Metallized Polyimide Films Research Articles

Metallized polyimide films for biomedical applications: X‐ray photoelectron spectroscopy, surface tension, and blood compatibility studies

AbstractThe implications of nitrogen plasma exposure of a semi‐aromatic polyimide (PI) and a fully aromatic one, was studied in regard to gold adhesion for biomedical purposes. The hydrophobicity of the analyzed PI films, estimated by the contact angle method, was influenced by both plasma treatment and gold sputtering. Comparative evaluation of the chemical binding states and surface chemical composition was determined by X‐ray photoelectron spectroscopy (XPS) for pristine, plasma treated, and metallized PI films. The appearance of the polar functional groups upon plasma exposure facilitates binding of the gold on the PI surface. Hemocompatibility was theoretically evaluated based on surface tension data. The observed characteristics of the metallized samples could be useful for making components for blood contacting devices, such as blood pressure or blood glucose detection.

Электронмен сәулелендірудің және күміспен қаптау процестерінің полиимидті үлдірлердің деформациялануына әсері

The effect of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films is studied. The metal layer of the polyimide base impregnated into the structure was from 1 to 5 µm thick. The coatings on the surface contained 80÷97 % of the relative silver mirror in the visible and infrared regions. The irradiation was carried out on a linear accelerator ELU-6 with an average electron beam energy of 2 MeV, an integral current of up to 1000 µa with a pulse frequency of 200 Hz and a pulse duration of 5 µs. The absorbed dose by the samples was: 10, 20, 30 and 40 MGy. Deformation of the samples was performed at room temperature in the uniaxial tension mode on the universal testing machine Instron 5982. Study of Structural changes in composite materials in the result of the impact of these physical factors was studied in the x-ray diffractometer type DRON–2M in air at 293 K, CuKa radiation (laCu=1.5418 A). A significant increase in the mechanical characteristics as a result of metallization of films compared to the pure film, so the increase in the tensile strength by ∆σ=105 MPa and plasticity by ∆e=75%, which is associated with the peculiarities of changes in the structure of metallized films and the conditions of their chemical etching. Electronic irradiation of the metallized polyimide film worsens its elastic and strength parameters, which is caused by the formation of new phases in the coating in the form of silver oxide, the concentration of which increases with increasing dose, and is also caused by a violation of the ordered structure of the material in the form of a rupture of the macromolecules of polyimide and the formation of new phases of silver in the coating. The mathematical model, which is in good agreement with the experimental data and allows to predict the elastic properties of silver metallized polyimide films, is obtained.

Impact of silver metallization and electron irradiation on the mechanical deformation of polyimide films

The impact of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films has been studied. The metal that impregnated the structure of the polyimide substrate was 1–5 μm. The surface coatings contained 80–97% of the relative silver mirror in the visible and infrared regions. Irradiation was performed at the ELU-6 linear accelerator with an average beam electron energy of 2 MeV, an integral current of up to 1000 μA, a pulse repetition rate of 200 Hz, and a pulse duration of 5 μs. The absorbed dose in the samples was 10, 20, 30, and 40 MGy. The samples were deformed at room temperature under uniaxial tension on an Instron 5982 universal testing system. The structural changes in the composite materials that result from the impact of the physical factors were studied using an X-ray diffractometer DRON-2M in air at 293 K using CuKα radiation (λαCu = 1.5418 A). A substantial growth of mechanical characteristics resulting from the film metallization, as compared to the pure film, was observed. The growth of the ultimate strength by Δσ = 105 MPa and the plasticity by Δe = 75% is connected with the characteristics of the change of structure of the metallized films and the chemical etching conditions. The electron irradiation of the metallized polyimide film worsens its elastic and strength characteristics due to the formation of new phases in the form of silver oxide in the coating. The concentration of these phases increased with increasing dose, which was also the result of the violation of the ordered material structure, namely, the rupture of polyimide macromolecule bonds and the formation of new phases of silver in the coating. A mathematical model was obtained that predicts the elastic properties of silver metallized polyimide films. This model agrees with the experimental data.

Electric and Optical Properties of Polyimide Surface Films Modified by Metals

<p>Electric and optical properties of polymer films, which were prepared on the basis of polyimides and metallized by binary aggregates Ag with Ni and Co, have been investigated. The metallized polyimide films with additional coating from Ni, Au and Rh have been studied too. It has been found that the temperature dependence of the specific surface resistance in the metallized films at the temperature from 25 up to 160 <sup>o</sup>C was in the well agreement with linear law. The specific surface resistance at 20 <sup>o</sup>C and temperature coefficient showed low values and was 0.16-2.24 Ω and 0.69×10<sup>-4</sup>-19.18×10<sup>-4</sup> K<sup>-1</sup> respectively. The film reflection coefficient in visible spectrum field at wavelength of 530 nm was 75% and essentially enlarged with wavelength increasing.</p>

Synthesis of New Metallized Polyimide Films with High Optical and Physical Performances

Electroconductive and reflective metallized polyimide films have been prepared by heterogeneous chemical modification of polyimide surface. By carrying out the chemical reactions in situ in the modified layers of polyimide surface, a metal phase strongly impregnated into the polyimide surface is obtained. The steps of chemical modification have been studied on the model compound – poly(amic acid) on the basis of isophthaloylchloride and methylenedianthranilic acid which forms insoluble sodium or potassium poly(amicacid) salts (polyamate). Metallization of Kapton HN & JP (from DuPont) and Upilex S (from Ube) films<br />has been carried out and the films have been characterized by X-ray diffraction (XRD), X-ray fine diffraction (XRFD), measurements of reflectivity in the visible range and surface resistivity at elevated temperatures. It is shown that reflectivity coefficients of silvered films are 90-92% and surface resistivity is about 0.5 Ω/sq.

Effect of Modification on Electrochemical Chelation of Polyimide Films

Novel procedure of electrochemical chelation of polyimide films was developed. The kinetics of silver cation sorptions into the films during the chelation was found out. The effect of modification treatment of film surfaces on kinetics of electrochemical process was studied. The stabilization of ion-sorbed layer of films occurs in water-isopropanol solvents. Sorption of silver during electrochemical deposition is 0.75-1.5 mg per 100 μm of polyimide depending on modification solution. Thus, the most appropriate morphological modification with about 1.5 mg/100 μm take places in heterocyclic solvents. The resulting metallized polyimide films show good non-washing out adhesion of metal into gel-like structured surfacial layers of the film.

New Reflectable Materials on the Basis of Polyimides

Electroconductive and reflective metallized polyimide films have been prepared by heterogeneous chemical modification of polyimide surface. By carrying out the chemical reactions <em>in situ</em> in the modified layers of polyimide surface, thereby a metal phase strongly impregnated into the polyimide surface is obtained. The steps of chemical modification have been studied on the model compound – poly(amic acid) on the basis of pyromellite dianhydride and oxydianiline, which forms insoluble sodium or potassium poly(amicacid) salts (polyamate). Metallization of Kapton HN & JP (from DuPont) and Upilex S films have been carried out and the films have been characterized by XRD, XRFD, and measurements of reflectivity in the visible range and surface resistivity at elevated temperatures. It is shown that reflectivity coefficients of silvered films are 90-92% and surface resistivity is about 0.5 Ω.

Highly Reflective and Conductive Double-Surface-Silvered Polyimide Films Prepared from Silver Fluoride and BTDA/4,4‘-ODA

This work focuses on surface silver metallization on a 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxydianiline (BTDA/ODA)-based polyimide matrix via a direct ion-exchange self-metallization technique using a simple silver salt, silver fluoride, as the silver precursor. The method involves performing an ion-exchange reaction of damp-dry poly(amic acid) films in silver aqueous solution to form silver(I)-containing precursor films. Thermal treatment under tension converts the poly(amic acid) into polyimide and simultaneously reduces the silver(I) to silver(0), yielding silver layers with excellent reflectivity and conductivity on both film sides. However, significant property differences were exhibited on the upside and underside surfaces of the metallized films and this has been discussed in detail. The variation of surface properties and surface morphologies during the thermal curing cycle was also investigated. The mechanical and thermal properties of the metallized polyimide films are essentially similar to those of the host polyimide.

Metallized polyimide films: Metallization and mechanism of the process

The formation of metallized polyimide films in situ, namely, the alkaline hydrolysis of film surfaces, chelation of the modified surface with metal ions, and their chemical reduction giving rise to a metal layer, has been investigated. Initial polyimide films are cast from reaction solutions on a glass substrate. The solutions are prepared through the polycondensation of dianhydride of tricyclo[4.2.2.02.5dec-7-ene-3,4,9,10-tetracarboxylic acid and 4,41-diaminodiphenyl oxide in N-methyl-2-pyrrolidone at 160°C. It has been shown that alkaline water-alcohol solutions are optimal media for the hydrolysis of the film surface. The maximal exchange of alkali metal ions is achieved through formation of a more stable metal-ligand complex of poly(amido acid), with the chelation rate depending on the nature of a metal. The metal reduction proceeds rapidly; however, the mechanism of this process depends on the pH of a medium. The annealing of metallized films results in the imidization of poly(amido acid) and in the growth of metal grains on the material surface to yield a metal layer with good optical properties and high conductivity.

Double-Surface-Silvered Polyimide Films Prepared via a Direct Ion-Exchange Self-Metallization Process

Silver metallized polyimide films have been fabricated with excellent reflectivity and conductivity on both sides via a direct ion-exchange self-metallization technique utilizing 3,3‘,4,4‘-benzophenonetetracarboxylic acid dianhydride/4,4‘-oxidianiline (BTDA/4,4‘-ODA)-based poly(amic acid) (PAA) films as the polyimide precursor and aqueous silver nitrate (AgNO3) solution as the silver origin. Silver polyamate was formed during the ion-exchange process. Heat treatment of the silver(I)-containing precursor films effects the cyclization of PAA and the simultaneous reduction of silver(I), giving silvered polyimide films. Surface reflectivity and conductivity were developed as a function of cure time and temperature and they were greatly associated with the variation of surface morphology. Property differences were exhibited on the upside and underside of the composite films. The final metallized BTDA/4,4‘-ODA polyimide films maintained the essential mechanical and thermal stability of the pristine polyimide films. Films were characterized by FTIR-ATR, ICP, DSC, CA, XPS, XRD, and SEM, as well as reflectivity and conductivity measurements.

Preparation of highly reflective and conductive metallized polyimide films through surface modification: processing, morphology and properties

Silvered polyimide films have been prepared by potassium hydroxide hydroxylation of polyimide film surfaces and incorporation of silver ions through subsequent ion exchange. Thermal curing not only recycloimidized the poly(amic acid) into polyimide, but also reduced silver ions into silver atoms and near-atomic silver clusters, which diffused and aggregated to give reflective and conductive surfaces without need of the addition of reducing agents. Films were characterized by X-ray photoelectron spectrometer, transmission electron microscopy, scanning electron microscopy and tapping mode atomic force microscopy. The thickness of the silvered layers and the reflectivity and conductivity of the silvered films can be controlled. By this method, the double-sided silvered polyimide films with excellent reflective (reflectivity > 97%) and conductive surfaces (surface resistivity = 0.02 Ω cm−2) could be easily fabricated. Their essential mechanical properties could be maintained, and the silver–polymer adhesion was outstanding.

Optical scanner using a MEMS actuator

Abstract Optical scanners have numerous applications from bar code readers and laser printers in industry to corneal resurfacing and optical coherence tomography in medicine. We have developed an optical scanner fabricated using photolithography on a polyimide substrate. This scanner uses an electrostatic microelectromechanical system (MEMS) actuator to tilt a gold-coated mirror resting on 3 μm thick polyimide torsion hinges to steer an optical beam. The linear actuator used is the integrated force array (IFA), a network of hundreds of thousands of deformable capacitors, which electrostatically contract with an applied differential voltage. IFAs are 2.2 μm thick patterned, metallized polyimide films 1 cm long and either 1 or 3 mm wide depending on the application. The mirror support structures were modeled using one-dimensional beam theory and ANSYS finite element analysis and then fabricated using a three-layer process with polyimide and gold on silicon wafers. Side scanning structures have been fabricated with tables 1.125 or 2.25 mm wide. The completed devices were coated with a 500 A thick conformal coating of parylene for protection from the environment. These devices have demonstrated optical scan angles up to 146° for applied voltages up to ±50 V. These devices were also used to steer a laser beam in a prototype bar code reader to demonstrate functionality.

Study of thermal properties of electron irradiated metallized polyimide films

The paper presents the results of experiments on the temperature dependence of thermal conductivity and heat capacity of some metallized polyimide films irradiated with electrons of energy 2–6 MeV. Accelerator ALU-6 was used to irradiate films with different integral doses (0–2×10 −3 Gy). A cascade-probability model of generation of radiation defects in polymers (break of polymer chains) was developed. Such defects act directly on the process of heat transport and heat capacity.

Control of Reflectivity and Surface Conductivity in Metallized Polyimide Films Prepared via in Situ Silver(I) Reduction

Optically reflective and surface-conductive polyimide films have been prepared by the incorporation of silver(I) acetate and trifluoroacetylacetone into a dimethylacetamide solution of the poly(ami...

Absorption and interaction of methylene chloride with metallized polyimide films

Metallized polyimide films are commonly used for the fabrication of flexible circuits for tape automated bonding (TAB) applications. Although there has been an extensive effort to understand the formation of the metal/polyimide interface, little information exists on the effects of humidity and temperature on adhesion. Further, since circuit fabrication processes involve a variety of chemicals, these materials can potentially induce adhesion degradation. Methylene chloride (MC), used for photoresist stripping, absorbs readily into Kapton-H. Residual MC levels in the polymer undergo decomposition upon heating above 100 °C to yield HCl. Optical microscopy, Rutherford backscattering spectroscopy and Auger electron spectroscopy are used to characterize the resulting interfaces on actual TAB circuit lines before and after exposures to humid and thermal environments. Thin metallized Kapton-H films were exposed to MC followed by a thermal cycle to determine the role of chloride on adhesion degradation. After a thermal cycle or additional temperature/humidity exposure, the fracture mode shifts from cohesive in the polyimide to the chromium/copper interface. This results in adhesion loss with concentration of chloride at the weaker interface.