February 11, 2015
Microscopes are a common instrument found in electronic assembly operations. Microscopes are used for inspection and for assembly of very small objects. It is critical that the microscope lenses remain clear and free of dust and other contamination. When not in use, microscopes should be covered to protect the optics.
Some manufactures of microscopes provide covers for the time when the scopes are not in use. Typically the covers are made of vinyl. While vinyl may provide good protection from dust and fumes, it is a significant static generator.
The vinyl cover in the photo above shows an electrostatic voltage of -5,500 volts. Once the cover is removed from the scope the voltage jumps even higher to -12,000 volts.
ANSI/ESD S2020, the industry standard for ESD control programs, states that all nonessential insulators should be removed from the ESD protected area.
Since it is critical that microscopes be covered when not in use, it could be argued that the microscope cover is a process essential insulator. ANSI/ESD S2020, Section 8.3.1 states that the ESD control program “shall include a plan for handling process required insulators in order to mitigate field induced CDM damage.”
The standard goes on to say that if the field is greater than 2000 volts/inch it must be kept more than 12” from the ESD sensitive item. If the microscope is not in use, but work on ESD sensitive devices is being performed at the station, the vinyl scope cover becomes a significant risk. The vinyl cover becomes even a greater risk if it is removed while there are ESD sensitive items at the workstation.
The best solution is to replace the vinyl cover with a microscope cover that is ESD safe, such as the Transforming Technologies MC1221W. This scope cover is constructed of ESD safe material and does not generate a significant charge.
Even when the cover is removed, the charge remains very low.
With Transforming Technologies’ MC1221W you can protect your microscope optics from contamination while keeping your work station ESD safe.