Printed Circuit Design & Fab - January 2009 - (Page 21)

LAMINATE MatErialS and, Eq 2 α conductor = 36 • √(ƒ) / Zo • w (dB/ in) where, α conductor is the conductor loss ƒ is the frequency (GHz) Zo is the impedance (Ω) w is the trace width (mil) These approximations have been demonstrated to be accurate enough to make informed decisions regarding material performance. These two equations will be used below to help demonstrate the influence of the variables mentioned previously. FiGurE 2. the effects of temperature on Dk at a 50% resin content. FiGurE 3. the effects of temperature on Df at a 50% resin content. Basis for Comparison In order to understand the influence of material and test variations on electrical performance, one can use the following equations to approximate the dielectric and conductor losses that will be used as the foundation for comparisons in this article. It is important to include the conductor losses as part of the comparison, because that portion of the loss can account for a substantial portion of the overall loss. The calculation for conductor loss does not include the effects of surface roughness of the conductor and should not be ignored. Conductor loss as a result of surface roughness is outside the scope of this article. The following first-order approximations can be used to show the difference in attenuation.8 α material = α dielectric + α conductor Eq 1 α dielectric = 2.3 •ƒ • Df • √Dk (dB/in) where, α dielectric is the dielectric loss ƒ is the frequency (GHz) Df is the material loss tangent Dk is the material relative permittivity Effects of Resin Content Differences in resin content percentages have a significant effect on the Dk and Df values. The resin content percentage varies based on the glass style, the target thickness for a given glass style and the manufacturing tolerances. FiGurE 1 demonstrates these differences between resins contents of 40% to 75% at three nominal frequencies at room temperature. Typical resin content percentages for laminate and prepreg product lines range from approximately 40% to 50% on thick cores with heavy glass cloth JANUARY 2009 PRINTED CIRCUIT DESIGN & FAB 21 http://www.taiyo-america.com http://www.taiyo-america.com/specials.asp http://www.taiyo-america.com

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - January 2009

Printed Circuit Design & Fab - January 2009 Contents Our Line Market Watch Around the World Happenings ROI The Signal Doctor Positive Plating Final Finish Forum Making Sense of Laminate Dielectric Properties Design and Fab Tips for Improving Solder Mask Registration Automating the DDRx Interface Verification Process Printed Circuit Design & Fab Annual Buyers Guide: Special Suppliers Section Printed Circuit Design & Fab Annual Buyers Guide: Guide to Products and Services Off the Shelf Marketplace Ad Index BGA Bulletin

Printed Circuit Design & Fab - January 2009

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