Introduction to In-Circuit Testing (ICT): Fault Coverage

In-circuit testing (ICT) is a critical process in electronics manufacturing, designed to ensure that printed circuit boards (PCBs) function as intended. As electronic devices become more complex and densely packed with components, ensuring the reliability of each PCB before it reaches the end user is paramount. ICT helps to detect defects at an early stage, ensuring that only fully functional products move further down the production line

Understanding Fault Coverage in ICT

Fault coverage is one of the most important metrics when evaluating the effectiveness of an ICT system. Fault coverage is a term that refers to a test program's ability to detect potential faults.

Why Fault Coverage Matters

Achieving high fault coverage is critical because it ensures that a larger percentage of defects are caught early in the manufacturing process, minimizing the chances of defective products reaching customers. Some of the benefits of maximizing fault coverage include:

• Reduced rework and scrap costs: By detecting faults earlier, manufacturers can repair defective PCBs before they are fully assembled or shipped.
• Improved product reliability: Products that undergo rigorous testing with high fault coverage are more likely to function correctly in the field, leading to fewer returns and warranty claims.
• Increased customer satisfaction: High-quality, thoroughly tested products enhance brand reputation and customer loyalty.

Manufacturers choose Acculogic for fault testing because of its advanced and comprehensive testing solutions that help ensure high-quality electronics production. Acculogic's TPS team supports all the major ICT platforms in the market, such as Keysight 3070 and Teradyne TestStation, offering a variety of test techniques to handle different types of components used on the printed circuit boards.

The TPS team performs detailed analysis to ensure that the test programs provide optimal fault coverage, identifying and addressing potential areas of concern on the PCB and can generate analysis reports. The Test Engineer uses these reports to identify tests that may need more debugging or identify components that are missing tests. The Manufacturer or Customer receiving the test program can use the Report to determine the fault coverage provided by the in-circuit test program. The General Summary Report shows the following digital fault insertion information:

• A list of all ICs tested by the Analyze tool command and the resulting fault coverage percentage.
• Number of digital devices tested in the program.
• Number of UUT input pins tested and the percentage of stuck-at-0 and stuck-at-1 faults that can be detected on them.
• Number of UUT output pins tested and the percentage sensed high and low.
• Number of UUT bidirectional pins and the percentage of them that detect stuck pins when used as inputs, and the percentage of them that were sensed high and low when used as outputs.
• Number of VCC, GND, and UNUSED pins.
• A list of burst labels that the Analyze tool command skipped because of burst failures.

The report identifies components that may require additional testing after in-circuit test. The TPS team can work with the PCB manufacturer or customer to create a functional test or a system self-test for areas of the board that are not fully tested during in-circuit testing.

Acculogic’s TPS Team provides manufacturers with critical support in developing and optimizing test programs tailored to their specific PCB designs and production needs. With their expertise in custom programming, fixture design, debugging, and optimization, the team ensures that manufacturers achieve the highest possible fault coverage and testing efficiency.