Parker Chomerics CHO-FOIL CCJ shielding tape is a tin-plated rolled copper foil coated on one side with a filled acrylic pressure-sensitive conductive adhesive. The product is supplied in roll form on a release liner and is used to close seams, wrap cable-to-connector transitions, and provide ground-plane continuity across joints in metallic and metallized enclosures. The conductive adhesive carries current through the thickness of the bond line, removing the requirement for a low-pressure metal-to-metal contact between the foil and the substrate. Published nominal construction data list a total thickness of 0.089 mm (3.5 mil), composed of approximately 0.036 mm (1.4 mil) tin-plated copper foil and 0.053 mm (2.1 mil) conductive acrylic adhesive. Standard roll widths from 6.35 mm (0.25 in) upward are available; custom slitting tolerances should be confirmed against the supplier’s current slitting capability.

The foil side is solderable, which distinguishes CHO-FOIL CCJ from unplated smooth copper tapes and from aluminum shielding tapes. The tin finish also reduces copper sulfide and oxide formation that can increase contact resistance in sulfur-rich or humid service environments. In production, the tape is not intended for repeated flex-cycle service; the copper foil has limited elasticity and can crack under continuous bending. For static seam shielding and grounding, the foil remains dimensionally stable.

How does the CCJ configuration differ from standard copper foil shielding tapes?

Standard copper foil tape with a non-conductive adhesive provides no electrical path through the adhesive. In seam-sealing applications, the tape must be folded or pressed so that the foil directly contacts the substrate. This is not always possible in flat overlaps with only one accessible side. By contrast, the filled acrylic pressure-sensitive adhesive on CHO-FOIL CCJ has specified through-thickness conductivity. Current can pass from the substrate into the adhesive and then into the foil without a separate mechanical fastener, although a fastener or clamp is still recommended where dynamic stress or vibration is present.

Compared with CHO-FOIL CCH, an unplated copper foil tape in the same product family, the CCJ variant uses tin plating. The tin layer changes the surface chemistry: it supports direct soldering with Sn63/Pb37 or SAC305, reduces the formation of non-conductive copper oxide during storage, and alters the galvanic potential when the tape is applied to aluminum or zinc-coated surfaces. Compared with CHO-FOIL CCE, where the copper foil is embossed to improve drape over complex geometries, CCJ is specified where a smooth foil plane and solderable surface are more important than maximum conformability. Conductive fabric tapes typically have higher bulk resistivity than foil tapes and are used where repeated bending must be accommodated. Fabric tapes do not provide solder points. Aluminum foil tapes have lower electrical conductivity than copper and are not directly solderable; they can also create a larger galvanic offset when coupled to copper or silver-filled grounding structures.

Another distinction from die-cut elastomer gaskets is that foil tape provides no compressible recovery. Where enclosures require repeated access or mating-part tolerance, a conductive foam or spring gasket is used. The tape is not a replacement for compressible EMI gaskets in seams that undergo repeated opening and closing.

Electrical shielding performance, resistivity, and environmental limits

Typical electrical values published for CHO-FOIL CCJ include surface resistivity below 0.005 Ω/sq and volume resistivity below 0.001 Ω·cm when measured according to ASTM D257. The surface resistivity is dominated by the copper foil, while the volume resistivity includes the through-thickness contribution of the conductive adhesive. Plane-wave shielding effectiveness is reported above 80 dB from 30 MHz to 1 GHz using IEEE 299. At frequencies above 1 GHz, shielding effectiveness becomes dependent on aperture geometry, tape joint length, and termination impedance; published data for this specific configuration is limited.

Shielding effectiveness also varies with seam gap and aperture shape. A tape applied to a slot aperture creates a current path across the long dimension. If the tape bridges a gap without contacting both sides, slot resonance can occur at frequencies where the gap length approaches λ/2. The adhesive’s through-conductivity does not correct for an air gap beneath the foil; the tape must be pressed into the seam. The tape performs best when the seam gap is below 0.5 mm and the tape is burnished into the joint. For low-frequency magnetic-field shielding, thin copper tape is not a substitute for high-permeability alloy; its shielding mechanism is reflective and conductive, not absorptive at low frequency.

The continuous operating temperature range is specified from -40 °C to 125 °C. Peel adhesion declines as the acrylic pressure-sensitive adhesive approaches service temperatures above 80 °C under constant shear. The adhesive is thermoplastic and can soften with prolonged heat exposure. Exposure to strong organic solvents, ester plasticizers, or amine-containing surface treatments can soften the adhesive and reduce peel strength. Corrosion resistance is improved by tin plating but not absolute: in a humid chloride environment, a galvanic couple between tin-plated copper and bare aluminum can accelerate substrate attack. Where aluminum-to-tape contact is unavoidable, a non-conductive passivation layer or nickel-containing transition is used. Sulfur-bearing paper and latex gaskets can tarnish copper; the tin surface slows but does not eliminate this reaction.

Soldering to the foil face is possible with Sn63/Pb37 or SAC305. Local dwell time at the solder joint should not exceed 5 s at 260 °C, because heat conducts through the 0.036 mm foil and degrades the acrylic adhesive at the bond line. Hand soldering on installed tape should use a temperature-controlled iron; reflow soldering of the whole tape is not recommended. At seam lengths greater than λ/4, the tape acts as a grounded conductive strip rather than a continuous shield; multiple grounding contacts are required at intervals below λ/10 to preserve shielding.

When surface preparation and application pressure affect installed shielding consistency

Installation performance is bounded by substrate surface energy and application pressure. Low-energy plastics such as polypropylene and untreated polyethylene have surface energies below 36 dyn/cm; the acrylic adhesive does not wet these surfaces reliably. Corona treatment to 40–50 dyn/cm or atmospheric plasma exposure is used immediately before application to raise surface energy. The treated surface has a limited life: in ambient air, treatment decay can occur within hours or days depending on polymer formulation. Substrates must be cleaned of mold release, silicone oil, plasticizer bloom, and condensation. Isopropyl alcohol or a 50/50 isopropyl alcohol/water mixture is common for metallic surfaces; the solvent must evaporate fully before tape placement because residual solvent can be trapped under the foil and reduce adhesion.

Abrasion is not required for most machined aluminum or cold-rolled steel enclosures, but etched or chromated surfaces show improved peel strength. Application by hand uses a hard rubber roller. Uniform pressure is specified because the conductive adhesive develops contact through intimate wet-out. Air pockets under the tape degrade shielding at the seam; the tape is not self-leveling. In automated tape-laying equipment, closed-loop tension control is required. The thin copper foil can neck down under excessive unwind tension, reducing width and creating residual stress that lifts the tape from the substrate within hours of application.

Die cutting with steel-rule dies can produce burrs along the cut edge of the copper foil. Loose burrs can become conductive debris that bridges closely spaced traces or connector contacts. Hardened rotary dies and foam ejection pins reduce burr generation. Edge quality is most important in applications adjacent to exposed PCB conductors. Lot-to-lot variation in adhesion has been observed on production lines when rolls are stored past the supplier’s published shelf life or stored near external plasticizers; adhesive transfer to the liner may increase. Rolls should be rotated on a first-in-first-out basis.

Repeated flexing creates strain on the copper foil and can eventually crack the conductor. If the tape is wrapped around a cable or flex circuit that undergoes repeated bending, conductive fabric tape may be more suitable. For static seam shielding, grounding of connector backshells, and EMI door contact surfaces, the foil remains dimensionally stable. The tape is not self-leveling and does not fill gaps; the substrate joint must already be mechanically contiguous or the tape must be burnished into the gap with sufficient local deformation of the foil.

Storage should be maintained at 15–30 °C and 40–60 % RH. Moisture condensation during storage can accelerate tin oxidation and reduce adhesion. Rolls should be brought to ambient temperature before opening to prevent condensation on the adhesive. In applications involving outgassing-sensitive optical devices or vacuum equipment, supplier lot-specific outgassing data should be requested because published data for this specific configuration is limited.