Optimizing Flying Probe Probe Target Allocation on Partially Accessible Interposers
Combining flying probe vectors with boundary scan coverage maximizes test fault detection while protecting micro-land integrity on dense interposers.
Z-Axis Probe Positioning
Contact Control
The precise control of the vertical height of a test probe relative to the circuit board surface prevents mechanical damage to delicate test points and component pads. During automated flying probe testing, accurate z-axis probe positioning ensures that the probe tip makes reliable electrical contact without puncturing the copper cladding. This contact control is essential for testing high-density board assemblies with small test pad dimensions.
Test Precision
The mechanical assembly uses closed-loop stepper motors and high-resolution optical encoders to control the vertical movement of the test head. In flying probe test systems, the z-axis probe positioning must compensate for any board warpage or flexure to maintain a consistent contact force. If the probe descends too far, it can leave deep craters in the solder pad or fracture the underlying dielectric layer.
This precision is maintained by using laser height sensors to map the surface profile of the board prior to running the test sequence.
Mechanical Safety
Automated calibration cycles are executed at regular intervals to reset the zero height reference point of the system. This calibration corrects for thermal expansion of the test machine frame or wear on the probe tips. This maintenance task ensures that the test sequence runs without damaging the boards.