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Knowledge For PCB Introduction of PCB fire rating

Introduction of PCB fire rating

July 19, 2022     Knowledge For PCB

UL certification mark introduction

** Recognized (Recognized) Service Mark**: Recognized is the inclusion of components, recognized as a complete expression: mainly for components and materials to implement a safety certification. Recognized service is one of UL's services, its identification of products can only be listed in UL, classification or other recognized products as components, raw materials used.

Recognized components are assembled in the finished product, and the components must meet the relevant permit conditions before they can be used in the corresponding finished product, so that the recognized product is not structurally complete or has certain restrictions on its use to ensure that the desired safety performance is achieved.

In most cases, the tracking service of approved products belongs to the R category. Approved products that fall into category L are electronic wire (AVLV2), processed wire (ZKLU2), wire harnesses (ZPFW2), aluminum wire (DVVR2) and metal flexible tubing (DXUZ2). Approved products are required to bear the approval mark. So such as switches, printed boards, transformers, wires, plugs, plastic materials, etc. that constitute a complete product are approved objects

PCB fire rating

UL certification, or fire rating certification, was originally developed by Underwriters Laboratories Inc. UL94 is a flammability standard for plastics developed by Underwriters Laboratories Inc (UL), which sets standards for each class based on the combustion condition, burning time, and extinguishing time of the tested product after ignition. From the lowest flame resistance to the highest flame resistance, the following are common.

  • HB: Slow burning on horizontally placed samples, with a burning rate of less than 75 mm/min for materials less than 3 mm thick.
  • V2: Stop burning within 30 seconds on vertically placed samples, allowing drops of burning particles to fall.
  • V1:Stop burning within 30 seconds on a vertically positioned sample and allow non-burning particles to drip down.
  • V0: Stop burning within 10 seconds on a vertically placed sample, allowing non-burning pellets to drip.
  • 5VB: Stop burning within 60 seconds on a vertically positioned sample, no dripping is allowed, and holes are permitted.
  • 5VA: Stop burning within 60 seconds on a vertically placed sample, no dripping and no holes on the sample are allowed.

Currently, most of the common substrates for PCBs are FR4, and the required UL certification for FR4 is 94 V0.


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