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, 01 Apr 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 Temperature cycling with Peltier elements of boards with SMD components and failure evaluation http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=2&articleid=17107911&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-02-2013-0004 <strong>Abstract</strong><br /><br /><B>Purpose</B> – This article aims to discuss the construction of a system for temperature cycling, where Peltier elements are used as heating or cooling elements. This article describes the results and experiences based on several years of practice in the area of thermo-mechanical reliability of soldered joints on printed boards with SMD components. <B>Design/methodology/approach</B> – The authors discuss the characteristics of the design, the threshold temperatures, dynamic properties of the system and, most importantly, the reliability and the useful life of the Peltier elements. The advantages and disadvantages of the system are mentioned as well as examples of use. <B>Findings</B> – The utilisation of Peltier elements for temperature cycling is possible, but it is important to keep in mind that the reliability of the elements is similar to the reliability of the system, and therefore, it is essential to replace the defective Peltier elements during the cycling. <B>Research limitations/implications</B> – The construction of system is very simply. It is necessary to ensure the Peltier elements with low dispersion parameters. <B>Originality/value</B> – The system is very well suited for cycling of printed boards, especially one sided, multi-chip systems, COB systems, flip-chip embedded construction, etc. The system can be used in situations where it is possible to ensure an effective heat transfer and where extremely low temperatures are not required. Article literatinetwork@emeraldinsight.com (Josef Šandera, Michal Nicák) Tue, 01 Apr 2014 00:00:00 +0100 Reliability analysis of an ACA attached flex-on-board assembly for industrial application http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=2&articleid=17107912&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-03-2013-0007 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this paper is to examine the long-term reliability of an anisotropic conductive adhesive (ACA) attached polyethylene terephthalate (PET) flex-on-board (FOB) assembly for industrial application used in harsh environments. In addition, the possibility of reducing reliability testing time was studied. <B>Design/methodology/approach</B> – A-40/+125°C thermal cycling test with 5- and 14-minute soak times was used to study the reliability. To study the functionality of the FOB assembly during testing, a real-time resistance measurement was used together with a 90° peel strength test. Failure analysis was performed on samples using scanning electron microscopy and cross sectioning. <B>Findings</B> – No failures or noticeable increase in the measured resistance values were seen during testing. The peel strength, however, decreased significantly with both soak times used. The highest drop in the mechanical strength occurred at the start of the temperature cycling tests. The time spent at the high temperature extreme seemed to have a greater impact on the peel strength than the number of temperature cycles. The failure mode of peel tested samples changed due to temperature cycling from interfacial delamination to cohesive failure. The temperature cycling was also observed to induce voiding inside the adhesive. <B>Originality/value</B> – The paper illustrates the applicability of ACA attached PET flex in high reliability industrial applications. Additionally, testing methods for high reliability adhesive interconnections are discussed. Especially, the effect of temperature cycling soak time on peel test results and reliability testing time is studied. Article literatinetwork@emeraldinsight.com (Janne Kiilunen, Laura Frisk) Tue, 01 Apr 2014 00:00:00 +0100 Statistical analysis of stencil technology for wafer-level bumping http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=2&articleid=17107913&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-07-2013-0017 <strong>Abstract</strong><br /><br /><B>Purpose</B> – Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150?<IT>µ</IT>m pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues. <B>Design/methodology/approach</B> – In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150?<IT>µ</IT>m pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types. <B>Findings</B> – Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent, were achieved with the micro-engineered stencil using low aperture area ratios of 0.5. <B>Originality/value</B> – Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200?<IT>µ</IT>m and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing. Article literatinetwork@emeraldinsight.com (Robert W. Kay, Gerard Cummins, Thomas Krebs, Richard Lathrop, Eitan Abraham, Marc Desmulliez) Tue, 01 Apr 2014 00:00:00 +0100 Corrosion of Sn-3.0Ag-0.5Cu thin films on Cu substrates in alkaline solution http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=2&articleid=17107914&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-01-2013-0001 <strong>Abstract</strong><br /><br /><B>Purpose</B> – The purpose of this paper is to examine the corrosion behaviors of SAC305 thin film solder alloy in 6?M KOH solution. <B>Design/methodology/approach</B> – The corrosion behavior of bare Cu, as-deposited SAC305/Cu and as-reflowed SAC305/Cu thin films at varying temperatures, was investigated by means of potentiodynamic polarization in a 6?M KOH solution. The microstructure, phase and thickness of the intermetallic compounds formed were determined before and after polarization. <B>Findings</B> – Bare Cu was found to possess the best corrosion resistance, whereas the as-deposited SAC305/Cu had the lowest corrosion resistance. As-reflowed SAC305/Cu with an exposed Cu<DN>3</DN>Sn layer exhibited better corrosion resistance than did Cu<DN>6</DN>Sn<DN>5</DN>. The Ag<DN>3</DN>Sn phase has the noblest characteristic because it was retained and did not dissolve in the KOH solution. All of the samples contained the corrosion products of oxide. Bare Cu obeys the well-known duplex structure of a Cu<DN>2</DN>O/CuO, Cu(OH)<DN>2</DN> layer. For as-reflowed SAC305/Cu, the corroded surface was also mainly composed of SnO and SnO<DN>2</DN>. <B>Originality/value</B> – New analysis on the polarization of thin film characteristics of SAC305 lead-free solder in alkaline solution. Article literatinetwork@emeraldinsight.com (Liu Mei Lee, Muhammad Firdaus Mohd Nazeri, Habsah Haliman, Ahmad Azmin Mohamad) Tue, 01 Apr 2014 00:00:00 +0100 Zn diffusion and reflow behaviour of Sn-9Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga solders on a Ni/Cu substrate under IR reflow http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=26&issue=2&articleid=17107915&show=abstract http://www.emeraldinsight.com/10.1108/SSMT-07-2013-0020 <strong>Abstract</strong><br /><br /><B>Purpose</B> – This paper aims to compare the reflow and Zn diffusion behaviors in Sn-Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (5E) solders during soldering on a Ni/Cu substrate under infrared (IR) reflow. The study proposes a model on the effect of various elements particularly Zn diffusion behavior in the solders on the formation of intermetallic compounds (IMCs). <B>Design/methodology/approach</B> – The melting activities of two solders near their melting points on copper substrates are visualized in an IR reflow furnace. Reflowed solder joints were analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy. <B>Findings</B> – Reflow behaviors of the solders are similar. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Both solders show a reduced amount of Zn in the solder. Theoretical calculations demonstrate a higher Zn diffusion in the 5E solder; however, the amount of Zn actually observed at the solder/substrate interface is lower than Sn-9Zn solder due to the formation of ZnAg3 in the solder. A thinner IMC layer is formed at the interface in the 5E solder than the Sn-Zn solder. <B>Research limitations/implications</B> – The present work compares the 5E solder only with Sn-Zn solder. Additional research work may be required to compare 5E solder with other solders like Sn-Ag, SnAgCu, etc. to further establish its practical applications. <B>Practical implications</B> – The study ascertains the advantages of 5E solder over Sn-Zn solder for all practical applications. <B>Originality/value</B> – The significance of this paper is the understanding of the relation between reflow behavior of solders and reactivity of different elements in the solder alloys and substrate to form various IMCs and their influence on the formation of IMC layer at solder/substrate interface. Emphasis is provided for the diffusion behavior of Zn during reflow and respective reaction mechanisms. Article literatinetwork@emeraldinsight.com (J. Mittal, K.L. Lin) Tue, 01 Apr 2014 00:00:00 +0100