LED Inspection via Non-Contact Photocharge Detection

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Solution Overview

Problem

The challenge lies in efficiently inspecting and distinguishing functional light-emitting diodes (LEDs) with extremely small sizes, as traditional methods require precise probe alignment and contact, which is difficult and time-consuming, and can lead to probe damage and reduced yield due to the small size of the LEDs.

Innovation Solution

An inspection apparatus that uses an illumination light source and a sensing probe to measure charge, electric field, or voltage distributions on LEDs, allowing for simultaneous irradiation and determination of electro-optical characteristics without physical contact, utilizing a medium layer that induces optical property changes to differentiate functional from non-functional LEDs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the probe size is reduced to match the small LED electrodes, then the measurement precision is improved, but the probe becomes more fragile and prone to damage

Engineering Contradiction:

Improveprobe alignment precisionVSAvoidprobe durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical contact probe system with an optical sensing system. Instead of using a physical probe that must contact the LED electrodes, the invention uses an illumination light source to emit light at a specific wavelength that generates photocharges in functional LEDs, which are then detected by a sensing probe. This substitution eliminates the mechanical contact and associated fragility while maintaining measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces light as an intermediary between the inspection system and the LED electrodes. The illumination light source emits light that interacts with the LED to generate photocharges, which then serve as the measurement signal. This intermediary approach allows indirect measurement without requiring direct physical contact between the probe and the fragile LED electrodes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If sequential probe contact is used for inspection, then the measurement precision is maintained, but the inspection time increases significantly

Engineering Contradiction:

Improveelectrode measurement accuracyVSAvoidinspection speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent merges multiple sequential measurement operations into a single simultaneous operation. By illuminating multiple LEDs with the light source at once and detecting their photocharge signals simultaneously through the sensing probe, the system inspects many LEDs in parallel rather than sequentially. This merging of operations dramatically increases inspection throughput while maintaining measurement accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs periodic illumination cycles where the light source emits light at specific time intervals to generate photocharges in batches of LEDs. This periodic action allows systematic inspection of large numbers of LEDs through repeated cycles of illumination and detection, improving overall inspection efficiency.

Inventive Principle:

Principle #19Periodic action

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 method enables rapid inspection of a significant number of LEDs, reducing the risk of probe damage and increasing efficiency by determining electro-optical characteristics through non-contact means, thus improving yield and reducing inspection time.

Implementation Method 1

The illumination beam has a sufficient light intensity so that the charge distribution, the electric field distribution, or the voltage distribution on the plurality of light-emitting diodes simultaneously illuminated by the illumination beam are close to a saturation charge distribution, a saturation electric field distribution or a saturation voltage distribution, respectively

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

The sensing probe is configured to measure a charge distribution, an electric field distribution, or a voltage distribution on the plurality of light-emitting diodes simultaneously irradiated by the illumination beam

Methodology Applied

Scientific EffectElectric field measurement: Electric Field

Data Source

PatentUS11474144B2Method for inspecting light-emitting diodes and inspection apparatus

Publication Date: 2022.10.18 IND TECH RES INST

AI summary

An inspection apparatus including an illumination light source, a sensing probe and a processing device is provided. The illumination light source emits an illumination beam to simultaneously irradiate the plurality of light-emitting diode. The sensing probe is configured to measure a charge distribution, an electric field distribution, or a voltage distribution on the plurality of light-emitting diodes simultaneously irradiated by the illumination beam. The processing device determines a plurality of electro-optical characteristics of the plurality of light-emitting diodes through the charge distribution, the electric field distribution, or the voltage distribution on the plurality of light-emitting diodes simultaneously irradiated by the illumination beam. Moreover, a method of for inspecting light-emitting diodes is also provided.