Flip-Chip LED Electrode Self-Alignment via Segmented Pads
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Solution Overview
Problem
Conventional flip-chip semiconductor light-emitting devices face misalignment issues during mounting due to differences in electrode area, leading to poor soldering film finish and potential bonding failures, especially with the negative electrode being smaller and harder to bond accurately.
Innovation Solution
The design involves forming electrode pads of equal size and shape for both positive and negative electrodes, with a short-circuit preventing insulator film and soldering particles in the pads, and using flux paste on the printed circuit board to improve soldering film finish and ensure accurate self-alignment during the re-flow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode area is made larger than the negative electrode area to improve light extraction and electrical conductivity, then the light-emitting efficiency and current flow are improved, but misalignment occurs during mounting and the soldering film finish deteriorates
Solution Approach 1:
The invention divides the electrode structure into two functional parts: the light-emitting electrode (positive or negative) maintains its optimized area for light extraction and current flow, while a separate mounting electrode of equal area is provided for both positive and negative sides. This segmentation allows the light-emitting function and mounting function to be independently optimized, resolving the contradiction between light-emitting efficiency and mounting alignment precision.
2Area of moving object
If the negative electrode area is reduced to minimize the device footprint, then the device size is reduced, but the bonding accuracy and soldering film quality during mounting deteriorate
Solution Approach 1:
The invention separates the light-emitting function from the mounting function by providing distinct electrodes for each purpose. The negative electrode maintains its small area for compact device footprint, while an equal-area mounting electrode is provided specifically for mounting operations. This allows the device to remain compact while achieving accurate bonding and good soldering film quality during mounting.
3Reliability
If different shaped electrodes are used for positive and negative electrodes to optimize their respective functions, then the electrical and optical performance is improved, but the mounting process becomes more complex and misalignment increases
Solution Approach 1:
The invention segments the electrode system into light-emitting electrodes (which can have different optimized shapes for electrical and optical performance) and mounting electrodes (which are equal in area and shape for both polarities). This segmentation simplifies the mounting process by providing symmetric mounting interfaces while preserving the asymmetric electrode designs needed for optimal electrical and optical performance.
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 approach prevents misalignment, ensures accurate bonding of the light-emitting device on the printed circuit board, and improves the finish of the soldering film, reducing production costs and increasing the accuracy of the mounting process.
Implementation Method 1
the soldering film is then melted and solidified by re-flow, thereby bonding the positive electrode pad and the negative electrode pad respectively with the electrode patterns
Implementation Method 2
using flux paste on the printed circuit board to improve soldering film finish and ensure accurate self-alignment during the re-flow process
Data Source
AI summary
A flip-chip type semiconductor light-emitting device having a positive electrode and a negative electrode similar in electrode area and capable of preventing the misalignment of the light-emitting device by utilizing the self alignment effect in manufacturing a light-emitting diode lamp and a printed circuit board for the flip-chip type semiconductor light-emitting device are provided. Furthermore, adopted are a flip-chip type semiconductor light-emitting device 1 which is provided with a negative electrode pad and a positive electrode pad formed on the side opposite the transparent substrate side of the semiconductor layer, wherein each of the electrode pads is formed in the same shape as each other and a printed circuit board for the light-emitting device has a pair of the electrode patterns which are formed in the same shape as each other. Still furthermore, a soldering film is included in each of the electrode pads.