Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications

As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au-Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au-Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Two distinct phases, Au5Sn and AuSn, were deposited at a composition of 30at.%Sn. The Au-Sn flip-chip joints were formed at 300 and 400 degrees without using any flux. In the case where the samples were reflowed at 300 degrees, only an (Au,Ni)3Sn2 IMC layer formed at the interface between the Au-Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)3Sn2 and (Au,Ni)3Sn, were found at the interfaces of the samples reflowed at 400 degrees. As the reflow time increased, the thickness of the (Au,Ni)3Sn2 and (Au,Ni)3Sn IMC layers formed at the interface increased and the eutectic lamellae in the bulk solder coarsened.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Microstructure and adhesion characteristics of a silver nanopaste screen-printed on Si substrate

The microstructural evolution and the adhesion of an Ag nanopaste screen-printed on a silicon substrate were investigated as a function of sintering temperature. Through the two thermal analysis methods, such as differential scanning calorimeter and thermo-gravimetric analysis, the sintering conditions were defined where the temperature was raised from 150°C to 300°C, all with a fixed sintering time of 30 min. The microstructure and the volume of the printed Ag nanopaste were observed using a field emission scanning electron microscope and a 3-D surface profiler, respectively. The apparent density of the printed Ag nanopaste was calculated depending on the sintering conditions, and the adhesion was evaluated by a scratch test. As the sintering temperature increased from 150°C to 300°C, the apparent density and the adhesion increased by 22.7% and 43%, respectively. It is confirmed that the printed Ag nanopaste sintered at higher temperatures showed higher apparent density in the microstructural evolution and void aggregation, resulting in the lower electrical resistivity and various scratched fractures

Synergistic effect of Indium and Gallium co-doping on growth behavior and physical properties of hydrothermally grown ZnO nanorods

We synthesized ZnO nanorods (NRs) using simple hydrothermal method, with the simultaneous incorporation of gallium (Ga) and indium (In), in addition, investigated the co-doping effect on the morphology, microstructure, electronic structure, and electrical/optical properties. The growth behavior of the doped NRs was affected by the nuclei density and polarity of the (001) plane. The c-axis parameter of the co-doped NRs was similar to that of undoped NRs due to the compensated lattice distortion caused by the presence of dopants that are both larger (In3+) and smaller (Ga3+) than the host Zn2+ cations. Red shifts in the ultraviolet emission peaks were observed in all doped NRs, owing to the combined effects of NR size, band gap renormalization, and the presence of stacking faults created by the dopant-induced lattice distortions. In addition, the NR/p-GaN diodes using co-doped NRs exhibited superior electrical conductivity compared to the other specimens due to the increase in the charge carrier density of NRs and the relatively large effective contact area of (001) planes. The simultaneous doping of In and Ga is therefore anticipated to provide a broader range of optical, physical, and electrical properties of ZnO NRs for a variety of opto-electronic applications

First record of the Genus Ennearthron Mellié (Coleoptera: Tenebrionoidea: Ciidae) in Korea, with three new records and its host fungi

The Genus Ennearthron Mellié, 1847 is taxonomically reviewed for the first time in Korea. Three species: Ennearthron chujoi Nakane & Nobuchi, 1955, Ennearthron ishiharai Miyatake, 1954, and Ennearthron robusticorne Kawanabe, 1996 are newly reported from Korea. Redescriptions for each species, photographs of adults, line drawings of the diagnostic characters, and the ecological information of the host fungi are provided

Effect of surface finish of substrate on mechanical reliability of IN-48SN solder joints in MOEMS package

Interfacial reactions and shear properties of the In-48Sn (in wt.%) ball grid array (BGA) solder joints after bonding were investigated with four different surface finishes of the substrate over an underlying Cu pad : electroplated Ni/Au (hereafter E-NG), electroless Ni/immersion Au (hereafter ENIG), immersion Ag (hereafter I-Ag) and organic solderability preservative (hereafter OSP). During bonding, continuous AuIn2, Ni3(Sn,In)4 and Cu6(Sn,In)5 intermetallic compound (IMC) layers were formed at the solder/E-NG, solder/ENIG and solder/OSP interface, respectively. The interfacial reactions between the solder and I-Ag substrate during bonding resulted in the formation of Cu6(Sn,In)5 and Cu(Sn,In)2 IMCs with a minor Ag element. The In-48Sn/I-Ag solder joint showed the best shear properties among the four solder joints after bonding, whereas the solder/ENIG solder joint exhibited the weakest mechanical integrity

effects on microstructure, mechanical properties and corrosion resistance of arc-evaporated CrTiAlN nanocomposite films on AISI 304 stainless steel, Thin Solid Films 519

The microstructures and mechanical properties of the friction welded pure Ti/AISI 321 stainless steel have been investigated. From the Ti side from the interface to the Ti base metal, the sequence of recrystallized grain, elongated grain and many twin embedded grain structures were observed. The reaction layers were formed within 0.2 mm thickness at the interface under the conditions of relatively longer friction time (t 1 ) and lower upset pressure (P 2 ). These reaction layers formed at the central interface were identified as (Fe, Cr) 2 Ti, FeTi 2 or Fe 2 Ti 4 O and -Ti, while those of the peripheral interface were identified as FeCr ( phase), (Fe, Cr) 2 Ti, FeTi and -Ti. The phase was restrictedly formed at the peripheral interface. Higher mechanical properties were acquired under higher upset pressure condition due to higher compressive force between bonded materials, smaller grain size and narrower thickness of reaction layer. Therefore, maximum ultimate tensile strength of these joints was approximately 420 MPa with the conditions of 400 MPa of P 2 and 0.5 s of t 1

SURFACE MODIFICATION OF PLASMA TREATMENT ON SiO2 LAYER WITH UNDERFILL

The plasma treatment on SiO2 substrate surfaces increased the oxygen-containing functional groups or the polar component of the surface free energy and, the wetting characteristics of the underfills/SiO2. The plasma treatment condition which gave the smallest contact angle between the underfills and SiO2 was an operating time of 60 sec under O2 gas atmosphere and a power of 200 W.Plasma treatment, silicon oxide, surface modification, underfill

Three species of the family Zopheridae (Coleoptera) new to Korea

Three species of the family Zopheridae, Usechus tsushimensis Kamiya, 1963, Synchita tokarensis (Nakane, 1968), and Synchita oculata (Sharp, 1885) are reported for the first time in Korea. Diagnoses, photographs of the adults, and the line drawings of the diagnostic characteristics for each species are presented