NOVELTY - Fabrication of a composite material involves subjecting a skeleton of single fibers or fabric to de-oiling, pre-impregnation with silica gel solution, heating, impregnation with silica gel solution, heat treatment and metallization, to obtain a photo-etchable material used to produce conductive tracks allowing bonding to devices.    USE - Production of optical, optoelectronic and electronic devices.    ADVANTAGE - Improved cost-performance ratio; low density; high dimensional stability resulting from a coefficient of expansion of almost zero, and thus reduced need for thermal control and reduced susceptibility to thermal gradients; insensitivity to humidity; long-term stability especially between -50 degrees C and 400 degrees C, insensitivity to a number of chemical reagents; high rigidity and very good mechanical and thermal properties, absence of porosity and micro-cracks and therefore high stability in outer space; and good thermal conductivity.    DETAILED DESCRIPTION - Fabrication of a composite material comprising a skeleton of single fibers, particularly single fibers of carbon (preferred), silicon carbide, aluminum or their mixtures, or fabric produced from the fibers, embedded in a silica matrix comprises:    (a) de-oiling the skeleton by chemical treatment;    (b) pre-impregnation of the de-oiled skeleton with a de-aerated silica gel solution;    (c) heating the obtained prepreg at 180-200 degrees C, to reduce gaseous inclusions, preferably at a pressure of around 10 power 6 Pa of nitrogen;    (d) one or more successive impregnations of the heat-treated prepreg with a de-aerated silica gel solution, to fill interstices and remove surface porosity;    (e) thermal treatment at around 950 degrees C but less than the crystallization temperature of silica, to bring the silica to a vitreous condition; and    (f) metallizing the composite material preferably by physical vapor deposition or cathodic sputtering, to obtain a photo-etchable material used to produce conductive tracks allowing bonding to devices.    Between stages (c) and (d) there is an intermediate stage (c1) comprising assembly of the heat-treated prepreg with another heat-treated prepreg obtained in stage (c).    During stage (d) impregnation-free zones are produced. Between stages (d) and (e) there is an intermediate stage (d1) comprising bending the impregnated material obtained in stage (d) or assembling the impregnated material with another impregnated material obtained in stage (d) at the impregnation-free zone and applying a binder comprising silica gel on the impregnation-free zone, followed by thermal treatment of the bent or assembled impregnated materials in stage (e).    Following stage (e) there is an additional stage (f) of machining the thermally treated, impregnated material before the metallization stage (h).    The composite material obtained in stage (e) or (f) can be subjected to a supplementary stage (g) comprising coating the composite material with a finishing layer of preferably de-aerated, pure silica gel, followed by polishing to obtain a mirror surface before metallizing in stage (h).    The metallized material obtained in stage (h) can be coated with conductive or dielectric layers in order to provide particular optical or electrical properties.    INDEPENDENT CLAIMS are given for:    (i) a composite material obtained by the above-described process and whose partially metallized surface forms a connection pad for a component, a conductive track, a resistive track, a circuit or a microwave line;    (ii) an article formed from the composite material and comprising optical instrument structures, mirrors, thin- or thick-layered hybrid electronic circuits, passive and active antennae, ultrastable radiofrequency cavities, solar panels, telescope or focal plane structures, laser systems, heaters or sensors which are preferably electronic; and    (iii) use of the composite material to produce conductive tracks or surfaces for joining with devices.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic representation of the single fiber impregnation or pre-impregnation and winding the impregnated fibers onto a mandrel.    Single fibers (1)    Slip (2)    Mandrel (3)