A perturbation technique is proposed for solution of the generalized equati
ons governing the thermal behaviour of thin metal films described by a hype
rbolic two-step model. The generalized equations of this model contains dif
fusion terms in both the electron and lattice energy equations and assumes
that incident laser radiation is absorbed by both the electron gas and soli
d lattice to account for the thermal behaviour of semiconducting and impure
metals. A perturbation technique is utilized to eliminate the coupling bet
ween the electron and phonon energy equations when the normalized temperatu
re difference between electrons and phonons is a small quantity, which is t
rue in materials exhibit high coupling factors.