PVD Protects and Beautifies

Surface Coating Industries (SCI),Toronto, Canada, wanted to penetrate the PVD (physical vapor deposition) world market. Its sister company, Balzers, already owned 70% of the world market for PVD wear coatings. SCI wanted to do the same in the decorative market. This aggressive plan was developed by Robert Langlois, president and CEO of SCI. "We have made a substantial long-term commitment to open decorative coating facilities on a global scale. The first facility is here in Toronto and additional facilities will open in the United States in soon."

Why PVD? It is a durable, cost-effective alternative to traditional plating that offers a wide variety of colors. The process is 100% environmentally friendly and produces finishes with exceptional physical properties. The finished surface is unaffected by the elements and the wear and tear of daily use, including household chemicals. SCI processes door hardware, plumbing fixtures, medical devices and automotive items, among other parts; however, the applications for the technology appear unlimited.

SCI adopted the Leybold DeQoTec in-line batch coater as its core coating equipment because it met SCI's demands for a fully automated production system with excellent process control; high reproducibility; high production volume; flexibility in handling different parts and materials; and minimal labor requirements. It allows SCI to provide high quality coatings at competitve prices.

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TABLE I—Quality Test of Zirconium Nitride Coatings
Test Salt Spray (ASTM B117-37) SO2 Spray (DIN 50-018-SWF-2.0S) CASS-Test (DIN 50 021/CuCl + Acetic, pH 3.1 to 3.3) Taber Abraser Vickers Hardness Brillance (CIE lab units/polished brass color) Substrate material Undercoat	Result 800 hours, no surface effect 24 hours, no surface effect 60 hours, no surface effect 1,000 cycles, not worn out 2,000 - 2,000 86 Brass and zinc die cast Ni/Pd-Ni or Ni/Cr, electroplated

 

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Equally important as the PVD process is precleaning the parts prior to coating. SCI cleans all parts entering the facility; customers need not bother. Because of this, SCI needed to develop a comprehensive, highly advanced cleaning system. Through its parent company's long association with ABW, a Swiss-based company, an ultrasonic system was developed. The system is proprietary to SCI.

The dual-cathode arrangement allows operators to run the sputter-ion-plating process simply and reliably. A gas discharge created between a pair of opposing magnetron cathodes generates a plasma concentrated around negatively biased parts to be coated. Simultaneously, the sputtering process acts on the cathodes, removing target material that is distributed around the substrates, condensing on the substrates under constant ion bombardment. The composition of the coating can be changed by the flow of reactive gas up to stoichiometry.¹ The results are uniformly distributed coatings having properties that remain constant over the full surface of the coated substrates.

¹stoichiometry—Chemistry dealing with the quantitative relationships of chemical elements and compounds, and the methods of calculating these relationships.

The ultrasonic cleaning could very well be the largest and most technologically sophisticated in the world. It handles plastics, zinc, steel, brass, nylon and other substrates. The process begins with a 15-stage ultrasonic bath using a variety of proprietary cleaning agents. Completing the wet baths, the parts pass through a turbulent dryer and then through a heat tunnel for drying. Once parts have passed through this rigorous cleaning process they are ready to enter the coater.

SCI's Toronto facility has two PVD coating systems with cycle times of six minutes. These fast-cycle, in-line systems have individual process chambers arranged in a cluster of four process modules around a cubic central chamber. A step-by-step transfer device moves the loaded substrate holders from chamber to chamber while maintaining a vacuum.

In automatic mode, the coating technician calls up a specific recipe for a customer's particular part. The recipe contains color specifications, which determine process parameters, temperature and gas compositions.

The process takes place inside the vacuum chamber where plasma vapor, which is the reactive gases of nitrogen and argon, or others dependent on the color to be achieved, combines with ceramic materials and condenses on the substrates in a uniform and controllable manner. The layers vary in thickness from 0.15 to 0.5 µm, forming films with high hardness and high abrasion and chemical resistance. SCI has the ability to deposit a variety of materials, including titanium nitride, titanium carbon nitride, chromium nitride and zirconium nitride on metals and plastics.

By changing the temperature in the chamber and/or the flow of the reactive gases, different colors can be obtained. The same chamber can be used to process different colors, substrates (plastics or metals) and different finishes. The process can also produce films that have varying degrees of color tones and high color uniformity. Using appropriate sputtering sources (magnetron cathodes) allows operators to deposit films of multi-component alloys and chemical compounds without additional effort. This allows for a nearly unlimited variety of materials that SCI can offer its various customers.

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TABLE II—Compact Specifications
Coating Cycle time Transfer time Time load/unload Pylon Cathodes Inst. Sputter power Inst. Bias power Inst. Etching power	ZrNx; 0.3 µm 6-8 min Less than 20 sec between chambers Less than one minute 300 µm × 1,000 µm length 300 kg maximum weight Two magnetron, HLK, 1,350 µm length 120 kW per chamber 15 kW per chamber 15 kW

PVD hard decorative coating applications are virtually unlimited. PVD's durability, varied color options and unmatched finish make it a premier surface protection choice for industry. With SCI's low-cost production system, durable decorative coatings are quite affordable for any manufacturing application.