Electronic Connector Company’s President, Bernard Gizzi, explains how heat-shrink tubing provides a versatile EMI/RFI shielding solution in industrial, mil/aero and medical apps
Disrupted electromagnetic energy can adversely affect the performance of electronic devices. Referred to as electromagnetic interference (EMI) or radio frequency interference (RFI), this is a growing problem and design challenge. In today’s world of ubiquitous electronic systems, this susceptibility can affect performance in two ways: conducted EMI/RFI which causes systems to malfunction from within or radiated EMI/RFI which causes other nearby equipment to malfunction.
If an electronic system needs a cable assembly connection, shielding may be required to mitigate EMI/RFI problems. Common solutions include a metal or metallized plastic connector and soldering the cable shield to the connector or wrapping the junction with copper tape which is soldered to the cable shield. More robust solutions involve metal braided sleeving and tubular expandable braided cable shielding. This is used primarily in the electrical wire interconnect industry to protect cables from electrostatic and electromagnetic interference. These solutions work but are costly and labor-intensive.
A cost-effective solution is shielded conductive heat-shrink tubing with a metallic conductive ink coating on the inside. The inner coating provides electrical continuity and EMI, RFI and ESD shielding around the connected joints.
The appropriate diameter of tubing is placed over the components or assemblies to be shielded. A gun, oven or other heating device applies heat to the tubing. After the tubing shrinks, the inner metallic layer provides an electrical connection between the outside surface of the objects joined by the tubing, creating an almost 100 per cent effective, 360-degree circumferential shield.
The versatility of heat-shrink tubing and its shielding effectiveness have been demonstrated in diverse applications. One military application involves a soldier’s helmet. The new helmet design incorporated night vision, heat sensing and two-way communications into the helmet. When the helmet was manufactured the electronic systems were in proximity and interfering with each other. Crosstalk was so bad it was impossible to use more than one system component at a time.
Using heat-shrink tubing to cover the cables running inside the helmet solved the problem. That simple solution avoided the design and fabrication of custom cable shields or metal enclosures, reducing the helmet’s complexity and weight.
Not all EMI/RFI cable shielding problems can be fixed with a single product like heat-shrink tubing but testing various configurations is a good start.