PCBs are being mass-produced every day and are also discarded at a rate higher than ever before. While manufacturing RoHS PCBs might not harm the environment quite as much, discarding the PCB without proper dumping causes severe pollution, especially PCBs with toxic materials. However, today’s RoHS PCBs do not cause as much toxicity after dumping as PCBs of previous decades did. Frequent contact in the operation of previous decades PCBs are considered hazardous. The control of hazardous materials in RoHS PCB can be credited to policies and regulations like RoHS and REACH. These PCBs are also called RoHS PCBs.
What is RoHS on Circuit Boards?
RoHS or Restriction of Hazardous Substances is a compliance standard first adopted by the European Union which primarily prohibits the use of heavy metals mercury, lead, cadmium, hexavalent chromium and six other compounds in the manufacturing and operations of RoHS PCB and other electronic and electrical equipment. This ensures the RoHS PCB does not cause toxicity after dumping or while in operation. These metals are, however, still used in electricals and electronics, but if even a component in the appliance has a higher amount of restricted material than the permissible limit, then the whole appliance will be declared as RoHS non-compliant.
Some of the Materials Forbidden in RoHS
These 6 materials were restricted in the RoHS 1 list. The list was amended in 2019 in the RoHS 3 list of materials which have 10 types of restricted materials. All of the mentioned materials are restricted to 0.1% each (except cadmium which is 0.01) of the mass of the component they are used in RoHS PCBs.
- Lead or Pb: It is the last of non-radioactive metals in the periodic table or in other words, it is the heaviest non-radioactive metal. However, it is used for reducing the melting point of an alloy. The problem with lead is that it chemically reassembles with calcium meaning, if absorbed in the human body, it gets stored in bones. It can also cause severe nervous system damage in workers who hand RoHS PCBs.
- Hexavalent Chromium or Cr(VI): It is a heavy metal used to make metal contacts lustrous and corrosion-free. Hexavalent chromium is a severe carcinogenic material, so it is strictly regulated in RoHS PCBs.
- Mercury or Hg: It is the metal which remains liquid at room temperature and was used in batteries and relays. Mercury which is forbidden in RoHS PCBs gets quickly absorbed by the skin and severely damages the nervous system.
- Cadmium or Cd: It is a heavy metal that was earlier used in batteries and some special solders. It is considered as a severe carcinogenic material. That’s why it is restricted in RoHS PCBs.
- Polybrominated Biphenyls or PBBs: It is a flame retardant material that was earlier used in plastics of connectors and the substrate material of the PCB. Polybrominated Biphenyls which are banned in RoHS PCBs cause severe damage to the nervous system.
- Polybrominated Diphenyl Ether or PBDE: It was used in laminates of the PCB material for their fire retardant properties. It damages the nervous system and was found to damage the thyroid gland. That’s why RoHS PCBs do not use PBDEs to ensure compliance.
Possible Non-RoHS Materials in Circuit Boards
When RoHS was introduced, there were two electronics that were majorly affected. They were batteries and PCBs. From fabrication to assembly, earlier PCBs used RoHS-restricted materials in every step of manufacturing and assembly of circuit boards. The PCB elements which were affected by RoHS were –
- Solder: Soldering is an essential part of RoHS circuit board assembly. Soldering wires and other solders without PCB RoHS compliance were primarily made of lead alloy. Lead solders were cheap, had low melting points and had high conductivity which led to mass production and usage of lead-based solders.
- Flux: Flux which was used in PCB assembly earlier used heavy metals and halogenated materials. But today RoHS circuit board assembly is strictly comply with PCB RoHS compliance.
- Surface Finishes: Surface finish gives a solderable slot on the RoHS circuit board for the components. Earlier, HASL or Hot air solder levelling was most widely used for surface finishes that used Pb-Sn alloy (Lead and tin alloy).
- Substrate Material: The substrate of the PCB without PCB RoHS compliance was made from various flame-retardant materials like PBB (Polybrominated Biphenyls). The substrate of the PCB without PCB RoHS compliance also contained other halogenated compounds which made the PCBs a major pollutant.
- ICs: Many ICs use lead, cadmium and mercury for their manufacturing. For example, the Intel Pentium processor used lead for attaching the silicon die to the IC package. Earlier the pins of the ICs would be coated with hexavalent chromium to avoid corrosion.
- Connectors: Many connectors on the PCBs without PCB RoHS compliance would use hexavalent chromium to avoid corrosion and loss of lustre.
As observed from the above list, almost every part of old PCBs used toxic materials. Rapid industrialisation and automation demanded more RoHS circuit boards to be manufactured. To appreciate the importance of RoHS one must understand the scale at which the RoHS circuit boards were manufactured and are being manufactured now.
How to Make a RoHS-Compliant PCB?
If the product you are designing is to be sold in Europe or even to non-European governmental organisations, PCB RoHS compliance is a must or even if RoHS is not demanded you should try to comply with RoHS for the sake of the environment. To make a RoHS PCB board complaint the following things should be ensured –
- Choose RoHS ICs: First and foremost, choose the ICs well. All the efforts for maintaining RoHS compliance will be wasted even if one IC on the RoHS PCB board is non-compliant with RoHS standards. All the ICs and the components on the RoHS PCB boards are required to be RoHS compliant which can be confirmed by the manufacturer’s datasheet of the component. Even the data sheet of connectors such as berg strips must be checked for RoHS compliance. Maintaining the records of compliance such as datasheets is recommended.
- Choose RoHS PCB Materials: When choosing the RoHS PCB board substrate or the material for dielectric make sure that it is RoHS compliant. While most of the materials available with RoHS PCB board fabricators are RoHS compliant it is much better to be sure.
- Surface Finish to be RoHS Compliant: Surface finishes are the part where many people make mistakes. Surface finishes are of many types like HASL (hot air solder levelling), and ENIG ( Electroless Nickel Immersion Gold, Immersion Tin and Hard Gold, out of which HASL is the cheapest and the only finish violating RoHS. Now what many manufacturers do is mention HASL instead of Lead HASL which leads to confusion. RoHS-compliant HASL will be named as Lead-free HASL.
- Use Lead-Free Solder: For soldering, lead-free solders are required to be used for RoHS compliance. Lead-free solder is a bit more expensive and has a higher melting point than lead solder.
- RoHS-Compliant PCB Fabrication Process: It is important to confirm with the vendor if their RoHS PCB board fabrication or manufacturing is RoHS-compliant.
- Full Supply Chain be RoHS Compliance: After the RoHS PCB board is fabricated it is important to maintain all the documents and compliance proof of the full supply chain.
RoHS-compliant fabrications are now easily available and are common among vendors to manufacture RoHS-compliant PCBs. However, still one must be vigilant with all the steps involved in the fabrication and assembly of a RoHS-compliant PCB. Even if you are unable to prove the compliance of even a small part of the RoHS PCB board, the whole PCB gets rejected on environmental grounds, especially in the European market.
Benefits of Using RoHS-Compliant PCBs
- Environmental Responsibility: RoHS-compliant PCBs ensure minimum toxicity when deployed or dumped. It helps in the conservation of natural resources like soil and water which helps maintain the environment and ecosystem. RoHS not only ensures safer dumping but also makes the PCB through RoHS PCB assembly recyclable.
- Safety and Health: Materials banned under RoHS are extremely toxic and harmful to health. Extended exposure to such materials causes cancer, neurological damage and other long-term health problems which are generally untreatable. Mercury lead and cadmium are especially infamous for heavy metal poisoning. RoHS PCB assembly reduces these health risks.
- Future-Proof: Standards like RoHS are only going to get stricter and more widely demanded. It is much better to comply with such standards than to face hassle in future. It might cost a bit more initially but certainly cost less than re-engineering the RoHS PCB assembly.
- Market Access: For selling any electronics in the European Union RoHS compliance is a must. Even some government organisations of various countries demand RoHS compliance in their tenders. To even apply such tenders, PCB RoHS compliances are a must.
- Brand Reputation: Compliance with RoHS with all your products creates trust and confidence in the brand. Many big organisations and end consumers prefer environmentally friendly and safe products over potential health hazards. RoHS compliant PCB assembly ensures health and the environment.
- Marketing: A RoHS-compliant product can be marketed as a lead-free and safe product which can attract consumers and businesses. Stating the role of RoHS compliant PCB assembly in marketing materials can also enhance the product’s appeal to environmentally conscious buyers.
Although PCB RoHS compliance is not compulsory for all sectors, it is still preferred over non-RoHS-compliant products. One crucial point to note is while the PCB might be RoHS compliant it cannot be marketed as an eco-friendly product. If RoHS is complied with by the PCB, be sure to add a lead-free symbol and the RoHS symbol using a top or bottom overlay to denote that the PCB is RoHS compliant.
