What is

Taping?

Tape insulation and jacketing provide important layers of mechanical and electrical protection for a cable. Choosing the appropriate materials for each can be an important decision.

Mylar Tape - Mylar is characterized by its excellent tensile strength and durability, and is often used as cable insulation. Its ideal operating temperature is 150ºC, for performance without diminished properties.

Aluminum Mylar - This tape consists of aluminum foil, laminated with polyester film. It reflects heat and light, and provides both chemical and flame resistance.

PTFE Tape - PTFE tape is a superb insulator. It offers a wide temperature range, low dissipation, low smoke generation and flame resistance, chemical and moisture resistance, and solvent resistance, but it has poor cold flow resistance. Usually PTFE tape is heat sintered to provide improve abrasion resistance, uniformity, and performance. However, unsintered PTFE tape is often used to reduce loss in high-speed data cables.

Polyester Tape - While this tape is not usually used as primary insulation, it is appropriate for shield isolation and insulation protection. It creates a thermal barrier between the two cable components and its tough material provides the cable with additional mechanical strength.

Kapton Tape - This tape is mechanically tough, increasing abrasion, cut-through, and impact resistance. It also improves the cable’s weather and chemical resistance, although it is susceptible to deterioration from strong bases. It has an impressive operating temperature range of -200ºC to +200ºC. This tape is radiation resistance and will not burn. Kapton Type F also has excellent electrical properties.

TFE Tape - TFE tape can be used as primary insulation. It provides extreme abrasion and abuse resistance, as well as chemical, heat, and moisture resistance. It boasts excellent electrical properties and is rated for use up to 260ºC under mil-spec standards and up to 250ºC according to UL specifications.

Mica Tape - This is a composite tape with a glass scrim backing for mechanical strength. It can be used as primary insulation. It is rated by the UL to 450ºC, but can resist temperatures much higher. It has great moisture and radiation resistance, and can withstand harsh electrical and thermal overloads.

Shielding

Shielding refers to the metallic layer surrounding a cable’s conductor, created to limit signal interference between the wire and external fields. Shielding plays an essential role in maximizing the effectiveness of cable systems.

Shielding is designed to minimize signal leakage and the reception of signals produced by external sources. The electrostatic interference prevented by shielding is also known as noise. An appropriate shield must be chosen in response to which kind of noise a cable will be exposed.

Static Noise - This is distortion caused by an electrical field that has been created by another voltage source and that has coupled into the signal-bearing circuit. Static Noise can be prevented by shielding the full circuit. Foil shields are the most effective in protecting against this type of noise, but must cover both the transmitting and receiving ends of the circuit in order to reduce high levels of interference. The shield must also be grounded to deliver the best results.

Magnetic Noise - Magnetic fields radiated by power wiring used in different mechanical applications cause this type of interference. The magnetic fields can create opposing current flows, disrupting the regular current flow of a wire. Twisting the cable elements is the simplest and most effective way to combat magnetic noise.

Common Mode Noise - Currents flowing from different potential grounds at different points within a system cause this type of interference. Receivers with high common mode rejection ratios can reduce the effects of common mode noise.

Crosstalk - When signals (pulsed DC or standard AC) from one wire are superimposed onto another wire nearby, it is called crosstalk. Individual cable pair shielding coupled to pair twist is the best way to prevent crosstalk, though pair twists alone also reduce this type of interference.

Common Shield Materails

• Bare Copper
• Tinned Copper
• Galvanized Steel
• Stainless Steel
• Aluminum Foil
• Fiberglass
• Kevlar

Armor vs. Shielding

Many times the idea of armor and shielding go hand in hand. Although both are metal layers used in cable to provide protection, each provides a very different kind of protection. Armor, located on the outside of the cable, is a sturdy layer of metal designed to protect mechanical integrity. It defends the cable against physical hazards and prevents it from being crushed or damaged by outside forces. Shielding is incorporated in the inner layers of the cable, around the conductor. It works to minimize electromagnetic interference and prevents the cable from intercepting outside currents or signals that could damage its productivity. Whether armor and shielding are both used in a cable depends on the application for which it is being designed.