In-Circuit Test Vector Synthesis for High Density Assembly Modifications
Vector synthesis for modified assemblies requires delta netlist verification, BSDL timing re-validation, and algorithmic backdrive current bounds.
Test Coverage Degradation
Meaning
Manufacturing quality metrics define the decrease in the proportion of circuit nodes or functional blocks that can be assessed during production testing. Ongoing test coverage degradation occurs when product updates add features without corresponding test points on the board. This reduces the ability of the test fixture to detect assembly errors, which leads to defective units reaching customers.
Production managers track this metric to determine when a test program update is necessary.
Interface Accumulation
High-density board designs limit the space available for dedicated test pads, which forces test engineers to rely on fewer physical test points. When nodes are omitted from the test access list, the test coverage drop is proportional to the unmonitored circuits. Utilizing boundary scan techniques allows engineers to test internal digital connections without physical probe access.
This logical testing compensates for the loss of mechanical access on highly integrated boards.
Diagnostic Capability
Untested circuit blocks increase the time needed to locate root causes of field failures. Faults remain hidden until the end-user operates specific functions.
Risk Mitigation
Designing for testability ensures that all critical power rails and radio frequency paths remain accessible to the testing probes. Factory yield analysis verifies that the escape rate of defective boards does not exceed the target threshold.