| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 102 === The ultrasonic wire bonding process probably causes fracture and failure of the optoelectronic and microelectronic devices. The wire bonding quality of the device depends on bonding parameters. In this thesis, acoustic emission technology was used to real-time monitor the stress wave signals suddenly released from stick and slip of the capillary tool on the contact surfaces. The contact force induced by the tool on the bond pad was measured by piezoelectric force sensor.
The weld time takes several to tens milliseconds during the ultrasonic welding process. The bonding wire of greater diameter requires higher power output and longer duration. The larger normal contact force on the bond pad due to application of the capillary tool, the greater friction will be yielded. More energy is essentially transferred into welding energy for wire bond, plastic deformation of the free air ball and bond pad, as well as acoustic emission energy. High-frequency acoustic emission signals have been found in some specimens in accordance with the spectra carried out by short time Fourier transform. Unfortunately, no defects were observed in the small amount of specimens by using focused ion beam technique and scanning electronic microscope. Further specimens are needed to assure validity of acoustic emission monitoring. Experimental evidence indicates that acoustic emission energy could be a notable index for quality assessment. Successful wire bonds usually appear in case that the acoustic emission energy is in the range of 6 to 12 (mV)2sec and occupies 10% energy delivered by the transducer.
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