In Circuit Test Nodal Access Limits on High Density Microvia Boards
Physical test probe access drops on high-density microvia boards, demanding solder beads or boundary scan to maintain coverage without damaging copper caps.
Trace Probing
Physical Measurement
Direct contact of a test instrument pin to a copper line on a circuit board allows the system to measure voltage or trace resistance during diagnostic testing. Performing trace probing requires high positioning accuracy to avoid damaging the fine conductor paths or the protective solder mask. The process is used in both flying probe and bed-of-nails test fixtures to verify electrical nets.
Probe Damage
Contact pressure and probe tip shape must be carefully managed because excessive force can gouge the copper or crack the underlying laminate. For high-speed lines, trace probing might introduce small capacitance changes that distort the signal, so engineers must plan where to place test points to minimize signal degradation. If trace widths are extremely narrow, manual probe placement becomes impossible, necessitating automated flying probe systems equipped with precision cameras and software-driven positioning.
These systems can locate and test paths with micrometer-level precision.
Yield Verification
Analyzing the test data helps engineers identify open circuits or shorts that occurred during board fabrication or assembly. When trace probing is integrated into the production workflow, it acts as a reliable filter to prevent defective boards from moving to final assembly. This step protects the quality of the shipped product.