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36 The PCB Magazine • May 2015 cell at bath ages from 0 to more than 100A.h/L. Consistent dimple depth of less than 10 μm was maintained with board thickness of 100 μm and 200 μm. This process may be used in either panel or pattern plate processes. Table 4 demonstrates the capability of the process to fill through- holes when used in a pattern plate mode. Table 5 shows results of tests performed in AEL equipment of deep through-hole fill- ing, which reveal the capability of the Mi- crofill THF process. This test was performed at 2.5 ASD with a copper surface deposition target of 25 μm. All holes were fully filled with copper with an acceptable dimple depth of < 12.0 μm. Table 6 also demonstrates that the bath can also be utilized for the metallization of blind microvia (BMV) with surface copper thickness of less than 15 μm. Bump formation on top of the blind microvias can be minimized by modi- fying such plating parameters as solution agita- Figure 11: Through-hole dimple depth as a function of bath age and panel thickness in vertical batch plating cell. Table 5: Deep holes filled using the Microfill THF bath. ELECTrOPLATING THrOUGH-HOLES wITH DIFFErENT GEOMETry continues FEaturE