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

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1856-1863
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• 2004

In the last 50 years, lead-contained solder materials have been the most popular interconnect materials used in the electronics industry. Recently, lead-free solders are about to replace lead-contained solders for preventing environmental pollutions. However, the reliability of lead-free solders is not yet satisfactory. Several researchers reported that lead-contained solders have a good fatigue property. The others published that the lead-free solders have a longer thermal fatigue life. In this paper, the reason for the contradictory results published on the estimation of fatigue life of lead-free solder is investigated. In the present study, fatigue behavior of 63Sn37Pb, and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluating the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder ball joint in BGA packages. It was found that lead-free solder joints have a good fatigue property in the small temperature range condition. That condition induce small strain amplitude. However in the large temperature range condition, lead-contained solder joints have a longer fatigue life.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.74-82
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• 2000

The fluxless wetting properties of UBM-coated Si-wafer to the binary lead-free solders(Sn-Ag, Sn-Sb, Sjn-In, Sn0Bi) were estimated by wetting balance method. With the new wettability indices from the wetting curves of one side coated specimen, the wetting property estimation of UBM-coated Si-wafer was possible. For UBM of Si-chip, Au/Cu/Cr UBm was better than au/Ni/TI in the point of wetting time/ At general reflow process temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) was better than that of low melting point one(Sn-Bi, Sn-In). The contact angle of the one side coated Si-plate to the solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.47-53
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• 2000

The fluxless wetting properties of TSM-coated glass substrate were evaluated by the wetting balance method. We could estimate the wettability of the TSM with new parameters obtained from the wetting balance test for one side-coated specimen. It was more effective in wetting to use Cu as a wetting layer and Au as a protection layer than to use Au itself as a wetting layer. The SnSb solder showed better wettability than SnAg, SnBi, and SnIn solders. The contact angle of the one side-coated glass substrate to the Pb-free solders could be calculated from the farce balance equation by measuring the static force and the tilt angle.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.90-96
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• 2014

The conventional SnPb solders were widely used for several decades in the electronic packing system due to the superior mechanical properties such as low melting point, better wettavility and good mechanical fatigue. However, in recent years, owing to adverse effect on the human health and environment, conventional SnPb solders have been replaced by Lead-free solders. In this research, the shear punch(SP) test of Sn-4Ag-(Cu)/Ni pad was performed. Pb-free solder alloys which are the environmentally friendly of the electronic components were performed at $150^{\circ}C$ for 100hr~1000hr to artificial aging processing. In order to evaluate the mechanical properties of solder joints, the SP test was conducted at $30^{\circ}C$ and $50^{\circ}C$. As a result, the maximum shear strength of almost the whole specimens was decreased with the increase in aging time and temperature of SP test. The mechanical properties of Sn-4Ag-0.5Cu solder were most excellent in all Pb-free solder which were produced by the SP test at $30^{\circ}C$.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.750-760
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• 2002

In this study, three solders, Sn-37Pb, Sn-3.5Ag, and Sn-3.8Ag-0.7Cu were screen printed on both electroless Ni/Au and OSP metal finished micro-via PCBs (Printed Circuit Boards). The interfacial reaction between PCB metal pad finish materials and solder materials, and its effects on the solder bump joint mechanical reliability were investigated. The lead free solders formed a large amount of intermetallic compounds (IMC) than Sn-37Pb on both electroless Ni/Au and OSP (Organic Solderabilty Preservatives) finished PCBs during solder reflows because of the higher Sn content and higher reflow temperature. For OSP finish, scallop-like $Cu_{6}$ /$Sn_{5}$ and planar $Cu_3$Sn intermetallic compounds (IMC) were formed, and fracture occurred 100% within the solder regardless of reflow numbers and solder materials. Bump shear strength of lead free solders showed higher value than that of Sn-37Pb solder, because lead free solders are usually harder than eutectic Sn-37Pb solder. For Ni/Au finish, polygonal shaped $Ni_3$$Sn_4$ IMC and P-rich Ni layer were formed, and a brittle fracture at the Ni-Sn IMC layer or the interface between Ni-Sn intermetallic and P-rich Ni layer was observed after several reflows. Therefore, bump shear strength values of the Ni/Au finish are relatively lower than those of OSP finish. Especially, spalled IMCs at Sn-3.5Ag interface was observed after several reflow times. And, for the Sn-3.8Ag-0.7Cu solder case, the ternary Sn-Ni-Cu IMCs were observed. As a result, it was found that OSP finished PCB was a better choice for solders on PCB in terms of flip chip mechanical reliability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.186-190
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• 2023

We studied the various characteristics of Sn-In (wt%) Pb-free solders for photovoltaic ribbon application. The solders near the eutectic composition of Sn₄₈In₅₂ (wt%) existed in InSn₄ and In₃Sn alloy phases, and in In crystal phase, but not in Sn crystal phase. In addition, the InSn₄ phase (γ-alloy) existed separately from the In₃Sn (β-alloy) and the In phase confirmed by an SEM-EDS-mapping. The melting temperature of the eutectic solder of Sn₄₈In₅₂ (wt%) was 119.2℃, and when the Sn content decreased in reference to the eutectic composition, it slightly increased to 121.4℃, but when the Sn content increased, it remained almost constant at 119.1℃. The peel strength of the ribbon plated with the Sn₄₂In₅₈ (wt%) solder was 38.7 N/mm², and it tended to increase when the Sn content increased. The peel strength of the eutectic Sn₄₈In₅₂ (wt%) solder was 53.6 N/mm², and that of the Sn₅₁In₄₉ (wt%) solder was 61.6 N/mm² that was the highest.

• Journal of Welding and Joining
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• v.15 no.2
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• pp.36-42
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• 1997

In this paper, stability of initial strength at solder joint with lead free solders, such as Sn-In (52-48%) and Sn-Ag (96.5-3.5wt%) was studied. To obtain at solder joint with high quality, it is very important to control the temperature at the interface of solder joints. It is found that the thermal EMF (electro motive force) occurs betwee lead frame and copper pad on a substrate during reflow soldering process using heated tip. As a result of control the temperature at interface of solder joints, variation of initial strength at solder joint decreases from about $\pm40%$ to $\pm20%$, and it is realized Pb free soldering process using Sn/In and Sn-Ag solder paste.

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

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