Parker Chomerics CHO-FOIL CCK shielding tape consists of a 0.036 mm (0.0014 in) rolled copper foil coated on one side with an electrically conductive acrylic pressure-sensitive adhesive. The product is supplied in CCK-18, CCK-36, and CCK-72 roll formats, corresponding to 18 yd (16.5 m), 36 yd (32.9 m), and 72 yd (65.8 m); common converter widths range from 12.7 mm to 610 mm. The release liner is removed during die cutting or at the application head, exposing the conductive adhesive for direct bonding to enclosure flanges, cable shields, and ground-plane surfaces. Typical applications include seam shielding on injection-molded enclosures, grounding of I/O connector gaskets, field repair of shielded rooms, and conductive bonding of fabric-over-foam EMI gaskets. The total tape thickness is nominally 0.099 mm to 0.110 mm, measured in accordance with ASTM D1000; the copper face is unplated, which preserves solderability but requires corrosion management in wet environments.

Compared with nonconductive acrylic copper tapes, CCK provides a through-conductive bond line rather than a capacitive gap. Compared with aluminum foil tapes, it offers lower volume resistivity and better low-frequency shielding per unit thickness but higher galvanic mismatch with aluminum substrates. The conductive adhesive is not a nonconductive mounting adhesive; its electrical continuity is the primary specification driver in grounding and seam-shielding applications.

This table is a compilation of manufacturer-reported typical values; lot-specific certificates may vary because conductive acrylic formulations can shift with filler type, coat weight, and liner lot. Compliance statements should be requested per RoHS Directive 2011/65/EU and REACH Regulation EC 1907/2006 for the specific roll or converted part.

When Slot-Aperture Leakage Dominates Over Foil Conductivity

Shielding effectiveness for a seam tape is controlled by aperture geometry once the foil is electrically continuous. At 30 MHz, skin depth in pure copper is approximately 21 μm, so the 36 μm foil exceeds one skin depth and contributes both reflection and absorption loss. At 1 GHz, skin depth decreases to approximately 2.1 μm, but enclosure-seam measurements often degrade to 40–60 dB when the tape edge is not burnished or when the flange gap exceeds 0.1 mm. Slot-aperture leakage is proportional to aperture length; even a 0.5 mm gap can dominate the shielding budget. For continuous grounding, the tape must be applied over a closed seam and rolled with a conductive or nonconductive pressure roller to displace entrapped air. The conductive adhesive cannot bridge a 0.2 mm step on anodized flanges; an electrically bonded gasket or mechanical compression is required.

Transfer impedance, not DC resistance alone, is the more relevant parameter for seam leakage below 100 MHz. For a seam tape, transfer impedance is influenced by the number of conductive paths through the adhesive and by the contact area. The conductive adhesive’s particle network is stochastic; under compression, through-resistance decreases with pressure up to approximately 2.1 MPa, beyond which foil deformation and adhesive squeeze-out can reduce the bond line. Published data for this specific configuration is limited, so in-process verification should be conducted on the actual flange geometry.

Testing per MIL-STD-285 or IEEE 299 should use the assembled seam, because tape coupon data over a uniform metal substrate overestimates enclosure-level isolation. At frequencies below 1 MHz, copper has limited magnetic-field shielding performance because relative permeability is approximately unity. High-permeability alloys such as mu-metal are required for low-frequency magnetic attenuation. Published measurement data for CCK in low-frequency magnetic-field shielding configurations is limited; qualification should be performed in the installed enclosure geometry.

Automated enclosure lines typically apply CCK from a roll-fed head with 60 Shore A silicone nip rollers. A nip pressure of 0.14–0.28 MPa (20–40 psi) is sufficient to eliminate visible air channels on rigid flanges; however, roller alignment across the flange should deviate no more than ±0.05 mm per 100 mm to prevent adhesive void formation. Die-cut converters process CCK on rotary or flatbed presses with air-cycled ejection to control adhesive stringing. Peeled liner release values are typically in the 0.05–0.15 N/cm range at 180°; liner removal must be conducted under ionized air if the work area has a static potential above 100 V.

Die-cutting copper foil produces greater tool wear than aluminum foil tape. Rotary dies require carbide or powdered-metal blades, and edge burr formation can begin when blade clearance exceeds 0.012 mm. Roll-to-roll variation in adhesive coat weight is typically controlled to ±5% of nominal; incoming inspection should include surface-resistance mapping across the roll width at 100 mm intervals using MIL-STD-202G Method 307 to identify high-resistance islands caused by conductive filler distribution.

What Are the Adhesive’s Practical Surface-Energy Boundaries?

The conductive acrylic pressure-sensitive adhesive in CCK has a measurable drop in peel strength when the substrate critical surface tension falls below 38 mN/m. On stainless steel panels cleaned with reagent-grade isopropyl alcohol, manufacturer-reported peel adhesion exceeds 4.4 N/mm; on untreated polypropylene or heavily silicone-contaminated surfaces, values below 1.8 N/mm are commonly observed. The adhesive is not load-bearing under sustained peel or shear: sustained static load should not exceed 0.35 N/cm at 23 °C, and elevated temperature reduces this limit. The tape provides an electrical path but does not replace screws, snap features, or compression gaskets in structural grounding connections.

Surface preparation has greater influence on long-term adhesion than initial tack. Mold-release residues, silicone oils, and plasticizer haze should be removed with reagent-grade isopropyl alcohol or a 50:50 isopropyl alcohol/deionized water solution, followed by lint-free wipe drying. For molded polycarbonate/ABS and polyphenylene oxide blends, plasma or corona treatment should raise the surface energy above 38 mN/m before tape placement. Peeling a sample at 90° and 300 mm/min after 20 min dwell is a practical incoming inspection method; full adhesion develops over 24–72 h depending on temperature and substrate polarity.

One failure mode observed on production lines is edge lifting after 72 h due to springback on curved flanges. Radial bends tighter than 12 mm require heat forming at 40–50 °C or mechanical clipping. On conductive fabric-over-foam gaskets, CCK is used to bond the gasket to an enclosure flange. The tape’s through-bond resistance is lower than a nonconductive pressure-sensitive adhesive, but total joint resistance is dominated by the gasket-to-tape interface, not the tape itself.

Corrosion Coupling at Copper-to-Aluminum Joints

CCK has an unplated copper surface, and direct application to aluminum flanges creates a galvanic couple in condensing humidity. The standard reduction potential for copper is +0.34 V versus standard hydrogen electrode, while aluminum is −1.66 V versus SHE; the resulting potential difference is 2.00 V. If a continuous electrolyte film forms at the tape edge, the aluminum flange becomes the anode and can pit. Indoor electronic equipment maintained below 60% RH with minimal thermal condensation is generally compatible, but outdoor or marine enclosures require a tin-plated copper tape, a nickel-plated copper tape, or an insulating overcoat applied over the tape edge.

When CCK is used on aluminum, the joint should be electrically sealed or mechanically protected within 24 h of application in high-humidity conditions. A 50 μm acrylic or polyurethane overcoat applied over the tape edge reduces electrolyte ingress but does not eliminate the underlying couple if moisture is already trapped. Users should avoid placing CCK in direct contact with unpainted galvanized steel without a compatibility check, because the copper-zinc couple can also produce corrosion under wet storage.

On cable-shield applications, CCK is spiral-wrapped with 50% overlap under 4.4 N tension; the wrapped shield must maintain at least 0.25 mm separation from signal conductors to avoid capacitance loading. The conductive adhesive secures the overlap region, but mechanical cable ties or shrink tube are required for vibration environments above 10 g rms. On printed circuit board ground-plane repairs, the copper foil can be soldered at its edges; soldering temperatures above 232 °C for more than 3 s can compromise the acrylic adhesive bond line, so heat sinking or low-temperature solder is used when the tape is not mechanically clamped.

Storage at 21 ± 3 °C and 50 ± 10% RH is specified for a 12-month shelf life. Rolls should not be stored below 5 °C before application; condensation during thawing can create microvoids at the adhesive-copper interface. High humidity accelerates copper oxide growth on exposed edges, which may require edge trimming prior to use. Direct contact with PVC containing uncured plasticizer or with room-temperature acetoxy-cure silicones should be avoided; plasticizer migration reduces peel strength, and acetic acid accelerates copper tarnish. Neutral-cure silicones are preferred when adjacent sealing operations release cure byproducts.