Electromagnetic as well as radio-frequency interference is a major issue for the shielded cable assemblies used in data transmission. The smallest disturbance could result in device failure, a reduction in signal quality, data loss, or a full disruption of the transmission.
What is Foil Shielding?
A shielded cable which uses a thin coating of aluminum or copper and a polyester covering to boost longevity is known as foil shielding. A tinned drain wire made of copper and a foil shield work together to ground that shield.
In addition to providing complete coverage, foil shielding is resistant to different RFI applications of high frequency. Foil shield comes quick, cheap, and simple to create because it is lightweight as well as affordable.
Despite providing coverage and RFI protection, foil shielding is not very robust, and its components are delicate. These characteristics make foil shielding challenging to deal with because it has a short flex life as well as zero mechanical strength. For the high-flex applications, foil shielding is not advised.
Foil shielding can be generally utilized in cables when the maximum amount of cable flexibility isn’t really critical. Understandably, the mechanical qualities of a totally enclosing foil that behaves like such a tube are not as efficient as a spiral and braided shielding. Because a foil shield may even crack under extreme mechanical stress, the engineers also use other shielding types when other factors like flexibility or even drag-chain compatibility have not been taken into account.
In every cable design, foil shielding plays a vital role in minimizing EMI as well as other crosstalk. Two forms of a tin foil: copper foil or aluminum foil can be utilized in data cables that are twisted.
What is the Function of Foil Shields?
The kind of screening or shielding used is a vital component in a cable. The primary function of various shielding techniques is to shield the conductors of the signal from outside interference (electrical or/and magnetic fields), which improves the electromagnetic compatibility of a cable and makes sure that the signal transmission becomes unhindered and interference-free as possible.
Also, the three basic shielding types are braided, spiral, and foil shields. Typically, the foil shield is made of plastic foil which is covered in aluminum just on surface and is bare or uncoated inside (this is also called the aluminum-laminated foil).
Even at tiny bending radii, it typically completely covers all its inner conductors and also provides mechanical stabilization for the cable. It is also feasible to coat with other types of metal, like copper.
If more glue or welding is required, this foil would either be laid or wrapped around this conductor in a longitudinal way and in the direction of movement). The shield wire, which is a thin, non-insulated strand that runs underneath the shield as well as connects it via the connector, is also significant in this situation.
Because they provide the finest electromagnetic field shielding capabilities, foil shields have been frequently utilized in high-frequency regions (this depends on the thickness as well as the applied material). Between 60 to about 65 dB, the foil shields offer a great value for attenuation.
Common Methods for Cable Foil’s Construction
The construction of a cable’s foil typically employs one of three techniques: longitudinal, wrapped, or diagonal.
Longitudinal
The longitudinal construction utilizing either copper or aluminum foil is the simplest and least expensive foil approach. It doesn’t need any extra production processing and gives the finest electrical shield efficacy. Foil can be fairly rigid when used longitudinally, which makes it less useful after movement. Take for instance, the foil might start to break or crack if it is moved too frequently.
Diagonal
Foil should be used in a diagonal approach, which could be used in the process of twisting to increase its flexibility. It doesn’t need any extra production processing, just like longitudinal. Nevertheless, when utilized diagonally, additional shielding foil would be needed than when utilized longitudinally.
This helps in increasing the foil consumption as well as your expenditures. Finally, regarding shielding, the effectiveness of diagonal shielding is less than that of longitudinal shielding.
Wrapping
The most flexible option is to wrap your shield foil, although this option has the least effective shielding. Taping the foil increases production costs as well. There is insufficient shielding between the connector and the cable shield.
Over the foil shielding, some copper is required, either tin or bare copper. There are two ways to include this copper in the cable: either as indirect cores or via copper braiding. Longer braids are more affordable, quick, and simple to strip.
However, they offer low flexibility, reduced attenuation, and short service lives, particularly in mobile applications. On the contrary side, shorter braids are preferable for lengthy service life in applications that move continuously, like cable tracks. Compared to short braids, they provide greater attenuation. However, they cost more up front and stripping them is more difficult.
What is Braided Shielding?
A shielded assembly is enclosed in a densely woven lattice comprising thin wires or tin copper for braided shielding. The braid-like arrangement offers a low-resistance route to the ground.
The most “conventional” type of shielding is braided, which is more adaptable than the foil shielding. This form of shielding is really effective and flexible, providing lots of flex life as well as mechanical strength.
iCONN advises using braided shielding for all EMI applications inside the low to the medium frequency range, despite the fact that it works at all types of frequency and is most effective at low frequencies.
While this foil shielding works great for different applications of high frequency, braided shielding provides strong mechanical strength therefore works best for medium and low frequencies. Foil is less expensive and more readily produced than braided, which may cost more. Braided shielding, the most common type of shielding, only offers 70–90% of coverage whereas foil shielding offers 100%.
Conclusion
Shielding, which is known as an insulation layer that contains electrical energy and is wrapped round electrical cables to stop it from absorbing or emitting EMI/RFI, is a component of shielded cable assembly. Foil shielding is essentially utilized in cables whereby the highest possible flexibility of the cable isn’t too important.
