Editorial
Article Type: Editorial From: Soldering & Surface Mount Technology, Volume 23, Issue 2
Welcome to Volume 23, Issue 2 of Soldering & Surface Mount Technology(SSMT)in which there are six papers covering a diverse range of subject matter from solder formulation to testing and end-user reliability requirements. In this issue, while Europe is well represented with papers from the UK (2), Hungary and Finland, there are also authors from Ghana and Malaysia, who help to contribute to the truly global coverage of the journal.
Nanotechnology and the potential for nanoparticles to offer enhanced performance have been the subject of a huge amount of research, especially over the last ten years and, not surprisingly, there has been growing interest in the use of nanoparticle additions to improve the performance of solders. The first paper in this issue reports on the results of an investigation into the effects of adding copper nanoparticles to Sn-3.5 Ag solder. In this work, by Aemi Nadia and A.S.M.A Haseeb from the Department of Mechanical Engineering at the University of Malaya in Kuala Lumpur, the authors report that the melting temperature, wetting behaviour and hardness of the chosen solder could all be improved by the addition of the copper nanoparticles.
The second paper is from the University of Greenwich at Chatham in the UK and it details the influence of particle size distribution and flux medium on the creep recovery performance of lead-free solder pastes. In the work reported,lead-free solder paste formulations were characterised utilising viscometry and oscillatory methods, after which creep/recovery investigations were conducted to determine the recovery performance. The results from the study highlight that a solder paste’s formulation can have a significant impact on the creep/recovery performance.
Ionic contamination can lead to serious reliability issues on electronics assemblies, especially when they are required to operate in high-humidity environments and where there may be high local electric field gradients that can lead to dendritic growth and corrosion of conductors, etc. Consequently, the subject of cleaning and cleanliness testing has been one that has received a lot of attention over many years and, as feature sizes continue to decrease, it is still a very important issue. In the next paper, the focus moves to this type of testing and, in particular, to the effectiveness and sensitivity of different cleanliness verification tests for post-soldered printed circuit board assemlbies (PCBAs). Kong Hui Lee, Rob Jukna, Jim Altpeter and Kantesh Doss report on a study in which PCBAs were subjected to different flux residue cleaning times. Cleanliness levels were assessed using a range of techniques to provide results capable of differentiating different sensitivity levels for each test. The results from this work help to provide an understanding of current industry practice for ionic contamination detection using verification tests with different detection sensitivity levels.
The fourth paper details the results of an investigation into the stability of automatic X-ray inspection systems and is by István Latos and Mihály Janóczki from the Department of Electronics Technology at Budapest University of Technology and Economics in Hungary. This study had the objective of developing a new method for evaluating the capabilities of state-of-the-art X-ray inspection machines. The work investigated the effectiveness and appropriateness of the present methods of calibration. The paper describes the adjustments required to achieve ideal optimized perfomance and a scientifically substantiated method is presented that can be used during the automated X-ray inspection of devices.
With the ever-increasing demands for performance enhancements in electronics and the continuing move to smaller pitches, components and vias have come to the realisation that basic SAC alloy formulations are not always able to satisfy the needs of the industry. Consequently, there has been growing interest in the use of additional alloying elements to improve performance via doping. The fifth paper reports one such approach and is the result of a collaborative effort from Finland by O. Nousiainen, O. Salmela, J. Putaala and T. Kangasvieri on an investigation into the enhanced thermal fatigue endurance and lifetime prediction of lead-free LGA joints in LTCC modules. The work, undertaken by the University of Oulu and Nokia Seimens Networks, describes the effect of indium alloying on the thermal fatigue endurance of an SAC alloy in low-temperature co-fired ceramic modules with land grid array joints. It was found that the addition of indium increased the lifetime of the LGA joints by 15 per cent. Alloying with indium changed the composition, size and distribution of the intermetallic compounds within the solder matrix.
Finally, for this issue, the sixth paper, by G. Takyi, E. Amalu, and P.K Bernasko, reports on the results of a collaborative study into the effect of solder joint integrity on the thermal performance of a thermo-electric cooler unit. The thermal performance the unit was evaluated using a heat pump test and the results were compared with those from scanning acoustic microscopy (C-SAM). The C-SAM observations were able to confirm a good solder joint at the interface between a thermo-electric cooler and its housing in the case of a device that gave a good heat pump test result and poor solder joints (gross de-lamination)at the interface between the thermo-electric cooler unit and its housing in the case of a device that yielded a poor heat pump test result. The heat pump test results showed a strong correlation with the C-SAM results and the results were used to qualify the post-vacuum soldered laser pump devices for their manufacturer.
As always, I hope that you enjoy reading these papers and the rest of the contents in this issue and that you find them both interesting and useful. I have previously mentioned that the journal is looking to increase its team of paper reviewers and I would still be happy to hear from those of you who have an interest in reviewing the latest novel research that is submitted for publication in SSMT. I am also pleased to report that the paper submission process for this journal has recently changed and authors are now able to submit their papers electronically online. The journal is now using ScholarOne Manuscripts for both paper submissions and their subsequent reviewing. Please visit web site: http://mc.manuscriptcentral.com/ssmtfor further information and to create a user account. Finally, I always appreciate feedback and comments from subscribers about the journal and its contents, etc. I can be contacted by e-mail at: m.goosey@lboro.ac.uk
Martin Goosey
