The present invention provides a low-modulus low-stress resin which has such heat resistance that cohesive force and reliability can be retained even at high temperatures and which is applicable as various functional materials. The resin is a thermoplastic resin having a modulus of elasticity at room temperature, 25° C., of 1 GPa or lower and a modulus of elasticity at 250° C. of 1 MPa or higher, or a precursor resin thereof.