Circuit World

ISSN: 0305-6120

Article publication date: 1 June 2004



(2004), "MICROTECH 2003", Circuit World, Vol. 30 No. 2. https://doi.org/10.1108/cw.2004.21730bac.004



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited



Keywords: IMAPS, Microelectronics, Medicine

Held at the impressive Ettington Chase Conference Centre, set amongst the misty and autumnal hills of the Cotswolds, MICROTECH 2003 was an excellent 2-day Technical Conference organised by IMAPS – UK on 1 and 2 October 2003.

Day 1 Microelectronics in medicine

Roadmaps in medical electronics were explained by Dr J. Malcolm Wilkinson, of TFI Ltd, Cambridge

Dr Wilkinson outlined the opportunities in medical electronics; there is a renewed interest in medical electronics, and healthcare is becoming increasingly important. The markets are long term, something that needs to be appreciated, but the potential for medical electronics is huge. The main application areas include the following.

  1. 1.

    Diagnosis. X-ray equipment, large capital expenditure.

  2. 2.

    Ultrasound imaging.

  3. 3.

    Blood analysis. The handheld iStat system is running at 60 million a year.

  4. 4.

    Silicon chips are now disposable.

  5. 5.

    For the future, "smart"' pills, which are used to help image internally, such as the small intestine. Such pills will be used in body chemistry, in DNA testing, and new biosensors as well as DNA chips.

The market forces that drive these include the reduction of X-ray dosage; need for cost performance improvement; need for smaller portable products for point of care testing, and smaller products suitable to assist minimal access surgery.

Technology trends and benefits will include smaller ultrasound probes for cardiovascular surgery. As an example, he showed a picture of an ultrasound transducer encapsulated in a less than 1 mm diameter capsule. Monitoring systems for heart rhythm, blood pressure, blood flow, and activity (movement). Also alarm systems in sheltered accommodation, providing improved accessibility, and constant monitoring of people in flats.

Portable measurement equipment leads to cost performance improvements, makes for better ease of use, has fewer wires and tubes at bedside, and provides more valuable physiological quantities.

Another area was in drug delivery – here nebulisers, micropumps, able to reliably deliver small amounts of drugs, meet a demand. Market forces include delivery mechanisms for larger molecular weight drugs; a need for painless/needle free delivery. These technologies can also offer IPR protection to extend drug life and a consideration of regulatory and litigation issues.

Trends and benefits include: smart patches – minimal invasive monitoring; implanted devices; pacemakers; bladder and muscle control; Hearing aids – cochlear implant systems, surgical tools including cardiovascular catheters, ultrasound probes; robotic surgery; minute catheter systems.

In medical applications, he said, the market is there, and represents a significant opportunity. It would certainly seem so.

John Alderman, NMRC, Ireland looked at some examples of polymer use for biosensors and biomedical devices

Mr Alderman looked at the reuse possibilities, and gave some examples of where polymers are used in biomedical devices. The problem, he said, is with the packaging, not with the silicon, it is everything else that goes with it. The reuse possibilities were endless – they included future ICT devices and products which will contain technologies from different domains such as electronics, materials, optics, physics, chemistry and biology, in fact a convergence of traditional sciences.

Within the next 3-10 years, nanotechnolgy will be the toolbox of new techniques, he said, and by modifying the use of standard technologies, by using the correct materials, including flexible materials, devices that can fit inside a shoe and measure the movement of a foot, for example, would be possible. NMRC is looking at the direct deposition of such sensor arrays.

In the Bionics group he heads, they have some specific objectives. They are researching core technologies, seeking biocompatability, i.e. how to get cells to grow. Why is this important? It is all down to cash, in the end, he said. Neuro beats cardio! They are pursuing a parallel examination of neural networks, which means growing neuron cells on polyimide, and this means the initiation of a retinal prostheses activity in Ireland, where patients are already undergoing treatment. They grow retinal cells using polyimide as a base, and with the application of platinum and gold films of 15 microns thick.

He also explained the EU project called TUBA – transceiver and inertial unit for biomedical applications, with an example of respirometric biochip and system for embryo assessment. The work on microelectronic modelling and stimulation meant that with the many forms and types of attractive polymers available the electronic treatment of cancer, and wound treatment, is now a possibility.

Jorgen Skindhoj, of Oticon in Denmark, explained all about ultra thin chip-stack and flip chip packages for hearing aids using 50 μ thin dies

Needless to say, with hearing aids, size is important. They need to be ultra-thin, have good cosmetics, and increased reliability. Oticon is an old company, going back 100 years to1904, when they were involved in diagnostics, telecommunication, working with companies such as Nokia, ChemiTech.

So what is a hearing aid? Jorgen went through a description of the component parts, where the IC is a silicone wafer used as a signal processor, with circuitry on the surface of some 5-10 microns, They use a chip stacking technology on ceramic substrates, known as Chip on Chip, and they are working on an EU project called Flex- Si, where a reduction in IC thickness is down to 180 microns, and the total thickness of the hybrid is now 1.4mm. Reliability is measured by a damp/heat test for 21 days at 40°C @ 93 per cent RH, plus a solder stress test. As for size, the goal is to have a 200 micron CSP added to the IC. Functionality, low power, light shielding, and EMC are all looked at in the process flow. Wirebonding is critical, he said, as is good accuracy in die placement.

Oticon is now using a PCB as a base instead of ceramics, it has proved to be one-fifth cheaper. Reliability is excellent, there is better adhesion, and a quicker set-up time. Their roadmap is to continue production of existing and new products with chip on chip technology, whilst continuing with further miniaturisation combining higher reliability. Oticon, he concluded, choose high and simple universal solutions.

Peter Laintenberger from Sphere Medical Ltd, Cambridge talked to us about a novel sensing technology for blood gases and clinical diagnostics

His company produces high technology sensing equipment for clinical diagnostics and they regard the medical markets as significant. Microsystems bring benefits to the hospital environment, and although the stress is on low cost solutions, there are very good margins to be made. There are many different ways of treating patients, but in particular is the continuing interest in the diagnostics market, where the trend is to bring the lab to the patient, not bits of the patient to the lab! Nurses are the most overworked people in our society, he confirmed, and medical electronics have to assist them, be easy to use, and fit into the hospital environment.

Sphere Medical Ltd is a small company, incorporated in 2002, and based in Cambridge where they are using technology which is essentially ex-Siemens, but with additional functionality. Their products have to be validated on the market, so it is vital to define with their customers what their equipment has to do. They have a family of 16 patents around their equipment, and recognise that flexibility ion design is important, as is working with strategic channel access partners, as the costs of sales for a small company can be very high.

In looking at a micro-machined transducer, they had to consider the usual demands based on cost, reproducabilty, manufacturability, flexibility and response time, and size. In the field of blood gas analysis, present measuring systems are slow, but all patients in an ICU have their blood pressure monitored.

So Sphere has produced a molecular imprinted polymer, which is quick, accurate and disposable. It is an intra-vascular, semi-continuous measurement system, patient-friendly. It is called, aptly, the Proxima system.

Norman Stockham of TWI Ltd, Cambridge, looked at microtechnology for medical implants and surgical tools

His paper covered packaging – trends – Materials and some conclusions. TWI is a member of EPPIC and has a Faraday partnership. He mentioned that surgical tools and the trends to implant lead towards smaller size and weight, they are getting smarter, include greater complexity in a field of multi-technology products, and reliability is becoming more critical. As always, the cost needs to be lower.

As examples he mentioned catheters where the tip of the sensor is now < 1 mm in diameter, where heart pacemakers have significantly reduced in size over the last 20 years and yet have become significantly more reliable.

Diode laser welding is increasingly in use on interconnects, wire terminations for medical products including hearing aids. No solder = no flux, so one can automate. Polymeric resins are increasingly in use as adhesives, coatings and as protection for medical devices, as well as coatings for biopsy needles. Laser chemical vapour deposition could be used to run tracks around housings, possibly. Polymer inkjet printing, and microjet printing are the topics for what is next column.

The industry is moving quite rapidly in technology terms. Products are smarter, lower in weight, smaller in size, and therefore less invasive.

Jordi Aguilo of CNM Barcelona talked about microprobe multisensor for graft viability monitoring during organ preservation and transplant

A very nice man from Spain said, in detail, about how his company was bringing together medical knowledge with technological skills. In the field of organ transplants, there were long waiting lists, the patient life was dependent upon finding an adequate donor; there were difficult procedures to follow to evaluate organ viability, and only a short preservation time for the organ is allowed.

From a clinical point of view CNM has a viable product, which is a multi-microsensor to measure temperature, pH and potassium. It is a classic example of where microdevices are becoming the new business market, and have overcome the challenge of microelectronics in medical applications. CNM has microelectronic equipment that will be of great assistance in the organ transplants.

The CNM MicroCard system was described in detail, protocols have been written, and the system, once approved by the EC Transplant Authority, will be a boon to cardio-vascular surgeons around the world.

Andrew Pacey of Advotek discussed the manufacturing challenges of a new concept

Mr Pacey energetically took the delegates through the operations of his company, Advotek. He started out 3 years back to act as a hub for a global network of consultants, scientists, OEMs and sub-contractors from the medical device and microelectronics industries. They specialise in the product development and placement of innovative electro-mechanical medical devices, and he told a cautionary tale of the development of a product, the IVUS catheter, which, like so many, started out in this country, full of hope and enthusiasm, only to disappear off-shore to a foreign company due to a lack of funding in the UK.

However, much was learnt from that exercise, and now Advotek has an established innovation and development hub to capitalise on the knowledge base, and they have set up a product development protocol which helps optimise development efficiency. They are currently working on pH catheters, Doppler probes, RF surgical devices and heart monitors.

Finally, Dr David Hitchings of dsTEC Ltd, in Staffordshire ran through a review of airflow sensor technology

He took a comprehensive look at the various ways in which airflow sensors operate, and the methodology of their manufacture, their pros and cons. It was his conclusion that micromachined gas flow sensors have many performance advantages over conventional flow sensors, they include high sensitivity and speed of response. In addition, their small size, low cost, low power consumption offer great potential in addressing a mass-market demand for point-of-care application,

Day 2 Polymers for advanced microelectronic fabrication and Structures

Robert Kay, from Heriot Watt University, speaking on behalf of MAT21, spoke about low temperature flip-chip packaging based on screen printing technology

The MAT21 project, funded by the British funding agency, EPSRC, aims to integrate microsystems and flip-chip technology into commercial contract high volume electronics manufacturing assembly lines. The technology is based on flip-chip applications and is viewed as a step towards advanced assembly and packaging processes for future MEMS technology markets. The project seeks to deliver commercially viable processes for ultra-fine sub-100 μm pitch connections using stencil printing at a length scale of one order magnitude less than presently available.

The project consortium of two Universities: Heriot-Watt and Greenwich are engaged in a highly interdisciplinary research program involving microsystems manufacturing, materials science and computational modelling. The consortium is strengthened by the industrial support from leading-edge companies including Celestica, Cookson, Merlin Circuit Technology, DEK Printing Machines, Electronic Technology Services and Micro-Emissive Displays, which cover the whole supply and manufacturing chains in electronics packaging.

The rapid growth rate of microsystems manufacturing (30 per cent per annum) makes it the world's fastest growing manufacturing industry. The trend towards ever increasing miniaturisation and the capacity to shrink electronic devices while multiplying their capabilities has profoundly changed both technology and society, for example, high performance computing systems, mobile phones and visualisation equipment. Research into microsystem technology for sensing and actuation has resulted in a number of Universities and small companies producing miniature components. In general, microsystem components have not found their way into mass produced commercial products because cost- effective packaging and assembly to standard microelectronics has presented a critical stumbling block (one notable exception is their use in accelerometers in car airbags). The challenge is now to interface such technology into commercial electronic contract manufacture assembly lines. Or should we say – was?

Robert Kay, in a detailed and absorbing presentation, made it evident that a low temperature, fine pitch (sub-100 μm) high-volume flip-chip assembly process has been developed which slots in well to SMT manufacturing lines, enabling low cost microsystem packaging.

Professor David Whalley looked at the characterisation of anisotropic conductive adhesive compression during the assembly process

Anisotropically conductive adhesives (ACAs) have emerged as an important joining technology in a number of significant application areas, such as flat panel display assembly and smart cards. These materials rely upon the trapping of conductive particles between the conductive pads on the two parts being connected and then retention of sufficient contact force following adhesive cure to create stable low resistance electrical connections.

David Whalley discussed the models of the ACA assembly process that have been developed earlier. Such models may be used to predict the time for adhesive resin flow out and whether this can be successfully achieved before resin cure. Modelling has also been used to provide significant insights into the effects of component and substrate bond pad geometry on the resin flow distribution and hence on the resulting conductive particle distribution. These models have, however, only been experimentally validated to a very limited extent. David described a new experimental technique, which has been developed to allow continuous monitoring of the adhesive thickness throughout the compression process. This technique applies a controlled assembly force through a linear "voice coil" type actuator and the resulting changes in capacitance of the adhesive material can be used to monitor its thickness. The data from tests using this technique show, for example, the effect of the conductor particle stiffness on the rate of adhesive compression during the later stages of the compression process. Such data will be used to further improve more sophisticated models of the ACA assembly process, which will both lead to a better understanding of the process and also facilitate establishment of design rules for different applications.

In conclusion, he thanked his partners in this research, namely Helge Kristiansen, SINTEF, Oslo, Norway and Johan Liu, Chalmers University of Technology, Goteborg, Sweden.

Professor Chris Bailey, from the University of Greenwich, talked about an investigation into the coupling between a VCSEL and a polymer waveguide for optical-electrical circuit boards (OECB) backplanes

The first generation of optical interconnects over backplanes consisted of discrete optical fibre interconnects; the second generation had fibre-on-board (FOB) technology, but now, with the demand for greater bandwidth increasing in all electronic sectors, from consumer to telecom, physical limitations have been reached. A third generation on embedded waveguides integrated into the PCB is now needed to provide a low cost alternative of optical interconnects. Why vertical channel surface emitting lasers (VCSELs)? They are cheaper than packaged lasers, lend themselves to passive alignment, and are easier to couple to waveguides, and overall provide a low cost solution. Why polymer waveguides? Well, you can build them into the PCB, and they are easier to manufacture than glass, with acceptable attenuation.

Professor Bailey covered a range of considerations that had to be encompassed in the investigation – how to handle flip-chip assembly? Mirrors – assembled, or integrated? Alignment is critical here. Assembled mirrors are low tech but high cost, whereas integrated mirrors are high tech but low cost. Can you use integrated components with a standard PCB, will they be reliable? Other factors included misalignment, thermal management, material mismatch, and interconnect stress. Much work still to be done, but it appears to be in the right hands.

Improved characterisation of electroluminescent lamps through environmental and electrical stress testing

Vince Arancio, from DuPont Microcircuit Materials, Bristol, explained that with the increasing use of inorganic electroluminescent (EL) lamps in very demanding applications, such as in the auto sector, the importance of accurate and reliable lamp assessment has become even greater. For a number of manufacturers, however, the challenge has been how to verify the performance of lamps to achieve consistent operation for some of these more taxing applications.

Throughout the long and promising history of EL lamps, there has never been the long awaited breakthrough and wide acceptance in the market place. There were many reasons for this, but two were dominant, namely high cost and poor reliability. To counter high cost, two main developments allowed significant cost reductions. Improved paste technology and innovative encapsulation of phosphor powder played a major role in reducing overall lamp costs, as did the use of chip or semiconductor based inverters. As a consequence, in the early 1990s, Timex took advantage of these developments and used EL lamps by the millions to backlight watches.

On the reliability front, however, although the EL phenomenon is an extremely reliable and robust technology, it was found that the total lamp construction was prone to failure and there are many areas of potential concern particularly with lamps being used today in more demanding environments such as in the Automotive sector.

The importance of high quality lamp assessment has therefore become even greater as long-term reliable performance is sought, and Mr Arancio and his colleague Mr Dorfman at Du Pont have now completed a programme to fully understand EL lamp reliability, as their paper demonstrated so clearly.

The afternoon of the second day was devoted to a Market Watch Panel Session, and here the panel, consisting of Mr Alan Fairbairn of SEMX UK, Mr Mark Hutton of BPA, Dr Malcolm Wilkinson of Europractice, and Dr Peter Barnwell – President IMAPS North America presented their thoughts on various topics relating to the microelectronics industry.

The global economic outlook – we see a slow improvement in the USA, and some overall improvement elsewhere, so there is room for cautious optimism. Semicons are also improving; here too we see the beginning of an upturn.

Dr P. Barnwell gave a synopsis on the paper entitled China's Advanced Packaging Trends and Infrastructure Development, written by E. Jan Vardamna, of TechSearch International Inc. In this paper, it was said that China is seen by many as the dominant driving force in our industry. It is already the fourth largest manufacturing country in the world, but they import most of their semiconductors. PC growth rate in China is now for 13 million domestic sales, making them the world's second largest PC market. For mobile phones, there is an internal demand for 4-5 million per month now, rising to 380 million by 2005. However, there is an over-production of handsets, capacity is only 20 million units. The semiconductor industry has seen huge expansion, with 80 per cent of them imported. However, there are seven new wafer fab factories under construction. EMS is now expanding in China, and there are 21 universities providing technology training and R&D in electronics, and microelectronics.

The Chinese people are being educated to work in the industry.

Dr Barnwell went on to look at "Trends in microelectronic packaging". It has been the longest, deepest recession we have ever seen, he accurately observed. But whilst he sees some recovery going on, which is in itself very fundamental, it will not go back to where it was. Things have changed, and a massive infrastructure of low cost manufacture is now established, such that there is over-capacity in many areas. Many companies have been weakened; the larger companies may leapfrog into new positions. Government policies to promote innovation would be of considerable assistance now that the emphasis on manufacture has changed so geographically and emphatically.

New opportunities exist in packaging – Microsystems, MEMS, MEOMS, optical, high microwave – 10GHz+range, automotive. New technologies include advanced ceramics, and advanced PCBs.

There is a need for focused and collaborative R&D, with a design initiative for novel end user applications – killer applications?

The Government appears confused over the role of UK versus Europe. The lack of Government support for our industry is quite evident, especially as a Government Minister was quoted as saying "Electronics is not a strategically important industry"'.

Dr Wilkinson asked, "What makes a killer application?" He looked at various subjects, including ink jet heads, fluid sensors, pressure sensors, accelerometers; they had a common factor, which is that technology must deliver a significant cost performance advantage. A lot of investment is needed to create a market, and he looked at the factors which pushed a market forward and factors which held it back.

A list of "killer applications'' could include RF MEMS for mobile communications; micro reactors; fuel cells; drug delivery systems; RFID tags – ID cards; and tyre pressure sensors.

All major supermarkets are going for RFID tags, and is an example of where high volume production fuels the next technology wave. RF MEMS is a classic "killer application'' in this regard.

Mark Hutton of BPA said that this is a mature industry, and large mature markets become splintered into a number of niche sectors. Where can we add value to what we do? Concentrate on what you do well and make it better, he exhorted.

In this competitive and global market, sound advice indeed.

IMAPS are to be congratulated in organising a well-attended, well-considered technical conference that covered a range of products and their application in a diverse and changing market place.

The Medieval Feast on the evening of 1 October was a jolly occasion; it came as a relief to some present that donning full armour and taking part in a sword fight was not de rigeur after all. For those concerned with menu authenticity some research may be needed on the existence of coleslaw in those far-off days, but no one could fault the conviviality of the evening, a conviviality that had a particular IMAPS flavour.