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1. Definition and Standards of the Flammability Rating

In high-frequency PCBs, the flammability rating is an indicator that measures the burning characteristics of PCB materials."Flammability ratings are not just numbers; they represent a commitment to safety and performance in high-frequency PCB applications." A common standard for flammability ratings is UL 94. UL 94 is a standard developed by Underwriters Laboratories (UL) to evaluate the flammability of plastic materials. According to this standard, materials are classified into different flammability levels such as V-0, V-1, and V-2.

For example, V-0 rated materials are self-extinguishing, meaning that in vertical burning tests, the flame extinguishes within a specified time (usually 10 seconds), and there are no burning drops that could cause secondary ignition. V-1 rated materials have a longer extinguishment time under the same test conditions and allow for a small amount of burning drops. V-2 rated materials burn relatively quickly, and the presence of burning drops may be more pronounced.

2. Importance of Flammability Rating

Using PCBs with appropriate flammability ratings is crucial for safety in electronic devices, especially those that generate heat or operate in fire-prone environments, such as power modules and industrial control equipment. Low flammability ratings can lead to rapid fire spread, posing serious safety risks. Additionally, many countries have regulations that require PCB materials to meet specific flammability standards to ensure safety during normal use and in exceptional situations, like short circuits.

3.Influencing Factors

3.1Composition of Materials

The composition of materials is a key factor affecting flammability ratings. For high-frequency PCBs, the chemical composition of substrate materials (such as FR-4, PTFE, etc.) varies, which impacts their flammability. For instance, some FR-4 substrate materials that contain flame retardants may have higher flammability ratings compared to standard FR-4 materials.

3.2 Manufacturing Processes

Manufacturing processes also influence flammability ratings. For example, if the processing of PCBs, such as drilling and etching, is not handled properly, it can damage the flame-retardant layer on the material's surface or introduce flammable impurities, thereby reducing the material's flammability rating.

4. Recommend Rogers RO4835 High - Frequency PCB

Significantly improved oxidation resistance compared to traditional thermoset microwave materials, RO4835 PCB is designed for performance sensitive, high volume applications.

Low loss(DF of 0.0037 at 10 GHz)

• Excellent electrical performance allows application with higher operating frequencies.

• Ideal for automotive applications.

Tight dielectric constant tolerance (DK of 3.48 +/- 0.05)

• Controlled impedance transmission lines

Lead-free process compatible

• No blistering or delamination

Low Z-axis expansion

• Reliable plated through holes(PTH)

Low in-plane expansion coefficient

• Remains stable over an entire range of circuit processing temperatures

CAF resistant

4.2 Typical Applications

• Automotive Radar and Sensors

• Point-to point Microwave

• Power Amplifiers

• Phased - Array Radar

• RF Components

5. Recap

It is crucial to be extremely cautious when selecting the appropriate flammability rating for high-frequency PCBs. As the saying goes，"In high-frequency applications, flammability ratings safeguard not only the circuit but also the end-user."

Founded in 2003, Shenzhen Bicheng Electronics Technology Co., Ltd is an established high frequency PCB supplier and exporter in Shenzhen, China, serving customers worldwide.

We are devoted to delivering high-frequency PCB products and solutions of the highest quality, along with exceptional service!