Conformal Coating Standards: MIL-I-46058C, UL 746E and More

The conformal coating standards that currently exist can be considered from two points of view. First, there are the standards that are used by the manufacturers of conformal coatings to qualify the products, whether that is done by self-certification or completed by independent testing. Second, the standards are a method for users to determine the quality of the conformal coatings they are considering. Below are four key standards:

• MIL-I-46058C Insulating Compound, Electrical (For Coating Printed Circuit Assemblies)
• Underwriters Laboratories (UL) UL 746E and UL94
• IPC-CC-830B Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assemblies
• IEC 61086-1 edition 2.0 Coatings for loaded printed wire boards (conformal coatings) – Part 1: Definitions, classification and general requirements

MIL-I-46058C
The Mil Standard for conformal coating has been inactive for new designs since November 1998, though is still widely used for independent certification of all types of conformal coatings. All companies tested to the Mil standard are listed on a Qualified Product List (QPL). Conformal coatings listed on the QPL have been through rigorous third-party testing.

UL 746E & UL 94
UL is a global safety certification body for consumer electronics. For conformal coating, two parts are important, UL 94 and UL 746E.

UL 94 measures conformal coating material’s tendency either to extinguish or to spread the flame once the test specimen has been ignited. The first program is described in UL 94. This is now harmonized with IEC 60707, 60695-11-10 and 60695-11-20 and ISO 9772 and 9773.

UL 746E measures the ignition resistance of the conformal coating to electrical ignition sources. The conformal coating material’s resistance to ignition and surface tracking characteristics is described in UL 746E.

IPC-CC-830B
The IPC-CC-830B Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assemblies was originally written as an alternative to MIL-I-46058C and is used for conformal coating applications all over the world. The major difference between the IPC standard and the Mil and UL standard is that the IPC standard is self-certification and not completed by independent means.

IEC 61086-1 ed2.0
The IEC 61086-1 ed2.0 Coatings for loaded printed wire boards (conformal coatings) – Part 1: Definitions, classification and general requirements provides the guidelines for electrical insulating materials suitable for application as coatings for loaded printed wire boards (conformal coatings). This standard excludes requirements for compatibility between such coatings and printed wire boards, this characteristic being evaluated in individual applications.