Bi-Ag as an alternative high temperature solder

The search for a high temperature lead-free solder replacement for high temperature leaded solder eutectic alloy has been an evolving process as the threat of a regional lead ban became a reality in July 2006. The advantages and disadvantages of lead-free solder in terms of manufacturing, performance and reliability have been increasingly revealed through companies' Research and Development (R&D), industrial consortia and university researchers. Materials and component design are the primary criteria to focus on the development for the current generation of high temperature lead-free solder alloys. According to the current status of high temperature lead free soldering, there are many unsolved technical problems such as explanation on the lift-off phenomenon, establishment of high temperature lead-free plating technology, construction of a database of physical properties (solder, parts, PCBs), standardization of high temperature solder materials evaluation technology, and most importantly, the best candidate material for high temperature solder. Clearly, high temperature soldering is one of the unsolved problems of the century in lead-free soldering. Moreover, most of the questions still remain unanswered by researchers. This paper reviews research conducted on the Bi-Ag solder alloy, which is one of the candidate alloys that has been proposed as an alternative for high temperature lead-free solder

The effects of welding parameters on butt joints using robotic gas metal arc welding

Robotic gas metal arc welding (GMAW) is one of the most popular welding methods in the manufacturing industries. The main focus of this paper is how welding parameters affect the joining process. The butt joint will be used in this study to identify suitable welding parameters for welding voltage, welding current and welding speed. The experiment involves using a specimen of low carbon steel A1008 as base metal and AWS ER 70S-6 as the filler metal in the butt joint process. The joint was tested to determine the tensile strength, which is identified as the main characteristic of the weld, and the hardness of the weld is also recorded. The results show that a welding voltage of 24 volts, current of 200-220 ampere, and speed of 45-50 cm/min gave the highest tensile hardness of 239.05 MPa (180HV)

Microstructural evaluation of Bi-Ag and Bi-Sb lead-free high-temperature solder candidates on copper substrate with multiple reflow number

An impetus has been provided towards the development of lead-free solders by worldwide environmental legislation that banned the use of lead in solders due to the lead toxicity. This study focus on Bi-Ag and Bi-Sb solder alloys, in compositions from 1.5 to 5 wt % Ag and Sb. The effects of Ag and Sb amount, and reflow number on the microstructure and morphology of solder bulk were analysed by optical microscope and scanning electron microscope-energy dispersive X-ray. Based on the results, the grain boundary grooving was observed in all samples except Bi-5Sb in all three reflows. Metallurgical and chemical reaction between interface and solders were found in Bi-5Sb solder alloys in different reflow numbers which lead to appearance of Cu3Sb intermetallic compound layer at the interface. Reflow numbers had a significant effect on the size of Cu-rich phase. Also it was observed that, with increasing reflow number Bi-Cu phase found in Bi-2.5Sb solder dissolves into the solder bulk

Nanocrystallization of CK60 commercial steel by drilling method

Drilling as a novel Surface Sever Plastic Deformation method (SSPD) has been applied to commercial CK60 steel plate to create a Nano Crystalline (NC) structured layer. In present study, the CK60 steel plate has been quenched in room temperature water from 950 °C (1 Hr) and tempered in 350°C for one hour. Drilling has been done with use of Ti-Carbide coated drilling bit under 10, 15 and 20 m/min speeds. The microstructure of the samples was studied by light microscope and high resolution SEM. The formation of NC layer having grain size in the order of 50nm was confirmed by the SEM observation and applying Hall-Pitch formula on the samples drilled with 15 m/min speed. The created fine grain zone is separated from base metal structure and clear boundary with 1 to 10 microns thickness where the drilling speed changes from 15 to 20 m/min. The microhardness test result illustrates that the hardness of surface NC layer increases almost more than twice when compared with coarse grain structure of base metal

Interfacial reaction of Bi–Ag and Bi–Sb solders on copper substrate with multiple reflow number

Owing to the toxicity of lead, much effort has been put in studies on lead-free solders after environmental legislations prohibited the use of lead in these parts worldwide. Here, Bi–Ag and Bi–Sb alternative solder alloys containing 1·5–5 wt-% Ag and Sb were investigated. The effect of the reflow number and weight percentage of Ag and Sb on the surface properties of solders and interfacial reactions between the solder bulk and the Cu substrate were analysed by optical microscopy and scanning electron microscopy–energy dispersive X-ray. The results show that by increasing the reflow number and wt-% of Ag and Sb in the solder bulk, the thickness of the mechanical grain boundary grooving is increased. However, the thickness of the Cu3Sb intermetallic compound layer at the interface of Bi–5Sb decreased by increasing the reflow number. Moreover, our findings show that the amount of Ag and Sb in solder alloys and the reflow number have different behaviours on the wettability properties. By increasing the reflow number, the wetting angle decreased in Bi–Ag solder alloys, whereas it increased in Bi–Sb solder alloys

The effect of nickel doping on SAC305 lead-free solders and EN(B)EPIG surface finish

Recently, there are many portable electronics product such as i-pad, smart phone and tablet were widely used due to growing needs of busy lives and demanding, more functionalities and compatibility. The growing of these smart technologies made electronic packaging are moving parallel with current technology and expanding rapidly because of global competitive pressure. Thus, flip chip technology is one of the important element need to be considered in order to produce high performance and quality of electronic devices due to shorter electrical connections between the chip and substrate and very high input/output capacity and the smallest possible package size. In flip chip applications, solder bump was used to connect the die to the substrate or circuit board. The addition of doping element in lead-free solder has been discussed have a big influence on the solder joint quality including solder microstructure. It also can enhanced the properties and improve the performance of interfacial reaction at interface and made a reliability of lead-free solder especially on Sn-3.0Ag-0.5Cu was increased. Therefore, this study investigates the effect of nickel doping on Sn-3.0Ag-0.5Cu (SAC305) lead-free solders and electroless nickel (boron)/electroless palladium/immersion gold (EN(B)EPIG) surface finish. In this study, two types of lead-free solders was used which are Sn-3.0Ag-0.5Cu (SAC305) and Sn-3.0Ag-0.5Cu-0.05Ni (SACN30505) with solder size diameter of 500 μm in order to examine the effect of nickel on interfacial reaction during soldering process. Reliability of solder joint has been assessed by performing solid state isothermal aging at 125C for 250, 500, 1000 and 2000 hours. Several characterization techniques will be conducted including image analyzer, optical microscope, field emission scanning electron microscopy and energy dispersive x-ray analysis to characterize the intermetallic formed. After reflow soldering process, it was found that the (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4 intermetallic compound (IMC) is formed at interface. (Ni, Cu)3Sn4 dominates in the outside of solder joint while (Cu, Ni)6Sn5 dominates in the centre of joints. Besides that, after soldering and isothermal aging process, SAC305 solder with additions of 0.05% of Ni (SACN30505) made the intermetallics grew slightly faster than in the solder without Ni additions. Hence, analysis by optical microscope revealed that the IMC thickness of the SACN30505 solder produced thicker IMC compared to SAC305 for both situations. This observation is confirmed by the increase in grain size of intermetallics with Ni additions. Moreover, aging time resulted in an increase in thickness and changed the morphology into more spherical, dense and large grain size. In addition, the results also revealed that the thickness of intermetallics formed is proportional to the aging duration

Application of artificial neural networks for the optimisation of wetting contact angle for lead free Bi-Ag soldering alloys

In the recent years, electronic packaging provides significant research and development challenges across multiple disciplines such as performance, materials, reliability, thermals and interconnections. New technologies and techniques frequently adopted can be implemented in soldering alloys of semiconductor sectors in terms of optimisation. Wetting contact angle or wettability of solder alloys is one of the important factors which has got the attention of scholars. Hence in this study, due to the remarkable similarity over classical solder alloys (Pb-Sn), Bi-Ag solder was investigated. Data were collected through the effects of aging time variation and different weight percentages of Ag in solder alloys. The contact angle of the alloys with Cu plate was measured by optical microscopy. Artificial neural networks (ANNs) were applied on the measured datasets to develop a numerical model for further simulation. Results of the experiments and simulations showed that the coefficient of determination (R2) is around 0.97, which signifies that the ANN set up is appropriate for the evaluation

Techniques on dispersion of nanoparticles in polymer matrices: a review

Dispersibility of nanoparticles is the key problem in nanotechnology industries, and thus warrants attention on the techniques of dispersion. This review paper presents dispersibility of treated nanoparticles in polymer resin. Dispersibility of nanoparticles in polymer media is crucial in order to enhance the mechanical and thermal properties of nanocomposite. This paper concentrates on several preparations on how to incorporate nanoparticles in polymer to overcome the problem described in this review. A few techniques are discussed in this paper such as by using ultra sonication or even directly mixing nanoparticles into polymer matrix

Investigation of Alkaline Surface Treatment Effected on Flax Fibre Woven Fabric with Biodegradable Polymer Based on Mechanical Properties

Biodegradable polymers such as polylactic acid (PLA) are used nowadays due to their degradability, durability and environmentally friendly properties. Alkaline surface treatment of natural fibres is used to increase the flexural properties of composites. This research investigated the flexural properties of dry compressed PLA, wet mix PLA, untreated flax/PLA and treated flax/PLA composites. The flax fibre was first treated with NaOH. The wet mix PLA was prepared via solvent casting with chloroform and dried at room temperature overnight followed by post-drying in an oven. The flax/PLA composites were fabricated using a hot press for 6 minutes. The wet mix PLA showed higher flexural strength compared to the dry compressed PLA. The treated flax fibre composite showed higher flexural strength compared to the untreated flax fibre. The flexural strength and elongation at break of the treated flax fibre composite was increased by 4.79% and 27.76%, respectively, while the flexural modulus decreased by 0.79% compared with the untreated flax composite. The treated flax composite also showed an improvement in impact properties, increasing its impact strength by about 3% and 10% at energy levels of 10 J, 15 J, and 17.5 J compared with the untreated flax fibre. Therefore, the investigation of the surface treatment of flax in a PLA matrix based on its mechanical properties revealed better properties compared to untreated flax/PLA composite

Cracks, microcracks, and fracture toughness of polymer composites: formation, testing method, nondestructive detection, and modifications

Polymer matrix composite consists of polymeric matrix and fiber as reinforcement. The properties of the matrices and fibers are usually opposite to each other. Where the matrix is soft, the fibers are rigid. This is how they complement each other since the main purpose of the rigid fiber addition was to increase the strength of the soft polymer matrix. However, because of these differences, the microcrack and crack formation and propagation in polymer composite become a complicated topic to be studied since it involves the interaction between the different type of materials. Example of factors that influence the formation of cracks as discussed in the chapter were type and dimensions of the fiber material used, compatibility between the matrix and fiber material, manufacturing process methodology, and application environment. After the cracks or microcracks formed, the next step is the propagation of the cracks. This progress was also influenced by these parameters and the type of composite configuration. The objective of this chapter is to review the different effects of the factors that influence the formation and propagation of cracks and microcracks in polymer composite. Following the discussion about the formation of microcracks, a step-by step method on how to detect and measure the cracks and microcracks, fracture mechanics, and the nondestructive testing available related to it is discussed in detail. Finally, based on knowledge of composite materials, two methods that have been studied and show promising results to improve fracture toughness in polymer composite material