Citation
Fu Guo, P. (2009), "Lead-Free Solders and Emerging Interconnect and Packaging Technologies at the 138th TMS Annual Meeting and Exhibition, 16-19 February 2009, Moscone West Convention Center, San Francisco, California, USA", Soldering & Surface Mount Technology, Vol. 21 No. 4. https://doi.org/10.1108/ssmt.2009.21921dac.002
Publisher
:Emerald Group Publishing Limited
Copyright © 2009, Emerald Group Publishing Limited
Lead-Free Solders and Emerging Interconnect and Packaging Technologies at the 138th TMS Annual Meeting and Exhibition, 16-19 February 2009, Moscone West Convention Center, San Francisco, California, USA
Article Type: Conferences and exhibitions From: Soldering & Surface Mount Technology, Volume 21, Issue 4
The TMS Annual Meeting and Exhibition, the ultimate networking experience for materials professionals, was held from 15-19 February 2009 in San Francisco, California, USA. Nearly 4,000 business leaders, engineers, scientists and other materials professionals from 68 countries were attracted to attend this meeting. As one of the most important symposia of the meeting, the Pb-free Solders and Emerging Interconnect and Packaging Technologies Symposium covered all the hot spots in the Pb-free materials and packaging processes. This symposium was organized by Sung K. Kang (IBM Corporation), Iver E. Anderson (Iowa State University), Srinivas Chada (Medtronic), Jenq-Gong Duh (National Tsing-Hua University.), Laura Turbini (Research in Motion) and Albert Tzu-Chia Wu (National Central University). It was sponsored by the Mineral, Metals and Materials Society (TMS), TMS Electronic, Magnetic and Photonic Materials Division and the Electronic Packaging and Interconnection Materials (EPIM) Committee.
The Pb-free Solders and Emerging Interconnect and Packaging Technologies Symposium involved a wide range of subjects, such as effects of surface finishes and advances in interconnects, electromigration reliability, microstructure and mechanical properties of the solder joint, interfacial reactions and phase transformation, modeling and tests methods in reliability evaluation, tin whisker formation and so forth. Four main parts, including the TMS2009 Pb-free solder and technology workshop, the poster session, the technical program and the EPIM Committee meeting, constituted the whole conference. Nearly 200 attendees participated in the workshop and the seven sessions of the technical program. Over 100 papers were presented during the conference and 26 posters were exhibited in the poster session.
The Pb-free Solder and Technology Workshop was held in the San Francisco Marriott Hotel on 15 February. Holding a one-day workshop before the technical program has become a tradition over the last five years ago. Over 140 attendees participated in the workshop at both presentations in the morning and the panel discussion in the afternoon. This year’s workshop was organized to serve as the industry roadmap for Pb-free solders in high reliability packaging and interconnections, with current industry needs and concerns serving as a driving force for research. Four presentations focused on Pb-free solder from the industry point of view were delivered in the morning session. For example, an insight for consumer electronics and automobile sector was given by Darrel Frear (Freescale Semiconductor); challenges in the networking and telecommunication industry for high reliability was delivered by Dave Towne (Cisco) and Greg Henshall (HP). The four presentations provided a thorough and deep analysis of what the high reliability concerns are and provided suggestions on how to approach these problems from an academic point of view.
In the followed afternoon session, particular topics were further discussed. J.W. Morris from University of California, Berkeley, presented the influence of imposed current on the creep of Sn-rich Pb free solder; Professor Chen from Purdue University presented stress-strain behaviour of Pb-free solders over various strain rates; John Osenbach from LSI Cooperation gave the presentation on creep and Sn whiskers; Polina Snugovsky from Celestica talked about reliability issues related to assembly and assembly rework parameters; and Thomas R. Bieler from Michigan State University presented an interesting topic regarding the role of elastic and plastic anisotropy on damage nucleation in lead free solder joints. Through presentations and extensive discussion regarding these key topics, this workshop established a bridge between companies producing high reliability products and research groups in academia, national laboratories and consortia and provided new directions in future study serving to satisfy the industry applications (Figures 1 and 2).
The poster session for Pb-free solders and emerging interconnect and packaging technologies was held after the workshop in the Moscone West Convention Center. It was the first time that the Pb-free solder symposium had run poster sessions in the technical program. In total, 26 posters regarding the interfacial reaction, the reliability of the solder joint, the tin whisker and electromigration were exhibited in this session. In order to stimulate the interests of the participants, the session chairs set up the awards for the top three prize winners. Di Xu from University of California, Los Angeles (UCLA), by virtue of her poster-structure properties of grain boundary in Cu affected by nanotwins, became the laureate of the first prize. Her study discovered that the hardness of copper near the grain boundaries which intersect with nanotwin boundaries is much higher than those of normal grain boundaries and bulk copper and the triple point where a twin intersects a grain boundary may play the key role in changing the structure and properties of the grain boundaries in the copper having a high density of nanotwins. In addition, the posters, aging-informed constitute models for steady state creep-plasticity in Sn3.8Ag0.7Cu solder alloy by Kaushik Mysore from Purdue University and accelerated growth of Tin Whiskers from evaporated films by Jing Cheng from University of Rochester were awarded the second and the third prize, respectively.
On the first day of the conference, there were two sessions: the symposia on electromigration reliability and the symposia related to fundamental properties, interfacial reactions and phase transformation. In total, 15 presentations were given in the electromigration reliability session, including the invited talk from King-Ning Tu of UCLA. Given that the current crowding occurs at the location where the current enters or leaves the solder bump due to the unique line-to-bump configuration of the flip chip induce the electromigration of the solder joints and in turn the concentration of the compressive stress which is attributed to the Sn whisker or hillock at the anode, new measures used to detect such stress should be acquired to facilitate the study. In the talk, King-Ning Tu reported that the stress migration can be investigated by means of the X-ray diffraction by micro beam synchrotron radiation, since the transient stress build-up in the Sn matrix has been detected and the effect of IMCs in slowing down the growth of the tin whisker and hillock has been presented through the observation by X-ray microdiffraction. Additionally, in this session, Di Xu from UCLA gave the presentation related to the electromigration in tin-copper, tin-silver and eutectic tin-lead flip chip solder joint; Albert Wu from National Central University reported the stress evaluation on solder stripe under electromigration; Hsiao-Yun Chen of National Chiao Tung University shared his study relevant to the effect of UBM on the eletromigration lifetime of SnAg solder joints and electromigration-induced failures on Ni/Cu Bi-layer bond pad. Besides, the in situ studies of electrical current induced whiskers studied by Andre Lee of Michigan State University also was presented in the session.
On the second day of the conference, one of the two sessions was mainly focused on the effects of surface finishes and advances in interconnects. The surface finishes have been applied in the practical solder joints widely and various evidence has shown that the surface finishes play an important role in the reliability of the solder joints due to the interfacial reactions between the finishes and the Pb-solders. Meanwhile, the interconnect technique is also a significant research direction. Thus, this theme stimulates the extensive interests of researchers and in turn numerous studies were performed in this branch. In this session, 13 presentations were delivered. The invited talk given by John Osenbach of LSI Corporation chiefly covered the corrosion of ENIG surface finishes contributed by the electroless nickel layer. According to his talk, a second phase particle contamination was present in the electroless nickel, Ni (P) layer on the substrates that have corroded ENIG but not on the substrates with non-corroded ENIG. These particles are almost the same composition as the Ni (P) layer. They can ultimately lead to Ni (P) corrosion for they can induce the modification of the surface topology as well as creating low-density interfaces. Furthermore, in this session, interconnection techniques, such as ultrasonic bonding and soldering, were presented by Shankar Srinivasan from the Edison Welding Institute and Jong-Bum Lee from Sungkyunkwan University.
In another session relevant to the tin-whisker formation and mechanical properties of solders/solder joints, 15 authors shared their findings with attendees. K. Subramanian from Michigan State University was invited to give the talk about the structure-property evaluation in Sn-based solders with nano-structured chemicals. John Osenbach from LSI Corporation reported grain orientation effects on the temperature cycling stability of 180 μm pitch Pb-free bump interconnects. Jung-Kyu Han from UCLA proposed competing mechanisms between intermetallic compound formation and whisker/hillock growth in Pb-free solder joints.
On the third day of the conference, reliability and microstructure development and modeling test methods were presented and discussed. The talk given by Polina Snugovsky, microstructure and reliability comparison of different Pb-free alloys used for wave soldering and rework, covered the influence of the microstructure after assembly and rework on Weibull plot parameters and failure mode, the analysis regarding the interconnect defects and recommendations on alloy applications. Besides, a novel solder technology based on gold nanoparticle ink was reported by Teymur Bakhishev from the University of California, Berkeley. According to the study of the author, optimized gold inks are able to sinter at temperatures as low as 120°C and achieve conductivities of up to 70 per cent of bulk. Once sintered, the metallic structure reverts to bulk-like properties and approaches bulk reliability and performance. Thus, the nanoparticle-based solders would operate at much lower homologous temperatures as compared to alloy-based solders. From the view point of the author, the nanoparticle inks are promising candidates as next-generation solders.
The conference lasted until the morning of Thursday, 19 February, which was the final day of the TMS2009 Annual Meeting. An additional 15 papers in the electromigration, microstructure and mechanical properties fields were presented.
The foregoing outline regarding the conference has merely given a few examples of the presentations from this large, well-attended and highly successful conference. People from different countries, regions and institutes made deep and extensive exchanges and held discussion in all aspects of the Pb-free solders and packaging technologies. There is no denying that the conference brought about benefits to both the authors of the papers and the attendees. Indisputably, the conference served as the impetus to stimulate the further development of Pb-free solder and advanced technologies in interconnects by inspiring the innovation and creativity of the researchers.
The EPIM Committee is the head of the Pb-free solder symposium of the TMS Annual Meeting. In order to conclude the past work and prepare for the next conference, the committee holds its annual meeting during the conference every year. This year the committee meeting was held on 17 February 2009 in the Marriott Hotel and was called to order by Chair C. Robert Kao from the National Taiwan University. In the meeting the committee reviewed the overall publication activities, educational activities and technical symposia programming round the year and put forward a revision in tenure of the officers of the committee.
With all the data and information regarding the conference, every individual must be informed that the conference was a very successful event in which all the attendees learned what they needed, reported what they want to share and discussed what they are interested in. All the novel materials, techniques, information introduced and discussed in this conference serve to develop both the academic and industrial fields in Pb-free solder materials and emerging interconnects and packaging technologies. Without any doubts, the conference, with such high standards, must take enormous efforts of the organizers, especially the EPIM Committee. Thus, appreciation and congratulations should be given to all the people who were engaged in preparation of the conference.
Professor Fu GuoCollege of Materials Science and Engineering, Beijing University of Technology