The Silicon Vertex Tracker (SVT) of the BaBar experiment at the PEP-II B-factory at SLAC plays a fundamental role for the CP-violation measurement. The SVT is made of five layers of double-sided silicon microstrip detectors covering the polar angles between 17.2° and 150° (in the ϒ(4S) center-of-mass reference frame this corresponds to −0.95<cosθ<0.87). Due to mechanical constraints, the strip signals must be brought to the readout electronics with flexible Upilex circuits (fanouts) where copper traces are deposited with a pitch of ≈50μm. We present here a detailed description of the mechanical and electric characteristics of these fanouts, with particular attention on the test system that has been designed in order to control the quality of the production.