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Halogen Free PCB: A Complete Guide to Green Electronics

Views: 1031 Author: Site Editor Publish Time: 2023-08-14 Origin: Site

The potential health risks associated with elevated concentrations of fluorine and chlorine in circuit boards led to the development of halogen free PCBs by the IEC. Given that electronics frequently incorporate materials with significant halogen content, achieving a halogen-free PCB entails minimizing the utilization of these substances or seeking suitable replacements. The level of halogen freedom in your PCB circuits should be determined based on your specific requirements and priorities.

halogen free PCB

What is Halogen-free PCB

A Halogen-free PCB is a type of circuit board that is manufactured without the use of halogen-containing materials, specifically halogenated flame retardants. Halogens are a group of chemical elements that include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). In the context of electronics manufacturing, halogens are often used as flame retardants in materials like PCB substrates, solder masks, and other components.

Standards such as IEC 61249-2-21 and JPCA-ES-01-2003 specify that halogen-free copper clads should have chlorine and bromine levels below 0.09 wt% (900ppm) and their combined total under 0.15 wt% (1500ppm). Thus, halogen-free PCBs are boards with chlorine below 0.09 wt% (900ppm), bromine below 0.09 wt% (900ppm), and overall halogens below 0.15 wt% (1500ppm).

Advantages of halogen-free PCBs

Halogen free PCBs offer several key advantages compared to traditional PCBs that use halogen-containing materials. These advantages make halogen-free PCBs a preferable choice, especially in environmentally conscious and regulatory-driven industries. Here are some of the significant benefits:

  • Enhanced Electrical Insulation: Halogen-free PCB substrates exhibit superior electrical insulation due to the reduced polarity of P (phosphorus) and N (nitrogen) compared to halogens. This results in reduced electric shock susceptibility, making halogen-free PCBs suitable for applications requiring higher insulation resistance.

  • Higher Glass Transition Temperature (TG): Halogen-free PCBs boast a higher TG, indicating they can operate at elevated temperatures. This attribute makes them a better fit for high-power applications, where increased temperature tolerance is essential.

  • Lower Moisture Absorption: Halogen-free PCBs, with P and N compound epoxy resins, have fewer opportunities to form hydrogen bonds with water than halogen epoxy resins. This results in lower moisture absorption rates, making them more resilient in environments with moisture, albeit on a smaller scale.

  • Enhanced Stability at High Temperatures: The higher monomer molecular weight of halogen-free PCBs translates to reduced molecular mobility, leading to improved thermal stability. This characteristic curtails the extent of expansion under heat, ensuring a higher degree of overall stability.

Disadvantages of halogen free PCBs

  • Cost: Halogen-free materials can be more expensive than traditional halogen-containing materials. This increased cost may impact the overall manufacturing budget, particularly for large-scale production.

  • Limited Material Choices: The range of available halogen-free materials may be more restricted compared to traditional materials, which can limit design flexibility and options.

  • Processing Challenges: Halogen-free materials might have different processing requirements during PCB fabrication, such as higher processing temperatures, longer curing times, or specific handling precautions, leading to potential challenges during manufacturing. Finding a fully competent pcb supplier with the techniques is very important.

What are the Common Substrate Materials Used in Halogen-free PCBs

Several common substrate materials are used in halogen-free PCBs. These materials provide the foundation for the PCB and play a crucial role in determining the board's performance, reliability, and overall environmental impact. Here are some commonly used halogen-free substrate materials:

  • FR-4 Alternatives: Traditional FR-4 (Flame Retardant 4) is a widely used substrate material in PCBs, but it often contains halogenated flame retardants. Halogen-free alternatives to FR-4 are available, such as high-performance laminates designed to meet stringent environmental and safety standards while maintaining compatibility with existing manufacturing processes.

  • Eco-Friendly Laminates: Some PCB manufacturers offer laminates specifically designed to be halogen-free and environmentally friendly. These laminates may incorporate bio-based or recyclable materials, reducing the environmental impact of the PCB.

  • Polyimide (PI): Polyimide is a high-temperature-resistant substrate material that is commonly used in flexible PCBs (FPCBs) and rigid-flex PCBs. Halogen-free versions of polyimide substrates are available, providing both thermal performance and environmental safety.

  • High-Temperature Substrates: For applications that require exceptional thermal performance, halogen-free high-temperature substrate materials, such as polytetrafluoroethylene (PTFE) and ceramic-filled laminates, can be utilized.

Related article: A Deep Dive into PCB Laminate Materials

Design Considerations When Using Halogen Free PCB materials

The benefits of adopting halogen-free boards do bring about increased complexity, not only in the manufacturing phase but also in the design process. A prime example lies in the use of halogen-free solder and flux, which can occasionally result in issues like solder graping. This phenomenon occurs when the solder conglomerates into a single large blob instead of being evenly distributed across a connection. To counteract this challenge, a strategic design approach involves leveraging solder mask technology to precisely define the pad. This containment method helps manage the solder paste and reduces the likelihood of defects.

Working with novel materials presents its unique design idiosyncrasies, necessitating effective communication with manufacturers or thorough research before their implementation. Although halogen-free boards are gradually becoming more available, they are still relatively uncommon. It's essential to engage in dialogue with your PCB manufacturer to ascertain their capability to produce PCBs using halogen-free materials.

As time progresses, our growing awareness reveals that many everyday materials harbor potential health risks. This awareness underscores the importance of standards, such as those developed by organizations like the IEC, for halogen-free boards. Understanding the typical sources of halogens (such as BFRs, solvents, and insulation) enables us to identify the elements to replace when transitioning to halogen-free solutions. Different standards permit varying halogen levels and may or may not detect specific types. Thorough preliminary research helps identify potential issues on your PCB. After pinpointing the desired materials, collaborating with the manufacturer and your CM (contract manufacturer) is essential to chart the most effective path forward. This might involve tweaking designs or refining specific manufacturing steps to ensure a successful PCB outcome.

What Are the Applications of Halogen Free PCB

Halogen-free PCBs are versatile and suitable for a wide range of industries that utilize electronic PCB boards, spanning from consumer electronics to industrial automation. Notably, they find significant application in the automotive and mobile phone sectors. While specifications may differ, consulting your manufacturer regarding industry-specific requirements is essential.

These boards are favored by companies demonstrating environmental responsibility, aiming to minimize their carbon footprint and reduce the release of toxins during production. Although halogen-free PCBs can benefit any company, they are particularly prevalent among those committed to sustainability.

If you're considering halogen-free boards for your application but have concerns about compatibility, feel free to reach out to us. Our PCB experts are ready to discuss the distinctions between halogen-free PCBs and traditional boards and how these distinctions may impact your specific product.

About The Author

I am the Engineering and Sales supervisor working in Victorypcb from 2015. During the past years, I have been reponsible for all oversea exhibitions like USA(IPC Apex Expo), Europe(Munich Electronica) and Japan(Nepcon) etc. Our factory founded in 2005, now have 1521 clients all over the world and occupied very good reputation among them.

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