Emerald | Soldering & Surface Mount Technology | Table of Contents http://www.emeraldinsight.com/0954-0911.htm Table of contents from the most recently published issue of Soldering & Surface Mount Technology Journal en-gb Tue, 27 May 2014 00:00:00 +0100 2014 Emerald Group Publishing Limited editorial@emeraldinsight.com support@emeraldinsight.com 60 Emerald | Soldering & Surface Mount Technology | Table of Contents http://www.emeraldinsight.com/common_assets/img/covers_journal/ssmtcover.gif http://www.emeraldinsight.com/0954-0911.htm 120 157 Influence of PTH offset angle in wave soldering with thermal-coupling method http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114158&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-08-2013-0021 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The aim of this study is to investigate the effects of offset angle in wave soldering by using thermal fluid structure interaction modeling with experimental validation. <B>Design/methodology/approach</B> – The authors used a thermal coupling approach that adopted mesh-based parallel code coupling interface between finite volume-and finite element-based software (ABAQUS). A 3D single pin-through-hole (PTH) connector with five offset angles (0 to 20°) on a printed circuit board (PCB) was built and meshed by using computational fluid dynamics preprocessing software called GAMBIT. An implicit volume of fluid technique with a second-order upwind scheme was also applied to track the flow front of solder material (Sn63Pb37) when passing through the solder pot during wave soldering. The structural solver and ABAQUS analyzed the temperature distribution, displacement and von Mises stress of the PTH connector. The predicted results were validated by the experimental solder profile. <B>Findings</B> – The simulation revealed that the PTH offset angle had a significant effect on the filling of molten solder through the PCB. The 0° angle yielded the best filling profile, filling time, lowest displacement and thermal stress. The simulation result was similar to the experimental result. <B>Practical implications</B> – This study provides a better understanding of the process control in wave soldering for PCB assembly. <B>Originality/value</B> – This study provides fundamental guidelines and references for the thermal coupling method to address reliability issues during wave soldering. It also enhances understanding of capillary flow and PTH joint issues to achieve high reliability in PCB assembly industries. Article literatinetwork@emeraldinsight.com (Mohd Sharizal Abdul Aziz, Mohd Zulkifly Abdullah, Chu Yee Khor) Tue, 27 May 2014 00:00:00 +0100 A method for the tin pest presence testing in SnCu solder alloys http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114159&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-10-2013-0027 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this study is to develop a testing method for tin pest in tin – copper (SnCu) alloys. Tin pest is the allotropic transformation of white ß-tin (body-centered tetragonal structure) into gray a-tin (diamond cubic structure) at temperatures &lt; 13.2°C. <B>Design/methodology/approach</B> – Bulk samples of Sn99Cu1 weight per cent (purity, 99.9 weight per cent) were cast in the form of roller-shaped ingots with a diameter of 1.0 cm and a height of 0.7 cm. The samples were then divided into four groups. The first group included samples artificially inoculated with a-tin powder. The second group was inoculated in the same way as the samples from the first group but additionally subjected to mechanical pressing. The third group of ingots was only subjected to mechanical pressing. The fourth group of samples consisted of as-received roller-shaped ingots.All samples were divided into two groups and kept either at -18°C or at -30°C for the low-temperature storage test. For tin pest identification, a visual inspection was made, using a Hirox digital microscope over 156 days at intervals not longer than 14 days. The plot of the transformation rate, presented as the average increase in the area of a-tin warts in time, was also determined. To demonstrate the differences between regions of ß- and a-tin, scanning ion microscopy observations using the focused ion beam technique was performed. <B>Findings</B> – The first symptoms of tin pest were observed for the inoculated, mechanically pressed samples stored at -18°C, as well as those at -30°C, after less than 14 days. In the first stage of transformation, the rate was higher at -30°C for some time but, after about 75 days of storage at sub-zero temperatures, the rate at -30°C became lower compared to the rate at -18°C. Inoculation via the application of substances which are structurally similar to a-tin was efficient for the proposed new approach of rapid testing only when applied with simultaneous mechanical pressing. Infection from pressed-in seeds, leading to conventional seeded growth, was more rapid than infection in contact with seeds (without mechanical pressing), where the transition mechanism was induced by the epitaxial growth of metastable ice. <B>Originality/value</B> – The new rapid method for the diagnostic testing of the susceptibility of different SnCu alloys to tin pest in a period much shorter than 14 days (within single days for storage at -30°C) is proposed and described. The test procedure described in this paper produced results several times quicker than conventional procedures, which may take years. In effect, the behavior of tin alloys in the face of tin pest may be predicted much more easily and much earlier. The same procedure can be applied to other SnCu alloys used in electronics (and in other areas), if the test samples are prepared in a similar manner. Article literatinetwork@emeraldinsight.com (Agata Skwarek, Jan Kulawik, Andrzej Czerwinski, Mariusz Pluska, Krzysztof Witek) Tue, 27 May 2014 00:00:00 +0100 Lifetime prediction and design aspects of reliable lead-free non-collapsible BGA joints in LTCC packages for RF/microwave telecommunication applications http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114160&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-07-2013-0018 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this paper is to describe the behavior of different lead-free solders (95.5Sn3.8Ag0.7Cu, i.e. SAC387 and Sn7In4.1Ag0.5Cu, i.e. SAC-In) in thermomechanically loaded non-collapsible ball grid array (BGA) joints of a low-temperature co-fired ceramic (LTCC) module. The validity of a modified Engelmaier’s model was tested to verify its capability to predict the characteristic lifetime of an LTCC module assembly implementable in field applications. <B>Design/methodology/approach</B> – Five printed wiring board (PWB) assemblies, each carrying eight LTCC modules, were fabricated and exposed to a temperature cycling test over a -40 to 125°C temperature range to determine the characteristic lifetimes of interconnections in the LTCC module/PWB assemblies. The failure mechanisms of the test assemblies were verified using scanning acoustic microscopy, scanning electron microscopy (SEM) and field emission SEM investigation. A stress-dependent Engelmaier’s model, adjusted for plastic-core solder ball (PCSB) BGA structures, was used to predict the characteristic lifetimes of the assemblies. <B>Findings</B> – Depending on the joint configuration, characteristic lifetimes of up to 1,920 cycles were achieved in the thermal cycling testing. The results showed that intergranular (creep) failures occurred primarily only in the joints containing Sn7In4.1Ag0.5Cu solder. Other primary failure mechanisms (mixed transgranular/intergranular, separation of the intermetallic compound/solder interface and cracking in the interface between the ceramic and metallization) were observed in the other joint configurations. The modified Engelmaier’s model was found to predict the lifetime of interconnections with good accuracy. The results confirmed the superiority of SAC-In solder over SAC in terms of reliability, and also proved that an air cavity structure of the module, which enhances its radio frequency (RF) performance, did not degrade the reliability of the second-level interconnections of the test assemblies. <B>Originality/value</B> – This paper shows the superiority of SAC-In solder over SAC387 solder in terms of reliability and verifies the applicability of the modified Engelmaier’s model as an accurate lifetime prediction method for PCSB BGA structures for the presented LTCC packages for RF/microwave telecommunication applications. Article literatinetwork@emeraldinsight.com (Jussi Putaala, Olli Salmela, Olli Nousiainen, Tero Kangasvieri, Jouko Vähäkangas, Antti Uusimäki, Jyrki Lappalainen) Tue, 27 May 2014 00:00:00 +0100 Solder joint imagery compressing and recovery based on compressive sensing http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114161&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-09-2013-0024 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this paper is to develop an improved compressive sensing algorithm for solder joint imagery compressing and recovery. The improved algorithm can improve the performance in terms of peak signal to noise ratio (PSNR) of solder joint imagery recovery. <B>Design/methodology/approach</B> – Unlike the traditional method, at first, the image was transformed into a sparse signal by discrete cosine transform; then the solder joint image was divided into blocks, and each image block was transformed into a one-dimensional data vector. At last, a block compressive sampling matching pursuit was proposed, and the proposed algorithm with different block sizes was used in recovering the solder joint imagery. <B>Findings</B> – The experiments showed that the proposed algorithm could achieve the best results on PSNR when compared to other methods such as the orthogonal matching pursuit algorithm, greedy basis pursuit algorithm, subspace pursuit algorithm and compressive sampling matching pursuit algorithm. When the block size was 16 × 16, the proposed algorithm could obtain better results than when the block size was 8 × 8 and 4 × 4. <B>Practical implications</B> – The paper provides a methodology for solder joint imagery compressing and recovery, and the proposed algorithm can also be used in other image compressing and recovery applications. <B>Originality/value</B> – According to the compressed sensing (CS) theory, a sparse or compressible signal can be represented by a fewer number of bases than those required by the Nyquist theorem. The findings provide fundamental guidelines to improve performance in image compressing and recovery based on compressive sensing. Article literatinetwork@emeraldinsight.com (Huihuang Zhao, Yaonan Wang, Zhijun Qiao, Bin Fu) Tue, 27 May 2014 00:00:00 +0100 Tin oxide coverage on tin whisker surfaces, measurements and implications for electronic circuits http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114162&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-12-2013-0040 <strong>Abstract</strong><br /><br /><B>Purpose</B> – This paper aims to evaluate the morphology and thickness of oxides that form on the surfaces of tin whiskers. The problems related to the growth of tin whiskers are stated, and the relevance of oxide layers adhering to whiskers is discussed. <B>Design/methodology/approach</B> – Modern laboratory methods including focused ion beam sectioning, energy dispersive spectroscopy and X-ray photoelectron spectroscopy have been used to characterise the composition of oxides present on the surfaces of 48-year-old whiskers. These very old whiskers had nucleated and grown on electronic equipment stored at ambient temperatures. They were compared to the oxide layers on newly grown 2-week-old whiskers. <B>Findings</B> – A dual oxide film, consisting of stannous and stannic oxides, was found present on both the old and the new whiskers. Measurements of oxide thickness were established for both generations of whiskers and these were noted to be similar to those films present on pure, cleaned bulk tin. <B>Research limitations/implications</B> – Only very new and very old whiskers, and their oxide films, were the focus of this investigation. However, sufficient data were gained to predict the effect both kinds of oxide films would have during whisker bridging between conductors and the risk of short circuits. Thick oxide films (order of 30 nm) may have a greater resistance to shorting, but they will be more difficult to remove during solder dipping (with respect to whisker mitigation). <B>Practical implications</B> – A knowledge of the oxide thickness on growing/gyrating tin whiskers will provide the electronics industry with data useful for establishing the risk of short circuits. It will also be useful during the forensic work associated with component and assembly failure analysis. <B>Originality/value</B> – The data resulting from this study are unique. They are of value to others who may require knowledge of the morphology, composition and thickness of oxides present on tin whiskers of different vintage. Article literatinetwork@emeraldinsight.com (Barrie D. Dunn, Grazyna Mozdzen) Tue, 27 May 2014 00:00:00 +0100 Review on the effect of alloying element and nanoparticle additions on the properties of Sn-Ag-Cu solder alloys http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114163&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-02-2014-0001 <strong>Abstract</strong><br /><br /><B>Purpose</B> – 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. <B>Design/methodology/approach</B> – 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 &lt; 425°C (Yoon <IT>et al.</IT>, 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 <IT>et al.</IT>, 2006; Tsao <IT>et al.</IT>, 2010; Wang <IT>et al.</IT>, 2002; Gain <IT>et al.</IT>, 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. <B>Findings</B> – 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. <B>Originality/value</B> – 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. Article literatinetwork@emeraldinsight.com (Ervina Efzan Mhd Noor, Amares Singh) Tue, 27 May 2014 00:00:00 +0100 Thermal warpage analysis of PBGA mounted on PCB during reflow process by FEM and experimental measurement http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=17114164&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-11-2013-0034 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this paper is to study the thermal warpage of a plastic ball grid array (PBGA) mounted on a printed circuit board (PCB) during the reflow process. <B>Design/methodology/approach</B> – A thermal-mechanical coupling method that used finite-element method software (ANSYS 13.1) was performed. Meanwhile, a shadow moiré apparatus (TherMoiré PS200) combined with a heating platform was used for the experimental measurement of the warpage of PBGA according to the JEDEC Standard. <B>Findings</B> – The authors found that the temperature profiles taken from the simulated results and experimental measurement are consistent with each other, only with a little and acceptable difference in the maximum temperatures. Furthermore, the maximum warpage measurements during the reflow process are 0.157 mm and 0.149 mm for simulation and experimental measurements, respectively, with a small 5.37 per cent difference. The experimental measurement and simulated results are well correlated. Based on the validated finite element model, two factors, namely, the thickness and dimension of PCB, are explored about their effect on the thermal warpage of PBGA mounted on PCB during the reflow process. <B>Practical implications</B> – The paper provides a thorough parametrical study of the thermal warpage of PBGA mounted on PCB during the reflow process. <B>Originality/value</B> – The findings in this paper illustrate methods of warpage study by combination of thermal-mechanical finite element simulation and experimental measurement, which can provide good guidelines of the PCB design in the perspective of thermal warpage during the reflow process. Article literatinetwork@emeraldinsight.com (Weisheng Xia, Ming Xiao, Yihao Chen, Fengshun Wu, Zhe Liu, Hongzhi Fu) Tue, 27 May 2014 00:00:00 +0100 Erratum http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=3&articleid=1937994&show=abstract Erratum Tue, 27 May 2014 00:00:00 +0100