Figure 1. C-SAM equipment.
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Features
C-SAM, also known as Scanning Acoustic Tomography (SAT), is a
non-destructive method for observing defects such as delamination.
By using acoustic waves, it is possible to observe not only the
sample surface, but also the internal structure. The method is
independent of the optical properties of the sample.
Because of the large reflection at the air interface, voids and
cracks inside the package of electronic components can be observed with
high sensitivity. Determination of the defect area is done by spatially
analysing the waveform of reflected or transmitted ultrasonic acoustic
waves at each measurement point. Contrary to X-ray computed tomography
(CT), it is possible to determine the adhesion state of electrodes and
bonded wafers.
Defect Analysis Examples
Semiconductor package products
Electronic components, both internally and externally.
Hole detection at the silicon wafer bonding interface
Adhesion at the bonding interface of metal plates
Adhesives, adhesive tapes, etc.
Porosity in ceramics materials
Principle
By analysing the waveform of the reflected ultrasonic wave emitted
from the probe (transducer), the internal structure the sample can be
visualized. Since the acoustic impedance changes at the interface of
different materials, the acoustic reflectance changes and hence also the
intensity of the reflected wave. This change is proportional to the
difference in acoustic impedance of the materials at each interface and
the reflections are particularly strong when one of the materials is
air. Interfaces with a large difference in acoustic impedance also
introduces a \(180{^\circ}\) phase
shift.
Figure 2. Scattering of ultra-sonic waves from a laminated (left) and
delaminated (right) surface interfaces.
Data examples
Figure 3. Photo (left) of a transistor subject to defect analysis and
specifications (right) of the observation (1) and depth information (2)
directions.
Figure 4. Top of sample (left) and depth information (right)
As shown to the left of Figure 4, strong reflections occur around the
wire in the failed product.
The right-hand side of Figure 4 shows the depth information and hence
the cross section, form which it can be judged that the defect is
located slightly above the chip-bonding tip.
Figure 5. Example of a semiconductor chip analysis. The left photo
shows the image from the acoustic wave reflection at the surface. The
right image includes also internal reflections, from which internal
wiring can be analysed.
Measurement specifications
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\[400 \times 400 \times 50\] |
\[w \times d \times h\]
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\[1\sim 307\] |
\[\text{mm}^{2}\] |
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\[\mu\text{m}\] |
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The higher the frequency, the higher the resolution, but the
transmission of the ultrasound is reduced.
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Transmission scan, water spill.
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Items for enquiries
Purpose of analysis and scope of measurement
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Shape (dimensions) and quantity
Structure and composition (material, film thicknesses)
Availability of a reference sample
Other relevant information
Caution
The following type of samples may adversely affect the sample,
equipment, and/or result, and measurement may therefore not be
possible.
Samples that cannot be immersed in water (water resistance
required)
Sample with a large surface roughness
Water-soluble components.
Samples that are not able to withstand temperatures above \(40℃\).