Reducing EMI with Flex Suppressor Sheets
Our friend at Kemet - James C Lewis, the Technical Marketing Director is looking at how to reduce EMI with Flex Suppressor sheets.
Introduction: Radiated vs. Conducted Emission
When solving electromagnetic suppression issues, there are two approaches. One is to reduce the amount of energy radiated by the system or eliminate it from the conducting path. In cases where a design is complete and modifications can’t be made, damping radiated emissions may be the only option.
A very common example of radiated suppression involve the EMI Cores you find on power or USB cables. These help to reduce relatively low frequency EMI (kilohertz to hundreds of megahertz) typical to these applications. As frequencies of signals increase to the gigahertz range and connections are only found as traces, not wires, the need for a highly responsive material becomes even more important. Flex Suppressors® are ideal for these higher performance applications.
Flex Suppressor Overview
A Flex Suppressor sheet is composed of magnetic powder that is suspended in a flexible polymer material. This magnetic powder is a proprietary mixture made primarily of iron and silicon. The iron flakes are so thin that eddy currents are not able to form on the skin, causing the electromagnetic field to collapse. Because the metallic flakes are separated from each, the overall sheet is non-conductive. This means it can be placed directly on ICs without fear of causing shorts between pins or from nearby metal shields.
Depending on the amount of permeability needed, the material is available in several thicknesses. The thicker the material used, the higher the permeability. There is a non-linear relationship between thickness and permeability. If the thickness is decreased by 50%, the permeability of the material is increased by approximately four times.
Because there are many factors involved in determining the material thickness needed, many customers choose trial and error to find the right amount. It is common to take the 1 mm sheet, measure EMI, and add additional layers if needed. This helps to determine the right thickness for your situation.
An adhesive backing is available to make it easier to attach to an IC, circuit board or enclosure.
Flex Suppressor Series Comparison
Figure 1: Permeability Graph
The graph in Figure 1 shows the inductance (µ`) and magnetic impedance (µ``) of the different types of Flex Suppressor material available. When trying to reduce noise in a certain frequency range, µ`` is the key parameter. The EFG Series has a relatively low permeability below 1 GHz. However, at 3 GHz, it provides the highest amount of suppression. With its peak around 3 GHz, the EFG is ideal for applications that need to desensitize components to a nearby WiFi and Bluetooth radio.
If your application requires the Flex Suppressor to be attached before the board goes through the reflow oven, consider the EFH Series. It can withstand reflow temperatures, but has mid-range noise suppression compared to the other series.
The EFF Series is the highest permeability material available and represents the latest developments in the Flex Suppressor product line.
All Flex Suppressor sheets available from KEMET are halogen and lead free.
|Part Number||Type||Fixing Method||Thickness||Article no|
|EFA(003)-240X240T0800||EFA - Flame Retardant & Red Phosphorous Free||Self-Adhesive||0.03mm||811-9149|
|EFA(005)-240X240T0800||EFA - Flame Retardant & Red Phosphorous Free||Self-Adhesive||0.05mm||811-9143|
|EFA(01)-240X240T0800||EFA - Flame Retardant & Red Phosphorous Free||Self-Adhesive||0.1mm||811-9152|
|EFA(02)-240X240T0800||EFA - Flame Retardant & Red Phosphorous Free||Self-Adhesive||0.2mm||811-9159|
|EFA(03)-240X240T0800||EFA - Flame Retardant & Red Phosphorous Free||Self-Adhesive||0.3mm||811-9161|
|EFF(007)-240X240T0800||EFF - Extra High Magnetic Permeability||Self-Adhesive||0.07mm||811-9165|
|EFF(01)-240X240T0800||EFF - Extra High Magnetic Permeability||Self-Adhesive||0.1mm||811-9174|
|EFF(02)-240X240T0800||EFF - Extra High Magnetic Permeability||Self-Adhesive||0.2mm||811-9171|
|EFF(03)-240X240T0800||EFF - Extra High Magnetic Permeability||Self-Adhesive||0.3mm||811-9183|
|EFG(005)-240X240T0800||EFG - High Frequency||Self-Adhesive||0.05mm||811-9187|
|EFG(01)-240X240T0800||EFG - High Frequency||Self-Adhesive||0.1mm||811-9196|
|EFG(02)-240X240T0800||EFG - High Frequency||Self-Adhesive||0.2mm||811-9193|
|EFG(03)-240X240T0800||EFG - High Frequency||Self-Adhesive||0.3mm||811-9206|
|EFH(005)-240x240T2200||EFH - High Temperature||Self-Adhesive||0.05mm||811-9200|
|EFH(01)-240x240T2200||EFH - High Temperature||Self-Adhesive||0.1mm||811-9219|
|EFR(005)-240X240T0800||EFR - Standard Specification||Self-Adhesive||0.05mm||811-9212|
|EFR(01)-240X240T0800||EFR - Standard Specification||Self-Adhesive||0.1mm||811-9216|
|EFR(02)-240X240T0800||EFR - Standard Specification||Self-Adhesive||0.2mm||811-9228|
|EFR(03)-240X240T0800||EFR - Standard Specification||Self-Adhesive||0.3mm||811-9231|
|EFR(05)-240X240T1500||EFR - Standard Specification||Self-Adhesive||0.5mm||811-9238|
|EFR(10)-240X240T1500||EFR - Standard Specification||Self-Adhesive||1mm||811-9240|
|EFX(005)-240X240T0800||EFX - High Magnetic Permeability||Self-Adhesive||0.05mm||811-9244|
|EFX(01)-240X240T0800||EFX - High Magnetic Permeability||Self-Adhesive||0.1mm||811-9253|
|EFX(02)-240X240T0800||EFX - High Magnetic Permeability||Self-Adhesive||0.2mm||811-9250|
|EFX(03)-240X240T0800||EFX - High Magnetic Permeability||Self-Adhesive||0.3mm||811-9262|
|EFX(05)-240X240T1500||EFX - High Magnetic Permeability||Self-Adhesive||0.5mm||811-9275|
|EFA(02)-240X240||EFA - Flame Retardant & Red Phosphorous Free||Tape||0.2mm||811-9155|
|EFA(03)-240X240||EFA - Flame Retardant & Red Phosphorous Free||Tape||0.3mm||811-9168|
|EFF(02)-240X240||EFF - Extra High Magnetic Permeability||Tape||0.2mm||811-9177|
|EFF(03)-240X240||EFF - Extra High Magnetic Permeability||Tape||0.3mm||811-9180|
|EFG(02)-240X240||EFG - High Frequency||Tape||0.2mm||811-9199|
|EFG(03)-240X240||EFG - High Frequency||Tape||0.3mm||811-9203|
|EFR(02)-240X240||EFR - Standard Specification||Tape||0.2mm||811-9225|
|EFR(03)-240X240||EFR - Standard Specification||Tape||0.3mm||811-9222|
|EFR(05)-240X240||EFR - Standard Specification||Tape||0.5mm||811-9234|
|EFR(10)-240X240||EFR - Standard Specification||Tape||1mm||811-9247|
|EFX(02)-240X240||EFX - High Magnetic Permeability||Tape||0.2mm||811-9256|
|EFX(03)-240X240||EFX - High Magnetic Permeability||Tape||0.3mm||811-9269|
|EFX(05)-240X240||EFX - High Magnetic Permeability||Tape||0.5mm||811-9266|
Flex Suppressor® is a registered trademark of NEC TOKIN Corporation.