The present invention provides low stress non-hermetic conformal coatings for the protection of microelectronic devices, such as a Microelectromechanical system (MEMS) based multichip module from adverse environments. The induced stress from these two coatings due to the thermal cycling and manufacture processing will not cause any influence on sensing accuracy of the piezopressure sensor or similar functional MEMS devices. Furthermore, the conformal coatings have the merits of low glass transition temperature, good elongation, low moisture uptake and mobile ion permeation, room temperature curability and good contamination resistance to the jet fume, which promise a high reliability for the aerospace and avionics application. One conformal coating comprises a composition/formulation containing a rubber, siloxane or urethane oligomer modified epoxy and an organic hardener, and optionally an organic diluent and a curing catalyst. Another conformal coating comprises a composition/formulation containing a silicone elastomer or gel and a metal chelate catalyst, and optionally a silica filler, a diluent and an adhesion promoter or coupling agent.