LED Assembly Using Pick-Up Tool Placement Cycles
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Solution Overview
Problem
Current methods for assembling Inorganic Light Emitting Diode (ILED) displays face challenges in scaling down standard LEDs for smaller displays due to inefficiencies in light direction control and high wafer yields, requiring new assembly processes that can handle millions of pixels with high throughput and accuracy, especially for portable devices where battery power is a concern.
Innovation Solution
A method involving a pick-up tool (PUT) for placing untested and tested LED dies on a display substrate, with optional deformable materials for adhesion, allowing for selective replacement of non-functional dies and enabling massive parallel pick and transfer of LED dies <10 μm in size with ±3 μm accuracy, combined with calibration cycles to ensure high display yield and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard LED assembly methods are used, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to inability to achieve ±3 μm accuracy for sub-10 μm dies
Solution Approach 1:
The patent applies preliminary action by pre-configuring the PUT with adhesion promoters and preparing the display substrate with alignment features before the actual placement process. This ensures that when placement occurs, the sub-10 μm LED dies can be accurately positioned at ±3 μm precision without requiring complex real-time adjustment mechanisms during the assembly process itself.
Solution Approach 2:
The patent introduces an intermediary PICK-UP-TRANSFER (PUT) tool that acts as a mediator between the LED die source and the display substrate. The PUT incorporates adhesion promoters and alignment features that enable precise handling and placement of sub-10 μm dies, resolving the contradiction by providing a specialized intermediate device that bridges the gap between standard manufacturing and high-precision requirements.
2Reliability
If wafer level testing is performed to identify KGD, then reliability improves, but productivity deteriorates due to complicated testing processes
Solution Approach 1:
The patent applies partial action by performing wafer level testing on a subset of LED dies rather than all dies, or by using rapid screening methods that test only critical parameters. This allows sufficient reliability to be achieved for the needed number of KGD while maintaining assembly throughput, avoiding the complete testing bottleneck that would otherwise reduce productivity.
Solution Approach 2:
The patent performs wafer level testing as a preliminary action before the main assembly process, identifying and segregating KGD in advance. This allows the subsequent assembly process to proceed at high speed using pre-validated dies, separating the testing function from the assembly function to maintain overall productivity while ensuring reliability.
3Reliability
If multiple placement cycles are used to replace defective dies, then reliability improves, but loss of time increases
Solution Approach 1:
The patent performs preliminary identification and preparation of replacement KGD before the placement cycles begin. By having replacement dies pre-configured and ready on the PUT with adhesion promoters pre-applied, the system can quickly swap defective dies during placement cycles without requiring time-consuming preparation steps during the actual replacement process, thus maintaining reliability while minimizing time loss.
Solution Approach 2:
The patent maintains continuity of useful action by designing the placement process so that while some dies are being tested and evaluated for defects, other placement operations continue uninterrupted with known good dies. The system continuously progresses through placement cycles without idle waiting time, ensuring that reliability improvements from multiple cycles do not come at the cost of excessive delays.
Data Source
AI summary
A method for manufacturing a display element comprising a plurality of pixels, each comprising a plurality of sub-pixels. The method comprises undertaking, using a pick up tool, a first placement cycle (1908) comprising picking up a plurality of first, untested LED dies and placing them on a display substrate at locations corresponding to the plurality of pixels, testing (1912) the first LED emitters on the display substrate to determine one or more locations of non-functional first LED emitters, selecting one or more second tested LED dies based on a result of the test, configuring the selected one or more second LED dies to enable their pick up and placement on the display substrate and undertaking, using the PUT, a second placement cycle (2008) comprising picking up the selected one or more second LED dies and placing them on the display substrate at the determined locations of the non-functional first LED emitters.