Product engineers have been designing for conformity to environmental standards for several years. Since 2003, several pieces of legislation have been enacted, including the Directive 2002/95/EC on the Restriction of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS, European Union), The Administrative Measure on the Control of Pollution Caused by Electronic Information Products (China), The Act for Resource Recycling of Electrical and Electronic Equipment and Vehicles (Korea), and The Electronic Waste Recycling Act of 2003 (State of California, USA). Each directive sets limits for the maximum concentration by weight of certain substances that can be present in a product. The product categories that are affected by the legislation are:

• Household Appliances
  
• IT Equipment
  
• Telecommunications Equipment
  
• Consumer Equipment
  
• Lighting Equipment
  
• Toys, Leisure, and Sports Equipment
  
• Automatic Dispensers

Medical devices and monitoring / control instruments are exempt from the current requirements as are certain infrastructure equipment in the telecommunications category.

In spirit, the legislation is addressing the environmental impact of electronics products at the end of their service life, when the product is discarded. Lowering or eliminating the presence of banned materials in products produces lower concentrations of these substances in waste streams. These requirements, which had been considered for many years, are now enforced by law. The risks to a manufacturer that attempts to ship a product that is not in compliance include an import ban as well as other monetary penalties.

Fortunately for product designers, adherence to the new environmental requirements is much easier to achieve as component manufacturers now support a green supply chain. In addition, manufacturing technology advancements have made it possible to produce reliable assemblies with green components and materials. Still, it is critical for product engineers to understand the fundamentals of green design, and more critically, how to authenticate the green compliance of the parts and processes used to produce a product.

The substances which are addressed by the environmental legislation are lead, cadmium, mercury, hexavalent chromium, poly-brominated biphenyls, and poly-brominated diphenyl ethers. These six materials have seen widespread use in a broad range of electronic components. The ban on lead required changing the materials and processes used for soldering. Cadmium was commonly used for connector contacts and in switches. Mercury could be found in relays, switches and flat screen backlighting systems. Hexavalent chromium was used as a corrosion inhibitor for metal housings. Poly-brominated biphenyl and poly-brominated diphenyl ether were added to plastics to reduce the flammability of those materials.

While the source of these banned substances is mostly found in the components, it is the product producer that is responsiblefor compliance to the environmental standard. Theproduct producer introduces the raw material into the marketplace where the consumer, in time, transfers the electronics product into the waste stream. Fortunately for the products producer, the component and material suppliers ultimately provide the supporting documentation forto prove the environmental compliance of an electronics assembly. The elimination of the banned substances from a product can be largely achieved by simply partnering with electronics suppliers who can readily authenticate the materials composition of the components that are used in the final product.

When selecting a component for a design, it is important to check the RoHS status of a device in addition to verifying the electrical characteristics of the device. Component manufacturers and component distributors are increasingly providing this information on web sites and on datasheets. The available information varies from a simple declaration that a device is RoHS compliant to more detailed reporting where the actual concentrations of the banned materials are indicated. Note: A lead free declaration only indicates partial RoHS compliance.

An effort has been made to standardize the exchange of RoHS compliance information between component suppliers and users. A volunteer committee consisting of members of the IPC with representatives from component manufacturers, products companies, electronic assembly manufacturers developed the IPC-1750 standard set. The documents provide specific guidelines to develop consistent data exchange formats to improve environmental data transfer throughout the global supply chain. The standards are available for free from the IPC. Printed circuit boards are also affected by the environmental compliance standards (Figure 1-1). The processing notes found on PCB fabrication drawings traditionally specified PB HASL or lead hot air solder level finishes. Pb HASL cannot be used in RoHS applications. A number of RoHS compliant and Pb free finish options are supported by PCB fabricators. Immersion White Tin, Immersion Silver, Immersion Gold and Pb free HASL are all RoHS compliant finishes.

Finally, the designer must consider the impact of the Pb free soldering process on the selection of components for an electronic assembly. Pb free solder processes require higher temperature reflow profiles. The higher temperature profile may damage or degrade plastic components that were previously compatible with the lead soldering profile.