If you have a classic recipe that you like to cook, you know how difficult it is to make without all of its regular ingredients. Everyone knows how it should taste, especially the chef, but replicating that success using a different palette of flavors can be nearly impossible. However, it may be surprising to discover that changing a recipe can be done successfully, in and out of the kitchen.
Twenty years ago, the electronics industry was faced with a similar dilemma when introducing the Restriction of Hazardous Substances directive. The RoHS requirements restricted the use of certain toxic materials during manufacturing, forcing changes in processes, materials, and components used in building electronics. Although this was a difficult change to incorporate, it has since been accomplished successfully by many PCB contract manufacturers. Here, we’ll look at the RoHS PCB manufacturing requirements in place today and how PCB CMs work with these regulations in producing circuit boards.
What is RoHS in Electronics Manufacturing?
The restriction of hazardous substances directive governs materials that are not allowed in the manufacturing of electrical and electronic products sold or used in the European Union. The RoHS compliance guide specifies the substances to be avoided and the categories of products that these substances are restricted from. The restricted materials are judged to be harmful to the environment or dangerous for people exposed to them during manufacturing and recycling. Although there are many substances that the RoHS directive restricts, the one that attracts the most attention is the lead used in PCB solder.
Traditional solder for electronics is a mixture of tin and lead that melts to create a bond between component leads and metal holes or pads on a circuit board. The use of lead in solder lowers its melting point, making it easier to work with, and creates a connection that is less prone to cracking or creating metal whiskers that can short to other connections. However, with the dangers associated with lead, many corporations and the European Union have restricted its use. The solder acceptable for use in RoHS applications is “lead-free” and can be a combination of tin, silver, copper, or other alloys.
Lead-free solder does have some differences between it and regular tin-lead solder that should be noted:
- Lead-free solder melts at a higher temperature, 217°C, as opposed to 183°C.
- Due to the higher melting point, lead-free solders can be more difficult to work with.
- Lead-free solders will produce a joint that is stronger mechanically than lead solder.
- Lead-free solder is more expensive than lead.
- The higher soldering temperatures can negatively impact components, and lead-free rated components are generally used instead.
As you can see, there are both pros and cons to using lead-free solder for circuit boards that must be certified RoHS compliant. Next, we’ll look at how circuit board manufacturers change their production process to work with lead-free solder.
How Circuit Board Manufacturers Support RoHS PCB Assembly
To build a high-quality circuit board that satisfies the requirements of the RoHS directive, PCB contract manufacturers will implement the following processes:
The first step in RoHS compliance is to ensure that the manufacturing staff is fully trained in all the new processes and requirements. This training includes new inventory controls, solder chemistry, manufacturing processes, rework, and inspection.
Work with RoHS compliant PCB fabrication shops
Building a RoHS-compliant circuit board requires starting with a circuit board that was fabricated using acceptable materials and substances. The PCB CM will need to establish working relationships with PCB fabricators that will provide bare board fabs built according to RoHS requirements.
Use separate production lines
Successful PCB CMs will often isolate their no-lead and RoHS compliant production processes from their standard production lines. This separation relieves the need to constantly sanitize and validate the absence of lead from their PCB production tools and equipment when switching between the two processes. Additionally, it makes for a more efficiently run production floor, especially when combined with color-coded and computerized tracking of the two processes.
Precise inventory control
Since RoHS compliance extends to the components and materials used in PCB manufacturing, CMs need to ensure that the customer’s bill of materials (BOM) uses RoHS-compliant parts. The CM must have a tight inventory control process tracking and storing the correct parts throughout the factory to ensure that lead and no-lead parts are not mixed on the same build.
Choosing the Best RoHS Compliant Manufacturer for Your PCB Assembly
While the production process of lead and no-lead soldering is essentially the same, many minute details need the oversight of an experienced PCB CM for success. When you look for a PCB assembly shop for this work, here are some of the questions to keep in mind while you do your research:
- Do they have a defined and documented process for RoHS compliant PCB assembly?
- How much experience do they have building to the RoHS specifications?
- Do they have the engineering and component capabilities to help you make the best design choices for a RoHS compliant board?
- Can they help you transition your legacy designs into new RoHS compliant versions?
At VSE, we fully understand the RoHS directive, and we have been building lead-free circuit boards for our customers for many years. Our equipment and processes have all been carefully orchestrated to support green technology manufacturing, with color-coded carts, racks, bins, and bar-coded parts and materials. Our staff is also well-trained and experienced with all of the RoHS regulations, and we constantly review new editions of the RoHS directive to ensure that we are fully up-to-date with all of the requirements.