I hope that someone on the forum may have a comment or two about this subject... and can help John. - Bill -----Original Message----- From: John Smith [mailto:[log in to unmask]] Sent: Thursday, May 05, 2005 7:21 AM To: 'Bill Brooks' Subject: RE: Web site question Thank you for your response Bill, I am trying find out at what voltage and at what distance I need to be concerned about a static discharge from a plastic surface. I have a silicon wafer processing tool and there is concern about static discharge from the exterior plastic panels. I want to be able to determine, the voltage vs.. distance safe point, i.e. (at 500v of charge an arc will not jump at a greater distance than .5") I understand that the type of material, the humidity and other factors make a difference, but there must be some test data some where that points to some generalities. Thanks again for your time bill John -----Original Message----- From: Bill Brooks [mailto:[log in to unmask]] Sent: Wednesday, May 04, 2005 11:03 PM To: 'John Smith' Subject: RE: Web site question http://sprott.physics.wisc.edu/demobook/chapter4.htm see table 4.2 The issue with predicting electrical arcing is in defining the environmental conditions that contribute to the 'break over' voltage. The presence of dry ionizing air, or ionic contamination on a surface can greatly increase the distance at which break over will occur. Once the arc is established, it ionizes an electrical path which is much lower in resistance that the initial break over voltage required to jump across the electrodes and the two points of potential can be moved much farther apart and they will still conduct... What are you trying to do? Bill Brooks -----Original Message----- From: John Smith [mailto:[log in to unmask]] Sent: Wednesday, May 04, 2005 2:09 PM To: [log in to unmask] Subject: Web site question Is there a guideline that references how far a static charge will jump? i.e. a 500v charge could be expected to jump or ark how far? --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ---------------------------------------------------------------------------------