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TFLEX 300 Series: Legacy Gap Fillers and the New HD Alternatives

by | Aug 22, 2025 | Artificial Intelligence, Die Cutting, Electrical Insulators, Thermal Pads

TFLEX 300 Series: Legacy Gap Fillers and the New HD Alternatives

The TFLEX® 300 series has long been a trusted name in thermal interface materials (TIMs). Designed for reliable heat transfer and ease of integration, this family includes TFLEX 300, TFLEX 300H, and TFLEX 300TG. Each variation offers a unique balance of compliance, mechanical strength, and thermal performance.

However, as devices demand higher heat dissipation and long-term reliability, Laird has introduced TFLEX HD300 and TFLEX HD300TG as the new alternatives to the legacy 300 line. In this blog, we’ll explore the technical properties of the original TFLEX 300 series and explain why engineers are now encouraged to transition to the HD300 series.

TFLEX 300: The Baseline

The TFLEX 300 pad established the foundation for the series. It is a soft, compliant thermal gap filler designed to minimize stress on sensitive components while ensuring a reliable thermal path.

Technical Highlights:

  • Moderate thermal conductivity suitable for general-purpose applications

  • Excellent compressibility, conforming to surface irregularities

  • Soft mechanical profile to protect fragile components

Typical Applications:

TFLEX 300H: High-Durability Variant

The TFLEX 300H builds upon the base material with a slightly harder formulation, enhancing its mechanical integrity.

Technical Highlights:

  • Firmer Shore hardness compared to TFLEX 300

  • Reduced pump-out during thermal cycling

  • Improved resistance to tearing or deformation under repeated assembly

Ideal Use Cases:

  • Automotive electronics exposed to vibration

  • Telecom infrastructure requiring long-term stability

  • Ruggedized industrial electronics

  • Repositionable pad due to the hardened back surface.

TFLEX 300TG: Fiberglass Carrier Reinforced

Unlike the baseline and H variants, the TFLEX 300TG incorporates a fiberglass carrier. This reinforcement provides dimensional stability during handling, die-cutting, and assembly.

Technical Highlights:

  • Embedded fiberglass carrier for mechanical reinforcement

  • Maintains structural integrity in thin profiles

  • Improves die-cutting precision for complex geometries

  • Reduces stretching or warping during assembly

Applications:

  • Thin-profile thermal stack-ups

  • Modules requiring intricate pad geometries

  • Situations where stability during placement is critical

The Evolution: TFLEX HD300 & HD300TG

As electronics become more compact and power-dense, the limitations of legacy gap fillers are more apparent. Laird’s TFLEX HD300 and TFLEX HD300TG were designed as direct replacements for the TFLEX 300 series.

TFLEX HD300

  • Higher thermal conductivity for improved heat dissipation

  • Better compression set resistance for long-term reliability

  • Optimized for today’s high-power devices such as AI accelerators, ADAS modules, and telecom gear

TFLEX HD300TG

  • Same improved thermal and mechanical performance as HD300

  • Includes a fiberglass carrier, directly replacing TFLEX 300TG

  • Designed for precision die-cutting and applications requiring carrier support

Why Upgrade from TFLEX 300 to TFLEX HD300?

Modern applications demand more robust materials. While the 300 series remains functional in lower-power systems, the HD300 line offers future-proof performance by handling higher heat flux, providing superior long-term stability, and reducing failure modes like pump-out or deformation.

Industries Benefiting from HD300 Series:

  • Automotive (ADAS, EV power modules)

  • Telecommunications (5G base stations, high-load radio units)

  • High-performance computing (servers, AI accelerators, GPUs)

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