Polyimide films, analyses

A representative sample of many of the polyimide films that were produced were subjected to thermo-mechanical analysis (TMA), torsional braid analysis (TBA), thermal gravimetric analysis (TGA), infrared spectral analysis and weight loss on prolonged heating (e.g. isothermal studies), TABLE II. The softening temperature as measured by TMA and TBA are in general... 

Figure 2. Differential scanning calorimetric analysis of a cobalt chloride modified BDSDA-ODA polyimide film.

Figure 3. Comparison of differential scanning calorimetric data (parts A and B) with thermomechanical analysis data (part C) for a cobalt chloride modified BTDA-ODA polyimide film.

The tangent of the capacitance phase angle has been shown to be a measure of the completeness of the anneal (2.) Based on this technique, we have data which would predict 30 minutes at 300°C is sufficient to obtain optimum dielectric properties. However, we have found chronogravimetric analysis of polyimide films to be more useful in defining optimum anneal conditions. 

There are several difficulties in the application of this technique to the analysis of sodium barrier properties of these polyimide films. First, as we have seen above, large shifts in the surface potential characteristics of MPOS structures can be associated with electronic conduction in the polyimide and charging of the polyimide-oxide interface. These shifts are not readily separable from any that might be caused by the inward drift of sodium ions. Second, the effect of the electronic charging process is to buck out the electric field in the polyimide which is needed to drive the ion drift mechanism. As seen in Figure 6, the electric field is reduced to very small values in a matter of minutes or less, particularly at the higher temperatures where ion drift would normally be measured. 

X-ray powder diffraction was recorded using a conventional x-ray powder diffractometer with Cu-Ka radiation. Polyimide film on which sample particles are deposited is glued on a glass sample holder with vacuum grease. Figure 1.6.9 shows the recorded diffraction pattern. An analysis of the pattern is made by comparing the lattice parameters and diffraction intensities of the particles and those of known iron compounds, and shows that the particles are Fe304. 

PMDA-ODA on Al 0,. A minor improvement is noticed in the peel force of PMDA-ODA on Al20, when APS is applied to the surface. From the surface analysis results one can see that the APS was not retained on the IPA cleaned sapphire surface to any detectable level, which is likely the cause for no significant improvement in the peel force. The minor improvement in the results may have to do with a possible surface cleaning effect of the sapphire surface with APS solution. The data in Table 3 show that the failure locus has not changed significantly by the APS or T H exposure, being essentially in the polyimide film close to the polyimide/ceramic interface. 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

In this study, plasma fluorinated polyimide films of various thicknesses were exposed to a 2 MeV He2+ ion beam at different doses to determine beam effects. A thick PTFE film, irradiated under similar conditions, was also examined surface changes and fluorine loss during RBS analysis were compared. 

For a number of years, polymers such as polyimide, have been subjected to widespread research, because of their increasing importance as dielectric materials for the fabrication of microelectronic devices (1). In particular, the adhesion of metal or polyimide films deposited on polyimide substrates and vice versa, is of considerable importance in most applications, and many studies ranging from adhesion testing to detailed spectroscopic analysis of interfaces have been reported previously (2,3.. 5.6). 

The experimental procedures and x-ray photoemission results for the preparation of ultrathin (d = 1.1 nm) polyimide films on polycrystalline silver by co-condensation of PMDA and ODA are described elsewhere [5]. In that work our XPS results suggested that the polyimide chains bond to the silver surface via a carboxylate type bonding. This conclusion was derived from an analysis of the results obtained for the interaction of the monomers (PMDA and ODA) and of the resulting ultra-thin polyimide film. Due to the relatively larger thickness of the polyamic acid films as compared to the monomer adsorbate phases and the polyimide film, no conclusions were possible about the reaction of the polyamic acid with the silver substrate. 

This paper describes a process for activating polyimide surfaces for electroless metal plating. A thin surface region of a polyimide film can be electro-chemically reduced when contacted with certain reducing agent solutions. The electroactivity of polyimides is used to mediate electron transfer for depositing catalytic metal (e.g., Pd, Pt, Ni, Cu) seeds onto the polymer surface. The proposed metal deposition mechanism presented is based on results obtained from cyclic voltammetric, UV-visible, and Rutherford backscattering analysis of reduced and metallized polyimide films. This process allows blanket and full-additive metallization of polymeric materials for electronic device fabrication. 

TABLE II TYPICAL ANALYSIS DATA FOR ULTRAPURE POLYIMIDE FILMS PROPERTY TYPICAL DATA... 

Glass transition temperature of polyimide film dried through 200°C for one hour, thermal mechanical analysis at heating rate of 5°C/min. 

Auger electron spectroscopy with depth profiling via argon ion etching (position and thickness of near-surface layer), transmission electron microscopy of ultramicrotomed cross-sections (physical internal structure), elemental analysis (extent of metal salt conversion), and surface electrical resistivity versus temperature profiles (continuity of near-surface layer). The data from these techniques were used cooperatively to develop a model for these microcomposite polyimide films. The model represents the sample as three distinct regions. Fig. 1. The bulk of the film contains either converted (e.g. Ag) or nonconverted (e.g. C0CI2) additive in a predominately polyimide environment. An oxide-rich (e.g. 0 ) or metal-rich layer (e.g. Ag, Au) interspersed with polyimide accounts for the second region. 

Xu and Coleman studied 6FDA (2,2 -bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride)-pMDA (pyromellitic dianhydride) polyimide films irradiated by an ion beam [84]. A beam of 140 keV N ions with a low-current density was used, and three irradiation fluences (2 x 10 cm , 1 x 10 cm , and 5 x 10 cm ) were chosen. It was reported that even a small dose altered the microstructure of the surface layer. The AFM analysis of those films showed that low-fluence irradiation induced microvoids in the surface layer of the polymer, and high-fluence irradiation resulted... 

ESCA was found to be useful in studying the effects of different methods of curing, the adhesion promoter and the deposition of copper on polyamic acid-polyimide surfaces. The results show different C Is spectral features for hot plate vs. oven cured films but identical stoichiometries. The silane treated amic acid surface showed an additional N Is component at 402.0 eV due to NH . Heat treatment of this film resulted in the formation of a silicon-polyimide. Grazing angle ESCA results showed that the silane diffused into the sub-surface of the amic-acid film. Analysis of cured polyimide films after the etch (FeCl ) removal of a... 

Fig. 25. (a) Desmeared SAXS curves of PAA and PMDA-ODA polyimide films cured off substrate under different eonditions (1) 90°C/3.5 h + 150°C/8 h + 190°C/4 h + 240°C/5.5 h stepwise (2) 250°C/12 h (3) 350°C/12 h and (4) 430°C/2 h. (b) Schematic diagram of a possible layered morphology based on one-dimensional model analysis. Reprodueed with permission from J Polymer Sci, Polym Phys Ed 1981 19 1293. 1981 John Wiley Sons [72]. (c) Smeared SAXS eurves of PMDA-ODA polyimide films cured off substrate under different temperatures. Reproduced with permission from J Polymer Sci, Polym Phys Ed 1984 22 1105. 1984 John Wiley Sons [73]. 

EDX of polyimide film does not show any sUicium peak - Figure 21 (a) but this peak is present in the analysis of the polyimide with siUca-gel microcapsules. 

The symmetry of the configuration depicted in Figure 4.25 with a circular delamination zone renders the analysis of delamination simple and transparent. If this symmetry is lost, the situation becomes more complex and the delamination zone shapes which can be observed are surprisingly rich in detail. For example, Choi and Kim (1992) introduced a cut into a polyimide film on a glass substrate and observed the resulting growth of a delamination front from the cut. Because the local conditions varied along... 

DABP and pyromellitic dianhydride (PMDA). Scanning electron microscopy was used to observe the titanium alloy surfaces after various pretreatments and the surfaces of fractured joints. ESCA spectra were obtained for the cleaned alloy surface and for fracture surfaces. The intensity of the titanium peak in the ESCA spectra was related to the presence of thin polyimide films. Specular reflectance infrared spectroscopy was also used in the analysis of the fracture surfaces. 

The polymer-metal interface shown in Fig. was derived from an electron micrograph obtained by Mazur and Reich.They electrodeposited silver from a silver ion solution diffusing through a polyimide film. Particles not connected to the diffusion source were removed by computer analysis. The deposited silver particles essentially "decorate the concentration profile and permit the diffusion front to be observed. A 1000-A thin slice was used to aproximate two dimensional diffusion. The fractal dimension of this interface was determined by computer analysis to be approximately 1.7. Similar ramified interface fronts are created by vapor deposition of metal atoms on polymers and by certain ion bombardment treatments of polymer surfaces. The fractal front is fairly insensitive to the details of the concentration profile. However, strong chemical potential gradients in asymmetric interfaces may promote a more planar, less ramified structure. The fractal characteristics of polymer interfaces... 

Figure 29 Determination of thermal expansion coefficients and glass transition temperatures by thermomechanical analysis of conductive adhesives (a) IP 680 silver-filled polyimide analyzed with a dilatation probe (Tg 230°C) (b) self-standing polyimide film studied with an extension probe (Tg 350°C).

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