Electromagnetic interference (EMI) can cause damage to delicate electronic components. Smartphones, computers, aircraft, biomedical technologies and dozens of other devices rely on electronics to function. To keep these devices up and running, adding EMI shielding products is a must. EMI shields come in several varieties and materials, each suitable for a specific application. Here is a quick list of some of the most commonly used EMI shields and how they are used.
Building EMI Shielding Products
When creating miniature "faraday cages" for use in electronic devices, a couple of issues arise. Materials used must be either magnetic or conductive, and solid or mesh, depending on frequencies that need blocking. For full range shielding, it can be tough to build in miniature. The following materials are some of the most commonly used because they block a wide range of signals and offer flexibility of design.
1. Pre-Tin Plated Steel for Low to Mid-Range Blocking
Pre-tinned steel parts are commonly used in many electronic items because it works well to block low frequencies and the tin plating makes the steel more versatile. Tin is solderable, so it can be installed easily in a number of devices, and the steel under the plating adds the magnetic component needed for blocking frequencies of less than 100 MHz.
2. 770 or Nickel Silver
Not all applications need magnetic components. In fact, some biomedical devices like MRI machines won't function with those parts, but they still need EMI shielding products. For these uses, an alloy of copper, nickel and zinc works well to block mid and high range frequencies. Because all of the materials used are naturally corrosion resistant and solderable, no plating is needed.
Pure copper shielding is one of the most useful and expensive options when building shielding. It works with both magnetic and electrical waves, making it useful in everything from computer parts to biomedical devices. For use in batteries or other contact applications, phosphorous bronze or beryllium copper are often the material of choice due to the increase in elasticity.
When fabrication is handled by the manufacturer, aluminum can be a good choice for many shielding applications. It doesn't rust, is highly conductive and offers a strength-to-weight ratio near the top of the chart. One of the challenges of working with aluminum is the simple fact that it does not solder well, making it difficult to install in tight areas.