Nickel Electroforming

Description

Nickel and nickel alloy electroforming processes are used for the fabrication of a variety of components. A typical example is the manufacturing of large size moulds (e.g. for injection moulding of dashboards) and dies (e.g. for steel sheet shaping) of complex geometry. Also some parts in the automotive and aerospace industry are made through electroforming processes, e.g. the leading edge rotors for helicopter blades, reflectors, etc. Finally a wide variety of mini- and micro-sized components for watches, hearing aids and other precision instruments is produced by means of electroforming on flat carriers as plates or wafers.

The throwing power of nickel and nickel alloy plating baths in general is very poor, while on the other hand the layer thickness specifications for electroformed objects are often very tight. Even at very low electroforming rates (current density values below 100 A/m2 or 10 ASF) this often leads to high scrap rates for mini- and micro-sized components. For large size objects intensive reworking (grinding) may be required, not only after the total process time, but even during process interruptions.

Elsyca's Advanced Engineering Services (AES) will mainly focus on an improved cell design for the reduction of the scrap rate for electroforming of mini- and micro-sized components, or on the design of an advanced tooling system that eliminates such reworking during process interruptions for large size moulds or dies.

A typical fully developed and optimized tooling system for a dashboard mould involves dozens of auxiliary anodes and shields or current robbers.

Elsyca's Solutions

Nickel electroforming processes are common spread and the applications range from mini-sized objects (mm scale) to large size objects (several foot or even meters long). Depending on the demands of the electroformed object in terms of hardness, wear resistance and corrosion resistance, or even magnetic properties, instead of pure nickel a nickel alloy will be deposited, for example nickel phosphor, nickel iron or nickel cobalt. Even tertiary alloys might be required (e.g. nickel iron cobalt)

The throwing power of nickel and nickel alloy plating baths (often Watts type or sulphamate based) in general is very poor, which makes it very challenging to meet minimal and maximal layer thickness specifications. Often this problem is circumvented for mini- and micro-sized components by allowing for a large scrap fraction, combined to a very low process speed. For large size objects the problem is also tackled by working at a very low process speed, while the work piece to be electroformed is intensively reworked (grinded) during several process interruptions. Total process times ranging from several days to several weeks are no exception.

For nickel alloy electroforming applications the workable current density window will even further narrow down since the allowable alloy content in the nickel is often restricted between tight limits in order to preserve the right properties of the electroformed material. This inherently means that drastically reducing the process speed (thereby giving in on production capacity) is not an option any more, since it will bring the deposited alloy out of specifications with respect to the alloying element(s) composition.

Elsyca's Advanced Engineering Services (AES) offer different solutions for nickel and nickel alloy electroforming applications.

Electrolyte characterization services allow gathering all relevant electrochemical properties from a given bath sample as supplied by the customer. Laboratory experiments are executed to measure critical plating bath characteristics, such as conductivity, anodic / cathodic polarization, cathodic plating efficiency and plating alloy composition. The data collected from the plating bath characterization are used as input for the Elsyca PlatingMaster simulations, ensuring an improved accuracy of the simulation results. On its own, the electrolyte characterization already provides valuable insight in the bath characteristics, such as the allowable operating window (current density, temperature, etc.) for achieving a specified deposit quality and alloy composition.

For large size parts to be electroformed, a plateability analysis based on the CAD of the mandrel is a very fast analysis that will reveal the deposit thickness distribution that could be achieved by only using the main tank anode baskets. In turn, these results provide a first indication to the electroforming shop on the amount and complexity of tooling and reworking efforts that will be required for electroforming this part within thickness specifications.

Both for large size parts and mini- and micro-sized components on a carrier (panel or wafer) a diagnostic of expected process performance can be quickly achieved with a Plating Feasibility Analysis where the electroforming performance is simulated for the existing or foreseen plating tank, thereby including the existing or foreseen tooling configuration (shield, conforming anodes and current robbers). These valuable data can be use internally for further process improvement or for marketing purposes to demonstrate the plating performance to an end-customer.

A Computer Aided Engineering (CAE) project for the electroforming process of mini- and micro-sized components might involve the design and optimization of tooling components (integrated configurations of auxiliary cathodes, current robbers and shields) for an existing plating tank, or the design of entirely new electroforming cells and concepts for high-end applications. A CAE project possibly also involves the optimization of the lay-out of the components on the carrier, including the definition of on-board current robber structures and / or current robber background grids on the carrier.

A Computer Aided Engineering (CAE) project for a large size part will often involve the design and combination of a complete tooling configuration that enables electroforming the part within thickness specifications without any process interruptions. The tooling configuration might involve a huge collection of conforming anodes (often of soluble type), shields and current robbers. The total number of tooling components for electroforming a single mandrel might get larger than 100, and the conforming anodes will often be steered by a multitude of auxiliary rectifiers.

Simulations are based on in-house developed software platforms, in casu Elsyca PlatingMaster for the current density and layer thickness distribution simulations.

For projects that involve the CAE of an optimised tooling configuration, Elsyca can also deliver the CAD of the entire Tooling and Fixture system, including technical drawings and Bill of Materials.

Some examples

A typical fully developed and optimized tooling system for a dashboard mould involves dozens of auxiliary anodes and shields or current robbers. An example can be found here.

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