Investigating the Component Shift during Reflow Soldering at Large Scale Capacitors

Component shift or component skewing is a well-known failure for large scale surface mounted (SM) components. The purpose of this paper was to investigate this phenomenon for large scale SMD capacitors with a size of 10 × 9 × 5.5 (lwh) mm. For the investigations, the forces acting on the component were calculated, which included the force due to the surface tension and due to the hydrostatic pressure of the molten solder, the mass of the component and the forces due to the friction. For calculating the forces due to the surface tension and due to the hydrostatic pressure, the shape of the solder fillet was predicted by a geometrical approach. The frictional forces were considered for three boundary conditions as; two states of the solder as being in molten state (viscosity of the molten solder) or in paste form, and besides for the two states of the paste as being fresh (force due to viscosity) or dried out (frictional forces). The non-Newtonian viscosity of the solder pastes was addressed by the Carreau-Yasuda rheological model. Results showed that this type of components can shift even 1 mm in less than 200 ms during the reflow soldering, which may results in open joints and failed circuit. By the results of our analysis regarding the component shift during reflow soldering, the first pass yield of manufacturing, and the quality of assemblies could be enhanced significantly.