Toluene and Xylene: solvents that have shown value and utility within the adhesives and coatings industries for decades. However, they often serve as a double-edged sword, offering superior solvent and drying capabilities but accompanied by some negative health and environmental impacts.

We at HumiSeal would like to dedicate a bit of time and space to one of the most often ignored factors related to successful conformal coating processes: Clean Air.

Conformal coatings rose to prominence in protection of printed circuit boards (PCBs) about five decades ago. Through their use, early PCB failures due to dust and dirt, liquids, and humidity contamination were greatly reduced or eliminated. This in turn allowed for the longer warranties and improved reliability we see today. Early conformal coatings, many of which are still in use today, were comprised of polymers dissolved in various solvents such as MEK, toluene, or xylene.

An approximate evolution of conformal coating chemistries could be viewed as

1. solvent-borne acrylics and polyurethanes
2. waterborne acrylics
3. synthetic rubber coatings
4. UV-curable acrylated urethanes
5. LED UV-curable acrylated urethanes

March 4^th of 2020 represented a potentially seminal date for both suppliers and manufacturers within the printed circuit board industry. This was the date of release of four updated Guobiao or “GB” standards related to the VOC content and other harmful substances allowable within supplied inks, adhesives, and protective coatings in China. This change in regulations is the result of China’s three-year action plan begun in 2018. The plan is intended to improve air quality through reduction of VOC emissions by at least 10% as compared to 2015 levels.

The new standards are straightforward but can become difficult to understand as they are often implemented by city and by region.

Xylene and Toluene. Two words that can evoke concern and add to paperwork for environmental health and safety departments and manufacturing professionals. Aromatic solvents have been safely used for decades by employing basic safety equipment including gloves, masks, and proper workplace ventilation. Nevertheless, concerns for maximizing employee safety and minimizing effects on the environment have led electronics manufacturers to seek out alternatives. For over 20 years, HumiSeal® has supplied a wide-ranging group of aromatic-free products across all traditional chemistries to manufacturers for whom these concerns are critical.