Light-Emitting Device Metal Layer Thermal Stress Distribution
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Solution Overview
Problem
Light-emitting devices bonded to wiring boards with solder are prone to damage due to thermal expansion coefficient differences, leading to potential damage from thermal shock or temperature cycles.
Innovation Solution
A light-emitting device structure featuring a layered structure with semiconductor layers, a light-transmissive member, and metal layers, where the metal layers cover the lateral surfaces and electrodes, providing a larger bonding area and stress distribution to reduce damage and enhance bonding strength and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light-emitting device is bonded to a wiring board with solder, then electrical connection and mounting are achieved, but the device is prone to damage from thermal shock or temperature cycles due to different thermal expansion coefficients
Solution Approach 1:
The patent introduces an intermediate layer structure between the light-emitting device and the wiring board. This intermediate layer acts as a buffer zone that segments the direct bonding interface, allowing differential thermal expansion without transmitting full stress to the light-emitting device. The intermediate layer includes a first metal layer connected to the light-emitting device and a second metal layer connected to the wiring board, creating a staged bonding structure that reduces thermal stress concentration.
Solution Approach 2:
The patent uses an intermediate layer as a mediator between the light-emitting device and the wiring board. This intermediate layer has thermal expansion properties that are intermediate between the two components, acting as a buffer that absorbs thermal expansion differences. The intermediate layer includes adhesive layers and metal layers that provide both mechanical bonding and thermal stress management, protecting the light-emitting device from direct thermal shock.
2Area of stationary object
If a conventional bonding structure is used, then the device can be mounted, but the bonding area is limited and stress concentration occurs
Solution Approach 1:
The patent extends the bonding interface from a simple point or small area contact to a multi-layered planar structure. The intermediate layer includes first and second metal layers that spread the bonding area across multiple dimensions, transforming the stress distribution from concentrated to distributed. This dimensional expansion of the bonding interface reduces stress concentration while maintaining secure mounting.
Solution Approach 2:
The bonding structure is segmented into multiple discrete layers including adhesive layers and metal layers, each performing specific functions. The first metal layer bonds to the light-emitting device while the second metal layer bonds to the wiring board, with intermediate adhesive layers providing transition. This segmentation allows each layer to be optimized for its specific function and distributes stress across multiple interfaces rather than concentrating it at a single bonding point.
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 structure effectively reduces damage from thermal stress and improves bonding strength and heat dissipation by distributing stress across a larger area and facilitating precise mounting and alignment.
Implementation Method 1
Because the thermal expansion coefficients of the wiring board and the light-emitting device bonded to each other with solder are different, the light-emitting device may be damaged by thermal shock or temperature cycles
Implementation Method 2
a pair of first metal layers on the first main surface of the light-emitting element, the pair of first metal layers covering a surface of the covering member and being respectively connected with the pair of electrodes; and at least one second metal layer separated from the first metal layers
Data Source
AI summary
A light-emitting device includes a light-emitting element that includes a layered structure including a semiconductor layer and a pair of electrodes on a first main surface of the layered structure, a light-transmissive member on a second main surface of the layered structure, the second main surface being opposite to the first main surface, a covering member covering lateral surfaces of the light-emitting element and the first main surface of the layered structure except for at least part of the pair of electrodes, a pair of first metal layers on the first main surface of the light-emitting element, the pair of first metal layers covering a surface of the covering member and being respectively connected with the pair of electrodes, and at least one second metal layer separated from the first metal layers.