To make a good Micro LED display, you still need to cross the hurdle of detection and repair.

LED testing includes photoluminescence (PL) and electroluminescence (EL) testing. The former method can test the LED chip without contact and damage, but compared with EL testing, it may not detect all defects. In contrast, EL testing is able to identify more defects, but it tests the LED chip by setting a current, which requires contact with the LED chip and can cause damage to the chip.

For Micro LED testing, applying EL testing is very difficult and inefficient because the chip size is too small for traditional testing equipment. However, using PL testing may miss some defects, resulting in poor results.

As a result, technology developers and equipment manufacturers are working on large-scale testing technology to improve detection efficiency without damaging the chip. A joint research team from Xiamen University and Taiwan's National Chiao Tung University has developed a camera-based microscopic imaging system for Micro LED testing. The system integrates a computer, current source, digital camera, current supply probe, microscope and supporting software to capture and analyze micrographs to measure the brightness of Micro LED chips.

Konica Minolta Group, which specializes in equipment manufacturing, has also begun to cooperate with its subsidiaries Instrument Systems (Germany) and Radiant Vision Systems (USA) to develop Micro LED and Mini LED inspection systems, covering a wide range of inspection applications, including gamma tuning, uniformity and LED chip inspection.

Since Micro LED chips are so small, how to effectively repair and replace them after identifying them is also a challenging task. Currently, Micro LED repair solutions include ultraviolet radiation repair technology, laser welding repair technology, selective repair technology, selective laser repair technology and redundant circuit design solutions.

American startup Tesoro has proposed a method that combines non-contact EL testing and BAR (Beam-Address Release) transfer, which can transfer only LED chips without problems to the target substrate at high speed.

Japanese equipment supplier Toray launches its Micro LED inspection and repair solution. Its automated optical inspection tools enable non-contact inspection, and then its laser trimming tools can troubleshoot faulty Micro LED chips based on the inspection results.