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The purpose of this paper is to demonstrate laser microvia drilling of polyimide thin films from multiple sources before metallic sputtering. This process flow reduces Flexible Printed Circuit Board (FPCB) material, chemical and operational costs by 90 per cent in the construction of flexible circuits.

The UV laser percussion drilling of microvias in 25 μm thick polyimide films with low coefficients of thermal expansion (CTE) and elastic modulii was investigated. Results were obtained using Scanning Electron Microscopy and Surface Profilometry. Polyimide films tested included: Dupont™ Kapton^® EN; Kolon^® GP and LV; Apical^® NPI; and Taimide™ TA‐T.

There was no direct relationship between the top and bottom diameters and ablation depth rates between the polyimide films tested using the same test conditions. There was a direct relationship with exit diameters and etch rates at different laser pulse frequency rates and fluence levels. Laser pulse rates at 30 kHz produced 20 per cent larger exit diameters than at 70 kHz, however at 70 kHz the first pulse etched 16.5 per cent more material. High fluence levels etched more material but with a lower etch efficiency rate. Other microvia quality concerns such as surface swelling, membrane residues on the bottom side and surface debris inside the microvias were observed. Nanoscale powder‐like surface debris was observed on all samples in all test conditions.

This is the first comparison of material specifications and costs for films from multiple polyimide manufactures and laser microvia drilling. The paper also is the first to demonstrate results using a JDSU™ Lightwave Q302^® laser rail. The results provide the first insights into potential microvia membrane issues and debris characteristics.

For TAB tapes and flex circuitry, laminates with adhesives (3‐layer laminates) are commonly used. The drawbacks of adhesives are well known. Adhesiveless flexible copper‐polyimide laminates (2‐layer laminates) could avoid such disadvantages. Two‐layer thin film laminates may be produced using sputtering technology. Good adhesion strength between the copper and the polyimide film may be achieved by means of special plasma treatment. The advantages and disadvantages of 2‐layer flexible thin film laminates are discussed in this paper, along with their different production methods. The adhesion strength of 2‐layer laminates in comparison with 3‐layer laminates will be pointed out. Future uses of 2‐layer flexible thin film laminates will be considered, along with their benefits.

A project has been undertaken to evaluate new sources of flexible circuit materials for use by the author's company. The vast majority of flexible circuits are fabricated from polyimide film and acrylic adhesive circuit materials. One new polyimide film has been evaluated as an alternative dielectric film. Thirteen suppliers of flexible circuit materials have been identified. The paper discusses the results of the mechanical and electrical properties evaluation study of some of the new sources of flexible circuit materials.

Coating and lithography steps in thin‐film processing require planar and smooth surfaces. Usually ceramic substrates with as‐fired surface roughness of R_a < 0.1µm or with polished surfaces for advanced requirements are used. In general, a thick‐film hybrid has an inappropriate surface for further successful thin‐film processing. In this work, the influence of surface roughness and topography on the properties of thin‐film conductors and the fabrication of vias is investigated. Surface smoothing and local planarisation can be achieved by the use of a thick‐film overglaze or by coating the surface with polyimide prior to thin‐film processing. The improvements in conductor and via yield are measured by adequate test structures with a conductor width of 25µm. Based on the results, a process is given to provide a thick‐film multilayer with a sufficient smooth and planar surface suitable for thin‐film processes.

The purpose of this paper is to discuss the fabrication technology and test of thermo-pneumatic actuator utilizing Si₃N₄-polyimide thin film membrane. Thin film polyimide membrane capped with Si₃N₄ thin layer is used as actuator membrane which is able to deform through thermal forces inside an isolated chamber. The fabricated membrane will be suitable for thermo-pneumatic-based membrane actuation for lab-on-chip application.

The actuator device consisting of a micro-heater, a Si-based micro-chamber and a heat-sensitive square-shaped membrane is fabricated using surface and bulk-micromachining process, with an additional adhesive bonding process. The polyimide membrane is capped with a thin silicon nitride layer that is fabricated by using etch stop technique and spin coating.

The deformation property of the membrane depend on the volumetric expansion of air particles in the heat chamber as a result of temperature increase generated from the micro-heater inside the chamber. Preliminary testing showed that the fabricated micro-heater has the capability to generate heat in the chamber with a temperature increase of 18.8 °C/min. Analysis on membrane deflection against temperature increase showed that heat-sensitive thin polyimide membrane can perform the deflection up to 65 μm for a temperature increase of 57°C.

The dual layer polyimide capped with Si₃N₄ was used as the membrane material. The nitride layer allowed the polyimide membrane for working at extreme heat condition. The process technique is simple implementing standard micro-electro-mechanical systems process.

The aim of this study was to fabricate polyimide (PI)/Al₂O₃ composite films via surface modification and ion exchange techniques, and examine their properties.

The method involves hydrolyzing the PI film double surface layers in an aqueous potassium hydroxide (KOH) solution and incorporating aluminium ions (Al3+) into the hydrolyzed layers of the PI film via subsequent ion exchange, followed by a treatment of the Al3+-loaded PI films with an aqueous ammonia solution, which leads to the formation of Al(OH)₃ in the surface-modified layers. After a final thermal annealing treatment in ambient air, the Al(OH)₃ decomposes to Al₂O₃, and forms composite layers on both surfaces of the re-imidized PI film.

The PI/Al₂O₃ composite film obtained with a 6 hours of KOH treatment exhibited excellent thermal stability, good mechanical properties and better electric breakdown strength and corona-resistance properties than the pristine PI film.

The method for obtaining the composite films in this paper is worth consideration, but additional research will be needed. Furthermore, this method is of general importance for the fabrication of composite PI films with tailored properties.

This study showed that surface modification and ion-exchange techniques are powerful methodologies for the fabrication of PI/Al₂O₃ composite films.

The purpose of this paper is to present a novel manufacturing process that aims to pattern metal tracks onto polyimide at atmospheric pressure and ambient environment. The process can be scaled up for industrial applications.

From a thorough literature survey, different approaches were carried out for processing polyimide. Following a design of experiments for the processing and various characterisation techniques, a micro‐coil was manufactured as a test demonstrator.

The characteristics of some main formaldehyde‐based electroless copper baths were compared. The quality of the sidewalls was characterised and the performance of the process was assessed.

This paper demonstrates a high‐value manufacturing technique that is mass manufacturable, low cost and suitable for use on 3D surfaces. Criteria required for the development of a direct‐writing process have been described. The issues surrounding electroless plating on polyimide have been explained.

This paper aims to study the tribological behavior of the WS2/oil-impregnated porous polyimide (PPI) solid/liquid composite system, in which both PFPE (perfluoropolyether) and SiCH (silahydrocarbons) oils with different hydrocarbon chains were used, respectively. Lubricating mechanism of the composite system was also explored.

The tribological behaviors of the WS2 films against the PPI cylindrical pins before and after immersing oil were evaluated under different loads by a reciprocating-type ball-on-disc tribometer.

The composite system exhibited the low and stable friction coefficient after the running-in stage, and the lubricant oil played a positive effect. It was found that the WS2/PFPE composite system exhibited more excellent lubricating property, although sole SiCH far exceeds PFPE in lubrication. The abnormal phenomenon mainly resulted from the influence of the oil amount. XRD results on the wear track surfaces indicated that PFPE and SiCH oils with different hydrocarbon chains were likely to preferentially adsorb to the edge plane and basal plane of the WS2 crystals, respectively.

In previous studies, liquid lubricants were directly dripped or spin-coated on the solid lubricant surface. Based on its potential advantage in application, the tribological behavior and mechanism of the solid lubricating film/oil-impregnated PPI composite system were investigated in this study.

Flexible circuitry and flexible interconnects are high technology products that require a good understanding of flexible laminates and their properties to ensure the proper design of a functional part. Many designers use flexible interconnects for packaging and multiplane interconnections, but incorrectly compare flexible materials to rigid laminates. Flexible materials and design considerations when using flexible materials are reviewed, with a brief overview of the combination of flex and rigid materials in a flex/rigid multilayer circuit.

A review of state‐of‐the‐art technology pertinent to tape automated bonding (for fine pitch, high I/O, high performance, high yield, high volume and high reliability) is presented. Emphasis is placed on a new understanding of the key elements (for example, tapes, bumps, inner lead bonding, testing and burn‐in on tape‐with‐chip, encapsulation, outer lead bonding, thermal management, reliability and rework) of this rapidly moving technology.