138 research outputs found
Типовая учебная программа для высших учебных заведений по специальности 1-21 01 01 Теология
Effects of Bi additions to Ag-containing lead-free solders have been the focus of a considerable amount of past investigation. However, the influence of Bi on Sn-Cu-Ni solders has not been studied extensively. In the present study, we explore the influence of Bi on microstructure formation of Sn-0.7Cu-0.05Ni/Cu solder joints both in the bulk and at the interface. It is shown that (i) Sn-0.7Cu-0.05Ni solidifies to produce a markedly different grain structure to Ag-containing lead-free alloys, with 5-8 independent βSn grains in each joint; (ii) Bi additions to Sn-0.7Cu-0.05Ni maintain this distinct βSn grain structure and had no discernible effect on the (Cu,Ni)6Sn5 interfacial intermetallic layers or primary intermetallic crystals
Effect of Ni on the Formation and Growth of Primary Cu6Sn5 Intermetallics in Sn-0.7 wt.%Cu Solder Pastes on Cu Substrates During the Soldering Process
Nickel-stabilized hexagonal (Cu, Ni)(6)Sn-5 in Sn-Cu-Ni lead-free solder alloys
CuSn is an important intermetallic compound (IMC) in lead-free solder alloys. CuSn exists in two crystal structures with an allotropic transformation from monoclinic η′-CuSn at temperatures lower than 186 °C to hexagonal η-CuSn. A detailed analysis by transmission electron microscopy (TEM) in Sn-0.7 wt.% Cu-0.06 wt.% Ni reveals that when the Ni content in (Cu, Ni)Sn is ∼9 at.% Ni, the hexagonal allotrope of (Cu, Ni)Sn becomes stable at room temperature
Perifollicular pigmentation is the first target for topical vitamin C derivative ascorbyl 2-phosphate 6-palmitate (APPS): Randomized, single-blinded, placebo-controlled study
Shear and tensile impact strength of lead-free solder ball grid arrays placed on Ni (P)/Au surface-finished substrates
This study aims to investigate the shear and tensile impact behavior of ball grid arrays (BGAs) placed on Ni (P)/Au surface-finished substrates considering the microstructure and compositions of intermetallic compounds (IMCs) formed at the solder/substrate interfaces. Tests were conducted on as-reflowed and aged samples with four different compositions of solders such as Ni-doped and non-Ni-doped Sn-0.7 wt.%Cu, Sn-37 wt.%Pb and Sn-3.0 wt.%Ag-0.5 wt.%Cu, over a wide range of displacement rates from 10 to 4000 mm/s in shear and from 1 to 400 mm/s in tensile tests. In shear tests, there was almost no difference between as-reflowed and aged samples at low displacement rates in all the samples, while at high displacement rates the aged samples showed better properties than as-reflowed ones, in particular, in Ni-doped Sn-0.7wt%Cu samples. In tensile tests, the aging treatments had little effect on the strength for any compositions of solders at low and high displacement rates. Sn-3.0 wt.%Ag-0.5 wt.%Cu samples with any heat treatments showed the least resistance to both shear and tensile loadings at any displacement rates
Cracking and phase stability in reaction layers between Sn-Cu-Ni solders and Cu substrates
A method of limiting cracking in the Cu6Sn5 intermetallic compounds (IMCs) at the interface between lead-free solders and copper substrates has been developed. To explore the mechanism of crack inhibition in the nickel-containing IMC reaction layers, detailed synchrotron x-ray powder diffraction with Rietveld analysis and differential scanning calorimetry have been used. The results show that nickel stabilizes the high-temperature hexagonal allotrope of Cu6Sn5, avoiding stresses induced by a volumetric change that would otherwise occur on transformation to the monoclinic phase
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