What are the dangers of solvent exposure with conformal coating?

Many widely used coatings contain large percentages of harmful which can cause great harm to operators if used incorrectly. For instance, toluene, a widely used solvent is now classified as a Class III carcinogen which can cause cancer.

Therefore everyone in a company should take the issues of safe solvent use seriously, including company directors who are ultimately held accountable by law down to the operators who use these dangerous solvents in their process. Ultimately, a mistake can seriously harm a person and/or end in serious litigation costing a company dearly.

So what options are there when considering solvent conformal coatings?

Option 1: Regularly measure the solvent exposure to operators.

Solvents can be used safely. However, the exposure of the operator to the solvent fumes must be REGULARLY measured and RECORDED. This ensures a safe operating environment and if a HSE problem does arise in the future, evidence exists to rule out the conformal coating process as the culprit.

The regular measurement of solvent fumes can be a low cost, easy exercise using products such as Solvent Exposure Monitors (SEA’s). SEA’s can easily be integrated into the coating process, continuously monitoring the solvents and raising an alarm if needed when exposure limits are reached. This ensures operators stay safe and have the confidence to use the processes safely.

Option 2: Change to a safer conformal coating material

Solventless conformal coatings are now widely available and are almost a drop-in replacement due to the advances in technology. Types available include water based acrylics and polyurethanes, solventless silicones and UV curable acrylics and all do a similar job in protecting the boards compared to solvent based materials.

Changing materials would mean no need to measure solvent fumes, operators would not be exposed to hazardous coatings, and litigation due to employee sickness would be much less likely.

Option 3: Use an independent subtract coating service

This solution using an independent coating service eliminates all the hazards of solvents immediately. Allowing another company to utilize the harmful coating materials means no re-qualification is required without needing to invest in operator safety and equipment.

Summary

There are three options for companies using solvent based conformal coatings.

Measure the solvent fumes regularly to ensure the operators are always safe.

Change to a solventless conformal coating eliminating the issue completely.

Subcontract the hazardous process to a coating service.

SCH Technologies are experts in all aspects of conformal coating whether it is providing the Humiseal range of conformal coatings, coating application equipment including spray booths and dip systems, subcontract conformal coating service and providing SEA solvent exposure monitoring equipment.

First we need to understand a few bits of terminology. Once you have a grasp of these then it is a fairly straightforward process.

First, what you are looking at here are Workplace Exposure Limits (WELs). These are the Occupational Exposure Limits (OELs) that have been set by the health and safety commission and are there to help protect the health of workers.

WELs are concentrations of hazardous substances in the air, averaged over a specified period of time referred to as a time-weight average (TWA). Two time periods are used: long term (8 hours) and short term (15 min). Short-term exposure limits (STELs) are set to help prevent effects, such as eye irritation, which may occur following exposure for a few minutes.

Therefore, LT EXP 8 hrs and ST EXP 15 min translate as the Long Term Exposure Limit of 8 hours and the Short Term Exposure Limit of 15 minutes. These two values set the maximum level of exposure on average that a worker should receive whilst using the solvents.

The values are defined in ppm (parts per million) and it is these exposure limits that should be compared with measured values that should be taken whilst the worker is carrying out his tasks.

If you do not carry out this check and your workers are over-exposed to the solvents then the worker may become ill in a variety of ways. There may be short and long term effects that ultimately could lead to occupational diseases that may not appear until a long time after the first exposure. Therefore, it is critical to know in advance how to protect the health of people working with hazardous substances.

There are several ways to do this that take a “snap shot” of typical day including having your staff wearing personal monitoring devices and then having the monitoring devices sent away and analysed. This is an excellent way to accurately identify the risks at that exact time but can be time consuming and very costly. Also, any change in the system, whether that is a change in material, equipment, process or operator action will ultimately mean that you will need to re-test to prove that system is still sound.

An alternative is to use large amounts of extraction with your process and hope that this prevents any exposure. However, you are reliant that there are no failures in the extraction & equipment and that your operator does not change the process in any manner.

Therefore, the only way to really be sure of the system being safe for your workers is to use a combination of factors.

First, set up a process that ensures that the worker is safe within the environment. This is done with adequate extraction, an identified process with boundaries and good staff training.

Second, and most importantly, is to continuously monitor the process, recording the exposure to the worker. With new technology, this can be achieved cost-effectively and accurately enough to remove risk to operators using VOC monitoring systems.

From our HSE risk assessment we can draw the following conclusions:

• Only UV A light is emitted from the twin UV 38w lighting units
• Readings for light in the UV B and UV C spectra were indicated as zero
• The UV A light intensities were within the suppliers specifications
• No detectable reflected UV A light was evident within booths, the levels being consistent with background irradiance.
• The recommended long sleeve ESD clothing & nitrile gloves that operators should wear all blocked the UVA emitted by the lights
• The Peltor Solus (EN 70) eye protection glasses supplied with the system effectively blocked 100% of the UV A light

We issue all Peltor Solus (BS EN 170) clear eye protection glasses which under tests within our facility effectively block 100% of the UV A light which is the only Ultra Violet wavelength range produced by our UVA lights.

The OSHA Standard for eye protection is 29 CFR 1910.133 and the ANSI standard that contains recommendations for eye protection is Z49.1.

In is worth noting that our staff also wear long sleeved ESD Coats and Gompels nitrile pf sens blue gloves both of which have again been shown to effectively block 100% of the UV A light produced.