It sounds like you have possibly not gotten enough clearance around the mounting holes on the Internal Layers. You should be able to visually verify if any exposed internal layer copper is present in the mounting holes. Are the screws that are being used metal or nylon? If metal try using nylon. Does the short go away when you remove the screw? Is there any significant Bow or Twist when the board is installed in the housing? Try installing the bare board in the housing and see if the same signals short out. These are a couple of suggestions to find the problem. Paul Brionez Sr. PCB Designer Cherry Electrical Products 11200 88th Ave Pleasant Prairie, WI 53158 PH 414-942-6659 Fax 414-942-6334 [log in to unmask] > -----Original Message----- > From: Bock Ming Gai Joanne [SMTP:[log in to unmask]] > Sent: Tuesday, September 01, 1998 2:17 AM > To: [log in to unmask] > Subject: [DC] Short Circuit > > Hi all, > > Currently I'm facing a problem at work. I have a few 6 layers of PCBs > that are perfectly alright, meaning that they passed the ET. However, > when our engineers did some testing after board assembly, problem > surface. When they tighten the board with mounting screws, they found > that one of the supply trace was shorted to the Gnd. This was not shown > during the ET because PCB suppliers only did the test on the bare > boards. So now I am looking into what could possibly cause them to short > together. > > I appreciate anyone who can help to provide me with a solution. > > Thanks & Best Regards! > Joanne Bock > > ################################################################ > DesignerCouncil E-Mail Forum provided as a free service by IPC using > LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE DesignerCouncil <your full name> > To unsubscribe: SIGNOFF DesignerCouncil > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ ################################################################ DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################