Authored By:
Dipl. Ing. Hartmut Berndt
B.E.STAT European ESD competence centre
Kesselsdorf, Germany
Summary
The number of failures caused by electrostatic discharges (ESD) has been increasing for some time now. So, it is necessary for everyone, who handles electrostatic sensitive devices (ESDS), to know the reasons of such failures. The paper will give an overview about possible causes for ESD. Particularly automated production lines have some processing steps, where electrostatic charges are increasingly generated. So far one has been focused on the human being.
This is controllable. Measurements in production lines show electrostatic charges at the following processing steps: application of soldering paste (printer), assembling (automated and manual (pick and place), and labeling as well as electric tests (ICT). The electronic components are always assembled directly and without any covering on the PCBs. Thus, the wire bonding process leads to damage of the electronic components.
The processing steps, where the PCBs are covered with chassis must be inspected also. Such chassis are mostly made of isolating materials, like plastics. Thus, those can be highly electrostatic charged, while assembling. In summary an optimized ESD Control System for ESD working areas and machines with the emphasis on cost-effectiveness will be compared. Topics: An optimized ESD control system, with an emphasis on cost-effectiveness, Introduction of an optimized ESD Control System for ESD working areas, Solutions for machines and automated processes, Measurement methods in SMT production line and ESD audits, Product quality.
Conclusions
The statements are intended to highlight the problems in an EPA and the handling of electronic components in the coming years. The components become more and more sensitive to electrostatic charges and fields. However, the current ESD measures are not sufficient, and thus they are not able to protect the ESDS in the coming years.
Many companies have already installed ESD Control Systems and ESD equipment. But this will not suffice, because the plans must be constantly reviewed and adapted to the current ESD requirements. Nevertheless, the ESD equipment on the market will no longer meet the ESD requirements in the coming years. They must be developed. Furthermore, the failure models are constantly changing. So far, the HBM was the most important one, but the CDM also becomes more and more important.
The actual sources of static electricity are another problem. People and work places are well controlled, but the machinery, equipment, etc are the next generation of electrostatic charges. The existing measurement systems are partially sufficient for the verification of persons and work places. But they are no longer sufficient to determine the electrostatic charges and fields in the very fast processes of plants and machinery. The question is, do we still measure static or would a dynamic measurement be better? At what speeds, frequencies, sampling rates, etc., should we measure?
Even conventional measurement technology is no longer sufficient today to measure electrostatic charging and discharging. Sometimes there are new materials that cannot be assessed according to the methods of resistance, such as conductive and dissipative plastic coatings.
Initially Published in the IPC Proceedings
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