Chip decapping test
Project introduction
Chip decapping test is like performing a surgical operation on the chip. Through decapping, we can directly observe the internal structure of the chip. After decapping, we can combine OM analysis to judge the current status of the sample and possible causes.

Meaning of decapping: Decapping means decapping, also known as opening the cover, opening the cap, which refers to the local corrosion of the fully packaged IC so that the IC can be exposed, while keeping the chip function intact, keeping the die, bond pads, bond wires and even the lead undamaged, preparing for the next chip failure analysis experiment, convenient for observation or other tests (such as FIB, EMMI), and normal function after decap.

Chip decapping test

Scope of application
Analog integrated chip, digital integrated chip, mixed signal integrated chip, bipolar chip and CMOS chip, signal processing chip, power chip, direct plug-in chip, surface mount chip, aerospace grade chip, automotive grade chip, industrial grade chip, commercial grade chip, etc.
Unsealing methods
Generally, there are chemical unsealing, mechanical unsealing, laser unsealing, and plasma decapping.

Unsealing laboratory: Decapping laboratory can handle almost all IC packaging forms (COB.QFP.DIP SOT, etc.) and wire bonding types (Au Cu Ag). Under the action of hot concentrated nitric acid (98%) or concentrated sulfuric acid, the polymer resin body is corroded into low molecular weight compounds that are easily soluble in aceton e. Under the action of ultrasound, the low molecular weight compounds are washed away, thereby exposing the surface of the chip.

Unsealing method 1: Heat on a heating plate to a temperature of 100-150 degrees, turn the front of the chip upward, and use a pipette to absorb a small amount of fuming nitric acid (concentration>98%). Drop on the surface of the product. At this time, the resin surface will react chemically and bubbles will appear. Wait until the reaction stops and then drop again. After dropping 5-10 drops in a row, clamp it with tweezers and put it in a beaker filled with aceton e. After cleaning it in an ultrasonic cleaner for 2-5 minutes, take it out and drop it again. Repeat this process until the chip is exposed. Finally, it must be repeatedly cleaned with clean aceton e to ensure that there is no residue on the surface of the chip.

Unsealing method 2: Put all products into 98% concentrated sulfuric acid at one time and boil them. This method is more suitable for large quantities and only needs to see if the chip is broken. The disadvantage is that the operation is more dangerous. You must master the essentials.

Unsealing precautions: All operations should be carried out in a fume hood and acid-proof gloves should be worn. The closer the product is to the end of uncapping, the less acid should be dropped and the more frequently it should be cleaned to avoid over-corrosion. During the cleaning process, be careful not to touch the gold wire and the surface of the chip with tweezers to avoid scratching the chip and the gold wire. According to the product or analysis requirements, the conductive glue under the chip should be exposed after uncapping, or the second point. In addition, in some cases, the uncapped products should be retested according to schedule. At this time, you should first observe whether the gold wire on the chip is broken or collapsed under an 80x microscope. If not, use a blade to scrape off the black film on the pin and send it for testing. Pay attention to control the uncapping temperature not to be too high.

Test items

1. IC uncapping (front/back) QFP, QFN, SOT, TO, DIP, BGA, COB, etc.

2. Sample thinning (ceramics, except metals)

3. Laser marking

The dangerous chemical reagents used in uncapping are recommended not to be tried easily by those who are inexperienced. You can go to a qualified third-party laboratory.

Commonly used acids in analysis: Concentrated sulfuric acid: Here refers to 98% concentrated sulfuric acid, which has strong dehydration, water absorption and oxidizing properties. It is used to boil a large amount of products at one time when uncapping, and its dehydration and strong oxidizing properties are used here. Concentrated hydrochloric acid: refers to 37% (V/V) hydrochloric acid, which has strong volatility and oxidizing properties. It is used to remove the aluminum layer on the chip during analysis. Fuming nitric acid: refers to nitric acid with a concentration of 98% (V/V). Used for uncapping. It is highly volatile and oxidizing, and is reddish brown due to the presence of NO2. Aqua regia: refers to a mixture of one volume of concentrated nitric acid and three volumes of concentrated hydrochloric acid. It is used to corrode gold balls in analysis because it is highly corrosive and can corrode gold. Reference standards
GB/T 37720-2019 Identification card Financial IC card chip technical requirements
GB/T 37045-2018 Information technology Biometric identification Fingerprint processing chip technical requirements
GB/T 4937.19-2018 Semiconductor devices Mechanical and climatic test methods Part 19: Chip shear strength
GB/T 36613-2018 Point measurement method for light-emitting diode chips
GB/T 36356-2018 Technical specification for power semiconductor light-emitting diode chips
GB/T 33922-2017 Wafer-level test method for performance of MEMS piezoresistive pressure-sensitive chips
GB/T 33752-2017 Aldehyde substrate for microarray chips
GB/T 28856-2012 Silicon piezoresistive pressure-sensitive chips
DB35/T 1403-2013 Multi-chip integrated package LED downlight for lighting

EIA EIA-763-2002 Bare chips and chip-scale packages for automated assembly, strapped with 8 mm and 12 mm carrier tapes

DLA DSCC-DWG-01002 REV E-2002 2512 type 1.5 watt (MELF) unit