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SnAgCu (SAC) solder is being offered as a lead-free termination finish. SAC finish is obtained by dipping the terminals of components into molten SAC solder. However, the reliability of solder joints formed with SAC solder refinished components needs to be determined in order to evaluate the effects of the SAC solder refinishing process. In this paper, the strength of solder joints with SAC solder...
This study, mainly emphasis on effects of solder volume on interfacial diffusion kinetics and mechanical properties of Sn/Cu microbump solder joints. Different thicknesses i.e. 12 μm Sn (electrodeposited) and 100 and 200μm Sn is screen printed over 14 μm thickness Cu under bump metallization (UBM). The diameter of Cu UBM used in this study is 50, 110 and 240μm respectively. Solder joints are subjected...
Low temperature stacking of dies for 3D integration has been gaining interest due to the thermal sensitivity of some advanced node devices such as DRAM. Sn-based solder joint is considered as a promising approach for making die to die interconnections due to its low bonding temperature and high yield. Previously the Cu/Sn solid state diffusion bonding at 150 °C was reported, during which the bonding...
This paper presents a zero-level packaging technology for hermetic encapsulation of MEMS. The technology relies on the “chip capping” of the MEMS using a metallic bond made by means of diffusion soldering of a Cu-Sn system at a temperature of around 250°C. For this, on a “capping wafer” a sealing ring (or bond frame), composed of a double layer of Cu/Sn, is grown, and on the MEMS wafer a matching...
A demand for small form factor in IC packaging has lead to a reduced bump size and an increased current density. The high current density accompanying with Joule heat induces an electromigration failure. In this study, we investigated the effects of under bump metallization (UBM) on the electromigration failure. Three types of UBM such as Cu 5 μm, Cu 10 μm and Cu 5 μm/Ni 2μm were compared with 60...
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...
The experimental results show that the formation of inter-metallic layers is controlled by diffusion and that the inter-metallic layers grow in a parabolic manner by the thermal activation. The results indicate three symptoms. The first one is that the thickness of IMC increases as the aging time extends. The second one is that Cu is partially molten, which the IMC interface between solder pastes...
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...
Current methods for the formation of pre-solder bumps for flip chip attachment use stencil printing techniques with an appropriate solder paste. The continuing trend towards increasing miniaturisation and the associated decrease in size of solder resist opening, SRO is causing production difficulties in particular associated with achieving sufficient yields with the stencil printing process. Practical...
Tin plating of lead frame packages has been driven into the market to meet Green requirements. To avoid tin whiskers issue, Sn-Cu and Sn-Bi are the other option in stead of pure Tin plating. Copper oxidation will give rise solder blisters if machine breakdown during Sn-Cu plating process for lead frame packages. The poor contacts resulted in contact area due to copper oxidization which in turn caused...
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...
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...
The interfacial reactions between (001) Ni single crystal and high-Sn solders were compared with those of polycrystalline Ni. The morphology of interfacial intermetallic compound (IMC) grains formed between (001) Ni single crystal and high-Sn solders (pure Sn, Sn-0.7Cu, Sn-0.7Cu-0.1Ni, Sn-1.5Cu and Sn-1.5Cu-0.1Ni, all in wt. %) at 250 °C and 300°C for various durations was investigated. Regular arrangement...
The line-type Cu/Sn/Ni interconnects were used to determine the effect of electromigration (EM) on the Cu-Ni cross-interaction under the current density of 1.0×104 A/cm2 at 150 °C for 100 h and 200 h. For the purpose of comparison, the line-type Cu/Sn/Ni interconnects were also aged at 150 °C for 100 h and 200 h. After soldering, Ni3Sn4 and Cu6Sn5 IMCs formed at the Sn/Ni and Sn/Cu interfaces, respectively...
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 combined effects of thermomigration (TM) and electromigration (EM) were investigated in Cu/Sn3.0Ag0.5Cu/Ni solder joints by applying a 5×103A/cm2 DC current to the joints. With a thermal gradient, the Cu atoms and Ni atoms were found to migrate towards the lower temperature side while the Sn atoms were found to migrate towards the higher temperature side. For the solder joint stressed with a 5×10...
The current study revealed that the growth kinetics and the interfacial reaction of the Cu/Sn/Ag couples with different thickness solder. For the Cu/Sn/Ag couples, plate-type Ag3Sn was firstly formed at the Sn/Cu interface rather than at the Sn/Ag interface for the Cu/Sn/Ag couple at the initial state of the reflow procedure when the solder thicknesses is 150 μm or 300 μm. Besides, the microstructure...
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