Authored By:
Hartmut Berndt, Dipl.-Ing.
B.E.STAT European ESD Competence Centre
Germany
Summary
In the latest few months of last year, more and more publications report about ESD requirements for an EPA „Class 0“. What does this mean? Means the semiconductor producer “0” voltage in the area or in the EPA. The standards ANSI/ESD S20.20-2014 and the IEC standard IEC 61340-5-1 does not describe this point. According to this classification, class “0Z” means a maximum electrostatic voltage of 50 volt in the EPA. Class “0A” means an electrostatic voltage between 50 and 125 volt. The typical requirement for an EPA according to the ESD standards (ANSI and IEC) is a maximum electrostatic voltage of 100 volt. At today, the requirements for the electronic industry are higher than for other industries. Most of the EPAs meet these requirements.
Conclusions
The 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 precision-ionization. All other ESD equipment have more than 0 volt. Even with a limit value of 50 volt or 125 volt (Level 0Z or 0A) it is hard to find suitable ESD material. A further attempt is to classify ESD control areas in different zones.
In addition, the increase of relative humidity by spraying is no solution to reduce electrostatic problems in EPAs. Many processes are also closed and cannot be influenced.
Initially Published in the SMTA Proceedings
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