Program Organizers: M. McCormack, AT&T Bell Laboratories, Rm lA- 123, 600 Mountain Ave., Murray Hill, NJ 07974; S. K. Kang IBM, T. J. Watson Research Center, P. O. Box 218, Yorktown Heights, NY 10598; M. R. Notis, Department of Materials Science and Engineering, Lehigh University, 5 East Packer Ave., Whitaker Laboratory, Bethlehem, PA 18015- 3195; K. N. Tu, Department of Materials Science and Engineering, UCLA, Los Angeles, CA 90095-1595
Monday, AM Room: Grand K
February 5, 1996 Location: Anaheim Marriott Hotel
Session Chairperson: M. R. Notis, Department of Materials Science and Engineering, Lehigh University, 5 East Packer Ave., Whitaker Laboratory, Bethlehem, PA 18015-3195
8:30 am Invited
ELECTRICALLY CONDUCTING ADHESIVES FOR MICROELECTRONIC PACKAGING APPLICATIONS: S. K. Kang, IBM, T. J. Watson Research Center, PO Box 218, Yorktown Heights, NY 10598
Solder interconnection technology is in need of alternatives to address not only environmental issues associated with lead (Pb) abatement and elimination of fluxes and flux cleaning solvents, but also the technical challenges related to fine pitch assembly and low temperature processing. In the electronic industry, two different groups of materials are being investigated currently for the possibility of substituting the Pb- containing solder materials; Pb- free solder alloys and electrically conducting adhesives. The present paper discusses the development and applications of electrically conducting adhesive materials. An electrically conducting adhesive is made of metallic filler particles dispersed in the matrix of a polymer resin. Depending on the mode of electroconduction, electrically conducting adhesives can be categorized into two groups; isotropic and anisotropic materials. Silver- filled epoxy material used in die attach applications is the most common example of an isotropic material. Anisotropic conducting film (ACF) used in liquid crystal display (LCD) applications belongs to the category of anisotropic conducting material. In this talk, both materials are discussed in terms of their current status, trends, and challenges for further development.
8:55 am Invited
ANISOTROPICALLY CONDUCTIVE INTERCONNECTION MATERIALS FOR MICROELECTRONIC PACKAGING: S. Jin, M. McCormack, AT&T Bell Laboratories, Murray Hill, NJ 07974
The enormous imbalance between the micron resolution at the IC device level and the hundreds- of- micron features at the interconnection/packaging level leads to ineffecient device integration. In order to make the electronic devices and products smaller, faster, and cheaper, a substantial increase in interconnection density is necessary. In this paper, some recent progress in the development of new, anisotropic conductive materials for high density interconnections will be described. The possibility of interconnection schemes using micro- solder arrangement, as well as metalpolymer composites, will also be discussed.
9:20 am Invited
DEVELOPMENT OF NEW SOLDER BONDING MATERIALS FOR ELECTRONIC PACKAGING APPLICATIONS: R. Emigh, J. Li, M. Pinter, Johnson Matthey Electronics, Spokane, WA 99216
New solder based bonding materials (Pb containing and Pb- free) are being developed for advanced electronic applications. These are targeted for use where reduced temperature and low stress bonding is required. Work is focused on developing materials that can tolerate subsequent reflow temperatures that are above the initial bonding temperature. The materials are also designed with enhanced thermal conductivity and fatigue resistance.
9:45 am Invited
MICROSTRUCTURAL MECHANISMS OF ELECTROMIGRATION FAILURE IN AL- CU THIN- FILM CONDUCTING LINES: J.W. Morris, Jr., C. Kim, S.H. Kang, Department of Materials Science, University of California Berkeley, and Center for Advanced Materials, Lawrence Berkeley Laboratory, CA 94720
This paper discusses microstructural control of internal electromigration failure in narrow Al- Cu thin film conduction lines on Si. The lines of interest have near- bamboo structures; their microstructures consists of polygranular segments that are terminated by "bamboo" grains that span the line. The common mode of electromigration failure mode is a transgranular separation of the bamboo grain that terminates its longest polygranular segment. The polygranular segment and terminating grain are swept free of Cu, which is gathered into a Cu precipitate at the opposite end of the segment. The time- to- failure increases exponentially with the inverse of the segment length. These observations suggest three ways for increasing the lifetime of narrow Al- Cu- Si lines; low- temperature pre-aging to stabilize the distribution of Cu, high- temperature pre- aging to narrow the distribution of polygranular segment lengths, and periodic current reversal to reverse Cu flow. All three methods have been tried with some success. This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract No. DE- AC03- 76SF00098.
10:10 am BREAK
10:25 am Invited
EFFECT OF THERMAL AGING ON THE MICROSTRUCTURE AND RELIABILITY OF BALL GRID ARRAY (BGA) SOLDER JOINTS: E. E. Bradley, P. Lall, K. Banerji, Motorola Advanced Manufacturing Technology Center, Land Mobile Products Sector, Ft. Lauderdale, FL 33322
A major cause of solder joint failures in electronic assemblies is due to the high strain rate effects of bending. Since solder is very strain- rate sensitive, solder joint failures caused during high strain rate deformation of the printed circuit board are often located at the interfaces where the solder has wetted to the PCB metallization. The formation and growth of intermetallics at these interfaces can substantially impact package- level reliability. This study investigated the solder joint reliability of Ball Grid Array (BGA) packages under three point bending as a function of aging. Parts were aged between 75deg.C and 125deg.C for up to 1000 hours and then reflowed onto printed circuit boards using a conventional surface mount profile. The relationship of the failure modes in three point bending to interfacial microstructural development will be discussed.
10:50 am Invited
MATERIALS- BASED MODEL TO PREDICT SOLDER JOINT LIFETIME IN ADVANCED ELECTRONIC PACKAGES: D. R. Frear, S. N. Burchett, M. K. Neilsen, Sandia National Laboratories, Albuquerque, NM 87185
The long term reliability of solder joints in electronic packaging is a critical competitiveness issue. The reliability of an electronic system is frequently limited by the failure of soldered electrical interconnections due to thermomechanical fatigue. As an added complication, thermomechanical fatigue tests at Sandia have clearly shown that the microstructure of the solder undergoes a heterogeneous coarsening process followed by failure through the coarsened regions. A microstructurally based constitutive model has been developed at Sandia to simulate thermomechanical response including microstructural evolution leading to prediction of the reliability and lifetime of solder joints. The metallurgical inputs for this model are: the constitutive relations of the solder in mathematical form and a quantitative relation of the solder microstructure as it evolves during thermomechanical fatigue. The microstructural state variables are then incorporated into the temperature- dependent, viscoplastic constitutive framework in a finite- element code. A time integration algorithm for the complete constitutive model is implemented into JAC3D, a three- dimensional finite- element code. The output of the simulation of three dimensional stress and strain and the solder microstructural evolution will be presented for a variety of solder joint designs. We present the metallurgical results that are used in the finite element model and simulation results of the model. Computational and experimental results will be presented that examine the effects of a the variety of joint structures used in advanced packages ranging from leadless surface mount, to flip chip, to ball grid array. This work was performed at Sandia National Laboratories, which is supported by the U.S. Dept. of Energy under contract number DE- AC04- 94AL85000.
ADHESION OF THIN TANTALUM NITRIDE FILMS ON Al2O3 AND ALN SUBSTRATES: N.R. Moody, D. Medlin, D. Norwood, Sandia National Laboratories, Livermore, CA 94551-0969; S. Venkataramant, Applied Materials, Santa Clara, CA 95054
Thin tantalum nitride films are often used in microelectronic applications because of their long term stability and low thermal coefficients of resistance. however, the lack of microstructure and adhesion data of these films on AL2O3 and ALN substrates limits our ability to assess reliability. We therefore combined nanoindentation, continuous microscratch testing, and high resolution transmission electron microscopy to determine structure- property relationships in thin tantalum nitride films on single crystal sapphire and polished aluminum nitride substrates. The films were sputter- deposited to a thickness of 100 nm on each type of substrate and then tested at room temperature. The results revealed that there was a difference in the structure, morphology, and properties of the films. In this presentation, the results will be discussed and used to show how interface structure and film morphology affects the resistance to fracture of thin tantalum nitride films. This work supported by U.S. DOE Contract DE- AC04- 94AL85000.
INFLUENCE OF LASER ANNEALING ON ELECTROPHYSICAL CHARACTERISTICS METAL- SILICON CONTACT UNDER IRRADIATION IN CARBON- CONTAINING LIQUIDS: A. M. Chaplanov, A. N. Shibko, Institute of Electronics BAS, 220090, 22, Logoiskii Trakt, Minsk, Belarus
Much attention has been given to physico-
processes which occur in thin films under irradiation with highpowered laser
beams owing to a wide use of such films in microelectronics. Peculiarities of
phase composition and electrophysical properties of titanium-
compositions under laser treatment in hydrocarbon-
environment have been studied. It is found that the use of certain aromatic
hydrocarbons (toluene, styrene, etc.) favors synthesis of metal carbides. The
use of benzene does not result in carbide synthesis, even though it causes
structural changes in the films. Benzene serves as a protective medium against
laser damage and formation of carbides in the films. Laser annealing of T-
systems in aromatic hydrocarbon medium results in changes of electrophysical
parameters of the contacts due to changes in the phase composition and
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