Stacked LED Display Assembly for Faster Sub-Pixel Mounting
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Solution Overview
Problem
Conventional LED displays face challenges in efficiently transferring and mounting individual LED chips onto display panels due to time-consuming rearrangement processes and the need to reduce sub-pixel size, which can compromise luminous area.
Innovation Solution
A method of transferring LED devices in groups by dividing wafers into light emitting devices using laser scribing, attaching them to a transfer tape, and bonding to a circuit board with controlled adhesive forces, allowing for efficient mounting and increased sub-pixel area utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LED chips are arranged individually on a transfer tape after wafer breaking, then the LED chips can be positioned at correct intervals, but the rearrangement process consumes significant time
Solution Approach 1:
The patent applies preliminary action by pre-forming the wafer with LED chips arranged at the correct intervals during the wafer fabrication process. The scribing lines are pre-defined on the wafer to enable direct transfer of multiple LED chips in their correct positions without requiring subsequent rearrangement steps. This preliminary arrangement eliminates the time-consuming individual chip rearrangement process while maintaining precise interval positioning.
Solution Approach 2:
The patent merges multiple LED chips into a single wafer structure that is transferred together as one unit. Instead of handling individual chips separately, the invention transfers a group of LED chips simultaneously from the wafer to the substrate, maintaining their relative positions and intervals. This merging approach reduces the number of separate transfer operations and significantly decreases total mounting time.
2Productivity
If the area of each sub-pixel is reduced to fit more pixels in a restricted area, then more pixels can be arranged, but the luminous area of each LED chip is reduced
Solution Approach 1:
The patent transitions from a two-dimensional arrangement where reducing sub-pixel area increases pixel density to a three-dimensional stacked structure. By stacking multiple LED chips vertically at each pixel location, the invention maintains larger individual chip areas for sufficient luminous output while achieving high pixel density through the additional vertical dimension. This dimensional change allows both goals to be achieved simultaneously.
Solution Approach 2:
The patent implements nesting by stacking multiple LED chips vertically within each pixel location, similar to nested dolls. Multiple light-emitting layers are positioned one above another at the same horizontal footprint, allowing each chip to maintain its full luminous area while the stacked configuration increases the effective pixel density. The chips are nested in the vertical dimension rather than competing for horizontal space.
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 significantly reduces mounting time and ensures each sub-pixel has a larger area without compromising luminous intensity, enhancing the efficiency of LED display apparatuses.
Implementation Method 1
dividing the wafer into a plurality of light emitting devices while the light emitting devices are in close contact with each other
Implementation Method 2
bonding the at least one light emitting device to the pads by applying heat to the bump pads and the pads
Data Source
AI summary
A light emitting display including a circuit board, a plurality of light emitting devices arranged on the circuit board each including a first, LED stack, a second LED stack, and a third LED stack, a bump pad disposed between the circuit board and the light emitting device, the bump pad comprising Au material, and an encapsulating layer comprising an optical interference preventing material and covering the light emitting devices, in which the circuit board includes an interconnection line and a plurality of pads disposed on an upper surface thereof to provide electrical connection, the first, second, and third LED stacks are stacked in a vertical direction, one of the LED stacks configured to emit light having the longest wavelength among the first, second, and third LED stacks is in ohmic contact with the Au material, and the bump pad has an irregular upper surface.