Wafer-Level LED Test System
MLEDTS-50

This wafer-level LED test system enables high-precision evaluation of LED chips while they remain on the wafer. It accurately measures electrical and optical parameters, including current–voltage–optical output (I-V-L) characteristics and emission spectra.
The system incorporates a pulse driver capable of delivering currents of up to 500 mA with pulse widths as short as 1 μs, enabling characterization with reduced thermal effects on the LED chips. This allows highly reproducible analysis of subtle parameter changes and light-emission efficiency.
Wafer-level measurement also offers the significant advantage of evaluating chip characteristics before dicing, helping shorten development cycles and accelerate feedback.
Note: The photodiode rise time is 5 μs or longer.

■Specifications

Item	Description
Sample Stage	Wafer size: Up to 2 inches X/Y travel: ±20 mm per axis
Platen	Vertically adjustable; travel: 4 mm
Probe Needles (Coaxial Probes)	Material: Tungsten Tip radius: 12.5 μm Quantity: 2
Manipulators	X/Y/Z travel: 10 mm per axis Travel per rotation: 250 μm per axis Quantity: 2
Stereo Microscope	Magnification: 7×–45× Illumination: LED ring light
Optical Detection Unit	1. Photodiode (spectral response range: 200 nm–1100 nm) 2. Optical fiber probe head
Drive Current Output Unit	Drive current ranges: 500 mA / 200 mA / 100 mA Maximum output voltage: 20 V Drive mode: CW / Pulse Minimum pulse width: 1 μs Maximum pulse period: 6 ms Maximum duty cycle: 50% Setting resolution: 0.1 μs
Output Voltage Detection	Voltage measurement ranges: 24 V / 12 V / 6 V / 3 V Measurement resolution: 1 mV
Detected Waveform Monitor Terminals	SYNC: Outputs the reference waveform during pulsed operation. DET: Outputs the photodetector photocurrent waveform. VF: Outputs the detected voltage waveform. IF: No detected current waveform output is provided.
Measurement Parameters	I-V-L (current–voltage–optical output) characteristics
Spectral Measurement	Wavelength range: 250 nm–850 nm Resolution: 1 nm (theoretical value)
Standard Measurement Software	Included

■IVL Characteristic Measurement Data

■Emission Spectrum Measurement Data

■Pulse Waveforms Measured with an Oscilloscope and Current Probe

*Specifications and appearance are subject to change without notice for product improvement.

■About LED IVL Characteristics

LED IVL characteristics are important indicators for comprehensively evaluating the electrical and optical performance of LED devices. They describe three relationships: current–voltage (I-V), current–optical output (I-L), and voltage–optical output (V-L).
I-V characteristics are measured by observing how the current changes as voltage is applied to the LED. They reveal fundamental electrical properties such as turn-on voltage and internal resistance. The characteristic nonlinear diode response, in which current rises sharply above a certain voltage, is used to assess initial device characteristics and identify defective devices.
I-L characteristics describe the relationship between the current supplied to an LED and the resulting optical output. They are used to evaluate the onset of optical output, slope efficiency, and light-emission efficiency. These characteristics help determine the optimum drive current and identify optical output saturation or degradation under excessive current.
V-L characteristics describe the relationship between voltage and optical output and are generally derived by combining I-V and I-L measurement results. They provide information useful for understanding power efficiency under actual operating conditions, such as mW/W or lm/W, and support energy-efficient design and the selection of operating conditions that reduce heat generation.
High-precision measurement and analysis of these IVL characteristics play a vital role in evaluating LED performance, optimizing product development, and supporting quality control and reliability testing.