Selective Elastomer Deposition for Operational LED Sorting
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Solution Overview
Problem
Current LED manufacturing techniques do not guarantee perfect yields, resulting in non-operational LEDs being transferred to display substrates during assembly, which can lead to defective displays.
Innovation Solution
A process involving a unidirectional conductive film and elastomer material deposition to differentiate operational from non-operational LEDs by applying a voltage difference and measuring electrical parameters, allowing only operational LEDs to be picked up and placed on the display substrate using a pick-up tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current LED manufacturing techniques are used, then production speed and cost are maintained, but non-operational LEDs are transferred to display substrate causing defects
Solution Approach 1:
The patent applies preliminary action by performing LED operational testing and elastomer deposition on the source substrate before the pick-and-place transfer process. This ensures that only operational LEDs have elastomer material applied, allowing the PUT to selectively pick up only functional LEDs. The testing and material application occur in advance, preventing defective LEDs from being transferred to the display substrate.
Solution Approach 2:
The patent introduces elastomer material as an intermediary substance that mediates between the LED operational status and the PUT pickup process. The elastomer material acts as a selective adhesive layer that enables the PUT to grip only operational LEDs, while non-operational LEDs without elastomer remain untouched. This intermediary material provides a physical mechanism for yield-based selective transfer.
2Manufacturing precision
If all LEDs are transferred without selection, then transfer speed is maintained, but display substrate quality deteriorates due to non-operational LEDs
Solution Approach 1:
The patent replaces the traditional mechanical blind transfer method with a selective pickup mechanism based on material adhesion properties. Instead of mechanically forcing all LEDs to be transferred, the system uses the presence or absence of elastomer material to enable or disable pickup at each location. This substitution of mechanical transfer with adhesion-based selection achieves both high precision and maintained productivity.
Solution Approach 2:
The patent applies local quality by varying the surface properties of individual LEDs based on their operational status. Operational LEDs receive elastomer material deposition creating a sticky surface, while non-operational LEDs retain their original non-sticky surface. This localized differentiation in surface quality enables the PUT to selectively pick up only functional LEDs at specific locations on the source substrate.
3Measurement precision
If LED testing is performed before transfer, then yield accuracy is improved, but process time and complexity increase
Solution Approach 1:
The patent merges the LED testing process with the material deposition process into a single integrated operation. The testing apparatus identifies operational LEDs, and immediately subsequent to testing, elastomer material is deposited on those same LEDs. This merging of detection and action eliminates separate handling steps and reduces the time loss associated with sequential testing and transfer operations.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the transition from testing to material deposition occurs without interruption or idle time. The system continuously processes LEDs through testing and immediately applies elastomer material to operational units, keeping the production flow continuous rather than introducing batch processing or waiting periods that would increase cycle time.
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
Ensures 100% yield by selectively picking and placing only operational LEDs, preventing non-operational ones from being transferred, thus ensuring a fully functional display substrate.
Implementation Method 1
The conductive surface or film may comprise a unidirectional conductive film, such that a voltage difference can be applied to the electrodes of each LED through the film
Implementation Method 2
An elastomer material deposition apparatus may selectively deposit elastomer material onto a surface of each of the plurality of LEDs determined to be operational
Data Source
AI summary
LEDs are manufactured on a substrate layer and picked and placed using a pick-up tool (PUT) onto a target substrate. The PUT typically attaches to an LED via an elastomer layer deposited on a surface of the LED. A given batch of manufactured LEDs may contain operational LEDs as well as non-operational LEDs. In order to separate the operational and non-operational LEDs, the LEDs are placed on a unidirectional conductive film. A voltage difference applied across the electrodes of each LED via the unidirectional conductive film powers the LEDs and causes the operational LEDs to emit light. An electrical parameter of each LED is measured and used to determine whether each LED is operational or non-operational. An elastomer deposition apparatus selectively deposits elastomer material on the operational LEDs, allowing for the operational LEDs to be picked up using the PUT, while not depositing elastomer material on the non-operational LEDs.