The melting temperatures of most lead-free solder alloys are somewhat higher than that of eutectic Sn/Pb solder, and many of the alloys tend to wet typical contact pads less readily. This tends to narrow down the fluxing and mass reflow process windows for assembly onto typical organic substrates and may enhance requirements on placement accuracy. Flip chip assembly here poses some unique chall...

Eutectic-related reaction is a special chemical/physical reaction involving multiple phases, solid and liquid. Visualization of a phase reaction of composite nanomaterials with high spatial and temporal resolution provides a key understanding of alloy growth with important industrial applications. However, it has been a rather challenging task. Here, we report the direct imaging and control of ...

Alloy Al – 27% Cu – 6% Si has a composition close to an eutectic one [1, 2] and is widely used as a solder (A34) for soldering aluminum and its alloys [3]. The main problem in fabrication of cast solder A34 is the formation of a ternary ( + CuAl 2 + Si) eutectic and primary silicon crystals in its structure, which lowers substantially the process and operating properties of the alloys. It is kn...

Equal-channel angular pressing (ECAP) was utilized to process a Bi‒42Sn eutectic alloy at room temperature using processing route A for 1, 2, 4, and 8 passes. Tensile testing was performed at room temperature under initial strain rates in the range of 1.0 × 10 -5 to 1.0 × 10 -2 s -1 . The results demonstrate that processing by ECAP improves the ductility in this material and the elongations to ...

Sn3.0Ag0.5Cu (SAC305) is currently the most popular near eutectic lead-free alloy used in the manufacturing processes. Over the last several years, the price of silver has dramatically increased driving a desire for lower silver alloy alternatives. As a result, there is a significant increase in the number of alternative low/no silver lead-free solder alloys available in the industry recently. ...

Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through thi...

It was recently shown that silicon particles in heat-treated Al–Si casting alloys can contain flaws such as surface pinholes and grooves, which cause varying degrees of reduction in the in situ particle fracture strength and hence influence the mechanical properties of this class of alloys. In this work, we show that the formation of one class of such strength-limiting flaws in solidified and c...

Effective control of phase growth under harsh conditions (such as high temperature, highly conductive liquids or high growth rate), where surfactants are unstable or ineffective, is still a long-standing challenge. Here we show a general approach for rapid control of diffusional growth through nanoparticle self-assembly on the fast-growing phase during cooling. After phase nucleation, the nanop...