Nanosolders for Low Temperature, Lead-Free Microelectronics

Assembly

A major obstacle facing the implementation of Sn-Ag-Cu lead-free solders for temperature-sensitive microelectronic devices is the higher melting point of Sn-Ag-Cu solders compared to Sn-Pb eutectic and near-eutectic solders. To overcome this obstacle, metallic nanoparticles pastes are being fabricated and studied by Purdue University and MetaMateria Partners, in conjunction with Indium Corporation and Motorola,  as part of the International Electronics Manufacturing Initiative (iNEMI) Pb-free Nanosolder Project. The goal of the iNEMI Nanosolder Project is the development of lower melting point Sn-Ag-Cu solder pastes that, after nanoparticle coalescence, form bulk solder joints and therefore exhibit solder joint reliability comparable to conventional Sn-Ag-Cu solders. By using small particle effects on melting, it is hoped that the melting point of lead-free solder alloys can be lowered at least as low as the melting point of Sn-Pb eutectic solders. As part of the process of developing a “nanosolder,” the melting, coalescence, and solidification behavior of metallic tin and tin alloy nanoparticles in flux has been characterized by differential scanning calorimetry (DSC) and by characterizing the metal solidified on copper substrates following paste melting.. The impact of particle size and surface condition on the melting, coalescence, and solidification behavior of metallic nanoparticles will be discussed with regards to the overall goal of developing a widely applicable and commercially viable nanosolder. 

Nanoparticle-enabled Printing of Large-Area Electronic Hierarchical Systems

New low temperature, nanoparticle-based printing processes for inorganic semiconductors are being investigated for fabrication of low cost, all-printed devices for wireless applications, such as WiFi and cellular communications.  Although inorganic semiconductor nanoparticles may sinter at lower temperatures than their bulk counterparts, these temperatures are generally significantly higher than 150°C, the maximum processing temperature allowable with low cost polyester or paper substrates.  

To enhance inorganic nanoparticle sintering at low temperatures, two different approaches are being developed.  First, for oxide semiconductors, printed, porous nanoparticle films are exposed to oxide precursors that precipitate directly as oxide onto the existing oxide nanoparticles and lead to increased particle-particle contact and higher carrier mobilities than the original films.  The second approach is to sinter core-shell nanoparticles consisting of a semiconductor core and a metal shell in a diffusion process related to metal-mediated crystallization observed in semiconductor-metal systems.  Current progress in device performance and in the development of these two approaches will be described.

背景材料：

Prof. Carol A. Handwerker

教授，材料工程学院，美国普渡大学西拉法叶校区，印地安那州

Professor, School of Materials Engineering, Purdue University, 501 Northwestern Avenue, West Lafayette, IN 47907-2044. Tel. (765) 494-0147. E-mail: handwerker@purdue.edu

Carol 教授的研究领域：

Research Areas for Carol Handwerker:  Materials and processes for microelectronics and nanoelectronics, including the thermodynamics, solidification processes, interface motion, and wetting of lead-free and mixed solders, tin whisker formation, reliability of lead-free solders and the relationship between reliability, composition, and microstructure, nanoparticles for printed electronics, and microstructure evolution during sintering and grain growth.

关于美国普渡大学：

About Purdue:  Purdue University is one of the nation’s leading land-grant universities, with a full range of academic majors and an enrollment of 37,000 students.  The College of Engineering at Purdue consists of over 6,000 undergraduate students, 2,400 graduate students, and 340 faculty members. The Purdue College of Engineering is enjoying unprecedented growth and revitalization in terms of faculty, facilities, and educational programs.  Eight signature areas including nanotechnology, advanced materials and manufacturing, and global sustainable industrial systems are part of new multidisciplinary initiatives.   For more information, see https://engineering.purdue.edu/Engr/Research/Initiatives/.  In addition, the College of Engineering is in the midst of a $400 million expansion and modernization of 50 percent of its engineering facilities. Included is significant investment in Discovery Park, a group of interdisciplinary research, learning, and engagement centers clustered around themes critical to the university and the State of Indiana.  For additional information, see http://www.purdue.edu/dp/index.php.

关于材料工程学院：

About the School of Materials Engineering: The School of Materials Engineering at Purdue is composed of 22 faculty members covering an extremely broad range of interdisciplinary materials science and engineering research, from nano and bio technologies to structural composites.  The School of Materials Engineering has almost doubled in faculty size over the past five years, and its graduate and undergraduate programs are growing in response. 

Carol Handwerker 教授简介

Carol A. Handwerker

Professor, School of Materials Engineering, Purdue University, 501 Northwestern Avenue, West Lafayette, IN 47907-2044. Tel. (765) 494-0147. E-mail: handwerker@purdue.edu

a. Education

Wellesley College                Art History                  B.A. 1973

Massachusetts Institute of Technology       MSE                            S.B 1978

Massachusetts Institute of Technology       Ceramics                     S.M. 1978

Massachusetts Institute of Technology       Ceramics                     Sc.D. 1983

Massachusetts Institute of Technology       Electronic Packaging           Postdoc – 1983-84

b. Professional Experience

Purdue University

Professor               School of Materials Engineering and DEEE               August, 2005 to present

National Institute of Standards and Technology

Division Chief      Metallurgy Division                               1996-2005

Group Leader     Materials Structure and Characterization Group 1994-1996

Metallurgist        Materials Processing Group                      1984-1994

c. Synergistic Activities

·                                          Assists microelectronics industry in worldwide conversion to lead-free solders for printed wiring boards through fundamental research in thermodynamics, in wetting and kinetics of phase transformations, and in the relationship between solder microstructure and joint reliability and through developing the link between many fundamental science concepts and high volume electronics manufacturing.  Co-chaired iNEMI Alloy Development Group (1999-2002) (www.iNEMI.org) of major US industrial consortium for conversion to lead-free solders in printed wiring boards and components; participant in iNEMI Processing and Reliability Groups. Organized and facilitated roadmapping workshops on R&D needed for successful conversion to Pb-free solders. Collaborating with Motorola, NanoDynamics, Indium, Corp., and others on development of next-generation interconnects and materials and processes for printed electronics.

·                                          Works closely with defense and aerospace industry and with high reliability microelectronics community in understanding the implications of Pb-free materials and processes for systems used in high reliability and harsh environments.

·                                          Member of iNEMI Technical (Advisory) Committee that develops and integrates iNEMI’s technology strategies and plans and coordinates all iNEMI technical activities.  Co-chair of iNEMI Research Committee, whose role is to stimulate research that will address gaps identified by iNEMI roadmaps. The Research Committee is responsible for organizing and publishing the iNEMI research priorities, presenting those priorities to research institutes and funding organizations, identifying funding opportunities, monitoring industry progress toward roadmap goals, and monitoring progress in nanotechnology research.

·                                          Leadership Team of iNEMI Initiative on Halogen Free and Beyond: Demonstrating Corporate Social Responsibility (CSR), with a focus on sustainability in the global microelectronics supply chain, from raw materials through end-of-life disposal, as well as from considerations of sustainability in materials and manufacturing research and in product design.

d. Publications

1.        Experimental and thermodynamic assessment of Sn-Ag-Cu solder alloys, K. W. Moon,  W. J. Boettinger,  U. R. Kattner,  F. S. Biancaniello,  C. A. Handwerker, Journal of Electronic Materials 29 [10] 1122-1136 (2000).

2.        Reliability of Pb-Free Solders, C. A. Handwerker, D. A. Noctor, and G. Whitten, Environment-Friendly Electronics: Lead-Free Solders, Ed. Jennie S. Hwang, Electrochemical Publications, Isle of Man, British Isles, 2001, 566-589.

3.        Major International Lead (Pb)-Free Solder Studies, C. A. Handwerker, K. Suganuma, E. de Kluizenar, and F. R. Gayle, Issues and Implementation of Pb Free Technology in Microelectronics, Eds. K. Puttlitz and K. Stalter, McGraw Hill/IEEE, 2004.

4.        Transitioning to Pb-Free Assemblies, C.A. Handwerker, Circuits Assembly, April 2005, p. 39 and full article in Printed Circuit Design and Manufacturing, March 2005 17-18, continued on 23. (and other articles in Circuits Assembly and CircuiTree trade magazines.)

5.        Observed correlation of Sn oxide film to Sn whisker growth in Sn-Cu electrodeposit for Pb-free solders, K.W. Moon, M.E. Williams, O. Kongstein, G.R. Stafford, C. A. Handwerker, W.J.  Boettinger, Journal of Electronic Materials, 34 [9] L31-L33 Sept. 2005.

6.        The Effect of Bi Contamination on the Solidification Behavior of Sn-Pb Solders, K.W. Moon, U.R. Kattner, and C.A. Handwerker, Journal of Electronic Materials, 2007.

7.        Lead-Free Electronics: iNEMI Projects Lead to Successful Manufacturing. ed.: E. Bradley,   C. A. Handwerker, J. Bath, R. Parker, and R. Gedney, IEEE/Wiley Press (October, 2007).

8.        Fundamental Properties of Pb-Free Solder Alloys, C. A. Handwerker, U. R. Kattner, and K.W. Moon, in Lead Free Soldering, ed. Jasbir Bath, Springer Publications, September, 2007.

9.        Alloy Selection, C. A. Handwerker, U. R. Kattner, K. W. Moon, J. Bath, and P. Snugovsky, in Lead-Free Electronics: iNEMI Projects Lead to Successful Manufacturing. ed.: Bradley, E.,  Handwerker, C., Bath, J., Parker, R., and R. Gedney, IEEE/Wiley Press (October, 2007).

10. Geometric Models of Crystal Growth, J. E. Taylor, J. W. Cahn, C. A. Handwerker, Acta Metallurgica et Materialia 40 [7] 1443-1474 (1992). Society 82 [7] 1889-1900 (1999.

11. Equilibrium Shape of Internal Cavities in Ruby and the Effect of Surface Energy Anisotropy on the Equilibrium Shape, J.-H. Choi, D.-Y. Kim, B.J. Hockey, S.M. Wiederhorn, J.E. Blendell, C.A. Handwerker, J. Amer. Ceram. Soc., 85[7] 1841-4, 2002.

12. Singular Grain Boundaries in Alumina and Their Roughening Transition, C.-W. Park, D.-Y. Yoon, J.E. Blendell, C.A. Handwerker, J. Amer. Ceram. Soc. 86[4] 603-11, 2003.

e. Collaborators

J. Bath, Solectron Corporation; W. J. Boettinger, National Institute of Standards and Technology; E. Bradley, Motorola; P. Brazis, Motorola; D. Fritz, SAIC/MacDermid; D. Gamota, Motorola; U. R. Kattner, National Institute of Standards and Technology; N.-C. Lee, Indium Corp.; D. Love, Sun Microsystems; K. W. Moon, University of Maryland; R. J. Parker, Delphi Corporation; A. Rae, Nanodynamics; R. Revur, Metamateria Partners, S. Sengupta, Metamateria Partners, A. Skipor, Motorola, J. Smetana, Alcatel; P. Snugovsky, Celestica; M. Williams, National Institute of Standards and Technology.

Postdoctoral Advisor

J. W. Cahn, National Institute of Standards and Technology

f. Additional Information

Fellow, ASM International

Fellow, American Ceramic Society

Member, National Materials Advisory Board, National Research Council