What is UL and how does it relate to conformal coating?
UL stands for Underwriter Laboratories. They are a global safety certification body for consumer electronics.
When a conformal coating states that it has a UL qualification, it means that the material has been independently tested by UL in one of their laboratories and passed a particular standard.
UL carry out the testing. It is independent. There is no self-certification available.
UL qualified conformal coatings are used in all areas of electronics protection including aerospace, industrial controls, automotive and telecommunication sectors.
What UL standard tests are used with conformal coating?
For conformal coating materials there are two standard tests typically used.
These are UL94 and UL 746E.
UL 94 Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing.
UL 94 is a plastic material flammability standard. It classifies plastics according to how they burn in various orientations and thicknesses.
UL 94 measures a conformal coating material’s ability to extinguish or to spread the flame once a test specimen has been ignited.
This ability is ranked as a classification as below.
Classifications
For conformal coatings the coupons are normally tested Horizontally (HB).
Tests are normally conducted on coupons of the minimum approved thickness with different types of laminate.
The conformal coating thickness range also is normally specified.
- V-2 burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
- V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
- V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
Most conformal coatings aim to achieve V-0 status.
UL 746E Standard Polymeric Materials: Industrial Laminates, Filament Wound Tubing, Vulcanized Fiber and Materials Used in Printed-Wiring Boards
The UL 746 test measures the 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.
Need to find out more?
Click UL standards and conformal coating for further information on whether you need UL qualified conformal coatings or contact us directly and we can help you.
If you are new to Nexus and our work on conformal coatings then a good place to go is our Start Here page or our free conformal coating eBook.
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