Electronic Substrate Layout for Thermal Stress Relief in LED Bonding
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Solution Overview
Problem
The coefficient of thermal expansion mismatch between LEDs and bases, such as glass, leads to cracks in the base or peeling of the LED during thermal shock tests, resulting in dark spots.
Innovation Solution
The electronic substrate design includes a protruding portion and a bonding pad where the bonding pad is not overlapped with the boundary of the protruding portion, creating a gap to reduce stress and improve solder joint flatness, thereby reducing the likelihood of base cracking and LED peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the bonding pad is positioned close to or overlapped with the protruding portion boundary to maximize space utilization, then the area utilization is improved, but the stress concentration increases leading to base cracking and LED peeling
Solution Approach 1:
The patent introduces an intermediary protective layer between the bonding pad and the protruding portion boundary. This protective layer acts as a stress buffer that absorbs thermal expansion forces, preventing direct stress transmission to the bonding pad and base interface, thereby eliminating cracks and peeling while maintaining close positioning for space efficiency
2Area of stationary object
If the bonding pad is positioned close to or overlapped with the protruding portion boundary to maximize space utilization, then the area utilization is improved, but the stress concentration increases leading to base cracking
Solution Approach 1:
The protective layer serves as a mediator that distributes and absorbs thermal stress before it reaches the base structure. This prevents stress concentration at the bonding pad edges and protruding portion boundary, maintaining base structural integrity while allowing compact layout
3Area of stationary object
If the bonding pad is positioned close to or overlapped with the protruding portion boundary to maximize space utilization, then the area utilization is improved, but the solder joint flatness deteriorates
Solution Approach 1:
The protective layer provides a flat, stable surface for the bonding pad while maintaining close proximity to the protruding portion. This intermediary structure ensures uniform solder joint formation by preventing edge effects and stress-induced deformation, achieving both compact layout and high manufacturing precision
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 design reduces the base cracking rate from 11.5% to 2% and maximum stress from 2905 MPa to 752 MPa, enhancing the reliability of the electronic device.
Implementation Method 1
coefficient of thermal expansion (CTE) mismatch readily occurs between the LED and the base (such as glass), thus leading to cracks in the base or peeling of the LED
Data Source
AI summary
An electronic substrate and an electronic device are provided. The electronic substrate includes a base, a conductive electrode, and a first layer. The conductive electrode and the first layer are disposed on the base, the first layer surrounds the conductive electrode and overlaps an edge portion of the conductive electrode. In a cross-sectional view, the first layer is divided into a first part and a second part, the conductive electrode is located between the first part and the second part, and a width of the first part is different from a width of the second part.