3M 1170 EMI Shielding Tape is a single-sided pressure-sensitive conductive tape consisting of a 0.0356 mm tin-plated copper foil backing and a 0.0356 mm electrically conductive acrylic adhesive layer. The nominal total thickness is 0.071 mm, and the product is supplied in log rolls with widths from 6.35 mm to 609.6 mm. The tin-plated copper surface provides a solderable and oxidation-resistant outer layer, while the acrylic adhesive contains conductive particles to establish through-bond electrical continuity after application. Typical uses include grounding of flexible display circuits, shielding of seam gaps in sheet-metal enclosures, static drain connection on telecom line cards, and shield-can edge termination. Compliance documentation from the manufacturer lists the product under RoHS 2011/65/EU and provides REACH SVHC status according to the current candidate list.

The values in the table are manufacturer-published typical properties, not batch specifications. Lot-to-lot variation in conductive adhesive particle loading can affect through-adhesive resistance, and qualification programmes should require certificate of analysis documentation when the tape is used on safety-critical or flight hardware.

Surface preparation involves a final wipe with isopropanol and full solvent evaporation before tape placement. Residual solvent can become trapped at the adhesive–substrate interface and create a high-impedance gap. The tape is applied with a roller or lamination nip because hand pressure alone may not generate sufficient contact force to collapse conductive particles into the substrate. Maximum peel adhesion develops after approximately 24 h at 23 °C as the acrylic flows into surface roughness. Automated placement on high-volume lines uses kiss-cut parts on a polyester liner; conversion with copper foil requires vacuum hold-down tooling to prevent folding of the 0.071 mm backing.

What Limits Through-Adhesive Resistance After Conductive Particle Settling?

Through-adhesive resistance is governed by the percolation network of conductive filler particles in the acrylic matrix. During application, compression brings the particles into temporary contact with the substrate and the foil backing. Subsequent adhesive relaxation can reduce contact force and increase resistance if the substrate is rough or if the joint is subjected to thermal cycling. The manufacturer’s quoted value of <0.01 Ω across a 1 in² lap is a contact-resistance measurement, not a bulk material resistivity. Under 85 °C/85% RH ageing, the tin-plated copper backing resists oxide formation better than bare copper, but the acrylic network can absorb moisture. This may produce reversible swelling and a small increase in through-adhesive resistance. The practical upper operational boundary is 155 °C continuous; above this, oxidative chain scission in the acrylic permanently degrades both adhesion and conductive contact. The product is therefore not a replacement for solder or welded joints where continuous current exceeds the tape’s current-carrying capacity. Published current-rating data for this specific tape configuration is limited; the manufacturer does not specify a continuous current limit for the adhesive layer.

When Tin-Plated Copper Replaces Bare Copper at Corrosion-Prone Seams

Compared with 3M 1181, which uses a bare copper foil backing, 3M 1170 substitutes a tin electrodeposit over the copper. The tin layer prevents rapid copper oxidation at the visible surface and permits direct solder wetting. In side-by-side comparison, a bare copper tape may show contact-resistance drift after 500 h at 85 °C/85% RH, whereas the tin-plated variant retains lower and more stable seam contact because tin oxide is thinner and disrupted more easily under mechanical wipe. However, tin plating is not galvanically compatible with aluminium in marine salt-spray environments. When attached to a 6061-T6 aluminium chassis, the copper-tin-aluminium couple can promote galvanic corrosion if the seam is not conformal coated. Designers should specify a non-conductive acrylic overcoat or polyurethane conformal coating after application in such environments. The manufacturer’s published salt-spray data for this specific geometry is limited; qualification under IEC 60068-2-52 or MIL-STD-810H Method 509.6 is therefore recommended before production release.

In automated assembly lines, die-cut 3M 1170 parts are placed by pick-and-place heads using vacuum cups. The 0.071 mm total thickness requires stiffener tabs or liners to prevent folding during transfer. Slitting blades must be sharp; a dull blade produces foil burrs that can bridge adjacent PCB traces. The roll is stored at 21 °C and 50% RH; exposure at 40 °C for more than 2 weeks can accelerate acrylic adhesive oxidation and reduce tack. For high-volume lines, the tape is kiss-cut onto a polyester liner and supplied as die-cut islands. Liner release force must be verified on downstream equipment because an excessively high release force can cause cohesive failure of the adhesive during liner removal.

Flat-Foil Construction, Embossed Alternatives, and Solder Termination Limits

Unlike embossed tapes such as 3M 1345 or 3M 1245, 3M 1170 uses a flat tin-plated copper backing. The flat foil minimises joint thickness, which is critical for slim-line enclosures and for maintaining a consistent ground plane under a shield can. Embossed tapes provide greater conformability over uneven surfaces and repeated peel stress, but they are thicker and may leave visible step heights. 3M 1170 is therefore selected when the substrate is flat or has gentle curvature, while embossed tapes are selected for complex die-cut shapes with bosses or irregular castings. The solder termination capability of 3M 1170 is limited by the acrylic adhesive below the foil. Soldering-iron tip temperatures of 315 °C to 370 °C can create local adhesive degradation after 2–3 s. Solder operations should use a temperature-controlled iron and a flux compatible with tin-plated copper. Reflow ovens with peak temperatures above 240 °C are incompatible with the tape unless the tape is added after reflow.

Thermal cycling from -40 °C to 85 °C can be applied after the tape has reached full adhesion. The acrylic adhesive has a low-temperature modulus increase below -40 °C, which reduces peel strength and can make initial application difficult without warming the substrate. The tape should not be applied to plasticised PVC cable jackets or surfaces coated with free silicone mould release. Plasticiser and silicone migration into the acrylic reduce peel adhesion and interfere with conductive-particle contact. Polyolefin, polyimide, and aluminium substrates are generally compatible. For seams that must be opened repeatedly, a conductive gasket with spring compression may provide more repeatable shielding; tape is preferred for permanent or low-cycle seams.

System-level shielding effectiveness of a seam treated with 3M 1170 is dominated by aperture geometry, seam length, and bonding impedance rather than by the intrinsic tape material. The tape reduces slot-antenna leakage when it bridges a seam. Planar shielding-effectiveness values for copper foil-backed tapes are reported in the range of 80 dB to 100 dB from 30 MHz to 1 GHz under ASTM D4935 planar material tests, but the installed value may be lower. Radiated-emission performance is not guaranteed by the tape alone; enclosure resonance and cable coupling dominate above 1 GHz. Compliance testing should be performed on the completed enclosure under the applicable standard, such as CISPR 32:2015 or MIL-STD-461G, because the tape cannot be characterised as a standalone EMI fix.

The product carries no independent UL electrical insulation rating. It is a conductive tape and must not be used where electrical isolation is required. The adhesive is not crosslinked and will creep under sustained peel load above 60 °C. Mechanical fasteners or clamps are required when the tape is used on load-bearing seams. The tape is compatible with conformal coating over-application after adhesion is fully developed, but coating solvents should be tested for compatibility with the acrylic adhesive before production use.