High Speed Low Loss Dielectric Extrusion
In 1933 Ph.D. Mr. Schelkunoff joined Western Electric’s research wing, he began analysis of waveguide propagation discovered analytically.
Breakthrough in Dielectric Technology
Another breakthrough in dielectric technology that we are still benefitting from today happened in the 1953 when Bell Lab’s and Mr. F.B. Lloyd at the Western Electric Company in the US to develop coaxial transmission line foaming and introducing air to extruded polyethylene and thereby lowering the capacitance and insertion loss.
The DuPont® Airquick polymer foam technology comprises nucleating agents and base polymers that improves both the processing and end-use performance.
This new Teflon® fluoropolymer foam resins offers a broad range of wire and cable applications for data communications in multiple applications such as Data Centers, LAN networks, Military and commercial aircrafts.
Benefits of Physical Foam
Physical foam is a more complicated process, but is has benefits that can out way the more complex process necessary to produce product. Physical foam requires a high-pressure gas injection system that is needed to be introducing gas into the melt stream at the gas’s critical velocity that will maximize absorption.
The foam or void content can be increased to 60% depending on materials but typically lower dielectric constants can be obtained with lower dissipation factors then those formed by chemically foamed process.
Skin-Foam-Skin Dielectric technology
Modern communication technologies, whether its data centers or broad band GSM applications, it’s all about creating low insertion loss at reasonable economic product values.
Physical foaming provides exactly the solution to the above challenge, lower insertion loss cables with high value.
In addition, this extrusion technology ensures optimal mechanical performance due to the triple layer Skin-Foam-Skin construction that reduces, if not eliminates all of negative effects of the change of transmission line geometries do to crushing, flexing and or downstream processing in the wire plant itself.
Triple Layer Dielectric Technology
As the transmission speed and the data capacity has increased exponentially in recent years, the operating frequency cable components has equally shifted upward exponentially to higher frequency regions.
Differential transmission lines with lower insertion loss, constant tanδ (Dielectric loss tangent) and low dielectric constant and at the same time economically attractive products have been in high demand.
Vadd’s answer is an in-house developed polyethylene base material enabling “micro” foam structures evenly dispersed throughout the dielectric structure with a minimal addition of nucleating agents.
The Skin-Foam-Skin Nitrogen gas injected dielectric technologies developed by Vadd along with the associated downstream manufacturing equipment and process provides a solution to this well-known and defined problem.
Many of the cable companies in the world of high-speed cables are using solid dielectrics. The manufacturing process and process control for manufacturing Skin-Foam-Skin are extremely challenging and standard off the shelf equipment is nonexistent
Cell Nucleation the Heart of Successful Foaming
Control of cell nucleation is crucial to obtaining the desired fine and uniform cell structure in the final foam structure. It is a complex area with several, often interrelated factors playing a role.
The main factors which influence cell nucleation:
- Higher rates of pressure drop at the die significantly increases the cell density, irrespective of the concentration of blowing agent gas and or external nucleator.
- High shear rates also play a role in promoting cell nucleation.
- It has also been established that higher concentrations of blowing agent and gas lead to increased cell density.
- The addition of external nucleating agents is the most commonly method used to control cell nucleation in the foaming process. Nucleating agents are basically defined as finely divided and dispersed solid particles, which provide sites for cell nucleation.
The gas injection process is a high pressure metering system used in conjunction with a multiple stage screw design that mixes the gas in the correct proportions with the base polymer at the correct melt temperature.
extrusion process needs to be controlled so that when done correctly it forms a high performing dielectric. This means that the resulting foam has a uniform structure which delivers low loss and superior performance.
Vadd extrusion system can predict and control all aspects of creating a high performance dielectric in real-time, with capacitance, diameter and concentricity gauges that interface with control loops that regulate line speed and quench position.
By introducing gas injected voids into FEP or PFA polymeric insulation material the dielectric can be significantly improved. Vadd capability to control the size and distribution of “bubbles” throughout the dielectric avoids any significant degradation of the dielectric performance.
Foaming Dielectrics Significance
Foaming dielectrics offers significant advantages over conventional melt extrusion technologies such as:
- Low Dielectric Constant
- Reduced weight and Size
- Reduced Loss or Attenuation
- Increased Velocity of Propagation
- Low Capacitance and Higher Impedance at reduced dimensions