Assembly and Quality Control

In-House Testing Methods: AOI, X-Ray, and Functional Checks

In-house testing methods like AOI, X-Ray, and functional checks ensure PCBA assemblies meet stringent quality standards before shipment. These techniques catch defects early, minimizing rework and field failures for OEMs and engineers.

Automated Optical Inspection (AOI)

AOI uses high-resolution cameras and multiple LED light sources to scan assembled boards post-SMT or reflow soldering. It detects visible defects such as missing components, misalignments, insufficient solder, bridges, or polarity errors by comparing against golden samples or CAD data.

Key benefits include:

  • Non-contact, high-speed inspection (up to 50 cm²/sec).

  • Operator-independent results with >99% accuracy for Class 2/3 boards.

  • Ideal for high-volume runs, catching 80-90% of soldering issues.

X-Ray Inspection (AXI)

X-Ray, or Automated X-Ray Inspection, employs real-time fluoroscopy or 3D CT imaging to penetrate boards, revealing hidden defects invisible to optical methods. It inspects BGA/QFN solder joints, via fills, internal layer alignment, and voids in multi-layer stacks.

Key benefits include:

  • Detects subsurface issues like head-in-pillow or microcracks.

  • Essential for high-reliability apps (automotive, medical) per IPC-A-610.

  • 2D/3D modes support complex BGAs up to 1mm pitch.

Functional Testing

Functional checks power up the fully assembled PCBA to verify real-world performance against design specs, including voltage levels, signal integrity, timing, and firmware behavior. Jigs with bed-of-nails probes or flying probes apply inputs and measure outputs via boundary scan (JTAG) or custom scripts.

Key benefits include:

  • Validates end-to-end operation, uncovering intermittent faults.

  • Supports ICT integration for opens/shorts plus dynamic tests.

  • Critical final gate, ensuring 100% compliance before delivery.

Comparison of Testing Methods

MethodBest ForSpeedCostDetects Hidden Defects
AOISurface/solder jointsVery FastLowNo
X-Ray (AXI)BGA/vias/internal layersModerateMediumYes
FunctionalFull circuit performanceSlowVariablePartial (powered)

Implementing In-House Quality

Combine AOI post-placement/reflow, X-Ray for high-density packages, and functional tests as the final QC step to achieve <500 DPMO. Foshan Krivina PCBA integrates these in our China facility with ISO 9001 certification, delivering reliable imports to India.

Ensure Your Quality: Upload Gerbers for complimentary testing quotes and DFM feedback today.

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