Standardization of LED Thermal Characterization

Abstract

The Chapter discusses the increasing need for a more sophisticated thermal characterization of LEDs (Light Emitting Diodes) and LED-based products. It goes without saying that the LED-business is growing exponentially, in fact, much faster than analysts predicted five years ago. Unfortunately, until recently the progress in thermal characterization has not kept pace. The situation was a serious problem until the first component level LED thermal testing standards were not published. As these standards are relatively new there are still manufacturers who are not yet aware of the new testing procedure and think they can publish whatever thermal information they want. The problem also still exists for the experienced user because the thermal data that are published are often rather useless in practice when accuracy is at stake, and accuracy is needed for an educated guess of expected performance and lifetime. This situation has much in common with the one the IC-world was facing almost 20 years ago. Provided the manufacturers want to cooperate, it is relatively easy to build upon the experience gained in the IC-business and their standard protocols that are in use worldwide. In 2008 the JEDEC JC15 committee on thermal standardization of semiconductor devices decided to take action and created a task group to deal with thermal standardization issues of power LEDs. CIE has also created new technical committees (e.g. TC2-63, TC2-64) which also aim to address thermal issues during measurement of high brightness / high power LEDs. The Chapter describes novel test methods which form the basis of new measurement guidelines including combined thermal and radiometric measurement of LEDs. In 2012, some new thermal testing standards were published, discussed in Appendix B. Initiatives to arrive at compact thermal modeling standards are also covered.