Steve Allen, our guest blogger from ACL, this time focuses on the topic of VOCs and aerosol cleaners
An important topic today with end-use customers using aerosol cleaners, is the changing regulations regarding the VOC content and compliance of solvent-based products. Many customers are perplexed as to why manufacturers and suppliers don't already have this information on their product MSDS (GHS safety data sheets) and tech data sheets. At one time, the weight percent of all non-exempt chemicals in most products was listed on each product MSDS, but this information has been removed for several reasons. And, as most everyone knows, the regs are changing all the time.
It's important to review what a VOC is and why it's important. VOC stands for "volatile organic compound." These are chemicals whose vapors have been found to chemically react with nitrogen oxides (NOx, which are produced by auto exhaust, the burning of fossil fuels for power generation, and other industrial processes) in the air and in the presence of sunlight to produce ground-level ozone or "smog". The ability of certain chemical vapors to produce smog when sunlight makes them react with nitrogen oxides is referred to as photochemical reactivity. The direct emission of these vapors into the air defines the scope with which the EPA is most concerned. Thus, chemicals whose vapors are not photochemically reactive to form smog are considered exempt and are not included in the process of determining the amount of VOC ingredients in a particular product.
The federal EPA publishes a list of exempt chemicals and many states also publish their own list. A chemical that is listed as exempt on the EPA list may not appear on the individual state or municipality listings. A basic Internet search for methods of calculating VOC will generate literally 1000s of information sources and reference sites. VOC test results are used for a variety of purposes. These are predominantly for emissions fees, new source review applicability, and compliance with permit limits.
Most VOC and air quality/emissions permits do not specify VOC test methodology for purposes of demonstrating compliance with VOC limits. Currently, there are inconsistencies and a lack of guidance among states and EPA regions in implementation of VOC test methodology. It is technically difficult to specify any one single method for VOC measurement. This is why it is difficult to specify a simple value for the VOC content of most cleaning products. Without specific knowledge of the area of the country in which the customer is located, the EPA region under whose regulations they operate, if they are operating under a Federal NESHAP, the existence of state and local emission regulations, and the specific application or way in which the product will be used, it is difficult-to-impossible to list accurate and specific VOC information on a product MSDS.
Many states do not recognize all of the chemicals on the EPA lists as being exempt. Formal exemption of a chemical from VOC consideration may depend on how it is being used. California is generally the most extreme case and most industry there is moving toward water-based cleaning.
So, why are VOC determinations mission-critical today? Traditionally, VOCs have been used for conformal coating and various contact cleaning and flux removal applications. The properties of a conformal coating stem from the selected base resin and the various additives, while the solvents used in most cleaners come from an aromatic or aliphatic hydrocarbon base. These are included to optimize the performance of the cured coating or the formulated cleaner. Organic solvents are used to dissolve the base resin and reduce viscosity to bring the coating within a workable range. As such, the conformal coating dries by a simple solvent evaporation. Contact cleaners and flux removers function in the same manner.Solvent-based conformal coatings are extremely versatile and can be applied in many ways, such as dipping, spraying, and brushing. By simply adjusting the solvent level, the viscosity of the coating can be tailored to the required application method. Solvents or VOCs are used for many different cleaning applications during PCB manufacture. Until recently, there has been a reluctance to change to alternative products for a number of reasons:
- Change required alterations to production procedures and equipment
- Solvent-based materials were very well established
- Alternatives did not have all the answers
- VOC limits on solvents were changing as were test methods
Many manufacturers are turning to "no-clean" processes implying that cleaning is not required after soldering. In the "no-clean" process, rosin and activator are not removed prior to the next process such as coating or encapsulating of the PCB. Such residues, along with any other unwanted elements collected due to the missing cleaning stage, could cause issues with adhesion and possibly affect the performance of the protecting media applied. It can therefore be stated that even with advances in new technologies, such as "no-clean" fluxes, cleaning is still an essential multi-stage process within the electronics industry. Finally, there are also cleaning stages required for the removal of coatings and adhesives when re-work is necessary and for the cleaning of actual components and for maintenance of the production line.
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