Key steps from laboratory towards mass production: Optimization of electroless plating process through numerical simulation

The electroless plating process is probably one of the most promising methods to overcome the barriers of the solder technology in scaling-down fine-pitch interconnection in the chip packaging industry. To optimize this process, we propose the usage of numerical simulation as a key step towards mass production. This study develops two fundamental simulation models for a rectangular and diamond pattern of pillars, respectively. For both arrangements, the pressure drop and further flow characteristics are investigated dependent on the following parameters: pillar diameter D, pitch-to-diameter ratio S/D and height-to-diameter ratio H/D and superficial velocity U. The results show that a lower pressure drop can be achieved for higher values of these three geometrical parameters. The flow in a rectangular pattern is more likely to form vortices between the wake and front region of the pillars and to form a focused stream between the side areas of the pillars for high D, low S/D, high H/D and high U. The diamond array is less likely for vortex generation and favors to form an S-shaped stream through the arrangement of pillars. However, the pressure drop of the diamond pattern tends to be considerably higher compared to the rectangular counterpart for large D, high S/D and high H/D due to enhanced stagnation forces. Moreover, the developed numerical models show a good match with experimental data from the literature.