Three decades of keeping it clean

| Cleanrooms and Contamination Control

Disk drive manufacturing

Jonathan Newell travelled to Winchester to meet former colleague Dick Gibbons to discuss how the cleanroom industry has changed in the last three decades and what the future holds.

The large class 100 ballroom sized cleanroom for the Winchester disk manufacturing line at IBM’s Havant plant in Hampshire was crammed with technology that would still make an impression today. Thirty-two years have gone by since I stepped into that cleanroom as an undergraduate trainee with my mentor, Dick Gibbons, who was then the company’s expert in cleanroom technology and contamination control.

Gibbons continued with his involvement in this field and is still active today in the development of cleanroom standards for the ISO. He agreed to meet me in Winchester, a short drive from IBM’s Hursley Park, the birthplace of Winchester disk technology, and discuss how things have moved on since the 80s.

JN: We couldn’t have imagined at that time that our cutting edge 14-inch disk drive with a capacity of 400Mb would eventually look antiquated by current technology. Have cleanrooms moved on at the same speed?

DG: Disks have progressed a lot, fly heights of the read/write heads are lower and are almost touching on the latest Seagate drives. They use MR (Magnetoresistive) heads now which present different protection requirements, they’re much more susceptible to corrosion. For the disk drives we worked on, we had a class 100 cleanroom but the requirements are more stringent now, so class 10 is the norm.

JN: What changes have we typically seen in the way cleanrooms are designed and operated?

DG: The cleaning process and the types of contaminant that have to be controlled have changed. At that time, we used fluorocarbon solvent cleaners, but they were very bad for the environment. I was part of a project to eliminate their use and we managed to cut the consumption from 300 tonnes a year to zero. All cleaning is now required to be done without solvents and so a different approach is needed which involves water and surfactants.

Also at that time, we were mostly concerned with particulate contamination – and indeed cleanroom standards are based on this – but for disk drive manufacturing, other contaminants, particularly organics and ionics, are of major concern and have to be eliminated to prevent corrosion and stiction, the term used to describe when the head sticks to the disk after a period of not being used.

JN: I remember these were issues at Havant, some people had “rusty fingers” as you referred to them as I recall.

DG: Yes that’s right. As disk drive technology progressed, it became much less tolerant to the presence of organic and ionic contaminants. Perspiration could leach through the gloves and contaminate an item causing “rusty” patches to appear. So now contamination is viewed not only as particulate but also as chemical. Food, drink, makeup and sweat all contribute to unacceptable quality in such precise manufacturing environments. Plastics outgas, latex produces organic contaminants, they’re all good lessons already well learnt.

JN: Didn’t you have zero tolerance to anything magnetic in the cleanroom as well?

DG: Definitely. Our sister plant in America had to close down because of magnetic contamination. Even the finest magnetic dust fragment in the air can scrap a disk drive. The problem is that if it gets into the disk enclosure, it will eventually work its way to the read/write head and it will wipe the data from the disk. It’s progressive so it might not destroy all the data until it’s been operating in a customer’s computer for a month or two. Magnetic material is a very dangerous contaminant in disk drive manufacturing.

JN: Tell me about the “Greener Cleanroom” concept

DG: Cleanrooms have always been costly to run and consume large quantities of energy, water and consumables. Our cleanroom at Havant in the 80s operated on three shifts and we spent over a million pounds a year, just on disposable rubber gloves! There are ways of doing it better, to consume less energy, to have different processes demanding reduced usage of consumables and making better use of the resources needed.

JN: Does the new ISO standard on Cleanroom Energy which you oversee relate to this?

DG: Yes, it does. I convene two ISO standards on cleanrooms, one on Airborne Chemical Contamination and the other on Cleanroom Energy. This latter one includes guidelines on cleanroom operations. Typically, they demand huge amounts of energy and the ballroom cleanroom we used to operate in Havant circulated 600 air changes an hour and it was a huge room.  Now, UK manufacturers are building more efficiency into them with automatic particle counting which links to the air flow control so it can be throttled back automatically and thereby improve energy efficiency. I’d like a labelling system to be introduced which is similar to the energy rating label on domestic refrigerators.

JN: I suppose, similar to a fridge, it doesn’t save energy to switch it off when not in use.

DG: Oh no, that would be a big mistake. There would be a shower of contaminants when it is switched on again and it wouldn’t be operational until the particle count was down, which would be a considerable time.

JN: What other energy saving aspects are you looking at?

DG: Humidity, leakage and of course temperature control, particularly the cost of cooling. In disk drive manufacturing, the temperature had to be controlled to +/-0.5C and we’re looking at relaxing that to 5C. In some countries, particularly Russia, the ambient temperatures can vary hugely and this has a big effect on the temperature control inside the cleanroom. Getting this part of the standard right is an important factor for the Russian participant on the ISO team.

JN: What are the challenges of working in an international standard-setting body?

DG: I find it to be a very cooperative environment and it’s interesting because the different nationalities have their own specific areas of interest. France has a high focus on the Nuclear and Space industries whilst Russia and Ireland have a significant interest in the Healthcare industry. It provides a very broad scope.

JN: What about electronics industry?

DG: Well, unfortunately much of that has gone from the UK, where there was a lot of activity previously. China and the Far East have emerged as the dominant area for technology with disk drives, chips and plasma screen devices.

JN: Do we still retain a capability?

DG: Most certainly, particularly in terms of skills. There is a lot of experience in the country and all the problems from the last 30 years have been overcome and well documented. Our biggest problem now is a lack of facilities, particularly for verification and certification of processes. Measuring contamination on, for example, a disk enclosure requires an ability to detect particulate contamination of between 3 and 4ng per enclosure casing, a capability that is very hard to find locally.

JN: How do you see the future of the cleanroom industry?

DG: Probably in relation to nano-technology processing where manufacturing tolerances in the nanometre range is the norm. This requires a different approach to cleanroom operations where such factors as vibration are seen as a “contaminant” and need to be controlled.

JN: Thank you very much, it was a great pleasure to meet you again after such a long time.

DG: It’s my pleasure.

Cleanroom classifications

The historic classification system for cleanrooms was the now defunct US Federal standard 209E which is still often used due to habit, ease of understanding and its equivalent to much of the ISO standard. However, it fails to reach down to the lower contaminations specified in ISO 14644 Part 1.

The table shows a comparison of the two standards for a range of cleanroom classes with the particle counts being the maximum allowable number which is greater than or equal to 5 microns (µm) in the given volume (1m3 for the ISO standard and 1ft3 for the US standard)

The ISO 14644 standard has several parts, each describing an aspect of cleanroom classification, design, operation and testing.

Table 1: Comparison of cleanroom standards

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Jonathan Newell
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