Issue link: https://iconnect007.uberflip.com/i/1024460
62 PCB007 MAGAZINE I SEPTEMBER 2018 Figure 6: Different geometries requiring different chemistry/process parameters/tools for copper plating. Table 3: Critical attributes/bump shapes for various plating applications. Table 3 summarizes critical attributes and the various bump shapes that are application specific. It has to be stated that a one-fits-all applica- tion chemistry and its needed equipment con- figuration will be hard to find, if at all. Befo- re diving into the depth of copper pillar tech- nologies and the related development routines, a closer look at the generic hydrodynamics of any pillar feature during electroplating/filling is shown in Figure 7. Developing the adequate plating chemistry (additives, basic concentrations copper/sulfuric acid/chloride) with respect to plating current 1 Applications Critical Plating Attribute Bump Shape RDL Coplanarity Flat to domed on flat substrate Micro bumps Coplanarity Flat on passivation substrates, domed on flat substrates Cu Pillars Coplanarity at high speed (≥3.5 mm/min) Flat on passivation substrates, domed on flat substrates Macro bumps Bump shape control & speed Flat to domed on passivation substrates Mega bumps Coplanarity, very high speed (>6 mm/min) Flat to dished, to slightly domed on flat substrates Filled via / TH "Post" shape control & speed Flat to dished, low surface copper Figure 7: Diffusion zone and limiting current govern any pillar copper plating. (Source: AMAT, Kalispell MT)