Micro-LED Element Pin Asymmetry for Alignment Tolerance
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Solution Overview
Problem
The high alignment precision requirements for micro-LED elements and bonding pads in display devices lead to low yield due to the small size of micro-LED elements and the resulting stringent assembly challenges.
Innovation Solution
The design of micro-LED elements with strip-like element pins and bonding pads with strip-like bonding pins, where the length of the element pin is greater than the width of the bonding pin and a non-zero included angle between their extending directions, allowing for increased alignment tolerance and reducing the risk of misalignment defects during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the micro-LED element size is reduced to achieve high-resolution display, then the display resolution is improved, but the alignment precision requirement increases and yield decreases
Solution Approach 1:
The bonding pin is designed with asymmetric dimensions where the length in the first direction (alignment direction) is greater than the width in the second direction. This asymmetric geometry creates a larger tolerance window for alignment in the critical first direction, allowing the micro-LED element to be accurately aligned despite size reduction, thereby maintaining high display resolution while improving assembly yield
Solution Approach 2:
The bonding pin structure utilizes dimensional differentiation by making the length in the first direction significantly larger than the width in the second direction. This dimensional change allows the alignment process to be more tolerant in the first direction (length direction) while maintaining precision requirements in the second direction, effectively decoupling the alignment sensitivity from the micro-LED element size reduction
2Reliability
If the alignment precision requirement is increased to maintain welding quality, then the welding quality is improved, but the assembly complexity and difficulty increase
Solution Approach 1:
The bonding pin employs asymmetric dimensions with length greater than width, creating a geometric feature that guides alignment in the critical first direction. This asymmetric design inherently provides alignment tolerance that maintains welding quality without requiring complex assembly processes or high-precision positioning equipment
Solution Approach 2:
The asymmetric bonding pin structure performs the alignment function preliminarily through its geometric design before the actual welding process. The larger length in the first direction pre-establishes an alignment tolerance window, allowing the micro-LED element to be positioned accurately without requiring complex real-time adjustment mechanisms during assembly
Data Source
AI summary
The present disclosure provides a light-emitting unit and a display device. The light-emitting includes a micro-LED element and a bonding pad. The micro-LED element includes an element pin, the bonding pad includes a bonding pin, in each welding pair of the element pin and the bonding pin, a length of the element pin is greater than a width of the bonding pin, and a non-zero angle is formed between the extending direction of the element pin and the extending direction of the bonding pin. When the element pin is deviated from the bonding pin in a certain range, the element pin can still be aligned accurately with the bonding pin. Thus, a requirement on the alignment precision between the micro-LED element and the bonding pad is lowered in a certain extent, thereby improving the yield.