Given normal circuit geometry and construction, 5 ohms is getting close to the upper limit for a hard short in a board. I believe a 5 mil wide trace on 0.5 oz copper will have a resistivity of about 0.6 ohms/inch at room temperature. Resistive heating will cause some increase but can't account for 10Mohms by itself. The only way to get a resistance that high is through contact resistance. I suspect that you've got some metallic contamination in between the two nets. Resistive heating results in thermal expansion and drives up the contact resistance. Happy hunting! > ---------- > From: Robert McGarry[SMTP:[log in to unmask]] > Reply To: [log in to unmask] > Sent: Tuesday, April 06, 1999 10:07 AM > To: Mcmaster, Michael > Subject: RE: [TN] test-phenom > > > What are the resistive values initially and after stabilizing). > > > > Initially around 5 ohms the after about 7 seconds it will stabalize > around 10 Megohms > > > > > ---------- > > > From: Robert McGarry[SMTP:[log in to unmask]] > > > Reply To: [log in to unmask] > > > Sent: Tuesday, April 06, 1999 9:39 AM > > > To: [log in to unmask] > > > Subject: [TN] test-phenom > > > > > > Hello Tech-Net, > > > I'm working with a bare PCB which is a 10 layer board and has > > > various signal and plane layers internally and solder mask and > > > trace layers externally. I'm experiencing a strange phenomena > > > during electrical test. The initial test fails as a short but when > I > > > put > > > an ohm-meter to the points, the resistance slowly increases then > > > becomes stable as if it were a capacitor charging up. when I > > > reverse the leads it discharges and then slowly increases > > > resistance. > > > Has anyone ever seen this occur or possibly have an explanation > > > or idea as to what might be happening. > > > Thanks, > > > > > > Robert P. McGarry jr > > > Technical Sales Analyst > > > Proto Circuit Inc. > > > 7 Ascot Pkwy. > > > Cuyahoga Falls, OH. 44223 > > > 330-572-3400 fx. 330-572-3434 > > > [log in to unmask] > > > http://www.protocircuit.com > > > > > > "QUALITY MANUFACTURED PRINTED CIRCUIT BOARDS" > > > > > > ################################################################ > > > TechNet 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 TechNet <your full name> > > > To unsubscribe: SIGNOFF TechNet > > > ################################################################ > > > 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 > > > ################################################################ > > > > > > Robert P. McGarry jr > Technical Sales Analyst > Proto Circuit Inc. > 7 Ascot Pkwy. > Cuyahoga Falls, OH. 44223 > 330-572-3400 fx. 330-572-3434 > [log in to unmask] > http://www.protocircuit.com > > "QUALITY MANUFACTURED PRINTED CIRCUIT BOARDS" > ################################################################ TechNet 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 TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ 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 ################################################################