Twisted Diode Pair for Orientation-Independent Micro-LED Assembly
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Solution Overview
Problem
The challenges in fabricating micro-LED and nano-LED displays include low throughput and high costs due to difficulties in handling small die sizes, controlling LED orientation, and achieving precise pick and place assembly tolerances, which increase post-placing process time and expense.
Innovation Solution
A twisted diode pair is formed by coupling a monolithic N-type semiconductor layer with a monolithic P-type semiconductor layer, allowing one diode to be forward biased and the other reverse biased, enabling diode pairs to be placed without prior orientation, ensuring proper biasing regardless of placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional pick and place assembly is used for micro-LED and nano-LED displays, then individual LED placement is achieved, but throughput is low and costs are high due to difficulties in handling small die sizes and controlling LED orientation
Solution Approach 1:
The patent merges two oppositely oriented LED dies onto a single substrate, creating a combined structure where one LED is oriented in the forward direction and the other in the reverse direction. This merging eliminates the need for individual orientation control during assembly, as the combined structure ensures proper orientation regardless of how it is placed on the display substrate.
Solution Approach 2:
The patent segments the LED assembly into paired units with opposite orientations rather than placing individual LEDs. Each paired structure contains two LED dies mounted in opposite directions, allowing the assembly process to treat them as a single unit. This segmentation approach simplifies the pick and place process while ensuring that at least one LED in each pair will be properly oriented.
2Reliability
If individual LED orientation control is implemented during pick and place, then proper forward biasing is achieved, but assembly tolerances must be precise and post-placing process time increases
Solution Approach 1:
The patent introduces asymmetry by mounting two LED dies in opposite orientations on the same substrate. This asymmetric configuration ensures that regardless of the orientation in which the paired structure is placed, one of the LEDs will be in the correct forward-biased orientation. This eliminates the need for precise orientation control during assembly while maintaining reliable forward biasing.
3Manufacturing precision
If precise pick and place assembly is performed for small LED die sizes, then correct LED placement is achieved, but process time and expense increase
Solution Approach 1:
The patent combines two LED dies into a single paired structure that is placed as one unit rather than placing individual LEDs separately. This merging approach reduces the number of placement operations required and eliminates the need for post-placement orientation adjustments, thereby reducing both process time and expense while maintaining placement precision.
Data Source
AI summary
A device includes a P-N junction comprising a monolithic N-type semiconductor layer coupled to a monolithic P-type semiconductor layer. The monolithic N-type semiconductor layer includes a first portion and a second portion. The first portion has a first surface and the second portion has a second surface facing away from the first surface. The monolithic P-type semiconductor layer includes a third portion and a fourth portion. The third portion has a third surface and the fourth portion has a fourth surface facing away from the third surface.