Impact reliability analysis of a rigid-flex PCB system under acceleration loads

The dynamic response of a microsystem based on rigid-flex printed circuit board (rigid-flex PCB) with three layers of rigid circuit boards connected by flexible circuits was investigated, and the impact reliability of the ball grid array (BGA) solders and redistribution layer (RDL) were determined. A finite element model (FEM) was established. The epoxy fill was considered a viscoelastic material and was modeled by the Prony series, and the BGA solders were modeled with the Johnson-Cook model. Horizontal acceleration and vertical acceleration with a maximum amplitude of 15,000 g were used as impact loads. The results showed that the system sustained far less stress under vertical acceleration than under horizontal acceleration, and the stress distribution was related to the stiffness distribution. Under horizontal acceleration, the system sustained both shear and compressive deformation, whereas only compressive deformation occurred under vertical acceleration. A sudden spatial change in the stiffness caused higher stress of the BGA and RDL under vertical acceleration.