High-temperature PCB materials are engineered to maintain structural and electrical integrity at temperatures exceeding 170°C, with tolerance levels varying significantly by material type, defined by Tg (glass transition temperature), Td (decomposition temperature), and continuous operating temperature. Standard FR-4 (Tg 130–140°C) can only operate continuously below 110°C, while high-performance substrates like polyimide, ceramic, and BT epoxy withstand 200°C+ continuous use, catering to aerospace, automotive, and high-power electronics.

High-Tg FR-4 (170–180°C Tg) is the most common cost-effective high-temperature material, supporting continuous operation at 130–150°C and short-term exposure up to 200°C. Modified epoxy formulations enhance its thermal stability, making it suitable for industrial power supplies and automotive non-engine compartments. BT epoxy (Tg 180–200°C) offers better heat resistance than high-Tg FR-4, with continuous operation up to 160°C, ideal for high-density interconnects and semiconductor packaging.

Polyimide (PI) substrates are the premium organic high-temperature material, with Tg 250–400°C, continuous operating temperature up to 260°C, and short-term tolerance to 300°C. Their aromatic molecular structure provides exceptional thermal stability, resisting decomposition above 500°C. PI is widely used in aerospace, military, and foldable devices, though at higher cost. Ceramic substrates (alumina, aluminum nitride) offer the highest temperature tolerance, with no Tg (inorganic) and operation exceeding 350°C, plus excellent thermal conductivity (20–200 W/m·K) for high-power heat dissipation.

PTFE (Tg ≈-120°C) excels in high-frequency high-temperature applications, with continuous operation up to 260°C and short-term exposure to 500°C, despite its high CTE. Material selection follows the "20–25°C rule": Tg must exceed the maximum operating temperature by 20–25°C to ensure reliability. For example, a 150°C operating environment requires a minimum 170°C Tg material to prevent softening and failure.