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.

Automated summary

The study compares the numerical simulation models of rectangular and diamond arrays of pillars and finds that larger pillar diameter, lower pitch-to-diameter ratio, higher height-to-diameter ratio, and higher superficial velocity can achieve lower pressure drop. The rectangular pattern is more likely to form vortices between the wake and front region of the pillars and form a focused stream between the side areas of the pillars. On the other hand, the diamond pattern is less likely to generate vortices and favors to form an S-shaped stream through the arrangement of pillars. The pressure drop of the diamond pattern tends to be higher for larger pillar diameter, higher pitch-to-diameter ratio, and higher height-to-diameter ratio.