Back when I was working for a telco company, I wrote a paper that mathematically analyzed FR-4 to an ideal upper limit of about 850 MHz, IIRC. We were using FR-4 to an upper channel freq of 860 MHz for analog and an upper of 1 GHz for ECL based digital. Now this is no absolute. I met some designers that wouldn't take FR-4 above about 300 or 400 MHz, but that was their situation. Our situation with the boards for the analog 850 stuff had it's downside. There could be a variance of anywhere from 1 to 2 dB of signal on the same board. This all depended greatly upon the mfr'ing processes used and that in turn all depended upon what exactly the board houses were told by the customer in making the boards. I'll stick my neck out and say as with anything, if the proper information is given and someone is willing to pay any amount of money for quality checks, you could take FR-4 as high as you want. Regards, Doug Manfred Huschka wrote: > > Fred, > > although I am working for a PTFE/woven glass fabric manufacturer, I can tell you that based on many years of > experience in manufacturing FR4, BT/Epoxy, Polyimide, PTFE, etc. base materials, 400 MHz is still a good > frequency for FR4 - depending on tolerances. > > Some design engineers use FR4 up to more than 1 GHz, whereas other ones use PTFE/woven glass laminates from > even as low as 200 MHz on. > > Regards > > Manfred Huschka > Taconic > > --- On Thu, 21 May 1998 08:25:09 -0700 Fred Watt <[log in to unmask]> wrote: > 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 ################################################################