Custom Designed EMI Shielding

• Tech-Etch supplies many custom designed shielding components for special applications from high volume requirements using progressive dies, to prototype and small quantities utilizing photoetch fabrication. Call for information.

EMI Shielding Performance
Material	H-Field - 100kHz	E-Field - 10MHz	P-Field - 1GHz
BeCu	>110 dB	>110 dB	<110 dB
Note: Plating the mating surfaces with the same material will provide superior performance. Chromate chemical film on aluminum maintains surface conductivity by reducing corrosion.

EMI Shielding Compatibility

Electromagnetic Compatibility
EMI/RFI Shielding Products are designed to either keep out or keep in electromagnetic interference. Shielding reflects and absorbs incident radiation. The higher the attenuation of the shielding, the more effective it is at keeping in or out the undesired electromagnetic interference.

Electrochemical Compatibility
To avoid galvanic action between contacting metals refer to this chart. Materials in adjacent groups may be safely used together. Choosing materials from within a single group in the table will provide the least corrosion due to galvanic action when the materials are in contact for an extended period of time with appropriate protective finish.

Grouping of Metals by Decreasing Galvanic Activity
Group 1	Group 2	Group 3	Group 4
Magnesium Magnesium Alloys Aluminum Aluminum Alloys Zinc & Zinc Plating Chromium Plating	Aluminum Aluminum Alloys Zinc & Zinc Plating Chromium Plating Cadmium Plating Carbon Steel Iron Nickel & Nickel Plating Tin & Tin Plating Tin/Lead Solder	Cadmium Plating Carbon Steel Iron Nickel & Nickel Plating Tin & Tin Plating Tin/Lead Solder Brass Stainless Steel Beryllium Copper Copper & Copper Alloys Nickel/Copper Alloys Monel	Brass Stainless Steel Beryllium Copper Copper & Copper Alloys Nickel/Copper Alloys Monel Silver

EMI Shielding Attenuation

For maximum attenuation of a gasketed gap, the contact resistance of the mounting joint and closing joint must be very low and remain so throughout the life of the product. While a gasket may have the potential for very high attenuation under ideal conditions, over time oxidation, corrosion and dirt at the mounting and closing joints may reduce effectiveness. Factors influencing contact resistance over the life of the product are pressure (closing force), plating, and wiping action. Our engineers can help you determine the optimal specifications to ensure sustained attenuation.

Compression

The purpose of shielding is to occupy and thereby shield the gap that exists between two adjoining surfaces. In order to be effective, shielding gaskets must be able to occupy both the maximum and minimum gaps, which exist due to fabrication tolerances, misalignment of surfaces, or irregular surfaces. Proper compression management is essential to ensure effective EMI shielding. Tech-Etch will be pleased to assist you in specifying the most effective gasket for your requirements. Compression data provided is for reference only.