8.4 Bare Board Inspection (IPC-A-600)

The quality of the final assembly cannot exceed the quality of the raw Printed Circuit Board (PCB). IPC-A-600 is the acceptance standard for rigid and flexible bare boards. This chapter defines the criteria for Incoming Quality Control (IQC).

8.4.1 Base Material (Laminate) Conditions

• Measling: Discrete white spots where resin has separated from fibers.
  • Class 2/3 Acceptable: If it does not bridge conductors or reduce spacing below minimum electrical clearance.
• Delamination/Blistering: Separation of layers.
  • Class 2/3 Defect: Any delamination exceeding 25% of the distance between holes or internal conductors is a rejection.

8.4.2 Plating & Solder Mask

• Solder Mask Skip: Absence of mask between pads.
  • Defect: If it exposes adjacent conductors, creating a risk of solder bridging.
• Hole Breakout: The drill hole is not perfectly centered on the pad.
  • Class 2: 90° breakout allowed (hole exits the pad) provided minimum annular ring is maintained on the wire-side.
  • Class 3: Hole must be contained within the pad (Tangency allowed, no breakout).

Final Checklist