Measuring Vibrations of Encapsulated MEMS

This application note demonstrates how SmarAct’s PICOSCALE Vibrometer enables direct, non-invasive measurement of MEMS vibrations through silicon packaging. Using infrared (1550 nm) confocal imaging, the system visualizes and quantifies internal motion in packaged MEMS devices like the MPU-6050 motion sensor. This allows accurate modal analysis under near-operational conditions—critical for design validation and integration testing.

Problem

MEMS sensors, such as motion detectors, often come sealed in silicon enclosures that block visible light—preventing traditional interferometric analysis of internal vibrations. However, evaluating mechanical performance through the package is crucial for development, integration, and troubleshooting of embedded systems.

Solution

The PICOSCALE Vibrometer uses 1550 nm infrared light and confocal microscopy to penetrate silicon enclosures and selectively image the internal MEMS structures. This enables modal and phase-resolved analysis of moving parts without altering or disassembling the sensor.

Implementation

• The system scanned through the silicon, identifying reflection peaks from both the window and MEMS structure.

• Local vibrations were measured under mechanical excitation (1–600 kHz), and resonance modes were visualized in 3D.

• Phase mapping showed motion differences between internal MEMS components.

Results

• MEMS features below the silicon surface were clearly imaged and resolved.

• Multiple resonance peaks were identified and assigned to specific bending modes.

• Different MEMS elements showed phase-shifted behavior (~70°), indicating decoupled dynamics—valuable for design validation.

Conclusion

The PICOSCALE Vibrometer enables precise, through-silicon vibration measurement of encapsulated MEMS. This opens up new possibilities for non-destructive testing, performance analysis, and system integration optimization of motion sensors and other packaged microstructures.