Although declared inactive nearly 20 years ago, the DLA spec remains alive in use.
During your selection of conformal coating, you ran into a specification that you have seen before but not fully understood. Conformal coating choices are vast, but with so many available, how does a user pick the correct one? Are there minimum standards that define what a conformal coating is supposed to do?
Thankfully, yes there are. Here we focus on one such standard: MIL-I-46058C.
The official title for the specification is MIL-I-46058C, “Insulating Compound (for Coating Printed Circuit Assemblies).” The standard serves as a material standard, used to evaluate and document that a particular coating meets a list of specific performance attributes (more on those later). MIL-I-46058C was developed to define a uniform set of test methods and performance requirements for conformal coatings and gives users confidence the material they select will perform.
MIL-I-46058C is managed by the Defense Logistics Agency (DLA). DLA manages the standard and maintains the associated Qualified Products List (QPL). For a coating to be placed on (and stay on) the QPL, it must be tested annually by a DLA-certified laboratory. The data are reviewed annually by DLA to ensure each coating proposed for inclusion on the QPL still meets the requirements of the standard. The latest version of the Qualified Products List is available from dscc.dla.mil.
MIL-I-46058C evaluates conformal coatings to an extensive list of properties. The tests are:
MIL-I-46058C was declared “inactive” in November 1998. This deactivation meant the standard was “inactive for new designs, except for replacement purposes.” This certainly does not mean MIL-I-46058C disappeared from the landscape. Today, MIL-I-46058C persists for coating users and specifiers due to its requirement for independent third-party certification and remains the only published conformal coating standard with an associated QPL.
Caution! As a user, you have many choices of conformal coatings. Many materials claim to “meet the requirements” of MIL-I-46058C. These coatings have probably not been fully tested to the rigorous standard required to obtain and maintain MIL-I-46058C qualification. Treat these coatings with caution: “meets” does not mean “is” on the QPL. There is only one way to verify this and that’s through the DLA.