Capacitive Field-Plate Testing for High-Throughput LED Arrays
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Solution Overview
Problem
Existing LED manufacturing processes face challenges in functionally testing millions of devices without direct electrical contact, particularly for micro-LEDs, which are crucial for efficient manufacturing and quality control.
Innovation Solution
A non-direct electrical contact method using a capacitive current injection (C²I) approach with a dielectric-coated field plate and specific voltage waveforms to inject current into LED devices, allowing parallel functional testing through capacitive coupling and image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual contact probes are used to test each LED device, then measurement precision is improved, but device complexity and manufacturing time increase significantly
Solution Approach 1:
The patent segments the testing function into two parts: a common contact that connects to all devices simultaneously, and individual device identification through spatial mapping. This allows parallel testing of multiple devices while maintaining individual measurement capability through image capture and pixel-to-device correspondence.
Solution Approach 2:
The patent uses an optical copy (image) of the device array to obtain functional information, rather than making physical electrical contact with each device. The image serves as a non-contact representation that captures the functional state of all devices simultaneously, eliminating the need for individual electrical probes.
2Measurement precision
If individual contact probes are used for each LED device, then functional testing accuracy is improved, but the time required for testing increases
Solution Approach 1:
The patent employs periodic pulsed voltage applied to the common contact to drive current through LED devices in a time-resolved manner. By synchronizing the pulse timing with image capture, the system achieves functional testing of all devices within a single periodic cycle, dramatically reducing total testing time compared to sequential individual probing.
Solution Approach 2:
The patent maintains continuous functional testing capability by keeping the common contact connected to all devices throughout the process. The pulsed voltage and continuous image capture create an uninterrupted testing flow where all devices are tested simultaneously in each cycle, eliminating the idle time associated with moving between individual devices.
3Productivity
If non-direct electrical contact method is used, then manufacturing efficiency is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent introduces light (optical signal) as an intermediary to transfer functional information from the LED devices to the sensor. Instead of direct electrical contact, the electrical function of the LEDs is converted to optical signals that can be captured non-contactually, maintaining measurement accuracy while enabling parallel testing of all devices.
Solution Approach 2:
The patent replaces the mechanical/electrical probing system with an optical detection system. The physical contact of electrical probes is substituted by optical imaging, which captures functional information through light emission from the LEDs, thereby eliminating mechanical wear and enabling simultaneous non-contact measurement of all devices.
4Ease of operation
If common contact is used for all devices, then ease of operation is improved, but individual device testing capability deteriorates
Solution Approach 1:
The patent adds a spatial dimension to the common contact system by using two-dimensional image capture. While the electrical connection remains common to all devices, the optical detection resolves individual device information through spatial mapping, allowing both simplified operation and individual device measurement to coexist.
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 functional testing of large numbers of LED devices, including micro-LEDs, with high throughput and scalability, reducing the need for individual contact probes and improving manufacturing efficiency.
Implementation Method 1
A non-direct electrical contact method using a capacitive current injection (C2I) approach with a dielectric-coated field plate and specific voltage waveforms to inject current into LED devices
Implementation Method 2
Light emitting diode (LED) devices... functionally test the LED devices to achieve one or more of the following: yield evaluation, binning, device repair/correction and collecting data
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Embodiments relate to functional test methods useful for fabricating products containing Light Emitting Diode (LED) structures. In particular, LED arrays are functionally tested by injecting current via a displacement current coupling device using a field plate comprising of an electrode and insulator placed in close proximity to the LED array. A controlled voltage waveform is then applied to the field plate electrode to excite the LED devices in parallel for high-throughput. A camera records the individual light emission resulting from the electrical excitation to yield a function test of a plurality of LED devices. Changing the voltage conditions can excite the LEDs at differing current density levels to functionally measure external quantum efficiency and other important device functional parameters.