Modelling the lifetime of aluminum heavy wire bond joints with a crack propagation law

Abstract

In this study, an approach for enhanced lifetime modelling of wire bonds has been investigated. Numerical simulations of a 3D wire bond model have been used to acquire a suitable damage parameter. For the lifetime model, a modified Paris law for calculating crack growth per cycle has been employed, to consider the gradual area degradation due to thermo-mechanical loads. With the knowledge of the crack propagation rates, the acquired lifetime model can easily be transferred to different wire bond geometries without repeating the experiments necessary to fit the crack growth parameters

New model of crack propagation of aluminium wire bonds in IGBT power modules under low temperature variations

“…As the crack length increases, the stress required to induce further crack in the remaining bond length is reduced. This trend is consistent with the findings in [20], it was reported a similar pattern in their experiments. It is also similar to the reduction in bond shear strength that occurs with increasing crack growth, as reported in [21].…”

“…Also, the plastic strain evolution with cycling could be taken into account. This approach has been proposed in [16] and [17] to determine the lifetime of aluminum heavy wire bond joints.…”

A geometry-independent lifetime modelling method for aluminum heavy wire bond joints

“…The damage parameter L1C:pl has been evaluated in an area close to the crack front, which was found to be mesh-independent [6].…”

“…also [9] ), where the wire is not heated significantly by currents of 5 A to 7 A and the substrate deformation is negligible. The crack is implemented as in [6] as a cut of 2 flm height 5 flm above the actual interface chip to wire. But here, the wedge is a simplified, quarter-symmetric extruded geometry for easier handling and meshing as well as faster calculation.…”

“…In [6], instead of Coffin-Manson, a modified Paris law has been investigated considering the fatigue crack, that propagates through the 'interface area' about 10 flm above the chip metallization, eq. (2): (2) dAldN describes the growth of the crack area with increasing number of cyclic loads.…”