20 June 2016
Cleaning is an important consideration for many critical applications, to ensure optimum performance. Control Engineering Europe reports.
Cleaning is an integral part of many manufacturing and maintenance processes and is often also critical to the continuing performance of a range of technologies. In many industry sectors, including such as semiconductor production, defense, microelectromechanical systems (MEMS), and biotech, an effective and efficient cleaning process is of critical importance to the performance of equipment and systems.
‘Cleaning’ in the process industry and in research laboratories refers to the use of agents such as solvents, acids or bases to remove unwanted particulates and contaminates from products such as optics, semiconductors and electronic devices. Cleaning can be an automated process on the finished product or can entail the surface preparation of a material prior to a manufacturing process.
Many applications will benefit from a secondary evaluation of the cleaning parameters or processes detailed in a request for proposal (RFP). “The specifiers will be aware of the importance of cleaning their products,” said Louise Bertagnolli, president of JST Manufacturing, a wet processing and precision cleaning equipment company. “However, they may not realise that cleaning technologies have become so sophisticated that it is usually possible to improve on the initial design of a cleaning tool or process, making it more efficient, cost-effective and robust.”
Bertagnolli goes on to explain that cleaning system specialists will have a broader view and experience of all the tools and technologies available, as well as the expertise needed to select and integrate them, so it can be beneficial to work with a cleaning specialist with an applications laboratory that is equipped to test a variety of cleaning systems. “Having the equipment required for this kind of facility is indicative of the commitment of the cleaning system specialist,” said Bertagnolli. “A facility capable of performing demonstrations will have specialised metrology equipment such as a scanning electron microscope and laser-based surface particle measurement systems in a state-of-the-art cleanroom.”
One cleaning application undertaken by JST Manufacturing is the design of a specialised cleaning tool for the US-based National Ignition Facility (NIF) which is based at Lawrence Livermore National Laboratories.
NIF, the world's highest-energy laser system that consists of 192 laser beams which will focus nearly two million joules of energy and create temperatures and pressures that exist in the cores of stars and giant planets. NIF is also a cornerstone of the National Nuclear Security Administration's effort to maintain the United States’ nuclear deterrent without nuclear testing. Other NIF missions include finding new sources of pollution-free energy, and studying physics and other sciences.
Each of the 192 beams are supported by an array of optics – up to 50 lenses for each beam – depending on the type of experiment being performed. Ensuring that these optics remain clean is crucial to the success of the various types of laser-based experiments.
“If the lenses were not clean then the performance of our laser would start to degrade,” explained Patrick Williams, NIF optics maintenance manager. “The cleanliness of the optics is crucial to our ability to produce maximum fluency (energy in joules) that is required to perform many tests.”
Transporting the chemistry
To maintain the large inventory of its optics, LLNL partnered with JST Manufacturing in the development of a suitable cleaning tool. “The optics are heavy and large, so we don’t want to handle them a lot,” said Williams. “So, after we developed an RFP and showed it to JST, the company suggested that there might be an easier and more cost-effective way to transport, clean and inspect the optics.” One of the innovations in the NIF cleaning tool, which was a tank-like configuration, was to eliminate the need to move the optics to wash, rinse and drying them.
The engineers suggested that rather than transport the heavy optics for cleaning, it would be simpler to transport the chemistry (solutions) to the optics in a fixed location. “We also designed a sling-like device to hold the optics. This also let technicians rotate them during the inspection process,” said Bertagnolli.
To date JST has built two cleaning tools for NIF. The first tool was used for the very beginning of the facility. “A second tool was built to provide us with dual capacity,” explained Williams. Because NIF has become a production facility, where many scientists and companies are performing research, we also wanted to be able to clean a higher volume of optics and also get away from single-point failure.”
Precision process cleaning
In some instances cleaning is an adjunct of the manufacturing process. JST Manufacturing, for example, has been involved with designing cleaning systems and etching systems for the production of crystals used in aerospace guidance systems.
“Etching involved the precision removal of material from a component, which is a form of cleaning just like the removal of unwanted material from the surface of an object, whether it’s particulate debris, corrosion or contaminants, or a layer of material,” said Bertagnolli.
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