What Is a Scanning Acoustic Microscope (SAM)?
Scanning acoustic microscopes (SAM) are devices used to inspect internal defects in materials. They utilize ultrasonic waves for non-destructive inspection. This technique, known as ultrasonic flaw detection, enables the visualization of internal structures of materials such as semiconductor components and car bodies.
Ultrasonic flaw detection measures the condition of an object based on the reflection of ultrasonic waves transmitted from a sensor, allowing for detailed internal examination.
Uses of Scanning Acoustic Microscopes (SAM)
Scanning acoustic microscopes are primarily used to detect minute defects inside objects without causing damage.
1. Semiconductors
In semiconductor manufacturing, SAM identifies delamination and cracks in molded IC packages. It can also detect delamination between chips in stacked IC packages and evaluate underfill delamination and voids in CSP.
2. Electronic Components and Ceramics
These devices can detect cracks, delamination, and voids in the internal electrode components of chip components. They also provide defect depth information through color coding.
3. Resin and Composite Materials
SAM is useful for analyzing resin flow in injection molding, detecting microspores and resin density distribution patterns. In carbon fiber reinforced plastic (CFRP) fracture analysis, it observes delamination in each layer during steel ball drop tests.
4. Metal Materials and Plate Bonding Conditions
This technology inspects bonding conditions between target materials and packing plates in sputtering targets for semiconductors, FPDs, solar cells, and more. It is capable of handling larger target materials.
5. Power Module Inspection
SAM is used for in-line inspection of component joints in power modules like IGBTs, detecting delamination and voids.
6. Laminated Wafer Inspection for MEMS
It visualizes bonding surfaces in laminated wafers for MEMS, detecting unjoined areas as small as 10μm in diameter.
Principle of Scanning Acoustic Microscopes (SAM)
Scanning acoustic microscopes use a probe combining an ultrasonic transmitter and receiver. The probe scans over a sample, creating images from the reflected waves. Ultrasonic waves reflect at material boundaries, allowing for detailed internal imaging. For ultrasonic wave measurement, the material is typically placed in water.
Principle of Ultrasonic Measurement
The probe’s piezoelectric element vibrates when stimulated by pulse voltage. These vibrations generate ultrasonic waves in water, which propagate as elastic waves inside the sample. Variations in acoustic impedance due to voids, cracks, or foreign matter cause reflection and refraction. The probe emits intermittent pulses and detects defects by receiving reflected sounds from within the specimen between oscillations.