Salme Jussila

Thin polyaniline films in EMI shielding

Abstract Electromagnetic interference shielding efficiency has been measured for highly electrically conducting Polyaniline-Camphor Sulfonic Acid. The polymer is spin coated from m-cresol solution on an electrically insulating substrate as a 1–30 μm thick layer having a conductivity of 10–100 S/cm. The shielding efficiencies (SE) for these electrically thin polyaniline films have been measured in the near-field with a dual-chamber box and in the far-field with a transmission line method in the frequency range 0.1–1000 MHz. The measurements show that SE depends primarily on the surface resistance both in the far-field and the near-field. An additional effect >10 dB is seen when the two layer structure is measured in the near field. By using layer structures, the SE is >40 dB up to ca. 100 MHz in the near-field and 39 dB at 1 GHz in the far-field.

Roll-to-roll method for producing polyaniline patterns on paper

High speed reel-to-reel manufacturing of electrically conductive polyaniline-dodecylbenzenesulfonic acid (PANI-DBSA) patterns directly onto paper substrate were investigated. A printing speed upto 100 meters per minute and line width down to 60 μm with a 60 cm wide paper web with a industrial scale pilot gravure printer was demonstrated. Additional measurements were made with printability tester using the conducting ink which consist of a PANI-DBSA in toluene solution. We illustrate what influence the concentration of the ink, printing speed and pressure at printing nip have on the conductivity of printed patterns.

Lithographic patterning of conductive polyaniline

Abstract Electrically conducting patterns of polyaniline are made by utilizing conventional semiconductor industry process. First polyaniline is spin- or spray-coated on an insulating substrate and has a conductivity of 1–100 S/cm. After that UV resist is spread on top of polyaniline, exposed by UV light, developed and removed. As a result one has a patterned polyaniline layer in insulating and in conducting form on top of the substrate. The conductivity remains essentially unaffected below the resist throughout the process and polyaniline turns insulating at places where the resist is removed. The difference between the electrically conducting part and the electrically insulating part is upto 10 10 . When the linewidth is smaller than 100 μm the square resistance increases slightly, because the deprotonating liquid penetrates somewhat below the resist. Linewidths down to 10 μm have been demonstrated. The process has been utilized in making all-polymer circuit boards having resistors and capacitors made of polyaniline.

Impedance Spectroscopy of the Polymer Thick Film Resistor/Conductor Interface

Impedance spectroscopy has been used to study the electric properties of screen—printed polymer thick film (PTF) resistors over the frequency range 10 Hz — 500 MHz. With a suitable test pattern it was possible to separate the impedance response of the resistor/conductor interface from that of the resistive element itself. This proved to be useful when analysing, whether the manufacturing parameters have more influence on the properties of the interface or the bulk resistor. The main varied manufacturing parameters were curing method, curing temperature and the resistor/conductor interface (pure copper vs. silver treated copper). Furthermore, the test components were kept for 600 hours in a humid environment (85oC / 85% RH), and after this the impedance measurements were repeated. Analysis of the effects of these manufacturing and environmental conditions on the electrical properties of PTF resistors are presented.