Hi Fred, I'm finding that many fab houses have settled into modified glass/epoxy systems for a lot of the Hi Speed applications. I would suggest running your design on a couple of different types. Mitch suggested the G-Tek, which does well, but I would also consider Nelco's material (N-6000?- Sorry all, if I got the wrong number). Also check cleanliness levels. JOHN WAITE Mitch Morey wrote: > Fred, > > I've personally done boards beyond 1Ghz with standard high Tg FR4 > material. The high Tg (>140) was for Z-axis stability. The board was > exclusively 50 ohms impedance, and included a test coupon on the board > itself. One thing we did was ask for impedance testing to be done to > 200db levels instead of the standard 20db. This would show any and all > discontinuities along the traces. > > My recommendation is to talk with your fab shop and determine what > exactly they can do for you (technical input), and find out if they can > fabricate using GETEK material (much like FR4, should be no additional > costs) which has a lower and much more stable dielectric constant. My > fab shops was dieing to give me GETEK boards, but this particular > engineer wasn't familiar with it, and couldn't evaluate it properly. > > But then again, he did get boards at 1.2Ghz using standard FR4 material. > Go figure? > > Good luck, > Mitch Morey > Sr PCB Designer > NSI Communications > San Diego CA 92121 > (619)657-5338 > [log in to unmask] > > >>> Fred Watt <[log in to unmask]> 05/21/98 07:25am >>> > Has anybody had any problems with FR-4 at 100 to 200 MHz? I > have several boards from several fabrication shops in which the signal > loses amplitude above 80-100 MHz. The boards are controlled > impedance (50 Ohms) with 5 mil traces and 5 mil dielectrics. The traces > are about 6.5" long. > I would appreciate any comments on this subject. The supplier of > the material says that FR-4 should be good to 400 MHz. > > ################################################################ > 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 web site (http://jefry.ipc.org/forum.htm) for additional > information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ > > ################################################################ > 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 web site (http://jefry.ipc.org/forum.htm) for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 > ################################################################ ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################