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The interfacial reaction between pure Sn and different metallizations of Cu, Ag, Ni and Co, as well as the melting/solidification characteristics of each reaction system were investigated using a differential scanning calorimeter (DSC). Results show that there exists the early interfacial eutectic reaction in Sn/Cu and Sn/Ag systems, which leads to the occurrence of the Sn melting at the interface...
TEM (transmission electron microscope) observations and precise SAED (selected area electron diffraction) analysis were used to character the growth of IMCs (intermetallic compounds) between eutectic SnBi solder and Cu(111) substrate after reflowing. The results indicated that after reflowing the interface between eutectic SnBi solder and Cu(111) substrate is made up by four groups of neighboring...
The results of lifetime testing of Cu/Sn-Cu eutectic bonded dice at 10μm pitch in large area arrays of 325,632 interconnects are shown. The interconnect bonding process (pressure and temperature) required for the formation of low resistance (~100 mΩ), high yielding (99.99% individual bond yield), and reliable interconnects is described. The effects of thermal cycling on electrical yield and resistance...
Recently, the Au/Pd/Ni(P) tri-layer has become one of the promising replacements for the Au/Ni(P) surface finish in array-array packaging applications. The key motivation for this developed trend is the additional Pd layer can prevent the Ni(P) from the galvanic hyper-corrosion that has long been recognized to be the root cause of ??black pads??. In the present study, the solderability of the Au/Pd/Ni(P)...
The microstructure of the eutectic SnBi/Cu interface was investigated by transmission electron microscopy (TEM). In-situ and ex-situ thermal aging were conducted to study the nucleation and growth of Cu3Sn and Cu6Sn5 on both polycrystalline and single crystalline Cu substrates. The growth kinetic analysis showed that although the growth of total IMCs (Cu3Sn + Cu6Sn5) was similar on single and polycrystalline...
Eutectic Sn-Cu alloy is one of the lead-free solder candidates for electronics interconnection. The methanesulphonic acid based baths were investigated for the electrodeposition of Sn-Cu alloys. The effect of iso-octyl phenoxy polyethoxy ethanol (Triton X-100) as a surfactant was studied, its addition proved to facilitate achieving the near eutectic composition of Sn-Cu alloy with improved microstructure...
For the past several years, the semiconductor industry has been responding to the RoHS directive to eliminate certain hazardous substances from electronic components. One of the areas where work is still ongoing to comply is in the area of flip chip interconnects. Currently, leaded flip chip interconnects are allowed under an exemption in the RoHS directive due to a perceived lack of a technically...
It is well known that Ni and its alloys possess a lower reaction rate with Sn than Cu and Cu alloys. Therefore Ni-based under bump metallization have attracted attention in recent years. In this study, the diffusion-controlled reaction between eutectic Sn-3.5Ag flip chip solder joints between electroplated-Ni (EP-Ni) and electroless-Ni (EL-Ni) has been investigated. Morphology and growth kinetics...
Transmission electron microscopy (TEM) observations were carried out to investigate the microstructural evolution of SnBi/single crystal (100) Cu interface during reflow and solid-state aging process. It was found that there were two kinds of IMCs, Cu6Sn5 and Cu3Sn, at the interface after reflow. The Cu3Sn grains grew along [100] direction of Cu with columnar morphology. During aging, new triangle...
The microstructures of SnBi/Cu interconnect after reflow and its evolution during solid-state aging at 393 K were investigated using transmission electron microscopy (TEM). It was found that after reflow there were two kinds of intermetallic compounds (IMCs) - Cu6Sn5 and Cu3Sn in solder joint. Above these IMC layers there was a Bi-rich layer which consisted of discontinuous Bi particles. During solid...
Cu pillar bumps with eutectic SnPb solder were annealed and their microstructures were investigated. Linear relationship was observed between thickness of intermetallic compounds (IMCs: Cu6Sn5, Cu3Sn) and square root of time at 120 and 150degC. Kirkendall voids, formed by the diffusivity differences between Cu and Sn, were observed near the interface between Cu and Cu3Sn. There was a change in slope...
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