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ISO 9001:2008 - AS9100:2009 REV C CERTIFICATION

EMI/RFI Shielding

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Finger Stock Gaskets

Finger Stock Gaskets General Information

ROHS

Tech-Etch offers the most complete line of standard EMI shielding strips in the industry. These RoHS compliant shielding strips are designed for a wide variety of application requirements. They are available in strips ranging from 16 to 24 inches in length, in continuous coils up to 35 feet long, as single fingers, or cut to requested full-finger lengths. Consult our engineering department for special modifications to suit your requirements.

Uncompressed heights of standard finger stock range from .03" to .44", which will occupy gaps as low as .01". Many gaskets are offered in two material thicknesses to meet diverse application compression requirements: "Standard" and "TF", which requires less force to compress the gasket to its operating range.

Finger Stock Profiles
Beryllium Copper EMI Shielding Products

  • Finger Stock
  • "D" Connector Gaskets
  • Contact Rings

Stainless Steel EMI Shielding Products

  • Finger Stock
  • "D" Connector Gaskets
  • Expansion Slot

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.

Beryllium Copper EMI Shielding Performance
 H-Field - 100kHz  E-Field - 10MHz  P-Field - 1GHz
 >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
Aluminum
Cadmium Plating
Brass
Magnesium Alloys
Aluminum Alloys Carbon Steel Stainless Steel
Aluminum Zinc & Zinc Plating Iron Beryllium Copper
Aluminum Alloys Chromium Plating Nickel & Nickel Plating Copper & Copper Alloys
Zinc & Zinc Plating Cadmium Plating Tin & Tin Plating Nickel/Copper Alloys
Chromium Plating Carbon Steel Tin/Lead Solder Monel
Iron Brass Silver
Nickel & Nickel Plating Stainless Steel
Tin & Tin Plating Beryllium Copper
Tin/Lead Solder Copper & Copper Alloys
Nickel/Copper Alloys
Monel

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.
• At the maximum gap the gasket should be compressed approximately 25%.
• Gaskets may be compressed to 50% of their height or more.

Gaps
Compression
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