Once the device is broken, don't stay away from it, but should be like a treasure.

Everyone who drives knows, where is the best way to practice driving? Highways are not good, only busy cities and bad road conditions can improve the level. The development of society is a process of discovering and solving problems. It is not terrible to have problems, but it is very terrible to have the same type of problems frequently.

 

 

Basic concepts of failure analysis

Definition: The process of diagnosing failed electronic components.

1. Failure analysis often requires electrical measurement and the use of advanced physical, metallurgical and chemical analysis methods.

2. The purpose of failure analysis is to determine the failure mode and failure mechanism, and propose corrective measures to 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.

 

General procedure for failure analysis

1. Collect field data

2. Electrical measurement and determination of failure mode

3. Non-destructive inspection

4. Open the package

5. Mirror

6. Power on and locate the failure

7. Perform physical and chemical analysis on the failure location to determine the failure mechanism.

8. Comprehensive analysis, determine the cause of failure, and propose corrective measures.

 

1. Collect field data:

Type of stress

experiment method

Possible main failure modes

Electrical stress

Static electricity, excessive electricity, noise

Gate breakdown of MOS devices, pn junction breakdown of bipolar devices, secondary breakdown of power transistors, latch-up effect of CMOS circuits

Thermal Stress

High temperature storage

Al-Si in metal-semiconductor contact is mutually soluble, ohmic contact is degraded, pn junction leakage, Au-Al bonding failure

Low temperature stress

Low temperature storage

Chip break

Low temperature electrical stress

Low temperature work

Hot carrier injection

High and low temperature stress

High and low temperature cycle

Chip breakage, chip bonding failure

Thermoelectric stress

High temperature work

Metal electromigration, ohmic contact degradation

Mechanical stress

Vibration, shock, acceleration

Chip breakage, lead breakage

Radiation stress

X-ray radiation, neutron radiation

Electrical parameter changes, soft errors, latch-up effects of CMOS circuits

Climatic stress

High humidity, salt spray

Outer lead corrosion, metallization corrosion, electrical parameter drift

2. Electrical measurement and determination of failure mode

Electrical measurement failures can be divided into connectivity failures, electrical parameter failures and functional failures.

Connectivity failures include open circuits, short circuits, and resistance changes. This type of failure is easy to test, and most of the field failures are caused by electrostatic discharge (ESD) and electrical stress (EOS).

 

 

The electrical parameters are invalid, and more complicated measurements are required. The main manifestations are that the parameter value exceeds the specified range (out of tolerance) and the parameter is unstable.

To confirm that the function is invalid, input a known excitation signal to the component and measure the output result. If the measured output state is the same as the predicted state, the component function is normal, otherwise it is invalid. The function test is mainly used for integrated circuits.

 

      The three types of failures have a certain correlation, that is, one type of failure may cause other types of failures. The root cause of functional failure and electrical parameter failure can often be attributed to connectivity failure. In the absence of complex functional testing equipment and testing procedures, it is possible to use simple connectivity testing and parameter testing methods for electrical testing, combined with the application of physical failure analysis techniques to still obtain satisfactory failure analysis results.

3. Non-destructive inspection

 

name

Application advantage

Main principle

X-ray fluoroscopy

With the low-density area as the background, observe the density anomalies in the high-density area of ​​the material

The abnormality of X-ray imaging after being partially absorbed by the sample

Reflection scanning acoustic microscopy (C-SAM)

Take the high-density area as the background to observe the voids or low-density areas inside the material

Ultrasonic wave is hindered and reflected by the gap

X-Ray inspection is to use X-ray to see through components (multiple directions and angles are optional) without destroying the chip, to detect the packaging of components, such as bubbles, abnormal bonding wires, die size, and bracket direction Wait.

picture

　　Applicable scenarios: check whether there is any abnormality in the bonding, whether the package is defective, confirm the die size and layout

　　Advantages: short construction period, intuitive and easy to analyze

　　 Disadvantage: limited access to information

　　 Limitations:

　　 1. The internal shapes of the devices of the same batch of devices in different packaging production lines are slightly different;

　　2. The internal circuit damage or defect is difficult to detect, and it must be obtained through functional tests and other tests.