Shahrum Abdullah

Subsurface Deformation of Worn Al-Cu and Al-Mg Alloys

This paper investigates the subsurface deformation of two types of aluminium alloys with differing nature; A2124 (precipitation-hardened) and A5056 (work-hardened), sliding against an M2 tool steel slider. With block-on-ring configuration, the wear test was carried out at different loads ranging from 23 - 140N, in a dry sliding condition. Detailed secondary electron microscopy (SEM) performed on the longitudinal cross sections of the worn alloys indicates that the subsurface deformed layer beneath the worn surfaces is composed of a number of distinct layers like the mechanically mixed layer (MML), the shear deformed and bulk layers with increased hardness as the surface was approached. Deformation below the MML followed the expected behaviour of an exponential decay of strain with depth. In contrast to other studies in the literature, a linear relationship between depth of deformation and specific wear rate was not found for both alloys. This was believed to a result of the MML, which occupied a great proportion of the total depth of deformation. The relationship between the characteristics of the MMLs especially on the work hardening as a function of alloy type is also discussed.

Dicing Laminated Wafer for QFN 3D Stacked Die Packaging

Nowadays, die attach film (DAF) gaining popularity in microelectronic packaging as integral part in facilitating the growth of wafer level packaging and stacked die packaging. DAF applied to the backside of wafers prior to saw have many advantages, such as the elimination of the epoxy dispensed process step and the reduction of epoxy related failure mode. However, the dicing process for DAF wafer usually associated with sidewall chipping, DAF whiskering and crack that will affect reliability of Quad Flat Non-Leaded (QFN) stacked die. Blade properties and characteristics are the crucial factor in analyzing the DAF dicing results. In this paper, we evaluate the blade characteristics before and after DAF wafer dicing process for our stacked die packaging. The qualitative measure by means of the Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) analysis were performed in order to understand the lamination and dulling effect on blade surface. The obtained results showed that sawing polymeric material such as wafer laminated with DAF induces lamination of polymeric material onto the blade surface and reduce blade cutting edge. As a result, reduce the quality of DAF dicing process.