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Requirements on a Class "0" EPA
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Authored By:Dipl.-Ing. Hartmut Berndt B.E.STAT European ESD competence centre Kesselsdorf, Germany, Saxony SummaryLately, more and more publications report about ESD requirements for an EPA "class 0". What does this mean? This point is not described in the ESD standards ANSI/ESD S20.20 and the IEC standard IEC 61340-5-1. The electronic industry follows these rules when it comes to the protection of electronic components and assemblies against electrostatic discharges. Only one standard divides electronic components into certain hazard classes, the HBM standard IEC 61340-3-1 (ANSI/ESDA/JEDEC JS001-2012). According to this classification, class "0A" means a maximum electrostatic voltage of 125 volt. Class "0B" means an electrostatic voltage between 125 and 250 volt. The typical requirement for an EPA according to the ESD standards (ANSI and IEC) is a maximum electrostatic voltage of 100 volt. At the moment, the requirements for the electronic industry are higher than for other industries. Most of the EPAs meet these requirements. Some semiconductor manufacturers demand a voltage of 0 volt for their electronic components within the handling area of an EPA. Is it possible to implement such requirements? Most of the ESD equipment on the market only grants the requirements up to 100 volt. Thus, how does the material have to be developed? Currently, only special ionizers are suitable to meet the target. Typical ionizers only guarantee a minimum of 100 volt, high specialized ones 10 volt (residual charge or balance). An optimized ESD Control System for machines with focus on cost-effectiveness is presented later. All electronic components and assemblies are exposed to risks of electrostatic discharges. Producers, suppliers, distributors and users have to perform the ESD control system during the whole manufacturing process, the measurements as well as during the applications. All active electronic components, beginning with simple diodes, transistors or complex inner circuits, require an extern ESD control system. In the next step, SMD resistors and condensers, and prospectively NEMS and MEMS are included in this danger category. Tests show that these passive components can be damaged through electrostatic discharges. The structures of electronic components become smaller and smaller. 5 volt of an electrostatic charge are already enough to change the structures in small electronic components. The structures will achieve such small dimensions, so that electrostatic charges can cause permanent damages. In the year 2024 the sizes of the electronic components will be less than 10 nm. Then, electrostatic charges of 0.1 nC and electrostatic fields of 10 volt /cm (or 1000 volt /m) will be enough to damage ESDS permanently. ConclusionsThe requirements "0 volt" can be achieved, when die maximum value will be required. Unfortunately, today we do not have any ESD material, which requires these limits. The biggest problems are machines and automated handling equipment (AHE), because very small charges are generated in these machines, independent from persons. These small and fast discharge procedures are energy-intensive. They cause damages of electrostatic sensitive devices and assemblies. The grounding of all metal parts does not suffice. New processes, which either discharge very small electrostatic charges fast or prevent theses discharges, have to be developed. The only way to meet such requirements is precisionionization. All other ESD equipment have more than 0 volt. Even with a limit value of 125 volt (Level 0A) it is hard to find suitable ESD material. A further attempt is to classify ESD control areas in different zones. 1. Basic control requirements 2. Advanced control requirements 3. Extended control requirements Until now, there are not any different requirements for these areas, defined in an ESD control program. Initially Published in the SMTA Proceedings |
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