The preferred insoluble anode is stainless steel and relatively little difficulty arises.
The archetype anode is graphite which is essentially cheap and which by reacting as an otherwise insoluble anode with the anode product oxygen can reduce the thermodynamic anode potential.
Insoluble anodes usually generate oxygen (chlorine is possible in chloride solutions) in completing the circuit but may also oxidise metal ions to a higher valency state, raise dissolved oxygen levels, oxidise additives and complexants (eg.
It is clearly necessary that insoluble anodes are not attacked, either physically by spalling or chemically by solution constituents, because this leads to solution contamination, and that they allow high conductivity passage of current.
Watch for new developments regarding a system that will fill the via and simultaneously plate the through-hole, using insoluble anodes
Some processes work best with insoluble anodes
because they are cleaner, create less nodules and reduce the required maintenance that would be needed if soluble anodes were used.
The electrolytic cells use the conventional, insoluble anodes
, but rather than use starting sheets to receive the cathode deposit, the Isa process uses 316L stainless steel blanks.
PCBs (size: 500 mm x 400 mm) with blind microvias ([empty set]: 100 [micro]m, depth: 80 [micro]m) were copper-plated in a 1400-litre test module equipped with insoluble anodes.
The electrolyte is used under direct current conditions and with insoluble anodes at a maximum temperature of 22[degrees]C.
Here the requirements are very high current densities on insoluble anodes
, which must have long life and high physical strength.
These include the use of insoluble anodes
and engineered fluid delivery devices such as educators or nozzles designed to create impinging flow on panel surfaces.