Nanosolders for Low Temperature, Lead-Free Microelectronics Assembly

Carol Handwerker

Professor, School of Materials Engineering, Purdue University

Abstract: 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.

About Carol Handwerker:

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

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

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

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.

·                    

··                    

··                     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.

Main 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.   

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.   

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..

12..