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.
False Fails
Erroneous Rejection
Manufacturing test discrepancies occur when functional boards are incorrectly classified as defective during automated optical inspection or functional testing. The occurrence of false fails stems from overly sensitive test limits on the inspection line. These incorrect readings force unnecessary secondary manual reviews or diagnostic procedures.
Trigger Mechanism
In automated optical inspection, camera alignment drift, board warp, or shadow effects from tall components frequently generate incorrect defect reports. This phenomenon is known as false fails and occurs when the automated algorithm compares a non-standard but acceptable board feature to a rigid golden board template. Variations in solder joint reflectivity also cause the machine to flag a non-existent anomaly.
Adjustments to the lighting profile or algorithmic tolerance limits can mitigate this issue, which maintains a high first pass yield without compromising actual defect detection.
Operational Burden
Unnecessary re-routing of acceptable boards to manual rework stations slows the manufacturing line and introduces opportunities for handling damage. When automated equipment reports false fails, human operators must spend time performing visual confirmation under a microscope. This repetitive manual inspection degrades throughput and introduces subjective operator fatigue.
It increases assembly costs because resources are consumed re-evaluating assemblies that already meet IPC acceptance criteria.