Why UL 94 is important for PCB(Electronic product industry)?

UL94 is a material flammability safety standard developed by Underwriters Laboratories (UL) in the United States, which is mainly used to evaluate the flame retardant properties of plastic materials.UL 94 test is a key safety indicator to ensure that PCBs will not burn quickly, drip, or spread the fire when exposed to high temperatures or accidental fires.

Relationship between PCB materials and UL94

Base material (such as FR-4)
Conventional FR-4 is usually V-0, which is achieved by adding flame retardants such as brominated epoxy resin.

Halogen-free FR-4 (environmentally friendly) requires optimized formulation to maintain V-0 performance.

Coating material (such as solder mask ink)
The solder mask layer and silkscreen ink also needs to be UL94 certified to prevent surface burning.

Special scenarios
High-frequency PCB (such as PTFE material): Additional treatment is required to meet flame retardant requirements.

Flexible PCB (FPC): Polyimide substrate is usually V-0, but attention should be paid to stability at high temperatures.

UL94 Key Levels(V-0,V-1,V-2,HB)

UL94 is divided into several flame retardant levels based on the performance of the material in vertical or horizontal burning tests. Commonly used in PCB substrates are:

V-0:
In the vertical burning test, the flame goes out within 10 seconds and there is no burning dripping.

This is the most common flame retardant level for PCB substrates (such as FR-4) and has the highest safety.

V-1:
The flame goes out within 30 seconds, a small amount of dripping is allowed, but it will not ignite the cotton wool below.

V-2:
The flame goes out within 30 seconds, but the dripping may ignite the cotton wool below.

HB (Horizontal Burning):
The material burns more slowly when placed horizontally, has lower flame retardancy, and is usually used in low-risk scenarios.

Common PCB substrates and UL94 level:

FR-4: The most commonly used substrate, usually compliant with UL94 V-0.

CEM-1/CEM-3: Composite epoxy resin material, mostly with a flame retardant rating of V-0 or V-1.

Polyimide (PI): High-frequency/high-temperature PCB substrate, usually V-0.

Notes for UL 94

Material certification ≠ finished product certification: PCB substrate passes UL94 test, but UL certification of the final product needs to be applied separately (such as UL 796)

Other factors: In addition to the substrate, materials such as solder mask ink ,silkscreen ink and copper foil may also affect the fire resistance of PCB.

Xinfeng Huihe Electronic Technology Co.,Ltd's pcb has been passed UL 94V-0 test,UL file number(E535792),you will be surely get UL certificated PCB in here.If you have more questions you can send an inquiry to email:sales@hhetech.com