The use of static Secondary Ion Mass Spectrometry (SIMS) in the characterization of polymer surfaces and interfaces between polymers and metals is described. Examples are given of the use of SIMS to study the effects of plasma treatments on polyimide surfaces and for the analysis of the interface in metallized polytetrafluoroethylene (PTFE).

Aluminum was deposited on a polyvinyl alcohol film surface by reaction with trimethyl aluminum at 300 K. XPS analysis indicated a carbon free deposition of a monolayer of Al. The Al forms an oxy-carbide complex, AIOC, which exhibits a stoichiometry of 1:1:1 for Al, 0 and C. Within this complex Al is bonded to both C and 0 resulting in the appearance of low binding energy peaks in C(ls) and O(ls) spectra. The complex is oriented such that Al forms the outer-most layer. The Al modified surface was hydrophobic compared to the hydrophilic PVA. A reaction mechanism is proposed based on XPS and mass spectrometric data.

A new method of simulation based on the output of the analytical equilibrium calculation of the Cluster Variational Method (CVM) is used to obtain information about the properties of the polymers adsorbed on a surface. We find a strong preferential adsorption of longer chains, in agreement with experimental observations. This tendency is more pronounced in neutral polymers than in polyelectrolytes. Other geometrical properties like trains, tails, and loops of adsorbed polymers are also calculated.

A semi-dilute polymer solution is one in which polymers overla1p. The bulk properties of semi-dilute polymer solutions have been studied extensively and much has been known. The scaling theory has been very successful. 1,2 The predictions of the scaling theory about various physical quantities as a function of polymer concentration, c, have been confirmed experimentally. 1,3

A system has been developed for studying the dynamic behaviour of gas bubbles in liquid media and is currently being used to investigate the behaviour of a single nitrogen bubble in molten LDPE. It involves the formation of an initial gas-liquid interface from a capillary by direct injection of the gas into the melt, subsequent growth until an equilibrium state is reached and the application of ambient pressure ramps which result in bubble expansion or contraction. The response depends on the rate of change of the ambient pressure. Experiments have been conducted at various temperatures above the crystalline melting temperature, Tm, of LDPE in the range 120°C-150°C. The numerical data acquired are in the form of pressure and temperature values, and these data are superimposed on stored video images of the bubbles for further processing on an image analyser whereby bubble sizes and shapes are determined.

The results obtained reveal the effect of melt viscoelasticity on the dynamics of bubbles in highly viscous fluid media. Furthermore, the changes in bubble shapes with time due to buoyancy effects are also shown. Clearly, the bubble response in the melt is governed by a combination of viscous and elastic effects. However, in the absence of suitable viscous solutions to the problem, we have attributed the behaviour to a time-dependent elastic response, but only as a first order approximation.

In situ Fourier transform infrared (FTIR) reflection-absorption spectroscopy investigations of etching of thin polyimide and poly(methyl methacrylate) films (200-1500Å) in downstream microwave NF3/O2/Ar plasmas are reported. Etch rates and surface chemistry are monitored as a function of gas phase composition, plasma treatment conditions and time. NF3/Ar plasma treatment leads to significant surface fluorination characterized by the formation of aliphatic fluorine compounds (CFx), acyl fluorides, benzoyl fluoride, and polyfluorinated benzene. Addition of oxygen to the etching gas reduces the degree of surface fluorination and modifies the chemical structure. The absorption bands due to CFx structures decrease gradually while polyfluorinated benzene rings and benzoyl fluoride are absent for NF3/O2 mixtures with more than 20% oxygen. The effect of humidity on the plasma-modified polymers is studied by comparing infrared spectra collected in situ with those after air exposure. For NF3/O2 plasma-treated polyimides significant changes are observed while samples fluorinated in NF3 show no changes after exposure to air overnight. The FTIR data are supplemented by XPS analysis.

The morphology of blended polyurethane (PU) sealants was studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The PU was modifided by mechanical mixing with various amounts of Lignin (L) to achieve a homogeneous blend. Specimens were subjected to control (C), accelerated weathering (AW), and natural weathering (NW) conditions. Results obtained from SEM analysis reveal an even distribution of L particles in the PU matrix. Furthermore, the SEM photomicrographs clearly emphasize the differing morphologies of the constituent phases. They also depict the differences in surface texture between control and aged specimens. The DSC analysis shows that the two phases are immiscible which is in agreement with observations by microscopy.

The effect of oxygen plasma treatment on adhesion and surface properties of polypropylene (PP) was assessed. An oxygen rich modified PP layer, immiscible with bulk PP, was formed by the treatment. Contact angle measurements showed that macromolecular motions led with time to rearrangements of the surface layer drastically decreasing its wettability, while its composition, measured by XPS, remained unaffected.

The shear strength of PP-epoxy joints increased after plasma treatment. The locus of failure was found to occur at the PP/epoxy interface for untreated PP, within PP in the case of oxygen-plasma-treated samples, close to the modified PP/bulk PP interface. This result suggests that the plasma treament improves the interaction at the PP/epoxy interface, but weakens the mechanical strength of the surface layer thereby creating a weak point at the modified PP/bulk PP interface.

Polyimides have been considered the most promising organic polymers for use as an inner-layer dielectric or over-metal passivation layer on ICs. These polymers have certain processing advantages over traditional inorganic dielectrics such as SiO2 or Si3N4. However, polyimide (PI) must meet the stringent standards that inorganic materials have met, including good adhesion to the substrate and resistance to diffusion of water. Failure to meet these standards may result in increased aluminum corrosion rate and consequent degraded reliability.

In this study, the corrosion rate of sputtered aluminum test patterns passivated with either PI or plasma-deposited silicon nitride (SiN) was measured at 85°C and 85% relative humidity (RH). The objectives of this work were to: (1) assess the failure rates of biased aluminum interconnection with PI or SiN passivation; (2) determine the failure mechanisms in each case; and (3), as a result, evaluate the suitability of PI passivation for high voltage ICs in non-hermetic packages. In this report, the test device fabrication and evaluation procedures are first described. Then the results are presented, including both the failure rate measurements and the failure analyses. Finally, the results are compared and discussed.

Polyimides are attractive candidates for advanced electronic and space applications due to their high performance thermal and mechanical properties. However, the typical intractability and insolubility of polyimides has been a disadvantage. Utilization of the soluble intermediate amic acid can, to some extent, circumvent this problem. However, drawbacks to this approach include the hydrolytic instability of the amic acid and the liberation of water during its subsequent thermal cyclization. Residual stress build-up at the imide-substrate interface may occur due to swelling and drying cycles caused by the loss of water and solvent. In addition, the liberation of volatiles from a polyimide adhesive or coating can lead to the creation of voids which may significantly detract from mechanical properties. Polymeric adhesives must flow in order to provide good wetting of adherend surfaces and consolidation of the bond components. Thus, fully imidized, melt and solution processable, high Tg aromatic polyimides are of great interest.

Ultra-high molecular weight polyethylene fibers possess exceptional strength and stiffness combined with low density. Their use as reinforcements in polymer matrix composites has, however, been limited by poor fiber adhesion. In the present study, individual fibers of UHMW-PE (Allied-Signal SPECTRA-1000) were modified by direct implantation of N+, Ti+ and Ar+ ions, at energies between 30 and 100 KeV, to doses ranging between 1x1014 and lx1015 ions/cm2. Fiber tensile strength was generally unaffected by these irradiations. Single-fiber droplet pull-off tests using DGEBA Epoxy with m-PDA curing agent have shown that ion beam surface modification of the fibers can give an increase of over 300% in interfacial shear strength (ISS). The improvements were found to vary with dose but were relatively insensitive to implant species. TEM observation of transverse microtomed sections confirmed a substantial improvement in fiber-matrix adhesion for ion beam modified UHMW-PE composites.

Ion implantation in silicone rubber has been carried out in order to study its effects on structure and chemical states. H+-, He+-, C+-, N+-, N2+-, O+-, O2+-, Ne+-, Na+-, Ar+-, and K+- ion implantations were performed at an energy of 150 keV with doses ranging from 1×1013 to 1×1017 ions/cm2 at room temperature. The depth profiles of the ion implanted elements and host elements were investigated by means of XPS and SIMS. The chemical properties were studied by FT-IR-ATR and Raman spectroscopy. XPS results indicated that most of the implanted elements showed a Gaussian like distribution in the silicone polymer matrix, but implanted He+, Ne+, and Ar+ could not be detected. Results of FT-IR-ATR showed that ion implantation broke CH3 and Si-O bonds to form new radicals such as SiOH, >C=0, CH2 and SiHx and the effects varied depending on the implanted ion species. The Raman spectroscopy results showed that ion implanted silicone contained both sp3 and sp2 bonded carbon.

Amorphous metal foil-wound inductors have been tested as ferromagnetic saturable inductive elements for pulsed-power (multi-terawatt) switching modules in the inertial confinement fusion program at Sandia National Laboratories. Saturation switching may provide large 100 ns current bursts necessary to accelerate ion beams for the fusion fuel pellet implosion required, for example, in PBFA (particle beam fusion accelerator) operation.

In simulated capacitor testing premature dielectric breakdown of thin polyethylene terephthalate film insulation in the inductor windings occurs at considerably below 2500 V. This appears to be due to inadvertant dielectric damage from micro-spikes on the amorphous foil surface. Electron micrographs and dielectric breakdown data illustrate that electrophoretically-applied dielectric coatings, deposited from organic aqueous colloid dispersions, can be used to provide insulating coatings on the foil which provide a 240% improvement (6000 V) in the breakdown strength of wound amorphous foil inductors.

The theory and operation of a dedicated electrophoretic continuous coating system is described. The machine was constructed and successfully applied for dielectric coating of amorphous metal foil. Additional possible applications exist for practical dielectric coating of metallic films or foils used in various commercial wound-type capacitor structures.

Interdiffusion at interfaces between deuterated polyamic acid (d-PAA) and polyimide (PI) films was investigated with forward recoil spectrometry, an ion beam analysis technique. The PI films were prepared by spin - coating a solution of PAA on a silicon substrate, followed by an anneal at a temperature Ti, which produced partial or complete conversion of the PAA to PI. An overlayer of d-PAA was added in one set of samples by spin - coating from solution and in another set by transferring (in the absence of solvents) a dry d-PAA film onto the PI surface. The bilayer samples were then either annealed at a temperature Td or allowed to stand at room temperature. Bilayers prepared by spin - coating d-PAA from solution directly on partially cured PI films had interdiffusion distances w that decreased with increasing values of Ti to immeasurable levels by Ti = 200 °C. The decrease in w with increasing Ti is thought to be caused by a positive Flory parameter between PAA and PI which increases with the imide fraction in the PI film; the result is an increasing immiscibility between the swollen polymer layers. No interdiffusion occurred in the solventless - transfer samples for any combination of temperatures Ti or Td from room temperature up to 400 °C. Post - annealing of spin - coated bilayers at a temperature Td up to 400 °C was ineffective in producing any additional interdiffusion. Both of these results indicate that thermally activated interdiffusion (even for initially unimidized samples) does not exist in the absence of solvents, an effect attributed to the rapid increase of the glass transition temperature of the polymer with imidization.

This paper reviews the principles and describes new procedures for determining the bond strength of a metal film on a substrate. Considered are mechanical, electrical, acoustical and thermal measurements. Particular attention is placed on techniques which permit an unambiguous connection to be made between measured quantitites and the parameters by which the adhesive strength of a coating on a substrate can be determined.

Film adhesion, which is an important reliability factor in many microelectronic structures, is usually evaluated by peel testing. The loading and the peel angle in peel tests can be controlled best if these tests are “automatized”, which could be done, for instance, by applying air pressure to a film through an opening in the substrate. We consider a rectangular opening and determine, how this pressure is related to the peel (membrane) loading and peel angle for the given film material and thickness. Our study is based on von-Kármán's equations for large deflections of plates. The obtained results provide mechanical fundamentals for a rational physical design of a peel test vehicle.

Monomolecular assemblies of n-perfluorocarboxylic acids [CF3 (CF2)nnCOOH,n=-6,7, and 8] have been adsorbed at silver by spontaneous adsorption from dilute alcoholic solutions. Infrared reflection spectroscopy indicates that the monolayers form by the reactive chemisorption of the carboxylic acid to a carboxylate salt. Ellipsometrically-determined film thicknesses increase linearly with an increase in the perfluorocarbon chain length. Contact angle measurements indicate that the packing density of the films increases with increasing chain length, resulting in an interface with a low surface free energy. The structure and properties of these interfaces are compared to those for monolayers of n-alkanoic acids. The potential utility of such assemblies to probe fundamental chemical and physical interactions at polymer-metal interfaces are also discussed.

The paper presents a study of three polyimide-oxide interfaces. The Cr-oxide-PI interface seems to undergo a drastic topographical structural rearrangement. The case of the Ni surface is indicative of heavy decomposition of the Ni oxide which induces the decomposition of the polymer film. On the contrary the stabilized Ni surface behaves in a normal manner indicating that the driving force for the decomposition is the instability of the oxide.

An enhancement of the adhesion between copper and polytetrafluoroethylene (PTFE) has been studied. Thin-films of copper were electron-beam deposited on the surface of the polymer substrates. Peel test measurements showed that, without any treatment of the substrates, the adhesion was poor with a peel strength of 1-2 g/mm. A pronounced enhancement of the adhesion has been obtained when the fluorocarbon substrates were treated by either an ultraviolet (UV) irradiation, an ion-beam presputtering prior to the metal deposition, or heat treatments after the deposition. Among the treatments employed, the ion-beam sputtering was the most effective in improving the adhesion. The roles of the treatments and possible reasons for the enhanced adhesion are discussed in conjunction with the studies of interface morphology and chemistry using Scanning Electron Microscopy, Rutherford Backscattering Spectroscopy, and X-ray Photoelectron Spectroscopy.