PCB News - PCB manufacturers, the damage of static electricity to electronic products

PCB manufacturers, the damage of static electricity to electronic products

The damage of static electricity to electronic products has many forms and has its own characteristics.

Forms of electrostatic damage

The basic physical properties of static electricity are: attraction or repulsion; there is a potential difference with the earth; it will produce a discharge current. Based on this, electrostatic damage has the following three forms:

(1) Electrostatic adsorption of dust reduces the insulation resistance of components (shortens the life);
(2) Electrostatic discharge (ESD) damage, causing electronic components to be damaged and unable to work (complete destruction);

(3) The electromagnetic field generated by electrostatic discharge has a large amplitude (up to several hundred volts/m) and a very wide frequency spectrum (from several gigabytes in time), which can cause interference or even damage to electronic devices (electromagnetic interference).

The damage of these three forms of static electricity to electronic products may be permanent (such as loss of function and cannot be restored), or temporary (such as interference caused by electrostatic discharge to temporarily lose function); or it may be sudden. A failure may also be a potential failure. Among them, electrostatic discharge (ESD) events are the most common and main cause of component damage.

Characteristics of electrostatic damage

Compared with other stresses, electrostatic damage to electronic products has the following characteristics.

(1) Concealment

The human body cannot directly perceive static electricity unless electrostatic discharge occurs, 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 electrostatic damage is concealed.

(2) Potentiality and accumulation

The performance of some electronic components is not significantly reduced after being damaged by static electricity, but multiple cumulative discharges will cause internal damage to the device and form a hidden danger. Therefore, static electricity has the potential to damage electronic products.

(3) Randomness

Under what circumstances will electronic components suffer electrostatic damage? It can be said that after a component is generated, until it is damaged, all processes are threatened by static electricity, and the generation of static electricity is random, so static damage is also random.

(4) Complexity

The failure analysis of electrostatic discharge damage is time-consuming, labor-intensive, and costly due to the fine, fine, and tiny structural characteristics of electronic products. It requires high technology and often requires the use of high-precision instruments such as scanning electron microscopes. Even so, some electrostatic damage phenomena are difficult to distinguish from damage caused by other causes, making people mistakenly regard electrostatic damage failures as other failures. Before the ESD damage is fully understood, it is often attributed to early failure or unknown failure, which unconsciously conceals the true cause of the failure. Therefore, the analysis of electrostatic damage to electronic products is complicated.

Manufacturing process that may cause electrostatic damage
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Components may suffer electrostatic damage during the whole process from production to use, which can be divided into:
(1) Component manufacturing process-including manufacturing, cutting, wiring, inspection and delivery;
(2) PCBA board production process-receiving, acceptance, storage, insertion, welding, quality control, packaging to shipment;
(3) Equipment manufacturing process-circuit board acceptance, storage, assembly, quality control and shipment;
(4) Equipment use process-receiving, installation, testing, use and maintenance;
(5) Equipment maintenance process.

In this whole process, at every small step in every stage, the components may be damaged by static electricity. In fact, the most important and easily neglected point is the transmission and transportation of the components. In this process, not only the packaging is prone to static electricity due to movement, but the entire packaging is easily exposed to external electric fields (such as passing near high-voltage equipment, frequent workers moving, vehicles moving quickly, etc.) and damaged. Therefore, special delivery and transportation processes are required. Pay attention and reduce losses.
Therefore, electrostatic damage may occur in any link from component manufacturing, assembly, use to maintenance.

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