Multilayer Chip Varistor Heat Diffusion for LED Thermal Management
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Solution Overview
Problem
Semiconductor light emitting elements generate heat during operation, which is difficult to efficiently dissipate, especially when sealed in optically transparent resin, leading to potential thermal management issues.
Innovation Solution
A light emitting device comprising a semiconductor light emitting element connected in parallel to a multilayer chip varistor with a varistor layer comprising ZnO, which facilitates heat diffusion through expanded heat radiation paths and improved bonding strength between the varistor and external electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the semiconductor light emitting element is sealed in an optically transparent resin, then the light emission is protected and maintained, but the heat diffusion becomes more difficult
Solution Approach 1:
The heat diffusion path is segmented into multiple routes: heat from the semiconductor light emitting element is transferred to the multilayer chip varistor, which then conducts heat through its internal electrodes and varistor layers to external electrodes and the substrate. This segmentation allows heat to bypass the optically transparent resin and diffuse through dedicated thermal pathways.
Solution Approach 2:
The multilayer chip varistor acts as an intermediary component between the semiconductor light emitting element and the substrate. It provides a dedicated heat conduction path with high thermal conductivity materials (ZnO varistor layer, metal internal electrodes, solder balls) that mediates heat transfer without compromising the optical properties of the sealing resin.
2Reliability
If a varistor is connected in parallel to protect from ESD surge, then the reliability is improved, but the heat diffusion capability is reduced
Solution Approach 1:
The varistor material parameters are specifically selected to achieve dual functionality: ZnO is used as the principal component because it provides both excellent nonlinear voltage-current characteristics for ESD protection and high thermal conductivity for heat diffusion. The internal electrodes are made of high-conductivity metals to enhance thermal conduction while maintaining electrical function.
Solution Approach 2:
The multilayer chip varistor employs a composite structure combining different materials with complementary properties: ZnO varistor layers for electrical protection, metal internal electrodes for thermal and electrical conduction, and solder balls for heat sinking. This composite construction enables simultaneous achievement of ESD protection and heat diffusion.
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 diffuses heat generated by the semiconductor light emitting element, preventing thermal inhibition and ensuring efficient heat management while protecting against ESD surges.
Implementation Method 1
the varistor layer comprising ZnO as a principal component... ZnO has a thermal conductivity approximately equal to that of alumina or the like normally used as a heat radiation substrate, and thus has the thermal conductivity relatively good
Implementation Method 2
the heat generated in the semiconductor light emitting element to be transferred mainly to the external electrodes and the internal electrodes and then to radiate
Data Source
AI summary
A light emitting device has a semiconductor light emitting element and a multilayer chip varistor. The multilayer chip varistor has a multilayer body with a varistor portion therein, and a plurality of external electrodes disposed on an outer surface of the multilayer body. The varistor portion has a varistor layer containing ZnO as a principal component and exhibiting nonlinear voltage-current characteristics, and a plurality of internal electrodes arranged to interpose the varistor layer between them. Each of the external electrodes is connected to a corresponding internal electrode out of the plurality of internal electrodes. The semiconductor light emitting element is disposed on the multilayer chip varistor. The semiconductor light emitting element is connected to corresponding external electrodes out of the plurality of external electrodes so as to be connected in parallel to the varistor portion.