Process for manufacturing printed circuit boards with protected spaces between tracks

It comprises the steps of: a) arranging a dielectric substrate ( 1 ) with at least one conducting plate ( 2 ) joined by an adhesive ( 8 ) to at least one of its sides; b) removing areas of said plate ( 2 ) by selective chemical milling to provide conducting tracks ( 5 ) joined to the substrate ( 1 ) and separated by spaces between tracks ( 6 ); c) applying and hardening by radiation an electroinsulating filler material ( 7 ) to fill said spaces between tracks ( 6 ), covering the tracks ( 5 ); d) applying an abrasion treatment to obtain flush upper surfaces ( 3 ) of the filler material ( 7 ) and of the tracks; and e) cooling, after step c) and during step d), the printed circuit board to reduce the temperature of the filler material ( 7 ) to under its glass transition temperature.