Like many others, it’s common for me to find ants inside at some point during the year. Whether after rain or an extended dry season, a few insects tend to make their way inside to escape the elements. However, I received quite a shock late last year when I discovered an infestation in my closet in the absence of any clear sources of food. I wanted these ants gone immediately, but I was conscientious that any chemical we use to eliminate the ants could affect the garden plants or animals that visit the backyard.
PCB manufacturers face a similar dilemma: what’s the most effective way to prevent pollution with heavy metals and other toxic substances for disposable products? The answer is the Restriction of Hazardous Substances (RoHS) standards, a European Union directive that addresses reducing the toxicity of electronics. For a circuit board to meet these requirements, specific materials and chemistry compliant with RoHS manufacturing regulations must be used during fabrication and assembly. For environmental safety and to prevent fines, recalls, lost sales, and brand damage, it is vital that these ingredients are free from contaminants or dangerous compounds above acceptable limits.
RoHS Manufacturing Protects Environments, People
RoHS regulations are standards that restrict the use of hazardous and toxic materials in electronic products sold or distributed in the European Union. Additionally, the RoHS directive has been partially adopted as a framework in regions outside the EU. As materials used in the production of circuit boards can include hazardous substances, the RoHS regulations specify the acceptable limit of these materials at 1000 parts per million (ppm) by weight. Products exceeding these thresholds cannot be sold in the EU.
| List of RoHS Materials (maximum permitted concentration 0.1%) | |||
| Lead (Pb) | Components of tin-lead solders, especially eutectic tin-lead for low melting point and excellent reliability. | ||
| Mercury (Hg) | Found in some electronic meters and gauges as the conductive element. | ||
| Cadmium (Cd) | Batteries (largely superseded by lithium-ion) and steel electroplating. *Note: cadmium is restricted to 0.01% maximum concentration.* | ||
| Hexavalent chromium (Cr6+) | Dyes, paints, inks, plastics; some anticorrosive uses (including electroplating). | ||
| Polybrominated biphenyls (PBB), Polybrominated diphenyl ether (PBDE) | Flame retardants. | ||
| Bis(2-ethylhexyl phthalate (DEHP) | Dielectric fluid in capacitors. | ||
| Butyl benzyl phthalate (BBP), Dibutyl phthalate (DBP), Diisobutyl phthalate (DIBP) | Plasticizers. | ||
The foremost casualty of the RoHS standards is eutectic tin-lead solder which was a staple of the PCB assembly process. In this step, leaded solders (most often eutectic tin-lead) leveraged the stability and relatively low temperature of tin-lead alloys. However, to limit the environmental accumulation of lead (a toxic heavy metal that can be lethal in small amounts), RoHS outlawed its usage, creating new challenges for manufacturers and long-term electronics reliability.
By specifying the maximum amount of these substances that are allowed in the manufacturing of PCBs, the RoHS regulations help to protect consumers from hazardous materials in a range of products and industries. Maintaining compliance is critical; a partner CM can address these requirements with a comprehensive approach to vetting the relevant aspects of production.
Key Principles of RoHS-Compliant Manufacturing of PCBAs
RoHS impacts the entire scope of manufacturing as the unintentional inclusion or byproduct of non-RoHS-compliant materials can result in costly rectification. Most, if not all, of the steps of the PCB manufacturing process, are impacted when complying with RoHS requirements.
However, three key concepts form the bedrock of RoHS-compliant PCB manufacturing:
- Materials: The most basic requirement for manufacturing a RoHS-compliant PCB is using compliant materials. For example, since RoHS restricted the use of lead in solder, it spurred the adoption of new materials with excellent thermal properties to satisfy the need for lead-free solder. All of the materials and chemicals used by a CM in the assembly of your board must be RoHS compliant.
- Processes: Contaminating RoHS chemistry and materials with non-RoHS substances will impede compliance. Processes must be in place to prevent the inclusion of offending materials above acceptable limits. This means having documented procedures to identify and isolate RoHS-compliant products from non-compliant ones throughout the production process.
- Documentation: All materials used for a PCB must be traceable to meet regulatory requirements. Documentation during manufacturing is crucial to establish records that all materials are RoHS compliant and have not been liable to cross-contamination with non-compliant materials.
Quality CMs ensure PCBs are manufactured with these principles at the forefront; those that understand the importance of these regulations will have the experience and procedures in place to maintain compliance. Larger CMs with volume-driven processes may not be able to guarantee these requirements.
Best Practices for RoHS Manufacturers and Their Partners
The first thing to look for when choosing a contract manufacturer that is RoHS compliant is to make sure they understand and have patterned their processes after the RoHS regulations. This means that they:
- Can source parts and materials from vendors that are fully RoHS compliant.
- Work with fabrication shops that also comply with RoHS standards.
- Store and process RoHS and non-RoHS chemistry and materials separately.
- Document RoHS requirements during quoting and product review.
- Employ process engineers to monitor production and ensure requirements are met.
At VSE, we understand the importance of the RoHS manufacturing regulations, and we are fully set up to work with compliant vendors to ensure that all parts and materials used will pass the RoHS requirements. Since 2006, we have utilized a documented procedure to tightly control the identification and compartmentalization of compliant and non-compliant materials. We know that cross-contamination is a big concern, and we have painstakingly defined and crafted our manufacturing processes to guarantee that all RoHS materials are within acceptable limits. Additionally, we provide RoHS conversion design services on legacy products to make revisions compliant.
