C-SAM (C-mode Scanning Acoustic Microscopy) is the most commonly used acoustic imaging mode for electronic package inspection — producing a plan-view (top-down) image at a specific depth within the package by gating the reflected signal from a particular interface.

What Is C-SAM?

• C-Mode: The transducer scans the $(x, y)$ plane. The return signal is gated to a specific time window corresponding to a specific depth (interface).
• Image Interpretation:
• Dark areas: Good bonding (acoustic energy transmitted through).
• Bright/White areas: Delamination or void (acoustic energy reflected back strongly due to air gap).
• Gate Selection: Different gates image different interfaces (die-to-DAF, DAF-to-substrate, etc.).

Why It Matters

• Industry Standard: "C-SAM" is often used interchangeably with "Acoustic Microscopy" in semiconductor packaging.
• Production Screening: Used for 100% inspection of critical packages (automotive, medical).
• Failure Correlation: C-SAM images directly correlate to cross-section findings.

C-SAM is the delamination detector — the single most important non-destructive tool in semiconductor package quality assurance.