Parker Chomerics CHO-FOIL CCE Shielding Tape is a copper-foil EMI shielding material supplied with an electrically conductive pressure-sensitive acrylic adhesive. The construction is intended for enclosure seam shielding, cable shield termination, and low-impedance grounding without soldered or mechanical fasteners. The product is identified by the designation CHO-FOIL CCE and is commonly slit from roll stock to application-specific widths. A dead-soft copper carrier is combined with a conductive acrylic PSA that forms a Z-axis electrical path across the adhesive bond line. Because installed shielding performance is controlled by seam contact resistance, overlap geometry, and substrate surface condition rather than by the foil carrier alone, release-to-production decisions should be based on supplier lot data for the specific tape width, substrate, and surface finish. The tape is applied in compliance-oriented electronics, including medical enclosures, instrumentation, and telecommunication modules, where conductive coatings or gasket attachment may be mechanically limited. The standard carrier thickness is commonly supplied at 0.1016 mm (0.004 in), with custom slit widths and die-cut configurations available from the manufacturer.

How does the conductive pressure-sensitive adhesive establish a low-resistance interface on enclosure substrates?

The adhesive layer is an acrylate-based viscoelastic system filled with conductive particles. Its Z-axis conductivity develops only when the PSA wets the substrate and establishes sufficient particle-to-substrate contacts. Painted enclosures, anodized aluminum, and low-surface-energy polymers such as polypropylene or acetal may not provide a reliable low-resistance interface without additional surface treatment. A solvent wipe with 70% isopropanol or a manufacturer-approved cleaner is normally required before application. Peel adhesion is evaluated according to ASTM D3330/D3330M-04, but conductive PSA values are not directly equivalent to nonconductive PSA values because filler loading alters viscoelastic flow and bond formation. On automated taping stations, edge lifting and micro-delamination are most likely where the tape crosses a sharp corner or where liner removal occurs before adhesive wet-out. A roller with a contact width equal to or greater than the tape width is used to apply pressure; visual flatness alone does not confirm a low-resistance interface. Peel force at the leading and trailing edges of the strip should be monitored because these zones often show lower pressure and higher variability than the center.

Shielding effectiveness is not an intrinsic tape property in isolation. When measured in accordance with IEEE 299-2006 or the legacy MIL-STD-285 method, the result applies to a specific fixture configuration, aperture size, edge termination, and frequency range. A copper-foil barrier can provide high plane-wave attenuation in a fully terminated test fixture; however, a PSA seam applied to a painted or passivated enclosure may leak along the adhesive-substrate interface long before the foil carrier becomes the limiting factor. The correct qualification approach is to measure the installed seam or closure in the intended housing with a fixture that replicates the enclosure joint and gasket-free PSA termination. Supplier-published data for CHO-FOIL CCE should be requested for the intended frequency range; where the exact enclosure configuration has not been evaluated, published data for that specific installed configuration is limited.

Surface Preparation Sequences and Peel Adhesion Boundaries

Adhesion performance of the acrylic PSA is highest when the substrate is clean, dry, and free of mold-release agents, silicone oils, and oxidized plasticizers. A production line cleaning sequence should include a dry wipe, a solvent wipe with 70% isopropanol or a manufacturer-approved cleaner, and a final dry cloth pass. Low-surface-energy polymers such as polypropylene, acetal, and thermoplastic olefins do not wet adequately with acrylic PSA and may require corona, plasma, or adhesion promoter treatment before tape application. Painted surfaces bond to the coating, not the polymer beneath; adhesion is therefore limited by the coating’s own adhesion to the substrate. On flame-retardant polycarbonate/ABS blends, mold-release additives can inhibit adhesion and should be removed before lamination. Reworked parts should not receive a second layer over a contaminated first layer; the original tape should be removed and the surface re-cleaned.

Differences from other shielding tapes are evident in both electrical and mechanical behavior. A copper foil tape with nonconductive adhesive requires an exposed foil surface or a mechanical fastener to create a grounding path; CHO-FOIL CCE avoids this because the PSA itself is conductive. Compared with conductive fabric tapes, the copper carrier produces a higher plane-wave attenuation per unit thickness but has lower conformability around compound curves and repeated flexures. Fabric tapes are therefore specified for hinged or irregular surfaces, while CCE is selected for seam sealing, flat grounding pads, and cable wrap where a metal barrier is required. Aluminum foil tapes may be lower in cost, but aluminum forms a nonconductive oxide and may create galvanic couples when applied to copper or steel surfaces in humid environments. Bulk conductivity values illustrate the carrier difference: copper is approximately 5.8 × 10⁷ S/m, whereas aluminum is approximately 3.5 × 10⁷ S/m. Despite this difference, installed shielding level is not governed by carrier conductivity alone; seam termination and adhesive contact resistance frequently dominate.

On automated production lines, tape placement is often followed by a post-lamination resistance check. A four-wire DC measurement is made across the applied seam with a milliohm meter; the acceptance limit is set from the enclosure shielding requirement rather than from the tape manufacturer’s generic surface resistivity. Because the conductive PSA path is lower in cross-sectional conductivity than the copper carrier, the measured resistance may be dominated by the adhesive interface. If the value exceeds the limit, the corrective action should distinguish between poor adhesive wet-out, contamination, insufficient pressure, and dimensional mismatch of the tape width to the seam. Electrostatic discharge control for the production area is referenced in IEC 61340-5-1, and conductive packaging should be used for converted parts where static-sensitive devices are handled nearby.

When process conditions include elevated humidity, thermal cycling, or painted seams

Acrylic PSA systems in this class are typically evaluated for continuous service below 85°C, with short-term excursions above that value requiring review of the supplier’s thermal aging data. Sustained humidity above 85% RH can reduce peel strength and promote corrosion at the exposed copper foil edge. If the enclosure is subjected to thermal cycling, differential expansion between copper and polymer substrates may create shear stress at the adhesive interface; this is more severe on large flat panels than on small die-cut parts. In marine or salt-fog environments, exposed copper edges require corrosion qualification; a tin- or nickel-plated foil or edge encapsulation may be required. The user should request ASTM D3654/D3654M-06 accelerated aging data and ASTM B117 salt spray data if the application involves outdoor exposure or condensation. CHO-FOIL CCE is not a structural adhesive, is not intended for continuous immersion, and should not be used as a sole mechanical fastener.

Where a pressure-sensitive adhesive tape is accepted as a Recognized Component, the supplier usually references UL 510 for flame and insulation properties. A current UL file should be requested during design review; recognition is not universally valid for all thicknesses and widths. The product family is generally declared according to RoHS 2011/65/EU, Annex II, and Regulation (EC) No 1907/2006 for REACH SVHC communication, but the user must verify current supplier certificates before production release.

Die-cut CHO-FOIL CCE parts are often supplied on kiss-cut liners or as multi-part arrays for high-volume placement. The release liner configuration and die-cut geometry influence peel-off force during automated pick-and-place. If the liner is too tightly cut, adhesive transfer may occur; if the liner is too loose, parts can shift in the shipping package. Incoming inspection should verify that the liner releases cleanly and that the conductive adhesive remains intact on the foil. A part with exposed liner adhesive or damaged copper edge should be rejected before placement because seam continuity may be compromised. For portable diagnostic devices and other small enclosures, the tape is typically converted into pad shapes that cover exposed seams and overlapped edges; the part must not be allowed to bridge isolated circuit nodes unless intentional grounding is designed.