Certifications are an important way to distinguish general purpose varnishes and shellacs from engineered coatings designed specifically for PCB protection. Although there are dozens of user and industry specifications, the two major certifications are IPC-CC-830B and UL746E. When selecting a coating, look for the availability of 3rd party test documentation, rather than coatings with the claim that it “meets the requirements”. Both standards use the UL94 standard to judge flammability, with a V-0 rating signifying the lowest flammability potential.
IPC-CC-830B / MIL-I-46058C
This standard originated with the military standard MIL-I-46058C, which became obsolete in 1998. The civilian version IPC-CC-830B is nearly identically, so it is generally understood that if a board passes the IPC spec it will also pass the MIL spec., and vice versa. IPC-CC-830B is a battery of tests, some pass-fail and others that provide data that can be referenced and compared:
- Insulation resistance
- UV fluorescence
- Fungus resistance
- Moisture and insulation resistance
- Thermal shock
- Hydrolytic stability
Underwriters Laboratories (UL) is considered a credible and reliable safety certification body worldwide, and UL certification is commonly required for consumer goods. UL746E tests for electrical safety and flammable safety of the coated electronics. For electrical safety, there is a battery of tests similar to IPC-CC-830B, but with a cycling current load to constantly measure the failure of the isolative properties of the coating. The flammability test uses the UL94 standard like IPC-CC-830B, which involves attempting to light the cured coating with an open flame and observing the sustainability of the flame.
Once a coating has passed UL746E, it can be registered with UL and assigned a registration number. Products certified and registered to UL746E standards can include the UL symbol (which looks like a backward “UR”). To maintain the registration, a coating much be retested annually.
Coatings can, and often are, tested to standards that only represent a portion of the whole standard. In the case of UL94, this is helpful when flammability is the main concern. Some specialty coatings may not be tested to the entire IPC-CC-830B or UL746E because they may fail portions of the test because of the nature of the product, not a reflection of the quality of the product. For example, some coatings intended to coat LEDs leave out the UV indicator to prevent color shift, but this automatically would cause disqualification under IPC-CC-830B. In other words, it is by definition impossible to pass IPC-CC-830B and have optical clarity in the UV part of the spectrum.
Of course, safety and environmental considerations should always play a part of the chemical selection and process design, but the various regulatory bodies make this even more challenging as requirements have to be interpreted and matched with product specifications.
- OSHA (Occupational Safety and Health Administration)
- EPA (United States Environmental Protection Agency)
- CARB (California Air Review Board) and other regional regulations
REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) as per EU regulation 1907/2006, obliges both manufacturers and importers of substances (components, mixtures and even components in articles) to register them in Europe and to assure a safe use for humans, animals and the environment of these chemicals. The obligation to register starts at 1 metric ton per year of imports or manufacturing
That’s our guide to conformal coating. We hope we answered a lot of your questions. Like any challenge, selecting the best coating and coating process can be broken apart, analysed and solved.
We carry a range of conformal coatings in our world wide assortment, and continusly evaluate which specific coating should be available in these markets;