For what it's worth, Nelco has nice tables of dielectric constant at 1MHz, 1GHz, 2.5GHz and 10GHz for several laminated thicknesses along with the constructions (e.g. 2 layers of 2116). Reference the tables at http://www.parknelco.com/parknelco/resources.htm and take the link for "Typical Dielectric Property Tables". You will need to register for a password first. Isola has some similar information for their FR406 and FR408 products at http://www.isolalaminatesystems.com/isolaus.nsf/main?OpenFrameset . See the spreadsheets under Processing Guide for the respective laminates. jf ------------------------------------------------------------------------ Jonathan Fasig Email: fasig.jonathan@xxxxxxxx Mayo Foundation 4001 41st Street NW MSC Sn 2-132 Phone: (507) 538-5464 Rochester, MN 55901 Fax: (507) 284-9171 -----Original Message----- From: David Hoover [mailto:dhoovy@xxxxxxxxxxxxx] Sent: Tuesday, November 25, 2003 10:46 PM To: alexh1@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Dielectric constant for FR4 at above 1Ghz frequency Alex, (it's been awhile) (below is my $.02 from a fabricator) In the case of FR-4 we typically see a series of variables that gives us the PCB dielectric properties. For example: If we look at the 5 most common (E-Glass) fiberglass styles used in the U.S.: 1060, 1080, 2113, 2116, and 7628 These yield different thicknesses within the PCB. The 1060 yields the thinnest all the way up to the 7628 which is (one of ) the thickest. The Dk of the pure resin of FR-4 epoxy is ~3.6 and the pure (E-glass) fiberglass is ~6.6 (@ 1 MHz . That's all I've found on the raw materials so far). It's the resin to glass ratio that gives us the variance. We typically find: Prepreg Thickness Resin Er Style Percentage (@ 1 GHz) 1060 ~.002" 69 3.63 1080 ~.003" 62 3.80 2113 ~.004" 55 4.00 2116 ~.005" 52 4.08 7628 ~.007" 45 4.32 Those values above are used to manufacture the various FR-4 cores. Each is basically like a building block used to achieve various thicknesses. The thinner ones typically cost more than the thicker ones. Some PCB fab shops or OEMs have rules where they require the use of two plys minimum. A key note to bring up is that even though the 1060 has the lowest Er, it would not be a good idea to build an entire PCB out of that prepreg. The resin content is too high and the pressed PCB would flow resin all over the edges of the lamination templates onto the lamination press. The thinner material(s) also has the greatest amount of dimensional movement within the PCB. An entire PCB built of 1060 would cost alot and would experience large amounts of material shrinkage when pressed. For cost and dimensional movement reasons we minimize the amount of plies by choosing those different styles of prepreg to build the various dielectric thickness. (This allows the pad to hole ratio used today to be maintained) There is beginning to be a few more choices of fiberglass styles. Nelco has introduced the "SI" style fiberglass which has a Dk of 4.4. When used to make prepreg, it yields a substantially lower Er product. If you factor in lower Dk resin blends (like the "-13") you can achieve a fairly low Er material (when compared to standard FR-4). Hitachi and a few others have blends coming on line that have fairly low Er values. These are all thermoset materials. (Meaning they cure into a hard rigid state) The thermoplastic materials (like PTFE based) have Er's that get very low but sometimes are very difficult to build multilayer PCBs with. We should start seeing more and more folks starting to test their materials at various frequencies soon. This is driven by issues such what Stuart, Andy, and Tom are discussing. As far as manipulating resins properties to achieve less loss, I havn't encountered that yet. I have heard of R and D efforts by the laminate manufacturers working on this, but I have not heard of any production ready releases. Kind Regards, David Hoover Sr. Field Application Engineer Multilayer Technology, Inc. San Jose, Ca http://www.multek.com ----- Original Message ----- From: "Alex Horvath" <alexh1@xxxxxxxxxxxxx> To: <si-list@xxxxxxxxxxxxx> Sent: Monday, November 24, 2003 3:04 PM Subject: [SI-LIST] Re: Dielectric constant for FR4 at above 1Ghz frequency > Exactly, it seems to be fairly common misconception that skin effect losses always dominate. Dielectric losses are proportional to frequency, although they start out lower they will always exceed skin effect losses between 500 and 1Ghz or so. The biggest factor affecting this seems to the resin content of the PCB. > > I'd like to hear more about the properties of the resin, if it can be manipulated for less loss and what are the tradeoffs. I wasn't able to find out much about resin properties on the web. > > Thanks > steve weir <weirsp@xxxxxxxxxx> wrote: > Stuart, for common dielectrics, somewhere in the high hundreds of MHz > dielectric loss overtakes loss from skin effect. > > Steve. > At 05:16 PM 11/24/2003 -0500, Stuart Brorson wrote: > >True enough, but aren't the dielectric losses in FR-4 more or less > >frequency independent (i.e. to the <10% level that the dielectric > >function is constant)? > > > >Anyway, Tom is right: you need to consider the frequency variation of > >both Dk (the dielectric function) and Df (the dielectric loss > >function). However, both are typically dominated by skin effect > >losses, particular in the GHz range. > > > >Stuart > > > > > > > To make the answer complete you need also to include dielectric > > > losses > > which > > > also are frequency dependent. > > > > > > Tom Dagostino > > > Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC 2926 > > > SE Yamhill St. Device Modeling Division Portland, OR 97214 13610 > > > SW Harness Lane Beaverton, OR 97008 > > > http://www.teraspeed.com 503-430-1065 > > > tom@xxxxxxxxxxxxx > > > > > > > > > -----Original Message----- > > > From: si-list-bounce@xxxxxxxxxxxxx > > > [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Stuart Brorson > > > Sent: Monday, November 24, 2003 1:22 PM > > > To: andyk@xxxxxxxxxx > > > Cc: si-list@xxxxxxxxxxxxx > > > Subject: [SI-LIST] Re: Dielectric constant for FR4 at above 1Ghz > > > frequency > > > > > > > > > If I am not mistaken, your question is equivalent to this one: Is > > > the dielectric function constant over the 1 MHz -- 1 GHz range? > > > The answer is: It is not constant, but varies by several percent > > > or more over that range for many FR-4s. (FR-4 is not a single > > > material, but is a family of materials, each different depending > > > upon your PCB vendor, and whatever batch of materials he was > > > shipped on any particular day.) > > > > > > However, the bigger problem for you to think about is the loss due > > > to the skin effect in your copper traces. The skin effect losses > > > vary as the square root of the frequency, IIRC. The > > > frequency-dependent loss due to the skin effect dominates over the > > > frequency variation of the FR-4's dielectric constant. > > > > > > Here are some references: > > > > > > http://www.tdasystems.com/library/appnotes/siml0803.pdf > > > http://signalintegrity.com/Pubs%5Cnews%5C4_5.htm > > > > > > Stuart > > > > > > > > > > Hi all, > > > > > > > > I am designing a high speed PCB at over 1Ghz frequency using FR4 > > material= > > > > . > > > > I am wondering how much the dielectric constant will be affected > > > > by the > > > > frequency over 1Ghz as compared to 1Mhz? > > > > > > > > Thank you > > > > > > > > Regards, > > > > Andy > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to: > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List technical documents are available at: http://www.si-list.org > > > >List archives are viewable at: > >//www.freelists.org/archives/si-list > >or at our remote archives: > >http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > >http://www.qsl.net/wb6tpu > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List technical documents are available at: http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu