Micro-LED Quality Validation

Micro-LED wafer testing device and method that allows non-destructive testing of micro-LEDs without damaging the fragile electrodes. The testing device has periodic through holes with testing elements inside. Each element has a metal post and dielectric portion. The dielectric contacts the micro-LED electrodes. The top metal post and wafer metal are powered to test the micro-LEDs without contact probes that could damage the small micro-LED electrodes.

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A micro LED detection device using AI to improve efficiency and accuracy in inspecting micro LED wafers. The device uses air bearings to move multiple detection modules over the wafers. A host with AI judgment units analyzes images from the modules for brightness, defects, and etching depth. The air-float platform setup allows synchronized motion of the modules to accurately align and compare views. The AI improves detection efficiency and precision by enabling consistent analysis across different detection methods.

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Abstract In this study, the thickness-dependent impact of atomic layer deposition (ALD) passivation on green micro-scaled-light-emitting diodes (micro-scaled-LEDs) varying sizes (40 70 m and 100 200 m) was systematically explored to mitigate sidewall defect-induced efficiency degradation. AlO layers (0-60 nm) were integrated into devices, followed by electrical, optical, aging analyses. Thinner (30 reduced reverse leakage 23% improved external quantum (EQE) 10.65% in smaller while thicker compromised light extraction due absorption. Larger devices exhibited limited EQE gains (6.54%) negligible thickness sensitivity. ABC + f(n) modeling confirmed suppressed Shockley-Read-Hall recombination enhanced radiative efficiency, offset partially Auger effects at higher carrier densities. Post-aging, passivated small retained 98.31% optical stability. The results emphasize a critical trade-off between defect losses scaled proposing dimension-specific ALD strategies for high-efficiency micro-LEDs.

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A method for inspecting micro LEDs on a growth substrate before transferring them to a display panel. The method involves forming electrodes and contacts on the micro LEDs and applying test power to them. This allows inspecting the LEDs' illumination before transferring. The contacts are made on the growth substrate and the test power is applied using probes. An image sensor captures the LED light and a control compares it to a reference to determine defects. This avoids disassembling the display after manufacturing to inspect the LEDs.

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Abstract Micro lightemitting diodes (MicroLEDs) are regarded as the core of nextgeneration display technology due to their high brightness and energy efficiency. However, reduction in size MicroLEDs has led increased manufacturing challenges exacerbated issues such sidewall emission, which hinder development highpixeldensity displays. This paper proposes a vertically stacked MicroLED design based on an Lshaped metal wall structure, aiming suppress emission enhance top light extraction efficiency (LEE). Through parameter scanning, dimensions thickness epitaxial layer optimized. Combined with inclined sidewalls reflective structure wall, optical characteristics red, green, blue analyzed using raytracing simulations. The is significantly reduced (with maximum 68.04% compared without walls), enhanced (the LEE within 90 direction for blue, red by 196.18%, 51.69%, 3.45%, respectively, walls). simulation results demonstrate potential fullcolor displays, providing new approach suppressing crosstalk improving performance.

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Full-color monolithic InGaN micro-LEDs can achieve the transfer of full-color subpixels through a single flip-chip bonding process, offering advantages such as simplified fabrication processes and reduced production costs for micro-LED display. In this paper, we demonstrate structure that utilizes pseudo-quantum well to long-wavelength red emission, which is applied micro-LEDs. Subsequently, present micro-LEDs, stack (R), green (G), blue (B) epitaxial layers tunnel junctions. The entire grown epitaxially by metal organic chemical vapor deposition. Micro-LEDs with mesa size 2020 m 2 RGB are fabricated. exhibits emission peak wavelength 650 nm at an injection current density 1 A/cm , dominant approximately 620 nm, achieving true emission. Even under 100 it still maintain over 600 nm. broad color gamut coverage their significant potential applications in

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The top-down submicron fabrication of blue-emitting light-emitting diodes on Qromis Substrate Technology substrates is reported. Light-emitting with mesa sizes as small 250 nm2 show ideal forward voltage and low leakage current density. It observed that sidewall treatment passivation methods used in micro-light-emitting (220 m) do not lead to the same level recombination suppression for ones (<1 m), evidenced by a 70% decrease peak external quantum efficiencies when are scaled from 2 m down nm. This attributed lateral carrier diffusion being comparable size, regardless recovery. results call rethinking impact sidewalls emerging fabricated (sub)micrometer-light-emitting diodes.

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Using atomic force microscopy (AFM) and scanning near-field optical (SNOM)-photoluminescence (PL) spectroscopy (SNOM-PL), we study the nanoscopic structural emission properties of a red InGaN hybrid single quantum well (SQW), consisting blue SQW. AFM images reveal presence threading-dislocation (TD)-related V-pits shallow trench defects. The defects are classified into three categories on basis their height relative to flat QW: lowered-, level-, raised-center SNOM-PL demonstrate that TDs all types exhibit low intensity, indicating they act as non-radiative recombination centers. Unlike previous studies low-In content samples, intensity in our high-In sample because In segregation. Given correlation dark positions between emissions, lower screw-type TD density at surface than n-GaN layer, should be one triggers formation Therefore, enhance external efficiency LEDs, it is crucial suppress segregation within decrease density.

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Adapter device and testing method for improving efficiency and accuracy of chip packaging testing, particularly for micro LED displays. The adapter has a connection plate with multiple testing units, each containing a slot for a micro LED, signal transmission sheet, and connector. The LEDs are bonded to the plate. An adapter plate connects to the testing plate. This allows testing multiple LEDs simultaneously. An ID code on the plate helps locate faulty LEDs. The adapter facilitates integrated testing by combining multiple steps, improves efficiency by finding defects faster, and provides convenience for handling and testing the LEDs.

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Detection panel and device to reduce defects and improve efficiency in testing microLEDs. The panel has multiple detection units with closely spaced electrodes. When an LED is illuminated, the panel detects electrical properties to check for defects. The spaced electrodes prevent contact damage to the LED electrodes. The panel is used with an optical emitter to shine light on the LED being tested. By detecting the electrical changes induced by illumination, the panel can determine if the LED has defects. This avoids the need for direct electrode contact and sequential testing.

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This study presents an optimized design of green-emitting Micro-LED structures, using numerical simulations to elucidate the pivotal role Micro-LEDs with pre-well and pre-layer configuration in alleviating polarization-related electric fields promoting energy band flattening. The simulation quantitatively demonstrates structure's effectiveness enhancing wave function overlap radiative recombination efficiency. These insights provide a robust theoretical foundation for experimentally observed enhancements external quantum efficiency, wavelength stability, high-speed modulation performance devices.

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Enabling testing, repair, and replacement of micro devices integrated into a system substrate like an emissive display. It provides methods and structures for identifying, fixing, and replacing defective micro devices in integrated systems like displays. The methods involve using temporary electrodes to bias and test floating contacts, optical sensors to measure light output, and fuses to disconnect defective devices. The structures include spare circuits, repair pads, and defect mapping blocks for populating and connecting replacements.

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Repairing techniques for micro LED displays to increase yield and reduce cost when defective micro LEDs are found after transfer to the system substrate. The techniques include replacing defective micro LEDs with spare ones, converting color of spares to match defects, mapping spare locations, and spatial coordinate variation to mitigate visual artifacts. It also involves calibration to correct for spatial non-uniformity induced by repair techniques.

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Transferring microdevices like LEDs from a donor substrate to a receiver substrate in a way that avoids defects and performance issues. The technique involves arranging the microdevices in cartridges, aligning the cartridges with a template, bonding them, then transferring the devices from the template to the receiver substrate. This allows selective transfer of defect-free devices from cartridges rather than transferring entire blocks from the donor substrate. The cartridges can also have anchors to hold the devices during transfer and vias for temperature and mechanical property adjustment. By testing the cartridges and adjusting transfers based on defect data, it reduces defects in the final receiver substrate.

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Micro-LEDs are suitable as special light sources that serve small sensors and for optical communication. The most important technology these applications is Micro-LED high-precision transfer (0.5 m positional accuracy). existing has the problem of low position accuracy. This study proposes a high-position-precision method based on vibrations. A single system microgripper was designed to achieve positioning. Compared with other methods, this can be used in conjunction microscope camera Micro-LED. To test performance our proposed method, Micro-LED, length approximately 40, width 20, thickness 4 m, transferred. tested. Subsequently, 5 6 array results show 2 out 30 have deviation exceeding 3 so failure. success rate >90%. root-mean-square error 0.8 m. experimental exhibits good transfers.

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Abstract MicroLED is considered as the new generation of display with longlifetime, high contrast and brightness, splicing capability, so forth. Mass transfer bottleneck that limits manufacturing at large volume, due to factors such laserlift off, pickup, metal bonding. Metal bonding between chip substrate one most important lightup yield. To solve key thermal mismatch issue backplane donor during heating, laserassisted process could be a viable solution. We present study in metallic element Au/Sn productivity, capability low cost, well good electrical conductivity, excellent strength, sensitivity surface roughness. The result presented 62 78 pixels fullcolor display, reliable connection microscale LED devices can achieved under 250C without any damage backplane. In conclusion, micromorphology formation mechanism different alloy phase compositions welded elements have been thoroughly studied, feasible technological methodology has developed for upcoming mass production modules.

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MicroLED display technology with improved yield and production efficiency by selectively removing defective microLEDs before transfer to the final substrate. The method involves testing the microLEDs on a temporary substrate, removing any failures, and then transferring the remaining good microLEDs to the permanent display substrate. This prevents filling gaps with extra microLEDs, which can have lower yield. The key is controlling the transfer and removal rates so more defective microLEDs are removed than replaced.

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Micro light-emitting diode (Micro-LED) is widely regarded as a highly promising technology in the current display field due to its excellent performance, but core issue hindering further development of Micro-LED how achieve high-precision and high-yield transfer. In this study, laser-induced forward transfer (LIFT) adopted main technique, novel blister-type dynamic release layer (DRL) material selected, characterized by gentle process minimal residue on chip after Chip-on-wafer (COW) structure that fabricates large number Micro-LEDs (15 30 m2) sapphire substrate. The COW-on-head (COH) bonding method can control uniformity overall height before within 3.5%, which favorable for subsequent stable Based analysis close relationship between gap laser energy density, study successfully achieved red/green/blue (R/G/B) chips (6400, respectively) onto corresponding chip-on-carrier 2 (COC-2), all them have one-step yield over 99.3% an average offset m or less. It worth mentioning mentioned paper different from testing repairing chips. fully reflect quality. order verify validity 1 in., f... Read More

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Abstract Microlight emitting diode (LED) based LED on silicon (LEDoS) is a promising candidate for nextgeneration AR and VR displays due to superior pixel performance potential high resolution. Traditional RGB pixels are placed single plane, which limits the To overcome this, vertically stacked using heterogeneous monolithic 3D integration (M3D) have been explored. However, previously reported vertical LED not considered heat dissipation capability of pixels, indeed important in future micro displays, utilized materials incompatible with standard CMOS processes, further limiting their practicality LEDoS. The critical regions constraint, bonding medium, typically organic polymer materials. Therefore, handle issue, fullcolor LEDs demonstrated oxide (SiO 2 ) yttrium (Y O 3 ), as mediums. These CMOScompatible offer thermal conductivity at least 10 times higher than conventional polymers. InGaN/GaN blue bonded oxides show improved management, leading external quantum efficiency (EQE) better color characteristics, including narrower full width half maximum (FWHM) purity. ... Read More

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Testing large arrays of devices like microLED displays using parallel excitation with repeated contact and interaction without damaging the probes or devices. The test tool has multiple probes that can simultaneously contact multiple device contacts. Liquid metal is applied to the probe tips before contact to act as a flexible interface. When the probes touch the device contacts, oxide pinholes form in the contact layer allowing electrical connection through the liquid metal bridge. This allows repeated contact without damaging the probes or devices. The liquid metal seals when the probes lift, preventing flow onto the contacts. This enables parallel device excitation with optical monitoring without active feedback loops to maintain probe-contact alignment.

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A test system for efficiently and accurately measuring the performance of small form factor LEDs like micro-LEDs and nano-LEDs. The system uses a probe head with obliquely angled probes that can contact the tiny LEDs without blocking emitted light. It also has a movable cover over the probe slot to protect the probes when not in use. The probes measure voltage and current through the LEDs while a separate light detector captures emitted light. This allows calculating the quantum efficiency based on all three parameters.

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Determining quality of inspection data using a machine learning model that can distinguish between defective and non-defective products without requiring labeled training data for defective products. The method involves generating training data from non-defective products, learning the ML model on that, preparing a feature spectrum from a specific layer output for non-defective training data, and using that learned model and feature spectrum to determine quality of unseen inspection data. Similarity between the inspection data feature spectrum and the known feature spectrum is calculated and a threshold is used to determine if it's non-defective or defective.

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Contactless probe for measuring cycles of microdevices like LEDs without needing post-processing steps. The probe has an electrode covering a dielectric to stimulate the microdevice capacitively. A switch keeps the device on after an active portion of the stimulus signal. This allows measuring cycles without contact, resets, or parasitic effects. The stimulus amplitude can also be increased after each cycle.

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Detecting defects in display panels using deep learning to accurately locate and identify the type of defect in a stacked structure of a display panel. The method involves collecting images of defects and layers from a database, learning the defect and layer information using a deep learning model, and then using that model to extract the location of the defect in the stacked structure. The deep learning allows detecting detailed defect locations and layer associations compared to just checking for defects in a single image.

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Display device with improved reliability by adding inspection lines that overlap the cathode-power electrode connection regions to check for defects. The inspection lines are disposed on the encapsulation layer covering the display pixels. They overlap the cathode-power connections and allow capacitance measurements to determine if the connections are stable. If the measured capacitance is within a range, it indicates good connection. If outside the range, it indicates defective connection. This provides a reliability check for the cathode-power connections to prevent issues like noise leakage through poorly connected cathodes.

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Pixel circuit for display devices that allows simultaneous driving and sensing of electrical characteristics of multiple driving transistors for a pixel to improve reliability, efficiency, and HDR contrast. The circuit has two driving transistors connected to the pixel's light-emitting element and a sensing part to simultaneously drive one transistor while sensing the electrical characteristics of the other transistor. This allows real-time monitoring of transistor performance while simultaneously emitting light. It enables selection of the best performing transistor for driving the light-emitting element and detects deterioration early. The simultaneous emission of light from both transistors increases luminance with less current and improves display performance.

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Self-monitoring method for displays to detect abnormalities without manual intervention. The method involves inputting a test image, extracting display parameters for each frame of the displayed test image, comparing the parameters between frames to find variations, and determining if display abnormalities are present based on the parameter comparisons. By feeding back test images with known variations, the display can learn normal parameter ranges and detect aberrations.

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Detecting defective pixels in an image array using statistical analysis on sets of surrounding pixels. For each pixel, a cell with neighboring pixels is analyzed statistically. If the statistical distance of the pixel from the cell exceeds a threshold, it indicates a defective pixel. This provides a way to detect defective pixels without relying on calibration or edge detection, as the statistical outlier can be identified on-the-fly during image processing.

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Predicting defects in assembly units using machine learning techniques to enable real-time yield protection in optical inspection systems. The method involves extracting features from inspection images, generating vectors, labeling clusters based on inspection outcomes, and propagating defect labels upstream to detect anomalous regions in new assembly units. It uses machine learning to identify common features associated with proper function versus defects, and can assist in confirming defects by comparing against these feature sets.

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Display apparatus with improved diagnostics for microLED displays. It allows detecting panel issues during vertical blank periods when the display is off. The display has multiple microLED drivers with timings controlled by separate clock signals. During blanking, all clock signals go low to disable emitting in all pixels. This lets detecting abnormalities like stuck pixels.

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A method for non-destructively detecting LEDs bonded to a display substrate using a light source and a sensor. The method involves irradiating the LEDs with light from the source and measuring the emitted light with the sensor. By analyzing the spectral characteristics of the emitted light, the quality and performance of the LEDs can be assessed without physically contacting or damaging them. The method enables high-precision LED detection without requiring expensive equipment like lasers or probes.

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Display manufacturing apparatus that removes foreign substances from micro LEDs before assembly to prevent defects in the finished display. The apparatus has two modules for filtering out non-magnetic and magnetic foreign substances from the micro LEDs. The first module removes non-magnetic contaminants using filtration. The second module removes magnetic foreign substances using a magnetic field. This ensures the micro LEDs are clean before assembly on the display substrate to prevent issues like misalignment, electrical shorts, and lighting defects.

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Contactless micro LED inspection system that uses pulsed lasers to detect defective micro LEDs without direct electrical testing. The system emits pulsed lasers at the LEDs to generate photovoltaic radio frequency signals when radiated. An antenna receives these signals, which are amplified and analyzed by a processor to determine if the LED is functioning or defective. This allows high-efficiency, contactless testing of micro LED arrays without needing to electrically test each individual tiny LED.

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Contactless and high efficiency method for inspecting micro LEDs using radio frequency (RF) induction and imaging. The method involves applying an RF signal to a glass panel with a conductive layer on top of the micro LEDs. The RF illuminates the LEDs by induction through the conductive layer. A camera captures images of the RF-illuminated LEDs. Analysis of the images determines if the LEDs are defective or functioning. The RF-induction allows contactless testing of micro LEDs without direct electrical contacts that can damage the tiny chips.

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Imaging device for fast and stable testing of display screens to measure spectrum, brightness, chromaticity, and viewing angle optical characteristics on a single device. The analyzer has a turntable with a CCD electronic lens and conoscope lens mounted off-center. A rangefinder is at the center. A spectrometer, RGB camera, and filter switch are inside. The turntable rotates to image displays from different angles. The lens offset and through hole align with the turntable axis for consistent imaging. This allows simultaneous spectroscopy, colorimetry, and angular analysis of displays.

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Objective and precise method to measure the color depth of display devices using specialized equipment like signal generators, optical measurement devices, and data analysis tools. The method involves connecting the display device under test to a signal generator, measuring the brightness and grayscale response using optical equipment, and analyzing the data to calculate the color depth. This provides a more accurate and objective method compared to subjective evaluation or calibration tools that indirectly affect color depth.

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Display screen brightness and chromaticity measurement system that can quickly and accurately measure uniformity of a display screen without the limitations of point-by-point scanning or imaging array instruments. The system uses moveable area array cameras mounted on rails to scan and measure multiple sub-areas of the screen. Spectrometers connected to the cameras capture spectral data. This allows simultaneous, efficient measurement of brightness and chromaticity across the screen without vignetting or viewing angle issues. The cameras can move along rails to scan sub-areas, providing comprehensive coverage without manual scanning.

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Rapidly verifying many micro-LEDs quickly identifies and removes defective chips. The method uses a wafer-level verification technique, creating an LED verification substrate with contact bumps connecting to the LED chips. The verification substrate containing multiple verification chips is bonded to the LED wafer. Power is applied to the contacts to turn on the LED chips. Any chips that don't emit light are identified as defective and removed.

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Method for accurately measuring display characteristics like luminance, color, and spectral distribution of activated displays that have performance variations during and between measurements. The method involves configuring the measurement setup to perform each optical measurement as a sequence of identical measurements, like pairs of 2D images or spot measurements. Time-averaging the results from each sequence improves accuracy compared to single measurements. This compensates for the display's changing performance during measurements.

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An apparatus for inspecting illumination of micro LEDs that addresses the need to efficiently screen and inspect completed micro LEDs before transferring them from a wafer to a target substrate. The apparatus uses a surface-contact probe that touches the front surface of the micro LED assembly and supplies power to the LED ends to turn them on. An imaging unit photographs the LED assembly before and after power is supplied to inspect the overall illumination.

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Objectively quantifying and evaluating pixel saturation of LED displays to optimize image quality and reduce moire artifacts when capturing images of LED screens. The method involves calculating the pixel filling rate by dividing the display into equal blocks, counting pixels with brightness above a threshold, and comparing to the total. A higher filling rate reduces moire but excessively saturated displays lose sharpness. This provides an objective metric to determine optimal pixel saturation for LED displays.

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An apparatus for inspecting the illumination quality of micro LEDs. It uses a surface-contact probe to turn on the micro LEDs and interconnect them, then photographs the lit LED array to inspect their illumination.

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Calibrating LED display screens with mixed modules from different batches to eliminate brightness and chromaticity variations between batches without full rescreen calibration. After initial calibration, measure the corrected brightness and chromaticity of each module. Use these values to determine a common target for secondary calibration. Then, apply the target to uniformly correct the entire screen. This avoids assembly and site calibration for mixed screens by leveraging the initial calibration data.

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Donor substrates and conductive architectures for on-wafer testing of micro LED display panels. The architectures aim to allow testing of the micro LEDs before transfer to identify good devices. They involve conductive stabilization structures to support and electrically connect the LEDs on the donor substrate. This enables testing of the micro LEDs while still on the donor substrate and prior to transfer to the final display substrate.

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A method of producing microLED displays that allows efficient and accurate mass transfer of microLED chips onto a display substrate. It involves probing and measuring the chips to create a database of chip characteristics. The chips are then transferred en masse using an expanded tape to match bonding pad spacing. This avoids individual pick-and-place and sorting steps.

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LED display unit yin and yang color measurement device and method that enables accurate and automated measurement of color non-uniformity in LED displays without manual participation. The method involves using light collectors on opposite sides of the display to capture light emitted by the LEDs. By comparing the signals from the collectors, the brightness difference between areas of the display can be determined to identify yin and yang color issues. This provides a quick and efficient way to assess and improve display uniformity without manual intervention.

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A display screen chromaticity and brightness testing device for efficiently and accurately measuring the color accuracy and brightness of display screens. It uses a control box with multiple test stations arranged on the top cover. Each test station has a light source, color filters, and sensors to simulate specific display conditions and measure the screen's response. This allows automated, repeatable testing of multiple displays without manual intervention. The control box coordinates the testing and collects the data for analysis.

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Chromaticity measurement method and device for calibrating LED tiled displays with high accuracy and convenience. The method involves using a combination of imaging sensors and spectrometers to measure color and spectrum at multiple regions of an LED tiled display. It utilizes partially transparent and partially reflective mirrors to separate outgoing light and direct a portion to the imaging sensor for color analysis and another portion to a spectrometer for spectral measurement. This allows accurate chromaticity calibration of the display by leveraging the spectrometer data to correct the imaging sensor measurements. The removable spectrometer design enables easy measurement of different display regions.

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Pick and place apparatus for testing LEDs during production that allows faster and more compact LED testing compared to traditional methods. The apparatus uses a bond head with a translucent portion that allows light from the LEDs to pass through to an optical sensor. This allows the LEDs to be optically tested while they are being picked and placed for electrical testing. The optical characteristics are used to sort the LEDs into bins with similar optical properties. This enables more uniform displays by bonding LEDs from different bins with matching optical characteristics.

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Automated method to test display brightness, contrast, and color temperature using a built-in display mode to reduce external signal interference. The method involves connecting a display under test, a scanner, a color analyzer, and a computer. The computer sends test patterns to the display, scans the display with the scanner, and measures color using the analyzer. It calculates average and minimum brightness values from multiple points to determine display brightness.

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