From DFM to DFT: Best Design Practices to Improve PCBA Yield | PCBA News & PCB Assembly Updates

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01

2025

From DFM to DFT: Best Design Practices to Improve PCBA Yield

What is DFM (Design for Manufacturability)?

Design for Manufacturability (DFM) focuses on optimizing a PCB design so it can be manufactured efficiently and at a lower cost without compromising quality. It ensures that the design aligns with your manufacturing partner’s capabilities, equipment, and assembly processes.

Key DFM Best Practices:

Standardize Component Footprints

Avoid exotic or outdated components. Use standard sizes and footprints that your supplier can source easily.
Keep Trace Widths and Spacing Manufacturable

Ensure that your trace widths and spacing comply with the manufacturing house’s minimum design rules to avoid short circuits or open circuits.
Avoid Complex Layer Stacks When Possible

Overly complex multilayer PCBs can increase manufacturing time and cost. Use only as many layers as needed for performance.
Proper Pad-to-Hole Alignment

Misaligned pads can cause soldering defects. Ensure vias and pads are accurately positioned and follow IPC standards.
Minimize Use of Vias-in-Pads

Vias in BGA or QFN pads can cause solder wicking and voids. Use via tenting or epoxy filling techniques if unavoidable.

What is DFT (Design for Testability)?

Design for Testability (DFT) ensures that a PCBA can be easily inspected and tested for defects during manufacturing. This step is crucial for maintaining yield as it allows early detection of issues before the product reaches end users.

Key DFT Best Practices:

Include Test Points for Key Signals

Provide adequate test access to power rails, ground, and high-speed signals for ICT (In-Circuit Testing) or flying probe testers.
Design for Boundary Scan (JTAG)

For complex assemblies or high-density BGAs, incorporate boundary scan test capabilities to facilitate fault isolation.
Space Out Test Pads

Ensure test pads are accessible and not too close to each other. This helps with reliable fixture contact and reduces false test failures.
Provide Clear Test Documentation

Collaborate with your EMS partner by providing schematics, netlists, and test specifications during the design handoff.

Why DFM and DFT Matter for PCBA Yield

Poor PCBA yield can lead to increased costs, long lead times, and unhappy customers. By integrating DFM and DFT best practices into your product development lifecycle:

You reduce defects during SMT and THT assembly
You catch errors early through test-friendly layouts
You save time and money during debugging and rework
You increase customer satisfaction and trust

Bonus Tips: Collaborating with Your EMS Partner

Your EMS partner plays a critical role in turning your designs into reliable products. Here's how you can ensure better collaboration:

Share Gerber files, BOM, pick-and-place files, and DFT documentation early.
Ask for a DFM/DFT review during the prototype phase.
Be open to feedback—manufacturers often suggest improvements based on real-world production experience.

Final Thoughts

DFM and DFT are not just checkboxes in your design checklist—they are strategies that, when implemented together, lead to higher PCBA yield, faster time-to-market, and fewer production surprises. By aligning your design with manufacturability and testability principles, you not only improve your bottom line but also build a more scalable and robust electronics product.

Looking for a Manufacturing Partner Who Cares About DFM and DFT?

We specialize in working with startups and small to medium-sized businesses. Whether you're building your first prototype or scaling to production, we offer design feedback, functional testing, and flexible collaboration to bring your ideas to life—without compromising quality.

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