What is RoHS Circuit Board: Definition, History and Details

What is a RoHS Circuit Board?

A RoHS (Restriction of Hazardous Substances) circuit board complies with the RoHS directive, a standard set by the European Union to limit the use of certain hazardous materials in electronic and electrical equipment. RoHS-compliant circuit boards are manufactured without the use of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated diphenyl ethers (PBDE), and four different phthalates. This compliance is crucial for reducing environmental impact and enhancing user safety.

History of RoHS

Origins and Initial Implementation

The RoHS directive originated in the European Union, introduced as part of a growing global concern over environmental sustainability and public health. Officially known as Directive 2002/95/EC, it was adopted in February 2003 and put into effect on July 1, 2006. The primary aim was to restrict the use of six hazardous materials found in electronic and electrical equipment. This initiative was a response to the escalating volumes of electronic waste, which were contributing to soil and water contamination due to the leaching of toxic substances.

Expansion and Revisions

Over the years, the RoHS directive has undergone several revisions to widen its scope and increase its effectiveness. The most significant revision came with RoHS 2 (Directive 2011/65/EU), adopted in 2011, which expanded the coverage to all electronic equipment, cables, and spare parts. RoHS 2 also brought in CE marking, making compliance a mandatory aspect of the CE marking process. Additionally, it laid down clearer guidelines for compliance and documentation.

Inclusion of More Substances

Another major revision was the introduction of RoHS 3 (Directive 2015/863), which added four phthalates to the list of restricted substances. This change, effective since July 2019, signified the directive’s ongoing evolution to encompass a broader range of hazardous materials. These additions were based on scientific evidence and consultations, reflecting the EU’s commitment to continually updating the legislation in line with technological advances and environmental research.

Global Influence and Adoption

The RoHS directive has had a considerable influence globally, setting a standard that many countries outside the EU have chosen to emulate. Nations across the world have implemented similar regulations, adapting the core principles of RoHS to their environmental and health safety strategies. This widespread adoption underscores the directive’s significant impact on global electronic and electrical manufacturing practices.

Driving Change in the Electronics Industry

The introduction and evolution of the RoHS directive have been pivotal in driving change within the electronics industry. It has pushed manufacturers to innovate and find safer, more sustainable materials and processes. The directive’s influence extends beyond compliance, as it has fostered a greater awareness of environmental responsibility and consumer safety in the electronics sector.

Substances Restricted Under RoHS Guidelines

Initial Set of Restricted Substances

• Lead (Pb): Once widely used in solder and electronic components, lead can cause numerous health issues, including neurological damage.
• Mercury (Hg): Used in certain types of batteries and lighting, mercury is toxic to the nervous system and kidneys.
• Cadmium (Cd): Found in some semiconductors and resistors, cadmium is a carcinogen and harmful to the environment.
• Hexavalent Chromium (Cr(VI)): Used for corrosion protection and in pigments, hexavalent chromium is known for its carcinogenic properties.
• Polybrominated Biphenyls (PBB): Formerly used as flame retardants in plastics, PBBs can disrupt endocrine functions and are persistent in the environment.
• Polybrominated Diphenyl Ethers (PBDE): Also used for flame retardancy in plastics, PBDEs can accumulate in humans and animals, leading to neurological and thyroid issues.

Additional Substances Restricted in Later Revisions

• Bis(2-Ethylhexyl) phthalate (DEHP): A common plasticizer in PVC, DEHP can affect human fertility and is harmful to aquatic life.
• Butyl Benzyl phthalate (BBP): Used in plastics and adhesives, BBP is a reproductive toxin and can cause developmental issues in children.
• Dibutyl phthalate (DBP): Found in some electronics as a plasticizer, DBP is a reproductive toxin and can also affect the kidneys and liver.
• Diisobutyl phthalate (DIBP): Similar to DBP, DIBP is used in various plastic and rubber products and poses similar health risks.

Continued Monitoring and Assessment

The list of restricted substances under the RoHS guidelines is subject to ongoing review and assessment. As scientific understanding and environmental awareness evolve, additional substances may be considered for restriction to ensure the continued protection of human health and the environment from hazardous electronic waste.

RoHS Requirements in PCB Manufacturing

Adopting Lead-Free Solder

One of the most significant changes in PCB manufacturing due to RoHS is the shift to lead-free solder. Traditional tin-lead solder is replaced with alternatives like tin-silver-copper (SAC) alloys. This transition requires adjustments in the soldering process, including higher melting points, which can affect the thermal profiles during PCB assembly.

Lead-Free Surface Finishes

RoHS compliance also means using lead-free surface finishes on PCBs. Common alternatives include Immersion Silver (Ag), Electroless Nickel Immersion Gold (ENIG), and Organic Solderability Preservatives (OSP). Each of these finishes offers different benefits and challenges, and the choice depends on factors like cost, shelf life, and the intended application of the PCB.

Eliminating Other Hazardous Substances

Beyond lead, RoHS restricts other substances like mercury, cadmium, and hexavalent chromium. Manufacturers must ensure that none of these substances are present in any of the components used in PCBs, including laminates, connectors, and wires. This often requires thorough testing and certification from component suppliers.

Component Sourcing and Verification

Ensuring RoHS compliance requires careful sourcing of components. Manufacturers must work closely with suppliers to obtain RoHS-compliant parts and materials. This often involves rigorous testing and documentation to verify compliance. Additionally, manufacturers need to establish traceability systems to track the compliance status of each component used in their PCBs.

Compliance Certification and Labeling

Manufacturers must not only comply with RoHS standards but also demonstrate compliance through proper documentation and labeling. PCBs that meet RoHS requirements are often labeled with a RoHS compliance mark. Additionally, manufacturers need to maintain records and provide documentation, such as a Declaration of Conformity, to prove compliance during audits or inspections.

Continual Monitoring and Adaptation

The RoHS directive is subject to updates and revisions, and manufacturers must stay informed about these changes to maintain compliance. This includes keeping up with new restricted substances, changes in limit values, and any new exemptions. Continual monitoring and adaptation to these regulations are essential for PCB manufacturers to remain compliant and competitive in the global market.

Identification of RoHS Boards

RoHS Compliance Markings

One of the primary ways to identify RoHS-compliant circuit boards is through specific markings. These often include a “RoHS Compliant” logo or the RoHS symbol, which consists of a green circle with a check mark. These markings are typically found on the PCB itself or sometimes on the packaging. They serve as a quick visual confirmation that the board adheres to RoHS standards.

Documentation and Certificates of Compliance

Manufacturers usually provide documentation certifying RoHS compliance. This can include a Declaration of Conformity, certificates from third-party testing agencies, or detailed material reports. Such documents are essential for audits and for businesses that need to ensure their entire supply chain is RoHS compliant.

Supplier Declarations

For components sourced from external suppliers, declarations or certifications of RoHS compliance are crucial. These declarations are part of the supply chain documentation, ensuring that all components used in the PCB are compliant with RoHS standards.

Material Testing and Analysis

In cases where compliance markings or documentation are not available, material testing can be conducted. Techniques like X-ray fluorescence (XRF) analysis can detect the presence of restricted substances like lead or mercury in the PCB materials. Such tests are often used by manufacturers for internal quality control and by third parties for verification purposes.

RoHS Compliant Component Sourcing

Identification also involves ensuring that all components soldered onto the board are RoHS compliant. This includes integrated circuits, resistors, capacitors, and any other electronic components. Manufacturers need to source these parts from trusted suppliers who guarantee RoHS compliance.

Traceability Systems

Effective traceability systems are key to identifying and verifying RoHS compliance. Manufacturers often implement tracking systems that log the compliance status of each component and material used in their PCBs. This traceability not only aids in compliance management but also in responding to customer inquiries and regulatory demands.