3M 1115B EMI Shielding Tape is constructed from an embossed copper foil backing bonded to a conductive acrylic pressure-sensitive adhesive. The nominal total thickness is 0.089 mm (3.5 mil). Standard roll widths supplied through authorized converting channels commonly include 25 mm, 50 mm, and 100 mm; custom slitting and die-cut geometries are available. The construction is declared compliant with EU 2011/65/EU as amended by (EU) 2015/863, with supplier documentation under Regulation (EC) No 1907/2006. The product is used where a conductive path must bridge an enclosure seam without soldering or mechanical fastener penetration. The embossed foil permits in-plane deformation that smooth rolled foils do not tolerate without fracture, while the conductive acrylic layer allows current to pass through the adhesive interface when compressed.

Construction data and referenced test methods

How does the through-adhesive current path develop under applied pressure?

Through-adhesive resistance is not a single material constant. The pressure-sensitive adhesive contains conductive particles that establish a percolating network only when the adhesive is flowed against the substrate. If the tape is hand-pressed without a roller, measured interface resistance can exceed 1.0 Ω over a 25 mm² electrode area. When the tape is applied with a 2 kg steel roller moving at 10 mm/s to 25 mm/s, the conductive particles are compressed into the substrate topography, and through-adhesive direct-current resistance measured by a four-wire probe commonly falls below 0.05 Ω. The embossed copper foil supplies the lateral low-resistance path, but seam effectiveness is controlled by constriction resistance at the adhesive-to-enclosure interface. On a zinc-plated steel chassis with Ra 0.4 µm surface finish, adhesion is generally stable; on a cast aluminum housing with Ra 1.6 µm or higher, the adhesive must wet deeper valleys. Production lamination using a rubber-covered roller with Shore A hardness of 40 to 60 is therefore required rather than optional finger application.

For enclosure flange seams, the tape is applied with 2 mm to 3 mm extension over each side of the split line. Excess compression during assembly can extrude the acrylic layer and reduce effective overlap; insufficient compression leaves high interface resistance. The applied part should be burnished along the edge to avoid fillet lift. On automated taping lines, liner release tension should remain below 0.15 N/mm width to prevent curl. Edge lifting at 15 °C is a recognized production failure because acrylic pressure-sensitive adhesive exhibits reduced tack below 10 °C; parts should be conditioned at 20 °C to 25 °C and low humidity before lamination.

If the tape is processed by rotary die-cutting, what parameters control edge quality?

Rotary die-cutting of a 0.089 mm copper foil adhesive laminate requires attention to tool clearance and release-liner stiffness. Tool clearance below 0.005 mm may reduce die life and generate copper slivers; clearance above 0.015 mm can leave uncut adhesive filaments and cause part-removal defects on the liner. Cutting speeds of 15 m/min to 40 m/min are typical on flatbed and rotary presses, but optimum speed depends on liner type and die temperature. The embossed foil surface produces load-cell force spikes at the emboss pattern, so converter presses should be equipped with force monitoring to prevent partial-depth cutting. If parts are lifted from the liner by vacuum heads after cutting, silicone transfer from the liner can contaminate the adhesive; liner release force and surface analysis should be part of incoming inspection. Liner slitting burr control is also critical because a torn liner creates adhesive pick-off and causes placement errors on automated pick-and-place lines.

Substrate preparation should precede tape application. Isopropyl alcohol or a process-compatible electronic-grade solvent removes machining oils and handling salts; organosiloxane mold release must be removed by alkaline cleaning or plasma treatment. Peel strength loss greater than 50 % on cleaned stainless steel per ASTM D3330 indicates residual contamination. The conductive acrylic is not a gap filler; it cannot bridge a seam wider than 1 mm without mechanical support, and it does not replace an EMI gasket in high-cycle or high-compression joints.

Seam shielding effectiveness across the 30 MHz to 1 GHz band

Shielding effectiveness is driven by the aperture formed by the seam. An open slot of length 10 cm can radiate significantly near its half-wavelength resonance; application of 3M 1115B over the slot reduces slot aperture coupling but does not restore full unperforated enclosure shielding. Transfer impedance values measured on assembled joints vary with contact pressure and joint flatness; published data for this exact tape in a standardized IEEE STD 299 enclosure are limited, so assembly-level verification is required. The copper foil remains useful as a reflective shield above 1 GHz only if the seam length remains electrically small; at 10 GHz, even a 2 mm application gap can leak unless the tape is continuous and conductive across the discontinuity. The product does not provide significant magnetic-field absorption below 100 kHz. For low-frequency magnetic shielding, a high-permeability material such as a nickel-iron alloy tape is required in addition to the conductive seam treatment.

Compared with smooth copper foil tape, the embossed backing of 3M 1115B accepts a larger radius of curvature without fracturing. For flat, tightly toleranced grounding planes, smooth foil often provides a thinner edge profile; however, the thicker embossed construction supports better handling on contoured enclosure ribs and structural frames. The conductive acrylic adhesive is the primary functional difference from copper tapes using non-conductive acrylic. Those tapes require a soldered tab or direct metal-to-metal contact because the adhesive layer is insulating. The product is not double-sided and should not be used to bond two suspended substrates together; for that configuration a double-sided conductive tape or conductive transfer adhesive is required. Substitution of 3M 1115B for non-conductive adhesive copper tape requires no change to the grounding scheme only if the tape is pressed onto conductive surfaces with sufficient area to establish a stable through-adhesive path.

The conductive acrylic adhesive imposes a finite upper temperature limit

Acrylic pressure-sensitive adhesives are not designed for sustained exposure above their oxidative degradation threshold. In continuous thermal soak at 85 °C, the tape may retain most of its adhesion, but exposed copper edges oxidize and through-adhesive resistance can increase. At process temperatures above 105 °C, published data for this specific product configuration are limited. A silicone-based conductive tape or solderable copper strap should be considered where the assembly must withstand solder-reflow temperatures of 260 °C. The acrylic adhesive is also susceptible to attack by ketones, esters, and aromatic hydrocarbons; aggressive solvent cleaning after application may lift the edge and should be avoided.

Die-cut parts are supplied on a release liner. Liner removal should be performed at 20 °C to 25 °C. Storage is recommended at 15 °C to 25 °C and 40 % to 60 % relative humidity in original packaging, with a typical shelf life of 12 months from date of manufacture; after expiration, adhesion and conductivity should be reverified per ASTM D3330 and through-adhesive resistance. For high-volume production, first-article testing should include a shielding-effectiveness coupon per IEEE STD 299 and a peel-adhesion test on the actual enclosure alloy, because painted, conversion-coated, or textured surfaces shift both mechanical and electrical performance.