The proliferation of electronic circuits can be witnessed virtually everywhere from our homes to the industrialized Internet of Things found in factories, transportation, food processing equipment and medical devices. Conductive surfaces, like the wires or metallic enclosures housing these circuits generate unexpected current and electrical energy when exposed to electromagnetic waves coming from a variety of natural and artificial sources. When electromagnetic energy disrupts the expected electrical performance of a device or material it’s called electromagnetic interference (EMI) or radio frequency interference (RFI). In today’s world of sophisticated electronic systems, this susceptibility can affect performance in one of two ways: conducted EMI/RFI which causes the system to malfunction from within, or radiated EMI/RFI, which causes nearby equipment to malfunction.
Cables often need shielding to mitigate EMI or RFI problems. Common solutions include a metal or metallized plastic connector and soldering the cable shield to the connector or, alternatively, wrapping the junction with copper tape and soldering it to the cable shield. More robust solutions involve metal braided sleeving and tubular expandable braided cable shielding which is used primarily in the electrical wire interconnect industry to protect cables from electrostatic and electromagnetic interference. Even though these types of solutions may work, they can be costly and labor-intensive.
A cost-effective solution to this problem is shielded conductive heat-shrink tubing with a metallic conductive ink coating on the inside of the tube. The inner coating provides electrical continuity and EMI, RFI and ESD shielding around the joints being connected. This tubing can solve a number of EMI/RFI problems easily and inexpensively.
In use, the appropriate diameter of tubing is placed over the components or assemblies to be shielded, and heat from a heat gun, oven or other conventional heating device is applied to the tubing. After the tubing shrinks, the inner metallic layer provides an electrical connection between the outside surface of the objects that are joined by the tubing, thereby creating an almost 100 per cent effective, 360 deg circumferential shield.
The versatility of heat-shrink tubing and its shielding effectiveness have been demonstrated in diverse applications. One military application is in a soldier’s high-tech helmet. The manufacturer had developed a new design incorporating advanced systems such as night vision, heat sensing and two-way communications. However, when the helmet was manufactured the various electronic systems were in proximity and were interfering with each other. Resulting crosstalk was so bad it was virtually impossible to use more than one system component at a time.
Using heat-shrink tubing to cover the cables running inside the helmet easily solved the crosstalk problem. That simple solution avoided the design and fabrication of custom cable shields or metal enclosures, thus reducing the helmet’s complexity and weight. The heat-shrink tubing also withstood the rapid thermal changes experienced where warfighters need to work and perform their duties in support of freedom.
In conclusion, shielded heat-shrink tubing offers a cost-effective and easily implemented solution to EMC challenges.