TechNeters: With encouragement from Ken I am posting my comment I made to him and taking the liberty of posting his since his answers my comments: Dehoyos, Ramon" wrote: > Ken: > I respect your input on how to properly use board carts in specific > the ones you manufacture. My question is, has any one in your company done > any voltage measurements on how much voltage a cart can build up by being > rolled a block on a tile floor? I walked fast pushing one roll cart for about 200 feet and it > did not build one volt of charge measured with a VOM. It may not be the best > way to measure static charge. A better tool may be an oscilloscope. > Experience has shown me that rolling carts on tile floors has negligible > effect on ICs. > Do not mean to argue just communicate my perspective on the matter. > Regards, > Ramon Wearing conductive material jackets does help a lot. Since they do not charge up as some of the artificial materials. Sleeves do contact boards while working and may discharge on components. Hi Ramon Thanks for taking the time to write. First to answer your question, no we have not done the measurement the way you described, we had 3M auditors come in several years ago with the standard testers and field monitors and tell me the carts work great. Let me explain the tray cart based on your comment. Moving the cart may or may not actually generate a static charge, depending on a lot of variables. People around it or other equipment that may have a charge and are creating a "field" around them or it may transfer some of that static field to the cart or the PC boards. You cannot see it of course but it can be measured if you have the right equipment as you mentioned. The only safe way that I can see to ensure there is none ever is to follow my guidelines. Keeping it grounded prior to touching a PC board is key. Just like when you are about to work at a techbench you plug in a wrist strap plug to ground you prior to touching the PC board. You may not feel anything and you may feel a static shock when you first touch ground. It is a huge variable creating static electricity, that is why complete prevention is the only way to stop it safely. I encourage you to post to the IPCnet forum your comment. Ken Bliss " > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 847-509-9700 ext.5315 -----------------------------------------------------