Specified as a graphite-based thermal interface material, Saint-Gobain Furon C695 Thermal Graphite Tape is supplied in roll form with a pressure-sensitive adhesive on one face and a removable release liner. Manufacturer-published data place in-plane thermal conductivity at 1 600 W·m⁻¹·K⁻¹ and through-plane thermal conductivity at 6 W·m⁻¹·K⁻¹, determined by ASTM E1461-13 laser flash diffusivity on 0.100 mm sheet. The graphite layer is supplied in standard thicknesses of 0.025 mm, 0.050 mm, and 0.100 mm; nominal density is 1 800 kg·m⁻³ per ASTM D792-20. The adhesive layer is typically 0.025 mm thick. The material is intended to spread heat laterally from discrete hot spots before conduction through the thickness into a heat sink, chassis, or display frame. Flame rating is UL 94 V-0 at the stated thickness range. Compliance with RoHS Directive 2011/65/EU and REACH Regulation (EC) No 1907/2006 is stated in manufacturer documentation.

Material Constitution and the Role of Anisotropic Graphite Orientation

The graphite layer in C695 is produced as a densified sheet with strongly oriented basal planes. This orientation creates the characteristic anisotropy: lateral phonon transport is efficient and yields the published in-plane conductivity of 1 600 W·m⁻¹·K⁻¹, while cross-plane transport is limited by interlayer interfaces and falls to 6 W·m⁻¹·K⁻¹. Design calculations for a thermal bridge must therefore treat the tape as a lateral heat spreader rather than a through-plane conductor. The acrylic pressure-sensitive adhesive is applied at approximately 0.025 mm thickness and is protected by a coated release liner. Liner removal force is controlled under ASTM D3330/D3330M-04 Method A, with manufacturer-controlled values typically between 0.05 N/25 mm and 0.30 N/25 mm. Because the graphite layer is electrically conductive in the basal plane, isolation from adjacent circuits is required when the tape is used near exposed terminations.

What Limits the Use of PSA-Backed Graphite Tapes at Sustained Edge Temperatures?

Sustained exposure at the upper edge of the published operating range produces two failure modes that are not always apparent in short-term thermal conductivity screening. The first is adhesive softening and creep at temperatures above 120 °C; the second is oxidative degradation of the graphite surface if the part is repeatedly cycled to the upper temperature limit in air with exposed cut edges. The manufacturer publishes a continuous operating range of -20 °C to 120 °C, but thermal ageing data for this specific configuration are limited and should be verified for each application. Where outgassing is critical, users typically apply ASTM E595-15 screening; manufacturer-published total mass loss and collected volatile condensable material values for C695 are not uniform across all thicknesses and should be requested before use in sealed optical cavities. The tape meets UL 94 V-0 flammability at the specified thickness range, but the presence of the adhesive layer means that flame propagation behavior can shift with liner removal and substrate type.

In high-volume rotary die-cutting, the graphite layer exhibits brittle fracture behavior that differs from polymer-based thermal pad materials. When kiss-cutting 0.100 mm total thickness with a rotary die press running at 30 strokes/min, edge delamination is observed when die clearance exceeds 0.02 mm; the graphite fractures at the cut line while the adhesive remains intact and creates lint-like edge debris. Production lines using flatbed kiss-cut configurations with 100 kN cutting force report cleaner edges when the blade is maintained at a sharpness of 0.010 mm tip radius or better. Lamination of die-cut C695 parts onto displays and midframes is commonly performed at nip pressures between 0.3 MPa and 0.5 MPa. Entrapped air is reduced when the substrate surface energy is above 38 dyn/cm and the surface is cleaned with isopropyl alcohol before lamination.

When Adhesive Selection Determines Gap-Filling Performance

The pressure-sensitive adhesive layer is the limiting element in through-plane thermal resistance and mechanical attachment. C695 is not a compressible gap filler; it does not conform to surface roughness in the same manner as a silicone pad. The graphite sheet itself is rigid enough to maintain planarity but is not designed to absorb large mounting tolerances. The adhesive layer provides attachment on clean, smooth substrates, but thermal impedance under ASTM D5470-17 will increase if contact pressure is low or if the substrate surface is textured. Published data for this specific configuration are limited, and measurements should be made with the actual substrate pair and clamping load rather than extrapolated from bulk conductivity values. For applications where through-plane heat transfer exceeds lateral spreading, a silicone-based gap filler or a phase-change material may be more appropriate.

For mobile display assemblies, the tape is frequently die-cut into U-shaped parts that bridge the driver integrated circuit region and the metal midframe. In this configuration the high lateral conductivity of C695 moves heat away from a concentrated hot spot before the adhesive and air gap become the through-plane bottleneck. Field data from production lamination lines show that a nip pressure of 0.4 MPa reduces visible air entrapment without crushing the graphite edge. Because the graphite is anisotropic, part orientation must be controlled in the die-cutting fixture: rotation of the part by 90° changes the principal heat-spreading direction relative to the source. In lithium-ion battery pack thermal management, C695 has been used between prismatic cell faces and aluminum cooling plates. In such assemblies, the graphite layer is electrically conductive in the basal plane, so a minimum creepage distance of 2 mm from cell tabs and busbars is maintained in production drawing controls. The tape does not replace electrical isolation film; where cell-to-cooler isolation is required, a separate dielectric layer must be used.

Assessing the Differences Between C695 and Silicone-Based Gap Fillers

Compared to silicone-based gap filler pads, C695 provides negligible through-plane conformability and is not intended to bridge variable air gaps. A silicone pad with a thermal conductivity of 3 W·m⁻¹·K⁻¹ may outperform C695 in a rough interface with 0.5 mm tolerance because the pad deforms and fills the gap, while the graphite tape depends on adhesive wet-out and a flat interface. Compared to copper foil, C695 offers lower mass density and anisotropic transport, but it does not provide isotropic heat spreading. Copper foil at 380 W·m⁻¹·K⁻¹ conducts equally in all directions; C695 is limited to approximately 6 W·m⁻¹·K⁻¹ through-plane. Compared to generic graphite tapes, C695 is differentiated by its controlled adhesive system and documented compliance with UL 94 V-0 and halogen-free requirements based on IEC 61249-2-21. Silicone-free composition is a further differentiator for applications where silicone outgassing or siloxane migration is not acceptable.

In battery module assembly, the substitution of C695 for a silicone gap pad changes the thermal path from a compressible through-plane interface to a lateral-spreading sheet with a thin adhesive bond. This substitution is valid only when the mounting stack tolerance is held below the adhesive wet-out limit, typically 0.10 mm, and when the interface surfaces are flat to within 0.05 mm over the part footprint. At relative humidity above 60 %, liner release force and adhesive tack can vary; preconditioning at 23 ± 2 °C and 50 ± 5 % RH for 24 h before lamination is recommended. Avoid continuous exposure to aromatic hydrocarbons, ketones, and esters above 200 ppm, because PSA swelling can reduce peel strength below 50 % of the initial 8 N/25 mm value. The graphite layer is not intended to carry structural load or to function as a primary electrical insulator. When the tape is specified for power electronics near exposed conductors, additional insulation and mechanical retention are required.