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IBM Journal of Research and Development

Issue 5 • Date Sep. 1988

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Displaying Results 1 - 14 of 14
  • Editor's Note

    Page(s): 581
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    Freely Available from IEEE
  • Ion transport through protective polymeric coatings exposed to an aqueous phase

    Page(s): 582 - 590
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    This paper describes the status of work in our laboratory to develop an improved understanding of the chemical and physical aspects of ion transport through polymeric coatings which are exposed to an aqueous phase. View full abstract»

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  • Characterization of PdSn catalysts for electroless metal deposition

    Page(s): 591 - 602
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    A set of electrochemical techniques has been developed to measure the component concentrations and the catalytic activity of the PdSn seeder solutions used to activate insulating substrates for the electroless deposition of Cu. The concentration of Sn(II) was calculated from the limiting current for Sn(II) oxidation, that of Sn(IV) from the difference between the Sn metal-deposition limiting current and the Sn(II) limiting current. The palladium concentration was determined by a stripping analysis after Pd deposition from an oxidized seeder solution. The catalytic activity of the PdSn catalyst was estimated by measuring its activity for the electro-oxidation of formaldehyde (the reducing agent used in the electroless Cu bath) or by the cyclic voltammetric response of a seeded electrode in an inert electrolyte. The cyclic voltammetric technique and transmission electron microscopy examination were used to evaluate various accelerating solutions used to increase the activity of the seeder. View full abstract»

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  • Chemistry at interfaces: Electropositive metals on polymer surfaces

    Page(s): 603 - 615
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    This paper presents a study of chemical interactions between polymer surfaces and metal atoms deposited from the vapor phase. Such interactions may play an important role in interfacial metal-polymer adhesion. The chemical nature of the interface formed when an electropositive metal (chromium or cesium) is deposited onto the surface of PMDA-ODA polyimide has been investigated using chemical model studies coupled with photoelectron spectroscopic techniques. X-ray photoelectron spectroscopy, synchrotron-radiation-excited core-level photoemission, and near-edge X-ray absorption spectroscopy were used to analyze changes in polymer surfaces during deposition of chromium and cesium. Chemical model studies using cyclic voltammetry and UV-visible spectroscopy were performed using several simpler polymers or monomeric model compounds which contained structural subunits of the polyimide. Results of these experiments show that chromium (and other electropositive metals studied so far) initially reacts rapidly with the carbonyl groups of polyimide, causing reduction of the dianhydride portion of the polymer, with concomitant chromium oxidation. Continued deposition of chromium onto the reacted polymer surface results in the formation of chromium carbide, oxide, and nitride species, indicating a disruption of the polymer chemical structure. View full abstract»

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  • Characterization of a bis-maleimide triazine resin for multilayer printed circuit boards

    Page(s): 616 - 625
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    The thermosetting resin investigated in this study was a mixture of bis-maleimide and bis-cyanate, frequently referred to as BT (bis-maleimide triazine). For printed circuit board applications, a brominated epoxy resin was blended with BT to impart flame resistance. Resin curing was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated-cell infrared spectroscopy, dynamic mechanical analysis, and microdielectrometry). Differential scanning calorimetry indicated a minimum of two separate reactions. Fourier-transform infrared spectroscopy provided more detailed information on the cross-linking reactions during the curing. The onset of cyclotrimerization was found to appear at 150°C, correlating with one of the peaks observed in the differential scanning calorimetry measurements. Dynamic mechanical methods were used to investigate the viscosity profile during simulated lamination temperature profiles. Microdielectrometry performed simultaneously with parallel-plate rheometry provided further insight into the physical changes that occur during lamination. View full abstract»

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  • Improvement of adhesion of copper on polyimide by reactive ion-beam etching

    Page(s): 626 - 630
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    In this paper we describe the effect of oxygen-reactive ion-beam etching of a polyimide film to enhance its adhesion to an overlying, subsequently deposited copper film. The adhesion strength of the copper to the polyimide could be increased by as much as a factor of 25 as a result of the etching. Near the etching condition which resulted in optimum strength, the failure mode at the polyimide/copper interface changed from adhesive failure to tensile failure. The latter occurred at the “roots” of a “grass-like” surface structure of the ion-etched polyimide film. View full abstract»

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  • Developer-induced debonding of photoresist from copper

    Page(s): 631 - 635
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    We describe the debonding of a polymeric photoresist film bonded to a thin copper substrate as a result of the diffusion of an organic penetrant into the polymer. The diffusion profile (measured by Rutherford backscattering spectroscopy) consisted of a uniformly swollen layer behind a sharp front which propagated into the polymer at a uniform velocity. Debonding always occurred when the front had penetrated about 12 µm into the polymer (about ⅕ its thickness). The debonding was driven by the release of elastic strain energy created by the swelling. View full abstract»

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  • Physical limits to the useful packaging density of electronic systems

    Page(s): 636 - 646
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    Increasing the density of electronic circuits and systems has been a major thrust for many years; the benefits are increased speed, reduced power-delay product, and reduced cost. Most of this effort has been directed toward the chip, but during the last decade system performance has been increasingly limited by packaging, and so emphasis has been shifting in that direction. Initially it was believed that heat dissipation was a serious fundamental limit, but advances in heat-sink technology have effectively eliminated that concern. One of the most serious problems is signal distribution. Although we can fabricate submicron metal lines, such lines are not normally practical as chip-to-chip interconnections because their resistance leads to undue signal delay and distortion; increasing their aspect ratio will increase cross talk. It is not clear what constitutes an optimal configuration, but for metals at room temperature a signal-line pitch of 30 to 40 µm appears practical. For low temperatures, and especially for superconducting lines, the pitch could be made very much finer, leading to greatly improved system density. View full abstract»

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  • Electrical design of signal lines for multilayer printed circuit boards

    Page(s): 647 - 657
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    Key aspects of the electrical design of signal lines for multilayer printed circuit boards used in computers are examined. Illustrative calculations are carried out for several signal-line configurations, and associated means are presented for selecting design trade-offs regarding cross talk and skin-effect-induced delay. View full abstract»

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  • Delocalized bonding at the metal-polymer interface

    Page(s): 658 - 668
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    This paper summarizes our current understanding of the nature of the chemical bond formed at the interface between a deposited metal atom and an underlying polyimide surface. The approach in these studies is based on the use of quantum chemical calculations to interpret photoemission spectroscopy results. By focusing on the initial reaction between a chromium atom and the PMDA-ODA polyimide repeat unit, the bonding is demonstrated to be delocalized, arising from the formation of a charge-transfer complex between the metal atom and the PMDA unit of the polyimide. Stabilization of the complex involves the transfer of electronic charge from the metal d states of chromium to the lowest unoccupied molecular orbital of the π system of the PMDA unit of the polyimide. The complex proposed is energetically favored over that involving a direct local interaction between the chromium atom and one of the carbonyl functional groups. The distribution of single-particle electron energy levels deduced from molecular-orbital calculations can account for the spectroscopy results. The formation of such delocalized metal-polymer complexes is also inferred from a related study of the chromium/PMDA-PDA interface. View full abstract»

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  • Surface analysis and characterization of large printed-circuit-board circuitization process steps

    Page(s): 669 - 681
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    We describe our use of surface-analysis techniques to characterize problems encountered in 1980–1981 in the fabrication of large printed circuit boards for the IBM 3081 processor unit. XPS, AES, SAM, SEM, and optical microscopy techniques were used. The two major areas addressed were (a) corrosion at a photoresist/Cu foil interface during electroless Cu plating of circuit lines which resulted in defects in subsequently formed Cu lines, and (b) surface-chemical aspects of a “single-seed” colloidal Pd/Sn catalytic initiation of electroless Cu plating onto epoxy surfaces. The corrosion mechanism responsible for the line defects was identified, and corrective actions suggested. Changes in surface composition (Pd/Sn ratio), and surface chemical state (Pd0/Pd2+,Sn0 Sn2+,4+) as a function of process step were correlated with plating effectiveness and led to a means of increasing the surface Pd0/Sn ratio by as much as an order of magnitude. View full abstract»

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  • Elastic and viscoelastic behavior of a magnetic recording tape

    Page(s): 682 - 694
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    The mechanical behavior of a trilayer Mylar-based magnetic recording tape has been studied by three complementary methods, applied either to the complete tape or to samples prepared by the selective removal of its front or back coatings. One method provided tensile stress-strain and creep data, another exploited the phenomenon of thermal curling, and a third or mandrel method was used to measure relaxation and recovery in simple bending. Despite the large relative thickness of the Mylar substrate, both the initial stiffness and subsequent relaxation behavior of the tape were strongly influenced by the surface magnetic coatings, and particularly by the oriented and calendered frontcoat, which exhibited elastic anisotropy and an enhanced longitudinal Young's modulus of up to five times that of the Mylar core. As a consequence, the magnetically active frontcoat emerged as the most highly stressed component of the tape, and initially supported almost half of an imposed tensile load. The high initial modulus of the oriented and calendered frontcoat was attributed to the reinforcement provided by the magnetic oxide dispersed in the polymeric frontcoat binder. The substantial viscoelastic behavior of the coatings was also linked to their composite structure, and specifically to the ability of the binder to relax the enhanced initial modulus conferred by the presence of the oxide. View full abstract»

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  • Recent publications by IBM authors

    Page(s): 695 - 708
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    The information listed here is supplied by the Institute for Scientific Information and other outside sources. Reprints of the papers may be obtained by writing directly to the first author cited. Information on books may be obtained by writing the publisher. Papers and books are listed alphabetically by author View full abstract»

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  • Recent IBM patents

    Page(s): 709 - 713
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    Freely Available from IEEE

Aims & Scope

The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Clifford A. Pickover
IBM T. J. Watson Research Center