February 2015 • The PCB Design Magazine 27
pears smooth but at the microscopic level,
all materials exhibit surface irregularities.
• The onset frequency of the RMS surface
roughness effect is 1.28GHz for ED copper.
• Typical values of surface roughness are
3um for the outer surface and 6um for the
inner surface.
• The smoothest surface HVLP material with
1.5um average surface roughness, will not
exhibit any noticeable surface roughness
effect up to 20GHz.
PCBDESIgn
References
1. Barry Olney Beyond Design columns: Sur-
face Finishes for High-Speed PCBs and Material
Selection for SERDES Design.
2. "How Surface Roughness Impacts High-
Performance PCBs," Judy Warner, Microwave
Journal.
3. "Effect of Conductor Surface Roughness
upon Measured Loss and Extracted Values of
PCB Laminate Material Dissipation Factor," Hi-
naga, Koledintseva, Anmula and Drewniak.
4. "Signal Transmission Loss due to Copper
Surface Roughness in High-Frequency Region,"
Liew, Okubo, and Hosoi.
5. "Roughness Characterization for Inter-
connect Analysis," Yuriy Shlepnev, Chudy Nwa-
chukwu.
6. "Signal and Power Integrity Simplified,"
Eric Bogatin.
7. "High-Speed Signal Propagation," How-
ard Johnson.
8. The ICD Stackup and PDN Planner, www.
icd.com.au
Barry Olney is managing direc-
tor of In-Circuit Design Pty ltd
(ICD), Australia. This PCB design
service bureau specializes in
board-level simulation, and has
developed the ICD stackup Plan-
ner and ICD PDN Planner software. To read
past columns, or to contact Olney, click here.
EFFECTS OF SURFACE ROUgHnESS On HIgH-SPEED PCBS continues
beyond design
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