LED Die Assembly Using Carrier Transfer and Selective Bonding
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Solution Overview
Problem
Conventional Pick Up Tool (PUT) techniques are inadequate for parallel transfer and selective bonding of multiple Light Emitting Diode (LED) dies due to difficulties in controlling forces at small scales, leading to non-uniformity and reduced yield in display manufacturing.
Innovation Solution
The method involves forming an epitaxial layer on a substrate with a quantum well layer, using carrier substrates with adhesive layers to transfer LED dies to a backplane, and employing laser lift-off and conductive bonding techniques to facilitate parallel and selective transfer of LED dies, allowing for simultaneous bonding and testing before transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Pick Up Tool (PUT) techniques are used to transfer LED dies, then individual die transfer is possible, but parallel transfer and selective bonding of multiple LED dies cannot be achieved due to difficulties in controlling forces at small scales
Solution Approach 1:
The patent segments the transfer process into two distinct phases: (1) parallel transfer of multiple LED dies from the substrate to the backplane using a PUT, and (2) selective bonding of non-defective dies. This segmentation allows the system to achieve high productivity through parallel transfer while maintaining precision through subsequent selective bonding based on die quality assessment.
Solution Approach 2:
The patent performs preliminary testing and identification of defective LED dies before the bonding step. By pre-characterizing the quality of each die and marking defective ones, the system can then selectively bond only non-defective dies to the backplane. This preliminary action resolves the contradiction by enabling parallel transfer of all dies while ensuring only quality dies are bonded.
2Productivity
If all LED dies are transferred to the backplane, then manufacturing speed is improved, but defective dies are also placed on the backplane reducing yield
Solution Approach 1:
The patent implements preliminary quality assessment and marking of LED dies before transfer to the backplane. Defective dies are identified and marked (e.g., with ink or physical markers) during the parallel transfer process, allowing subsequent selective bonding to exclude only the defective dies. This maintains high manufacturing speed while protecting yield by preventing defective dies from being bonded to the backplane.
Solution Approach 2:
The system enables self-sorting of LED dies based on their quality characteristics. By incorporating real-time or pre-transfer quality assessment, the system automatically identifies and segregates defective dies without requiring manual inspection, thereby maintaining high productivity while ensuring only good dies are bonded to the backplane.
3Manufacturing precision
If force control precision is maintained high for individual die manipulation, then positioning accuracy is improved, but manufacturing speed decreases due to sequential processing
Solution Approach 1:
The patent divides the transfer operation into a parallel phase where multiple dies are transferred simultaneously with relaxed force control, followed by a selective bonding phase where positioning precision is applied only to non-defective dies. This segmentation allows the system to achieve high throughput through parallel processing while maintaining positioning accuracy only where necessary for final bonding.
Solution Approach 2:
The patent applies partial precision control by transferring all LED dies with standard force control (sufficient for parallel transfer) and then applying enhanced precision control only during the selective bonding of non-defective dies. This partial application of precision control maintains manufacturing speed while ensuring accurate positioning only for the critical bonding operation.
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 enables efficient parallel transfer and selective bonding of LED dies, improving manufacturing speed and yield by relaxing force control precision and enabling the transfer of non-defective dies, while preventing defective ones from being placed on the backplane.
Implementation Method 1
forming an adhesive layer between the second surface of the epitaxial layer and a surface of the single carrier device to adhere the epitaxial layer to the single carrier device
Implementation Method 2
forming a bonding layer between a subset of the LED devices and a surface of a backplane to bond the subset of the LED devices with the backplane
Implementation Method 3
using a light directed through the carrier substrate to weaken the adhesive bond between the second surface of the epitaxial layer and the carrier substrate
Data Source
AI summary
A method for manufacturing LED devices is provided. The method comprises forming an epitaxial layer on a starter substrate, the epitaxial layer having a first surface that interfaces with the starter substrate and a second surface opposite to the first surface; establishing an adhesive bond between the second surface of the epitaxial layer and a carrier substrate having a pre-determined light transmittance; etching away the starter substrate; etching away part of the epitaxial layer to form a plurality of light emitting diode (LED) dies on a third surface of the epitaxial layer opposite to the second surface; establishing one or more conductive bonds between selected one or more LED dies, from the plurality of LED dies, and a backplane; weakening the adhesive bond between the second surface of the epitaxial layer and the carrier substrate; and moving the carrier substrate away from the backplane.