HEAT PULSE CHARACTERIZATION AND MEASUREMENT FROM A XENON FLASHLAMP FOR PHOTONIC CURING APPLICATIONS
Photonic curing is a widely adopted method to thermally process thin films on flexible substrates for producing flexible electronic circuits. Photonic curing uses short pulses of light from xenon flashlamps to process thin films much more rapidly than traditional methods. The pulses are characterized by pulse shape, duration, and time in between pulses. The ability to model photonic curing is important for engineers and designers seeking to optimize process goals. The process is modeled with the transient heat conduction equation using a heat flux boundary condition, but the predicted temperature distributions are only as accurate as the heat flux model. In this work, we attempt several approaches for characterizing heat pulse waveforms used in photonic curing tools. The first approach solves an LRC circuit for the lamp power based on an expression for the voltage drop through the xenon lamp provided by the lamp manufacturer. The second method replaces the expression provided by the lamp manufacturer with an empirical model based on data taken from photonic curing tools. This approach requires calibration to the specific tool, but provides waveforms that compare better with the experimental data. Finally, an in-situ temperature sensor is developed. The sensor is a resistance temperature detector (RTD) type. The recorded temperature history is used as a boundary condition in the heat conduction equation to deduce the pulse waveform. The
temperature sensor is the most accurate method for characterizing the waveform, although the empirical method developed in this effort also provides an acceptably accurate model.