Quantum dot Cellular Automata (QCA) is amongst promising new computing scheme in the nano-scale regimes. As an emerging technology, QCA relies on radically different operations in its devices; for example, the logic values are represented by the position of electrons inside QCA cells rather than voltage levels, and the basic logic block of QCA is the majority voter. In this paper, we present the impact of scaling on defects that may arise in the manufacturing of QCA devices. This study shows how the sensitivity to manufacturing processing variations changes with device scaling. Scaling in QCA technology is related to cell dimension/size and cell-to-cell spacing within a Cartesian layout. Extensive simulation results on scaling of QCA devices, such as the majority voter, the inverter and the binary wire, are provided to show that defects have definitive trends in their behavior. These trends relate cell size (l) to the smallest cell-to-cell spacing (d) for erroneous behavior in the presence of different defects (such as misalignment and displacement); their impact on the correct functionality of QCA devices is extensively discussed. It is shown that in most defect cases the scaling relationship between l and d is linear, albeit with different slopes.