UL identification

What is UL?

UL is an American organisation with a recognised identification system, over the years, they have developed numerous safety standards and testing procedures. UL standards are very comprehensive and cover a wide range of risks; these are based on the field of application, the materials used and the manufacturing and assembly processes. For electrical appliances, the main focus is to ensure fire protection and electrical safety.

Your requirements:

Which UL parameters must the device comply with? Which appliance class does your product belong to and which higher-level UL standards are applicable? Which information in the UL certification documentation (“Section General” or in the “description” for critical components) define the necessary UL requirements?

Our solutions:

UL and flex-rigid – our strengths: We have 4 UL models listed for flex-rigid PCB´s!

We are happy to help you find out which model best suits your application based on your specific requirements. Get in touch with our UL specialists immediately!


Combustibility according to UL94 Standard: We satisfy the very highest UL specification “UL94 V-1 or better”!

Tracking resistance

Comparative Tracking Index (CTI; ASTM D3638 ) – are there any requirements regarding tracking resistance? We offer flex-rigid solutions for a CTI range-tracking index of 250 – 400V (PLC 2).

Maximum operating temperature (MOT)

Maximum operating temperature (MOT): We have successfully passed the tests for MOT120 in accordance with UL796F.

Based on the UL testing method, the MOT value gives an indication of up to which temperature a type of circuit board with a defined, cohesive copper surface will exhibit

  • no signs of delamination.
  • copper adhesion, albeit very low levels, of 0.175N7mm demonstrated after the 56 day test.
  • at least 50% of original mechanical and electrical properties still exhibited.

In this process, neither the period of use nor the load cycle are defined (mission profile), it also does not account for thermo-mechanic material properties or heat generation caused by leakage of thermal power. This is why we generally advise against using this UL MOT value as the maximum continuous operation temperature when using the application. Because although, for example, according to IPC4101/21 standard FR4 only has a minimum of 110°C for one day, it is still certified as UL-MOT 130 by UL standards! It can only be hoped that no one ever comes up with the idea of making a device with a continuous operating temperature of 130°C and giving it an FR4 standard!

Operating conditions under mains voltage (DSR)

Direct support of current-carrying parts: Our UL models satisfy the direct support requirements (DSR) in accordance with UL746A.

The UL testing process

The UL 94 flammability test

The flammability of polymer materials is tested according to Underwriters Laboratories standard UL 94 (among others), whereby a classification of flammability is undertaken.

The best-known classifications are HB, V-2, V-1 and V-0.

UL 94 V 0 (Vertical Burning Test)

In this test, a standardised flame from a methane gas burner of 20mm length is held 10s long at the lower end of a vertically clamped specimen. After extinguishing the flame the procedure is repeated for a further 10s. This is carried out on 5 specimens. The times of burning and glowing are noted and summed together. It is also recorded whether drops fall from the specimen and whether the cotton mounted beneath the specimen ignites.
The UL 94 V classifications range from V-2 to best classification V-0. If a specimen fails to meet the requirements, 5 additional samples are tested. The V-0 classification requires that the cotton does not ignite through glowing or burning drops.

Marking of pcbs is available according to UL-94.