Low Melting Temperature Solder Materials for Use in Flexible Microelectronic Packaging Applications

The increasing application of heat-sensitive microelectronic components such as a multitude of transistors, polymer-based microchips, and so on, and flexible polymer substrates including polyethylene terephthalate (PET) and polyimide (PI), among others, for use in wearable devices has led to the development of more advanced, low melting temperature solders (<150°C) for interconnecting components in various applications. However, the current low melting temperature solders face several key challenges, which include more intermetallic compound formation (thus become more brittle), cost issues according to the addition of supplementary elements to decrease the melting point temperature, an increase in the possibility of thermal or popcorn cracking (reliability problems), and so on. Furthermore, the low melting temperature solders are still required to possess rapid electronic/electrical transport ability (high electrical conductivity and current density) and accompany strong mechanical strength sustaining the heavy-uploaded microelectronic devices on the plastic substrates, which are at least those of the conventional melting temperature solders (180–230°C). Thus, the pursuit of more advanced low melting temperature solders for interconnections is timely. This review is devoted to the research on three methods to improve the current properties (i.e., electrical and thermomechanical properties) of low melting temperature solders: (i) doping with a small amount of certain additives, (ii) alloying with a large amount of certain additives, and (iii) reinforcing with metal, carbon, or ceramic materials. In this review, we also summarize the overall recent progress in low melting temperature solders and present a critical overview of the basis of microscopic analysis with regard to grain size and solid solutions, electrical conductivity by supplementation with conductive additives, thermal behavior (melting point and melting range) according to surface oxidation and intermetallic compound formation, and various mechanical properties

Pulse Electrodeposition of Lead-Free Tin-Based Composites for Microelectronic Packaging

This chapter provides a detailed overview of the various Sn-based composites solders reinforced with ceramic nanoparticles. These solders are lead free in nature and are produced by various process like powder metallurgy, ball milling, casting as well as simple and economic pulse co-electrodeposition technique. In this chapter, various electrodeposited composite solders, their synthesis, characterization, and evaluation of various properties for microelectronic packaging applications, such as microstructure, microhardness, density and porosity, wear and friction, electrochemical corrosion, melting point, electrical resistivity, and residual stress of the monolithic Sn-based and (nano)composite solders have been presented and discussed. This chapter is divided into the following sections: such as introduction to microelectronic packaging, synthesis routes for solders and composites, various nanoreinforcement, and the mechanism of incorporation in solder matrix, the pulse co-electrodeposition technique, the various factors affecting composite deposition, and the improved properties of composite solders over monolithic solders for microelectronic packaging applications are also summarized here

Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications

As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au-Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au-Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Two distinct phases, Au5Sn and AuSn, were deposited at a composition of 30at.%Sn. The Au-Sn flip-chip joints were formed at 300 and 400 degrees without using any flux. In the case where the samples were reflowed at 300 degrees, only an (Au,Ni)3Sn2 IMC layer formed at the interface between the Au-Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)3Sn2 and (Au,Ni)3Sn, were found at the interfaces of the samples reflowed at 400 degrees. As the reflow time increased, the thickness of the (Au,Ni)3Sn2 and (Au,Ni)3Sn IMC layers formed at the interface increased and the eutectic lamellae in the bulk solder coarsened.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Thermomechanical behavior of monolithic Sn-Ag-Cu solder and copper fiber reinforced solders

Solder joints provide both electrical and mechanical interconnections between a silicon chip and the packaging substrate in an electronic application. The thermomechanical cycling in the solder causes numerous reliability challenges, mostly because of the mismatch of the coefficient of thermal expansion between the silicon chip and the substrate. The actual transition to lead-free solders and the trend towards hotter-running, miniaturized and higher current density chips aggravate this situation. Therefore, improved solder joints, with higher resistance to creep and low cycle fatigue, are necessary for future generations of microelectronics. This study focuses on a thermomechanical behavior comparison between monolithic Sn-Ag-Cu, copper fiber and copper ribbon cylindrical reinforced solders. The composite solders were found to reduce the inelastic strain range of the joint relative to monolithic solder, but at the expense of increased stress range.http://archive.org/details/thermomechanical109452062Approved for public release; distribution is unlimited

Effect of Ag nanopowders on microstructure, hardness and elastic modulus of Sn-Bi solders

This paper presents the microstructure, hardness and elastic modulus of Sn58Bi, Sn57Bi1Ag and Ag nanopowders reinforced Sn58Bi composite solders. Microstructural observations reveal that the Ag nanopowders reinforced Sn58Bi composite solders have smaller grains of Ag3Sn and a more uniform Ag3Sn distribution in comparison with those of Sn57Bi1Ag solder. Nanoindentation test results show that the addition of Ag nanopowders has greatly enhanced the mechanical properties of Sn58Bi solder, i.e., it exhibits 13-30% increase in hardness and 10-22% increase in modulus of the composite solder. Besides, hardness and elastic modulus of solder are dependent on the size, distribution and the quantity of the second-phase

The durability of solder joints under thermo-mechanical loading; application to Sn-37Pb and Sn-3.8Ag-0.7Cu lead-free replacement alloy

Solder joints in electronic packages provide mechanical, electrical and thermal connections. Hence, their reliability is also a major concern to the electronic packaging industry. Ball Grid Arrays (BGAs) are a very common type of surface mount technology for electronic packaging. This work primarily addresses the thermo-mechanical durability of BGAs and is applied to the exemplar alloys; traditional leaded solder and a popular lead-free solder. Isothermal mechanical fatigue tests were carried out on 4-ball test specimens of the lead-free (Sn-3.8Ag-0.7Cu) and leaded (Sn-37Pb) solder under load control at room temperature, 35°C and 75°C. As well as this, a set of combined thermal and mechanical cycling tests were carried out, again under load control with the thermal cycles either at a different frequency from the mechanical cycles (not-in-phase) or at the same frequency (both in phase and out-of-phase). The microstructural evaluation of both alloys was investigated by carrying out a series of simulated ageing tests, coupled with detailed metallurgical analysis and hardness testing. The results were treated to produce stress-life, cyclic behaviour and creep curves for each of the test conditions. Careful calibration allowed the effects of substrate and grips to be accounted for and so a set of strain-life curves to be produced. These results were compared with other results from the literature taking into account the observations on microstructure made in the ageing tests. It is generally concluded that the TMF performance is better for the Sn-Ag-Cu alloy than for the Sn-Pb alloy, when expressed as stress-life curves. There is also a significant effect on temperature and phase for each of the alloys, the Sn-Ag-Cu being less susceptible to these effects. When expressed as strain life, the effects of temperature, phase and alloy type are much diminished. Many of these conclusions coincided with only parts of the literature and reasons for the remaining differences are advanced

A review: microstructure and properties of tin-silver-copper lead-free solder series for the applications of electronics

Purpose The research on lead-free solder alloys has increased in past decades due to awareness of the environmental impact of lead contents in soldering alloys. This has led to the introduction and development of different grades of lead-free solder alloys in the global market. Tin-silver-copper is a lead-free alloy which has been acknowledged by different consortia as a good alternative to conventional tin-lead alloy. The purpose of this paper is to provide comprehensive knowledge about the tin-silver-copper series. Design/methodology/approach The approach of this study reviews the microstructure and some other properties of tin-silver-copper series after the addition of indium, titanium, iron, zinc, zirconium, bismuth, nickel, antimony, gallium, aluminium, cerium, lanthanum, yttrium, erbium, praseodymium, neodymium, ytterbium, nanoparticles of nickel, cobalt, silicon carbide, aluminium oxide, zinc oxide, titanium dioxide, cerium oxide, zirconium oxide and titanium diboride, as well as carbon nanotubes, nickel-coated carbon nanotubes, single-walled carbon nanotubes and graphene-nano-sheets. Findings The current paper presents a comprehensive review of the tin-silver-copper solder series with possible solutions for improving their microstructure, melting point, mechanical properties and wettability through the addition of different elements/nanoparticles and other materials. Originality/value This paper summarises the useful findings of the tin-silver-copper series comprehensively. This information will assist in future work for the design and development of novel lead-free solder alloys

Effect of heat treatment temperature on SN-0.7CU solders material on microstructure

Soldering plays the most important role for joining technology in electronic industry.The conventional tin-lead solders have been used for a quite long time in electronic industries.However,since lead is a toxic element and harmful to individual health and environment,many researchers have proposed lead-free solder to protect individual health and environment as well.The objective of this study is to analyze the microstructure at the solder and base metal interface.This study investigates the interfacial reactions between Sn-0.7Cu solder material and copper substrate before and after aging at 100°C, 150°C and 200°C for 1 hour,3 hours and hours.Copper substrates are connected to each other by manual soldering.After soldering, the intermetallic compound formed at the interface is Cu6Sn5 intermetallic compound.The thickness of the intermetallic compound increases as the aging time and temperature increased. Intermetallic compound layer must be keep at sufficient thickness because excessive amount of intermetallic compound can generate defect and affect the solder joint reliability

A study on the profile of solid waste and its reduction alternatives at Universiti Tun Hussein Onn Malaysia (UTHM), Pagoh Campus, Muar, Johor

Universiti Tun Hussein Onn Malaysia (UTHM) Pagoh campus is a new branch of UTHM campus situated at the Pagoh Education Hub, Johor. No studies have been conducted to determine the amount and types of waste generated in this campus, as well as the waste reduction initiatives. It is important to find out the generation and composition of waste before any recommendations for an integrated solid waste management program can be made. A mixed-method approach which comprised of quantitative and qualitative data collection was used to achieve the objectives of this research. This research revealed the results of a waste audit conducted for 10 consecutive weeks on the campus which includes the academic zone, cafeteria zone and laboratory zone. From the quantitative results, it can be summarized the average solid waste generation rate in UTHM Pagoh campus varied during regular lecture weeks, mid-semester break, and Ramadan lecture weeks, which were 203.90 kg/day, 93.96 kg/day, and 24.48 kg/day respectively. The cafeteria has been identified as the main contributor to solid waste generation on campus. The composition of the waste generated consisted of 66.9 % food waste, 19.0 % residual waste, 7.1% plastic, 4.3 % paper, 0.7 % metals, 0.7 % beverage cartons, 0.5 % aluminum, 0.6 % of other organic waste, 0.2 % of other non-organic waste and 0.1 % glass. From the qualitative data collection, the interview results revealed that the main obstacle in implementing a good SWM in the campus was the students’ and staffs’ attitude towards solid waste issues. Other challenges elaborated by the respondents include low awareness, insufficient facilities, and financial constraints. From the waste collected, it was found that a potential income of RM 330.98 could be obtained from the sales of recyclable waste. In addition, results from the cost-benefit analysis revealed that the implementation of a composting machine was found feasible to be implemented in the campus. Based on the results, proposals on the awareness campaigns, waste separation models and policy to improve the quality of SWM on the campus are provided to reduce the solid waste generated strategically