Nanocomposite Solder Research Articles

Electrochemical migration and corrosion behaviours of SAC305 reinforced by NiO, Fe2O3, TiO2 nanoparticles in NaCl solution

Pb-free solders incorporated with nano-sized particles have been identified, as potential Pb-free nanocomposite solders that could provide higher microstructure stability and better mechanical properties than the conventional solders. Nowadays, the miniaturizations of electronic devices increase in their usage have increased the risk of failure due to ion migration and corrosion phenomena. This research investigates the effects the electrochemical migration (ECM) and corrosion behaviour of Sn- 3.0Ag-0.5Cu (SAC305) reinforced by NiO, Fe2O3 and TiO2 nanoparticles in 0.1M NaCl solution. The SAC305 solder alloys were doped with different percentages of NiO, Fe2O3 and TiO2 at nominal percentages of 0.01, 0.05 and 0.15 wt% in producing nanocomposite solder paste. Then, the solder paste has flowed in the reflow oven at the temperature of 240°C. After that, the Water Drop Test (WDT) was performed using 0.1 M NaCl solution to investigate the ion migration behaviour and Potentiodyamic Tafel Polarization technique to determine the corrosion behaviour on the solder alloys. In general, the results showed the mean-time-to-failure (MTTF) of SAC305 solder alloy increased when added of the nanoparticles of NiO, Fe2O3 and TiO2. Besides, SAC305-TiO2 has the longest MTTF in 0.1 M NaCl solution followed by SAC305-Fe2O3 and SAC305-NiO nanoparticles. This results is believed due to the presence of nanoparticles as the alloying element in the solder that hinder the process of ECM to suppress the growth of the dendrites accelerating for the short circuit occurs and causes the failure of the IPC-24 test board. The potentiodynamic polarization curve results exhibit the SAC305 with nanoparticles decreased the corrosion rate compared with SAC305 solder alloy only. SAC305 with NiO and TiO2 have slightly lower corrosion rates compared with Fe2O3 nanoparticles. Therefore, SAC305 reinforced by TiO2, Fe2O3 and NiO nanoparticles exhibited excellent ECM and corrosion resistance behaviours in the 0.1 M NaCl solution.

Mechanical, electrical, and thermal reliability of Sn-58wt.%Bi solder joints with Ag-decorated MWCNT for LED package component during aging treatment

The effect of aging on reliability of Sn-58 wt%Bi solder joint with Ag-decorated multi-walled carbon nanotubes (Ag-MWCNTs) was investigated for the LED package components. The mechanical, electrical and thermal characteristics of the solder joints with various Ag-MWCNT contents were examined under aging treatment. Ag-MWCNTs were synthesized by using a colloidal method and the nanocomposite solder paste was fabricated by mechanically mixing the Ag-MWCNTs with Sn-58 wt%Bi solder paste. The flip-chip light emission diode (FC-LED) package component was bonded on the substrate with Cu pad finished organic solderability preservative (OSP). And then these were isothermally aged at 85 °C up to 1000 h in an oven. The mechanical, electrical and thermal property of solder joints was evaluated by using shear test, measuring the electrical resistance and thermal transient test, respectively. The bonding strength of all of the solder joints decreased and the electrical resistance of the solder joints increased with increasing aging time. The bonding strength of the solder joints with 0.05Ag-MWCNTs was 12% higher than those of other solder joints. And the electrical and thermal resistance of the solder joints exhibited the lowest resistance with 0.1Ag-MWCNTs and 0.05Ag-MWCNTs after aging for 1000 h, respectively.

Effect of Cu6Sn5 nanoparticles size on the properties of Sn0.3Ag0.7Cu nano-composite solders and joints

The effect of different-sized Cu6Sn5 nanoparticles on thermal behavior and interfacial reaction with Cu substrate of Sn–0.3Ag–0.7Cu solder was evaluated. The results showed that 30 nm and 70 nm Cu6Sn5 nanoparticles were successfully synthesized by using the method of different reductants, attributed to the difference of reductive ability. Under condition of the same heating parameters, 30 nm Cu6Sn5 nanoparticle owned lower sintering temperature than that of 70 nm Cu6Sn5 nanoparticle. The thermal behavior was revealed that the composite solders with the addition of different-sized Cu6Sn5 nanoparticles had slightly lower melting point and higher undercooling value, compared with original Sn–0.3Ag–0.7Cu solder alloy. The highest undercooling value occurred with 30 nm Cu6Sn5 nanoparticle addition. Moreover, the interfacial reactions between Cu substrate and Sn–0.3Ag–0.7Cu solders mixed with different-sized Cu6Sn5 nanoparticles have produced after reflowing at 250 °C and aging at 150 °C for different interval time. It was clearly found that comparing to the initial Sn–0.3Ag–0.7Cu/Cu solder joint, the thickness of interfacial intermetallic compound (IMC) layer on solder joint with adding nanoparticle was thinner and the growth rate was slower. The growth of interfacial IMC was suppressed with the addition of Cu6Sn5 nanoparticle, and 30 nm Cu6Sn5 nanoparticle had the strongest inhibition effect on the growth of IMC, as well as the growth of IMC grains.

Thermal and mechanical property of FCLED package component interconnected with Sn–MWCNT composite solder

Flip-chip light-emitting diode (FCLED) packages were interconnected with various contents of Sn-decorated multi-walled carbon nanotube (Sn–MWCNT) composite solder. The Sn–MWCNT was synthesized with a Sn solution using polyol to decorate Sn nanoparticle on the surface of MWCNTs. The Sn-58Bi solder pastes containing Sn–MWCNTs were printed on the metal-printed circuit boards, and then bonded with a flip-chip bonder. The mechanical property of FCLED packages with various contents of Sn–MWCNTs were evaluated with a bond tester. Thermal property was measured with IR Camera and laser flash analysis. The shear strength of an LED chip with 0.1 wt% Sn–MWCNT solder increased about 25% over that without Sn–MWCNT. The LED chip temperature with 0.1 wt% Sn–MWCNT nanocomposite solder decreased about 7% compared to that of the Sn-58Bi solder.

Lead-free Sn-based/MW-CNTs nanocomposite soldering: effects of reinforcing content, Ni-coating modification, and isothermal ageing treatment

In this article, soldering of sheet-form copper substrates in a lap-joint design by using the newly developed lead-free nanocomposite solders based on the ternary eutectic system of Sn–3.5Ag–0.7Cu (in wt%) alloy reinforced with multi-walled carbon nano-tubes (MW-CNTs) was assessed. Different weight percentages of MW-CNTs (0.05, 0.1, 0.15, and 0.2 wt%) were incorporated within the SAC solder matrix by using the powder mixture system and employing of mechanical alloying (MA) processing route. The main object was controlling the formation morphology and growth kinetics of intermetallic compounds (IMCs) layer at the interface with the Cu substrate during soldering process. Also, to improve the compatibility of reinforcing MW-CNTs and solder alloy, decoration of nickel particles on the surface of nanotubes by using the electroless plating system was considered. The results showed that by increasing the amount of reinforcing nanotubes and implementation of Ni-coating on the surface of MW-CNTs, the thickness of IMC layer at the interface between Cu substrate and solder alloy is continuously refined. This important issue yielded to a continuous and significant improvement of tensile strength up to ~ 50%, as compared to the un-reinforced SAC solder alloy, despite of considerable ductility reduction. In following, the influence of post isothermal ageing treatment at a temperature of 150 °C with a holding time up to ~ 100 h on the microstructural characteristics and mechanical property of the soldered joints was elaborated. Employing of such isothermal ageing treatment revealed very effective in more elevating the mechanical strength of soldered joints (to attain the tensile strength of up to ~ 30 MPa). Furthermore, a simultaneous improvement of the elongation to failure more than ~ 22% was noted caused by increasing the thickness of the IMC layer at the interface. To this end, acceleration in the solid-state diffusion of elements played the main role.

Coupling effects of rare-earth Pr and Al2O3 nanoparticles on the microstructure and properties of Sn-0.3Ag-0.7Cu low-Ag solder

Low-cost Al2O3 nanoparticles (NPs) are regularly incorporated into lead-free solder to improve its mechanical performance, but the poor wettability of Al2O3 NPs leads to weak Al2O3/solder interface bonding. In this work, a novel idea different from the common solution of pre-coating a metal layer on the surface of NPs was proposed to address the issue of weak interface bonding by simultaneously doping rare-earth (RE) Pr (0.06 wt%) and Al2O3 NPs (0–0.5 wt%) into Sn-0.3Ag-0.7Cu low-Ag solder. The coupling effects of RE Pr and Al2O3 NPs on the wettability, microstructures, shear force and creep resistance of prepared nanocomposite solder were systematically investigated. It was found that the coupling effects were concentration dependent. When the content of Al2O3 NPs was less than 0.06 wt%, a synergistic relationship between free Pr atoms and Al2O3 NPs was established. This is because the surface-active Pr atoms, acting as bridges between Al2O3 NPs and solder matrix, can be spontaneously adsorbed at the surfaces of Al2O3 NPs to in situ form Pr-coated Al2O3 NPs, which have much better wettability than the single Al2O3 NPs. However, increasing the doping content of Al2O3 NPs over 0.06 wt% led to a competitive relationship among free Pr atoms, Al2O3 NPs and Pr-coated Al2O3 NPs, which was probably caused by the emerged Al2O3 agglomerates occupying partial space of grain surfaces. The optimum doping content of Al2O3 NPs in SAC0307–0.06Pr solder was approximately 0.06 wt% and SAC0307–0.06Pr-0.06Al2O3 possessed the best wettability, a well-controlled growth of interfacial IMC layer, the highest shear force (∼61 N) and a superior room-temperature creep resistance with creep stress exponent (n) reaching approximately 11.7.

Development of Pb-Free Nanocomposite Solder Alloys

As an alternative to conventional Pb-containing solder material, Sn–Ag–Cu (SAC) based alloys are at the forefront despite limitations associated with relatively poor strength and coarsening of grains/intermetallic compounds (IMCs) during aging/reflow. Accordingly, this study examines the improvement of properties of SAC alloys by incorporating nanoparticles in it. Two different types of nanoparticles were added in monolithic SAC alloy: (1) Al2O3 or (2) Fe and their effect on microstructure and thermal properties were investigated. Addition of Fe nanoparticles leads to the formation of FeSn2 IMCs alongside Ag3Sn and Cu6Sn5 from monolithic SAC alloy. Addition of Al2O3 nano-particles do not contribute to phase formation, however, remains dispersed along primary β-Sn grain boundaries and act as a grain refiner. As the addition of either Fe or Al2O3 nano-particles do not make any significant effect on thermal behavior, these reinforced nanocomposites are foreseen to provide better mechanical characteristics with respect to conventional monolithic SAC solder alloys.

Investigation on nano-reinforced solder paste after reflow soldering part 1: Effects of nano-reinforced solder paste on melting, hardness, spreading rate, and wetting quality

In this study, the effects of three distinctive contents of metal oxide [Iron Nickel Oxide (Fe2NiO4), Iron Oxide (Fe2O3), Nickel Oxide (NiO), and Indium Tin Oxide (ITO)] and carbon nanostructure [diamond (C)]-reinforced solder paste on melting behavior, hardness, spreading rate, and wetting angle after reflow soldering were differentiated. Each nanoparticle was mechanically mixed with SAC 305 solder paste to produce homogeneous nanocomposite solder alloys. Based on the results, the addition of nanoparticles slightly increased the melting point; except for the SAC 305-ITO and SAC 305-Diamond composite solder pastes. The SAC 305-ITO composite solder showed negligible effects, but the SAC 305-Diamond composite solder reduced the melting point. The SAC 305-Diamond composite solder exhibited a very high increment in solder hardness compared with other nanocomposite solder pastes. Reinforcement of 0.5 wt% diamond nanoparticles increased solder viscosity higher than other metal oxide nanoparticles. The flow rate of SAC 305-Diamond molten solder on Cu substrate decreased upon the nanoparticle addition during reflow soldering. The reduction in the spreading caused the enlargement in the wetting angle of solder paste. However, very low percentage of carbon nanostructure addition into molten solder alloys reduced the melting point and increased solder hardness with tolerable spreading rate and wetting quality, which enhanced solder reliability after reflow.

Effects of α-Al2O3 nanoparticles-doped on microstructure and properties of Sn–0.3Ag–0.7Cu low-Ag solder

In order to enhance the properties of Sn–0.3Ag–0.7Cu low-Ag solder, α-Al2O3 nanoparticles with various content (0–0.5 wt%) were successfully doped into the solder paste with a self-designed dispersion step. After comprehensive study of the microstructures and properties of the novel nano-composite solder, several satisfactory modified results can be obtained. For instance, the wettability of solder was greatly improved with trace amount of α-Al2O3 nanoparticles-doped. The superior wettability was achieved by Sn–0.3Ag–0.7Cu–0.12Al2O3 solder with spreading area approaching to ~ 79 mm2. Detailed thermodynamic and kinetic analysis of how α-Al2O3 nanoparticles promoting the processes of solder wetting and spreading on Cu substrate were given. In addition, the joint soldered with Sn–0.3Ag–0.7Cu–0.12Al2O3 displayed the highest shear force (57.1 N) with a typical ductile fracture failure mode. This relates to the evidently refined microstructure as well as the well-controlled growth of interfacial Cu6Sn5 IMCs. Corresponding theoretical analysis shows 0.12 wt% Al2O3 nanoparticles-doped can decrease the growth rate constant of interfacial Cu6Sn5 IMCs from 5.08 × 10−10 to 1.71 × 10−10 cm2/s.

Influence of dual ceramic nanomaterials on the solderability and interfacial reactions between lead-free Sn-Ag-Cu and a Cu conductor

This study examined the addition of dual ceramic nanomaterials, TiO2 and graphene (0, 0.03, 0.12, 0.21, and 0.60 wt %), to a lead-free Sn-3.0 wt %Ag-0.5 wt %Cu (SAC305) solder alloy. TiO2 and graphene nanomaterials were mixed simultaneously at equal weight fractions into the SAC305 molten solder by mechanical mixing and melting to produce a bulk nanocomposite solder. The effects of the dual nanomaterials on the melting point, microstructure, solderability, and intermetallic compound (IMC) growth were conducted. The structural and morphological features of the samples were characterized by field emission scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy. In addition, the melting behavior of the nanocomposite solder was characterized by differential scanning calorimetry. The nanocomposite solder with 0.21 wt % nanomaterials showed 33.67% enhancement in wettability and an 8.66% increase in spreadability due to the increased fluidity and decreased surface tension of molten solder in the presence of dual nanomaterials. In addition, the thickness of the IMCs was reduced after adding the dual nanomaterials to the monolithic SAC alloy. The optimal concentration of the dual nanomaterials in the monolithic SAC alloy was found to be 0.21 wt %.

Effects of nanoparticles on the thermal, microstructural and mechanical properties of novel Sn3.5Ag0.5Zn composite solders

The effects of added nanoparticles (i.e., Al2O3 and TiO2) on the thermal, microstructural and mechanical properties of Sn3.5Ag0.5Zn nanocomposite solders have been investigated. Adding nanoparticles to the Sn3.5Ag0.5Zn solder increases the melting temperature by only 2.1–4.6 °C. It was also confirmed that the nanoparticles affect the microstructural and mechanical properties. The UTS, 0.2 YS, and microhardness of the Sn3.5Ag0.5Zn nanocomposite solder improved, which could be attributed to the refinement of the β-Sn grain size, the precipitation of Ag3(Sn, Zn) grains, and the second phase dispersion strengthening mechanism. The fracture mechanism of Sn3.5Ag0.5Zn nanocomposite solders was confirmed to be the ductile fracture mode. The cracks were initiated at the interfaces between β-Sn(Zn) grains and Ag(Zn, Sn) phases.

Lead free Sn-Ag-Cu solders reinforced by Ni-coated graphene nanosheets prepared by mechanical alloying: Microstructural evolution and mechanical durability

As one of the key technologies for high performance electronic devices, composite solders have been developed to improve the thermal and mechanical properties of soldered joints. In this research, mechanical alloying was employed to fabricate the lead-free tin-based nanocomposite solders. The nanocomposite composed of a Sn-Ag-Cu ternary eutectic alloy reinforced by graphene nano-sheets (GNSs). Since the tin alloy melt do not wet the surfaces of GNSs, interface bonding between the metal matrix and these inclusions was promoted with decorating of the nano-sheets by a thin layer of chemically-deposited nickel. It was shown that nickel coating significantly improves the distribution of GNSs throughout the SAC matrix prepared by the severe plastic deformation route. Additionally, brittle and elongated intermetallic compounds were significantly refined to distribute the particles with an average diameter of a few hundred nanometers. Microstructural studies also revealed a recrystallized fine-grained and eutectic morphology for the SAC alloy matrix before and after soldering, respectively. The role of Ni-coated GNSs on retarding the growth of intermetallic phases upon soldering process is presented. We have employed a solid-state post ageing process to enhance the mechanical properties of the developed soldered joints by precipitation hardening mechanism assisted by nano-sheets, as well. Enhanced strength and ductility of the copper soldered joints prepared by the nanocomposite solder is shown. A maximum enhancement of ~ 65% in the tensile-shear strength is reported, while the ductility preserved up to ~ 63%, as well.

Effects of AlN Nanoparticles on the Microstructure, Solderability, and Mechanical Properties of Sn-Ag-Cu Solder

The addition of nanosized AlN particles to Sn-3.0 wt pctAg-0.5 wt pctCu (SAC305) lead-free solder alloy has been investigated. The various weight fractions of AlN (0, 0.03, 0.12, 0.21, 0.60 wt pct) have been dispersed in SAC305 solder matrix by a mechanical mixing and melting route. The influences of AlN nanosized particles on the microstructure, mechanical properties, and solderability (e.g., spreadability and wettability) have been carried out. The structural and morphological features of the nanocomposite solder were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscope (TEM). The experimental results show that the best combination of solderability and mechanical properties is obtained at 0.21 wt pct AlN in the solder matrix. The reinforced composite solder with 0.21 wt pct AlN nanoparticles shows ≈25 pct improvement in ultimate tensile strength (UTS), and ≈4 pct increase in the spreadability. In addition, the results of microstructural analyses of composite solders indicate that the nanocomposite solder, especially reinforced with 0.21 wt pct of AlN nanoparticles, exhibits better microstructure and improved elongation percentage, compared with the monolithic SAC305 solder.

Effects of Metallic Nanoparticles on Interfacial Intermetallic Compounds in Tin-Based Solders for Microelectronic Packaging

Tin (Sn)-based solders have established themselves as the main alternative to the traditional lead (Pb)-based solders in many applications. However, the reliability of the Sn-based solders continues to be a concern. In order to make Sn-based solders microstructurally more stable and hence more reliable, researchers are showing great interest in investigating the effects of the incorporation of different nanoparticles into them. This paper gives an overview of the influence of metallic nanoparticles on the characteristics of interfacial intermetallic compounds (IMCs) in Sn-based solder joints on copper substrates during reflow and thermal aging. Nanocomposite solders were prepared by mechanically blending nanoparticles of nickel (Ni), cobalt (Co), zinc (Zn), molybdenum (Mo), manganese (Mn) and titanium (Ti) with Sn-3.8Ag-0.7Cu and Sn-3.5Ag solder pastes. The composite solders were then reflowed and their wetting characteristics and interfacial microstructural evolution were investigated. Through the paste mixing route, Ni, Co, Zn and Mo nanoparticles alter the morphology and thickness of the IMCs in beneficial ways for the performance of solder joints. The thickness of Cu3Sn IMC is decreased with the addition of Ni, Co and Zn nanoparticles. The thickness of total IMC layer is decreased with the addition of Zn and Mo nanoparticles in the solder. The metallic nanoparticles can be divided into two groups. Ni, Co, and Zn nanoparticles undergo reactive dissolution during solder reflow, causing in situ alloying and therefore offering an alternative route of alloy additions to solders. Mo nanoparticles remain intact during reflow and impart their influence as discrete particles. Mechanisms of interactions between different types of metallic nanoparticles and solder are discussed.

Effect of nano-Cu addition on microstructure evolution of Sn0.7Ag0.5Cu-BiNi/Cu solder joint

PurposeThe purpose of this paper is to focus on the fabrication of SnAgCu (SAC) nanocomposites solder and study the effect of Cu nanopowders (nano-Cu) addition on the microstructure evolution of resultant nanocomposite solder after reflow and thermal aging.Design/methodology/approachMechanical mixing is used in this work to incorporate nanoparticles into the solder and produce more homogeneous mixture. Standard metallographic procedures are applied for microstructural analysis of solder joints.FindingsIt is found that nano-Cu doped into Sn0.7Ag0.5Cu-BiNi solder has no appreciable influence on melting temperature of the composite solder. The addition of Cu nanoparticles refines the microstructure of bulk solder and suppresses the growth of interfacial intermetallic compound (IMC) layers. However, interfacial IMC grain size increases slightly after 1.0 per cent nano-Cu added.Originality/valueThe paper demonstrates a method of nano-composite solder paste preparation by means of mechanical mixing and a comparison study of the microstructure evolution of composite solder with the basic SAC solder.

Synthesis and characterization of ceramic nanoparticles reinforced lead-free solder

Sn-0.7Cu is among the least expensive types of lead-free solders available. However, its poor mechanical properties have limited its application. In this study, Sn-Cu lead-free solder reinforced with amorphous silica (SiO2) nanoparticles was synthesized through powder metallurgy route. Desired mixtures of raw materials was mechanically milled, compressed, sintered and extruded to prepare bulk solder samples. The samples were characterized by optical and electron microscopy as well as mechanical tests. The results showed that mechanical properties were increased by addition of SiO2 nanoparticles to the solder matrix. Addition of 1.5wt% ceramic reinforcement to the composite increased tensile, yield and compressive strengths up to 27%, 23% and 41%, respectively, compared to those of the monolithic sample. In addition, the ceramic nanoparticles caused an up to 50% decrease in the wetting angle between the substrate and the nanocomposite solder.

Effects of nano-copper particles on the properties of Sn58Bi composite solder pastes

PurposeThis paper aimed to investigate the effects of nano-copper particles on the melting behaviors, wettability and defect formation mechanism of the Sn58Bi composite solder pastes.Design/methodology/approachIn this paper, the mechanical stirring method was used to get the nano-composite solder pastes.FindingsExperimental results indicated that the addition of 3 wt.% (weight percentage) 50 nm copper particles showed limited effects on the melting behaviors of the Sn58Bi composite solder paste. The spreading rate of the Sn58Bi composite solder paste showed a decreasing trend with the increase of the weight percentage of 50 nm copper particles from 0 to 3 wt.%. With the addition of copper particles of diameters 50 nm, 500 nm or 6.5 μm into the Sn58Bi solder paste, the porosities of the three types of solder pastes showed a similar trend. The porosity increased with the increase of the weight percentage of copper particles. Based on the experimental results, a model of the void formation mechanism was proposed. During reflow, the copper particles reacted with Sn in the matrix and formed intermetallic compounds, which gathered around the voids produced by the volatilization of flux. The exclusion of the voids was suppressed and eventually led to the formation of defects.Originality/valueThis study provides an optimized material for the second and third level packaging. A model of the void formation mechanism was proposed.

Use of Indocyanine Green in Nanocomposite Solders to Increase Strength and Homogeneity in Laser Welding of Tendons

The ability to form sutures in bovine tendon using a prototype laser biological tissue welding device was demonstrated. New solder compositions are proposed, based on carbon nanotubules (0.1% w/w) in an aqueous matrix of bovine serum albumin (25% w/w) supplemented with the medical laser dye indocyanine green (0.01% w/w). The absorption peak of the nanocomposition solder coincided with the apparatus wavelength of 800 nm. The use of indocyanine green as radiation absorber in nanocomposition solders provided increases in the strength of laser weld sutures in tendons. The maximum level of ~0.82 MPa was achieved using a solder based on multiwalled carbon nanotubules. X-Ray microtomography demonstrated uniformity in the joining of tendons in depth and length during formation of nanocomposite between the two welded biological tissue fragments. Growth of fibroblast cells on the composite surface formed at the site of the laser weld suture was demonstrated.

Reliability enhancement of Sn-1.0Ag-0.5Cu nano-composite solders by adding multiple sizes of TiO2 nanoparticles

This paper demonstrates a novel low silver content TiO2 nanoparticle composite solder alloys, and discusses the TiO2 size effect on reliability of the solder and its solder joints with copper. 6 nm and 20 nm TiO2 nanoparticles were synthesized and added into Sn-1.0Ag-0.5Cu (SAC105) solder to prepare the nano-composite solders. The microstructure, coefficient of thermal expansion of the solders, and the shear strength, interfacial intermetallic compound growth of the solder joints under thermal cycling (1000 cycles) between −55 °C and 125 °C were investigated. The experimental results show that TiO2 nanoparticles can refine β-Sn grain size, decrease CTE of the solders, as well as suppress the interfacial intermetallic compound formation and growth. Also, after thermal cycling, the nano-composite solder joints have higher shear strength than the joints without TiO2 nanoparticles. Most importantly, smaller TiO2 nanoparticles (6 nm) shows larger influence on the respects of microstructure refinement, coefficient of thermal expansion reduction, interfacial IMC thickness decrease, and shear strength enhancement of the solder joints. The TiO2 nano-composite solder joints show higher electrical reliability than the original SAC105 solder joint according to the results of electric resistance change during thermal cycling.

Effect of alumina nanoparticles on the microstructure and mechanical durability of meltspun lead-free solders based on tin alloys

As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this research, melt spinning was employed to fabricate a lead-free based nanocomposite solder for electronic application materials via introducing Ni-coated Al2O3 nanoparticles (0.1 wt%) into a Sn-Ag-Cu ternary eutectic alloy during rapid solidification. These surface-modified nanoparticles were synthesized by an in situ chemical reduction method. The effect of rapid solidification on the distribution of reinforcing nanoparticles, microstructural evolution, and solderability of the tin alloy were studied. Microstructural studies determined that rapid solidification refined brittle and elongated intermetallic compounds (IMCs) into small particles with an average diameter of a few hundred nanometers. The particles were uniformly dispersed into an amorphous/recrystallized fine-grained eutectic morphology of the solder matrix. It was also found that the addition of Ni-coated Al2O3 nanoparticles could effectively suppress the growth of IMC layers, which enhanced the reliability of solder joints. Effects of solid-state ageing phenomenon on the tensile and shear properties of the soldered joints were also evaluated. Higher strength and ductility was measured for joints prepared from the nanocomposite solder as compared with the unreinforced solder. A maximum enhancement of ∼20% in the shear strength was obtained.