In polymers for microelectronics applications, moisture is known to have a deleterious effect upon device reliability. In this paper, the moisture transport behaviors of a newly developed family of all-aromatic and aromatic/aliphatic copolyester thermosetting films were described. The moisture uptake as a function of temperature, relative humidity, sample thickness, and processing conditions were presented via conjugate moisture sorption tests.(1) It was found that the post curing near but below T-g resulted in an increase in both total moisture uptake and diffusion coefficient due to the effect of physical aging and the generation of sample defect volume.