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Selecting a CPSA for EMI shielding and grounding
Among various fastening methods for properly shielded and grounded electronic assemblies, conductive pressure sensitive adhesives (CPSAs) are excellent for helping enable design flexibility. Manufacturers like 3M, who have been developing CPSA materials since the 1980s, offer conductive adhesive tapes to multiple industries including for use in electronics applications which continue to evolve.
Conductive tapes provide firm, consistent adhesion and excellent XYZ axis conductivity in a variety of applications. Thin and lightweight, these CPSA tapes can accommodate a greater range of designs vs. screws and other mechanical fasteners, and do not require stress points such as drill holes or rivets. CPSA tape can be used later in the process – which is especially advantageous for applications such as shield can lids or thin touchpads where adding mechanical fasteners could require significant modifications or complete redesigns.
CPSAs consist of particle-filled conductive adhesives that can be combined with foil and fabric backings to help provide the right blend of EMI performance, stability and conformability.
Backings/Carriers
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Conductive fabric
Woven or non-woven fabric carriers are generally chosen for their conformability vs. metal foil backings. Fabrics are also less likely to wrinkle. 3M incorporates metal into the fabric to enhance conductivity.
Foil
Metal foil-backed tapes provide excellent shielding effectiveness.
Both foil- and fabric-backed CPSAs can be coated for applications where aesthetics is important.
Adhesive chemistries
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Acrylic
Acrylic adhesives have a range of advantages for CPSAs. Acrylics used in CPSAs feature fillers for consistent, specific performance characteristics, and bond well to a wide range of substrates while also remaining durable and resistant to challenging environments.
Polyolefin
3M CPSAs with polyolefin adhesive include 3M™ Electrically Conductive Single-Sided Tape 5113SFT and 3M™ Electrically Conductive Double-Sided Tape 5113DFT. They feature a proprietary polyolefin XYZ-axis conductive pressure-sensitive adhesive and a conductive matrix carrier (a nickel/copper/nickel-coated conductive woven carrier). They bond well to a variety of substrates including plastics and metals.
Construction
CPSA tapes are available with adhesive applied to one or both sides of the backing. They are also available ready to apply without the backing as conductive adhesive transfer tapes.
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Single-sided conductive pressure sensitive adhesive tapes
Generally used for applications requiring excellent shielding performance, single-sided tapes are easy to handle, and can be highly conformable – fabric-backed single-sided tapes are bendable across multiple planes without wrinkling or puckering. They bond quickly and deliver high adhesion to a range of substrates. Single-sided CPSAs are excellent for space-constrained areas and are often specified for applications where conductivity is important even with relatively little Z-axis space.
Example applications:
- Display wrapping
- Replacing traditional shield-can lids
- Sensor grounding
- Display CoF
Solutions:
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Double-sided conductive pressure sensitive adhesive tapes
Generally preferred for applications where effective grounding is important, double-sided conductive tapes typically feature thicker constructions than single-sided or adhesive transfer tapes.
Example applications:
- Bond line gap shielding
- Component grounding
Solutions:
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Conductive pressure sensitive adhesive transfer tapes
CPSAs can be used for applications where light weight, extreme flexibility or very low profiles are required. Generally, electrically conductive adhesive transfer tapes are used where mechanical fasteners are too bulky or soldering could be detrimental, such as for assemblies with temperature-sensitive components.
Example applications:
- Sensor grounding
- Connecting medium pitch flex circuits
- Rigid printed PCB
- LCD screens
- Bonding EMI/RFI shield and gaskets to metal frames and enclosures
Solutions:
Learn More
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3M is happy to work with engineers to help them choose the right CPSA for their specific applications. For more information, or to get in touch with a 3M expert, view our Electrically Conductive Tapes for Industrial and Manufacturing.
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