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As the demand for flip‐chip products increases, the need for low cost high volume manufacturing processes also increases. Currently solder paste printing is the wafer bumping method of choice for device pitches down to 150‐200μm. However, limitations in print quality and stencil manufacture mean that this technology is not likely to move significantly below this pitch and new methods will be required to meet the demands predicted by the technology roadmaps. This paper describes experiments conducted on carriers made from silicon for bumping of die using solder paste. An anisotropic etching process was used to generate pockets in the silicon surface into which solder paste was printed. Die were then placed against the carrier and reflowed to transfer the solder directly to the bondpads. An assessment was carried out of the potential application and limitations of this technique for device pitches at 225 and 127μm.

The purpose of this paper is to provide an overview of the research in a project aimed at developing manufacturing techniques for integrated optical and electronic interconnect printed circuit boards (OPCB) including the motivation for this research, the progress, the achievements and the interactions between the partners.

Several polymer waveguide fabrication methods were developed including direct laser write, laser ablation and inkjet printing. Polymer formulations were developed to suit the fabrication methods. Computer‐aided design (CAD) tools were developed and waveguide layout design rules were established. The CAD tools were used to lay out a complex backplane interconnect pattern to meet practical demanding specifications for use in a system demonstrator.

Novel polymer formulations for polyacrylate enable faster writing times for laser direct write fabrication. Control of the fabrication parameters enables inkjet printing of polysiloxane waveguides. Several different laser systems can be used to form waveguide structures by ablation. Establishment of waveguide layout design rules from experimental measurements and modelling enables successful first time layout of complex interconnection patterns.

The complexity and length of the waveguides in a complex backplane interconnect, beyond that achieved in this paper, is limited by the bend loss and by the propagation loss partially caused by waveguide sidewall roughness, so further research in these areas would be beneficial to give a wider range of applicability.

The paper gives an overview of advances in polymer formulation, fabrication methods and CAD tools, for manufacturing of complex hybrid‐integrated OPCBs.

To introduce the Innovative Electronics Manufacturing Research Centre Flagship Project: Integrated Optical and Electronic Interconnect PCB Manufacturing, its objectives, its consortium of three universities and ten companies and to describe the university research being carried out. This paper briefly reviews the motivation for developing novel polymer formulations, fabrication techniques, layout design rules and characterisation techniques for hybrid electronic and optical printed circuit boards (PCBs) using multimode polymer optical waveguide interconnects.

The authors are investigating a number of different fabrication techniques which they compare with each other and with modelled calculations of waveguide components. The fabrication techniques include photolithography, laser ablation, direct laser writing, embossing, extrusion and ink jet printing.

A number of design rules for polymer multimode waveguides have been found and published. Techniques for ink jetting polymer to print waveguides and laser ablation techniques have been developed. New formulations of polymer which cure faster for direct writing have also been developed.

Further work is needed to thicken the ink jet printed polymer and to investigate side wall roughness of the ablated waveguides and development of new polymer formulations for dry film. Further research is also needed on construction of prototype system demonstrators.

The fabrication techniques being developed are designed to be transferred to industrial PCB manufacturers to enable them to make higher value optical PCBs. The design rules being discovered are being entered into commercial PCB layout software to aid designers of optical PCBs.

The paper is of interest to PCB manufacturers who wish to upgrade their processes to be able to manufacture optical PCBs. The university research is original and some has been published as shown in the publications in the reference list.

The purpose of this paper is to present an outline of the development of a new process for the formation of flip‐chip interconnections using metal coated polymer microparticles.

Metal coated polymer microparticles were selectively deposited onto the bondpads of integrated circuits using electrophoresis. Thermocompression bonding was then used to bond the devices to substrates.

Particles obtained a positive surface charge following immersion in an acidic solution and this surface charge allowed the particles to be deposited electrophoretically directly onto the bondpads of an integrated circuit without the need for patterning. Thermocompression bonding of nickel/gold coated particles to gold coated substrates was achieved at temperatures as low as 160°C.

Further work is needed to test this approach using integrated circuits with finer pitch, and to use patterned substrates for assembly and reliability measurements.

This paper presents a new method for the deposition of metal coated polymer microparticles without the need for any masking or patterning processes for the formation of interconnections on integrated circuits.

The encapsulation of electronic assemblies within thermoplastic polymers is an attractive technology for the protection of circuitry used in harsh environments, such as those experienced in automotive applications. However, the relatively low‐thermal conductivity of the encapsulating polymer will introduce a thermally insulating barrier, which will impact on the dissipation of heat from the components and may result in the build‐up of stresses in the structure. This paper therefore seeks to present the results from computational models used to investigate the thermal and thermo‐mechanical issues arising during the operation of such electronic modules. In particular, a two‐shot overmoulded structure comprising an inner layer of water soluble and an outer layer of conventional engineering thermoplastics was investigated, due to this type of structure's potential to enable the easy separation of the electronics from the polymer at the end‐of‐life for recycling.

Representative finite element models of the overmoulded electronic structures were constructed and the effects of the polymer overmould were analysed through thermal and thermo‐mechanical simulations. Investigations were also carried out to explore the effect of materials properties on the overmoulded structure.

Models have shown that some power de‐rating of components is required to prevent temperatures exceeding those in unencapsulated circuits and have quantified the benefits of adding thermally conductive fillers to the polymer. Simulations have also clearly demonstrated the benefits of foamed polymers in reducing thermal stresses in the assemblies, despite their poorer thermal conductivity compared with solid polymers.

The paper illustrates the thermal issues affecting the overmoulded electronics and gives some guidelines for improving their performance.

The purpose of this paper is to present the need, and a potential solution, for in‐plane routing of optical signals for optical‐enabled circuit boards.

Multimode waveguides and integrated 45° in‐plane mirror structures were made in a low loss acrylate‐based photopolymer using excimer laser ablation. The fabrication of multimode waveguides and mirrors was carried out in a single laser system which minimised alignment issues.

It was established that in‐plane mirror fabrication using laser ablation can be achieved and can potentially be used to define mirrors in waveguides made by other methods such as photolithography.

While the concept (integrated in‐plane mirror) was demonstrated, the viability of its deployment will depend on the results of optical loss measurements for which further research is required.

The paper gives an overview of the design concept and fabrication steps for an in‐plane embedded mirror.

The purpose of this paper is to highlight a novel manufacturing process for a biochip with a multi‐electrode array (MEA) that is specifically designed for use in characterising cardio‐active substances and to demonstrate a novel proposed solution prototype that has been constructed to meet the needs of end‐users.

Practical problems encountered with conventional MEA biochips are described and a novel biochip design to tackle these problems is presented. The manufacturing approach used to produce the prototypes of that design is described and depicted.

The novel prototype MEA biochips were successfully manufactured using conventional electronics manufacturing approaches. Prototypes demonstrated limited successes in the early stages of testing. Further revisions of the feature geometry are required to implement an alternative MEA biochip that is suitably reliable.

Basic photolithography techniques have been used to construct a base substrate for proof‐of‐principle studies. Increased sophistication in manufacturing stages is required in future iterations of the proposed concept.

This paper introduces a problem encountered by MEA system adopters that requires a suitable solution. The scale up of an electronics manufacturing process‐based solution to the problems described holds much promise for the screening of new chemical entities.

The solder interconnection of components to printed circuit boards normally utilises a flux to enable the efficient removal of oxide layers from the metals to be joined. While this produces a strong metallurgical bond, the flux residue left behind after the soldering process can be detrimental to the long‐term performance of the product. Therefore, after assembly, a cleaning process is often employed to remove the residue, however, this incurs extra financial and environmental costs. In this work, organic coatings have been used to preserve copper surfaces in an oxide free state, enabling fluxless soldering to take place. These coatings, if stored appropriately, were found to be effective in preventing the oxidation of copper for several weeks, however, they are readily displaced by the soldering process allowing the active copper surface to be wetted. Wetting balance testing and surface analysis have been used to assess the preservation of copper coupons following storage in air.

To present the aims and preliminary findings of a research project to investigate the manufacture of multilayer glass substrates built up from thin glass sheets.

The approaches that may be taken to create glass substrates and the challenges involved are described. Excimer laser machining was used for the formation of microvias and other features in individual glass sheets. In addition, methods for the electroless copper metallisation of the smooth glass surfaces were studied. Finally, a technique for the lamination of the glass layers using low temperature, pressure assisted bonding was investigated.

Microvias with 100 μm diameter entry holes were successfully machined in 100 μm thick glass sheets and process windows were identified to reduce debris and hole taper. Using appropriate pre‐treatment steps, electroless copper coatings could be deposited uniformly over the smooth glass surface, however, further improvements in adhesion were found to be necessary. The direct lamination of glass layers was found to be possible using pressure and temperature applied over long periods of time. Improvements to the lamination process were made to reduce the initiation of cracks which were assessed using fatigue testing.

The feasibility of the individual steps in the fabrication of glass substrates has been demonstrated. Further work is necessary to control the processes in order to limit microcrack formation, improve copper coating adhesion and ensure uniform lamination of multiple glass layers.

The use of glass materials could enable the manufacture of substrates for high density electrical interconnect with integrated optical waveguides.