New techniques in high vacuum at Edwards

What can be new or impressive about a vacuum? You might say nothing: but Nick Denbow learned a lot more about making a vacuum in a visit to Edwards in Burgess Hill, and reported on 5 June 2008 as follows.

Creating nothing has never needed more technology, innovation and R+D.

Over 30% of the Edwards vacuum pump sales are from new designs, each year, so this is a business that is moving forward constantly, and as a result leads the world in many areas of vacuum pumping and processing.

Edwards, now an independent company, employs 3600 people at plants in Crawley, Burgess Hill, Shoreham and Burnley in the UK, plus other R+D and manufacturing facilities in Korea, Czechoslovakia, Japan, China and Mexico.

Sales in 2007 were around USD 1Bn, spread worldwide, with a bias into Asia, but the end products that rely on Edwards technology are then shipped worldwide.

This is because the vacuums that Edwards create enable the manufacture of semiconductors, solar panels, flat panel displays, biofuels and LEDs – the list of modern devices and developments dependent on vacuum pumps goes on.

Edwards had the right technology and the larger sized pump capability to be able to provide the pumps suddenly needed for the boom in solar panel and TV flat panel display production, and also the foresight to build new production plants and support facilities for these units alongside the new manufacturing companies established in Korea and Japan.

Both rely on the deposition of different chemical layers on glass or similar panels under vacuum, and this was just the application serviced by Edwards for the semiconductor industry: despite the rapid growth of these new industries, semiconductor production still represents the largest end-user industry for Edwards.

A recent visit to their plant in Burgess Hill showed off the production of aluminium pumps, both dry scroll and turbomolecular pumps, which are supplied to many OEMs for use on scientific and process analytical instruments and applications.

With no bearings, lubrication or grease in the vacuum space, and no shaft seals to wear, dry scroll pumps have largely eliminated the maintenance attention that was previously always necessary on vacuum systems: the spiral seal in a modern scroll pump might need consideration for replacement only after 12 months or more.

Operating for around 10 years, the plant at Burgess Hill was established purely for the precision machining of these aluminium units, and is an accurately temperature controlled environment: the orbital eccentric movement of the two scrolls (spirals) – within one another, achieving a rolling seal along the scroll face to extract the gas – requires a manufacturing tolerance of around 14 microns for the scroll spiral.

Similar, or better, precision is required on the turbomolecular pumps: these are often used on mass spectrometers, cyclotrons or electron microscopes – equipment where any noise and vibration cannot be tolerated.

Each multi-stage turbine unit, machined from a single billet, is individually balanced to eliminate vibration, and typically rotates at up to 90,000rpm in a stable (vertical axis) position – peak to peak vibration is quoted at below 0.02 micron: a 24 hour final running test is needed to avoid any stress relief type changes in the rotor.

A recent release from Edwards describes their latest turbomolecular unit, the STP iX2205 pump, again focussed on glass coating machines and solar cells (http://www.processingtalk.com/news/bce/bce132.html).

This new unit release demonstrates one of the major factors that have driven the Edwards new designs and developments over the years: the new unit is much more compact and smaller than previous units, and has a maintenance interval that can extend to five years.

The Edwards business is in pulling the gases from processing areas, to enable manufacturing functions: but these manufacturing functions themselves involve various corrosive or hazardous chemicals.

While Edwards provide vacuum pumps with various corrosion resistant coatings to avoid damage from the chemicals, they have developed their business into neutralising and eliminating these vapours, in equipment known as abatement systems.

Perhaps typical in illustrating their specialisation and experience, some of the etching processes result in the extraction of fluorine gas: in the abatement, or thermal conditioning system, this is burnt in a methane flame, to produce hydrofluoric acid, which is then absorbed on crystals to produce calcium fluoride.

The Edwards abatement units are effectively treating the effluent from the plant, replacing the conventional chemical processing normally provided (See for example http://www.processingtalk.com/news/bce/bce133.html).

An interesting side effect of this extension to their vacuum pump business activity is that instead of their production output being a major user of power and therefore contributing a large carbon use footprint to the World, the Edwards abatement products now eliminate so many ‘greenhouse gas’ type effluents, that this totally outweighs their use of carbon in the lifetime powering the pumps, and makes the overall Edwards product World footprint into a positive contribution, reducing greenhouse gas effects.

Another similar aspect of their businesses profile is that the overall yearly production output of solar panels in Japan can provide the power output equivalent to a new nuclear power station, every year!

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