Issue link: https://iconnect007.uberflip.com/i/1050827
82 PCB007 MAGAZINE I NOVEMBER 2018 Via Fill: Concentration Levels Effect and CD Influence on Via Dimple It was established that an increase in bright- ener concentration led to an increase in dim- ple size. The wetter showed a minimal effect on dimple depth. Leveler results are inconclu- sive, although in most of the cases increasing the leveler concentration affected via filling, usually increasing via dimple. Increase in cur- rent density showed an increase of dimple size for 3 x 3 vias and a decrease in dimple size for larger size vias (Figures 6–8). A high concentration of organic additives and 10 ASF showed the best plating results. The optimization model could minimize and maximize throwing power and via dimple size. Enhanced TH microdistribution was achieved under optimal conditions for maximum throw- ing power: high brightener and leveler concen- trations, low CD, 10 ASF. A current density of 30 ASF caused cavities in 3 x 3 and 4 x 4 vias, in some cases. Experiments were designed to run under the conditions of the minimum and maximum dimple size and minimum and max- imum throwing power: • Max dimple (no voids inside the vias): 4.5 ml/l brightener, 5.0 ml/l wetter, 25.0 ml/l leveler, 10 ASF • Max throw power: 4.5 ml/L brightener, 15.0 ml/l wetter, 25.0 ml/l leveler, 10 ASF • Min dimple (no voids inside the vias): 2.5 ml/l brightener, 10.0 ml/l wetter, 15.0 ml/l leveler, 20 ASF • Min throw power: 0.5 ml/L brightener, 5.0 ml/l wetter, 25.0 ml/l leveler, 30 ASF The minimum dimple condition shows a large improvement from maximum dimple con- ditions; large differentiation. The maximum throw power percentage showed improvement from the minimum condition, but not consid- erable; small differentiation (Figure 9). Figure 6: Main effect plot 3 x 3 (75 x 75 mm); via dimple as a function of brightener, wetter, leveler, and CD. Figure 7: Interaction plot for 4 x 3 (100 x 75 mm) vias. Figure 8: Interaction plot for 4 x 4 (100 x 100 mm) vias. Figure 9: Throwing power interval plot of various sizes THs at min and max TP% conditions.