you may want pay Calce for details. "Hollow Fibers and Conductive Filament Formation Increases in failures due to internal board shorting by conductive filament formation (CFF) have driven glass and laminate manufacturers to consider screens and qualification tests to assess the hollow fiber concentration of circuit cards. Laminates composed of hollow fibers pose a threat to the reliability of electronic systems in that they provide a convenient open path for CFF. CFF, also referred to as metallic electromigration, is an electrochemical process. This process requires, as do all other migration phenomena, the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. CFF is difficult to detect in the field because once it occurs, sufficient heat is generated to "vaporize" the conductive filament and "clear" the failure. Furthermore, observation of a partial filament requires destructive analysis. The most apparent solution for the elimination of hollow fibers is to improve manufacturing processes and controls. Multi-layer organic laminates, which make up over 90 percent of the present types of interconnecting substrates in today's electronics (standard FR-4 represents 85 percent of resin systems), can develop a loss of insulation resistance between two biased conductors due to the CFF phenomenon. The opportunity for failure due to CFF is a function of temperature, moisture content, the voltage bias, and manufacturing conditions. E-SEM Image of a Hollow Fiber Based on CALCE EPSC's recommendations, hollow fiber assessment has now become a standard screen by some board fabricators and contract assemblers to qualify suppliers and discard lots with hollow fiber concentrations above specifications. The CALCE EPSC specification being used by laminate manufacturers for this screen is no more than one hollow fiber per 10 cm x 10 cm. This guideline specification reduces the CFF opportunity to less than 1 percent, based on calculations done at CALCE EPSC. As a result of CALCE EPSC's efforts, Nan Ya Plastics, one of the world's largest glass fiber manufacturers, revised their glass production process and experienced a sharp drop in hollow fiber concentration. For more information on hollow fibers and conductive filament formation, contact Dr. Craig Hillman or Keith Rogers at 301-405-5316. " -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Donald Vischulis Sent: Tuesday, February 01, 2005 5:48 PM To: [log in to unmask] Subject: [TN] FAB Question One of our engineers approached me about the use of hollow glass fibres in FR-4. I've never heard of this concept before. Can anybody educate me? This is supposedly a new development from Asia. Don Vischulis --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 -----------------------------------------------------