Flexible printed circuit boards laser bonding using a laser beam homogenization process

A laser micro-bonding process using laser beam shaping is successfully demonstrated for flexible printed circuit boards. A CW Ytterbium fiber laser with a wavelength of 1070 nm and a laser power density of 1–7 W/mm2 is employed as a local heat source for bonding flexible printed circuit boards to rigid printed circuit boards. To improve the bonding quality, a micro-lens array is used to modify the Gaussian laser beam for the bonding process. An electromagnetic modeling and heat transfer simulation is conducted to verify the effect of the micro-lens array on the laser bonding process. The optimal bonding parameters are found experimentally. As the measured temperature ramp rate of the boards exceeds 1100 K/s, bonding occurs within 100–200 ms at a laser power density of 5 W/mm2. The bonding quality of the FPCB is verified with a shear strength test. Process characteristics are also discussed.

► A laser micro-bonding process using laser beam shaping.
► A CW Ytterbium fiber laser is employed as a local heat source for bonding.
► An electromagnetic modeling and heat transfer simulation is conducted to verify the effect of the micro-lens array.
► The bonding quality of the Flexible Printed Circuit Boards is verified with a shear strength test.