A method for obtaining information about a layer of an organic solderability preservative on a printed circuit board, the method comprising - Providing or producing a printed circuit board having a copper layer covering a part of an area of the printed circuit board, wherein a solder resist is placed on the copper layer, and the solder resist has openings wherein in the openings a copper surface of the copper layer is covered by a layer of an organic solderability preservative with an individual thickness, - Providing a fluorescence measuring system, comprising a radiation source suitable for emitting a radiation beam, a detection unit for detecting fluorescent radiation, and a movement device which is arranged to move the radiation source and the printed circuit board relatively to each other in at least one dimension, the method comprising following steps a) Obtaining information about the location of the openings on the printed circuit board, b) Selecting at least one of the openings, thereby obtaining at least one selected opening, c) Moving the radiation source and the printed circuit board relatively to each other with the movement device and placing the radiation source at such position that the radiation beam irradiates into the at least one selected opening, and on the layer of the organic solderability preservative in the at least one selected opening, d) Detecting the fluorescent radiation which is emitted from the organic solderability preservative with the detection unit. wherein in step c) the radiation beam irradiates in such way that no solder resist is irradiated. - Providing or producing a printed circuit board having a copper layer covering a part of an area of the printed circuit board, wherein a solder resist is placed on the copper layer, and the solder resist has openings wherein in the openings a copper surface of the copper layer is covered by a layer of an organic solderability preservative with an individual thickness, - Providing a fluorescence measuring system, comprising a radiation source suitable for emitting a radiation beam, a detection unit for detecting fluorescent radiation, and a movement device which is arranged to move the radiation source and the printed circuit board relatively to each other in at least one dimension, the method comprising following steps a) Obtaining information about the location of the openings on the printed circuit board, b) Selecting at least one of the openings, thereby obtaining at least one selected opening, c) Moving the radiation source and the printed circuit board relatively to each other with the movement device and placing the radiation source at such position that the radiation beam irradiates into the at least one selected opening, and on the layer of the organic solderability preservative in the at least one selected opening, d) Detecting the fluorescent radiation which is emitted from the organic solderability preservative with the detection unit. wherein in step c) the radiation beam irradiates in such way that no solder resist is irradiated. a radiation source suitable for emitting a radiation beam, a detection unit for detecting fluorescent radiation, and a movement device which is arranged to move the radiation source and the printed circuit board relatively to each other in at least one dimension, a) Obtaining information about the location of the openings on the printed circuit board, b) Selecting at least one of the openings, thereby obtaining at least one selected opening, c) Moving the radiation source and the printed circuit board relatively to each other with the movement device and placing the radiation source at such position that the radiation beam irradiates into the at least one selected opening, and on the layer of the organic solderability preservative in the at least one selected opening, d) Detecting the fluorescent radiation which is emitted from the organic solderability preservative with the detection unit.