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84 PCB007 MAGAZINE I NOVEMBER 2018 Comparing maximum throw power and min- imum dimple conditions (two ideal conditions) resulted in a better tradeoff by targeting mini- mal dimple. Throwing power varies much less between the maximum TP condition and min- imum dimple condition (Figure 10) than dim- ple size between the two conditions (Figure 11). The throwing power was reduced slightly when running at optimized dimple conditions (minimum dimple). If dimple size and throw- ing power are critical, the best compromise is to operate under optimized dimple conditions. Throwing power and knee thickness in- crease as the TH AR decreases and the diam- eter increases, as shown for the 0.8-mm panel in Figure 12. The industry specification for a throw- ing power >75% and knee thickness >75% could be achieved under proper plating con- ditions for all sizes THs (0.15, 0.20, 0.25, and 0.30 mm), ARs of up to 5:1 in 0.8-mm panels or thinner 0.4-mm panels. However, the throw- ing power for thicker panels (1.2−1.6 mm) was measured to be below 75%. It usually was about 55–59% for 0.25-mm holes in 1.6-mm panels (AR = 6.4). Basic Copper Electrolyte (VMS): Enhanced Throwing Power To improve the throwing power for thicker boards, the inorganic component concentra- tions in the bath were varied, reducing copper Figure 10: Throwing power interval plot of various sizes THs at optimum conditions. Figure 11: Via dimple interval plot of various sizes vias at optimum conditions. Figure 12: TP min and knee as a function of hole diameter.