An Overview of Halogen-Free Requirements for PCBs

I. Introduction

In accordance with the requirements of IEC 61249-2-21, maximum halogen content limits are specified for electronic soldering materials, resins, and reinforcing materials used in the manufacture of halogen-free printed circuit boards. Halogen-free manufacturing has become yet another “green revolution” in the electronics industry since the implementation of the RoHS Directive on July 1, 2006.

II. The Concept of Halogens

HalogenIt is a Greek word that originally meant “salty, alkaline land.” The halogens, or halogen elements, include five chemical elements: fluorine, chlorine, bromine, iodine, and astatine. In the electronics industry, however, people are primarily interested in bromine and chlorine.

III. Why Go Halogen-Free?

Electronic waste and plastic products containing bromine and chlorine compounds contain halogen-based flame retardants and PVC. When these products are discarded and incinerated, they readily produce harmful substances such as dioxins and acidic gases (HCl), which, through bioaccumulation, pose risks to the environment and human health. The United Nations Environment Programme has classified them as persistent organic pollutants.

Halogenated compounds are widely found in printed circuit boards, solder masks, molding compounds, connectors, and other common electronic products. For example, halogen-containing materials are present in flame retardants used in printed circuit boards, and the toxicity of PBB and PBDE is a major concern. When halogen-containing circuit boards and electronic products undergo incomplete combustion, they produce numerous byproducts, including dioxins and furan-like compounds, as well as acidic or corrosive gases, all of which pose potential hazards to the environment and human health.

Currently, most power and telecommunications cables contain halogens, which release toxic chemical fumes when burned. In the event of a fire, the acidic gases produced by burning cables can damage people’s noses, mouths, and throats, and the smoke can easily disorient people, making it difficult to escape the fire scene. Consequently, the EU’s RoHS Directive prohibits the use of PBB and PBDE—two halogen-containing materials—in printed circuit boards. There are now efforts to restrict the use of all halogen-containing materials in electronic devices. Proponents argue that when electronic devices are incinerated, brominated materials produce highly toxic dioxins. Their call to ban halogen-containing materials goes beyond the RoHS’s original provisions, which restricted only PBB and PBDE. The shift toward halogen-free materials may become another “green revolution” in the electronics industry following the implementation of the RoHS (Restriction of Hazardous Substances) Directive on July 1, 2006.

Compared to the hazards posed by halogenated compounds, the six hazardous substances restricted by the RoHS Directive (four heavy metals—lead (Pb), cadmium (Cd), mercury (Hg), and hexavalent chromium (Cr⁶⁺)—and two flame retardants—polybrominated diphenyl ethers (PBDE) and polybrominated biphenyls (PBB)) are even more alarming. Among these, lead causes direct damage to the nervous system; cadmium causes damage to the bones, kidneys, and respiratory system; mercury causes damage to the central nervous system and kidneys; hexavalent chromium can cause genetic defects; and polybrominated diphenyl ethers (PBDE) and polybrominated biphenyls (PBB) are potent carcinogens and teratogens. From lead-free and RoHS to halogen-free, and on to Norway’s PoHS directive banning the use of 18 hazardous substances, increasingly stringent environmental requirements for materials not only significantly reduce environmental pollution caused by electronic products but also effectively safeguard our health.

Market Drivers for Halogen Elimination:

1. Concerns about the environment and health: As environmental awareness continues to grow, people are paying closer attention to the potential harm that hazardous substances pose to the environment and human health.
2. Certain brominated flame retardants are indeed toxic: The toxicity of brominated flame retardants, such as polybrominated biphenyls and polybrominated diphenyl ethers, has drawn widespread attention.
3. Many brominated flame retardants are structurally similar to polychlorinated biphenyls (PCBs), which are known to be toxic: Concerns that brominated flame retardants may produce harmful substances similar to polychlorinated biphenyls.
4. This has sparked concerns about all brominated flame retardants: To be on the safe side, people tend to avoid using any materials that contain halogens.
5. Toxic byproducts generated during the incineration of end-of-life products: When electronic products reach the end of their useful life, incineration may produce hazardous byproducts.
6. Incomplete combustion of halogens produces dioxins: During incomplete combustion, halogens may produce dioxins, which are extremely harmful substances.
7. The open-air burning of discarded electronics is widespread worldwide: Improper disposal of electronic waste may result in the release of hazardous substances.
8. Environmental organizations strongly oppose brominated flame retardants: Many environmental organizations actively advocate for halogen-free manufacturing.
9. Driven by environmental organizations, OEMs are seeking halogen-free solutions and extending this requirement throughout their supply chains.
10. Announcements from Major OEMs Regarding the Elimination of Bromides: Several well-known electronics manufacturers have actively announced that their products will no longer contain bromides.

IV. Halogen-Free Regulations and Their Provisions

According to various regulations and standards, the acceptable halogen content is as follows:

• Bromine: 900 ppm
• Chlorine: 900 ppm
• The total halogen content must not exceed 1,500 ppm.

Requirements for Halogen-Free Manufacturing:

• IPC Low-Halogen Electronics Standards Working Group 4-33A & JEDEC JC14 Committee: All PCB substrates must meet the low-halogen bromine and chlorine requirements defined in the IPC-4101B standard.
• RoHS II is currently being revised.
• Given the wide variety of halogen sources and the minimal environmental impact of low halogen levels, most organizations adopt the concentration limits specified by the International Electrochemical Commission (IEC) as requirements for their final assembled products.

V. Testing and Analysis of Halogen-Free Products

To verify that the materials used in circuit boards are halogen-free, manufacturers must conduct an incineration test and then use ion chromatography to determine the presence of halogen elements. During combustion, brominated activator materials decompose; in these materials, the bromine atoms form bromide molecules through covalent bonds at room temperature.

Test methods include:

1. prEN 14582 Characterization of Waste—Halogen and Sulfur Content—Oxygen Combustion in Closed Systems and Determination Method
   • Method A: Calorimetric bomb method
   • Method B: Schoniger flask combustion method
2. IEC 61189-2 Test Methods for Electronic Materials, Printed Circuit Boards, and Interconnect Structures and Assemblies—Part 2: TEST 2C12—Test Method for Interconnect Structures
3. JPCA-ES-01-2003 Test Methods for Halogen-Free Materials
4. IPC TM-650 (Number 2.3.41)

VI. Challenges and Opportunities Facing Halogen-Free Manufacturing Processes

The move toward halogen-free manufacturing presents both challenges and opportunities for Chinese companies. Although we have been in a passive role in this environmental movement, we can still learn from the experience. Having successfully navigated the transition to lead-free manufacturing, we now face the challenge of halogen-free manufacturing. If we can proactively address halogen-free manufacturing, we will be better prepared to meet any new environmental requirements that may arise in the future.

Therefore, halogen-free manufacturing processes present both challenges and opportunities. They can encourage companies to adopt more environmentally friendly manufacturing methods, reduce their environmental impact, and enhance the market competitiveness of their products. At the same time, they also require companies to continuously innovate and seek alternative materials and processes to meet environmental standards.

Conclusion

As global environmental standards continue to rise, halogen-free manufacturing has become an inevitable trend in the electronics industry. Eliminating halogens reduces emissions of harmful substances, thereby protecting the environment and human health. Therefore, halogen-free manufacturing is not only a regulatory requirement but also a key direction for corporate sustainable development. By actively addressing the challenges of halogen-free processes, companies can achieve more environmentally friendly production while also unlocking broader market opportunities.

Frequently Asked Questions

Q1. What are the issues associated with halogens in electronics manufacturing?

Halogens may lead to the release of harmful substances during electronics manufacturing, posing potential risks to the environment and human health.

Q2. Why does the electronics industry need to adopt halogen-free manufacturing?

Halogen-free manufacturing helps reduce emissions of harmful substances, protects the environment and human health, and meets global environmental protection requirements.

Q3. What are the regulations and standards for halogen-free manufacturing?

Various regulations and standards specify limits on halogen content, such as 900 ppm for bromine, 900 ppm for chlorine, and a maximum total halogen content of 1,500 ppm.

Q4. Does the halogen-free manufacturing process present business opportunities?

Yes, halogen-free manufacturing processes can enhance a product’s market competitiveness, meet environmental requirements, and contribute to a company’s sustainable development.

Q5. Why is the halogen-free manufacturing process both a challenge and an opportunity for Chinese companies?

Halogen-free manufacturing processes pose challenges for Chinese companies, but they can also encourage them to adopt more environmentally friendly manufacturing methods and enhance their market competitiveness.

Further Reading：Analysis and Solutions to Humidity Issues in Printed Circuit Boards · How to Avoid Common Mistakes in Printed Circuit Board Design