PHIL In a past life did high voltage design. The tracking usually follows the weave of the material as you said. We used a material that was a blown glass in plastic this produced a random weave the material was called Milacron. Don't know the cost. I posted the information for this material awhile back. I don't even know if the material is made anymore. Thankyou Joe Keary -----Original Message----- From: Phil Nutting [mailto:[log in to unmask]] Sent: Wednesday, May 15, 2002 2:03 PM To: [log in to unmask] Subject: [TN] High Voltage tracking on pbc surface Hi folks, Today I have a question about high voltage tracking. The actual set of materials and applications are as follows. FR4 material, 0.090" thick, two layer, plated through hole, LPI solder mask, submerged in Shell Diala AX dielectric oil, operating at 100kV. We are seeing hv tracking marks that run with the grain (fiber directions) of the FR4 material. This burn marking is in the LPI, but also in the FR4 material as can be seen in the photo where the LPI has been scrapped off. The measling is from removing the copper from the board. Here is the photo http://www.stevezeva.homestead.com/files/HVTracking.jpg. It is the top left hand photo entitled High Voltage Tracking. Thanks, Steve Gregory for posting this on your page www.stevezeva.homstead.com. We have seen this tracking on other boards which do not have the LPI solder mask, they are bare boards, so that eliminates the LPI as the cause. One of our engineers had seen this in a former life and it was attributed to the small air bubbles in the substrate where the fibers were. Is there a different type of material that will not exhibit this tracking? Thanks, Phil Nutting ---------------------------------------------------------------------------- ----- Technet 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 Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet 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 Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------