How to remove IC chip packaging? Anatomical detection of electronic components

Date：2022-01-04 15:24:00 Views：1749

Component unsealing, also known as component cover opening and cap opening, is a commonly used destructive detection method in failure analysis. Generally speaking, that is to do surgery on the chip. Through unsealing, we can intuitively observe the internal structure of the chip. After unsealing, we can judge the current situation and possible causes of the sample in combination with OM analysis.

Meaning of unsealing: decap refers to unsealing, also known as cover opening and cap opening. It refers to local corrosion of the fully encapsulated IC, so that the IC can be exposed, while maintaining the integrity of the chip function, and keeping die, bond pads, bond wires and even lead - from damage, so as to prepare for the next chip failure analysis experiment, facilitate observation or other tests (such as FIB and Emmi). The function after decap is normal.

Unsealing scope: common package cob, BGA, QFP, QFN, sot, to, dip, BGA, cob, ceramic, metal and other special packages.

Unsealing methods: generally chemical unsealing, mechanical unsealing, laser unsealing and plasma decap

Kaifeng laboratory: decap laboratory can handle almost all IC packaging forms (COB, QFP, dip, sot, etc.) and wiring types (Au Cu Ag).

Under the action of hot concentrated nitric acid (98%) or concentrated sulfuric acid, the polymer resin is corroded into a low molecular compound easily soluble in acetone. Under the action of ultrasound, the low molecular compound is washed away to expose the surface of the chip.

Unsealing method 1: take a stainless steel plate, lay a thin layer of yellow sand on it (or heat the product directly on the steel plate), heat it on the electric furnace, the sand temperature should reach 100-150 degrees, put the product on the sand, the front of the chip faces upward, and use a straw to absorb a small amount of fuming nitric acid (concentration > 98%). Drop it on the product surface. At this time, the resin surface has a chemical reaction and bubbles appear. After the reaction stops, drop it again. After dropping 5-10 drops continuously, clamp it with tweezers and put it into a beaker containing acetone. After cleaning in an ultrasonic machine for 2-5 minutes, take it out and drop it again. Repeat this until the chip is exposed. Later, clean it again with clean acetone to ensure that there is no residue on the chip surface.

Unsealing method 2: Boil all products in 98% concentrated sulfuric acid at one time. This method is more suitable for the case of large quantity and only depending on whether the chip is broken. The disadvantage is that the operation is dangerous. Master the essentials.

Precautions for unsealing: all operations shall be carried out in the fume hood and acid proof gloves shall be worn. The more the product is opened to the back, the less acid should be dropped and cleaned frequently to avoid excessive corrosion. During cleaning, the tweezers shall not touch the gold wire and chip surface to avoid scratching the chip and gold wire. According to the product or analysis requirements, some conductive adhesive under the chip shall be exposed after opening the cap, Or the second point In addition, in some cases, the open cap products shall be retested according to the row. At this time, first observe whether the gold wire on the chip is broken and collapsed under an 80x microscope. If not, scrape the black film on the pin with a blade and send it for measurement. Pay attention to control the opening temperature not too high.

Acid commonly used in analysis: concentrated sulfuric acid. This refers to 98% concentrated sulfuric acid, which has strong dehydration, water absorption and oxidation. When opening the cap, it is used to cook a large number of products at one time. Here, its dehydration and strong oxidation are used. Concentrated hydrochloric acid. It refers to 37% (V / V) hydrochloric acid with strong volatility and oxidation. It is used to remove the aluminum layer on the chip in the analysis. Fuming nitric acid refers to nitric acid with a concentration of 98% (V / V). To open the hat. It has strong volatility and oxidation, and is reddish brown due to the dissolution 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 rot gold ball in analysis because it is highly corrosive and can corrode gold.

In short, the top metal cover is mainly used to protect internal components, but there is still a certain distance between the core chip of the processor and the top metal cover, and the general heat conduction effect of silicone grease is certainly not as good as that of liquid gold (liquid metal). When the core chip is heated, the liquid gold can better transmit heat to the top cover, Achieve better heat dissipation performance.