Main source of static electricity for electronic components
In the electronics manufacturing industry, the source of static electricity is multi-faceted, such as human body, plastic products, related equipment and electronic components themselves. 1. Human body static electricity The human body is the most important static power source. There are three main reasons. First, the human body has a wide contact surface and a large range of motion. It is easy to be in contact with or frictional with an electrostatically charged object, and there are many opportunities to transfer the charge carried by the body itself to the device or discharge through the device. Second, the capacitance between the human body and the earth is low, about 50-250pF, and the typical value is 150PF, so a small amount of static charge can cause a high electrostatic potential. Third, the human body's resistance is low, equivalent to a good conductor, such as the resistance between the hand and the foot is only a few hundred ohms, the contact resistance generated by the finger is several thousand to several tens of kilo ohms, so the human body is easy to sense in the electrostatic field. When the electricity is activated, and a part of the human body is charged, the whole body can be charged. 2. Static electricity of instruments and equipment Instruments and equipment can also be electrostatically charged due to friction or static induction. For example, the transmission belt is electrostatically generated due to contact and separation with the rotating shaft during transmission, or the metal casing of the instrument with poor grounding induces static electricity in the electric field. When the instrument is energized, it will also generate electrostatic discharge when it comes into contact with the components, causing electrostatic damage. 3. Electrostatics of the device itself The outer casing of the electronic component (mainly ceramic, glass and plastic packaged case) rubs against the insulating material and also generates static electricity. After the device case generates static electricity, it will discharge static electricity through a grounded pin or an external lead, which will also cause electrostatic damage to the device. 4. Other electrostatic sources In addition to the above three electrostatic sources, in the process of manufacturing, installing, transferring, transporting, testing, storing, measuring and debugging electronic components, various kinds of insulating materials will be encountered. Items that rub against each other or rub against the human body produce a high electrostatic potential.
