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The influence of electrostatic factors on IC packaging

October 30, 2020

The packaging industry belongs to the back-end production process in the entire IC production. In this process, for plastic package IC, hybrid IC or monolithic IC, there are mainly wafer thinning (grinding), wafer cutting (scribing), and core loading. (Adhesive sheet), pressure welding (bonding), packaging (encapsulation), pre-curing, electroplating, printing, post-curing, cutting ribs, tube mounting, post-sealing testing, etc. Each process has different requirements for different process environments.

The influence of electrostatic factors on IC packaging

First of all, the cause of static electricity can be seen everywhere. Today, with the rapid development of science and technology and the high degree of automation in industrial production, the harm of static electricity in industrial production is already obvious. It can cause various obstacles, limit the improvement of automation level and affect product quality. Here are the main reasons for the generation of static electricity based on the actual situation of our factory in the integrated circuit packaging and production process.

1. The construction and decoration materials in the production workshop are mostly high-resistance materials. The IC production process requires the use of a clean workshop or an ultra-clean workshop.
The particle size of dust-removing particles is required to be changed from the previous 0.3μm to 0.1μm, and the dust particle density is about 353/m3. To this end, in addition to the installation of various dust collection equipment, inorganic and organic dust-free materials must be used to prevent dust. However, the electrical performance of building materials is not considered as an indicator. There is no provision in the design specifications for clean workshops of industrial enterprises. The main interior decoration materials used in the clean workshop of IC factory are: polyurethane elastic floor, nylon, hard plastic, polyethylene, plastic wallpaper, resin, wood, white porcelain plate, enamel, plaster, etc. Most of the above-mentioned materials are polymer compounds or insulators. For example, the resistivity of plexiglass body is 1012~1014Ω/cm, and the resistivity of polyethylene body is 1013~1015Ω/cm, so the conductivity is relatively poor, and static electricity due to some reason is not easy to leak to the earth through them, resulting in the accumulation of static electricity.

2. Human body static electricity
The different movements and walking back and forth of the clean room operators, the soles of the shoes and the ground are constantly in close contact and separation, and various parts of the human body also have activities and friction. Whether it is fast walking, slow walking, or trotting, static electricity will be generated, which is the so-called walking charge; the human body stands up after moving. , The work clothes worn by the human body and the chair surface are separated after contacting the chair surface, and static electricity will also be generated. If the electrostatic voltage of the human body cannot be eliminated and the IC chip is touched, it may cause IC breakdown unknowingly.

3. Static electricity caused by air conditioning and air purification
Since IC production requires 45-55% RH, air conditioning and air purification must be implemented. The dehumidified air is sent to the clean room through the primary filter, medium efficiency filter, high efficiency filter and air duct. Generally, the wind speed of the main air duct is 8~10m/s, and the inner wall of the air duct is painted. When the dry air and the air duct, the dry air and the filter move relative to each other, static electricity will be generated. It should be noted that static electricity is more sensitive to humidity.
In addition, the transportation of semi-finished products and IC products will generate static electricity during packaging and transportation, which is one of the factors of static electricity.
Secondly, the damage of static electricity to IC is considerable. Generally speaking, static electricity has the characteristics of high potential and strong electric field. In the process of electrostatic charging and discharging, transient high current discharge and electromagnetic pulse (EMP) are sometimes formed, generating electromagnetic radiation fields with a wide spectrum.
In addition, compared with conventional electric energy, electrostatic energy is relatively small. In the natural electrification-discharge process, electrostatic discharge (ESD) parameters are uncontrollable, and it is a random process that is difficult to repeat. Therefore, its role is often affected by people. Ignored. Especially in the field of microelectronics technology, the harm it causes to us is astonishing. According to reports, the direct economic loss caused by static electricity is as high as several hundred million yuan every year. Static electricity has become a major obstacle to the development of the microelectronics industry.

In the semiconductor device production workshop, due to the adsorption of dust on the chip, the yield of ICs, especially very large scale integrated circuits (VLSI), will be greatly reduced. Operators in the IC production workshop wear clean overalls. If the human body is charged with static electricity, it is easy to absorb dust and dirt. If these dust and dirt are brought to the operation site, it will affect product quality, deteriorate product performance, and greatly reduce Ic Yield. If the radius of the adsorbed dust particles is greater than 100 μm and the line width is about 100 μm, when the film thickness is below 50 μm, the product is most likely to be scrapped.

Thirdly, the damage of static electricity to IC has certain characteristics.
(1) Concealment Unless electrostatic discharge occurs, the human body cannot directly perceive static electricity, but the human body may not feel an electric shock when electrostatic discharge occurs. This is because the electrostatic discharge voltage sensed by the human body is 2~3kv, so static electricity is concealed.
(2) Potentiality The performance of some sinks is not significantly reduced after being damaged by static electricity, but multiple cumulative discharges will cause internal damage to IC devices and form hidden dangers. Therefore, static electricity has potential to damage IC.
(3) Under what circumstances can a random IC suffer electrostatic damage? It can be said that from the production of an IC chip until it is damaged, all processes are threatened by static electricity, and the generation of static electricity is also random. Its damage is also random.
(4) The failure analysis of complex electrostatic discharge damage is time-consuming, labor-intensive, and expensive due to the fine, fine, and tiny structural characteristics of microelectronic IC products, requiring high technology and often requiring the use of highly sophisticated instruments, even so Some electrostatic damage phenomena are also difficult to distinguish from damage caused by other reasons; people mistake the failure of electrostatic discharge damage as other failures, which are often attributed to early failure or unknown conditions before the full understanding of electrostatic discharge damage The failure, thus unconsciously cover up the real cause of the failure. Therefore, it is complicated to analyze the damage of static electricity to IC.

All in all, it is necessary to establish an electrostatic protection system in the process of IC processing, production and packaging! IC packaging production lines have stricter requirements for static electricity. In order to ensure the normal operation of the production line, the overall decoration of anti-static building materials is carried out on the clean workshop, and all personnel entering and leaving the clean workshop are equipped with anti-static clothing. In addition to adopting hardware measures, the packaging company can follow the relevant national standards and the actual situation of the company. The situation has formulated corporate standards or specific requirements in terms of anti-static to cooperate with the normal operation of IC packaging production lines. With the expansion of my country’s IC packaging lines, the improvement of packaging capabilities, the increase in packaging varieties, and higher requirements for product quality and yield, correspondingly, various software and hardware requirements and the awareness of electrostatic protection for all practitioners Strengthening is even more important, and this is also playing and acting as the "main role" and "invisible killer" affecting the quality of our products. Therefore, electrostatic protection will be a major issue in the entire IC industry at present and in the future.