Printed In this work, a finite element

Printed
Circuit Board (PCB) are used in most
electronic products to mechanically support and electrically connect chips,
capacitors, resistors, or other electronic components via soldered
joints. During utilisation, these products will experience loading
environments that include vibration loading and thermal loading that is why it
is necessary to determine the structural integrity of the PCB and its
components due to these loads. PCB is exposed to
combined loading such as vibration and thermal and it is well known that solder
is the most critical part of the assembly as it assure the interconnection
between the card and the component.    

Several work has been
established in order to study the dynamic behavior of an electronic component
under vibration load. Grieu (Grieu et al.
2008) presented a methodology to calculate the damage of solder joint under
random vibration. In addition, he used FEM to calculate the lifetime of electronic
components under random loadings. Mattila (Mattila et al. 2008) carry out experimental
tests of temperature and harmonic vibration to study the effect of different
temperatures (25°C, 70°C and 110°C) on solder joint reliability. The maximum
strain on the PCB was increased with temperature rise. Delmonte et al (Delmonte et al. 2013) developed a thermomechanical
model to predict the fatigue life of the solder joints. He presented an
approach to determine strain using Coffin-Masson equation. Zhang (Zhang et al. 2015) conducted tests in order to
investigate the effect of temperature (25 °C, 65 °C and 105 °C) on PCB
frequency and strain; moreover, he studied the reliability of solder joints
under vibrating loading.

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In this work, a finite
element model of PCB and component assembly is presented in order to
investigate the effect of combined load on PCB response: dynamic thermal mechanical
loading.COMSOL
Multiphysics finite element model is used to study the stress-displacement and
thermal analysis of the solder balls on the Plastic Ball Grid Array (PBGA)
component (Fig. 1). The PCB is made of two layers: FR4 of 12mm length, 1.23mm
thickness and Cooper with the same length and 0.07mm thickness. The Component of
2 mm × 0.5 mm is
mounted with 0.76 mm diameter solder balls under 0.48 mm pitch and it is
situated in a distance of 5 mm from each face. The boundary conditions for one
of the opposite faces of PCB are set as clamped and the other face is free. The
material properties of the FR4, Cooper, Solder ball and component are listed in
Table 1. In this numerical simulation, the density of mesh will have an impact
on the predicted results. For this reason, mesh is refined in the solder ball
as represented in Fig. 2.In this study, the response of the component
under harmonic excitation is investigated using the FEM model described in Section
2. The harmonic excitation force (Eq. 1) is applied in the longitudinal direction
(Y) on the free edge. The natural frequencies and their modes are calculated using
the proposed model (see Table 2).

Cinar
et al. 2012 showed
that the first natural frequency is the most destructive mode, forced vibration
analysis was performed around the first natural frequency. Fig. 6 and Fig. 7 show
the peak of stress, deformation at a point between the solder joint and the
component in the frequency (f) is range of 5.4-5.5 kHz.