Over the last decade, manufacturers have been tasked with designing printed circuit board assemblies (PCBAs) that are increasingly small in size, but complex in power and function. The pressure to achieve both of these requirements is pushing the physical limits of PCB manufacturability. Catastrophic recalls like Samsung’s exploding Galaxy Note 7 illustrate how the race towards thinner, higher performing products compromises planning and testing, puts end user satisfaction and safety at risk, and ultimately costs manufacturers time and money.
By designing PCBs with manufacturability in mind, engineers can proactively lessen the risks of product failure or poor product performance. Design for manufacturability (DFM) accounts for every step of the production process – from initial drawing and prototyping to fabrication, assembly, testing, and phases of post-production including procurement, shipping, delivery, and beyond. Taking the principles of DFM into account, engineers review the processes involved in each of these steps, while also considering the associated costs.
Unfortunately, there’s no shortage of challenges that could arise throughout the phases of production. Early stage design defects can affect overall system processes and product yield, while manufacturing errors can lead to missing or misplaced components, insufficient solder, bent pins, and electrical deficiencies. By making DFM considerations early in the process of product design, engineers mitigate the risks of small defects that, if overlooked, can trigger harmful downstream effects.
The key to DFM is process. OEMs (original equipment manufacturers) that invest in specialized design tools and optimize and streamline their operational processes to correct inefficiencies ultimately yield optimum product quality and higher ROI. High quality back-end DFM tools support engineers in identifying ruleset violations, however they can also create bottlenecks in production if errors are caught too late in the design cycle. Interactive DFM tools are a more effective alternative, providing engineers with real-time reporting on design flaws and enabling them to make immediate adjustments with minimal disruption to the production process.
Even with the implementation of these tools, however, there are other common pitfalls to be aware of:
- Lack of communication with PCB/PCBA manufacturers – Maintain close contact with your manufacturer, even when outsourcing a design. Early and regular communication – even before handing the design off – is the best way to stay ahead of possible setbacks or complications.
- Rule set mismatch – In addition to communicating with your manufacturer, communicate with your supplier about component footprint files. A designer may have thousands of parts worth of files, so you’ll want to ensure you’re providing the manufacturer with the exact specs you want when setting up DFM rule sets.
- Electrical performance issues – The electrical characteristics of the board are almost always affected by physical design changes. Be sure to use simulation tools to run tests on how electrical performance would change before committing to any major design modifications.
- Designs that aren’t compatible with every manufacturer – If you’ve used a rapid prototyping service to expedite the design process, be aware of whether the prototyped part is specific to the manufacturer that made it. Contact other manufacturers to see if they have the capabilities to replicate it, or if they would need to alter the design to meet their DFM requirements. If you have a specific manufacturer in mind, speak with them about these requirements ahead of time to design a part suited for their capabilities.
- Variations in tolerance – Check tolerances for consistency at every level for individual parts as well as overall manufacturing processes.
Above all else, DFM is a risk management strategy for PCB assembly. When executed properly, it reduces costs and creates a more seamless production process. Every aspect of PCB assembly, from material selection and board layout to layer stack-up and trace width, can be optimized through the implementation of rules, requirements, and limitations. DFM tools operate under these rule sets to support improvements in product yield and enhance the performance of the end user product. To meet the simultaneous demands of miniaturized components and expanded capabilities, original equipment manufacturers should consult contract manufacturers with experience in DFM as partners throughout the design process.
