Mo, stacked over the Cu layer, to match the thermal expansion coefficient of the light emitting device, preventing damage from thermal stress and maintaining a stable light emission angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a radiator made of high thermal-conductivity material (e.g., Cu-W) is used, then heat dissipation performance is improved, but planarity deterioration occurs due to thermal expansion differences
Solution Approach 1:
The patent changes the material parameters of the radiator by using a Cu alloy with specifically controlled composition (Cu-5wt%W or Cu-5wt%Mo) to match the thermal expansion coefficient with the light emitting device. This parameter adjustment resolves the contradiction by maintaining both heat dissipation performance and planarity stability under thermal stress.
Solution Approach 2:
The patent employs a composite radiator structure made of Cu-W or Cu-Mo alloy, combining copper's excellent thermal conductivity with tungsten or molybdenum's low thermal expansion characteristics. This composite material approach simultaneously achieves high heat dissipation performance and dimensional stability, preventing planarity deterioration.
2Stress or pressure
If the radiator surface becomes roughened due to volumetric expansion, then thermal stress is reduced, but light emission angle tilts and mounting alignment deteriorates
Solution Approach 1:
The patent changes the thermal expansion parameter by selecting Cu alloy materials with thermal expansion coefficients matched to the light emitting device. This prevents differential expansion that would cause surface roughening, thereby maintaining both thermal stress management and manufacturing precision for light emission angle and mounting alignment.
3Ease of manufacture
If a single-layer Cu radiator is used, then manufacturing simplicity is maintained, but thermal expansion mismatch causes reliability issues
Solution Approach 1:
The patent uses Cu-W or Cu-Mo composite alloy materials that inherently combine the benefits of copper (thermal conductivity) and tungsten/molybdenum (thermal expansion matching). This single-phase composite material approach maintains manufacturing simplicity while significantly improving reliability under thermal stress compared to pure copper.
Solution Approach 2:
The patent modifies the material composition parameter of the radiator from pure copper to Cu alloy with controlled W or Mo content (5wt%). This parameter change achieves thermal expansion matching with the light emitting device, preventing reliability issues while maintaining ease of manufacture through standard alloy fabrication processes.
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 enhances the reliability of the LED package by stabilizing the light emitting device's position, improving heat transfer, and maintaining a consistent light emission angle, while preventing damage from thermal expansion.
Implementation Method 1
the radiator 180 may undergo deterioration of planarity due to a difference in coefficients of thermal expansion between different constituent materials of the package body 110 and the radiator 180
Implementation Method 2
the radiator 180 and the light emitting device 130 may be fixed to each other via a conductive adhesive layer 120
Data Source
Figure 1
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AI summary
Disclosed is a light emitting diode package. The light emitting device includes a package body (210) having a cavity defined by a sidewall and a bottom surface, a light emitting diode (230) disposed in the cavity, a radiator (220) inserted into the package body and disposed below the light emitting diode, and a second electrode pattern disposed around the radiator and electrically connected to the light emitting diode via wire bonding. The second electrode pattern includes a first region to which a wire is bonded, and a second region connected to the first region, and a width of the first region differs from a width of the second region.