JOURNALOF MATERIALS SCIENCE: MATERIALS IN ELECTRONICS 15 (2004) 205±209 Structural, mechanical, hardness indentation measurements of Sn 65  x Ag 25 Sb 10 Cu x solder alloys rapidly solidi®ed from melt at cooling rate 1.1 6 10 5 Ks  1 R. M. SHALABY Faculty of Science, Metal Physics Laboratory, Physics Department, Mansoura University, Mansoura, Egypt E-mail: rizk1969@yahoo.co.uk Structural, mechanical properties, and hardness indentation measurements of Sn 65  x Ag 25 Sb 10 Cu x (x  0,0.5,1.0,1.5,2.0,and2.5wt%)solderalloyshavebeenstudiedand analyzed. The alloy exhibits mechanical properties superior to those in both the Sn±Ag 25 binary and Sn±Ag 25 Sb 10 ternary solder alloys. The addition of small amounts of Cu is found to re®ne the effective grain size, while retaining the uniform distribution of Ag 3 Sn, SnSb, and Cu 10 Sn 3 precipitates in the solidi®cation microstructure, thus signi®cantly improving the ductility and strength. # 2004 Kluwer Academic Publishers 1. Introduction This study is an extension to previous work by this author that used a cooling rate of 3:7610 5 Ks  1 [1]. Pb±Sn alloys are the dominant solders in manufacturing because of their unique combination of material properties and low cost. However, there are mounting health and environmental concerns about the toxicity of Pb present in these alloys [2], and the search for potential replacement alloys has been an area of extensive research in recent years [3±6]. One new Pb-free alloy has been recently reported to offer superior mechanical properties in many respects. This ternary Sn±Ag 25 ±Sb 10 (wt %) alloy was found to have superior strength compared to Sn±Ag 25 binary alloy. These mechanical-property enhancements are attributed to microstructural differences between alloys that develop during solidi®cation. It is also noted [7] that the addition of small amounts of Cu, less than 1% re®nes the effective grain size, while retaining the uniform distribution of Ag 3 Sn precipitates in the solidi®cation microstructure, which signi®cantly improves the ductility. The addition of excess amounts of Cu or Zn beyond about 1% levels is not desirable as it causes precipitation of additional intermetallic phases that depletes the ®nal precipitate in the surrounding matrix and induces nonuniformities in the microstructure that consequently degrade the mechanical properties. Due to the health and environmental hazards posed by lead, the electronics industry is under pressure to ®nd alternatives to lead in the manufacturing process and in components. In the present study, melt-spun Sn 65  x Ag 25 Sb 10 Cu x alloys with various compositions have been investigated. The main purpose was to obtain new lead-free solder alloys for industrial applications. In addition, the high cooling rate improves the mechanical properties and produces attractive combinations of strength and ducti- lity for these alloys. 2. Experimental procedures High-purity materials have been used for the preparation of metallic alloys. The fragments of Sn, Ag, Sb, and Cu have a purity of 99.9%. The raw materials were melted in a porcelain crucible in an electric furnace at temperatures ranging from 900 to 1000K. Melting was repeated several times at the same temperature. The duration of each melting was 2 h. The ribbons were produced using a single aluminum roller at a cooling rate of 1:1610 5 Ks  1 (1200r.p.m. or 9:4ms  1 ). The alloy ribbons have an average thickness of 120±140 mm and are 0.5±1.0cm in width with composition Sn 65  x Ag 25 Sb 10 Cu x (x  0, 0.5, 1.0, 1.5, 2.0, and 2.5wt%). The procedure employed in the preparation of the melt-spun ribbons was reported previously [7±9]. The structure of the quenched ribbons was investi- gated by X-ray diffraction using CuK a radiation at room temperature. The elastic moduli of melt-spun ribbons were examined in an air atmosphere with a dynamic resonance method. Microhardness tests were conducted using a digital Vickers microhardness tester (model FM-7) applying a different load with different indentation time via a Vickers diamond pyramid. More than 15 indents, to each value were made on each sample to reveal any hardness variation due to the presence of more phases, with one 0957±4522 # 2004 Kluwer Academic Publishers 205