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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...
Packaging engineers, in the search for the perfect packaging technology, are turning to three-dimensional packaging technologies that stack multiple dies/chips within a single package. Prevailing problems with stacked dies and clips are the tilting of the chips or clips due to the unbalanced bond line thickness of different solder attachments at different height levels or unbalanced weight distribution...
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),...
In this study, varying amounts of Ni-CNTs were incorporated into the Sn-Ag-Cu matrix to form the composite solders. The interfacial intermetallic thickness formed on the Ni/Au metallized Cu substrate was determined under the as-soldered and isothermally aged (at 150°C for up to 42 days) conditions. The results of the interfacial intermetallic thickness showed that for the case of the unreinforced...
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...
In this study, Ag/NiNiP-plated Cu leadframes from two different processes are compared in terms of NiNiP surface morphology, composition of NiP layer, grain structures of Ni and NiP plated layers, and impurities in the interface of Ni/NiP plated layers. Their impacts were assessed after solder plating and baking. Scanning electron microscopy (SEM) shows that the grain size of Leadframe A (from Process...
Interfacial reactions during Si die attachment with Zn-Al-Mg-Ga high-temperature lead (Pb)-free solder on bare Cu lead-frame (Tamac 4) and Ni metallized Cu lead-frame were investigated using an optical microscope, scanning electron microscope (SEM) and energy dispersive x-ray (EDX). Die attachment was performed in an automatic die attach machine in a forming gas environment at temperature 380°C. The...
This paper investigated the root cause of component fell-off from hand-held products after drop test. Failure modes are cracks at solder joints. Microstructure and fracture morphology of ENIG pad and solder joint were investigated through optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The solder alloy used for assembly is SAC305 (SnAg3.0Cu0.5)...
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 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...
The experimental samples mainly are the assembled OSP PCB with the Plated-Through-Hole (PTH) components which leads are manufactured with Sn/Ni/Cu substrates and the soldering process is Wave-Soldering (W/S) with two kinds of lead-free SAC solder bars categorized as Sn-3.0wt%Ag-0.5wt%Cu (SAC305) and Sn-0.3wt%Ag-0.7wt%Cu (SC0307). In addition, the test conditions are defined that the experimental temperatures...
The Ni-P alloy [or Ni(P)] with a 6-13 wt.% P content is a very common surface finishing material used in microelectronic packages. When a high P-content Ni(P) finish (≃13 wt.%) was jointed to the Sn-based solders, there are several possible P-containing intermetallics, e.g., Ni2SnP, Ni2P, Ni12P5, and Ni3P, can form at the interface. Among these intermetallics, the Ni2SnP layer played a major role...
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...
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...
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