Desco - Questions And Answers

Do you have any information / suggestions for some process equipment (silk screen type device) that builds up a significant charge (the part) when processing. In this case, I do not need to protect the part, I need to proctect the assembler from a static discharge, vissible and 2-3 inches long. We have tried wrist straps, ionizers over the parts (2-4 second dwell time!) etc, but this does not seem to work. In this case is it better to try and ground the part (which is porcelean coated)? -Jim, Whirlpool Corp., Clyde Ohio

In this case, grounding the person may be making matters worse (increasing the potential difference between the process equipment and the operator). Ionization is probably the most useful tool for removing charge, but the area that is charging must be identified and the ionization directed to that area to help minimize charge build up and consequential ESD. If possible, grounding the process equipment may help, but it appears several isolated insulators are part of the system and will need ionization directed onto these exposed surfaces. Make sure that the power going to the equipment is properly wired/grounded via the power input. Other solutions would be to treat the exposed insulative surfaces with a topical antistat (if not detrimental to the process), increase the RH to no more the 70% (if corrosion is not a big concern) and make sure that the setup is not creating a huge capacitor (capacitive coupling) via the worktable/stand and processing equipment.

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