The development of a new generation of innovative thermoplastics for microelectronic and photonic applications is essential to make cavity packages able to compete with ceramic packages in terms of cost and design flexibility. Among plastic materials, thermoplastic resins such as Liquid Crystal Polymers (LCP) offer attractive properties including low gas permeation, high temperature resistance, thermal stability and low dielectric constant (3.1 at 1 MHz and 2.8 at 10 GHz). However LCP present anisotropic mechanical properties (Young’s modulus, CTE, …) due to the straight rigid molecular chains oriented parallel to the molding direction during processing. The difference of properties between the molding direction (MD) and the transverse direction (TD) of injection could induce a potential fragility of the material and then a lack of reliability of the package. In the present study, silica nanoparticles are introduced into the LCP matrix to reduce the anisotropy factor. The mineral fillers have been functionalized by sol-gel method using various chemical functions. The impact of the functionalization on the anisotropy factor is studied. Results show a significant change in mechanical properties in both directions as well as reduced anisotropy factor. The anisotropy factor (EMD/ETD) decreases significantly of about 25% with the addition of the functionalized particles.