Clean as can be

Chris Reed, operations director of InteliCoat Technologies, gives an insight into precision coating in a cleanroom environment

Cleanrooms are work areas in which the air quality, temperature and humidity are highly regulated in order to protect sensitive equipment and processes from contamination. At InteliCoat they are used in the coating, laminating and converting of flexible materials during the manufacturing of precision coated papers, films, and speciality substrates for imaging, electronics, medical, and optically clear applications.

Maintenance of a cleanroom environment for precision coating is integral to the business and an important part of the company’s ethos of total quality management, as opposed to just a list of specialized procedures and equipment. This approach extends throughout the manufacturing process, from receipt of raw materials, through to mix processing, slitting and packaging. For successful cleanroom coating and converting, it is essential that all team members fully appreciate the final application of the material to be coated, in order to deliver products of the highest standard.

Air quality

Cleanrooms are rated as Class 10,000 where there are no more than 10,000 particles larger than 0.5 micron in any given cubic foot of air, and Class 1000 where there are no more than 1,000 particles. InteliCoat has an air quality standard of Class 10,000 in the coating room and Class 1,000 at the coating head. This can only be achieved through the careful design of air supply systems and operating practices when creating an enclosed cleanroom within a production environment. Such measures are essential at the planning stage of constructing a cleanroom facility, to be able to demonstrate compliance with customer needs for process and product cleanliness.

Establishing a low throughput of air is key to successfully maintaining cleanroom conditions, helping to keep all surfaces clean and minimize the risk of contamination. Air supplied to the coating room is filtered through a sequence of panel filters, bag filters and high temperature stainless steel HEPA (High Efficiency Particulate Air) filters. The drying ovens use air supplied through different filters and separate from the main room for optimal air cleanliness. Although the system is robust, its effectiveness is also dependent on a functioning preventative maintenance routine.

Using this type of operational schedule, air filters are routinely checked for a high pressure differential and visually inspected every three months. Under normal conditions, HEPA filters have a relatively long life and do not require changing more than once a year. Coating room air quality is monitored on a weekly basis using a standard particle counter procedure, and the results are displayed in the machine shift reports, which indicate if the filters need changing.

Regularly monitored by pressure gauge reading, positive air pressure is required to ensure a higher pressure is maintained inside the cleanroom, preventing any contaminated air from being drawn in. It is important to employ strict entry protocols for personnel and materials. Special protective clothing must be worn that does not shed lint particles and prevents human skin and hair particles from entering the room's atmosphere. Tacky floor mats are used at pedestrian entry points to ensure dirt is removed from shoes. Only clean materials must enter the cleanroom environment, as palletized supplier material runs the risk of introducing board fibres and dust.

It is important to work closely with suppliers to ensure raw materials received are at the required cleanliness levels, before passing through the air showered controlled materials entry/exit point.

Active and passive anti static devices fitted to the coating machine for safety reasons can further help cleanroom processing of materials. By eliminating or significantly reducing electrostatic charging of the web as it passes through the coater, the risk of debris being attracted onto the product is reduced significantly.

Companies planning to perform cleanroom manufacturing need to be well prepared for the capital investment required to convert open plan processing systems into segregated and enclosed sections within the plant. For the associated procedures required for materials handling, clothing upkeep, cleaning protocols, entry/exit procedures, quality and process control measures must be implemented from the start to ensure product quality and consistency, ideally as part of certification to ISO 9001:2000 standard.

Under the ISO 9001:2000 guidelines, manufacturers are responsible for the design of their own processes and internal standards, extending through to planning, setting of objectives, and management of all quality systems. Measurement, collection and analysis of quality data are also tightly regulated. Such a process led approach to quality management systems helps to fine tune the customer focus in all operations by placing greater emphasis on the monitoring of customer feedback and measurement of customer satisfaction. Process improvement measures are also addressed through preventative action and review processes.

Measurement and improvement of customer satisfaction received much emphasis in the 2000 update of the ISO guidelines. It is sometimes not easy to measure until business is lost. As well as keeping constant vigilance through the measurement of parameters such as delivery performance and customer returns, regular formal customer surveys should also be performed. For specialist manufacturers, such tight control is simply the way of doing business. Six sigma is an additional tool available which can provide a valuable platform for maintaining quality and driving down costs.

The cleanroom environment is an essential part of manufacturing at InteliCoat. Many of the product ranges, such as optically clear films, have extremely high visual quality requirements. These are used in applications such as membrane touch switches, window films and graphic overlay films, where even very small contaminants may render the end product useless. The production of medical component films, which ultimately end up in medical devices, requires extremely high levels of cleanliness, and so is critically dependent on the elimination of any contaminants from the coating environment.

“InteliCoat has been at the forefront of cleanroom coating for over 20 years and the equipment and working practices are built into the way the whole business operates”, states Dave Williams, 63in coater team leader. “Our operators have, collectively, decades of expertise resulting in a cleanroom methodology which is second nature and at the same time meets the most rigorous industry guidelines.”