Basic concepts of failure analysis
1. Failure analysis often requires electrical measurements and advanced physical, metallurgical and chemical analysis methods.
2. The purpose of failure analysis is to determine the failure mode and failure mechanism, propose corrective measures, and prevent the recurrence of this failure mode and failure mechanism.
3. Failure mode refers to the observed failure phenomenon and failure form, such as open circuit, short circuit, parameter drift, functional failure, etc.
4. Failure mechanism refers to the physical and chemical process of failure, such as fatigue, corrosion and overstress.
Significance of failure analysis
1. Failure analysis is a necessary means to determine the failure mechanism of the chip.
2. Failure analysis provides the necessary information for effective fault diagnosis.
3. Failure analysis provides necessary feedback information for design engineers to continuously improve or repair chip design to make it more consistent with design specifications.
4. Failure analysis can evaluate the effectiveness of different test vectors, provide necessary supplements for production tests, and provide the necessary information basis for verification test process optimization.
Main steps and content of failure analysis
Chip unpacking:
Remove the IC sealant, while keeping the chip function intact, keep the die, bondpads, bondwires and even the lead-frame from damage, and prepare for the next chip failure analysis experiment.
SEM scanning electron microscope/EDX component analysis:
Including material structure analysis/defect observation, conventional micro-area analysis of element composition, precise measurement of component dimensions, etc. Probe test: Use micro-probes to quickly and conveniently obtain internal electrical signals of ICs.
Laser cutting:
Use micro-laser beam to cut off specific area of circuit or upper layer of chip.
EMMI detection:
EMMI low-light microscope is a highly efficient failure analysis tool, providing a highly sensitive non-destructive fault location method, which can detect and locate very weak light (visible light and near-infrared light), thereby capturing various Leakage current generated by component defects or abnormalities is visible to light.
OBIRCH application (laser beam induced impedance change test):
OBIRCH is often used in the analysis of high and low impedance inside the chip, and the analysis of line leakage paths. Using the OBIRCH method, defects in circuits can be effectively located, such as holes in lines and holes under vias. The high-resistance area at the bottom of the through hole, etc., can also effectively detect short circuits or leakage, which is a powerful supplement to luminescence microscopy.
LG LCD hotspot detection:
Using liquid crystal to sense the molecular arrangement and recombination at the leakage of IC, under the microscope, it presents a patchy image different from other areas, and finds the leakage area (failure point exceeding 10mA) that troubles designers in actual analysis.
Fixed-point/non-fixed-point chip grinding:
Remove the gold bumps planted on the LCD driver chip Pad, and keep the Pad intact for subsequent analysis or rebonding.
X-Ray non-destructive detection:
Detect various defects in IC packaging such as layer peeling, bursting, voids and integrity of bonding wires, possible defects in PCB manufacturing such as poor alignment or bridging, open circuits, short circuits or abnormal connection defects, solder balls in packages integrity.
SAM (SAT) ultrasonic flaw detection:
It can conduct non-destructive inspection on the internal structure of IC packaging, and effectively detect various damages caused by water vapor or heat energy, such as: delamination of wafer surface, cracks in solder balls, wafers or glue filling, packaging The pores inside the material, o various holes such as the holes in the bonding surface of wafers, solder balls, glue filling, etc.
