Ultrasonic assisted thermoforming for rapid fabrication of a microspeaker diaphragm

The present study uses ultrasonic vibration energy as an energy source in thermoforming of a microspeaker diaphragm. Microspeaker diaphragms have many applications in mobile media, and are generally manufactured from a thin polymer film using the thermoforming process. Thermoforming is a polymer processing method in which a polymer film is heated and softened to be formed into a desired shape. This process requires long cycle time because the polymer film should be heated enough to be softened before forming, and should be cooled sufficiently to be solidified after forming. In this study, ultrasonic vibration is applied to a thermoforming plug from which thin polymer films are shaped. For this purpose, an ultrasonic plug is designed to resonate at the excitation frequency of ultrasonic waves, and is applied to the thermoforming of a microspeaker diaphragm that incorporates a number of micro-corrugations. Considering that the cycle time of the proposed ultrasonic-assisted thermoforming process is <20 s owing to its localized heating capability, it can be concluded that the proposed process is superior to the conventional thermoforming process, the cycle time of which was as long as 160 s.