Product Code: ICA10_M406

Direct Joining of FPC and Metal Electrode by Pulsed Nd:YAG Laser
Authors:
Mohd Idris Shah Ismail, Okayama University; Okayama Japan
Yasuhiro Okamoto, Okayama University; Okayama Japan
Yoshiyuki Uno, Okayama University; Okayama Japan
Presented at ICALEO 2010

Laser micro-welding is widely used for the manufacturing process in the electrical and the electronics industries, where the demands for the miniaturization, the high strength and temperature resistance are constantly increasing. Recently, a flexible printed circuit (FPC) is expected as a connection technology between electrical conductors according to the improvement of reliability and controllability with diversification of the design concept. In this technology, it is required to weld a several tens µm in thickness of FPC and a several hundreds µm in thickness of metal electrode. This material combination accompanies the difficulty to control the welding due to the difference of thermal properties and heat capacity. In this study, the overlap welding of thin copper circuit on a polyimide film and a thick brass electrode was experimentally and numerically investigated by using a pulsed Nd:YAG laser, and a shearing stress of overlap welding was evaluated with and without the control of pulse waveform, which can achieve various heat input configurations. The results showed that the porosity was observed as the major weld defect during the welding process without a pulse control. However, the appropriate controlled laser pulse configuration of micro-welding can remove the welding defects during processing, improve the weld penetration stability and increase the weld strength. The mechanism of pulse forming is discussed including potential benefits for the use within the direct laser micro-welding process. It is clarified that the direct laser micro-welding of a thin copper circuit on a polyimide film and a thick brass electrode could be realized by using a proper control of laser pulse and heat input.