Keywords: 94V-0 PCB

UL 94 V-0 is a flammability standard for specific printed circuit board (PCB) material that defines its high flame retardance. This rating informs that the material corresponds to UL 94V-0 PCB tests for flammability. In particular, it means that the material is 94V-0 according to Underwriters Laboratories standard UL 94.

With regards to electronics equipment for example portable equipment such as its circuit boards, flame resistance is a very important factor that has to be considered to avoid conflagration. All the materials that carry out the 94V-0 rating retain the vertical burning characteristic of UL 94 standard most recognized test procedures. This paper covers all the necessary information about the imperatives of PCB flammability ratings, what information the 94V-0 standard includes or entails and important factors to consider when choosing boards.

PCB Flammability Ratings

Polymeric substances inclusions today are resin, reinforcement fabrics, and bonding films, which by inherent characteristic possess different flammability. Standardizing the flame retardant properties of circuit boards offers measurability to safely guide the material.

UL 94 Flammability Testing

The Underwriters Laboratories test procedures UL 94 flame classifications define the burning characteristics of plastic substances. They come into testing so that ignition resistance as well as the burning characteristic can be judged.

UL 94 V – vertical burn test

UL 94 VTM – Test method for vertical burning test of thick materials

V1564 – Test method for vertical burning test of advanced thermoplastic materials polyester or other thermoplastic materials at a test level of 5V.

From the results, materials are given UL flammability classifications of V-0, V-1, and V-2 with reference to the varying resistance of burning. There can also be other additional designations for the materials, which include 5VA, and 5VB under the UL 94 5V test standard.

UL 94 V vertical burning evaluation maxim with the V-0 class accredited 94V-0.

IEC 60695 Fire Hazard Testing

Another set of standards for Electrotechnical products and components is provided by the IEC 60695 series issued by the International Electrotechnical Commission and which identifies potential fire hazards. This includes:

IEC proposal IEC 60695-11-10: Glow-wire flammability test

IEC 60695-11-20 – Needle flame test for charities of flexible material

Thus UL 94 not only permits relative rating of the materials in terms of flammability but IEC 60695 directly specifies pass/fail criteria to the tests. Evaluating separately these two testing methodologies ensures more comprehensive results of PCB fire safety. Generally, any material that has the 94V-0 rating also passes the IEC 60695 tests.

What is UL 94V-0 Rating

The type of PCBs that are 94V-0 printed circuit boards have complied to the UL 94 V flammability test reaching the vertical burning classification level ‘V-0’. This suggests that the boards have extremely high fire resistance with self-extinguishing times below 0.1 of second when lit.

UL 94V-0 Rating Criteria

Average burn time is to be less than or equal to 10 seconds.

Total burn time ≤ 50 seconds

No burning drops allowed

No glowing particles allowed

This is due to the meaning of 94V-0 that represents some of the toughest flame classifications under the UL 94 vertical burn tests. It reflects high flame retardance in terms of its ability to self-extinguish, not dripping and its ability to resist glow or spark.

Advantages of using 94V-0 PCB Materials

Printed circuit boards compliant with the 94V-0 rating provide substantial safety enhancements and fire prevention measures for electronics systems:

Non - flaming- quickly consumes flame and does not continue burning when ignited is removed.

Halogen-free – efficiency in preventing the formation of toxic/corrosive gas produced when burning.

Glow-wire resistant – Lacks glow incandescence when comes into contact with hot wires

Non-dripping – Stops a viscous stream of flaming molten particles from the structure.

Therefore using UL 94V-0 material reduces chances of fire and smoke related losses. These are important in consumer products, industrial electronics and medical devices as well as in transport systems. The high degree of flame retardance also enables such circuit boards to easily fulfill the consumer safety requirements on the end product.

Materials Used in making 94V-0 Circuit Board

Flame-retardant (FR) Laminates: These laminates are available with Glass fabric-reinforced epoxy or polyimide cores that afford themselves compliance to UL 94V-0 & IEC 60695 standards by using brominated formulations. They provide the best solutions for questions of electrical, heat and mechanical loads.

High Temperature (Hi-Tg) Laminates – enhanced epoxy resins crossing the glass transition temperature makes the products UL 94 V-0 compliant while having higher operating temperatures over 170°C. That means to have a certain level of comprehension of soldering processes.

Composite Epoxy Materials (CEMs) – FR-4 replacement material based on using non-woven fiberglass fabric reinforcement. Includes individual parts that have achieved a V-0 rating, the use of which does not require halogenated flame retardants. Environmentally friendly.

A large number of reliable PCB manufacturers provide 94V-0 certified, with different base materials for the rigid, rigid-flexible, flexible, and high-frequency boards that are designed to maximize fire resistance. The exact resin chemistry as well as the weaving styles requires innovative strategies to achieve no drip flammability as well as adequate dielectric, thermal and mechanical performance.

Once again the production technique involved is identified as Lamination Construction for 94V-0.

Base materials, prepregs, bonding films which constitute the printed circuit board stackup determine the fire safety rating. Decisions in this design domain are required for core layering, PCB thickness, and lamination.

Selecting Cores/Prepregs

A multilayer board should be made of cores, prepregs and bond plies that have been certified according to the UL 94V-0 standards. Since prepregs and cores do not meet V-0 requirements individually, it may lead to failures even if the copper layers meet or offer V-0 results separately.

All laminates by PCB manufacturer that have UL 94V-0 engineered to hold the rating for all the layers are ideal from compliance point of view.

Stackup Construction

Avoid complex structures if possible and its much better to keep constructions symmetric and balanced. Do not attempt use large varieties of material through the cross section – fire ratings may vary by large margins that cause failures. Another challenge with a high number of interfaces from mixed cores and prepregs with different chemistry is also witnessed.

Raising the overall board thickness may improve the flame resistance but check to ensure this does not introduce delamination problem during lamination while maintaining UL 94V-0 rating.

Bonding Film Types

As much as FR-4 material class, regular bondplies may not attain V-0. To achieve 94V-0 construction without affecting the issue of lamination, flame retardant films containing particular solutions to the PVB are used. Numerous have been proposed for high Tg, fracture toughness, adhesion and rheology.

Limit the use of bonding films as much as possible. Construction process to be confirmed for high layer count boards that are being rated 94V-0.

Conclusion

As a result, it indicated that only the best techniques to design product safety can produce hazel free printed circuit boards with 94V-0 flammability conformance. Choosing the proper materials, assessing construction formations, and directly engaging with the fabrication providers guarantee the end product achieves the highest levels of flame resistance rates per UL 94V.

Due to the raised concerns over consumer protection and the essential consumer safety coupled with the fire risks associated with electrical and electronic products, PCB substrates used in the aforementioned devices have to undertake third party tests to the highest nonflammable standards. Boards conforming to the 94V-0 class offer huge improvements in fire retardation, risk attenuation, and threat escape.

Applying superior flame class fire resistance to circuit card applications, it should be considered a basic prerequisite where selecting the PCB fabrication service due to settling for the highest standard UL 94V-0 protection for the final product as well as the consumer.