Technology – Plating General

y avoiding aqueous solutions, a fundamental reassessment of all electro-chemical processes is allowed. Issues like, for example, hydrogen evolution, hydroxide chemistry, over potentials, solubility limits, pH levels, current efficiency etc may either be obsolete or need to be completely reconsidered. We have developed ionic liquids, which we have used to plate a variety of metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sn, Pb, Pd, Ag, Pt, Ru and Au) and alloys (Zn/Cr, Cr/Mn, Sn/Cu and Zn/Sn) onto a large selection of substrates, including onto corrosion sensitive metals like aluminium.
Process Benefits Include:
• Substantial energy savings
• Significantly reduced environmental impact
• Reduced effluent treatment required
• Minimised need for air pollution control measures
• Fewer surface defects
• Reduced material use
• Ability to plate onto previously incompatible substrates
We are currently focusing our development work on chromium plating (both decorative and hard chrome) and we are in the process of building a pilot plant.
Electroless Deposition of Silver and Copper
The PCB fabrication technology has gone under drastic changes over the last 20 years. This was mainly due to the limitation of using chlorinated and or fluorinated solvents in the fabrication process. As a result, certain photo polymer resist materials used for conductor imaging and solder masking could no longer being processed. The newer resist that are processed in alkaline solution did not withstand the high pH of the electroless Cu plating bath. Direct electroless plating of conductor lines, as used in additive processing of PCBs, could no longer being performed. The PCB fabrication processes using additive technology stopped because of the lack of suitable materials.
The introduction of Ionic liquids as a new plating technology for electroless or electro plating offered a new opportunity for the re-introduction of additive technology. First results in chromium plating, copper plating of aluminium, electropolishing and electroless silver plating proved functionally of ionic liquids in the field of electro andelectroless plating.
A new process has been developed for the electroless deposition of silver on to a copper substrate. The process is particularly designed for silver plating on multi-track circuit boards. The operating conditions are the same as the existing water based solutions and represent simple drop in technology. The process has the following benefits:
• Thick, bright, adherent silver layers possible
• Reduced light sensitivity of solution
• Decreased soldering temperature
• Uniform deposition rate
• Non-acidic formulation
• Non-cyanide
These benefits are accomplished through a new ionic liquid technology.
A new process has also been developed for the electroless deposition of copper onto aluminium substrates. The process is designed to facilitate electrolytic coatings of other metals onto aluminium components. The operating conditions are very mild and the process is very simple. Thickness of the copper adhesion layer is controlled by exposure time but typically thin, even, adherent, homogeneous films can be deposited in a few minutes. The process has the following benefits:
• Dip coating process
• No catalyst of surface treatment required
• Rapid deposition time
• Simple process operation
• Acid-free
• Low toxicity
This process uses new liquids that are less hazardous to use than established aqueous technologies but are otherwise drop-in replacements. This process has the benefit that electrolytic plating on top of the copper ad-layer is easily accomplished using any other conventional electroplating process. For example good adherent coatings (10 ?m) of Ni were achieved from an aqueous Watts bath on an Al rod plated with electroless Cu from the ionic liquid.


For a full background on metal processing using ionic liquids look at the new book
F. Endres, A. P. Abbott and D. MacFarlane, Electrodeposition from Ionic Liquids, Wiley VCH, Weinheim, 2008
(ISBN: 978-3-527-31565-9)

April 2020
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