text: the present invention is based on the fact that the sensitizer contains a noble metal salt as well as a chromium ( iii ) complex compound in which the ligands , once they are exposed to light of a suitable wavelength , have a reducing effect on chromium having the oxidation number three . the chromium with oxidation number two produced during the exposure then has a direct reducing effect on the noble metal ions contained in the noble metal salt , resulting in the formation of noble metal nuclei which are required for the subsequent metallization without external current . the chromium ( iii ) ion contained in the unexposed sensitizer has an high chemical stability . thus , chromium ( ii ) in aqueous solutions oxidizes to chromium ( iii ) in the oxygen of the air . even if air is excluded , oxidation to chromium ( iii ) takes place in that water is reduced by releasing hydrogen . in preferred embodiments the noble metal salt contains at least one metal selected from gold , iridium , osmium , palladium , platinum , rhodium , ruthenium and silver . thus , in the unexposed sensitizer , chromium will be present exclusively with the oxidation number + 3 . the result is an excellent long term stability of such solutions . the absence of chromium of oxidation state + 2 in the unexposed sensitizer is particularly important since chromium ( ii ) would lead to undesired nucleation , as described above , and could thus be the cause for undesired metallizing or for the destruction of the metallization baths operating without external current . the unexposed sensitizer , in the preferred embodiments , has a chromium ( iii ) ion / noble metal mole ratio in a range from 10 : 1 to 1 : 10 . the activation energy required for the above described redox reactions must be supplied by radiation having wavelengths of less than 400 nm , preferably by uv radiation . longer - wave radiation is insufficient for activation . it is also undesirable because in it the influence of natural light would make handling difficult . for an absorption maximum at a radiation wavelength between 250 and 260 nm , a preferred embodiment of the invention employs a trioxalate chromate ( iii )- palladium ( ii ) chloride sensitizer . the stated absorption maximum permits the use of monochromatic coherent uv laser light for illumination . the advantage of laser light is its high energy density and the possible contact free image transfer from the master to the substrate surface without noticeable scattering effects . moreover , many mercury vapor lamps exhibit emission maxima in this wavelength range . by combining chromium in oxidation stage iii with a noble metal salt , the formation of stable noble metal nuclei directly after exposure to light becomes possible . this formation of metal nuclei can be enhanced by contact with a further solution of noble metal salts . if the light intensity is weak , a maturing process makes enlargement of the nuclei possible . in the subsequently used chemical metallization baths the resulting metallic nucleation layer need then only be reinforced to the intended layer thickness . the present invention will now be described in greater detail by way of the following examples . circuit board substrate material , e . g . a glass fiber reinforced epoxy resin plate , is cleaned in a known manner and etched . for cleaning , water and organic solvents such as propanol - 2 are used ; for etching , a commercial chromic acid bath is taken . sensitization to uv light is effected by immersion into a sensitizer solution proudced in the following manner , particularly in dependence on the substrate material employed and on its pretreatment : 1 to 10 g sodium oxalate and 1 to 18 g chromium ( iii ) chloride are dissolved in 500 ml demineralized water . added to this is 500 ml of an aqueous solution of 0 . 1 to 2 g / l palladium ( ii ) chloride , mixed with 1 to 100 ml / l 37 % hydrochloric acid and 100 to 800 mg / l wetting agent . when the mixture has taken on a reddish hue , it can be used . then the coated substrate is dried . the temperature at which the sensitizer solution is applied to the substrate is 25 ° c . the possible range of temperatures is 1 ° c . to 50 ° c . the temperature at which the coated substrate is dried was 50 ° c . a possible range is 40 ° c . to 120 ° c . the required time is always 5 minutes . the wetting agent was sodium - dodecyl - sulfate . the sensitized substrate material is exposed to uv light from a mercury vapor high pressure lamp through a negative mask containing the conductor pattern to be produced . here already an image of the conductor pattern can be recognized . this pattern is treated with an aqueous solution containing 0 . 1 to 0 . 9 g palladium ( ii ) chloride , 1 to 100 ml 37 % hydrochloric acid and 10 to 200 mg of a wetting agent per liter of solution . then selective chemical metallization is performed in a presently commercially available copper bath which operates without external current until the desired conductor thickness has been obtained . corresponding to example 1 , only that a focused uv laser beam having a wavelength between 250 and 260 nm is used for the exposure . the beam is spatially deflectable and its intensity can be modulated . the associated controls and / or regulation are performed by means of a data processing system in which is stored the conductor pattern ( surface pattern ) to be produced . as an alternative to the deflectable laser beam , it is possible to keep the beam stationary and move the base material ( substrate ) to be exposed , e . g . with the aid of a mechanical stage controlled by the data processing system in accordance with the pattern to be produced . thus , in each case , exposure is limited to the surface regions which , are to be provided with conductive material . for radiation exposure the second harmonic generation of the 514 . 5 nm emission of argon ion gas laser is used . the output intensity was 30 mw . the translation speed of the laser beam was 1 m / min . corresponding to example 1 , except that initially the unexposed sensitizer solution is applied spatially selectively to the circuit board base material ( substrate ) according to the surface pattern ( conductor pattern ) to be produced . the thus coated substrate is then exposed essentially over its entire surface area to uv light having a wavelength range from 250 nm to 260 nm and is treated further according to example 1 . spatially selective coating can be effected in many ways , for example with the aid of a hand - guided brush and / or an ink writing implement filled with sensitizer solution . aditionally it is possible to fasten a suitably configured writing implement filled with sensitizer solution to the so - called plotter of a data processing system and to coat the substrate in that way according to the pattern to be produced . the light source can then be almost any uv source which radiates over a large area , e . g . a household sun lamp . such a process is particularly suitable for the cost - effective production of small series and / or test patterns . an exposure mask suitable for uv light and / or focused uv light are avoided . the exposure time was 1 minute , the light intensity was 0 . 5 w / cm 2 . the same as example 1 only that a mixture of sodium trioxalate chromate ( iii ), palladium ( ii ) chloride and polyvinyl alcohol are used for the sensitization . so 1 to 10 g sodium oxalate and 1 to 18 g chromium ( iii ) chloride are mixed with 500 ml polyvinylalcohol . added to this is 500 ml of a mixture of 0 . 1 g / l to 2 g / l palladium ( ii ) chloride and polyvinylalcohol . the same as example 1 only that a mixture of potassium trioxalate chromate ( iii ), gold ( iii ) chloride and pentaerythrite is used for the sensitization . so 1 to 10 g potassium oxalate and 1 to 18 g chromium ( iii ) chloride are dissolved in 500 ml demineralized water . added to this is 500 ml of an aqueous solution of 0 . 1 to 2 g / l gold ( iii ) chloride , mixed with 1 to 100 ml / l 37 % hydrochloric acid and 100 to 10 , 000 mg / l pentaerythrite . the same as example 1 only that a selective premetallization in a nickel - phosphorus alloying bath takes place before the thick copper plating . the alloying bath consists of a demineralized water solution having the following composition : and is adjusted to a ph of 9 with naoh . other noble metal salt - chromium ( iii )- complex compound mixtures to be suitable for use in the method according to the invention are : 1 to 10 g potassium oxalate , 1 to 18 g chromium ( iii ) chloride and platinum ( iv ) chloride , dissolved in 500 ml 5 % hydrochloric acid ; or 1 to 10 g sodium oxalate , 1 to 18 g chromium ( iii ) chloride and rhodium ( iii ) chloride , dissolved in 500 ml 5 % hydrochloric acid . it will be understood that the above description of the present invention is susceptible to various modifications , changes and adaptations , and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims .