scanning acoustic microscopy (sam)

**Scanning Acoustic Microscopy (SAM)** is the **specific instrumental implementation of acoustic microscopy** — using a focused ultrasonic transducer that rasters across the sample surface to build a high-resolution acoustic image of internal structures. **What Is SAM?** - **Transducer**: Piezoelectric element focused through a sapphire or fused-silica lens. - **Resolution**: Down to ~1 $mu m$ at 1 GHz (surface mode), typically 15-50 $mu m$ at production frequencies. - **Image**: Each pixel represents the reflected amplitude and time-of-flight at that $(x, y)$ position. - **Vendors**: Sonoscan (Gen7), PVA TePla, Hitachi. **Why It Matters** - **MSL Qualification**: Mandatory per IPC/JEDEC J-STD-020 for Moisture Sensitivity Level classification. - **Flip-Chip Inspection**: Checking underfill coverage and bump integrity. - **QA Audit**: Widely used for incoming quality and return-material analysis (RMA). **SAM** is **the X-ray of packaging** — the industry-standard non-destructive tool for verifying the internal integrity of semiconductor packages.