Porous polyimide (PI) is an advanced engineering material due to its excellent insulating and outstanding dielectric properties. These properties enable porous PI films for its potential application as inter level insulation material in next generation micro electronic devices. Development of Porous PI film (PPI) was initiated for use in sensing layer of relative humidity (RH) space sensor. In this study, a novel method is developed to achieve uniform pore size and the process is scalable. To achieve desirable porous film forming properties rheological studies of plain Polyamic acid and filled resins (with porogen) was carried out followed by experimental trials to validate film-forming properties. Suitable Porogen used in the realization of PPI, which can be easily dispersed in the Polyamic Acid (PAA) resin. Optimization of process parameters for realization of porous polyimide film (PPI) was carried out w.r.t mixing time, curing cycle, and chemical etching duration of porogen followed by heating to remove any traces of volatile impurity present in the pores. Developed porous polyimide film had uniform pore distribution with a pore size in the range of 0.5 to 8.5 µm, the dielectric constant is measured as 1.4 and the film is thermally stable up to 500 °C meeting all the requirements for use in space grade RH sensor. The rheological parameters, solid content, and other process variables were finely tuned to fulfill the scale-up demands for porous polyimide film production. As a result, a successful demonstration and characterization of porous polyimide film, with a batch size of 3m2, were achieved, marking a significant advancement not documented in previous literature.