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IMPROVEMENT IN THE CONTROL AND ATTAINMENT OF HIGH SPEED ELECTRODEPOSITION PROCESSES

Objective

THE PROJECT IS CONCERNED WITH NOVEL METHODS OF INCREASING THE ELECTRODEPOSITION RATES OF METALS WHILST ACHIEVING AT LEAST EQUIVALENT PROPERTIES COMPARED WITH THOSE OBTAINED FROM CONVENTIONAL TECHNIQUES.BOTH THEORETICAL AND EXPERIMENTALK APPROACHES WILL BE EMPLOYED.THE THEORETICAL ASPECT WILL ENABLE A FULLER UNDERSTANDING OF THE PROCESSES THAT CONTROL HIGH SPEED DEPOSITION (I.E. CELL DESIGN HYDRODYNAMICS AND DIFFUSION LIMITING PROCESSES).DIFFERENT CELL DESIGNS WILL BE ADOPTED AND MODIFIED AS NECESSARY TO ACHIEVE OPTIMUM PLATING CONDITIONS.USED CURRENTS WILL THEN BE SUPERIMPOSED TO FURTHER INCREASE THE LIMITING CURRENT DENSITIES.THE FULLY OPTIMIZED PROCESSES WILL BE EXTENTED TO PILOT SCALE,AND THEIR EFFICACY TESTED FOR BOTH ELECTROCOATING OF STEEL STRIPS AND THE SELECTIVE DEPOSITION OF PRECIOUS METALS ONTO ELECTRICAL CONTACTS.FROM THIS WORK IT IS ANTICIPATED THAT NOVEL PROCESSES CAN BE OFFERED OF SPECIAL USE TO THE ELECTRICAL AND STEEL INDUSTRIES.

The research concerned improving existing, and developing new, high speed electrodeposition processes. The approach is multidisciplinary and is centred around 2 industrial applications:
the electrocoating of steel strip involving the (high current densities process (HCD);
the electrodeposition of precious metals for applications in the electronics industry involving high speed selective jet electrodeposition (HSSJE).

Laboratory devices have been successfully constructed and used to simulate industrial high speed electroplating processes and a full understanding of the factors that control the deposit quality has been attained for different processes. This had led to the development of morphological diagrams.
Zinc electrodeposits with smaller grain size have been produced with the addition of jetted flow to rotational agitation, as well as under certain pulse conditions. Pulse plated zinc samples with improved corrosion resistant characteristics have been obtained. Multilayered high speed zinc coatings were also produced.

Zinc nickel electrodeposits with a nickel percentage ranging between 6 and 40% could be obtained by varying the pulse parameters and agitation level. Multilayer zinc nickel samples formed by different compositional layers were produced. They showed an improvement in the corrosion resistance in terms of first appearance of red rust 60 hs um{-1}.

The HSSD of gold, gold nickel alloy and tin has been successfully developed. Deposition can be achieved at high rates, producing high quality deposits reproducibly and with good selectivity.
Potential applications include:
direct writing of printed circuit boards;
direct writing of microwave circuit boards;
decorative applications such as personalisation of jewellery;
selective gold plating of electrical connectors;
selective tin plating of components to provide solderable regions.
FOR INITIAL TRIALS SOME TEST FACILITIES WERE PROJECTED AND BUILT.DEVICE SETTING IS IN PROGRESS.THEY INCLUDE:
-A RCE HIGH ROTATION SPEED AND FLUID TANGENTAL FLOW TO OBTAIN HIGH TURBULENCE CONDITIONS(RE500.000) EQUIPPED WITH A COMPLETED ELECTRONIC UNIT TO APPLY AND CONTROL HIGH CURRENT DENSITIES UP TO 500 A/DM2,A PUMP AND A THERMOSTATIC UNIT UP TO 80 CELSIUS DEGREES;
-ASINGLE JET UNIT CAPABLE OF DEPOSITING EITHER SPOTS OR BY SIMPLE MECHANICAL MOVEMENT,THIN TRACKS;
-NEW RCE TEST CELLS WITH ADDITIONAL JET OR PULSE FACILITY,DESIGNED TO INCORPORATE SPORT JETS ON SMALL CYLINDERS AND KNIFE-EDGE JETS ON LONG CYLINDERS;-AN ASSEMBLY/CONTROL EQUIPMENT TO ESTABLISH THAT CYLINDER ROTATION REMAINS MASS TRANSFER CONTROLLING IN THE PRESENCE OF VARIOUS JET CONFIGURATIONS.

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Coordinator

MATERIALS RESEARCH CENTRE
EU contribution
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Address
Via di Castel Romano 100/102
00128 ROMA
Italy

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