Moo-Chin Wang

Formation of intermetallic compounds at eutectic Sn-Zn-Al solder/Cu interface

The eutectic Sn–Zn–Al solder alloy was used [composition: 91Sn–9(5Al–Zn)] to investigate the intermetallic compounds (IMCs) formed between solder and a Cu substrate. Scanning electron microscope, transmission electron microscope, and electron diffraction analysis were used to study the IMCs between solder and a Cu substrate. The γ–Cu 5 Zn 8 and γ–Cu 9 Al 4 IMC s were found at the Sn–Zn–Al/Cu interface. Thermodynamic calculation can explain the formation of γ–Cu 5 Zn 8 and γ–Cu 9 Al 4 IMC s instead of Cu–Sn compounds. The formation and growth of γ–Cu 9 Al 4 IMC at 423 K resulted in the decrease of adhesion strength at the interface of solder and a Cu substrate, where the Kirkendall voids were severely formed. As the heating time increased up to 1000 h at 423 K, the adhesion strength between the eutectic Sn–Zn–Al solder and a Cu substrate decreased from 7.6 ± 0.7 MPa to 4.4 ± 0.8 MPa.

Effects of process parameters on the soldering behavior of the eutectic Sn-Zn solder on Cu substrate

The effects of process parameters such as flux, dipping temperature and the heat-treatment on the soldering behaviors of the eutectic solder (composition: 91Sn-9Zn) hot-dipped on Cu substrates were investigated. The most suitable flux as tested was oleic acid for the eutectic Sn-Zn solder system hot-dipped on Cu substrate for the solder coverage. The adhesion strength obtained increased from 9.6±0.6 MPa to 11.9±0.6 MPa when the dipping temperature increased from 250 °C to 300 °C. However, it decreased from 11.9±0.6 MPa to 5.2±2.2 MPa as the sample was heated at 150 °C for 1200 h. Planar γ-Cu5Zn8 isolate-shaped η-Cu6Sn5 intermetallic layers were found in the bulk sample after heating at 150 °C for 300 h but was not found in the as-cast sample. In the plate samples, scallop-shaped γ-Cu5Zn8/inverted trigonal-shaped η-Cu6Sn5 intermetallic layers were found after heating at 150 °C for 600 h. Some pores were found at the interface between γ-Cu5Zn8 intermetallic compound (IMC) and the solder alloy, which might come from the formation and growth of IMCs and decreased the adhesion strength.

SOLVENT DEBINDING MECHANISM FOR ALUMINA INJECTION MOLDED COMPACTS WITH WATER-SOLUBLE BINDERS

The solvent debinding process has been widely accepted in the ceramic injection molding (CIM) industry process due to its short debinding cycle. However, the organic solvents most adopted in solvent debinding now are flammable, carcinogenic and not environmentally acceptable. For eliminating the use of unsound solvents, water-soluble polyethylene glycol (PEG) is used in this study to modify the pattern of debinding in CIM. The purpose of the investigation was to examine the binder behavior during solvent debinding based on water extraction for a multi-component PEG binder system. Based on the in situ evaluation results of dimensional variations, mercury intrusion data and scanning electron microscope (SEM) observations, possible solvent debinding mechanism for alumina injection molded compacts with water-soluble binders is proposed.

Electrochemical Behaviors of the Sn-9Zn-xAg Lead-Free Solders in a 3.5 wt % NaCl Solution

The electrochemical behaviors, microstructures, and corroded products of Sn-9Zn-xAg lead-free solders were investigated in this study. The 63Sn-37Pb and Sn-3.5Ag solder alloys were also tested for comparison. The Sn-3.5Ag solder alloy had a higher equilibrium potential (-0.44 V SCE ) than the ones of 63Sn-37Pb (-1.10 V SCE ) and Sn-9Zn (-1.43 V SCE ). The Ag addition enhanced the corrosion resistance of the Sn-9Zn solder alloy. Passivation behavior occurred in the solder alloys used in this study except the 63Sn-37Pb one. X-ray diffraction patterns showed that the Zn segregated in the Sn-9Zn solder alloy as solidified, but it dissolved when 0.5 wt % Ag was added to the solder alloy. The AgZn 3 and Ag 5 Zn 8 were found in the Sn-9Zn-1.5Ag solder alloy but they were substituted by the Ag 3 Sn when the Ag content in the solder alloy was above 2.5 wt %. However, they were the initial sites for pits formation. The corroded product of SnCl 2 was observed in all solder alloys tested. In addition, the ZnCl 2 , ZnO, and SnO were observed in the Sn-9Zn-xAg solder alloys.

Dielectric properties of Ba(ZrxTi1−x)O3 thin films prepared using radio frequency magnetron sputtering

Pt/Ba(ZrxTi1−x)O3/Pt/Ti/SiO2/Si capacitors were fabricated using radio frequency (rf) magnetron sputtering. The deposition parameter effects on the dielectric constant, capacitance, and leakage current density of the capacitors were investigated. Amorphous Ba(ZrxTi1−x)O3 (BZxT1−x) thin films were sputtered onto a substrate with a temperature of 300 °C, rf power of 130 W, and in a no-oxygen atmosphere. BZxT1−x thin films deposited onto Pt-coated Si substrates show a preferred orientation in the (100) reflection. The dielectric constants of the BZxT1−x thin films increased with increasing Zr content and deposition temperature. The diffuse phase transition behavior of the BZxT1−x thin films became more pronounced at high Zr content films. The leakage current density of the Pt/Ba(ZrxTi1−x)O3/Pt/Ti/SiO2/Si capacitors at 1 kV/cm was about 1.0×10−7 A/cm2. This increased with increasing deposition temperature but decreased with increasing O2/(O2+Ar) ratio. From the films, P–E hysteresis loops, the BZ0.1T0.9 thin ...

The effects of flux on the wetting characteristics of near-eutectic Sn-Zn-In solder on Cu substrate

The effects of flux on the wetting characteristics of the near-eutectic Sn-Zn-In solder alloy [composition: 86Sn-9Zn-5In] on Cu substrate have been studied by using dimethylammonium chloride (DMAHCl), stearic acid (SA), lactic acid (LA) and oleic acid (OA) as fluxes. Wetting time and maximum force were estimated from the wetting experiments. According to the wetting curves obtained by wetting balance apparatus, the SA and OA are not suitable as flux for the near-eutectic Sn-Zn-In solder on Cu substrate. However, the LA and DMAHCl provide a good wetting behavior. The lowest wetting time (0.27 s) was obtained with 3.5 wt% DMAHCl as flux as-dipped at 300°C. When the dipping temperature increased from 250 to 300°C, the wetting time decreased obviously from about 0.6 to 0.4 s while the LA and DMAHCl were used as flux. When the content of LA was less than 5.0 vol% at 250°C and 2.5 vol% at 300°C, non-wetting or partial wetting was observed as determined by wetting curves. In addition, for the content of DMAHCl less than 1.5 wt% at 250 and 300°C, non-wetting or partial wetting was also observed. Quite different from the most tin-based solders for Cu substrate, intermetallic compound γ-Cu5Zn8 was found by the X-ray diffraction (XRD) and selected area electron diffraction (SAED) analyses at the interface of solder and substrate after etching out the unreacted solder layer. The Zn element was enriched at the interface between solder and Cu substrate as analyzed by line scanning.

Structural and dielectric characterization of the (Ba1-xSrx)(Ti0.9Sn0.1)O3 thin films deposited on Pt/Ti/SiO2/Si substrate by radio frequency magnetron sputtering

(Ba1−xSrx)(Ti0.9Sn0.1)O3 (BSxTS) thin films prepared by rf magnetron sputtering have been characterized as a function of temperature, applied voltage, and electric field. The BSxTS thin films have been confirmed with x-ray diffraction and electron diffraction analysis. The BSxTS thin films show a strong (111) preferred orientation for Sr content 0.1≦x≦0.3. Grain size increases with increasing deposition temperature and is correlated to high dielectric constants. Leakage current density at 1 kV/cm varies from below 10−7 to mid 10−9 A/cm2 for the O2/(O2+Ar) ratio varying from 5/(5+5) to 1/(1+9). A large and clear hysteresis shows ferroelectricity at 25 °C for all BSxTS thin films. The remnant polarization increases with increasing Sr content, which is preseemably caused by the lattice mismatch between BSxTS thin films and Pt layers.

Dielectric Properties of Nanocrystalline Barium Titanate Thin Films Deposited by RF Magnetron Sputtering

The nanocrystalline thin films of BaTiO3 have been deposited on the Pt/Ti/SiO2/Si substrates by RF magnetron sputtering at 500°C. The film deposited at 500°C has a thickness of 450.0 nm and is composed of granular crystallites of about 45.0 nm size. The crystallite size decreases with decreasing film thickness. The dielectric constant of the nanocrystalline BaTiO3 thin films increases with increasing film thickness. For the film thicknesses of 150.0 and 450.0 nm, the leakage current density is below 1.0×10-9 A/cm2 for the applied voltage of less than 5 V.

Effect of process parameters on synthesis of aluminum nitride powder prepared by chemical vapor deposition

Ultrafine aluminum nitride (AlN) powders were obtained by the chemical vapor deposition (CVD) process via the AlCl3-N2-NH3 system operated at various temperatures and different mixing modes of AlCl3 and NH3 gases. X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), transmission electron microscope (TEM) and electron diffraction (ED) were utilized to study the effect of process parameters on the synthesis and characterization of the AlN powders. It had been shown that all of the obtained powders were exclusively identified to be the single phase AlN and were indifferent to the different mixing modes AlCl3 and NH3 gases. The yield of synthesized AlN powder was affected by the entries mixing position of the reacting gases of AlCl3 and NH3.The yield increased from 13% to 82% where the mixed position was shifted from the front edge to middle point of the quartz tube. On the other hand, the yield increased from 5% to 82% as the reaction temperature increased from 600°C to 1050°C. The morphology of the AlN powders was affected by the diameter of a feeding nozzle and mixing mode of AlCl3 and NH3 gases.

Sintering and piezoelectric properties of Pb(Ni1/3Sb2/3)O3-PbZrO3-PbTiO3 ceramics

The sintering and piezoelectric properties of Pb(Ni1/3Sb2/3)O3-PbZrO3-PbTiO3 ceramics have been investigated. When the powders contain 48 mol% PbTiO3 and less than 10 mol% Pb(Ni1/3Sb2/3)O3 followed by calcination at 850°C for 2 h, the calcine only contains the perovskite structure; but if the Pb(Ni1/3Sb2/3)O3 content is between 12 mol% and 14 mol%, both tetragonal and rhombohedral phases are obtained. The composition of the morphotropic phase boundary(MPB) in the Pb(Ni1/3Sb2/3)O3-PbZrO3-PbTiO3 system is Pb(Ni1/3Sb2/3)O3 = 12 mol%, PbZrO3 = 40 mol% and PbTiO3 = 48 mol%. As the composition at the MPB is sintered at 1260°C and 1280°C for 2 h, respectively, the maximum density (7.8 g/cm3) is obtained. The SEM micrographs indicate that a decrease in porosity with increasing sintering temperature is attained at 1280°C, which is due to a decrease in the number and size of pores. When the sintering temperature is higher than 1280°C, the porosity increases due to PbO evaporation leading to an increase of the number of pore sites and in enlargement of the pore diameter. When the compact composition at MPB is sintered at 1280°C for 2 h, the planar coupling coefficient (Kp) and mechanical quality coefficient (Qm) tend to approach the maximum (0.488) and minimum values (292.5), respectively.