PWB Processes: Acid Copper DC Electroplate

Acid Copper for "Via filling" Via Filling connects the different layers in buildup technology (stacked vias and vias in pad) manufacturing, enhancing the long-term reliability of the PCB and the package.

Thru-Cup EVF-R

EVF-R is a unique DC (direct current, no pulse) acid copper plating system for filling blind vias, connecting layer 1 to layer 2 and occasionally to layer 3. It is designed to plate aspect ratios of 1:1 or less. With diligence and current time manipulation, the EVF-R system is effective in plating aspect ratios higher that 1:1, (vias whose depth exceeds the diameter of the ablated hole).

EVF-R is comprised of a combination of organic additives that work with a specific acid to copper ratio in the bath. The organic components include a brightener (accelerator/ grain refiner), a carrier (a wide range suppressor) and a leveler (a unique surface suppressor). All components are readily analyzable using CVS. EVF-R does not require additives in the pre-dip.

The EVF-R plating process is compatible with both air agitation and airless agitation (E-ductor). It is also compatible with soluble and insoluble anodes. The insoluble anodes are titanium, coated with a mixed metal oxide (MMO).

For best performance, the chemistry must be augmented with solution dynamics that can preferentially maintain the leveling component at the surface, in contrast with the bottom of the via. The leveling component suppresses plating on the surface and allows plating to be accelerated in the bottom of the via. When setting up the EVF-R bath, cell design, solution dynamics and appropriate rectification must be optimized for best results.

The choice of current density (ASF) and dwell time are determined based on the degree of difficulty (hole diameter vs depth). Occasionally, it may be necessary to increase the current density at the back end of the plating cycle.

The EVF-R plating sequence must be preceded by a low surface tension acid cleaner with high wetting capability. The function of the cleaner is to evenly wet the hole and facilitate the removal of entrapped air that could interfere with plating. In addition, the cleaner removes oxidation from the surface to be plated.

Thru-Cup EVF-N

EVF-N plates copper in through-holes and blind vias simultaneously, reducing process time by 50%. It delivers exceptional performance for blind via diameters smaller than 150 micrometers.

Designed for soluble anodes, it is suitable for both pattern and through-hole plating. The process uses DC current, which minimizes both equipment cost and chemical use. Thru-Cup EVF-N is a unique organic additive system, which fills blind vias with electroplated copper using vertical plating equipment.

Additive components are readily analyzed using CVS and Hull cell techniques. The organic additives are very stable and do not require regeneration. Carbon treatment is recommended at a frequency of 2000AH/L of bath (approximately annually). The ratios of the inorganic components are different from traditional acid copper plating.

Thru-Cup EPL

Thru-Cup EPL is a “High Throwing Power“ acid copper additive for printed wiring board plating applications. It was engineered for high aspect ratios with fine line circuitry. It has the simplicity of DC plating with results that can easily compete with the more complex waveforms of pulse plating. The chemistry is very stable and does not require continuous regeneration.

The process produces a fine-grained equiaxed copper deposit. The leveling capability of Thru-Cup EPL overcomes irregularities on the substrate and prevents nodule growth. The deposit is bright and ductile with excellent elongation, tensile strength and metallurgical properties. Thru-Cup EPL maintains these metallurgical properties, plating as low as 5 ASF (0.5 ASD) and as high as 25 ASF (2.5ASD).

Thru-Cup EPL is a two-component system. The suppressor incorporates a carrier and a leveling component and controls deposit thickness uniformity; the brightener is the grain-refining additive. The solution components and additives have a wide operating window and are easily controlled by standard analytical methods.

Thru-Cup EPL is compatible with both air agitation and airless agitation (E-ductor). It is also compatible with both soluble and insoluble anodes. The insoluble anodes are composed of a titanium mesh coated with a mixed metal oxide (MMO).

Uyemura Thru-Cup EPL Acid Copper and ENIG Pass More Than 2000 Cycles of IST Testing

Thru-Cup ETN

An acid copper additive for printed wiring board plating. It is ideally suited for vertical conveyorized lines where plating speed is critical, and plates with current densities as high as 40 ASF or 4.0 ASD.

The process produces a fine-grained equiaxed copper deposit. The leveling capability of Thru-Cup ETN overcomes substrate irregularities and does not allow nodule growth. The deposit is bright and ductile, with excellent elongation, tensile strength and metallurgical properties. The chemistry is exceptionally stable and does not require continuous regeneration.

Thru-Cup AC-90

A single-component acid copper additive system designed for simplicity. It is a mixture of carrier and brightener that has a wide operating window for general-purpose plating. The additives are mixed in the proper ratio for use as a single component system.