This paper addresses some of the problems encountered in propagating high-speed signals on lossy transmission lines encountered in highperformance computers. A technique is described for including frequency-dependent losses, such as skin effect and dielectric dispersion, in transmission line analyses. The disjoint group of available tools is brought together, and their relevance to the propagation of high-speed pulses in digital circuit applications is explained. Guidelines are given for different interconnection technologies to indicate where the onset of severe dispersion takes place. Experimental structures have been built and tested, and this paper reports on their electrical performance and demonstrates the agreement between measured data and waveforms derived from analysis. The paper

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SYNOPSISTo enhance polyimide-to-polyimide adhesion, we have investigated the effect of surface modification in water vapor plasma. The use of a water vapor plasma to treat a fully cured polyimide ( PMDA-ODA) surface before subsequent layers of polyimide are applied results in dramatically enhanced interfacial adhesion. The polyimide-to-polyimide interfacial adhesion strength attained following water vapor plasma treatment exceeds the cohesive strength of the applied polyimide layer. The effect of surface modification in water vapor plasma on metal-to-polyimide adhesion has also been investigated. The use of a water vapor plasma to treat a fully cured polyimide (PMDA-ODA) surface prior to metallization results in increased metal-to-polymer interfacial adhesion. A study of both electroless and vacuum-deposited metal was conducted. The use of contact-angle measurements, peel tests, Fourier transform infrared spectroscopy, optical emission spectroscopy, nuclear forward scattering, and X-ray photoelectron spectroscopy has led us to a preliminary understanding of the resulting surface modification and the subsequent effect of adhesion promotion.

The role of oxygen in affecting the adhesive bonding at the metal/polyimide (polyimide-on-metal) interface has been studied. Both pyromellitic dianhydride (PMDA) -oxydianiline (ODA) and biphenyl-tetracarboxylic dianhydride(BPDA) -p-phenylene diamine (PDA) based poly(amic acid) precursors were cast and fully imidized on metal surfaces of Cr, Cu, Ni, Co, Cu/Ni, and Cu/Co in a nitrogen atmosphere. The peel strengths at the polyimide-on-metal interface were measured, using a 90° peel test, immediately after curing, and then remeasured after annealing in either nitrogen (N2−≤100 ppm O2 ) or air (N2 –21% O2 ) at 350 °C for 1 h. Very little or no change in peel strength was measured after these samples were annealed in nitrogen, while significant adhesion degradations were measured on all metals after annealing in air. The loss of polyimide (PI) adhesion to the Cu or Co surface is attributed to metal catalyzed thermal–oxidative degradation of the PI at the metal/PI interface, as characterized by polyimide thickness reduction, Fourier transform infrared and x-ray photoelectron spectrometries. The rate of degradation of the PMDA-ODA films on Cu or Co is several times faster than that of the BPDA-PDA films. The degradation products were characterized as CO2, CO, Cu carboxylate salts and a nitrile moiety entrapped in partially degraded PI films. The extent of degradation was found to increase with increasing oxygen content in the annealing ambient or with decreasing PI thickness, indicating that oxygen diffusion through the PI overcoating to the metal/PI interface plays a critical role in promoting degradation. On the Cr and Ni surfaces, such metal catalyzed degradation was not detected with our techniques, while some adhesion strength was still retained, a significant loss in adhesion strength was observed. This is probably due to oxidation of the metal underlayer causing debonding at the originally well adhered metal/PI interface. When all testing variables were held constant, the peel strength of a well adhered metal/PI joint is shown to increase with increasing peeling rate (crosshead speed). An increase of up to ∼40% in peel strength was measured when the crosshead speed was increased from a low speed of 0.05 mm/min to 10 mm/min. The locus of fracture of the as-cured films was cohesive, i.e., the fractured surface was located within PI, while for the thermal–oxidative degraded joint the failure mode was changed to adhesive.