What is the difference between acoustic imaging, acoustic micro imaging, and scanning acoustic microscopy?

None. They are synonyms for the same non-destructive inspection technique. The acronyms AMI, SAM and C-SAM® are also frequently used and stand for Acoustic Micro Imaging, Scanning Acoustic Microscopy and C-mode Scanning Acoustic Microscopy, respectively. The term "ultrasonic testing" is sometimes used to describe this technique as well, but can also be used in reference to macro systems designed for inspecting larger items, such as structural components of vehicles or aircraft, using lower frequencies. The term "Sonoscan testing" is often used as another synonym for acoustic micro imaging. Sonoscan® and C-SAM® are registered trademarks of Sonoscan Inc., the inventor of this inspection technology and a primary provider of acoustic microscopy systems.


Is red or yellow always bad in an acoustic image?

No. A variety of colormaps can be applied to highlight defects in an image. It is important to evaluate the actual echo waveforms to determine the nature of a particular feature.  Click here for an example showing the difference that proper and improper colormap choices can make in an acoustic image.

What defects can be found using acoustic microscopy?

Acoustic Microscopy is particularly sensitive to delamination, cracks, and voids. Any defects that entail a separation, no matter how slight it might be, cause the sound to bounce back to the transducer instead of transmit through the device.  For a diagram that shows examples of these defects click here. Or for some specific examples/case studies click here.

What package types or devices can X-ray and C-SAM® be used on?

There are a myriad of devices that x-ray and C-SAM® can be applied to.  To see some specific case studies click here.

Specifically for C-SAM® the short answer is basically any device that is not constructed to have air gaps or is not round. A typical device would be a plastic encapsulated microcircuits (PEM's) where MSL testing could cause internal damage, or prior to doing a DPA, or to screen a particular lot for defects.  Other devices that are commonly scanned acoustically are ceramic capacitors, heatsink attachments, hybrids, or devices on PCB's.

As far as X-ray, PEM's are also fairly common. In addition to PEM's, devices that do contain gaps or are round in nature such as ceramic IC's and CAN or AXIAL devices are good x-ray candidates.  X-Ray is also ideal for finding broken or bent bondwires as well as potential counterfeit devices.
For more basic information on PEM's click here