C-SAM

Scanning Mode

The hardware moves the transducer over the surface of the specimen in a rapid pattern while simultaneously firing acoustic pulses into the material. Because the system records the echo amplitude at a specific depth range, it produces an image representing a thin slice of the physical assembly. This method relies on a gate to filter out reflections from the upper and lower surfaces of the package so that the focus remains on the specific interface under test.

Data acquisition occurs at discrete intervals to assemble a pixel-based representation of the scanned volume. Digital signal processing analyzes the intensity of each return pulse to assign color or contrast values that indicate the status of the interface.

Acoustic Impedance

Variations in the material properties at a bond interface dictate the intensity of the reflected acoustic pulse. When a sound wave travels from a high impedance solid into a low impedance gas within a void, nearly total reflection occurs. This interaction results in a high contrast pixel in the final scan because of the difference in mass density and sound velocity between the materials.