Parker develops low-bleed thermal interface pad

Parker Hannifin has introduced THERM-A-GAP PAD 120LOE, a thermally conductive gap filler designed to limit silicone oil migration while maintaining heat transfer between electronic components and their cooling structures.

Developed by the company's Chomerics Division, the material provides a specified thermal conductivity of 12 W/mK and combines an electrically insulating formulation with low compression forces. It is intended for applications where heat dissipation, mechanical stress, and the possibility of material contamination must be considered together.

The product is being introduced during electronica 2026 in Munich, following a 10 November announcement from the company's UK operation. Target applications include processors, graphics hardware, memory assemblies, telecommunications equipment, automotive electronics, battery systems, and defence equipment.

Thermal gap fillers provide a conductive path between heat-generating components and surfaces intended to dissipate that heat. Manufacturing tolerances and surface roughness prevent two nominally flat surfaces from making continuous contact, leaving small air gaps that increase resistance to heat transfer.

A compliant interface material deforms to fill these irregularities, reducing the amount of poorly conducting air trapped between the surfaces. The resulting thermal performance depends on the material's conductivity, installed thickness, contact area, and the resistance created at its interfaces with the adjoining components.

PAD 120LOE uses a silicone-based elastomer formulation with a hardness of 45 Shore 00, measured according to ASTM D2240. Its compliance allows the material to accommodate uneven surfaces while limiting the force transferred to components when the assembly is compressed.

Mechanical loading becomes important when a heatsink or enclosure is brought into contact with integrated circuits mounted on a printed circuit board. Excessive pressure can bend the board, stress solder joints, or impose loads on semiconductor packages. Insufficient compression, however, may leave gaps that compromise thermal contact.

Parker has formulated the pad to exhibit stress relaxation after installation, reducing the sustained compressive force while maintaining contact with the surrounding surfaces. The manufacturer also identifies vibration damping and physical protection among its characteristics.

Stress relaxation must be distinguished from complete mechanical recovery. A material that becomes less forceful under constant compression does not necessarily return to its original dimensions after removal. Applications requiring repeated assembly and disassembly must therefore assess the relevant recovery and reuse characteristics separately.

The second focus of the new formulation is silicone oil migration. Some silicone-based thermal interface materials can release mobile constituents during service, particularly when exposed to sustained temperature and pressure. Such migration can create manufacturing, appearance, or contamination concerns depending on the surrounding electronic assembly.

Components incorporating optical surfaces, sensitive contacts, or closely spaced mechanical interfaces may require particular control over substances capable of spreading beyond the intended thermal contact area. The appropriate restriction depends on the equipment design and the contamination requirements established for its operating environment.

Parker describes PAD 120LOE as having very low oil bleed and migration, with the formulation developed through several material evaluation methods. The product remains a silicone-based material; its low-bleed designation does not establish that it contains no silicone oil or that migration is impossible under every service condition.

The manufacturer's specified conductivity of 12 W/mK describes heat conduction through the material under defined measurement conditions. It does not establish the temperature reduction available in a completed electronic assembly, where the final result depends on the entire thermal path.

Gap thickness creates a direct design trade-off. A thicker pad can bridge greater mechanical tolerances, but heat must travel through more material. In a simplified one-dimensional conduction model, thermal resistance increases with thickness and decreases with conductivity and contact area.

Actual assemblies introduce additional factors, including non-uniform compression, local heat concentration, contact resistance, and variations in surface geometry. An interface material must consequently be evaluated in the intended mechanical arrangement rather than selected solely by its bulk conductivity rating.

PAD 120LOE is supplied in standard thicknesses from 1 to 5 mm. Parker offers sheets measuring 254 × 381 mm and custom die-cut parts, allowing the interface to be shaped for individual semiconductor packages or assemblies containing several heat-generating components.

The material has a high-tack surface intended to improve contact with adjoining components. It is electrically insulating, with Parker specifying dielectric strength of 8 kVAC/mm and volume resistivity of 10¹⁴ Ω-cm under the applicable test methods.

Electrical insulation can be important where a cooling structure approaches exposed conductors or components operating at different electrical potentials. The published material properties provide useful selection data, although the insulation performance of a complete assembly must also account for pad thickness, geometry, operating voltage, and applicable safety requirements.

The pad carries a UL 94 V-0 flammability classification and is specified for operation between -50°C and +200°C. These material-level characteristics do not independently qualify a completed electronic product for a particular automotive, industrial, or defence application.

Repeated temperature changes can alter the contact conditions within an electronic assembly as component packages, boards, and cooling structures expand at different rates. The material must remain sufficiently compliant to accommodate those changes while preserving the intended heat-transfer path.

Parker positions the low-bleed formulation for long-life electronic products where heat dissipation and material stability are both important. The manufacturer has not published a universal improvement in semiconductor temperature or a guaranteed service life applicable to every installation.

The new pad is available in standard and custom formats. Selection will depend on the heat load, allowable component temperature, gap dimensions, compression limits, environmental conditions, and contamination requirements of the finished electronic assembly.