B.J. Ramsey

Capacitive-type humidity sensors fabricated using the offset lithographic printing process

This paper reports on the fabrication of a novel capacitive-type relative humidity sensor of which the electrode films are deposited using the high speed printing process, offset lithography. Parallel-plate capacitor sensor structures have been formed with a number of humidity sensitive polymers including polyimide and polyethersulphone (PES). Details of the fabrication process and sensor characteristics such as linearity, sensitivity and response time are included.

A NOVEL CIRCUIT FABRICATION TECHNIQUE USING OFFSET LITHOGRAPHY

This paper reports the progress in the development of a novel fabrication technique for thin-film electronic circuit boards. The application of this work is in substitutes for resin-laminate circuit boards fabricated by photo-resist and etching processes. Circuit tracks are formed on paper-like substrates by depositing films of a metal-loaded ink via a standard lithographic printing process. Whilst developed primarily for low cost applications, Conductive Lithographic Films (CLFs) have now been successfully demonstrated in a range of telephone plant, microprocessor and microwave stripline applications.

Lithographic film circuits – a review

Conductive lithographic films (CLF) are an emerging fabrication process for electronic interconnect and a range of passive component structures. This paper reviews the manufacture, properties and applications of CLF conductors, and discusses other lithographically deposited electronic materials including resistive, dielectric and ferrite films. Recent developments in CLF technology, including multilayer structures and concurrent printing of interconnect with printed passive components, are presented.

INTERDIGITATED CAPACITORS BY OFFSET LITHOGRAPHY

This paper reports on an initial investigation into interdigitated capacitors manufactured via the offset lithographic printing process. Results taken from print-trials reveal the relationship between electrode geometry and capacitance. The paper also identifies a relationship between the substrate characteristics and the behaviour of the capacitive structures. This work is in support of a low cost and low environmental impact approach to circuit board manufacture.

A novel manufacturing process for capacitors using offset lithography

A novel fabrication technique for passive electronic components and circuit interconnects based on offset lithographic printing is described. The application of this work is in low cost and low environmental impact substitutes for resin-laminate circuit boards populated with discrete components. Multilayer ceramic capacitor elements are formed on flexible substrates by depositing layers of metal and ceramic-loaded inks sequentially via a standard lithographic printing press.

Printed thermocouple devices

A novel process for the fabrication of thermocouples using thick-film techniques has been developed. Thermoelectric reactions of 22 /spl mu/V//spl deg/C per couple have been observed which are comparable to those of conventional thermocouples. The paper outlines the potential for a rapid, low-cost, low temperature manufacturing solution for the production of electrical temperature sensors.

Post-processing of conductive lithographic films for multilayer device fabrication

Cheap, flexible conductive interconnects have the potential for application to a wide variety of device structures. Conductive lithography is a very fast single-stage printing process for flexible electrical interconnects. For the more challenging exploitation areas in multilayer devices, such as displays, it was found that the existing films could not be employed in their current form and three parameters were identified as critical to device fabrication. Two distinct methods of post-processing have been investigated, calendering and electroless plating, to improve properties. Both methods aimed to modify the surface roughness and conductivity, with the plating study also modifying the work function. We report the successful evaluation of polymer light-emitting diodes fabricated using these electrode structures and compare their properties. It is expected that these developments will stimulate further progress in multilayer device fabrication.

Component attachment in lithographic film circuits

Conductive lithographic films are an emerging fabrication process for electronic circuits and systems. This paper reviews the manufacture and properties of CLF conductors, and describes a series of experiments to characterise bonds formed between them and surface-mount-technology (SMT) component packages employing electrically conductive adhesives. The purpose of this work is to directly compare the characteristics of solder joints between SMT packages on screen-printed alumina substrates, and conductive adhesive bonds formed between similar components and CLF substrates. The principal failure mechanisms of film-adhesive bonds in shear on various polymer substrate materials are identified and statistical data on bond strengths presented.

Test structures to characterise a novel circuit fabrication technique that uses offset lithography

This paper reports on the use of microelectronic test structures to characterise a novel fabrication technique for thin-film electronic circuit boards. In this technology, circuit tracks are formed on paper-like substrates by depositing films of a metal-loaded ink via a standard lithographic printing process. Sheet resistance and line width are electrically evaluated and these quantities are compared with optical and surface profiling measurements.

Development of paper membrane switches for fully featured computer keyboards

This paper documents the successful development and evaluation of a novel membrane switch. The process results in lower environmental burdens and manufacturing costs than current screen-printed polyester solutions. Detailed is the evaluation of offset lithographically printed conductive tracks on paper substrates for application in computer keyboard assemblies. Offset lithographic printing of conductive tracks is an emerging fabrication technique finding application in low-cost, high volume, flexible circuitry applications. Several fully featured demonstration keyboards and switch membranes have been constructed and tested. These are currently in use in office environments and are presented.