How to protect against static electricity in electronic equipment
Electrostatic discharge (ESD) is a familiar and underestimated source of circuit board and component damage in electronic assembly. It affects every manufacturer, regardless of its size. Although many people think that they are producing products in an ESD safe environment, in fact, ESD-related damage continues to cost the world's electronics manufacturing industry billions of dollars a year. ESD occurs very quickly with extremely high intensity, and usually generates enough heat to melt the internal circuits of the semiconductor chip, and looks like small bullets/bullet holes blown out under the electron microscope, causing immediate and irreversible damage.
What's more serious is that only one-tenth of this hazard is so bad that the entire component tested in the final test fails. In the other 90% of cases, ESD damage causes only partial degradation-meaning that the damaged component can pass the final test unnoticeably, and only has premature field failure after shipment to the customer. The result is the worst reputation and the most costly place for a manufacturer to correct any manufacturing defect.
The main product used to prevent ESD is a wristband, with curled corduroy and a dissipative surface or anti-static rubber mat-both must be properly grounded. Additional aids such as dissipative footwear or heel straps and suitable clothing are designed to prevent personnel from accumulating and maintaining a net charge when moving in an electrostatic protected area (EPA).
During and after assembly, the PCB should also prevent ESD from internal and external transportation. There are many circuit board packaging products that can be used in this area, including shielding bags, shipping boxes and movable carts. Although the correct use of the above equipment will prevent 90% of ESD-related problems, in order to reach the last 10%, another kind of protection is needed: ionization. The most effective way to neutralize assembly equipment and surfaces that can generate electrostatic charges is to use an ionizer-a device that blows out a stream of ionized air over the work area to neutralize any electrical charge accumulated on the insulating material.
Due to the use of ionizers, manufacturers can accept the fact that some insulating materials appear in their EPA. Because the ion generation system continuously neutralizes any charge accumulation that may occur on the insulator, they are a reasonable investment for any ESD program.