- Posted by doEEEt Media Group
- On April 26, 2022
Complementary non-destructive testing
The Scanning Acoustic Microscopy (SAM) technique is the most effective and complete non-destructive approach for the detection of critical and latent anomalies within plastic encapsulated parts, either on assembled or non-assembled systems: Therefore, it is routinely used and required to screen out potentially defective parts before the implementation into different industrial sectors such as automotive, military industry, avionics, space applications, and others.
Such a technique is sensitive to density changes, making it reliable and accurate in detecting “air-gap anomalies” such as delaminations, voids, and cracks.
The difficulty of this technique when carrying out the inspection is due to its non-destructive nature. This makes it impossible to know the device’s internal structure in advance. For that reason, preliminary X-ray inspection is systematically conducted to identify the critical focal planes for multifocal SAM inspections. However, the X-Ray inspection does not detect the “air-gap anomalies” spotted by SAM. For that reason, SAM and X-Ray are complementary techniques.
The picture above shows a case where a void was detected during SAM inspection. This anomaly is in the same plane as a wire connecting the lead frame to the die, potentially endangering the mechanical stability of the structure and affecting the functionality of the device. As you can see in the X-Ray image, there is no evidence of delamination since this technique is not sensitive to this kind of defect. However, the X-Ray image provides essential information (in this case, the presence of the wires) that is key to differentiating between a pass or reject the result.
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