Sustainable considerations for parts cleaning in hi-tech production

9-May-2022

Making products like complex semiconductors, or life-saving medical devices requires all components are free from pollutants like dust, manufacturing particulate, lubricants, and fingerprints. But this process must also prioritise environmental standards as MicroCare's Elizabeth Norwood explains

Critical cleaning, such as parts cleaning within the cleanroom environment, is an extremely important consideration for manufacturers. Advanced high-tech production requires stringent contamination control.

Cleaning, sometimes down to the sub-micron range, is also essential to ensure parts meet the process validations required within a cleanroom environment. However, some of the more popular cleaning methods and fluids once considered industry standards are now under environmental or worker safety scrutiny.

Unlike aqueous cleaning, vapour degreasing takes up little valuable floor space inside a cleanroom

Faced with the possibility of needing to change their existing cleaning methods and fluids, manufacturers are looking for better alternatives inside their cleanrooms. They need cleaning fluids that not only clean well and are easily validated today, but will also meet evolving sustainability and regulatory standards well into the future. One cleaning method that meets this emerging sustainability challenge is vapour degreasing.

Meeting the sustainability challenge

Vapour degreasing, when used in combination with modern, sustainable cleaning fluids, is a 'greener' more environmentally sustainable approach to parts cleaning. The low viscosity and surface tension ratings of modern vapour degreasing cleaning fluids, combined with their volatility, ensure all parts surfaces are effectively cleaned. They also adhere to stringent process validation specifications which are essential within a cleanroom environment. Additionally, new advances in cleaning fluid technology mean that modern vapour degreasing is an environmentally sound option meeting strict local and national air quality regulations and operator safety requirements.

Vapour degreasing is a closed-loop industrial cleaning process. It consists of a top-loading machine comprised of two chambers, the boil sump and the rinse sump. Both are filled with a low-boiling, non-flammable cleaning fluid.

In the boil sump, the fluid is heated and parts are immersed and cleaned. Parts are then mechanically transferred to the rinse sump for a final wash in a pure, uncontaminated fluid. The parts come out clean, dry, spot-free and immediately ready for the next step in the process or packaging.

Steps to sustainable cleaning

When it comes to sustainable vapour degreaser cleaning, there are certain factors that are important to consider.

Preserve natural resources and fossil fuels: There are significant resource and energy savings with vapour degreasing. Unlike aqueous cleaning, vapour degreasing uses no water, therefore, conserving this vital non-renewable resource. In addition, there is no ongoing stream of wastewater to filter, distil, deionise, or osmosis prep prior to disposal.

Many of the modern, sustainable cleaning fluids used within a vapour degreaser also have a low boiling point and heat of vapourisation. This means vapour degreasers typically require less power to run than most aqueous cleaning machines which need large amounts of energy, either electricity or natural gas, to heat the water for cleaning.

Historically, brominated and chlorinated solvents were used, but these are now becoming obsolete

Also, modern vapour degreasers do not require additional equipment like air knives or blowers to dry parts, reducing the amount of energy needed to clean effectively and cutting total carbon emission and greenhouse gas output. It is important to also point out here that a reduction in energy equates to a reduction in operating costs.

Eliminate waste: Vapour degreasing systems have the capacity for continuous recovery and recycling. The vapour degreasing fluid can be used and recycled many hundreds of times within the vapour degreaser before it needs refreshing or replacing.

Meet environmental regulations: The cleaning fluids for manufacturing parts have strict environmental guidelines to follow. Growing numbers of regulatory agencies and governing bodies across the world are increasing legislation and enforcing the laws in an effort to reduce any negative impact on the planet and its people.

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Historically, brominated and chlorinated solvents like nPB (n-propyl bromide), PERC (perchloroethylene) and TCE (trichloroethylene) were used inside a vapour degreaser to reliably and economically clean parts. These however are now becoming obsolete as they do not work with new environmental restrictions and have longstanding worker safety concerns. While still used in the United States, TCE has a carcinogen classification in some jurisdictions and has not been available for vapour degreaser cleaning in Europe without special authorisation and stringent controls on factory emissions since 2016.

Additionally, as part of the US EPA TSCA Risk Evaluation process, TCE has been classified as a High Priority Substance and it ha been determined that TCE presents unreasonable risk to users. The US EPA is in the final steps of formulating new regulations to reduce worker exposure. And under EU REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations, nPB is included in the candidate list of "Substances of Very High Concern for Authorisation" (SVHC substances) and requires special permission for use in Europe as of 2020. Hydrofluorocarbons (HFCs) are also now being phased out of production by EU F-Gas regulations and by the American Innovation and Manufacturing (AIM) Act in the US.

Limit ODSs and GWPs: In addition, the international Montreal Protocol agreement regulates the production and consumption of man-made chemicals which contain ozone-depleting substances (ODS). Established in 1987, it identifies a list of nearly 100 ODS that threaten human health by lessening the earth's protective stratospheric ozone layer. Some ODS are strictly controlled for their use. Others are targeted for phasedown and others were completely phased out at the time of finalisation.

Since it began, 197 countries have participated in the Protocol which has resulted in the phase-out of 99% of nearly 100 ozone-depleting chemicals. The Montreal Protocol's Scientific Assessment Panel estimates that with the implementation of the treaty we can expect near-complete recovery of the ozone layer by the middle of the 21st century. This underlines its importance and why it is critical to use sustainable cleaning methods.

Many of the new sustainable cleaning fluids are based on HFO (hydrofluoroolefin) technology that offers excellent performance along with improved environmental advantages. This includes zero ODP (Ozone Depleting Potential) ratings, low GWPs (Global Warming Potential), and many with no Volatile Organic Compound (VOC) content.

Cleaning sometimes needs to be done down to the sub-micron range

The GWP of a cleaning fluid is a measurement of the atmospheric lifetime of the fluid or its gaseous vapours. The longer a trapped gas absorbs infrared radiation in the atmosphere, the more it may contribute to global warming and climate change. The new cleaning fluids typically have a low GWP of 3 or less. By comparison, the older solvents used in cleaning fluids, like HCFCs (hydrofluorocarbons), had average GWP ratings in the thousands.

New sustainable vapour degreasing cleaning fluids offer improved environmental properties without compromising on cleaning performance. These new fluids clean just as well, if not better than the older legacy solvents under scrutiny.

Vapour degreasing is a consistent, repeatable and easily documented process. Plus, unlike aqueous cleaning, it takes up little valuable floor space inside a cleanroom and removes water, a potential source of bioburden, from the cleaning process.

Safety: When looking for sustainable long-term cleaning solutions, worker safety must be a primary concern. In addition to providing effective, repeatable and sustainable cleaning in a cleanroom, vapour degreasing and modern cleaning fluids are also safe to use. Greener cleaning fluids replace solvent chemistries that could be harmful, or are on the list of those under scrutiny.

Advanced vapour degreasing fluids have a very good safety profile. In the USA, the OSHA-designated time limit or PEL (Permissible Exposure Limit) that workers are exposed to a chemical is far more acceptable for new sustainable cleaning fluids than their legacy counterparts. The PEL is usually 200-250 ppm (parts per million) for modern, sustainable fluids. When compared with older legacy cleaning fluids like TCE which has a 100-ppm PEL or nPB which is rated at less than 0.1 ppm. It is clear to see the safety advantages of modern cleaning fluids for exposed workers.

A greener cleanroom

As parts produced in a cleanroom become smaller and more complex, they also become more sensitive to contamination. Finding a cleaning process that is reliable and consistent is critical to reliability and quality. But this is only half the challenge. The cleaning process must also meet changing regulations, safety standards, validations and environmental targets.

Vapour degreasing, together with highly-advanced cleaning fluids provide sustainable and safe precision cleaning. It not only ensures parts are perfectly clean and pass the cleanroom's high standards, but it also addresses worker safety and long-term environmental concerns by reducing the use of fossil fuels, limiting waste disposal, and controlling and restricting any harmful emissions.

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For companies looking for help in selecting and using sustainable manufacturing cleaning fluids that can be used in highly regulated environments like a cleanroom, it is essential to work with a partner that has expertise in the subject. Based on specific parts make-up and the contamination encountered, they can recommend the sustainable fluids and cleaning methods that will work best.

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