Substrate With Variable-Volume Conductive Bumps For Micro LED Alignment
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Solution Overview
Problem
The challenge in manufacturing micro LED displays arises from thermal stress causing substrate warpage, which displaces micro LEDs and complicates alignment during mass transfer, leading to reduced transfer yield due to uneven bonding strength and conductivity issues.
Innovation Solution
A substrate design featuring conductive bumps of varying volumes and thicknesses at different positions to accommodate warped carrier boards, ensuring consistent bonding strength and alignment of micro elements across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform conductive bumps are used on the substrate, then the manufacturing process is simple, but the alignment precision deteriorates due to substrate warpage caused by thermal stress
Solution Approach 1:
The patent applies local quality by making conductive bumps have different volumes at different positions on the substrate. Specifically, conductive bumps in the peripheral region have larger volumes than those in the central region, which compensates for the substrate warpage and maintains consistent bonding strength across the entire substrate surface.
Solution Approach 2:
The patent changes the volume parameter of conductive bumps based on their position on the substrate. By adjusting the volume of conductive bumps according to the substrate warpage profile, the invention achieves consistent bonding performance across warped surfaces while maintaining a relatively simple overall substrate structure.
2Productivity
If the substrate is heated and cooled during manufacturing, then the micro LEDs can be formed and transferred, but the substrate deforms due to thermal expansion coefficient differences
Solution Approach 1:
The patent applies preliminary anti-action by pre-designing conductive bumps with different volumes to counteract the expected substrate warpage. The larger peripheral bumps are positioned to compensate for the outward bulging that occurs during thermal processing, thereby maintaining alignment precision throughout the heating and cooling cycles.
3Manufacturing precision
If conductive bumps with different volumes are used, then the alignment precision improves on warped substrates, but the manufacturing complexity increases
Solution Approach 1:
The patent implements local quality by varying only the volume parameter of conductive bumps at different positions, while keeping other substrate characteristics uniform. This localized modification achieves improved alignment precision without requiring complex overall substrate design.
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 enhances the transfer yield by evenly distributing stress and maintaining consistent conductivity across micro elements, improving the alignment and bonding process even on warped substrates.
Implementation Method 1
since the thermal expansion coefficients of the various materials may be different, the substrate carrying micro LEDs may be deformed (such as bowing or warpage) while being heated and cooled due to thermal stress
Data Source
AI summary
The present invention discloses a substrate configured to receive a plurality of micro elements on a carrier board. The substrate comprises a body, a first conductive bump, and a second conductive bump. The body has a first surface, a transfer area is defined within the first surface, and a central portion and a peripheral portion is defined within the transfer area. The first conductive bump, disposed on the central portion, has a first volume. The second conductive bump, disposed on the peripheral portion, has a second volume. Wherein the first volume is different from the second volume.