Search results

This paper aims to identify a variety of binary system solders by alloying, and relevantly derive multiple system Pb-free solders from the former, attempting to replace the high temperature Sn-Pb solder.

The basis of the paper is the synthesis of previous studies. In terms of some binary high temperature solder alloys, such as Au-20Sn, Bi-2.5Ag, Sn-5Sb, Au-12.5Ge, Zn-6Al and Zn-Sn, taking the alloy phase diagram as the starting point, the melting characteristics, microstructure, mechanical properties, wetting ability and reliability of solder joint are analysed and the prospect is consequently indicated.

Based on the analysis of the six groups of Pb-free solders, the present binary system solder alloys, from the perspective of melting properties, mechanical properties, soldering or reliability of solder joint, rarely meet the comprehensive requirements of replacing the high-temperature Sn-Pb solder. It is assumed to be a solution that multiple-system Pb-free solders derive from a variety of binary system solders by means of alloying. The future development of high temperature Pb-free solder may focus on some factors such as physical properties, mechanical properties, processing, reliability of solder joint, environmental performance and expense.

The paper concentrates on the issue of Pb-free solders at high temperature. From a specific perspective of binary system solders, the presently available Pb-free solders are suggested from the starting point of the alloy phase diagram and the prospect of alternatives of Sn-Pb solders at high temperature are indicated.

To investigate effects of the thermal history on intermetallic thickness and morphology and on the resulting shear strength of the ball attachment for a variety of BGA components.

In this study, a variety of BGA components with balls made of Pb‐free Sn‐Ag‐Cu (SAC) 305, Sn‐Pb eutectic and high‐temperature 90Pb‐10Sn alloys, were subjected to different thermal histories, including up to ten reflow cycles, and aged at 125°C from 24 to 336 h. The intermetallic thickness and morphology after these thermal events were then examined under optical and scanning electronic microscopes. Ball shearing tests were conducted to investigate effects of the thermal history and intermetallic thickness and morphology on shearing strength of these solder balls.

The results show that effects directly from intermetallic layers may or may not be detectable; and the shear strength of solder balls is largely dependent on the solder alloy and its microstructure. Shear strength increases are observed after multiple reflow cycles and ageing at elevated temperature for the two Pb‐bearing alloys, while the SAC305 lead‐free alloy shows slight reductions in both strength and ductility after thermal exposure.

Presented results can be used for estimation of reliability for electronic assemblies subjected to multiple rework and repair operations, which expose sensitive components, such as BGAs, to elevated temperatures.

It is believed that a sound understanding of the effects of intermetallic morphology and thickness on reliability of BGA solder balls can lead to more intelligent choice of soldering processes, as well as to rework/repair process optimisation and to establishing their operational limits.

The aim of the present study was to gather and review all the important properties of the Sn–Ag–Cu (SAC) solder alloy. The SAC solder alloy has been proposed as the alternative solder to overcome the environmental concern of lead (Pb) solder. Many researchers have studied the SAC solder alloy and found that the properties such as melting temperature, wettability, microstructure and interfacial, together with mechanical properties, are better for the SAC solder than the tin – lead (SnPb) solders. Meanwhile, addition of various elements and nanoparticles seems to produce enhancement on the prior bulk solder alloy as well. These benefits suggest that the SAC solder alloy could be the next alternative solder for the electronic packaging industry. Although many studies have been conducted for this particular solder alloy, a compilation of all these properties regarding the SAC solder alloy is still not available for a review to say.

Soldering is identified as the metallurgical joining method in electronic packaging industry which uses filler metal, or well known as the solder, with a melting point < 425°C (Yoon et al., 2009; Ervina and Marini, 2012). The SAC solder has been developed by many methods and even alloying it with some elements to enhance its properties (Law et al., 2006; Tsao et al., 2010; Wang et al., 2002; Gain et al., 2011). The development toward miniaturization, meanwhile, requires much smaller solder joints and fine-pitch interconnections for microelectronic packaging in electronic devices which demand better solder joint reliability of SAC solder Although many studies have been done based on the SAC solder, a review based on the important characteristics and the fundamental factor involving the SAC solder is still not sufficient. Henceforth, this paper resolves in stating all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding.

Various Pb-free solders have been studied and investigated to overcome the health and environmental concern of the SnPb solder. In terms of the melting temperature, the SAC solder seems to possess a high melting temperature of 227°C than the Pb solder SnPb. Here, the melting temperature of this solder falls within the range of the average reflow temperature in the electronic packaging industry and would not really affect the process of connection. A good amendment here is, this melting temperature can actually be reduced by adding some element such as titanium and zinc. The addition of these elements tends to decrease the melting temperature of the SAC solder alloy to about 3°C. Adding nanoparticles, meanwhile, tend to increase the melting temperature slightly; nonetheless, this increment was not seemed to damage other devices due to the very slight increment and no drastic changes in the solidification temperature. Henceforth, this paper reviews all the properties of the Pb-free SAC solder system by how it is developed from overcoming environmental problem to achieving and sustaining as the viable candidate in the electronic packaging industry. The Pb-free SAC solder can be the alternative to all drawbacks that the traditional SnPb solder possesses and also an upcoming new invention for the future needs. Although many studies have been done in this particular solder, not much information is gathered in a review to give better understanding for SAC solder alloy. In that, this paper reviews and gathers the importance of this SAC solder in the electronic packaging industry and provides information for better knowledge.

This paper resolves in stating of all its important properties based on the SAC solder including its alloying of elements and nanoparticles addition for further understanding.

This paper aims to invastigate of the wetting and interfacial properties of Sn-(3-x)Ag-0.5Cu-(x)Bi (x = 0.5, 1 and 2 in Wt.%) Pb-free solder alloys at various temperatures ( 250, 280 and 310°C) on Cu substrate in Ar atmosphere.

In this study, new Sn-(3-x)Ag-0.5Cu-xBi systems, low Ag content quaternary lead-free solder alloys, were produced by adding 0.5, 1 and 2% Bi to the near-eutectic SAC305 alloy. The wetting angles of three new alloys, Sn-2.5Ag-0.5Cu-0.5 Bi(SAC-0.5 Bi), Sn-2Ag-0.5Cu-1Bi(SAC-1Bi) and Sn-1Ag-0.5Cu-2Bi(SAC-2Bi) were measured by sessile drop technique on the Cu substrate in argon atmosphere.

In accordance with the interfacial analyses, intermetallic compounds of Cu3Sn, Cu6Sn5, and Ag3Sn were detected at the SAC-Bi/Cu interface. The results of wetting tests show that the addition of 1 Wt.% Bi improves the wetting properties of the Sn-3Ag-0.5Cu solder. The lowest wetting angle (θ) was obtained as 35,34° for Sn-2Ag-0.5Cu-1Bi alloy at a temperature of 310 °C.

This work was carried out with our handmade experiment set and the production of the quaternary lead-free solder alloy used in wetting tests belongs to us. Experiments were conducted using the sessile drop method in accordance with wetting tests.

This study aims to study the impact of intermetallic compound on microstructure, mechanical characteristics and thermal behavior of the melt-spun Bi-Ag high-temperature lead-free solder.

In this paper, a new group of lead-free high-temperature Pb-free solder bearing alloys with five weight percentages of different silver additions, Bi-Ag_x (x = 3.0, 3.5, 4.0, 4.5 and 5.0 Wt.%) have been developed by rapidly solidification processing (RSP) using melt-spun technique as a promising candidate for the replacement of conventional Sn-37Pb common solder. The effect of the addition of a small amount of Ag on the structure, microstructure, thermal and properties of Bi-Ag solder was analyzed by means of X-ray diffractometer, scanning electron microscopy, differential scanning calorimetry and Vickers hardness technique. Applying the RSP commonly results in departures from conventional microstructures, giving an improvement of grain refinement. Furthermore, the grain size of rhombohedral hexagonal phase Bi solid solution and cubic IMC Bi_0.97Ag_0.03 phase is refined by Ag addition. Microstructure analysis of the as soldered revealed that relatively uniform distribution, equiaxed refined grains of secondary IMC Bi_0.97Ag_0.03 particles about 10 µm for Bi-Ag_4.5 dispersed in a Bi matrix. The addition of trace Ag led to a decrease in the solidus and liquidus temperatures of solder, meanwhile, the mushy zone is about 11.4°C and the melting of Sn-Ag_4.5 solder was found to be 261.42°C which is lower compared with the Sn-Ag₃ solder 263.60°C. This means that the silver additions into Bi enhance the melting point. The results indicate that an obvious change in electrical resistivity (?) at room temperature was noticed by the Ag addition. It was also observed that the Vickers microhardness (H_v) was increased with Ag increasing from 118 to 152 MPa. This study recommended the use of the Bi-Ag lead-free solder alloys for higher temperature applications.

Silver content is very important for the soldering process and solder joint reliability. Based on the present investigations described in this study, several conclusions were found regarding an evaluation of microstructural and mechanical deformation behavior of various Bi-Ag solders. The effect of Ag and rapid solidification on the melting characteristics, and microstructure of Bi-Ag alloys were studied. In addition, the mechanical properties of Bi with different low silver were investigated. From the present experimental study, the following conclusions can be drawn. The addition of Ag had a marked effect on the melting temperature of the lead-free solder alloys, it decreases the melting temperature of the alloy from 263.6 to 261.42°C. Bi-Ag solders are comprised of rhombohedral Hex. Bi solid solution and cubic Ag_0.97Bi_0.03 IMC is formed in the Bi matrix. The alloying of Ag could refine the primary Bi phase and the Bi_0.97Ag_0.03 IMC. With increasing Ag content, the microstructure of the Bi-Ag gradually changes from large dimples into tiny dimple-like structures. The refinement of IMC grains was restrained after silver particles were added into the matrix. The inhibition effect on the growth of IMC grains was most conspicuous when solder was doped with Ag particles. As a result, the Vickers microhardness of the Bi-Ag lead-free solder alloys was enhanced by more than 100% ranging from 118.34 to 252.95 MPa. Bi-Ag high-temperature lead-free solders are a potential candidate for replacing the tin-lead solder (Sn-37Pb) materials which are toxic to human and the environment and has already been banned.

This study recommended the use of the Bi-Ag lead-free solder alloys for high-temperature applications.

The purpose of this paper is to enhance the understanding on the electrodeposition of various lead (Pb)‐free solder alloys, so that new studies can be carried out to solve processing issues.

The paper reviews the available reports on the electrodeposition of tin (Sn)‐based solder systems and identifies the challenges in this area.

Compositional control remains a major challenge in this area, where the achievement of desired composition for binary and ternary alloys is subjected to uncertainties. The use of chelating agents in the bath and optimization of parameters can assist the achievement of near‐desired alloy composition. Acidic plating baths are preferred due to their compatibility with photoresists but oxidation of stannous ions causes poor bath stability. Antioxidants, reducing agents and low oxygen overpotential anodes can suppress the oxidation rate and increase the lifespan of plating baths. Apart from chelating agents and antioxidants, various categories of additives can be added to improve quality of deposits. Surfactants, grain refiners and brighteners are routinely used to obtain smooth, fine‐grained and bright deposits with good thermo‐mechanical properties.

The paper provides information on the key issues in electrodeposition of Pb‐free solder alloys. Possible measures to alleviate the issues are suggested so that the electrodeposition technique can be established for mass production of a wider range of solder alloys.

Eutectic Sn‐Ag solder is being considered as a potential replacement for Sn‐Pb solders. A potential drawback to using the eutectic Sn‐Ag solder is its higher melting point, 221°C, compared with the eutectic Pb‐Sn solder. Owing to its higher melting temperature, the eutectic Sn‐Ag solder is also being considered for automotive under‐the‐hood applications, which experience high temperature environments. Electronic components and/or circuit boards are often coated with Pb‐bearing solder to facilitate soldering operations. Soldering Pb‐bearing solder coated components and/or boards with eutectic Sn‐Ag solder will result in joints contaminated with Pb. In this study, the effects of Pb contamination on eutectic Sn‐Ag solder joints were investigated using three ternary alloys made by incorporating some Pb into eutectic Sn‐Ag solder. These ternary alloys all showed a peak at 178°C in heating curves obtained using Differential Scanning Calorimetry (DSC), which resulted from the ternary eutectic composition in the Sn‐Ag‐Pb system. The Pb phases in the ternary alloys were found to be dispersed throughout the microstructure. A practical implication of Pb contamination in eutectic Sn‐Ag solder joints is that the service temperature of such joints would be limited by the lower melting temperature of the ternary eutectic phase.

This paper aims to investigate the effect of In and Sb additions on the thermal behavior and wettability of Sn-3.5Ag-xIn-ySb (x = 0, 1.0 and 1.5 Wt.%, y = 0, 1.0, 1.4 and 2.1 Wt.%) solder alloys.

The thermal behavior of the Pb-free solder alloys was studied using differential scanning calorimetry. Wetting balance experiments were performed in accordance with the IPC standard, IPC-TM-650 and at a temperature of 260°C. Also, a solder spread test was performed on a Cu surface finish using the JIS-Z-3197 solderability standard.

It is shown that among the selected Sn-3.5Ag-xIn-ySb (x = 0, 1.0 and 1.5 Wt.%, y = 0, 1.0, 1.4 and 2.1 Wt.%) alloys, Sn-3.5Ag-1.5In-1Sb showed the lowest melting point and the lowest undercooling temperature. The best wettability was achieved when the In and Sb contents were approximately 1.5 and 1.0 Wt.%, respectively. The effect of the combined addition of In and Sb on solder spreadability on a Cu substrate was also demonstrated.

It was found that adding approximately 1.5 and 1.0 Wt.% of In and Sb, respectively, in Sn-3.5Ag solder provided the best wetting performance and improved the solder spreadability.

The purpose of the present work is to study the impacts of rapid cooling and Tb rare-earth additions on the structural, thermal and mechanical behavior of Bi–0.5Ag lead-free solder for high-temperature applications.

Effect of rapid solidification processing on structural, thermal and mechanical properties of Bi-Ag lead-free solder reinforced Tb rare-earth element.

The obtained results indicated that the microstructure consists of rhombohedral Bi-rich phase and Ag99.5Bi0.5 intermetallic compound (IMC). The addition of Tb could effectively reduce the onset and melting point. The elastic modulus of Tb-containing solders was enhanced to about 90% at 0.5 Tb. The higher elastic modulus may be attributed to solid solution strengthening effect, solubility extension, microstructure refinement and precipitation hardening of uniform distribution Ag99.5Bi0.5 IMC particles which can reasonably modify the microstructure, as well as inhibit the segregation and hinder the motion of dislocations.

It is recommended that the lead-free Bi-0.5Ag-0.5Tb solder be a candidate instead of common solder alloy (Sn-37Pb) for high temperature and high performance applications.

This paper aims to develop a fuzzy logic-based algorithm to predict the intermetallic compound (IMC) size and mechanical properties of soldering material, Sn96.5-Ag3.0-Cu0.5 (SAC305) alloy, at different levels of temperature. The reliability of solder joint in materials selection is critical in terms of temperature, mechanical properties and environmental aspects. Owing to a wide range of soldering materials available, the selection space finds a fuzzy characteristic.

The developed algorithm takes thermal aging temperature for SAC305 alloy as input and converts it into fuzzy domain. These fuzzified values are then subjected to a fuzzy rule base, where a set of rules determines the IMC size and mechanical properties, such as yield strength (YS) and ultimate tensile strength (UTS) of SAC305 alloy. The algorithm is successfully simulated for various input thermal aging temperatures. To analyze and validate the developed algorithm, an SAC305 lead (Pb)-free solder alloy is developed and thermally aged at 40, 60 and 100°C temperature.

The experimental results indicate an average IMCs size of 5.967 (in Pixels), 19.850 N/mm² YS and 22.740 N/mm² UTS for SAC305 alloy when thermally aged at an elevated temperature of 140°C. In comparison, the simulation results predicted 5.895 (in Pixels) average IMCs size, 19.875 N/mm² YS and 22.480 N/mm² UTS for SAC305 alloy at 140°C thermally aged temperature.

From the experimental and simulated results, it is evident that the fuzzy-based developed algorithm can be used effectively to predict the IMCs size and mechanical properties of SAC305 at various aging temperatures, for the first time.