The rapid growth of the electronic industry together with the extensive use of electronic devices or appliances in telecommunication, defense, medical, automation, and other sectors has led to problems related to electromagnetic interference (EMI), affecting equipment performance. The situation may get worse unless designers take steps to reduce or suppress harmful radiations using EMI shielding material. Though there are many conductive components with the ability to absorb or eliminate EM reflections, selection of the right material is not easy. Here is how you can pick the right EMI shields:
Factors to Consider
The fundamental idea behind choosing the best- material is not just meeting EMI emission standards,-but also ensuring compatibility with a particular device or gadget.
Frequency range and High Current Circuits: The frequency at which the device operates usually is one of the significant aspects of shielding material selection. Emissions increase more rapidly with the increase in device frequency. It explains why high-frequency electronic equipment, devices, or circuits are more susceptible to EMI. Interference also increases directly with the current. Therefore, you should factor in high frequency and high current circuits when opting shielding products.
Shielding effectiveness (SE): SE is a parameter used for determining the extent of protection a shield can give. It is expressed as the ratio between strengths of an EM field at a particular distance from the source, without and with the shield respectively. The efficiency of a shielding material differs from one to the other. However, which one will suit a particular device depends on the interference level. Once can achieve maximum SE by using only copper or ferrite or the combination of both.
Mechanical requirements: There are mechanical factors that affect the selection of materials. The materials surrounding the shield may change the conductivity, which is detrimental to its performance. Physical fit is another factor due to which the SE can change. A well-fitted shield always ensures more safety than a loose-fitting one.
The extent to which an EMI shielding product will suppress emission mainly depend on its size, the kind of material used, thickness, field frequency, and aperture orientation. The same is applicable for installation and mounting too. Shielding materials with apt mechanical requirements will prevent emissions and improve the overall performance of an electronic device or equipment. A poorly installed one is not of much use even if it is made of the best material.
Tolerance to pressure and compression load: Though professionally designed EMI shielding gaskets hardly fail, inappropriate use or incorrect installation will affect compression. If it is under-compressed, it will fail to achieve the required SE. Over compression will also lead to poor shielding efficiency. Besides, you must also factor in force and load considerations when choosing a shielding material. Pick out shielding products based on the metal used, its thickness, the flatness of the mating surface, and fastener spacing. Choose fabric-over-foam material that you can use with low compression, offering outstanding shielding efficiency.
Selection of shielding material depends on the nature of housing used in an appliance too. The devices with plastic housing usually have low tolerance level to the compression load. Calculating the actual pressure created by a shield is of particular importance while searching the material for this equipment. An over-compressed shield can affect the delicate parts whereas the under-compressed one may fail to provide adequate safety. Finding out the best-suited shielding materials for these devices is a challenging task.
Galvanic corrosion: When two different metals are exposed to each other, one of those starts to corrode rapidly, i.e., the metal tries to get a more chemically stable form. This phenomenon is called galvanic corrosion or galvanic coupling. It does not occur if the shielding material possesses similar characteristics as the device metal. Therefore, do not opt for metals with dissimilar features or properties.
EMI shielding materials play a crucial role in reducing unwanted emissions in devices and systems. Today, modern appliances are more vulnerable to interference issues than before. Thus, selection of the right material is more crucial than ever for getting the most from these devices.