Method for obtaining information about a layer of an organic solderability preservative on a printed circuit board

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 (16) having a copper layer (18) covering a part of an area of the printed circuit board (16), wherein a solder resist (19) is placed on the copper layer (18), and the solder resist (19) has openings (21) wherein in the openings (21) a copper surface of the copper layer (18) is covered by a layer of an organic solderability preservative with an individual thickness (20), - Providing a fluorescence measuring system (10), comprising a radiation source (11) suitable for emitting a radiation beam (22), a detection unit (12) for detecting fluorescent radiation (23), and a movement device (24) which is arranged to move the radiation source (11) and the printed circuit board (16) relatively to each other in at least one dimension, the method comprising following steps (a) Obtaining (S2) information about the location of the opening