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NOVEMBER 2020 I PCB007 MAGAZINE 25 controlled impedance. Conventional HDI are panels with multilayer cores and buried vias with one or more outer layers of HDI. The via fill can be accomplished by button or dot plat- ing and may require planarization to level the surface. Microvias are typically pattern plated first; through-holes are plated second. A con- ventional plating cell can be used with either copper or insoluble anodes. Today, a pattern plate copper via fill can si- multaneously plate microvias and through- holes in a single cycle to a 4:1 aspect ratio. Ad- vanced HDI designs, including mSAP, and thin- ner panels are in mass production today using a single pattern plate cycle for via without pla- narization. The via-filled through-hole plating is best done with direct impingement solution flow and either copper or insoluble anodes. 6. Two-in-One RDL Plating These IC substrate fabrication chemistries are used to build redistribution layers that fan out the signal routing from the IC package for the final attachment to the PCB. These solu- tions are designed to fill smaller microvias (<65 µm wide x 35 µm deep) and laser-drilled X-vias in IC substrate core layers while provid- ing extremely tight trace profiles and trace/pad coplanarity in pattern plating mode. 7. Embedded Trace Plating These are chemistries formulated for very fine lines and spaces in pattern plating mode with extremely tight trace profile tolerances and coplanarity on IC substrates. These sys- tems are capable of plating lines down to 5 µm in width. 8. Pillar Plating These are chemistries used to build cop- per pillars for attachment of the IC package in place of solder bumps. These solutions are ca- pable of building copper pillars upwards of 200 µm in height at high plating speeds with con- trolled top profile and coplanarity. 9. Through-Hole Filling These are chemistries designed for use with pulse rectification to completely fill through- holes for core layer buildup and thermal man- agement. 2. Do the formulations and names change depending on whether the chemistry is for horizontal versus vertical conveyorized tanks, vertical rack-type tanks, and whether pulse- plating or insoluble anodes are used? If so, how do you name them? In general, the formulations will change depending upon the application rather than the equipment in which it is used. For in- stance, via filling and through-hole plating re- quire very different types of additives in or- der to perform their respective functions. Via filling requires additives that preferentially adsorb on the surface of the panel to suppress surface copper buildup while other accelerating additives adsorb in the low cur- rent density microvia bottoms to increase the plating rate, thus giving the bottom-up fill. If these additives were used in conventional DC plating of through-holes, one would end