LED Testing Circuit Layout for Small-Pitch Defect Screening
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Solution Overview
Problem
Conventional LED testing methods are inefficient for small-sized LEDs due to the small size of electrodes and the space between them, making it difficult to perform effective testing.
Innovation Solution
A manufacturing method that involves forming a testing circuit on a substrate with multiple zones, electrically connecting LEDs in each zone to form parallel or series-parallel circuits, and using this circuit to test and identify defective LEDs, allowing for their removal or repair, and transferring the remaining LEDs to a target carrier or module carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional probes are used to test small-sized LEDs, then the testing method is simple and easy to operate, but the testing effectiveness is poor due to the small size of electrodes and space between them
Solution Approach 1:
The substrate is divided into multiple zones, with each zone containing a group of LEDs and an integrated testing circuit. This segmentation allows testing to be performed at the zone level rather than requiring individual probe contact with each tiny LED electrode, thereby improving testing effectiveness while maintaining operational simplicity.
Solution Approach 2:
Multiple LEDs within each zone are electrically connected to form parallel or series-parallel circuits, and the testing circuit is integrated directly on the substrate. This merging approach enables collective testing of multiple LEDs simultaneously, overcoming the limitation of small electrode sizes and making the testing process more effective and efficient.
2Productivity
If individual LED testing is performed using conventional methods, then each LED can be tested independently, but the testing efficiency is low and time-consuming
Solution Approach 1:
Multiple LEDs in each zone are electrically connected to form circuits that can be tested collectively. The testing circuit applies current to and measures the light output of multiple LEDs simultaneously through shared current input and light detection paths, significantly improving testing efficiency and reducing the time required compared to individual testing.
Solution Approach 2:
The testing circuit is designed with universal functionality to handle multiple LEDs within each zone using the same current input path and light detection mechanism. This multi-functional design allows the same testing infrastructure to efficiently test numerous LEDs without requiring separate testing setups for each LED, thereby increasing productivity.
3Reliability
If testing circuits are added to test small-sized LEDs, then testing capability is improved, but the substrate space is reduced
Solution Approach 1:
The substrate is divided into multiple zones, each containing a group of LEDs and a shared testing circuit. This segmentation allows the testing circuit area to be distributed across multiple zones rather than requiring a large centralized testing area, thereby improving testing capability while minimizing the impact on overall substrate space availability.
Solution Approach 2:
The testing circuit is integrated directly on the substrate and shares common current input paths and light detection mechanisms across multiple LEDs within each zone. This merging approach consolidates the testing infrastructure, reducing the total area required for testing components while maintaining full testing capability for all LEDs in the zone.
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
Enables efficient testing and identification of defective LEDs, improving the yield and quality of small-sized LEDs by allowing for selective testing and repair, and optimizing the use of substrate space for testing circuits.
Implementation Method 1
a light-emitting diode (LED) includes: a semiconductor stack including a first semiconductor layer, an active region and a second semiconductor layer which are sequentially formed on a substrate
Implementation Method 2
In a conventional LED testing method such as electroluminescence (EL) testing, probes are applied to the electrodes of the LED to input a testing current to obtain the photoelectric characteristics of the LED
Data Source
AI summary
A manufacturing method for an LED includes: providing a substrate having an upper surface divided into a plurality of zones; a LED group formed on each of the zones and wherein: a plurality of the LED groups includes a first LED group; and the LEDs of the first LED group include a defective LED; forming a testing circuit on the substrate to electrically connect the LEDs; testing the first LED group by the testing circuit; recording a position of the defective LED; providing a carrier; and performing one of the following steps by the position of the defective LED: removing the defective LED from the substrate and then transferring the other LEDs in the first LED group to the carrier; transferring the other LEDs other than the defective LED in the first LED group to the carrier; or transferring the LEDs to the carrier and repairing it on the carrier.