Abstract
Ultrasonic precise bonding is an emerging technology in the application of polymer micro-assembly. The propagation of ultrasound changes with the interfacial polymer physical state in the ultrasonic bonding process. So the ultrasonic guided wave is an effective parameter to in-situ monitor the fusion degree. The time-frequency characteristics in the ultrasonic guided wave are analyzed by vibration analysis methods. The polymer interfacial fusion is online visual monitored by the high-speed HD camera. The fusion behavior of the thermal melt interface and the time-frequency characteristics are analyzed and correlated. Results indicate that the change of the interfacial thermal melt state is related to the time-frequency characteristics of the ultrasonic guided wave. The generation of the melting zone, the fusion of the melting zone, the rotation of the micro-device, the generation or disappearance of local air bubbles all lead to the changing of the harmonic frequency and intensity in the ultrasonic bonding process.
Highlights
Since the 1990s, polymer micro-device has been widely used in the manufacture of MEMS devices such as microfluidic biochips, micro fuel cells, micro-valves, and micro-pumps due to high forming efficiency and light weight [1, 2]
Several bonding techniques have been applied in micro-nano manufacturing such as thermal bonding [3], laser bonding [4], adhesive bonding [5], microwave bonding [6], and ultrasonic bonding [7]
The precise bonding experiment was carried out based on the test rig
Summary
Since the 1990s, polymer micro-device has been widely used in the manufacture of MEMS devices such as microfluidic biochips, micro fuel cells, micro-valves, and micro-pumps due to high forming efficiency and light weight [1, 2]. Ultrasonic bonding technology uses high-frequency periodic mechanical force to move two parts relative to each other and generates heat locally by interface friction and periodic energy loss of materials. Jingmin Li et al [13] designed an energy director structure and self-balancing jig to improve the uniformity of the microchannel height and provide an effective method for large-scale ultrasonic bonding of microfluidic devices. Zhang et al [15] verified the effectiveness of a new thermally-assisted ultrasonic bonding method for polymer Micro/NanoElectro-Mechanical Systems (M/NEMS) through bonding experiments on PMMA microfluidic chips. Compared with the traditional time, pressure, energy, and other parameter control methods, the monitoring of the thermal melt interface provides an effective method for the ultrasonic guided wave in this study.
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