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Different flip chip bump configurations are investigated in terms of their electromigration behavior. Standard SAC (SnAgCu) solder bumps with a Ni/Au finish on the chip side are compared with Cu pillar bumps soldered with a thin layer of SnAg alloy. The substrate finish is identical for both cases and consists of a 17μm thick Cu layer. Depending on the current direction, different interfaces are stressed...
Two different flip chip bump configurations have been investigated in terms of their thermo-mechanical, electromigration and fusing behaviour. Standard SAC (SnAgCu) solder bumps with a Ni/Au finish on the chip side are compared with Cu pillar bumps soldered with a thin layer of SnAg alloy. For the test structure, the flip chip assembly is integrated in a BGA package. Finite Element Modelling is used...
Compared with widely used SAC305 (Sn-3.0Ag-0.5Cu) solder, low-Ag (Ag ≤ 1%) SAC solder obviously shows advantages in cost and mechanical impact resistance, and disadvantages in worse wettability, higher melting point and degeneration in electromigration, which restrict its application. Therefore, adding some suitable elements to the solder to improve the solderability and mechanical performance is...
Improving the toughness against impact of an electrolytically plated (Ni/Au) Sn-3 mass%Ag-0.5 mass%Cu solder joint for a ball grid array package was examined. The concentration of impurities (C, O, S, and Cl) that reduce the toughness against impact of Ni plating is shown to be inversely proportional to the rate of Ni deposition. The constant of proportionality becomes the rate of adsorption of impurities...
Wide bandgap materials have become very attractive for power electronics due to their physical properties that allow junction temperatures up to a theoretical limit of 600°C. In contrast, the maximum operation temperature of conventional silicon semiconductors is limited to approximately 200°C. The high-temperature operation of wide bandgap switches allows an increasing power density of power converters...
NEMI recommended Sn3.9Ag0.6Cu to replace the eutectic SnPb solder, but solder joints of this alloy have poor performance in reliability tests of electronic packages, especially the board level drop test. In this paper, the effect of Cu content in solder is studied on the interfacial reliability of SnAgCu solder joints on the Ni/Au plated pads. After preconditioning (three reflows post package assembly),...
This paper presents a systematic failure analysis approach on a field return Ball Grid Array (BGA) solder joint crack. The lead free BGA solder ball sits on Au/ Ni metallization with Sn-37.5Pb solder paste. The field return component exhibits no form of mechanical induced damage and destructive analysis showed a brittle fracture mechanism at the intermetallic compound (IMC) interface and a thicker...
Electrolessly plated Ni-P has been extensively studied due to its high coating uniformity, selectivity and low coating stress. However, the use of lead-free solders accelerates interfacial reaction because they have higher melting points and higher Sn content than the conventional Pb-Sn solders. In this work, we developed a ternary electroless Ni-Sn-P (6~7 wt.% of P and 15~17 wt.% of Sn) alloy to...
SnCu2-4Ni1-2 as a lead-free solder was prepared from both sulfate and chloride plating solutions by galvanostatic electrodeposition. Current-potential polarizations for both plating baths were obtained with their respective deposition rates measured. Characterizations including SEM, EDX, and XRD were carried out to obtain relevant materials properties.
In this paper, the reaction couples were prepared to investigate the interaction between Sn and Cu substrate with various surface finishes. The studied interfacial systems contain Sn/Ni/Ag/Cu, Sn/Ag/Cu and Sn/Cu/Ag/Cu. The corresponding surface finish, Ag or Ni layer, is about 1~2μM. In the Sn/Ni/Ag/Cu reaction, the formed phase was Ni3Sn4 at first, indicating that Sn reacted with Ni at the Sn/Ni...
In this study, we would analyzed the solid state reaction between Sn2.5Ag solder bump and Cu/Ni under-bump-metallization (UBM). After 150°C thermal aging, we observed that the intermetallic compounds (IMCs) at chip side and interposer side both were Ni3Sn4 IMCs. It indicated that the solder did not react with Cu and the Cu layer was completed. As thermal aging time increased, the thickness of Ni3Sn...
In this work, IMC (Inter metallic compound) of lead free (Sn-Ag-Cu (SAC)) and lead (62Sn-36Pb-2Ag (SP)) solder joint on the four kinds of surface finished of ball grid array (BGA) pad, such as Immersion Tin (ImSn), Organic solderability preservatives (OSPs), Ni-P/Pd/Au (ENEPIG), and Ni-P/Au (ENIG) were investigated by Focus Ion Beam microscope (FIB). Sample after failure ageing conditions (Baking...
Because of the relatively low reactivity with solders, Ni-based materials are the most commonly used diffusion barrier layer materials in flip chip packaging technology for Al metallization integrated circuits. However, due to the high diffusivity of Cu, the diffusion barrier materials need to be re-evaluated for Cu/low k integrated circuits. Some literatures had indicated that Co is with superior...
The isothermal section of the Sn-Sb-Ni ternary system at 270°C is experimentally determined in this study. Sn-Sb and Sn-Sb-based alloys are viable high-temperature Pb-free solders, and Ni is the most frequently encountered surface finish in microelectronic industry. Sn-Sb/Ni is an important contact in using high temperature solders. Thus, phase equilibria information of the Sn-Sb-Ni ternary system...
This study was conducted to the Ni and Cu dissolution behaviors, and the cross-interaction during Ni/Sn3.5Ag/Cu joints fabrication. To form such joint structure, two common soldering sequences were employed: an as-reflow Cu/Sn3.5Ag solder bump jointed to Ni (Seq. I), and an as-reflow Ni/Sn3.5Ag solder bump jointed to Cu (Seq. II). The research results revealed that a ternary compound, (Cu, Ni)6Sn5...
In this study, the assembly processes and reliability performance of interconnects with 30 μm pitch Cu/Ni/SnAg joints are evaluated, Plasma was treated on the both upper and lower chips before bonding, then fine gap control bonding process was applied to minimize the solder squeezing phenomenon which causes the adjacent joints bridged. Two kinds of underfills were used to fill the gap of around 20...
Since 3D-IC becomes popular nowadays, solder micro-bumps plays an important role to develop TSV technology. This study verifies solder micro-bump efficiency via cracking as index. The micro-bump cracking is observed at the interface of intermetallic compound (IMC) layer after Si chip and Si carrier bonding. It was found that P-rich Ni layer will perform weaker and brittle solder joint by means of...
A Cu/Ni UBM and Sn-2.5Ag lead-free solder for 20 μm pitch micro-bump was successfully fabricated via consecutive electroplatings of Cu, Ni, and binary SnAg. Materials characterizations such as Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe Micro-analyzer (EPMA), and X-ay Photoelectron Spectroscopy (XPS) were carried out to obtain relevant materials properties. We observed...
The texture as well as epitaxial growth of intermetallic compounds (IMCs) are becoming important issues, due to increases in IMCs-solder ratios in the development of micro-bumping. (Cu, Ni)6Sn5 formed on Ni substrate didn't simply grow in an unexpected manner, but did so, producing a spectacular morphology. Even in the presence of very few Ni atoms dissolved in (Cu, Ni)6Sn5, a strongly preferential...
The Ni/95Pb5Sn/Cu ternary diffusion couples were used to investigate the cross-interaction between Ni and Cu across a layer of 95Pb5Sn solder. High-lead solder layers with thickness of 100 or 400 μm was electroplated over Cu foils. A pure Ni layer (20 μm) was then deposited over the as-deposited high-lead solder surface. The diffusion couples were then aged at 150 to 250°C for different periods of...
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