UCLA

The advanced packaging technology is a business of billions of dollars. The reliability issues of the packaging products are of keen interest. In the microelectronic industry, a major paradigm change from two-dimensional integrated circuit (2D-IC) to three-dimensional integrated circuit (3D-IC) is occurring. Electromigration (EM), referring to the atomic diffusion induced by a high electron current density, is one of the most serious reliability concerns of flip chip solder joints used in packaging technology. In the traditional study of the flip-chip solder joints by using two-dimensional (2D) examination procedure (e.g. Scanning Electron Microscopy), it has encountered two problems. One is the difficulty in uncovering the kinetics in the real test vehicle during EM, especially at the early stage, which requires a nondestructive monitoring. The other is that a 2D method would bring more uncertainties of the void growth measurement in a real three-dimensional (3D) structure. As a nondestructive 3D imaging technique, synchrotron radiation based x-rays tomography or laminography can bring significant evidence on the in-situ characterization of flip-chip solder joints or other 3D packaging parts during accelerated reliability tests, such as EM tests. We have conducted tomography experiments in Advanced Light Source, LBNL, USA to measure the effective charge number of eutectic SnPb solders accurately. Also we have conducted laminography imaging experiments at the beamline ID15A at ESRF, Grenoble, France to investigate the new mechanism of the EM induced failure in Pb-free solder joints. A proposed link between the physical and statistical analysis of the failure is outlined on the base of the 3D characterization, and offers as a rapid way to estimate the life time of the test vehicles.