Sn-0.5Cu(-x)Al Solder Alloys: Microstructure-Related Aspects and Tensile Properties Responses

Abstract

In this study, experiments were conducted to analyze the effect of 0.05 and 0.1 wt.% Al additions during the unsteady-state growth of the Sn-0.5wt.%Cu solder alloy. Various as-solidified specimens of each alloy were selected so that tensile tests could also be performed. Microstructural aspects such as the dimensions of primary, λ1, and secondary, λ2, dendritic arrays, and intermetallic compounds (IMCs) morphologies were comparatively assessed for the three tested compositions, that is, Sn-0.5wt.%Cu, Sn-0.5wt.%Cu-0.05wt.%Al, and Sn-0.5wt.%Cu-0.1wt.%Al alloys. Al addition affected neither the primary dendritic spacing nor the types of morphologies identified for the Cu6Sn5 IMC, which was found to be either globular or fibrous regardless of the alloy considered. Secondary dendrite arm spacing was found to be enlarged and the eutectic fraction was reduced with an increase in the Al-content. Tensile properties remained unaffected with the addition of Al, except for the improvement in ductility of up to 40% when compared to the Sn-0.5wt.%Cu alloy without Al trace. A smaller λ2 in size was demonstrated to be the prime microstructure parameter associated with the beneficial effect on the strength of the Sn-0.5wt.%Cu(-x)Al alloys.

Microstructure Growth Morphologies, Macrosegregation, and Microhardness in Bi–Sb Thermal Interface Alloys

“…It is observed that despite the two morphological transitions in the Bi‐rich matrix, the power‐type experimental laws given by λ 1 = 331.8 () −0.55 and λ 2 = 16.8 ( V ) −1.1 may represent the evolution of these microstructural spacings for all the studied Bi–Sb alloys. The use of the −0.55 exponent in the experimental law has been demonstrated to effectively describe the dependence on the growth of λ 1 for several metallic alloys . Despite many studies having found equations given by λ 2 = constant ( V ) −2/3 for different alloy systems, the effects of lateral solute segregation on the wavelengths of instabilities along the sides of primary dendritic stems for Bi‐based alloys are still not well understood.…”

Solder Alloy Design: Investigation of Predictive Models for Tensile Properties Based on Different Alloy Compositions and Microstructures

“…Most of the studies [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] employed directional solidification systems to allow microstructural and tensile data to be assessed. After solidifying the casting, transverse (perpendicular to the solidification direction) and longitudinal samples (at various sections from the cooled bottom of the castings) were removed of alloy casting for the metallographic procedure using optical microscopy.…”

“…The secondary (λ2) and tertiary (λ3) dendritic arm spacings were measured by using the linear intercept method using longitudinal sections (parallel to the extraction direction of heat) and transversal, respectively. The same linear intercept method was adopted in some of the studies [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] for determining λfino, λcoarse, λcu6Sn5, λAg3Sn and λZn. Moreover, the tensile properties of the alloys were determined through tensile tests at different positions in the castings with strain rates in the order of 10 -3 s -1 .…”