Electroplating operations are filtration intensive because a dirty plating solution can cause cosmetic defects and actual functional failure of the plated part. For example, a chrome plated part for an automobile must be visibly pleasing to the customer, and also must protect against corrosion. Defects on a circuit board would render the electronics useless.
Operations producing metal parts, for example automotive or appliance parts, can have plating operations. Even factories that don’t have “plating” in the company name or main description of the product can have significant plating operations. Printed circuit board (PCB) manufacturers have plating operations as well.
Contamination can be particulate or chemical in nature. For particulate contaminants, polypropylene is a very common filter material because of its broad chemical compatibility with many of the fluids employed for plating and PCBs: water, plating solutions, resists, resist strippers, etchants, and cleaning solutions (such as hydrogen peroxide). Polypropylene is compatible with many acids and bases. Melt Blown (Delta Pure Filtration MB series) and string wound (Delta Pure Filtration DW Series) filters with polypropylene media are commonly employed.
For organic chemical contaminants and chlorine, carbon filtration is often employed. Two carbon filter formats are the “extruded carbon block” and rolled “carbon paper.” Delta Pure Filtration also offers “combination filters” with a sediment pre-filtration section followed by a carbon filtration section.
Delta Pure Filtration employs coconut carbon in its filters. Coconut carbon is regarded as zero-sulfur containing, as opposed to coal-based carbon which can contain sulfur. Sulfur would be a contaminant in plating solutions because the chemistry of the plating solution must be carefully controlled to assure effective plating, and because sulfur can accelerate corrosion.
Delta Pure Filtration supplies carbon filters for a variety of applications, including drinking water, and not every filter will be automatically appropriate for every plating chemical. It is also helpful to understand that there are two “end of life” phenomena with a carbon filter: saturation, and blinding (or plugging). A filter that is saturated won’t remove any more molecular contaminants such as organics or chlorine, but may still allow adequate flow. A filter that is plugged with particles will choke off flow. To “get the best of both worlds” in one filter, one might consider a 4.5” diameter “J series” DCB filter, which has a full 2.5” diameter carbon block, with a sediment pre-filtration section upstream!
The plating operation generally employs filters in a recirculating arrangement. Fluid from a bath is pumped through the filter and returned to the plating, etching or cleaning solution tank. Flow rate has a big impact on how well the bath is “cleaned up.” Understandably, filter users will pay attention to the filter rating or particle removal efficiency of a filter, but this is only one part of the puzzle.
A high recirculation rate can be even more valuable in keeping a plating solution clean than a slight improvement in filter efficiency, because each successive pass of the fluid through the filter will make the plating solution cleaner. For that reason, the “tightest possible filter” may not be the best choice. The filter user will also consider the size of the pump (to achieve a sufficient recirculation rate), the size of the filters used (to extend filter life and reduce resistance to flow), and the arrangement of suction and return of the solution (to assure adequate mixing.)
|CCB – Coconut Carbon Block||-Best molecular contaminant (such as organics and chlorine) removal-Longest life to saturation||-Higher price point-Higher pressure drop|
-Ideally, will be protected by pre-filtration
– J series (4.5” diameter) contains more carbon and will remove more organics or chlorine than a standard 2.5” diameter filter of the same height.
|DWCC –Coconut Carbon Impregnated Cellulose||-Good flow rate/low pressure drop-good life to plugging|
– great price
|– Contains cellulose which is not compatible with all chemicals in the plating operation. (Many platers will look for a “cellulose free” filter.)- less adsorption capacity than a carbon block|
|DWCF – Coconut Carbon Shell Impregnated Polyester||-Good flow rate/low pressure drop-good life to plugging|
|– Contains polyester – verify compatibility with the chemical of interest. (Polyester is not very acid resistant, for example.)- less adsorption capacity than a carbon block|
|CN04 – Coconut carbon impregnated cellulose with string wound pre-filtration section||-Long life to plugging||-contains cellulose-see comments for DWCC|
|CN04CF – coconut carbon impregnated polyester with string wound filter (pre-filtration section)||-Long life to plugging||-contains polyester-see comments for DWCF|
|DCB-coconut carbon block with string wound filter (pre-filtration section)||-long life to plugging-great life to saturation||– a wide variety of pre-filter materials are available.- J series (4.5” diameter) DCB cartridges use a 2.5” diameter carbon block|
-Standard (2.5” diameter) DCB cartridges use a narrower carbon block
* A sediment filter may be installed downstream of a carbon filter to collect carbon fines.