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Two sapphire substrates were bonded using a fresnoite glass thin film as a sealant, by irradiation with a 1,064 nm ns laser. The sapphire close to the interface was examined by TEM, showing some structural defects due to the laser processing. Bond quality and strength were evaluated by scanning acoustic microscopy (SAM) and micro-chevron testing, respectively. Optimization of laser parameters lead to an improved processing speed (>1 mm/s) as well as an enhanced fracture toughness to 1.23 MPa m1/2

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In this paper the performance of multi-narrow-band spectral analysis was evaluated concerning defect detection in microelectronic components with flip-chip contacts. Today, flip-chip technology is widely applied for interconnecting silicon dies to a substrate within high-end semiconductor packaging technologies. The integrity of the bump solder interconnection is of major concern for the reliability in this technology. Non-destructive defect localization and analysis of the flip-chip interconnections operating in a semi-automated mode is strongly desired. Scanning acoustic microscopy (SAM) combined with subsequent signal analysis has high potential for non-destructive localization of defective flip-chip interconnects. Analyzing multiple narrow spectral bands of signals acquired by a scanning acoustic microscope enabled the identification and localization of defective flip-chip interconnects. In the current study a 180 MHz transducer with 8 mm focal length was employed f or acoustic data acquisition by SAM. Those data were then analyzed off-line by discrete Fourier transformation, chirp z-transform and cosine transform using custom made MATLAB software. Through multi-narrow band spectral analysis, defective flip-chip interconnects that have not been revealed by standard acoustical imaging methods have been detected successfully. Acoustically found defects have been confirmed by subsequent FIB-cross sectioning and SEM imaging. The high resolution SEM imaging revealed complete and partial delamination at the interface between the die and the bump

Metal-based thermocompression bonding enables the creation of hermetic seals formed at relatively low processing temperatures and occupying a small portion of the device area. In the current study we have investigated the application of scanning acoustic microscopy (SAM) for assessing the quality of metal thermocompression bonds, both by evaluating its capabilities of localizing areas of poor bonding, and by finding defects in the integrity of the bond seal. Wafer laminates containing a test vehicle with pre-defined defects in the bond metal layer were sealed by Au-Au and Al-Al thermocompression bonding. Employing SAM, an area of 5 chips of poor bonding was identified non-destructively on the Al-Al laminate.Line defects of width 3.6 µm and point defects of diameter 22.4 µm have also been identified by SAM. The dicing yield for sealing frames was above 96% for all frame structures and both bond metal systems. The average bond strength was 31.5 ± 11.9 MPa for Al-Al thermocompression bonds and 37.3 ± 9.7 MPa for Au-Au thermocompression bonds.Scanning acoustic microscopy operates non-destructively and proved to be an extremely useful tool complementing current state-of-the-art methods for bond quality assessment.