What are the common ideas and methods for chip failure analysis?

Date：2022-10-17 17:12:36Views：747

In general, failure of integrated circuits is inevitable in the process of development, production and use. Due to the continuous improvement of people's requirements for product quality and reliability, failure analysis is becoming more and more important. Through chip failure analysis, IC designers can find design defects, mismatch of process parameters, or improper design and operation problems. The following is a brief analysis of common ideas of chip failure analysis for your reference.

Specifically, the significance of failure analysis is mainly shown in the following aspects:

1. Failure analysis is a necessary means to determine the chip failure mechanism;

2. Failure analysis provides necessary information for effective fault diagnosis;

3. Failure analysis provides necessary feedback information for design engineers to continuously improve or repair the chip design to make it more consistent with the design specification;

4. Failure analysis can evaluate the effectiveness of different test vectors, provide necessary supplements for production testing, and provide necessary information basis for verification testing process optimization.

Common ideas and methods for chip failure analysis:

1. X-RAY inspection

X-RAY rays, a kind of electromagnetic radiation with very short wavelength, can penetrate many solid substances that cannot be penetrated by ordinary light. The X-RAY analyzer in the reliability analysis room can be used to check the gold wire condition of the product, the air hole condition in the resin body, the bubbles in the conductive adhesive under the chip, and the distribution range of the conductive adhesive.

2. Ultrasonic cleaning

Cleaning is only used to analyze the components with abnormal electrical performance, and the failure may be related to the contamination of the shell or chip surface. At this time, it should be confirmed that there is no leakage in the package, so as to remove the contamination on the housing. Before cleaning, remove any sundries on the surface and re measure the electrical parameters. If it still fails, clean it again. After cleaning, measure the electrical parameters and compare the changes of electrical parameters before and after cleaning. The cleaning agent shall not damage the shell. Generally, acetone, ethanol and toluene shall be used. After cleaning, pure water shall be used for cleaning. Finally, acetone and absolute ethanol shall be used for dehydration and drying. The cleaning shall ensure that there is no failure caused by the cleaning agent.

3. Uncovering

Under the action of hot concentrated nitric acid (98%) or concentrated sulfuric acid, the polymer resin body is decomposed into low molecular compounds that are easily soluble in acetone. Under the action of ultrasound, the low molecular compounds are washed away, exposing the chip surface.

4. Internal visual inspection

Depending on the product, place it under a 200x or 500x metallographic microscope or stereo microscope to carefully observe whether there are cracks, broken aluminum, scratches, burns, contamination and other abnormalities on the chip surface. For the chip crack, open the cap from the reverse side to observe whether there is a bad point at the top of the thimble when installing the chip on the reverse side, because the chip is easy to crack when removing the chip by opening the cap from the front side. The conductive adhesive on the reverse side can be slowly corroded with nitric acid, and then gently scraped off with a soft thin copper wire.

5. External visual inspection

Whether there are cracks in the resin body, short circuit caused by impurities between the pins, whether the pins are pulled out of the resin body, whether copper is exposed at the root of the pins, whether the pins and the resin body are contaminated, whether the pins are bent and deformed, etc.

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