HEAT-RESISTANT BUFFER SHEET AND HOT-PRESSURIZING TREATMENT METHOD

A provided heat-resistant cushioning sheet is a heat-resistant cushioning sheet configured to be disposed between a thermocompression face of a thermocompression apparatus and a target in thermocompression treatment of the target to prevent direct contact between the target and the thermocompression face, wherein a compression strain change amount ΔS250 being a difference S250 - S25 between a compression strain S25 at 25°C and a compression strain S250 at 250°C is -5% or more. S25 and S250 are each a compression strain ST of the heat-resistant cushioning sheet evaluated by thermomechanical analysis (TMA), S25 is evaluated at an evaluation temperature of 25°C, and S250 is evaluated at an evaluation temperature of 250°C. The compression strain ST is determined by an equation ST = (t1 - t0)/t0 × 100 (%), where to is a thickness of the heat-resistant cushioning sheet at 25°C and t1 is a thickness of the heat-resistant cushioning sheet at the evaluation temperature T (°C) under a compression force applied by TMA in a thickness direction of the heat-resistant cushioning sheet. The above heat-resistant cushioning sheet can be more reliably adapted to expected further increases in treatment temperature and pressure.