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86 PCB007 MAGAZINE I JULY 2022 Manufacturing yield is a key measure of qual- ity in PCB manufacturing. Measured as a per- centage of good parts relative to the total pro- duced, achieving 100% yield rates is extremely challenging for anything but the simplest PCB designs. Most PCB manufacturers produce less than a 95% yield, eating the cost of discards and re-designs. PCB manufacturers can take steps to improve yield rates. It is possible to achieve more than a 98% yield rate by addressing com- mon manufacturing errors, improving safety and quality in tandem, and integrating a Lean approach to all processes. Addressing Common Errors Many errors go unnoticed in fabrication and even assembly. Looking out for these during prototyping can catch low yield culprits before production. While testing increases cost and turnaround during prototype iteration, gains in yield rate will offset this in high-volume pro- duction. Keeping these guidelines in mind can accel- erate the process: • Always double-check that your bill of materials components fits your layout foot- print. Replacing a component that doesn't fit its location or size on a board can be costly, if not impossible. Mismatched boards are oen unusable. • Ensure that board materials can withstand the electrical and mechanical demands of your design. Inadequate material can cause failure from thermal or physical stress. • Don't try to cut corners when it comes to spacing and clearance. Many PCB lay- out errors are the result of clearance viola- Caution—Yield Ahead Connect the Dots by Matt Stevenson, SUNSTONE CIRCUITS