Controlled Energy Testing: Clarity
With the Vf varying by 19% across a typical LED wafer, using constant current mode only for testing means that power input to a device will also vary at 19% across a wafer. Therefore, when measuring optical power output across a wafer, true optical power is obscured by process variation on that wafer. Therefore lot to lot or product to product comparisons are tainted.
LEDs, though called a light emitting diode, is more appropriately an energy conversion device, taking electrical energy and converting it to optical energy. Therefore, testing using constant current mode doesn’t adequately describe the input energy into the LED.
Controlled energy testing uses a software controlled loop to correct the level of constant current for each device’s forward voltage in real time, so that power is kept at a constant level. Therefore energy into the device is controlled and known or measured, and a true efficiency can be calculated.
Controlled Energy Integrated Into the Cube 7010
Additionally with the Op-Test Cube 7010 system, the energy in is tightly synchronized with a spectrometer reading to allow for more precise readings of luminous efficacy. Tight synchronization of the spectral and electrical readings, combined with automation of testing, can allow fast testing speeds and throughput for production needs.
Using Controlled energy we have found has gotten rid of instrumentation jitter and brings consistency to spectral data over a wafer/lot.
U.S. Patent No. 8,593,148 and 9,442,155B2, Australian Patent No. 2010281408, Chinese Patent No. ZL2010800446807, Taiwan Patent No. 440867, and other patents pending.