film capacitors
January 18, 2022

Using Modern Flame Spray Technology to Metallize Capacitors – or Schoopage

Modern flame spray technology is a thermal spray technique used to produce high-performance, uniform coatings on substrates. Flame spray technology involves supplying feedstock to an oxy-fuel flame. The flame melts the feedstock that is atomized by compressed air and is targeted onto the substrate, thus forming a coating. The two most commonly used fuels in flame spray technology are acetylene and propane.

The Requirement for Metallizing Capacitors / Schoopage

Capacitors are a key component for electronic systems that find application in telecommunications, electric vehicle systems, military aircraft, and power trains. Polymeric film capacitors have been fabricated by depositing conductive, thin metallic layers (such as aluminium or zinc), onto thin dielectric substrates (e.g., polyester, polypropylene). The deposited layers act as electrodes of the resulting film capacitors (aka polymer film capacitors). These film capacitors produced via flame spray technology can withstand high voltages, have low ESR, and are non-polarized, making them ideal candidates for microelectronics.

The film is wound to a roll and the edges of the thousands of aluminum layers (connect electrode layers) need to be terminated, or shorted together. This is done by schoopage of a molten metal (zinc, tin or aluminium) on the ends of the roll to form the capacitor polymer film capacitors to form the capacitor element.

Why Flame Spray Technology?

The deposition efficiencies delivered by flame spray technology are higher than arc spraying, e.g., reduced material losses and higher deposition rates. Reduced feedstock loss in flame spray technology eventually reduces coating costs. Compared to arc spraying, flame spray technology offers lower fine particle emissions, thereby reducing the risk of metal fume fever and contamination of the capacitor by particle insertion between the layers.

Flame Spray

Less oxidation of the particles combined with smaller and fully adjustable particle size leads a homogeneous, dense coating with superior electrical and thermal conductivities and, thus, improving the efficiency of the capacitor.

Read More: The Evolution of Flame Spray Technology

Flame spray technology can achieve low heat input with our proprietary cooling system that is crucial to avoid heat build-up and distortions in the metalized film coatings. One of our flame spray technology-based proprietary products is the Master Jet® Auto IV thermal flame spray gun.

Master Jet® Auto IV

Master Jet® Auto IV uses state-of-the-art flame spray technology to deliver superior deposit efficiency with low gas consumption. Master Jet® Auto IV is a cost-effective spray equipment for the production of premium quality schoopage of capacitors, among other applications.

The spray gun has a fully automated system containing a programmable logic controller, touch screen display and mass flowmeter. An electronic motor ensures precise material feed to obtain a uniform coating thickness. The Master Jet® Auto IV gun is mountable on a robotic arm, thus enabling the convenient coating of complex capacitor geometries. The complete process control, including a closed-loop wire feed monitoring offered by the Master Jet Auto IV promises a superior and predictable coating quality comparable to that obtained using arc spraying.

The ergonomic design of the mobile touchscreen enables the user to monitor the coating process effectively. The accurate thermal mass flowmeter controllers ensure the consistency of flame characteristics and particle morphology, which is critical to delivering a reproducible coating quality. In case of abnormal operating conditions (too low-pressure supplies and empty gas tanks), the Master Jet® Auto gun stops automatically, thereby preventing deposition of a poor coating.

Saint-Gobain has a proven track record of manufacturing highly performant, durable, and cost-effective flame spray technology solutions. To find out more about our flame spray solutions, contact us today.