Finally, the last remaining solder interface – the chip solder layer – can be replaced by an Ag diffusion sinter technology.
The presence of a thin nanometric η-Cu6Sn5 phase layer at the Cu/liquid eutectic Sn-0.7 wt%Cu solder interface in absence of the ε-Cu3Sn phase is demonstrated experimentally for the first time.
The principal aim of this work is to determine experimentally and unambiguously the sequence of phase formation at Cu/liquid solder interface, i.e., to determine which of the two thermodynamically stable intermetallics η-Cu6Sn5 or ε-Cu3Sn forms and grows first at this interface.
The characterizations of samples by a high-resolution scanning electron microscopy and transmission electron microscopy clearly demonstrate that the only phase that forms and grows at the Cu/liquid solder interface, for contact times less than about 65 ms, is the η-Cu6Sn5 phase.
Stop feeding the solder interface is filled.
While the brittle fracture occurred in big solder joints and the fracture positions were at the areas close to the soldering interface.
This is because in order to capture the slightest geometrical difference on the order of a few microns between the two designs, the multiple-layer solder-die interface needs to be modeled using extremely fine mesh, while the overall dimensions of the package and the test board are on the order of millimeters.
Experiments were performed to illustrate the position of the BGA solder joint crack interface caused by tensile stress.
Scattering of tension values can be explained by scattering in the failure mode, while no adhesive failure of the solder mask/epoxy adhesive interface occurred in the SM-BM or in the SM-Cu configuration.
The conventional packaging structures, in which the Cu-based MCHS is bonded to the direct bond copper by solder or thermal interface material, are investigated to compare with the proposed structure.
