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A two-dimensional analysis of the Charpy V-notch specimen subjected to impact loading, according to the standard DIN EN 10045-1, is carried out, using a transient explicit dynamic finite element program. An elastic-viscoplastic, temperature dependent, constitutive relation for a porous plastic solid based on the Gurson damage model is developed. Ductile fracture of the matrix material will be described by the nucleation and subsequent growth of voids to coalescence. An updated Lagrange–Jaumann formulation is employed accounting for large strain and rotation. The discretization is based on four-node plane strain solid elements with one Gauss point. The equations of motion are integrated numerically by an explicit integration algorithm utilising a lumped mass matrix. The predictions of the numerical analysis in terms of force deflection response, crack resistance behaviour and deformation energy absorbtion are compared with results from Charpy tests which were carried out according to the low-blow technique.
The finite element method was used to simulate the thermo-mechanical behaviour of a flip chip under thermocyclic loading between -55°C (-67°F) and 125°C (257°F). In order to simulate realistically the inelastic material response of the solder bump, Chaboche's viscoplastic material model instead of a classical ORNL-theory was implemented into the finite element code ABAQUS and applied to a flip chip configuration. This so-called unified constitutive model is able to describe the Bauschinger effect as well as the creep/plasticity interaction. Herewith the influence of the substrate material on the inelastic deformation behaviour of a tin-lead solder bump was analysed. A comparison is given with respect to the influence of the two substrate materials namely Al<sub>2</sub>O<sub>3 </sub> and our self-developed Low Temperature Co-fired Ceramics (LTCC) on the inelastic response of the Sn60Pb40 eutectic solder material. It may be shown that the thermoelastic behaviour of the LTCC substrate significantly reduces the cyclic stresses in the bump compared to Al<sub>2</sub>O<sub>3</sub> as well as the cumulative inelastic strain which is responsible for the development of damage and hence flip chip failure
The successive fatigue failure process, i.e. crack initiation and growth up to electrical failure, has been investigated for a flip chip configuration. A cracked and uncracked solder bump was analysed using an unified viscoplastic constitutive model (Chaboche). The electrical failure of a bump seems to be reached in general not before a deep crack has grown into the bump. In order to update the actual loading situation two different cracked structures were calculated.