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The past few decades have seen an escalation of power densities in electronic devices, and in particular in microprocessor chips. Together with the continuing trend of reduction in device dimensions this has led to dramatic increase in the thermal issues within electronic circuits. The electrons, in their passage through the conductors and semiconductors, produce a lot of heat, and they negatively affect the final performance of the circuit. The temperature changes the reliability and durability of the electrical and electronic components. A device malfunction is almost always caused by a thermal problem. High temperatures not only make the system work unstable but also reduce the average life of the components, thus leading to their deterioration. This has lead to many Lithium battery fire incidents involving hoverboards, smartphones, and electric vehicles posing a serious public safety concern and creating a surge in demand for improved battery safety technologies and thermal management solutions.
The quantity of heat depends on the power and on circuit design. The optimal arrangement of the electronic component, on a circuit, should provide for excellent air circulation and intelligent placement of the parts, taking into consideration the specifications of the electrical circuit.
Thermal management is therefore becoming increasingly more critical and fundamental to ensuring that electronic devices operate within their specification. Although a thermal management system may make use of all modes of heat transfer to maintain temperatures within their appropriate limits and to ensure optimum performance and reliability, conductive heat transfer is typically used to spread the heat out from its point of generation and into the extended surface area of a heat sink.
In general, various interfaces will exist between the high power, heat generating component and the eventual heatsink. Some of these interfaces will consist of permanent bonds, such as solders or adhesives, but often a non-permanent interface will form part of the heat transfer path, e.g. where a component is bolted to a heatsink or between an assembled module and a chassis.
When these surfaces are attached together there will almost always be only a small area of actual mechanical contact between the two surfaces at this interface, due to the micro-scale surface roughness and waviness of the surfaces. This will have an impact on the heat conduction across the interface, as there will be gaps filled with low thermal conductivity air.
Electronic thermal management materials also abbreviated as ETMM refers to the materials that are used between different substrates for the efficient heat dissipation within the electronic devices. These management systems not only ensures optimum performance of the electronic devices but also aids in reducing contact resistance. Therefore, thermal management materials are becoming more essential to ensure the electronic assemblies operate within the required specifications.
Thermal conductivity (k) is the intrinsic property of a material which relates its ability to conduct heat. Heat transfer by conduction involves transfer of energy within a material without any motion of the material as a whole. Conduction takes place when a temperature gradient exists in a solid (or stationary fluid) medium. Conductive heat flow occurs in the direction of decreasing temperature because higher temperature equates to higher molecular energy or more molecular movement.
Thermal resistance, R, is the temperature difference, at steady state, between two defined surfaces of a material or construction that induces a unit heat flow rate through a unit area, and is defined as Km2/W. Thermal resistance can, therefore, be shown to be directly proportional to thickness and makes the basic assumption that the material is homogeneous. For non-homogeneous materials the relationship may not be linear. However, because true surfaces are never perfectly smooth the contact between surfaces can also contribute to the resistance
of heat-flow. This is referred to as surface contact resistance and can be a factor in correctly determining heat flow.
The first precaution to take is to adopt and implement a strategy to disperse the heat of the electrical and electronic circuits. The heat transfer efficiency of the heat sinks is linked to the thermal resistance between the heat sink and the ambient space. It measures the ability of a material to dissipate heat. An ideal heat sink material must have high thermal conductivity, low thermal expansion coefficient, low density, and low cost.
The irregularity of real surfaces is therefore a primary cause of thermal contact resistance. In order to minimize the thermal contact resistance, filler materials, known as thermal interface materials (TIMs) are therefore generally required to enhance the contact between the
mating surfaces . The effective total thermal resistance at the interface between two materials is the sum of the resistance due to the
thermal conductivity of the TIM and contact resistance between the TIM and the two contacting surfaces.
Proper and effective thermal management and heat dissipation for electronic devices from computers to LED lighting and solar panels are critical for performance and reliability. Thermal conductivity of a thermal interface adhesive or compound is commonly used as a “gauge” of how good it may be in helping to dissipate heat from a device. This should not be the only measure for the potential effectiveness of
a material as a thermal interface for as other parameters are of equal importance.
In applications where heat is generated from components of various heights and there is a need to dissipate the heat to a heat-sink or an external metal casing, thermal interface pads are employed. These products are soft, conformable sheets in thickness from 0.125 mm to 10 mm or thicker that can be compressed to give a good thermal interface.
Thermal Interface Pads
The softness of the gap fill pads helps eliminate air gaps between components and the heat-sink while conforming to the curvature and warp of the mating surfaces. Generally, these are soft and easily of compressible to accommodate the different profile heights of multiple components and remain stress- free whilst providing outstanding mechanical shock absorption. Gap pads offer a good combination of thermal performance, cost-effectiveness and ease of manufacture. They can be supplied in many forms, such as sheets, tubes, moldings, rolls or die cut parts.
Thermal interface pads are traditionally made using a silicone filled with a thermally conductive filler material, which may be either Al2O3 or. However, for more demanding applications, where silicone outgassing could be an issue, acrylic or epoxy based formulations are commonly employed.
Phase change materials
Phase Change Materials (PCMs) are solid materials at room temperature that melt at operating temperatures forming intimate contact on the mating surfaces to produce a low thermal resistance. Generally, PCM materials are used as a replacement for grease, which can
be messy in a production environment and has been shown to exhibit migration, or pump out issues, particularly under conditions where thermal cycling occurs.
Generally the phase change occurs at a temperature of 50 – 70⁰C. This is chosen so that the material will flow when the device is initially powered up but will not flow during transportation or storage. Typically these materials are composed of a mixture of organic binders,
thermally conductive fillers, and an optional substrate such as polyimide or aluminium to give additional functionality and ease of handling.
In use the PCM material will initially perform like a dry joint. However, as the operating temperature increases the material will flow under the pressure of the clips used to attach the heatsink. As the material flows it displaces the interstitial air and this lowers the thermal resistance. The next time the device is powered up there will not be this delay in achieving good thermal management as the thermal joint has already been established.
Phase change materials are substances that absorb and release thermal energy (heat) during the process of melting and freezing at defined temperatures . They are called “phase change” materials because they transition from one of the two fundamental states of matter – solid and liquid – to the other during the thermal cycling process. By melting and solidifying at the phase change temperature (PCT), a PCM is capable of storing and releasing large amounts of energy to provide useful heat/cooling. The phase transition may also be between non-classical states of matter, such as the conformity of crystals, where the material goes from conforming to one crystalline structure to conforming to another, which may be a higher or lower energy state.
They are also useful in military applications. Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. Latent heat energy storage systems that utilize Phase Change Materials (PCMs) present an effective way of storing thermal energy and offer key advantages such as high-energy storage density, high heat of fusion values, and greater stability in temperature control. Military vehicles frequently undergo high-transient thermal loads and often do not provide adequate cooling for powertrain subsystems.
Thermally Conductive Insulators
Thermally conductive insulators are thin, thermally conductive materials designed for a wide range of applications where good thermal transfer and electrical isolation are required. One of the most critical parameters for insulators is the dielectric breakdown voltage.
The dielectric breakdown voltage is defined as the maximum electrical field strength that the material can withstand without breaking down and losing its insulation properties. Thermally conductive insulators can be supplied in sheet, tube, rolls or die-cut form depending on
the end application.
Thermally and Electrically Conductive Materials Where electrical conduction is needed as well as thermal conductivity it will be necessary to use a thermally and electrically conductive material. For solid pads these materials are predominantly graphite based whilst electrically conductive greases and pastes are often based on a silicone matrix filled with electrically conductive particles or fibres. Generally these products are used for high power electrical applications, power switches, circuit breakers and grounding semiconductor components.
Thermally Conductive Adhesive Tapes
Thermally conductive adhesive tapes are used to mechanically and thermally bond electronic components to heat sinks. These tapes allow for easy joining of many substrates with light pressure in just seconds at room temperature. These tapes are permanently tacky consisting of a pressure sensitive adhesive (PSA) film filled with ceramic particles. These particles allow thermal conduction through the tape. The tape provides an excellent combination of thermal conductivity, electrical isolation and adhesion.
Thermal Greases
Thermal greases are low viscosity, thermally conductive materials which can be used to transfer heat between a heatsink and a heat source. These materials are used to provide a very thin bond line thickness (BLT) which optimises the thermal transfer.
Thermal Gels
Thermal gels are one or two part systems which are cured in place to give a permanent and durable thermal interface. In the uncured state, these materials are soft enough to assemble components under low force and then cure to a harder state.
Thermal Putties
Of all the TIMs commercially available, thermal putties are perhaps the most interesting and offer the designer the most opportunities for low total cost of ownership thermal management. These products are one-part, fully cured thermally conductive materials which can be applied to a surface using a number of means. These materials are supplied fully cured but have a viscosity which allows them to be dispensed or printed in the same way as a conventional grease.
These materials are ultra-soft, transfer little or no pressure between bonded surfaces and are more viscous than grease or phase change materials so many of the problems associated with these classes of materials are removed. These materials are especially useful for filling large gaps or for areas where there is significant variation in surface height or roughness.
Compressible Soft-PGS thermal interface material (TIM)
Panasonic Automotive & Industrial Systems Europe in Munich is introducing the compressible Soft-PGS thermal interface material (TIM) for electronics cooling and thermal-management in extremely thin spaces — particularly for power electronics devices. Soft-PGS enhances the thermal coupling between heat-producing devices (heat sources) and heat-dissipation devices (heat sinks). The Soft-PGS is a 200-micron thick graphite sheet designed as a thermal interface material for insulated-gate bipolar transistor (IGBT) modules.
As Soft-PGS can be compressed by 40 percent it is a solution for reducing thermal resistance between a heat sink and an IGBT module. The 200-micron thick Soft-PGS sheet is easy to install, and has far lower labor and installation costs than thermal grease or phase change material, Panasonic officials say. Soft-PGS guarantees thermo stability to 400 degrees Celsius and high reliability against intense heat cycles from -55 C to 150 C. Its thermal conductivity is guaranteed at 400 Watts per meter-Kelvin for X-Y direction and at 30 Watts per meter-Kelvin in Z direction.
Annealed pyrolytic graphite, or APG
Annealed pyrolytic graphite, or APG, encapsulated within a structural shell made from traditional materials such as aluminum, copper, beryllium, ceramics or composites is another promising approach. Encapsulated APG was first used operationally in high-flying DoD aircraft, where its lightweight characteristics earned it early acceptance in applications where each pound saved could be transformed into another pound of fuel or additional avionics. The low mass of encapsulated APG based solutions is still a key factor in reliable cooling solutions for remote electronics and navigational avionics, writes Mark J. Montesano, VP of Engineering and Technology, Thermacore, k Technology Division.
Encapsulated APG offers additional thermal advantages that go beyond light weight, and apply to many military systems. The most fundamental advantage is high conductivity at low mass. Encapsulated APG material offers three times the conductivity (k) of copper with a mass less than aluminum. This results in a significant improvement in conductivity for any encapsulant paired with APG.
Encapsulated APG’s high conductivity, combined with its low mass density, results in a material system with outstanding performance per pound, or specific conductivity (W/m•K/g/cm3). The specific conductivity of encapsulated APG materials range from 4- to 10- times that of traditional thermal management materials. For example a copper encapsulated APG heatsink with an 80% APG volume fraction would have approximately eight times the specific conductivity of copper alone.
Another benefit of encapsulated APG is that the coefficient of thermal expansion (CTE) offered by this solution can be tailored to specific application needs by altering the choice or configuration of the encapsulant. CTE can also be matched to a specific application, allowing dissipation of dramatically increased heat fluxes by permitting direct attachment, thereby minimizing thermal resistance.
By combining the high thermal conductivity of APG with an easily-tailored CTE encapsulation material, engineers can create solutions for high-powered military electronics while keeping weight and footprint under control. Designers can choose the encapsulant that most closely matches the CTE of electronic materials such as silicon and gallium arsenide, allowing the direct attachment of these devices and providing the thermal benefits of both APG and the encapsulation material.
Encapsulated APG also offers simple integration into current and planned systems. Because the APG is hermetically sealed within the encapsulating material, it is compatible with standard finishing and processing manufacturing steps as well as with the encapsulation materials themselves. These encapsulated APG solutions, with no moving parts, give thermal engineers greater design flexibility, more durability, and less maintenance concerns.
All of these advantages make encapsulated APG an ideal material for military applications, enabling the technology that satisfies today’s needs for high-density packing requirements in a limited space. Thermal technologies based on encapsulated APG have proven to perform well under demanding temperature, stress, load, vibration and other conditions as protection for avionics, target acquisition, imaging and other systems in mission-critical applications onboard fighter aircraft (such as the F-16, F-22 and F-35 Joint Strike Fighter) and helicopters. Encapsulated APG-based solutions help sensitive electronics continue to function in temperatures down to -70° C and in 9g load conditions.
The properties of encapsulated APG, at work in so many military applications today, are also opening up new possibilities for the future. One example is flexible thermal links for aircraft, integrating APG with a flexible heat pipe to cool target acquisition sensors while isolating them from the aircraft’s vibration. The flexibility of APG and the strength of the encapsulation material combine to provide a thermal solution with mission-critical reliability, writes Mark J. Montesano, VP of Engineering and Technology, Thermacore, k Technology Division.
New metamaterial enhances natural cooling without power input
A team at the University of Colorado Boulder (CU-Boulder) in the US developed a new metamaterial film out of glass microspheres, polymer and silver, that provides cooling without needing a power input. Radiative cooling is the natural process through which objects shed heat in the form of infrared radiation. All materials at room temperature emit infrared at wavelengths of 5–15 μm. However, the process is not typically very efficient because it is counteracted by external influences that heat the object, such as sunlight and air currents. Air, meanwhile, absorbs and emits very little radiation with wavelengths 8–13 μm. The Earth cools itself at night by emitting infrared through this “atmospheric window” and into space.
While night-time radiative cooling materials, including a pigment paint, have been successfully developed, a daytime version has proved challenging. The problem is that the materials absorb sunlight, which quickly exceeds the cooling power and instead heats the surface. So the challenge for the CU-Boulder researchers was to create a material that both reflects sunlight and also allows infrared emission.
They created a thin, flexible material with two layers; a sheet of polymer polymethyl pentene containing randomly dispersed silicon-dioxide (SiO2) glass microspheres 8 μm in diameter and a 200 nm-thick silver coating. The combination of the two layers is only 50 μm thick. The polymer-microsphere film is transparent to the whole solar spectrum but radiates infrared. The broad collective resonance among the microspheres ensures the film is highly emissive of infrared within the atmospheric range of 8–13 μm. This property therefore enhances the naturally occurring radiative cooling. Meanwhile, sunlight travels through the metamaterial and is reflected back by the silver coating, which prevents any solar heating.
Researchers also developed low cost production method for the material. “The key innovation of this work is to produce the designed material at scale using the roll-to-roll process,” explains Yang. The researchers used a roll-to-roll extruder to distribute the microspheres in the polymer and a roll-to-roll sputtering machine to apply the silver coating. This means they are able to produce large amounts of the material in mere minutes. “When produced at scale, we estimate that the material cost is only $0.50 per m2 (yes, 50 cents per square metre), since it can be produced at 100 square metres per minute,” adds Yang.
Field tests in Boulder, Colorado and Cave Creek, Arizona, revealed that the film’s average cooling power was more than 110 W/m2 over 72 hours. Even in the midday Sun, its average was 93 W/m2. This is roughly equivalent to the electricity generated by a typical solar panel of the same area. The glass-polymer sheet has many potential cooling applications. By applying it to a solar-panel’s surface, the film could not only cool the panel but also recover an additional one or two per cent of solar efficiency, because overheating hampers the ability to convert solar energy. “That makes a big difference at scale,” says Xiaobo Yin, another researcher on the project.
Thermal Interface Materials for 5G
5G promises incredible download rates and extremely low latency communication. The first 5G smartphones came to the market in 2019, but the market has expanded rapidly in 2020. Early 5G phones were commonly reported to overheat rapidly, especially in warmer climates when using mmWave, dropping to the use of 4G to keep temperatures down. Material utilization around the mmWave antenna also reveals challenges with signal propagation. This presents an opportunity for materials suppliers to address these challenges. The key markets will be for thermal interface materials (TIMs), heat spreaders and thermal insulation materials. Recent years have seen an increasing application of vapor chambers within smartphones to improve heat spreading. However, their future is far from set, with several high-end models still using graphite heat spreaders for their reduced complexity, cost and weight. For example in 2020, Samsung, who have previously hyped vapor chambers, have used a graphite heat spreader or a copper vapor chamber in the Note 20 interchangeably. Additionally for 2020, Apple’s first 5G phones, the iPhone 12 lineup, all use graphite heat spreaders and have not adopted vapor chambers.
Several new thermal materials for 5G applications were released in 2020. For TIMs, DOW introduced the DOWSIL TC-3065 Thermal Gel with a thermal conductivity of 6.5 W/mK and bondline thicknesses down to 150 microns, specifying applications in optical transceivers, solid-state disks and other network devices. Henkel also announced their portfolio of TIMs for 5G infrastructure, including the BERGQUIST LIQUI-FORM TLF 6000HG gel-type TIM with 6.0 W/mK thermal conductivity and their BERGQUIST GAP PAD TGP 10000ULM with a 10 W/mK thermal conductivity and plans for a 12 W/mK version. Another significant material release in 2020 was the announcement of W.L. Gore’s Thermal Insulation material for smartphones, this material has a thermal conductivity lower than air, helping reduce hot spots on the device surface, but is also compatible with the new mmWave 5G antenna that can struggle with signal propagation
Thermal Management Solutions
In an interview with EE Times, Michael Mo, chief executive officer at Kulr Technology Group, highlighted how the company’s carbon-fiber technology designed with NASA to regulate the extreme temperatures of sensitive components in space for the Perseverance mission, will be employed by Drako Motors for a new electric supercar. With a 1,200-horsepower architecture designed, Drako GTE is an EV platform that highlights the difficulties of thermal management and thus the importance of new solutions that can improve performance.
Kulr Technology Group is developing, manufacturing, and licensing carbon fiber thermal technologies for batteries and other electronic devices for space to keep them cool. Its thermal management solution used on the Mars mission will enable the next electric luxury sports cars. Kulr is using phase change material with vertically aligned carbon fibre (carbon fiber thermal interface, or FTI) for electronics and lithium-ion batteries to serve the world of electric transportation, energy storage, battery safety, 5G infrastructure, cloud computing, and aerospace and defense applications.
Carbon fiber can dissipate heat while reducing size, weight, and manufacturing complexity. Kulr has developed a proprietary manufacturing technology that organizes 5 to 10-micron carbon fiber strands onto a base material in a way that looks and feels like black velvet. With the ability to produce 1,800 continuous amps and 2,200 peak amps, the battery in Drako GTE is designed to offer megawatt-order power output and cooling capacity to withstand track-level sports performance on various world circuits.
Mo pointed out that producing an electric supercar needs to involve extreme power, and by maintaining limited space for heat sinks, the thermal interface has its importance. Bringing the technology used in space environment with high temperatures, the electric transport could support more power thus ensuring proper dissipation and avoiding overheating. “But we have some challenges to solve: the biggest thing that the consumer world is looking for is the price to be very cost-effective, and high thermal conductivity performance,” said Mo.
Mo explained how the FTI solutions family specifically includes Alcor and Mizar FTI materials. “The ALCOR has a density of < 0.7 g/cm^3, and very low contact pressure to achieve low thermal impedance. The MIZAR FTI increases power densities of a board layout and relieves mechanical stress — resulting in an overall increase in thermal stability and reliability,” added Michael Mo.
ARA is another solution from Kulr aimed at solving thermal management problems in the aerospace and defense industry, as it has a thermal capability that has experimentally proven effective over a small temperature range. It finds use in systems with a large amount of computing power in short time intervals. Michael Mo said they developed a proprietary high thermal conductivity fiber core material to deliver a good performance required by space.
HYDRA is another solution that acts as a heat sink for lithium-ion batteries and prevents the thermal runaway propagation (TRP): an important parameter in electric vehicles . A short circuit in a battery pack can cause thermal runaway and, therefore, the ignition of fire and combustion of materials such as to raise the temperature of neighboring cells. Rising temperatures increase the possibility of shorting adjacent cells. “Hydra aims to prevent the temperatures of neighboring cells from rising above 100 °C and thus prevent thermal runaway,” said Mo.
Typically, a thermal runaway is caused by excessive current or a high ambient temperature and develops through several stages: starting at a temperature of about 90-100 °C, the heat generated causes organic solvents to rupture, resulting in the release of gas, increasing the pressure inside the cells. Despite this, the gas does not ignite due to the lack of oxygen. If, however, the temperature continues to rise, exceeding 135 °C, the separator melts and causes a short circuit between the anode and cathode, leading to the rupture of the metal oxide cathode at 200 °C and releasing oxygen. This allows the electrolyte and hydrogen gas to burn. As part of battery testing, Kulr developed the LYRA internal short circuit (ISC) trigger cell to identify a cell’s failure conditions to study the failure modes and safety issues that could arise within battery packs.
Example Performance of the HYDRA TRS (Source: Kulr).
Thermal Management materials market
We’re seeing changes in the world of power electronics with the automotive industry moving to vehicle electrification and the advent of 5G communications technologies that will accelerate the growth of cloud computing. These applications require more power and also thermal management solutions or cooling technologies for batteries and other powertrain systems.
Electronic thermal management materials are widely used in varied end user segments including consumer electronics, automotive, aerospace, healthcare and telecom among others. These materials form a basic part of modern-day electronics as it aids in maintaining temperature within the electronic assembly.
The electronic thermal management materials market is widely driven by the growing penetration of electronics devices across various end user industries such as automotive and healthcare among others. Moreover, the growing demand for electronics mainly in the developing region shall further generate substantial revenue to the overall market during the review period. The market includes various products such as gap fillers, tapes, thermal gels and thermal greases. These products can be used interchangeably in various applications. However, the choice of ETMM mostly depends on the thermal resistance, dielectric properties, structural strength and also on the cost of the material. For instance, gap filler are widely employed in electronics, whereas greases are extensively used for automotive applications.
The rapid advancement in manufacturing process of various electronics assemblies such as chip density and number of transistors incorporated shall augment the requirement for high performing cost-effective thermal solutions in the coming years. However, high product prices of thermal management material prices is projected to be a major downside to the market growth. Electronic thermal management material prices are high and ranges between USD 35 to 40/kg. Additionally, high product prices limit its usage in the electronic equipment due to the price sensitive nature of the market, especially consumer electronic which is the major product consumer.
Conductive paste was the most revenue generating product in the overall electronic thermal management materials market in 2018. These pastes help in reducing the dependency on screws and clips in electronic devices, thereby providing with lightweight consumer electronics. The consumer electronics manufacturers are constantly trying to reduce the weight of their produce hence are shifting towards the use of conductive pastes.
Gap fillers help in eliminating air gaps between heat sink and other electrical components. These fillers offer an effective combination of thermal performance with an efficient mechanical shock resistance. Phase change materials (PCM) are mostly employed in high power electronics due to their excellent chemical stability and high latent heat. However, their low thermal conductivity compared to other electronic thermal management products is a major limitation of the product.
Electronic thermal management material are widely used in the consumer electronics sector. The need for effective thermal management and heat dissipation from electronic devices from computers to LED lighting have become pivotal for their reliability and performance. Moreover, with the diminishing size of electronics efficient thermal stability within the electronic assembly is becoming an area of utmost importance in the recent times. Consumer electronics held an electronic thermal management materials market share of close to 35% in 2018.
ETMM products are also extensively used in the automotive and telecommunication sector. Gap pads, thermal greases, and phase change materials are used in automotive engine, transmission controls and on-board electronics. Telecommunication equipment manufacturers to ensure reliability and long life hugely depends on thermal interface materials. ETMM are mainly used in switches, optical fiber cables, transmitters and receivers among others in the telecom industry.
ETMM materials in the Asia Pacific region has gain wide popularity in the recent times. The presence of major electronics manufacturers in the region is positively contribution to the ETMM demand. Moreover, encouraging government schemes especially in India such as ‘Digital India’ and 100% FDI has surged electronic manufacturing in turn propelling the demand for thermal management materials. Europe and North America are other major revenue generating regions. The presence of large manufacturing infrastructure coupled with the increasing demand for electronics shall contribute to the electronic thermal management materials market growth.
Some of the key players include 3M, Parker Chomerics, Boyd, European Thermodynamics, Dr Dietrich Muller Gmbh, Wacker AG, Darcoid company, Laird PLC, Lord Corporation, Amerasia International (AI) Technology Inc, Henkel AG & Company, Marian Inc, Honeywell International Inc and Dupont.
References and Resources also include:
Basics of Thermal Management Materials for Microelectronics – theory and practise, Dr. Philip Blazdell , General Manager, t-Global Technology Unit 1-2 Cosford Business Park, Lutterworth, UK, pblazdell@tglobaltechnology.com
