These are the main products used to prevent static electricity
(Wristband), with curled corduroy and dissipative surface or bedding-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 the 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.
A common fallacy is that because the bowl belt is worn at the workstation, the insulator in the area, such as a polystyrene cup or cardboard box, will safely dissipate the charge. By definition, an insulator does not conduct electricity, except that it is impossible to discharge through ionization.
If a charged insulator remains in the EPA, it will radiate an electrostatic field, triggering a net charge to any nearby objects, thus increasing the risk of ESD damage to the product. Although many manufacturers attempt to ban insulating materials from their EPA, this method is difficult to implement. Insulation is too much part of everyday life-from the foam cushion that the operator sits on comfortably, to something in the plastic cover.
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.
There are two basic forms of ion-generating equipment in standard electronic assemblies:
*Desktop type (single fan)
* Over-the-top equipment (in a single overhead unit, there are a series of fans)
There are also indoor ion generators, but they are mainly used to clean the room environment.
The choice depends on the size of the area to be protected. The desktop ionizer will cover a single working surface, while the overhead ionizer will cover two or three. Another advantage is that the ionizer can also prevent dust from statically adhering to the product, which may degrade the appearance.
However, if there is no normal testing and monitoring of the effectiveness of ESD equipment, then no protection plan is perfect. Leading ESD control and ionization experts reported examples of manufacturers who used failed (and therefore useless) ESD equipment without knowing the failure.
In order to prevent this situation, in addition to standard ESD equipment, ESD suppliers also provide various constant monitors, which automatically alarm if a performance exceeds the regulations. The monitor can be used as an independent unit or connected together in a network. There is also network software for automatic data collection, which displays the system performance of related operators and workstations in real time.
The monitor can simplify ESD planning by eliminating many daily tasks, such as ensuring that the bowl belt is properly measured every day, the ionizer is balanced and properly maintained, and the workbench ground point is not damaged.
The first step to prevent ESD is to correctly evaluate how small details may cause irreparable damage if ignored. An effective plan requires not only the use of effective ESD protection equipment, but also strict operating procedures to ensure that the behavior of all factory floor personnel is ESD safe.
Although many manufacturers use automatic bowl strap testers, it is often seen that operators pass the test or fail because the bowl strap is too loose. Many operators attempt to pass the test by simply holding the tester close to their wrist with the other hand.