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EETE SEPT 2013

INTERCONNECTS High resolution copper ink printing for electronic interconnects By Dr Pufinji Obene and Dr Ian Clark printed electronic s is an example of additive manufacturing where only materials that are contributing to the final circuit are deposited, offering a simpler, more cost effective and cleaner process with little or no waste. Today, the vast majority of integrated circuit boards are manufactured by applying the functional materials everywhere and then removing by means of a mask or etchant, the areas not required. The most commonly used material combination for electronic circuits is copper on FR4 laminate and in many cases up to 75% of the copper is etched back off to produce the desired base circuitry. Although further processing steps such as nickel and gold coating are additive in nature, the passive, active and MEMs devices that populate such base boards to produce final integrated electronic circuit devices are also up to 50% subtractive in nature. The adoption of additive manufacturing could potentially save up to 25-50% of material component costs. The technology of additive manufacturing will enable manufacturers to deposit conducting and insulating fluids including: adhesives, resists, liquid crystal fluids, metallic inks, nano-inks, semiconductor inks and a wide range of other fluids as well as regular inks, using well known deposition techniques such as screen, inkjet, gravure and electrostatic printing, together with curing systems such as convection oven, infra red and laser sintering. It will also allow passive components: resistors, capacitors, inductors, switches and relays as well as thin film transistors, organic light emitting diodes (OLE D) and logic gates. To date additive processes are used in products when fabrication costs and flexibility outweighs size and performance considerations. Typical uses are in organic and large area electronic applications. Research and development in the field of OLE Ds is proceeding rapidly and may lead to future applications in large information displays, automotive dashboards, home and office lighting and flexible displays. Because OLE Ds refresh faster than LCDs (almost 1,000 times faster) a device with an OLE D display could change information effectively in real time. Video images could be much more realistic and constantly Fig. 2: Detailed image of a manufactured print head. updated. The newspaper of the future might be based on an OLE D display that refreshes with updated news and like a regular newspaper could be folded up after reading and placed back in the bag, briefcase or backpack. A flexible OLE D display is very likely to be the basis of the next generation smart device used for all forms of written communication Intrinsiq Materials (IML) of Farnborough, UK, has teamed up with Swindon-based automotive sensor maker Precision Varionic International (PVI) to use nanocopper conductive inks as the interconnect in high precision printed electronic components for a wide range of applications. PVI is developing a mid to high range production printing system called High Resolution ElectroStatic Ink JET (ES JET ) for the printed electronics marketplace. This patented electrostatic printer technology provides both higher resolution (feature size and print channel spacing) and a broader range of ink type compatibility than conventional ink jet technologies. In contrast to current high-resolution inkjet printers based on piezo operation, ES JET has no moving parts. This allows very high print channel density to be achieved since print channels can be arranged over a two dimensional surface, rather than being in a single print channel line. Typical channel spacing in commercial inkjet printing equipment is 50 to 360dpi, whereas with the lab prototype ES - JET printer, resolution of 2116 dpi has been demonstrated with current development aimed at achieving up to 10,000 dpi. A typical Fig. 1: Print head layout to achieve high print channel density. Dr Pufinji Obene is Operations Director at Precision Varionic International – www.pvi.co.uk Dr Ian E Clark is Sales & Marketing Director at Intrinsiq Materials Ltd - www.intrinsiqmaterials.com Fig. 3: Sample print pattern of a low viscosity ink having a size 7.1±0.2μm. 20 Electronic Engineering Times Europe September 2013 www.electronics-eetimes.com


EETE SEPT 2013
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