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This work applied the ultrasonic bonding to package flip chip GaN-based light emitting diodes (flip chip LEDs) on Si substrates.The effects of ultrasonic bonding parameters on the reliability of flip chip GaN-based LED were investigated.In the sequent aging tests,samples were driven with a constant current of 80 mA for hundreds hours at the room temperature.It was found that the electroluminescence (EL) intensity variation had a large correlation to the ultrasonic power,and then to the bonding temperature and force.A high bonding temperature and ultrasonic power and a proper bonding force improved the EL intensity significantly.It was contributed to a strong atom inter-diffusion forming a stable joint at the bonding interface.The temperature fluctuation in the aging test was the main factor to generate a high inner stress forming delamination at the interface between the chip and Au bump.As a result,delamination had retarded the photons to emit out of the LED packaging and decay its EL intensity.