LED Thermal Characteristic Measurement via Voltage Transient Analysis
Solution Overview
Problem
Conventional methods for measuring thermal electric characteristics of semiconductor LED devices are time-consuming and not suitable for fast measurement, particularly due to the requirement for steady-state testing conditions and the complexity of measuring thermal resistance.
Innovation Solution
A method involving the provision of current to an LED device over a time interval, recording the voltage transient response with multiple time segments of different gradients, computing the voltage difference, and determining thermal-dependent defects, allowing for rapid measurement of thermal electric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional thermal measurement methods are used to ensure accurate thermal resistance measurement, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent applies periodic action by using pulsed current instead of continuous current for heating. The pulsed current is applied in periodic intervals, allowing the device to be heated rapidly during pulse periods and measured during off-periods, thereby reducing the total time required to reach thermal equilibrium while maintaining measurement accuracy.
Solution Approach 2:
The patent implements preliminary action by pre-characterizing the voltage-trans temperature relationship at different current levels before actual measurement. This pre-established calibration data allows for direct calculation of thermal resistance from voltage measurements without requiring repeated equilibrium measurements, significantly reducing measurement time while preserving precision.
2Measurement precision
If steady-state testing conditions are maintained for accurate TSP value measurement, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The method uses periodic pulsed current to rapidly achieve thermal conditions suitable for TSP measurement. By applying current in periodic pulses rather than maintaining continuous steady-state, the system can complete multiple measurement cycles in the time it would take to reach equilibrium once, thereby increasing productivity while maintaining measurement precision through the periodic sampling at optimal points in the pulse cycle.
Solution Approach 2:
The patent performs preliminary calibration to establish the relationship between voltage, current, and temperature before production measurements. This pre-established relationship allows for direct calculation of temperature from voltage measurements without requiring steady-state conditions during actual testing, enabling high-speed throughput while maintaining accuracy through the previously characterized TSP behavior.
3Measurement precision
If conventional two-step measurement process is used to measure temperature and thermal resistance, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the heating and measurement functions into a single integrated process. By using the same current pulse for both heating and voltage measurement, and by utilizing the voltage transient response during the pulse, the method combines what were previously separate heating-phase and measurement-phase operations into one unified measurement step, reducing process complexity while maintaining thermal characteristic measurement accuracy.
Solution Approach 2:
The patent performs preliminary establishment of the voltage-trans temperature relationship through calibration. This pre-characterization allows the measurement system to directly calculate thermal resistance from voltage measurements without requiring separate heating and measurement steps, simplifying the measurement process from two distinct steps to a single calculation-based approach that maintains precision.
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 fast and accurate measurement of thermal electric characteristics, reducing measurement time and improving the assessment of thermal performance in LED devices.
Implementation Method 1
a heating current, such as 300 mA, is provided to an LED device by a current source
Implementation Method 2
measuring a temperature sensitive parameter (TSP)... A forward voltage under the small current is measured as the calculation of the device temperature
Data Source
AI summary
The present disclosure relates to a method for measuring thermal electric characteristics of a semiconductor device, including the steps of: providing at least one current to the LED device over a time interval; recording a voltage transient response of the LED device, wherein the voltage transient response has a plurality of time segments different in gradient; computing a voltage difference from one of the plurality of time segments in the voltage transient response; and determining whether the LED device is defective based on the voltage difference, wherein the voltage difference is thermal dependent. The present disclosure also provides a testing method for defining a plurality of time segments.