LED Substrate Protection Structure Against Solder Invasion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED packaging methods, particularly the eutectic joint process, face issues where solder can invade the interfaces between the compound reflection metal layers, reducing efficiency and the working life of LEDs.
Innovation Solution
A protection structure with trenches is formed on the substrate's surface opposite to the epitaxy structure to prevent solder from entering the interfaces between the compound metal reflection layers during the eutectic joint process, increasing the distance and resistance for solder penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the eutectic joint method is used to mount LED on package substrate, then the joint strength and heat dissipation are improved, but the solder invades the interfaces between compound metal reflection layers reducing LED efficiency and working life
Solution Approach 1:
The invention divides the reflection layer into multiple separate reflection units (first reflection layer, second reflection layer, third reflection layer) with isolation trenches between them. This segmentation prevents solder from continuously invading across the entire reflection layer interface, as the trenches act as barriers to stop solder penetration while maintaining the eutectic joint's strength and heat dissipation benefits.
Solution Approach 2:
The isolation trench acts as an intermediary barrier between the solder and the reflection layer interfaces. This trench structure mediates the interaction by providing a physical obstacle that prevents direct contact between solder and the metal layer interfaces, thereby protecting the LED's working life while allowing the eutectic joint to function properly.
2Illumination intensity
If the compound reflection metal layer is formed to enhance LED brightness, then the light reflection efficiency is improved, but the interfaces between layers become vulnerable to solder invasion
Solution Approach 1:
The compound reflection metal layer is segmented into multiple reflection layers (Al/Ti/Ag, Al/Ti/Ag, Al/Ti) separated by isolation trenches. This segmentation maintains the high reflection efficiency needed for brightness while creating protective barriers that prevent solder from reaching the metal layer interfaces during the eutectic joint process.
Solution Approach 2:
The isolation trenches, which initially appear to reduce the reflective area, actually convert the potential harm of solder invasion into a benefit by protecting the reflection layer interfaces. The trenches serve as sacrificial features that prevent solder from contaminating the critical metal layer interfaces, thereby preserving LED reliability while maintaining adequate brightness.
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 solution enhances the quality and yield rate of LEDs by preventing solder invasion, thus maintaining the efficiency and extending the working life of the LEDs.
Implementation Method 1
a compound reflection layer placed on the second surface of the substrate... the brightness of LEDs can be enhanced by from 30 to 50% with the addition of a compound reflection metal layer
Implementation Method 2
the metallic tin layer 26, of an LED can be adhered on the solder layer 30 of a package substrate to form a metal eutectic
Data Source
AI summary
A light emitting diode comprises a substrate having a first surface and a second surface, a light emitting epitaxy structure placed on the first surface of the substrate, and a compound reflection layer placed on the second surface of the substrate. The second surface of the substrate further has a protection structure.