Scanning Acoustic Microscopy & Electronic Failure Analysis

Acoustic imaging is both science and experience. IAL can provide you with both to ensure a proper reading of the images.

Scanning Acoustic Microscopy (CSAM) is a quick, non-destructive failure analysis technique that uses ultrasound waves to detect changes in acoustic impedances in integrated circuits (ICs) and other similar materials. Pulses of different frequencies are used to penetrate various materials to examine sample interiors for voids, cracks or delamination.

Scanning Acoustic Microscopy is used for evaluation of die attach integrity, heat spreader adhesion, and solder quality.

 

 

Purpose:

Scanning Acoustic Microscopy provides non-destructive investigation and failure analysis of opaque devices. This includes, but is not limited to, plastic or ceramic integrated circuits, chip capacitors, chip resistors, circuit

board traces, and discrete

semiconductor devices.

 

Scanning Acoustic Microscopy is complimentary to X-ray analysis.

C-scan of packaged integrated circuit showing die surface delamination

Application:

  • Electronic plastic package evaluation

  • Electronic ceramic package evaluation

  • Chip capacitor and resistor evaluation

  • Die attach evaluation

  • Molding compound evaluation

  • Package crack detection

  • Flip chip bond evaluation

  • Printed circuit metal trace evaluation

Technical Notes:

Longitudinal waves: wave movement is parallel to particle movement.

Acoustic Velocity (v): n = ¦ ´ l where ¦ = frequency and l = wavelength in material. Focal length of the transducer is dependent on acoustic velocity of the particular material.

Frequency (f): ¦ = n ¸ l . Lower frequency provides deeper penetration, but higher frequency provides better resolution. Transducer frequency ranges from » 5 MHz to 150 MHz.

The minimum detectable defect: this should be greater than or equal to _ l .

Sound reflectance (Pr ): Pr = , where Z1 is the acoustic impedance of the first material, and Z2 is the acoustic impedance of the second material.


Peak Amplitude C-scan


Phase Inversion C-scan

Three factors control resolution:

  • The diameter of the acoustic beam

  • The transducer frequency

  • The focal convergence

The Inspection Modes are:

  • Pulse-Echo can determine which interface is delaminated and provides images with a high degree of spatial detail.

  • Thru Transmission uses two transducers and in one scan can reveal delamination at all interfaces with less spatial resolution than pulse-echo.

Acoustic imaging relies upon both science and experience. IAL can provide you with both to ensure a proper interpretation of the images.