What is Drill Tool Inspection
Drill tool inspection examines and evaluates the quality and precision of the drilling phase in PCB manufacturing. This inspection is essential to ensure that the drilled holes meet the required specifications and adhere to the highest standards of quality.
During the drill tool inspection, the drill count and size, which are compared against the specifications provided in the fabrication (fab) print, are carefully assessed. The inspection also verifies the type of drill, distinguishing between Plated Through Hole (PTH) and Non-Plated Through Hole (NPTH) drills. Additionally, the presence of connections for non-plated drills is checked to ensure accurate drilling without any unintended connections between different holes.
Other aspects examined during the inspection process include the identification of close holes with a diameter less than 0.006 inches, the detection of mouse bites (small perforations facilitating board separation), and the verification of drills and features within the defined board profile. The inspection also evaluates the via sizes and their compliance with the minimum aspect ratio requirement, which refers to the ratio of the depth of the drilled hole to its diameter.
Furthermore, the inspection assesses the tolerance levels for both plated and non-plated drills, aiming for precision within the specified tolerances. Consistency between the fab drawing and the drill file is also verified, ensuring that all NPTH drill/slot or cutout locations are accurately represented. Finally, the inspection confirms compliance with via filling requirements, as specified in the assembly guidelines.
Drill Tool Inspection can be performed manually, although it may be limited by the decreasing inspection capability of the human eye for small-size apertures. Alternatively, specialized equipment such as PCB hole inspection machines or Automated Optical Inspection (AOI) equipment can be employed to enhance efficiency and accuracy. These machines utilize optical systems to capture images of the drilled holes and compare them with the design file, enabling the detection of any discrepancies or defects.