Hi Simon, This might be a stretch, so others, feel free to beat me up... The formula one of our laminate suppliers uses for determining theortical Dk of FR-4 materials is: Dk=6.3*(Tglass/Td)+3.6*((Td-Tglass)/Td), where Tglass = thickness of glass cloth (in mils) Td = overall thickness of dielectric 6.3 = Dk of glass (at 1 Mhz) 3.6 = Dk of FR-4 epoxy resin (at 1 MHz) Assuming you know the Dk and thickness of each of the materials in question, I don't see why you couldn't apply the above formula. Change the 6.3 to the Dk of one of the materials, the 3.6 to the Dk of the other material. Substitute the thickness of the first material for Tglass, and Td is equal to the combined thickness of both materials. Hope this makes sense...Andy ______________________________ Reply Separator _________________________________ Subject: [TN] Dielectric Calculation Author: Simon Butte <[log in to unmask]> at smtplink-hadco Date: 05/05/99 4:04 PM Hi Everybody, Is anyone know how I can figure out the effective dielectric constant when 2 different Dielectric materials are placed together. Is there any document I can find in the web. Any input is appreciated. Simon Butte Email : [log in to unmask] ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################