Parker Chomerics CHO-FOIL CCD Shielding Tape is a copper-foil-backed pressure-sensitive adhesive tape in which the adhesive layer is a conductive acrylic formulation. The product is specified for electromagnetic interference shielding, electrical grounding, and electrostatic charge control in cabinet, enclosure, and module applications where a thin conformable conductor must bridge mating metal surfaces. The designation CCD identifies a particular foil–adhesive–liner construction within the wider CHO-FOIL family; the exact foil thickness, adhesive thickness, total tape thickness, roll width, and roll length are controlled by the current Parker Chomerics datasheet and may differ among regional distribution formats. The copper foil is supplied in rolled or electrodeposited form, and the conductive acrylic adhesive is applied to one side of the foil. A release liner is removed before laydown.

Because the adhesive is electrically conductive, the tape does not rely solely on edge contact or mechanical fasteners to create a bond-line ground path. The foil itself provides high bulk conductivity, while the adhesive provides through-thickness conduction. The conductive filler network inside the acrylic matrix reduces the joint resistance between the copper backing and the substrate after pressure application. The result is a shielding tape that can be applied across seams, access panels, connector flanges, and enclosure slots. It is not an environmental seal, and it does not provide structural load-carrying capability.

For purchasing and incoming inspection, the critical parameters include tape width tolerance, roll length, total thickness, surface resistance, through-adhesive resistance, peel adhesion to stainless steel or aluminum, and shielding effectiveness. These properties are not specified by a single universal standard; the supplier may use internal test methods traceable to ASTM D4496, ASTM D3330, and UL 510. Buyers should request the certificate of conformance for each lot.

What makes the conductive acrylic adhesive in CHO-FOIL CCD materially different from a nonconductive adhesive layer?

A nonconductive pressure-sensitive adhesive between copper foil and an aluminum or steel substrate acts as a dielectric spacer. The direct-current resistance between backing and substrate remains high until mechanical pressure punctures the adhesive or until the foil is folded around a bare ground point. In an enclosure seam, that creates a discontinuous ground plane and poor low-frequency shielding. CHO-FOIL CCD uses a percolating conductive filler network inside the acrylic layer. After roller pressure, the adhesive forms a large number of distributed conductive contacts. Published supplier data for conductive acrylic pressure-sensitive adhesive foil tapes commonly report through-adhesive resistance below 1 Ω using a 1 cm² electrode at a defined contact pressure; exact CHO-FOIL CCD values should be confirmed against the current revision because filler type, coating weight, and surface roughness alter the result. The remaining resistance is not zero. For a 25 mm wide tape joint, the total seam resistance includes foil sheet resistance, bond-line resistance, and substrate interface resistance.

Above 100 MHz, capacitive coupling across a thin nonconductive adhesive may mask the deficiency in some test setups, but below 10 MHz the absence of a conductive path becomes measurable as higher transfer impedance. The conductive adhesive in CHO-FOIL CCD therefore changes the low-frequency failure mode from an open adhesive layer to a finite contact resistance that can be modeled as a series resistance in a ground path.

Shielding effectiveness of copper foil with conductive adhesive depends on frequency, seam geometry, and termination quality. Copper skin depth at 1 MHz is approximately 0.066 mm, and at 10 MHz it is approximately 0.021 mm. A foil thickness of 0.035 mm is therefore electrically thin at 1 MHz but exceeds the skin depth at higher frequencies. In the 30 MHz–10 GHz band, a continuous copper foil tape applied over a compressed seam can provide shielding effectiveness above 60 dB when tested in a controlled fixture. Published data for this specific configuration may vary because test aperture size, substrate material, seam overlap width, and contact pressure all influence the result. If the application requires a certified attenuation value, enclosure-level testing under MIL-STD-461 or IEEE 299 should be performed rather than relying on material-level shielding data.

When enclosure seams require RF shielding without increased fastener density

Enclosure seams that are held by fasteners on 50 mm to 75 mm centers can radiate through the gaps between fasteners. The tape is applied across the seam before final assembly to extend the conductive contact length between fasteners and to cover gaps created by sheet-metal tolerance variation. The tape should be oriented so that the copper foil is not stretched, cut to provide at least 3 mm of contact on each side of the seam, and pressed with a 60 Shore A roller or a pneumatic nip at 0.3 MPa to 0.5 MPa. Application below 10 °C reduces tack and may produce incomplete wet-out, especially on textured or oily surfaces. Full adhesive bond strength typically develops over 24 h to 72 h at ambient temperature, although conductive performance appears immediately after pressure is applied. If the tape is applied over a painted surface, the conductive adhesive contacts the paint film, not the base metal; the paint must be removed or masked locally where electrical contact is required.

With automatic tape placement equipment, the roll tension should be kept low enough to avoid yielding the copper foil. Once yielded, the foil may retain curl and peel back from the substrate after thermal cycling. Production lines that laminate conductive foil to flat panel seams with a heated roller should verify that the heat does not accelerate acrylic adhesive flow or create adhesive starvation at the tape edge. For die-cut parts, a kiss-cut operation can cut the foil and adhesive without cutting the liner; grounding of the converting equipment is required to prevent static charge accumulation on the liner.

Surface preparation, galvanic corrosion, and application temperature constraints

Surface cleanliness controls bond-line resistance. Isopropyl alcohol wiping followed by solvent drying removes common oils and light ionic contamination. Abrasive treatment may roughen the surface and improve mechanical keying, but it can also remove conversion coatings that provide galvanic protection. Copper is cathodic to aluminum and magnesium; in the presence of moisture and ionic contamination, the tape edge can act as a galvanic cathode and accelerate substrate corrosion. For aluminum enclosures qualified to ASTM B117 salt spray, chromate or non-chromate conversion coating under the tape may help reduce corrosion, but the conductive bond must still be made to bare or conversion-coated metal, not to paint or anodize. Magnesium substrates present a more severe galvanic mismatch. If the design must survive prolonged salt fog or condensing humidity, a tin-plated copper variant or an isolating conductive gasket may be more appropriate. Published data for this specific configuration is limited when the tape is applied to magnesium, so qualification testing is required.

The acrylic adhesive is stable over a typical operating range but should not be exposed to ketones, esters, or chlorinated solvents in service. Such solvents can swell the adhesive and reduce peel strength. The copper foil can oxidize over time, particularly at elevated humidity. Oxidation of the outer foil surface does not normally eliminate shielding because copper oxides are thin and the bulk conductor remains, but oxidation at the bond line may increase contact resistance if the adhesive loses contact. Storing rolls in sealed polyethylene bags with desiccant at 20 °C to 25 °C and 45–55% RH preserves tack and minimizes oxidation.

Chomerics CHO-FOIL CCD is frequently compared with aluminum foil tape, nonconductive adhesive copper tape, and conductive fabric tape. The following material-class comparison uses published vendor data for typical values; each value should be verified for the specific production lot.

Compared with conductive fabric tapes, CHO-FOIL CCD provides lower sheet resistance and better low-frequency shielding but less conformability. Compared with aluminum foil conductive tape, the copper backing offers higher bulk conductivity and solderability, but the copper-tape edge creates a stronger galvanic cell against aluminum or magnesium. Compared with nonconductive-adhesive copper tape, the conductive adhesive eliminates the requirement for the adhesive to be punctured by pressure or for a separate grounding strap to bridge every seam segment. However, the conductive adhesive is not a replacement for a continuous weld or for a conductive elastomer gasket used in environmental sealing. If soldering is required, the adhesive and liner should be removed from the solder joint area because acrylic decomposes at soldering temperatures and may contaminate the joint.

Electrical bonding safety should be analyzed separately from electromagnetic interference shielding. The thin copper foil and conductive adhesive provide a low-impedance path for small signal and ground-reference currents, but they are not dimensioned for protective earth fault currents. End-product standards such as IEC 62368-1 and IEC 61010-1 require protective bonding conductors to survive specified fault conditions and to maintain a maximum resistance between exposed parts and the protective earth terminal. CHO-FOIL CCD may contribute to grounding at the circuit level, but it does not replace a designated protective conductor unless the complete assembly is evaluated and found compliant under the relevant safety standard.

Batch-to-batch variance in conductive adhesive tapes is primarily observed in peel strength and through-adhesive resistance, not in bulk copper conductivity. Incoming inspection should sample roll width, total thickness, and surface resistance. A four-point probe setup with spring-loaded pins is used for sheet resistance; if pin pressure is too low or the adhesive creates an insulating film on the probe face, readings may be unstable. Peel adhesion to a standard stainless steel panel should be measured after 20 min dwell and again after 24 h to confirm that adhesive wet-out is progressing. For critical applications, retain a control sample from each batch and record application temperature, humidity, roller pressure, and substrate roughness to support traceability.

The tape’s limiting application boundaries include sharp bends, continuous movement, direct liquid immersion, and long-term contact with incompatible plasticizers. When applied to flexible circuits or moving shields, copper foil may fracture after repeated cycles because the metal work-hardens. For static seams, epoxy or acrylic coating can be applied over the tape edge to reduce solvent intrusion and edge lift, but the coating should not contaminate the bond line. If a design requires continuous operation above 105 °C, the adhesive may soften and lose peel strength; the current datasheet should be checked for the maximum continuous service temperature and any UL thermal index.