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

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

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