How to Perform a Design for Manufacturing Review

A design for manufacturing review will help you spot all the errors in your design and take steps to correct these before volume production.

12 August 2021

Anytime a new product is to be placed into manufacturing, it must pass a design for manufacturing (DFM) review. During the DFM process, the design is thoroughly inspected for any aspects that may create manufacturing defects or assembly defects. An alignment between your manufacturer’s process capabilities and the design is critical to ensure high yield and eliminate the need for any rework.

In PCB and electronics packaging manufacturing, this review phase is quite critical. There are many electrically correct design choices that can be implemented in a PCB, but these are not always manufacturable, and they may not comply with certain industry standards that govern your design. Working with an experienced partner that understands how to streamline a DFM review will help ensure success, quality, and yield. An experienced manufacturing partner can also help you identify areas where costs can be reduced without sacrificing quality or yield, helping you stay competitive in a global market.

What to Expect in a DFM Review

There are several goals to be achieved in a DFM review:

  1. Compare feature sizes with processing limits. Any feature sizes that are below reliable processing capability limits may need to be modified. In some cases, small features or clearances are unintended defects from ECAD software and identifying these early lets a design team modify them before production.

  2. Inspect the stackup for producibility. Design teams can often get bogged down focusing on complex design tasks, but they may forget simple things like dielectric selection and layer thickness in the PCB stackup. The best EMS companies can help modify the stackup as needed to ensure impedance, signal loss, and layer thickness targets are met.

  3. Ensure acceptance standards are satisfied. Industry standards, such as IPC-A-600/610 and IPC-6011/6012, define certain acceptance and performance criteria that should be reflected in the design. A DFM review allows the manufacturer to check that these were implemented in the physical design.

  4. Identify potential assembly defects. Problems like tombstoning, solder bridging, cold joints, wicking, and residue can be identified by inspecting PCB footprints, solder mask openings, and other features in the physical design. Another benefit is the ability to plan out the assembly process for a complex product.

A DFM review can be performed by manually looking through the design and by using the DRC functions in ECAD software. Typically, the design is examined after DRCs are run and corrected to spot any problems that might create manufacturing or assembly defects. The design team can then correct these final problems before generating output files.

Once your design and fabrication files are sent to an EMS provider, they are typically inspected using specialized CAM software. For PCB manufacturing, the Gerbers are scanned to identify any clearance and feature size violations, as well as common via size, drill hit location, and SMD/NSMD pad violations. Manufacturers are very experienced at using these programs and can deliver a report to the design team with any violations, as well as proposed solutions where needed.

Streamline Your Design for Manufacturing Review

Working with the right manufacturer and some front-end requirements gathering can help both sides streamline the DFM review process and get into production quickly. However, there are some simple steps OEMs can take to help streamline the design review process, especially when planning for high volume production.

  • Know your relevant standards. The list of electronics performance and reliability standards is long, and not all of these will apply to your board. Make sure to communicate the relevant design, performance, and inspection standards to your fabricator when preparing for production.

  • Contact your manufacturer early. Taking a moment to inquire about processing capabilities, preferred stackup requirements, and available materials before starting a design will help ensure the design passes a DFM review. This prevents production delays by eliminating redesigns.

  • Run spot DFM checks during design. DRCs in ECAD software are very helpful for spotting manufacturability constraint violations. It’s advisable to run spot checks at various points in the design process, such as after component placement, routing, and final layout cleanup.

  • Create thorough documentation. ECAD software can quickly generate fabrication and assembly files from your design data. These files should be generated and sent in for DFM review along with the original ECAD files. Some design changes may be simple enough to be applied without sending the design back to the customer.

One other important aspect of a DFM review is to review testing requirements and testability. The design team should clearly communicate these test requirements to an EMS provider, as well as which test requirements are most critical for high-volume manufacturing vs. prototyping. During a DFM review, your EMS provider will also be able to spot some design changes that will aid testability.

Beyond Level 1 Automation

Today’s newer trucks include ADAS capabilities that have converged with telematics systems. Data collected by telematics modules is already used in conjunction with ADAS systems to activate safety mechanisms in Level 1 autonomous vehicles. However, as automation in autonomous trucks increases and the driver can take a less active role in controlling the vehicle, the dependency on telematics will continue to increase.

Perhaps the most important thing a design team can do to ensure high yield is to gather their manufacturer’s DFM requirements early. If manufacturing capabilities and feature limits are gathered early in the design process, these can be added as design rules to ECAD tools to help ensure there are no accidental DFM violations in the final fabrication files. This allows designers to perform spot DFM checks throughout the design process, rather than waiting to perform a single DFM check once the design is completed. Your EMS partner can provide capabilities statements and fabrication tolerances upon request so that you can implement these constraints in your design software.

OEMs that want to ensure high quality and yield should partner with an experienced EMS service that performs a comprehensive design for manufacturing review. We have more than 30 years of EMS experience focused in consumer goods, industrial, automotive, and medical devices, as well as in Printed Circuit Board Assembly (PCBA) and box builds. Our Lean Six Sigma manufacturing expertise enables us to customize our manufacturing line to meet our partners’ requirements.

If needed, we provide our customers the flexibility needed to quickly scale production as needs arise. We provide our partners with high-quality products at lower manufacturing costs thanks to our shorter change-over time and leaner material control. Contact PCI today to learn more about our capabilities.