How PCBs are Manufactured Sustainably

March 11, 2021 Cadence PCB Solutions

Key Takeaways

  • Reputable PCB manufacturers comply with RoHS, REACH, and other regulatory standards.

  • Selecting the right PCB manufacturer includes viewing their RoHS and REACH compliance information. 

  • Alternative solutions are enabling the PCB manufacturing industry to emphasize sustainability.

Sustainable manufacturing graphic

At one time, the PCB industry’s dedication to the environment seemed questionable. Complicated multi-step manufacturing processes relied on solvents such as glycol ethers and toxic chemicals that included formaldehyde, dimethylformamide, and lead. For example, rinse water from PCB etching processes contained high concentrations of copper, lead, nickel, chromium, and tin. Along with polluting the environment with chemical-filled wastewater and loading landfills down with hazardous waste, the PCB manufacturing process also exposed workers to carcinogens and chemicals that had the potential to cause reproductive harm. 

Fortunately, how PCBs are manufactured has changed over the years. Although much work remains to achieve truly sustainable PCB manufacturing processes, compliance with the Restriction of Hazardous Substances (RoHS) directive and the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) initiative has prompted PCB manufacturers to:

  • abandon the use of toxic chemicals

  • check supply chains for ethical practices

  • discover environment-friendly alternatives for board components

When comparing PCB manufacturers, always check if they show compliance with the RoHS and REACH regulations, as these regulations have enabled the PCB industry to begin working towards a more sustainable future.

The Restriction of Hazardous Substances Directive

Adopted by the European Union during 2003 and expanded during 2011, the RoHS bans the use of toxic substances within circuit boards and has gained global compliance by importers, distributors, and manufacturers. Toxic materials banned by the RoHS include:

  • Lead 

  • Mercury

  • Cadmium 

  • Hexavalent chromium 

  • Polybrominated biphenyls 

  • Polybrominated diphenyl ethers

  • Four classes of phthalates

Along with eliminating those chemicals from PCB manufacturing processes, RoHS compliance also covers any plating or finishes applied to electronic products and involves maintaining documentation about compliance and non-compliance.

While the original RoHS also applies to the components, sub-assemblies, and wiring that connect to PCBs, RoHS 2 covers all electrical/electronic equipment, cables, and components. RoHS 3 lists additional phthalates as hazardous. Compliance with RoHS directives results in the application of a CE mark to products.

The Registration, Evaluation, Authorization, and Restriction of Chemicals Initiative

Like the RoHS, the REACH initiative began with the European Union. However, many jurisdictions in the United States have similar restrictions regarding the use of hazardous chemicals. The U.S. Environmental Protection Agency uses complementary screening methods called the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) and the Risk-Screening Environmental Indicators (RSEI) to quantify environmental impacts.

While compliance with the RoHS regulations restricts the use of hazardous materials in a final product, the REACH initiative controls chemicals used during the manufacturing processes for printed circuit boards, electrical components, and electronic components. Those chemicals are on the list of Substances of Very High Concern (SHVC) and include:

  • Dibutyl phthalate 

  • Di (2-ethylhexyl) phthalate

  • Hexabromocylclododecane  

  • Butyl benzyl phthalate

  • Tributyltin oxide

In contrast to the RoHS, REACH applies to the supply chain as well as to manufacturers. A supplier must notify a PCB manufacturer that bare circuit boards, assembled circuit boards, housings, components, sub-assemblies, and finished products comply with the REACH initiative.

How PCBs are Manufactured Today

Although each of the banned chemicals offered advantages for PCB manufacturing, the industry has found alternatives that provide the same (or even better) performance and reliability. Rather than use lead-tin solder, for example, PCB manufacturing processes rely on tin-silver-copper solder. Even though silver is a hazardous material, the small amount used in tin-silver-copper solder does not have a harmful environmental impact. 

Along with tin-silver-solder, PCB manufacturers also use silicone and polyamide polymer adhesives that include small embedded flakes of silver to achieve high conductivity and tight bonding to circuit boards. Other lead-free solder technologies include electroplating, solder ball formation technologies, and solder dipping technologies. 

The switch to lead-free soldering also prompted design teams and manufacturers to collaborate to achieve simplified layouts with tightly packed components. As a result, manufacturers gained the ability to fabricate smaller boards at lower costs.

Paper PCBs Provide Another Alternative Solution

Aside from the RoHS-banned chemicals, PCB manufacturers have begun moving away from the use of glycol ethers, formaldehyde, and dimethylformamide in production processes. 

Paper PCBs (P-PCBs) that mount components on flexible paper substrates combine reliable functionality with environmentally-friendly, renewable materials. P-PCBs rely on lead-free, electrically conductive adhesives that connect surface mounted components to tin or zinc conductors. These conductors transfer to the paper PCB through screen printing, 3-D printing, or inkjet printing.

Prototype paper PCBs have demonstrated the same functionality as traditional circuit boards in terms of electrical conductivity, reliability, multilayer capabilities, and resistance loss. A typical P-PCB fabrication process involves using additive technologies to print the ECA onto each layer of paper substrate. The next step includes curing the adhesive, aligning the layer-by-layer circuits, and then adhering the layers to one another with pressure-sensitive adhesives. After the punching of vias through each layer, the process continues with mounting surface-mount devices to the conductors.

While paper PCBs remain in the prototype stage, developments in advanced paper materials promise to deliver properties that allow the use of paper-based technologies for high-speed, high-density applications. The advancements in paper materials offset the loss of properties seen with RoHS-banned materials through improved electrical and thermal conductivity, enhanced fire resistance, moisture resistance, and improved dielectric properties.

While the industry has come far in terms of how PCBs are manufactured, we still have a long way to go towards creating an environmentally-friendly manufacturing process. For tools to assist you with your next sustainable design, visit Cadence’s PCB Design and Analysis Software page. The Allegro PCB Editor helps you create accurate, quality designs. You can also use InspectAR to accurately assess and improve PCBs using augmented reality and intuitive interaction. Inspecting, debugging, reworking, and assembling PCBs has never been faster or easier.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

 

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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