• Korean Journal of Materials Research
• /
• v.15 no.9
• /
• pp.598-603
• /
• 2005

To develope new lead-free solders with the melting temperature close to that of Sn-37Pb$(183^{\circ}C)$, Sn-0.7Cu-5Pb-1Ga, Sn-0.7Cu-5Pb-1Ag, Sn-0.7Cu-5Pb-5Bi-1Ag, and Sn-0.7Cu-SBi-1Ag alloys were composed by adding low-netting elements such as Ga, Bi, Pb, and Ag to Sn-0.7Cu. Then the melting temperatures, microstructures, wettability, and adhesion properties of these alloys were evaluated. DSC analysis showed that the melting temperature of Sn-0.7Cu-SPb-1Ga was $211^{\circ}C$, and those of other alloys was in the range of $192\~200^{\circ}C$. Microstructures of these alloys after heat-treatment at $150^{\circ}C$ for 24 hrs were basically composed of coarsely- grown $\beta-Sn$ grains, and $Cu_6Sn_5$ and $Ag_3Sn$ intermetallic precipitates. Sn-0.7Cu-5Pb-1Ga and Sn-0.7Cu-5Pb-5Bi-1Ag showed excellent wettability, while Sn-0.7Cu-5Bi-1Ag and Sn-0.7Cu-5Pb-5Bi-1Ag revealed good adhesion strength with the Cu substrates. Among 4 alloys, Sn-0.7Cu-5Pb-5Bi-1Ag with the lowest melting temperature $(192^{\circ}C)$ and relatively excellent wettability and adhesion strength was suggested to be the best candidate solder to replace Sn-37Pb.

• Korean Journal of Materials Research
• /
• v.19 no.1
• /
• pp.13-17
• /
• 2009

A semi-empirical method to estimate the surface tension of molten alloys at different oxygen partial pressures is suggested in this study. The surface tension of molten Ag-Sn and Ag-Cu alloys were calculated using the Butler equation with the surface tension value of pure substance at a given oxygen partial pressure. The oxygen partial pressure ranges were $2.86{\times}10^{-12}$－$1.24{\times}10^{-9}$ Pa for the Ag-Sn system and $2.27{\times}10^{-11}$－$5.68{\times}10^{-4}$ Pa for the Ag-Cu system. In this calculation, the interactions of the adsorbed oxygen with other metallic constituents were ignored. The calculated results of the Ag-Sn alloys were in reasonable accordance with the experimental data within a difference of 8%. For the Ag-Cu alloy system at a higher oxygen partial pressure, the surface tension initially decreased but showed a minimum at $X_{Ag}$ = 0.05 to increase as the silver content increased. This behavior appears to be related to the oxygen adsorption and the corresponding surface segregation of the constituent with a lower surface tension. Nevertheless, the calculated results of the Ag-Cu alloys with the present model were in good agreement with the experimental data within a difference of 10%.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2002.05a
• /
• pp.104-108
• /
• 2002

This paper was investigated the lead free solder characteristics by P mass percentage chang e. Tension test, wetting balance test, spread test, and analysis of intermetallic compound after isothermal aging of Sn-2.5Ag-0.7Cu-0.005P, Sn-2.5Ag-0.7Cu-0.01P, Sn-2.5Ag-0.7Cu-0.02P, Sn-0.7Cu-0.005P were performed for estimation. By adding P on the solder alloys, it was showe d improvement of tensile strength, reduction of intermetallic compound growth and reduction of oxidization of fusible solder under wave soldering processes. After comparing solder alloy containing P with tin lead eutectic solder alloy, p containing solder alloys showed much better solderability than eutectic solder alloys.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.6
• /
• pp.549-554
• /
• 2003

The purpose of this paper is to investigate the solder properties by the change of P mass percentage. Tension test, wetting balance test, spread test, and analysis of intermetallic compound after isothermal aging of Sn-2.5Ag-0.7Cu-0.005P, Sn-2.5Ag-0.7Cu-0.01P, Sn-2.5Ag-0.7Cu-0.02P, Sn-0.7Cu-0.005P were performed. Adding P in the solder alloys resulted in improvement of tensile strength, reduction of intermetallic compound growth, reduction of oxidization in fusible solders under wave soldering. After comparing solder alloy containing P with tin-lead eutectic solder alloy, P contained solders alloys showed much better solder properties than eutectic solder alloy. Furthermore, this solder alloy presented remarkable properties than any other lead-free solder alloy.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.2
• /
• pp.91-97
• /
• 2014

With Pb-free solder joints containing Sn-Ag-Cu-based ternary alloys (Sn-1.0 wt.%Ag-0.5Cu and Sn-4.0Ag-0.5Cu) and Sn-Ag-Cu-In-based quaternary alloys (Sn-1.0Ag-0.5Cu-1.0In, Sn-1.2Ag-0.5Cu-0.4In, Sn-1.2Ag-0.5Cu-0.6In, and Sn-1.2Ag-0.7Cu-0.4In), fracture-mode change, shear strengths, and fracture energies were observed and measured under a high-speed shear test of 500 mm/s. The samples in each composition were prepared with as-reflowed ones or solid-aged ones at $125^{\circ}C$ to 500 h. As a result, it was observed that ductile or quasi-ductile fracture modes occurs in the most of Sn-Ag-Cu-In samples. The happening frequency of a quasi-ductile fracture mode showed that the Sn-Ag-Cu-In joints possessed ductile fracture properties more than that of Sn-3.0Ag-0.5Cu in the high-speed shear condition. Moreover, the Sn-Ag-Cu-In joints presented averagely fracture energies similar to those of Sn-Ag-Cu joints. While maximum values in the fracture energies were measured after the solid aging for 100 h, clear decreases in the fracture energies were observed after the solid aging for 500 h. This result indicated that reliability degradation of the Sn-Ag-Cu-In solder joints might accelerate from about that time.

• Applied Science and Convergence Technology
• /
• v.23 no.6
• /
• pp.345-350
• /
• 2014

The surface oxidation mechanism of lead-free solder alloys has been investigated with multiple reflow using X-ray photoelectron spectroscopy. It was found that the solder surface of Sn-Ag-Cu-In solder alloy is surrounded by a thin $InO_x$ layer after reflow process; this coating protects the metallic surface from thermal oxidation. Based on this result, we have performed a wetting balance test at various temperatures. The Sn-Ag-Cu-In solder alloy shows characteristics of both thermal oxidation and wetting balance better than those of Sn-Ag-Cu solder alloy. Therefore, Sn-Ag-Cu-In solder alloy is a good candidate to solve the two problems of easy oxidation and low wettability, which are the most critical problems of Pb-free solders.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2003.09a
• /
• pp.147-163
• /
• 2003

European Union bans the usage of Pb in electronics from July 1 st, 2006. The Near-eutectic Sn-Ag-Cu alloys are the leading candidate Pb-free solders (for SMT card assembly). .The microstructure of Sn-Ag-Cu alloys is discussed in terms of solidification, composition and cooling rate. Methods of controlling Ag3Sn plates are discussed. .Thermo-mechanical fatigue behaviors of Sn-Ag-Cu solder joints are reviewed. Tin pest, whisker growth, electromigration of Pb-free solders are discussed.

• Proceedings of the KWS Conference
• /
• 2006.10a
• /
• pp.169-171
• /
• 2006

Solderability and reaction properties were investigated for four Pb-free alloys as a function of Ag contents; Sn-4.0Ag-0.5Cu, Sn-3.0Ag-0.5Cu, Sn-2.5Ag-0.5Cu, and Sn-1.0Ag-0.5Cu. The alloy of the lowest Ag content, i.e., Sn-1.0Ag-0.5Cu, showed poor wetting properties as the reaction temperature decreased to 230oC. Variation of Ag concentration in the Sn-xAg-0.5Cu alloy shifted exothermic peaks indicating the undercooling temperature in DSC curve. For the aging process at 170oC, the thickness of IMCs at the board-side solder/Cu interface increased with the Ag concentration.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.3
• /
• pp.130-134
• /
• 2018

In the past few years, various solder compositions have been a representative material to electronic packages and surface mount technology industries as a replacement of Pb-base solder alloy. Therefore, extensive studies on process and/or reliability related with the low Ag composition have been reported because of recent rapid rise in Ag price. In this study, Sn-3.0Ag-0.5Cu, Sn-0.7Cu and Sn-0.3Ag-0.5Cu solder bar samples were fabricated by melting of Sn, Ag and Cu metal powders. Crystal structure and element concentration were analyzed by XRD, XRF, optical microscope, FE-SEM and EDS. The fabricated solder samples were composed of ${\beta}-Sn$, ${\varepsilon}-Ag_3Sn$ and ${\eta}-Cu_6Sn_5$ phases.

• Journal of the Korean Society for Heat Treatment
• /
• v.20 no.6
• /
• pp.318-322
• /
• 2007

The high electrical conductivity Cu-0.15% Sn alloys containing various P contents, and the high conductivity and high strength Cu-0.1% Sn-0.1%Ag alloys with various Mg/P additions were fabricated and their mechanical properties and electrical conductivity were investigated. The electrical conductivity was generally decreased as the P content was increased where as the hardness and strength was shown to increase. When Mg was added to P-containing Cu alloys, the detrimental effect of P on the conductivity was significantly reduced, and TEM observations indicated that the formation of $Mg_3P_2$ phase is responsible for this result.