Vacuum requirements for low-E coating
The production of low-emissivity glass depends on vacuum deposition technology. More than 90% of current low-E coatings are silver-based, according to a review of the technology. These thin films are applied in vacuum chambers to achieve the required optical and thermal properties. A 2020 development by Memon et al. involved glass-metal fusion sealing for vacuum glazing, with coating performed on Pilkington K-glass panes at temperatures around 450 °C. The process demands a stable, clean vacuum environment.
Ferrofluid sealing mechanics
Magnetic fluid feedthroughs create a dynamic seal using ferrofluid retained by powerful magnetic fields within the feedthrough body. This design hermetically seals the rings to the shaft. A major benefit is the minimization of stray magnetic fields. The roller-bearing spindle in these units allows for smooth rotation at high speeds, with some capable of up to 5,000 RPM.
Performance specifications from the field
Technical data for hollow axle flanged feedthroughs shows the level of performance needed. Published specifications list an operating vacuum pressure of 10^-6 mbar. The helium leak rate for these components is typically less than 10^-12 mbar·l/sec. They operate within a temperature range of 0 to 80 °C and are suited for use with inert gases. Common construction materials are type 304 stainless steel for the housing and type 420 stainless steel for the shaft.
Advantages for production stability
In high-end vacuum applications like thin-film coating, advanced ferrofluid formulations enable operation in ultra-high vacuum conditions, reportedly up to 1×10^-9 Pa. A significant operational advantage is the absence of outgassing or particle generation from the seal itself. This cleanliness prevents contamination of the delicate silver-based layers being deposited. The hollow axle design also allows for the passage of utilities, like cooling lines or electrical signals, into the vacuum chamber while it rotates.
We manufacture magnetic fluid feedthroughs that meet these technical demands for vacuum processing equipment.