Isolation Precision
The degree of specificity with which a circuit board test system isolates a failure to a single component or a specific net determines the efficiency of the rework process. This metric, known as diagnostic resolution, determines whether a test operator can immediately target the failed part or must troubleshoot a list of suspects. High resolution decreases repair times and lowers rework-induced defects.
It is a function of both test program design and board layout access. For complex digital assemblies, this metric is often expressed as the percentage of faults that can be isolated to a single replaceable component.
Test Coverage
In-circuit testers achieve high pinpoint accuracy by using dedicated test points for each node. If a board lacks physical test points, the diagnostic software might only isolate the error to a group of parallel components. This limitation forces the repair technician to perform manual measurements to find the root cause.
Proper board design includes a strategy for high-resolution testing.
Repair Effectiveness
Low precision results in the unnecessary replacement of functional parts. Operators may replace three components when only one was defective, which wastes materials and risks board damage from excessive heat. High-resolution diagnostics use algorithmic routines to narrow down the fault to a single pin.
This optimization maintains high yield rates and protects delicate traces.
