Parameter Optimization of Pretin Printing Process of Wireless Communication Module

For system manufacturers, packaging of the ball grid array (BGA) of wireless communication modules can be performed via solder paste printing. As reballing can be conducted via the pretinning process, it can be compatible with its existing surface mount technology (SMT). This study referred to the Taguchi experimental design to plan its experiment. Three quality characteristics related to the consistency of the solder volume are applied for printing, that is, the standard deviation of the deposition volume of solder paste on all bonding pads of a single component, the coplanarity of the solder balls of the component, and the height range of the solder ball of a single component, which were regarded as the response values. Important design and process parameters related to the pretinning process and the relative location of the bonding pads of components on a connecting board are considered as the controlling factors. Then, this study applied and integrated the results of two multivariate analysis methods, i.e., gray correlation of the principal components and a technique for order preference by similarity to ideal solution (TOPSIS), in order to determine the ideal solution and propose the optimal parameter combination: general squeegee: pressure 40 N and speed 30 mm/s; steel: separation distance 3 mm, speed 2 mm/s, and aspect ratio 0.17; and cleaning frequency: cleaning of stencils after the printing of every two boards. This method effectively improves the control of the solder volume in the pretinning process and meets the acceptance criteria of manufacturers.