Shielded enclosures are designed to nullify external magnetic and acoustic interferences that may impede the function of the circuit. Sometimes a particular component in a circuit can trigger internal disturbance which, in turn, can hinder the workings of other elements in the circuit. To block crosstalk among circuit components, a shielded enclosure is fabricated over a PCB. This technique helps enclose disturbing agents. To build a long-lasting enclosure, hard metals like aluminum, steel, and galvanized steel are preferred, as these metals can withstand strong physical force from the outside. However, soft metals such as copper are also used as they are highly conductive and can effectively block any interfering crosstalk across the circuit. To understand the intricacies of a shielded enclosure, we should take a close look at these three metals. The more we know about the shielding properties of these three metals, the better we will be able to design a protective housing.
Copper and brass (a copper alloy] are one of the most versatile metals used for shielding. As copper is a soft metal, it can be given any specific kind of shape according to the requirement. Incorporating a copper enclosure into a circuit board is easy; a simple soldering can help fix a copper enclosure over a PCB. Copper is highly conductive and doesn’t oxidize readily when exposed to natural elements. Therefore, copper makes an ideal solution where the designer is looking to build a strong, long-lasting application. A softer conductive metal like copper is also a good choice for better field modification. However, because of its softness, copper is not an ideal choice when it comes to building bigger enclosures. Sometimes, designers use thick copper sheets for larger housing, which guarantees high performance and protection.
There is one thing, developers need to keep in mind that copper is cathodic concerning the other metals in the galvanic chart. So, before coupling with any other metal, developers must take great care to minimize galvanic corrosion in the other metal. For this reason, the surface of the second metal in contact with copper should be treated properly before coupling. The reduction of galvanic corrosion in this way is necessary for better enclosure strength.
Aluminum is the second most commonly used RF shielding material. Aluminum sheets are of a heavier gauge than their copper counterparts are, and can, therefore, build a sturdy enclosure. Aluminum’s non-ferrous properties and higher strength to weight ratio make it an appealing choice among designers. Aluminum’s bare metal surface gets readily oxidized in air, but this doesn’t create any problem for the circuitry, as the oxidation process stops after a certain point. Sometimes the bare surface of aluminum is coated with protective material, and it comes handy when the enclosure may have a chance to get in contact with strong chemical solutions.
Steel is ferromagnetic, and in its various forms, it can create a very low-frequency magnetic field around it. This low-frequency field can create a protective enclosure when the situation demands. Steel alloys, depending on their carbon content and annealing process can emanate different range of magnetic fields. These counter-fields offer added protection to the circuitry elements. Generally, steel does not form any metal oxide layer in its bare surface. However, the presence of impurities in the steel ore can make some varieties prone to oxidation. To curb this problem, the designers always should use a protective layer over the steel enclosure.
To run smoothly, electrical and electronic products need to be shielded against the external wave interferences. Shielded enclosures help to attenuate external electromagnetic radiations and acoustic interferences. The three kinds of metal we have discussed above are both sturdy and good conductors, which are the reason why they are the prime choices for making shielded enclosures for important machines.