DMD Based Microscopic Fringe Projection Profilometry of Copper-Clad Substrates

The shape of a PCB surface, i.e., its topography, influences many functional properties of the designed circuit. In this paper, we propose the utilization of a non-contact, non-invasive, and non-destructive simplified microscopic fringe projection technique for the surface profiling of copper-clad PCBs. Here, a digital micromirror device (DMD) is used to project a high spatial fringe density at the surface of copper-clad PCBs to achieve high-speed profilometry, which can avoid disturbance due to in-field vibrations. Furthermore, the optimal spatial frequency of 70 mu m pitch is selected empirically to minimize phase error by comparing the sample's surface phase map at different spatial frequencies. The experimentally calculated average height using optimal spatial frequency for the central portion of the antenna's surface is found to be 13.46 mu m, and it is well in coordination with the height of 14.72 mu m obtained using a standard roughness tester. The qualitative and quantitative experimental results verified the practical applicability of the fringe projection system for measuring the surface profiling of copper-clad PCB.