Micro LED Electrode Groove Structure for Reliable Eutectic Bonding
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Solution Overview
Problem
The challenge lies in efficiently mounting extremely small light emitting diodes (LEDs) on circuit boards using conventional surface mounting technology, as the small size of micro LEDs results in close spacing of bump pads, making conventional bonding techniques unreliable and time-consuming.
Innovation Solution
The solution involves a light emitting device structure with multiple stacked LEDs and connection electrodes, where bonding metal layers with grooves on the electrodes facilitate eutectic bonding to circuit board pads, allowing for stable and efficient mounting of micro LEDs, reducing the mounting process time and enabling electrical measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface mounting technology is used to mount micro LEDs, then the mounting process can be performed with existing equipment, but the mounting becomes unreliable and time-consuming due to extremely small LED size and close spacing of bump pads
Solution Approach 1:
The invention divides the mounting structure into distinct functional segments: the micro LED chip with its active area, the connection electrodes extending from the chip, and the bonding metal layers at the electrode ends. This segmentation allows each component to be optimized independently - the connection electrodes provide extended bonding surfaces while the bonding metal layers provide reliable bonding interfaces, solving the reliability issue without requiring time-consuming adjustments to the mounting process
Solution Approach 2:
The bonding metal layers act as intermediary elements between the connection electrodes and the circuit board pads. These metal layers (such as Au, Ag, or Cu) provide a compatible bonding interface that facilitates reliable eutectic bonding with the circuit board, thereby improving mounting reliability while maintaining process efficiency
2Productivity
If the size of light emitting devices is reduced to create micro LEDs, then more devices can be arranged on a display, but the interval between bump pads becomes extremely small making conventional mounting infeasible
Solution Approach 1:
The invention transitions from a two-dimensional mounting approach (direct bonding of small LED chips to closely spaced pads) to a three-dimensional structure by extending connection electrodes outward from the LED chip. This dimensional extension creates additional bonding space, allowing the bonding metal layers to be positioned away from the chip body, thereby making mounting feasible despite the extremely small LED size and close pad spacing
Solution Approach 2:
The connection electrodes and bonding metal layers are pre-formed as integral parts of the LED structure before mounting. This preliminary preparation of extended bonding surfaces and compatible metal layers eliminates the need for time-consuming adjustments during the mounting process, maintaining ease of manufacture while enabling micro LED deployment
3Reliability
If bonding metal layers are added to connection electrodes, then eutectic bonding reliability is improved, but the device structure becomes more complex
Solution Approach 1:
The bonding metal layers are merged with the connection electrodes to form an integrated structure. The bonding metal layers are deposited directly onto the connection electrodes, creating a unified component that combines the electrical connection function of the electrodes with the bonding function of the metal layers. This merging improves bonding reliability while minimizing the increase in structural complexity
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 enables faster and more reliable mounting of micro LEDs on circuit boards, improving the efficiency of the manufacturing process and allowing for precise electrical measurement, overcoming the limitations of conventional bonding techniques for small LEDs.
Implementation Method 1
bonding metal layers with grooves on the electrodes facilitate eutectic bonding to circuit board pads
Data Source
AI summary
A light emitting device including a first light emitting stack, a second light emitting stack disposed under the first light emitting stack, a third light emitting stack disposed under the second light emitting stack, first, second, third, and fourth connection electrodes disposed over the first light emitting stack, and electrically connected to the first, second, and third light emitting stacks, and bonding metal layers disposed on upper surfaces of the first, second, third, and fourth connection electrodes, in which each of the first, second, third, and fourth connection electrodes includes a groove on an upper surface thereof, and the bonding metal layers cover the grooves of the first, second, third, and fourth connection electrodes, respectively.