APPLICATIONS
Electroforming
Electroforming is the critical process that converts the soft organic photoresist pattern into a hard, durable metal tool capable of withstanding the pressures and temperatures of high-volume production. This process creates a nickel shim, an exact negative replica of the original micro-structured surface, which will serve as the embossing die for mass production.
From PET Master to Nickel Shim
The electroforming process is an electrochemical deposition technique. Before placing the recombined PET master into the electroforming tank, the surface must first be made electrically conductive. This is achieved by applying a thin silver coating to the PET surface through either chemical silvering or vacuum sputtering. The silver layer provides the conductive surface necessary for electrodeposition.
The silver-coated PET master is then immersed in an electroforming tank containing a nickel sulfamate electrolyte solution. A nickel anode is placed in the solution, and a controlled direct current is passed between the anode and the conductive PET master (which serves as the cathode). Nickel ions migrate from the anode through the electrolyte and deposit onto the conductive silver layer, gradually building up a solid nickel shell that conforms exactly to the micro-structured surface topography.
The electroforming process requires precise control of multiple parameters: bath temperature (typically maintained within a narrow range around 50 degrees Celsius), current density, pH level, and deposition time. Typical deposition cycles range from 90 minutes to several hours depending on the desired nickel thickness. The result is a mother nickel master origination shim (also called the master shim), which is an exact negative of the original photoresist pattern.
From this mother master, multiple working shims (daughter shims) can be produced through additional electroforming cycles. The mother shim is placed back into a hard electroforming tank, and the process is repeated to create additional nickel copies. These daughter shims are slightly harder than the mother shim and are the actual tools used in the embossing machines. A single mother shim can produce numerous daughter shims, each capable of embossing thousands of meters of holographic film before wear necessitates replacement.
After electroforming, the nickel shim is carefully separated from the PET substrate, thoroughly cleaned to remove any residual photoresist or silver coating, and inspected for surface quality. The finished shim carries micro-structures with dimensional accuracy measured in sub-micron tolerances, ensuring faithful reproduction of the original optical design.
