In modern electronics manufacturing, manufacturers are often highly concerned about two main issues: whether their products pose a threat to the environment and whether they can be harmful to human health. Clearly, these factors are crucial for a company’s reputation and image. Among these, halogens have become a significant focus of attention. In this article, TechSparks will delve into the topic of halogen-free PCB to help you better understand this issue and provide valuable information for your projects.
What Is a Halogen-Free PCB
In accordance with the standards set by IEC 61249-2-21 (International Electrotechnical Commission) and JPCA-ES-2003 (Japan Printed Circuit Board Association), a PCB is classified as halogen-free PCB if the levels of chlorine and bromine fall within 0.09 weight percent or 900 ppm, and the total halogen content is within 0.15 weight percentage or 1500 ppm.
Halogens are a group of elements found in the periodic table, consisting of six components: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). All of these elements, except for Astatine, are commonly used in electronic products. Astatine is a radioactive material and is, therefore, unsuitable for use in electronics.
Here are some examples of halogen-free materials that are employed in PCB manufacturing:
Why Halogen-Containing PCB Are Unpopular
In 2006, regulations were enacted to prohibit the use of halogenated flame retardants, such as polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE). Subsequently, in 2008, the usage of tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) was also banned. These regulations were introduced due to the significant hazards associated with these elements. When halogen-containing PCB materials combust, they release highly toxic gases and unpleasant odors, posing a threat to the health of electronic device users.
While halogens enhance the flame resistance of PCB, since the implementation of these bans, manufacturers have actively sought alternative materials, such as phosphorus and phosphorous-nitrogen compounds. These substitutes are equally effective in providing outstanding flame resistance. In comparison to halogens, halogen-free PCB exhibit superior performance in multiple aspects, including electrical properties, flame resistance, moisture absorption, and chemical resistance. Most importantly, halogen-free PCB do not contain toxic substances, making them more environmentally friendly for recycling and enhancing a company’s reputation, contributing to a positive image in the eyes of customers.
How Do Halogen-Free PCB Achieve Flame Resistance
The most commonly used materials for halogen-free PCB are phosphorus or phosphorus-nitrogen composite flame retardants. These flame retardants, when exposed to heat during combustion, undergo thermal decomposition to produce phosphoric acid or polyphosphoric acid. These products aid in the formation of a char layer that covers the resin’s surface. This char layer acts as an insulator, preventing the resin from further combustion by isolating it from the surrounding air. Additionally, this process releases non-combustible gases, thereby enhancing the flame resistance of the resin.
Applications of Halogen-free PCB
When we emphasize the use of non-halogen materials, it often comes with some cost challenges. Firstly, using alternative materials may introduce additional production costs. Moreover, the production processes may require adjustments and modifications to accommodate these new materials. Special testing methods are also needed to verify whether these materials meet the standards of halogen restrictions.
However, despite the potential extra input involved in the production of halogen-free PCB, it can be highly cost-effective in certain specialized applications. For instance, in equipment like medical diagnostic instruments, patient monitoring devices, and imaging systems, the use of halogen-free PCB ensures the highest safety standards and reliability. This is crucial for maintaining patient health and providing dependable medical information.
Methods of Testing Halogen
To ensure that the substrate is free from halogens, third-party testing and certification are typically required to verify compliance with regulatory standards. Methods for detecting halogens in PCB include:
X-ray Fluorescence (XRF): This is a non-invasive method that uses X-rays to detect trace halogens in PCB substrates.
Combustion Ion Chromatography (CIC): This method involves burning material samples and then measuring the halogen content in the generated gases. It is a relatively accurate method but destroys material samples.
Halogens testing not only helps ensure that PCB materials comply with industry standards but also promotes environmental sustainability and safety. Manufacturers, regulatory bodies, and consumers all recognize that halogens in PCB materials can pose threats to safety and the environment. Therefore, taking appropriate testing measures is crucial.
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