Yee-Wen Yen

Nickel and copper deposition on fine alumina particles by using the chemical vapor deposition-circulation fluidized bed reactor technique

A Chemical Vapor Deposition-Circulation Fluidized Bed Reactor technique has been developed to deposit metallic Ni and Cu onto alumina particles of 45 μm diameter. The furnaces consisted of upper and lower zones, and the deposition precursors were produced both in situ and by vaporization of chlorides. X-ray diffraction, metallographical examination, and compositional analysis were used to analyze the deposition layers. For both Ni and Cu deposition, the deposition rates increased with higher temperatures of the lower furnace. The rates increased with greater amounts of chloride addition as well, but they reached plateaus when the amounts of addition were more than 40%.

Interfacial reactions between lead-free solders and the multilayer Au/Ni/SUS304 substrate

Abstract Interfacial reactions between Sn, Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and an Au/Ni/SUS304 stainless steel (SUS304) substrate were conducted using the reaction couple technique at 240, 255 and 270 °C for 1 – 5 h. In the earliest stage of the reaction, only the Ni3Sn4 phase was formed on the Sn/Au/Ni/SUS304 interface. As the reaction time increased to 4 h, the Ni layer was gradually consumed and the Ni3Sn4 phase detached from the interface. Meanwhile, the Sn reacted with the SUS304 to form the FeSn2 phase. In the SAC/Au/Ni/SUS304 reaction couple, both Ni3Sn4 and Cu6Sn5 phases were formed on the interface. When the reaction time exceeded 4 h, the Ni3Sn4 phase disappeared; the Cu6Sn5 phase was spread over the SUS304 surface and the FeSn2 phase was formed on the SUS304 surface. The growth of intermetallic compounds can be described by the parabolic law and the reactions were diffusion-controlled.

Investigation of Interfacial Reactions and Sn Whisker Formation in the Matte Sn Layer With NiP/Ni/Cu and Ni/Cu Multilayer Systems

This paper investigates the relationship between the interfacial reactions and Sn whisker formation in the matte Sn layer in NiP/Ni/Cu and Ni/Cu multilayer systems. All specimens were first reflowed at 250°C for 10 min and then aged at 150°C for 500 h. Sn whiskers were found only in the Sn/Ni/Cu multilayer specimen. Ni from the NiP layer was consumed to form the Ni3Sn4 phase in the Sn/NiP/Ni/Cu specimen. Thus, the phosphorous (P) atoms segregated at the interface and reacted with Ni and Sn atoms to form the Ni-P-Sn ternary phase between the phase and NiP layer. This Ni-P-Sn ternary phase acted as a diffusion barrier and decreased the diffusion rate and diffusion flux of the Ni atoms. The compressive stress induced by the flux of the Ni atoms was the driving force resulting in Sn whisker growth. The Ni-P-Sn ternary can inhibit this compressive stress. That is why no Sn whiskers were found in the Sn/NiP/Ni/Cu multilayer specimen.

Effect of minor addition of Pb upon interfacial reactions and mechanical properties at Sn-3.0Ag-0.5Cu/Cu and Sn-58Bi/Cu solder joints

Abstract Interfacial reactions and mechanical properties between the Cu and Pb-free solders, Sn-3.0Ag-0.5Cu and Sn-58Bi with addition of 0.1 to 1.0 wt.% Pb are investigated in this study. Two kinds of intermetallic compounds, scallop-shaped Cu6Sn5 and plane layered Cu3Sn phases, were found in both Sn-3.0Ag-0.5Cu + Pb/Cu and Sn-58Bi + Pb/Cu couples. The intermetallic compound thickness increased with longer reaction times, higher reaction temperatures and greater Pb contents. The Cu6Sn5 phase was the thicker intermetallic compound in the Sn-3.0Ag-0.5Cu + Pb/Cu couple. However, in the Sn-58Bi + Pb/Cu system, the Cu3Sn phase is the thicker intermetallic compound. Experimental results indicate that the higher Pb concentration in Sn-3.0Ag-0.5Cu or Sn-58Bi solders reduces the alloy liquidus temperature and increases the thickness of the intermetallic compound. Thicker intermetallic compounds reduce the mechanical strength of the solder joint.

Study of interfacial reactions between Sn–Ag–Cu alloys and Au substrate

Abstract Interfacial reactions between Sn – Ag – Cu lead-free solders and Au were investigated by the use of SAC/Au solid/solid reaction couples which were annealed at 150, 180 and 200 °C for various reaction times. Five intermetallic compounds, AuSn, AuSn2, AuSn4, (Au, Cu)Sn, and (Cu, Au)5Sn6, were formed at a higher temperature and lower Cu content. As the reaction temperature was dropped and Cu content was increased, only three intermetallic layers, AuSn, (Au, Cu)Sn, and (Cu, Au)5Sn6, could be observed. Meanwhile, when the Cu content in SAC alloys increased, the thickness of total reaction layers decreased, but that of (Au, Cu)Sn/(Cu, Au)6Sn5 layers increased. It likely resulted from (Au, Cu)Sn/(Cu, Au)6Sn5 layers acting as a diffusion barrier to resist Sn diffusing to Au – Sn intermetallic compounds and decrease the growth rate of Au – Sn intermetallic compounds. The growth and formation of intermetallic compounds are sensitive to the reaction temperature and Cu content in the SAC/Au couple systems.

Thermodynamic assessment of the Hg-Sn system

A thermodynamic assessment of the Hg-Sn system has been carried out using the CALPHAD method. The comprehensive assessment covers the extensive phase diagram data as well as the enthalpy, activity, and vapor pressure data. Two cases of intermetallic compounds in the Hg-Sn system are considered. Case 1 considers the intermetallic compounds β, γ, and HgSn4 as having no solubility and can thus be treated as the stoichiometric phases β-HgSn38, γ-HgSn12, and HgSn4. Case 2 uses a sublattice model to more accurately describe a solubility of the γ phase; it also considers the stoichiometric δ-HgSn7 phase. The ε phase was considered to be metastable and neglected in the thermodynamic assessment. Thermodynamic parameters have been optimized using all the assessed experimental thermodynamic and phase equilibrium data. Both calculated phase diagrams of the Hg-Sn system (Cases 1 and 2) and the thermodynamic data are reasonable and satisfactory when compared with literature data. Future crucial experiments are suggested.

Substrate Shape Effect on the Sn Whisker Growth in the Electroplating Matte Sn System

In this study, the substrate shape effect on the Cu substrates for Sn whisker growth has been investigated. A Cu foil, as a substrate, was bent to 90° by a universal testing machine. The matte Sn layers were electroplated on the Cu substrate under various current densities. Then, the samples were given heat treatment under various temperatures for 250 h. The results indicate that Sn whisker growth was promoted by the compression stress on the concave side and was restrained by the tension stress on the convex side. The increase of plating thickness in electroplating process offered the extensive residual stress to mitigate the Sn whisker growth. Increasing the aging temperatures also enhanced the thickness of the oxide layer. Thick oxide layers can prevent Sn whisker growth.

Interfacial reactions between SAC405 and SACNG lead-free solders with Au/Ni(P)/Cu substrate reflowed using the CO2 laser and hot-air methods

This study investigated the interfacial reactions between Sn-4.0Ag-0.5Cu (wt.%) (SAC405) and Sn-4.0Ag-0.5Cu-0.05Ni-0.01Ge (wt.%) (SACNG) lead free solders with an Au/Ni(P)/Cu substrate reflowed using the CO2 laser and hot-air methods. A mixture of two intermetallic compounds, (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4 phases, was formed at the interface when the solder/substrate couples were reflowed using the CO2 laser. When the specimen was aged at 150°C, the thickness of the (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4 phases increased as the aging time increased. The (Cu, Ni)6Sn5, (Ni, Cu)3Sn4, Ni–Sn–P and Ni3P phases were formed at the interface when the specimens were reflowed using the hot-air method at 240°C and aged at 150°C for a long reaction period. Due to a rapid cooling-rate in the CO2 laser reflowing system, solidification phases with finer microstructure were found in the solder matrix.

Reaction Mechanism of the Two-Step MOCVD of Copper Thin Film Using Cu ( hfac ) 2 ∙H2O Source

,G5 2005 . The current study tested the feasibility ofcondensing the two steps into one, but unexpectedly discovered an interesting phenomenon. Consequently, the mechanisms of thetwo-step MOCVD of Cu films have become clear. The determination of detailed mechanisms of this MOCVD method can furtherestablish its status as a replacement for sputtering in the deposition of seed layers for electroplating.© 2005 The Electrochemical Society. DOI: 10.1149/1.2052050 All rights reserved.Manuscript submitted May 27, 2005; revised manuscript received July 11, 2005. Available electronically September 12, 2005.

Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.