Static Electricity And Hazards in Cleanrooms

Generation and hazards of static electricity in Cleanroom

Principles of Static Electricity Generation

Static electricity of Clean Room is the product of electrons moving within or between materials (including polarisation and conduction). Two different materials in contact with each other, the distance between them is less than a certain distance, such as 10-25cm, due to the tunneling effect, the two materials within the electrons across the interface and mutual exchange. When the exchange reaches equilibrium, the material will produce a certain potential difference between the interface on both sides of the equal amount of positive and negative charges. If the contact after the two materials are separated, the two materials will be charged with equal amounts of positive and negative charges, which is the basic principle of electrostatic generation.

The generation of static electricity in Cleanrooms mainly have the following three ways:

• Friction: because of different materials of objects in contact and then separated, due to different atomic nuclei on the binding capacity of electrons is different, when two different materials material contact or friction, the peripheral electrons will be transferred to the binding capacity of the larger party, resulting in a material with a positive charge, the other material with a negative charge.

• Conducting charged: because in the case of a conductor, electrons can move freely on his surface. When in contact with a charged body, the electrons are transferred from the occurring charge, resulting in a balance of charge between the two, thus creating an electrostatic phenomenon.

• Induction charged: is the induction of neighbouring electric field, for conductors, electrons move freely on the surface of the conductive material, if the conductor is placed in another electrostatic field, due to the homogeneous charges repel each other, and the heterogeneous charges are attracted to each other, the positive and negative ions will be transferred, the conductor due to the induction of the electrostatic field resulting in positive and negative charge imbalance and the formation of charged.

Hazards of static electricity

Electrostatic hazards have some different characteristics from general lightning protection or electromagnetic interference. For example:

• Concealment: general electrostatic discharge is not perceived by the human body, while the components are unknowingly damaged.

• Potential and cumulative: some components are damaged by electrostatic discharge, only show a decline in some performance parameters, but has not yet failed, in the case of continued use may lead to failure, so electrostatic damage to the device has the potential.

• Randomness: electronic components of electrostatic discharge damage may be in the product from processing to manufacturing to the use of maintenance of any link, any step, and any relevant charged human (or object) contact occurs, has a strong randomness.

• Complexity: some electrostatic damage is also difficult to distinguish from other causes of damage, so that people mistakenly take the electrostatic damage failure as other failures, so as to make a wrong judgement.

For the assembly of electronic products, static hazards seriously affect the quality of the product, yield and reliability, must be used for the assembly of electronic products in the purification room for systematic anti-static measures to minimise the degree of static hazards in the production process.