Electromagnetic interference (EMI) whether on board or device level must be either managed or eliminated. This is because it interferes with the functioning of the PCB or device and may even damage it. Today many EMI shielding techniques are used to mitigate EMI. Although these shielding techniques differ in terms of application and impact, the only requirement most users focus on is their EMC compatibility. A shield must be EMC compatible, which means the device or PCB can function normally in the presence of EMI with the use of EMC shields. Board level shields are a great option to mitigate EMI on the board level. While it is common to use non-conductive materials to prevent EMI, such as rubber or plastic, conductive metals such as stainless steel are also used effectively. But one can get the best output when plastic film and metal are combined to form this shield. This post discusses the use and effectiveness of stainless steel vs. plasticized metal in EMI shields.
What Are Stainless Steel EMI Shields?
These are EMI shields made using stainless steel as the only metal or it may be used with other metal composites, polyester fabrics, or thermoplastics. In general, metals are effective in EMI shielding as they are conductive. They help in grounding, heat dissipation, and prevention of static charge. Stainless steel is widely used alongside copper and aluminum. This is because it is robust and cost effective. Aside from conductivity, stainless steel offers heat and corrosion resistance. The shielding effectiveness of stainless steel ranges from 83 dB and 126 dB. The conductivity of stainless steel is 1.8 × 104 S/cm. However, despite all these characteristics, stainless steel adds its weight to the board.
What Are Plasticized Metal EMI Shields?
This is one of the advancements in the EMI shielding segment. Plastic films such as polyetherimide may be either combined with metals or reinforced on the inner surface. This makes the shields lightweight and enhances the board’s EMC value. Polyetherimide can withstand high temperatures beyond 300 degrees Fahrenheit. It is flame retardant and offers structural stability to the board. This high performance engineering thermoplastic offers decent shielding effectiveness, especially when combined with metals such as stainless steel or tin.
Effectiveness of Plasticized Metal Shields Over Stainless Steel Shields
Plasticized metal shields plated with tin certainly have more benefits compared to metal or stainless steel EMI shields.
- These shields are not only effective in EMI shielding but are lightweight and flexible. On the other hand, metal shields consume a lot of space and add weight.
- They consume less space and can be custom made to the fit any shape and size of the board. They are thermoformed and hence can fit the board well even in case of complex designs, limited clearance between shield surface and components, single or multi-cavity shapes, and more.
- While they fit the board well, these shields are removable. This helps in case you want to rework on the PCB.
- These shields offer better isolation, and resistance to shocks, vibration, heat, moisture, and more.
- These shields find use in mission critical applications such as medical devices, defense systems, avionics, navigation systems, and more.
If you are looking for good quality shields for your new or existing PCBA, it may be wise to consider plasticized metal PCBs rather than only stainless steel ones. Also, ensure you source them from reliable and certified players. XGR Technologies offers SnapShot ™ EMI shields made of a thin polyetherimide film on the interior and tin on the exterior surfaces. This offers better isolation for frequencies from below 1 GHz to 12 GHz. These super lightweight shields are reliable and can be easily removed and reinstalled in case you need to make any changes to the board. The non-conductive interior surface reduces electromagnetic coupling. You can contact the XGR Technologies team today for requirement sharing or any further information you need about EMI shields.
