PSI - Issue 79

Giulia Morettini et al. / Procedia Structural Integrity 79 (2026) 440–448

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This behavior results in a combined bending and tensile stress on each terminal (Steinberg (2000), Al-Araji et al. (2020)), which can be schematically represented as shown in Fig. 2. The bending stress originates from the angular deformation that each lead must undergo relative to the PCB plane, while the normal component arises from the vertical variation of the relative distance between the component body and the board surface. 2.2. Stresses Induced by the Dynamic Coupling Between Component and PCB In addition to the cyclic stresses described above, an additional contribution arises from the intrinsic dynamics of the component system. The component mounted on the board can be modeled as a mass–spring–damper system, where the mass represents the component body, the stiffness is associated with the flexibility of the connection leads, and the damping corresponds to the dissipative effects of the material and the solder joints (Perkins and Sitaraman (2004)). When the system is excited by a vibrational input containing frequencies close to its natural resonance frequency, an amplification of displacements occurs along the vertical axis (x-direction), as schematically shown in Fig. 3. This amplification causes a relative oscillation between the component body and the PCB surface, resulting in an alternating tensile and compressive stress on the component leads.

Fig. 3. Schematic representation of the mass–spring–damper model of a mounted component and the amplification of relative displacements under resonant excitation

When these effects are superimposed, the component leads experience cyclic fatigue stresses concentrated near the solder joint, which acts as a stress concentration zone. These localized stresses are amplified, facilitating crack initiation. Over time, this process may evolve into complete fracture of the lead or the solder joint, leading to electrical disconnection and eventual component failure. Such behavior, confirmed by several experimental studies in the literature, highlights how the coupled dynamic response between the PCB and the component represents one of the most critical aspects in predicting the mechanical reliability of Through Hole components, particularly for radial-leaded devices. 3. The Workflow of the Proposed Approach As previously mentioned, the present approach is based on the assumption of preliminary knowledge of the physical and mechanical parameters of the bare PCB, such as Poisson’s ratio, Young’s modulus, and the material density, as well as of the boundary conditions that connect the board to the external environment (Bhavsar et al. (2014), Khandpur (2005)). The input loads are also known and are expressed in terms of the Power Spectral Density (PSD) of acceleration applied at the constraints and the duration of the excitation.