Plastic ball grid array reflow using a fast-modulated CW laser

Plastic ball grid array reflow using a fast-modulated CW laser is studied. A CW/Q-switched Nd:YAG laser is modified to work in the fast-modulated CW m ode. Sn-Pb eutectic solder balls with a diameter of 760 mum and Au-Ni-Cu so lder pads are used in the study. By varying the laser power and the laser-o n time, respectively, the solderable parameter region of laser reflow for t he solder balls and the solder pads is obtained. Shear strength tests are a lso performed to find out the optimal reflow parameters. The measured shear strength is higher than 1500 gf, with the maximum value over 1900 gf. An e nergy equilibrium model is proposed to compare the solderable region predic ted theoretically with the experimental results and to estimate the average temperatures of solder joint under the given experimental conditions.