Junction Temperature

Junction Temperature is the basis for every semiconductor device design.  Knowledge of junction temperature and thermal resistance is useful at all stages of semiconductor production from R&D to characterization and quality assurance. End user designers rely on accurate junction temperature data that is published on datasheets for their designs. With proper junction temperature measurements and/or data, R&D can be reduced and other design considerations may be optimized. For example, with accurate junction temperature data, proper thermal management is possible. With proper thermal management, losses due to support issues may be avoided.

Thermal Measurements

Thermal measurements are used in a variety of applications involving LEDs, laser diodes and other semiconductor devices. Thermal measurements, specifically junction temperature, are useful at all stages of semiconductor production from design and development to quality assurance. The basis for every semiconductor data sheet and end user design is junction temperature.  

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Junction Temperature Cross Section
Junction Temperature Cross Section

Tj Measurement

Tj Measurement is most accurate when using JEDEC’s Electrical Test Method (ETM), described in JESD-51-14 and JESD-51-51. This method uses the LED or laser’s forward voltage (Vf) vs temperature characteristic to infer temperature. 

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Vektrex Sample Junction Temperature Waveform

Tj Measurement Toolkit

The Tj Measurment Tookit is an optional add-on to the SpikeSafe Pulsed Source Measure Unit. It simplifies and automates junction temperature measurement for LED or laser devices using JEDEC’s Electrical Test Method (ETM).

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Vektrex Junction Temperature Software with Y Intercept Capture

Application Note: Measuring LED Junction Temperature (Tj)

Manufacturers and solid-state lighting developers are driving LEDs to higher power levels. As more energy is
pushed through the LED diode junction, heat removal becomes a critical issue. To assure device lifetime, quantum efficiency and LED color, the diode junction temperature (Tj) must be maintained within a specified band.

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Vektrex Junction Temperature Tj Measurement System

SpikeSafe SMU Featured in LEDs Magazine Junction Temperature Measurement Article

LED’s magazine’s April 2020 issue features the article Simpler LED Junction Temperature Measurement, written by Vektrex CTO Jeff Hulett. The article discusses how the SpikeSafe SMU solves a critical problem for luminaire manufacturers – how to make in-situ junction temperature measurements.

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Is Your Light Measurement Method Undervaluing Your LEDs?

The LED industry is facing a roadblock that threatens its continued rapid evolution. Heating effects are making it nearly impossible to accurately measure the performance of new LEDs.

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L vs I Sweep of AlGaInP LED - Nominal L-I_50ms Single Pulse Sweep_DC Sweep
L vs I sweep of Osram LY W5SM AlGaInP LED showing droop caused by junction heating.