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Learning with Leo: The Cost of Cleaning and Protecting the Ozone Layer

I share this perspective based on my experience as a member of the United Nations Environment Programme (UNEP) Solvent, Coatings and Adhesives Technical Options Committee, which developed the report “Protecting the Ozone Layer” to inform policy decisions at the 1995 Meeting of the Parties to the Montreal Protocol in Nairobi. My involvement in this work dates back to 1976, when I joined Digital Equipment as an engineer supporting manufacturing operations, focusing on soldering and cleaning processes across global facilities.

In the 1970s, chlorinated hydrocarbon materials were phased out due to their properties, and our assembly processes used solvents considered unacceptable by users and environmentalists for cleaning fluxes from printed circuit boards. Examples of solvents used to clean rosin fluxes included Trichloroethylene (TCE), 1,1,1-Trichloroethane, Chloroethane, D-Sol, and MEK (Methyl Ethyl Ketone).

Subsequently, in the 1980s, those materials were replaced with fluorinated hydrocarbons, which were advertised as safer for the users and the environment. Evaluations and physical samples eventually found that the materials were ozone-depleting and were also phased out of manufacturing.

Our concern was the need to change from existing solvents to another method. The first investigated process was the evolutionary shift from chlorinated to fluorinated hydrocarbons, which were to replace them. Once it was determined that this was an ozone-depleting material, another change had to be investigated.

It was decided to evaluate cleaning fluxes from circuit boards using a water-based system. We investigated aqueous cleaning as a possibility to convert the processes from those solvents to a more environmentally sound solution. After the evaluation was completed and it was announced that the new aqueous cleaning process produced ionically cleaner boards than the solvent process, the changeover began.

However, this change was not without its challenges, since we were using rosin-type fluxes, the chemistries had to be adjusted to create rosin soaps that were biodegradable and disposable, and to meet local environmental requirements for the disposal of the effluent. 

As a worldwide manufacturer, we also encountered the reality of differences in water supply across the world and within our own localities. These variations included water hardness, minerals inclusions, and the adaptations to the equipment maintenance needed to maintain continuous operations.

Implementing the new process across all facilities provided much-needed information to promote it and demonstrate its success. The evolution of the process mandated standardizing the type of water used across our facilities. The results led the company to select deionized water (DI Water) as the main ingredient, and the saponifier selected was an alkaline material with a pH of 12 or 13.

The proper water-solvent mix cleaned boards better than any of the previous solvents, which was better for the environment and employees. With this focus on cleanliness, the concern was the disposal of materials after use. How do we dispose of this material, since it ends up being a 100-gallon batch of high-pH material, and how can we introduce it into the community's waste stream?

Again, further investigations led to adjusting the wastewater pH to neutral and then disposing of the material in accordance with local requirements. At this point, we had a biodegradable cleaning system that met local requirements, and we were running the program across all our plants as part of the wave soldering and cleaning systems.

In 1992, on a global basis and in conjunction with the U.S. EPA, global multinational companies were approached and invited to participate in a worldwide program to publicize our work, reduce and promote the use of cleaning solvents that are not detrimental to the environment, specifically in this case, ozone-depleting materials, thereby reducing and eliminating the use of ozone-depleting solvents from the manufacturing operations.

As team members, we were to consult with online managers, write recommendations on innovative technologies, discuss implementation obstacles, benefits, and financial obligations, and highlight the successes of the methodology and processes we had implemented.

Since CFCs (chlorofluorocarbons) were banned, the introduction and implementation of the program has resulted in a decline in CFC concentrations in the atmosphere, which peaked in the 1990s and has been declining ever since. The Antarctic ozone hole stopped getting worse in the early 2000s. Since then, satellite observations show a gradual long-term recovery of stratospheric ozone. 

Currently, the 2025 Antarctic ozone hole was among the smallest observed in decades. NASA and NOAA ranked it the fifth smallest since 1992, and scientists report that ozone holes are now generally forming later, becoming smaller, and closing earlier in the season. 

Based upon the initial goals of the program and the physical recovery rates resulting from the elimination of CFCs, improvements are being observed worldwide. 

In conclusion, working together with all the involved nations, the program is considered a success. 

Leo Lambert is the technical director at EPTAC Corporation.