Focus No.5

"RFI Shielding Limited has become focused on providing technically innovative custom solutions to global markets where rapid change is commonplace" says RFI's Commercial Director and General Manager Philip Mizen, "we are currently negotiating joint ventures and alliances with strategically located organisations to extend our strong customer base".

RFI Shielding Limited is part of the Derbyshire based Cirqual plc group of companies, and is Europe's leading manufacturer of EMC shielding materials. Founded in London in 1978 by the Unitech group, RFI moved to its current Braintree location two years later. With the sale of Unitech to Siebe plc in May 1996 and the subsequent restructuring of their core businesses, RFI was purchased for œ9 Million in April 1997 by Cirqual, as part of the development of their specialist-engineering group.

RFI's original markets were specifically the defence and aerospace industries, but as awareness of EMC increased and regulatory controls ensued, many more new and interesting market opportunities arose. This has become apparent in the way RFI's product portfolio and operational practices have developed, and is reflective of the need to listen to customers' requirements and provide complete shielding solutions to specific application problems, rather than simply providing a range of shielding components.

Cellular telephone components complete with Xyshield ® gaskets

"To this end, RFI Shielding Limited has become focused on providing technically innovative custom solutions to global markets where rapid change is commonplace", says RFI's Commercial Director and General Manager Philip Mizen, "we are currently negotiating joint ventures and alliances with strategically located organisations to extend our strong customer base".

Together with this focus has come the rapid growth of the company, from 44 employees in January '95 to a current number of 92 which includes part-time and temporary staff, and an increasing turnover exceeding œ5 Million per annum. According to Philip Mizen, "The rapid growth within RFI has been mainly due to the development and introduction of our Xyshield® product range, complemented by the steady growth of our more traditional products".

The Xyshield® product range was developed in conjunction with the cellular handset manufacturer Orbitel, now an integral part of Ericsson Telecommunications. During the design cycle of a currently available cellular telephone, Orbitel's Basingstoke based design engineers discovered that existing gasket technology would not be suitable for current and future product designs, due to both performance considerations and the need to engineer out assembly costs. Having approached RFI to discuss their requirements, they jointly identified the need for a combined small cross-section electromagnetic and environmental seal for high volume applications. Working closely with RFI's Materials and Process Specialists, a 'Form-in-Place' gasket was produced using prototype-dispensing equipment designed and constructed 'in-house'.

The results obtained from these early trials led to a full development programme for both the electrically conductive silicone elastomers, and the high precision fluid dispensing techniques required to successfully apply such a product. Xyshield® has evolved into a 'Form-in-Place' gasket, which can be applied to small and intricate electronic enclosures where more traditional shielding materials would be impossible to use, especially in mass production. The material itself has been formulated in such a way that it is a single component silicone elastomer, filled with electrically conductive particles. Its primary function is to provide a low impedance flexible connection between two conductive surfaces, but will also provide suitable environmental protection when correct provision is made in the application's design. Xyshield® has been specifically designed for application in fluid form, directly onto the component that is to be shielded, and is a material with thixotropic properties (the gasket bead will not slump or flow after dispensing ensuring a consistent gasket cross-section). The material is mixed in a dedicated clean environment, where stringent formulation procedures are followed. Each batch is tested for viscosity, hardness, conductivity, and adhesion, ensuring batch consistency, repeatable flow characteristics, and guaranteeing product quality. Xyshield® cures by reacting with water vapour in the air, and is achieved in a dust free, humidity and temperature controlled environment. This advantageous curing mechanism was part of the initial material formulation, which specified that no corrosive/toxic fumes or vapours are evolved as a by-product of curing during normal processing. Due to this property it is suitable for use on, or close to, sensitive electronic components or substrates, and is hazard free for process operators.

Running in parallel with the material formulation, has been the RFI's development of the dispensing technology. With the requirement to move away from small batch quantities and move towards high volume processing, new and improved techniques were necessary to maximise the materials potential. Sophisticated production equipment dispenses the material onto components via multiple syringes, mounted on 3 axis CNC tables with an accuracy of 25 microns/500mm (approximately one third of the diameter of a human hair). The dispense heads follow a pre-programmed path, consistent with the geometry of the component part, ensuring an optimum level of precision and control over the flow of the gasket bead. Each head has X,Y, and Z axis micrometer adjustment, ensuring close tolerances can be maintained, and the component parts are positively located by vacuum in machined location jigs for consistent and repeatable positioning during application. Process Quality Controls have also been designed into the manufacturing cycle; process capability is continually measured using video edge detection equipment, linked to SPC (Statistical Process Control) software. This non-contact method of measuring the critical dimensions of a dispensed gasket, means that uncured parts may be monitored and the manufacturing process maintained within pre-defined limits.

RFI's commitment to continual improvement has recently been highlighted by two key Xyshield® related events:

• First, the release of XY300, the next generation of 'Form-in-Place' materials. After extensive research and testing, a new material was released into production as a direct result of a customer's specific requirement. XY300 has delivered several enhanced characteristics when compared with other 'Form-in-Place' materials, including:
  Lower Volume Resistivity through a much wider deflection range - 10-60% compression;
  
  Greater Working Deflection Range to accommodate greater tolerances on mating surfaces;
  
  Very Low Resistance Contact achieved with minimal deflection/pressure;
  
  Improved Compatibility with a Wider Range of Substrates, including materials subject to forming resistive oxide layers;
  
  Excellent Long Term Ageing Characteristics.
  
  Second, the trebling in size of the Xyshield® production facility floor area. This coincides with the formation of a dedicated research and technical department to co-ordinate 'Form-in-Place' technology research activities. The facility provides staff with all the equipment necessary, such as an environmental test chamber (to test product and prototype performance), to keep RFI at the very front in this exciting market.

RFI Shielding Limited is not only applying its efforts to 'Form-in-Place' technology, especially as there continues to be steady growth in its more traditional product areas. A concerted effort is being made in the reformulation of the Supershield range of conductive silicone elastomers, to enhance both processing and performance criteria. Supershield has historically been produced in a wide range of cross-sectional extruded profiles, compression moulded to meet customers specific designs exactly, or die cut from sheet material. However, as a direct result of this work, RFI will imminently have the ability to injection mould conductive silicone elastomer gaskets. In the first round of reformulations, S800 (silver plated copper in silicone), S600 (silver plated glass in silicone), and S400 (nickel particles in silicone) have been targeted. During the course of this project, further interesting areas for future new development have been identified.

The current high levels of orders in one of RFI's longest running product ranges, knitted mesh products, is being capably tackled by what is considered to be one of Europe's most modern and efficient facilities. Significant investment and foresight in providing high speed, fast set up, low maintenance, interchangeable head, automatic dieing, knitting machines, has given RFI the capacity any capability to respond quickly to both small and large run quantities in virtually any mesh cross-section. Although some of the applications using knitted mesh have changed since it was first introduced, it has proved itself to be a very durable and effective range of products.

Philip Mizen continued "In our ambitions to be a global provider of EMC shielding solutions we will actively construct a framework with which to support and supply information to our world-wide distributors and partners". RFI has already started building this framework using an Internet web site, which has been 'live' for about three months. "It has already proved extremely useful as part of a co-ordinated overseas promotion programme, with our representatives using it as another tool with which to both promote and access us". However just as important are the people that are finding RFI for themselves, "The number of contacts made directly to us has been excellent, providing not only the possibility of future custom, but also valuable intelligence on many markets yet to be positively addressed by our Marketing and Sales team".

RFI Shielding Limited's web site can be found on the Internet at: http://www.rfi-shielding.com and their Technical Sales Team can be contacted by Email at: sales.enq@rfi-shielding.com

In conclusion Philip Mizen added, "RFI is fast approaching its twentieth anniversary which gives us some cause to celebrate and be proud of our past achievements. As we look towards the future we know we are entering a very challenging phase, but we believe we have the right blend of people and a very strong product base to take forward and realise our ambitions".