Reasons for static electricity generation
We know that matter is composed of molecules, which are composed of atoms containing negatively charged electrons and positively charged protons. Under normal circumstances, an atom has the same number of protons and electrons, with positive and negative balances, thus exhibiting a phenomenon of being uncharged externally. However, electrons orbit around the atomic nucleus and once subjected to external force, they leave their orbit and enter other atoms, causing the atom to become positively charged due to a lack of electrons, while other atoms become negatively charged due to an increase in the number of electrons. The excess or insufficient relatively static electric charge carried on the surface of this object is called static electricity. The ways to cause static electricity usually include solid electrification, induction electrification, friction electrification, human body electrification, and so on.
There are three main forms of human electrification. One is contact separation electrification, which refers to the friction between clothing and external substances during activities, and the contact separation between shoes and the ground. The second is induced charging; The third is adsorption charging. When the human body moves in a space with charged particles, the charged particles are adsorbed by the human body, making the human body charged. Some external factors have a significant impact on the generation of static electricity, with the most important being the human body and humidity.
human factors
Due to continuous movement, the human body is easily charged with static electricity; Insulating materials such as human skin, hair, and body can store a considerable amount of electrostatic charges; Due to human operation, static electricity from the human body is transmitted (emitted) to components or devices.
Low humidity (dry air)
Humidity has a significant impact on the accumulation and dissipation of static electricity. When the humidity is low, the electrostatic potential is high; When the humidity is high, the electrostatic potential is low. This is mainly because when the humidity is high, water molecules (sometimes conductive impurities) are adsorbed on the surface of the insulation material, which reduces insulation and facilitates electrostatic leakage. Different substances are affected by humidity differently. Those with high hygroscopicity are easily wetted by moisture and are greatly affected by humidity; Low moisture absorption and less affected by humidity. Like glass surfaces, they are easily wetted by water, while substances such as paraffin and polytetrafluoroethylene that are not easily wetted by water are less affected by humidity.
Types of materials in contact
The size of static electricity generated by different materials varies, especially synthetic materials, ordinary plastics, and insulators are more prone to generating or storing static electricity.
Electrostatic Discharge (ESD)
The so-called electrostatic discharge refers to the transfer of electrostatic charges between objects with different electrostatic potentials due to direct contact or electrostatic induction. This is the phenomenon where the energy of the electrostatic field reaches a certain level, and then the dielectric is broken down and discharged.
The hazards of static electricity in the electronics industry
The impact of electrostatic discharge on the human body does not seem significant, but in the production process of electronic components, or in the installation, debugging, and inspection process of electronic products, if static electricity is not eliminated, it will affect production or reduce product quality. Especially in the semiconductor device and microcircuit production industries, electrostatic discharge can cause device failure.
With the rapid development of science and technology, the rapid rise of high-tech industries such as electronics, postal and telecommunications, and aerospace, there is a growing demand for electronic products such as electronic instruments, meters, and equipment to become increasingly miniaturized, multifunctional, and intelligent. High density integrated circuits (such as MCUs) have become indispensable components in the electronic industry for the above requirements. This type of device has the characteristics of short line spacing, thin lines, high integration, fast operation speed, low power, low voltage resistance, and high input impedance, which makes it increasingly sensitive to static electricity. The energy of electrostatic discharge (ESD) has little impact on traditional electronic components and is difficult for people to detect. However, in these high-density integrated circuit components, whether they are MOS devices or bipolar devices, they may fail due to electrostatic fields and discharge currents, or cause "soft breakdown" phenomena that are difficult to detect, leaving potential hazards to the entire machine and directly affecting the quality, lifespan, reliability, and economy of electronic products.
The breakdown damage of electronic components caused by electrostatic discharge is the most common and serious electrostatic hazard in the electronics industry, which can be divided into immediate failure and delayed failure.
Instant failure refers to the one-time occurrence of dielectric breakdown, burning, or permanent failure of electronic components. Delay failure refers to the degradation of device performance or a decrease in parameter indicators, which means that even if the product has passed all inspections and tests, it may still fail after being delivered to the customer.