A delamination of the surface-breaking paddle has been detected, extending from the edge of the package to the die a critical anomaly. This type of internal defect poses a significant risk, as it may allow water and other contaminants to enter from the external environment. Such ingress can lead to die disbonding or full detachment from the die paddle, commonly known as “lifted die.”
For identifying such internal defects in plastic packages, Scanning Acoustic Microscopy (SAM) stands out as the most sensitive and non-destructive inspection technique. This technical note presents a comprehensive inspection of a dual switching diode, showcasing the detection of critical delamination using C-SAM.
Sample & Method
The inspected component is a Dual Switching Diode in a plastic SOT-416 package. Confocal Scanning Acoustic Microscopy (C-SAM) is performed using both reflection and transmission modes at 50 MHz.
To enhance defect identification, a phase inversion algorithm was applied to highlight regions exhibiting delamination. In addition, A-Scan analysis was used to confirm the presence and characteristics of the detected anomalies.
The inspection follows the acceptance/rejection criteria defined in ESCC 25200.
Findings & Observations
A thorough acoustic inspection using C-SAM revealed defects in various areas of the device:
- Minor delamination was observed at the lead fingers. This type of defect is considered acceptable according to the criteria established in ESCC 25200.
- In contrast, a critical delamination was detected at the die paddle, characterized by a surface-breaking anomaly extending from the edge of the package to the die. This defect is cause for rejection under multiple test standards, as it poses a serious risk of water and contaminant ingress from the external environment—potentially compromising the device’s reliability and functionality.
This anomaly can result in die disbonding or complete detachment from the paddle, a condition commonly referred to as a “lifted die.“
The phase inversion algorithm was effective in identifying and highlighting the delaminated areas, which were further confirmed by A-scan signals:
- A normal signal (without phase inversion) was observed in defect-free areas (left).
- A clear phase inversion signal was detected in the delaminated region (right), serving as a distinct acoustic signature of the defect.
These findings are supported by C-SAM and A-scan images, provided as visual evidence.
Additionally, a destructive cross-section was performed through the delaminated area to verify the acoustic results. The section revealed a well-defined separation line at the die paddle in the affected region. Due to the small size of the feature, imaging required the use of a high-resolution, high-magnification Scanning Electron Microscope (SEM).
It is important to note that this type of anomaly would not be detectable by radiographic testing, further underscoring the superior sensitivity of acoustic microscopy in identifying critical delaminations in plastic packages.
