Abstract: The effect of wafer-level solder bump size on solder bump shear strength and intermetallic growth as a function of time, at different storage temperatures is studied, using solder bumps of two different heights: 95 mum (SB95) and 142 mum (SB142). Smaller solder bumps (SB95) lead to a faster decrease in bump shear strength. Increasing aging temperature and time brings about an increase in the final fracture area of the solder, from a ductile to a quasi-brittle failure mode. It is observed that the smaller solder bump (SB95) exhibits a faster rate of increase in final fracture area, than the bigger bump. A linear decrease of solder bump shear strength with intermetallic thickness is established for the systems studied. Degradation of solder bump shear strength is found to be affected by the relative volume of the solder bump with respect to Ni/Au, such that a lower solder bump to Ni/Au volume ratio leads to faster shear strength degradation, due to the consumption of Cu in the bulk solder bump and the formation of brittle intermetallics. The overall intermetallic growth activation energies for the two solder bump sizes are found to be comparable, at 0.85- 0.86 eV. For this study, (Cu,Ni)6 Sn5, is initially formed, at the solder bump-to-under bump metallization (UBM) interface, followed by the formation of (Ni,Cu)3 Sn4, between the UBM and the (Cu,Ni)6 Sn5 intermetallic layer.
Abstract: We present a detailed experimental characterization of a confocal microscope readout system in a photochromic polymer under two-photon excitation. In particular, the effect of writing power, exposure time and recording depth on the contrast of the readout signal is explored. The reflected intensity of the recorded data bits is shown to be strongly dependent on the intensity of the writing laser and exposure time. The relative intensity initially shows an I2 dependence on power, followed by saturation. The saturation effect is also evident as exposure time is varied. These saturation features allow for reading of the stored bits with objectives whose numerical aperture is less than that used for writing (1.4 N.A.). Furthermore, a decrease in contrast is observed with an increase in layer depth.
Abstract: We observe a saturable change in the refractive index induced by two-photon absorption in a photochromic polymer, while the erasable nature of the polymer is maintained. As a result, the support region of spatial frequencies of the recorded data bits caused by the refractive index change in the polymer is enlarged. This feature leads to the significant enhancement of the signal level in a reflection confocal microscope readout system for three-dimensional photochromic bit optical data storage.
Abstract: Pulsed laser deposition (PLD) technique was demonstrated for the deposition of titanium nitride (TiN) thin films on Si (100) substrates. A 1064 nm pulsed Nd-YAG laser is focused on a titanium (99.5%) target in a nitrogen environment to generate the atomic flux needed for the film deposition. Spectroscopic analysis of the plasma emission indicates the presence of atomic titanium and nitrogen, which are the precursors of TiN. Images of the films grown at different laser pulse energies show an increase in the number and size of deposited droplets and clusters with increasing laser pulse energy. A decrease in cluster and droplet size is also observed, with an increase in substrate temperature. EDS data show an increase in the titanium peak relative to the silicon as the ambient nitrogen pressure is decreased. An increase in deposition time was found to result in large clusters and irregularly shaped structures on the substrate. Post-deposition annealing of the samples enhanced the crystallinity of the film.
Abstract: The present invention relates to A package (50,70) for a microelectronic component, comprising: a carrier element (12) having a first side (16) that comprises conductor lines (14); --a microelectronic component (20) having a first surface (24) and a second surface (23) facing away from the first surface; the microelectronic component with said second surface mounted on said first side and connected to the conductor lines via bonding wires (28); a polymeric encapsulation material (30) encapsulating the bonding wires and exposing a central zone (40) of said first surface (24), the encapsulation material comprising an outer edge (36) at said first side and an inner edge (38) at said first surface; a dam (42,44) abutting to the encapsulation material; wherein the dam (44) comprises a step-shaped surface transition (46) at said first side (16), the surface transition abutting on said outer edge (36). The dam (44) influences the forming of the outer (36) and the inner edge (38) during manufacturing the encapsulation material (30) and enlarges the area of the central zone (40). The present invention also relates to a method of manufacturing such a package for a microelectronic component.
