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48 PCB007 MAGAZINE I JUNE 2018 observed at very high flow rate. A typical plat- ing was done under the conditions summa- rized in Table 1 and followed the process flow given above; this resulted in a via fill shown in Figure 5. A via with diameter of 150 µm and depth of 100 µm was seamlessly filled with- out any issue. Surface was flat, and the depos- it was bright with surface copper thickness at only 8−11 µm. Total organic content (TOC) of the bath was obtained for the fresh and aged bath. Accord- ing to the data summarized in Figure 6, the TOC did not change significantly over time and the fresh bath has very low TOC. Low TOC in the fresh makeup means, the bath will have prolonged lifetime and stability. Since the or- ganic buildup is very low with age, the bath requires less frequent carbon treatment. This makes the process more environmentally be- nign and hassle-free in terms of waste treat- ment. Compatibility of this via fill formulation in direct metallization was evaluated by plat- ing propagation panels. These are panels with eight through-holes alternatively connected and processed with a carbon-based direct met- allization layer. Maximum propagation result is eight: two regions for high current densi- ty and low current density were plated simul- taneously in a Hull Cell. According to the re- sults summarized in Figure 7, the formulation reported here has an excellent propagation at high current density area and low propagation at low current density area. A 1.6 mm thick through-hole panel was plat- ed to evaluate the micro-distribution. The mi- Figure 5: Typical via fill capability for different via diameter and depth at surface copper ~8–11 µm. Figure 6: Total organic content of the new bath and aged bath.