ICT vs Flying Probe: Best Method for High-Volume Manufacturing
No matter how good manufacturing processes and machines are, some defects are to be expected due to human error, wrong component values, dead devices (for example: ESD-damaged), assembly process or placement errors, or electrical hazard defects during mass production. Hence, it is evident that testing is necessary to capture defects and ensure product quality. The most common electrical test methods are in-circuit testing and flying probe testing. In this post, we will examine these two options and assess how they align with the overall electrical testing needs of manufacturers.
In-Circuit Test (ICT)
In-circuit test (ICT) is a powerful tool for high-volume printed circuit board assembly testing. ICT is highly efficient, performing node-oriented open shorts testing and component value testing for virtually all electrical components with remarkable speed, thanks to its simultaneous access to 'bed-of-nails' fixtures. This makes ICT the fastest and most reliable method for defect detection in high-volume manufacturing. It can also perform unpowered vectorless tests, digital vector tests, JTAG boundary scans, and mixed tests relatively quickly compared to other electrical testers, as all the connections are in place in the fixture.
Test program generation is automated, and sophisticated circuit analysis is employed to create optimal test cases. Defect detection is the fastest when compared with the flying probe. Diagnostic routines are relatively short; as a result, testing costs are lower than those of other electrical systems that might need skilled support engineers. This makes ICT attractive for production use.
Node access is becoming more challenging due to board compactness as component geometry continues to shrink. The move to higher-speed operation further drives intra-device spacing to smaller distances, thereby increasing the signal routing problems for test pad access. However, it is still possible to achieve good coverage, as the core test challenges have been resolved with limited nodal access test methodologies. Test coverage can be further improved by adding external circuitry or hardware such as counter modules for measuring very high frequencies (>100 MHz) and photo-detectors to test LED color and intensity.
Flying Probe Testing
A flying probe utilizes a generic board holder with multiple probes that access individual nodes of the board through software control. The software can be developed relatively quickly from the PCB design files, allowing for easy changes as pad positions or components are modified. No mechanical test fixture is required, and fixture fabrication time is not needed.
While flying probe testers offer flexibility and cost-effectiveness, their slower operating speed and lower levels of electrical fault detection make them less suitable for high-volume production compared to ICT. For an ICT system, all the connections are in place in the fixture. A flying probe is not always able to achieve higher levels of electrical fault detection. It is suitable for low-volume production and prototype applications due to its speed limitation and flexibility, low development costs, and short development time.
In conclusion, ICT remains the dominant choice for high-volume manufacturing due to its efficiency, speed, and cost-effectiveness. While flying probes have their place, ICT offers the best combination of reliability and performance, making it the ideal choice for manufacturers looking to ensure product quality and minimize defects.