Analysis of Test Coupon Structures for the Extraction of ... · Analysis of Test Coupon Structures...
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Analysis of Test Coupon Structures for the Extraction
of High Frequency PCB Material Properties
Heidi Barnes
Bob Schaefer
Jose Moreira
‘SPI 20131
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AGENDA
2 ‘SPI 2013
� EM Simulation and PCB Material Properties
� 2-Line Segment ( dK, loss tan, conductivity)
� Resonant Beatty Structure (dK height, trace width)
� Measurement Based Parameter Tuning Results
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Measurement Based Verification of EM Simulation
3 ‘SPI 2013
EM Simulations are
only as accurate as the
PCB specifications
Simple Series Resonant Change in Impedance
Frequency Domain
EM Simulation Fails to Match Measurement
Time Domain
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PCB Conductor and Dielectric Material Properties
4
‘SPI 2013
+
+=Ζ
tw
tb
r8.0
2ln
60
εο
Z0, characteristic impedance (Ohm)
b, the dielectric height between reference planes (mil)
t, copper thickness of the PCB trace (mil)
w, trace width (mil)
, dielectric constant
, is the speed of light in vacuum
, loss tangent
rε
dielconddB ααα +=
fwZ
cond
0
36=α
r
o
diel fc
εδπ
α tan=
oc
δtan
PCB Frequency Dependent Losses
can be separated into Conductor
and Dielectric Losses
Stripline Dielectric Losses only
require 1 line length to determine
dielectric loss and electrical delay.
Stripline Conductor Losses require
more then 1 line width to determine
dielectric height and trace width.
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5 ‘SPI 2013
Typical Method for Measured PCB Material Properties
Two PCB Test Structures with Different Line Lengths
� Excellent for determining T-Line loss and delay characteristics
� Does not provide information on as-built trace width and dK height.
FIXTURE AS-PARAMETERS
FIXTURE BS-PARAMETERS
SYMMETRICAL 2x FIXTURE THROUGH PATH
Splitting of the
S-Parameters
Agilent PLTS AFR Algorithm
Step 1
FIXTURE
DE-EMBED
FIXTURE + ADDITIONAL LINE LENGTHT-LINE LENGTH
MATERIAL PROPERTIES
T-Matrix
Step 2
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6 ‘SPI 2013
Additional PCB Resonant Beatty Structure
Beatty Style Series Resonant Change in Impedance Test Structure
� Enables estimation of as-fabricated dK height and trace width.
� Only requires one additional test structure on the PCB.
� Simple layout construction.
T-Line Change in ZFabrication Properties
FIXTURE
DE-EMBED
T-Matrix
Step 3FIXTURE + Resonant Beatty Structure
FIXTURE
DE-EMBED
Step 3
S-Parameters before Fixture De-Embed Measured S-Parametersafter Fixture De-Embed
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7 ‘SPI 2013
VarEqn VAR
VAR6
t=0.6
TanD=0.0058328 {t}
W=9.4 {t}
sigma=42936000 {t}
W_tol=-1.1 {t}
b=7.9 {t}
Er=3.22 {t}
Dielectric Constant
Loss Tangent
Dielectric Height
Trace Width
Etching Tolerance
Trace thickness
Copper Trace Conductivity
As-Fabricated
Material Properties
Tune Model Variables
to Match Measurement
Enables Estimate of Trace Width and DK Height
Series Resonant Beatty Structure
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8 ‘SPI 2013
2-Step Process: Fast Tuning with 2D-Planar Model then Fine Tune with EM Simulator
Fast Tune 2D-Planar Model Parameters to Match Measured Data
* Simple T-Line model with out the complexity of fixture connections
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9 ‘SPI 2013
Matching Measured Data – Time and Frequency
Transmission Line Through Segment Series Resonant Beatty Structure
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10 ‘SPI 2013
Final 3D EM Model vs. Measurement
Frequency Domain
Fine Tune EM Model Parameters to Match Measured Data
• Dielectric Constant
• Dielectric Height
• Trace Width
• Etching Tolerance
• Loss Tangent
• Copper Trace Conductivity
Parameters for Tuning
Time Domain
3D EM Model
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11 ‘SPI 2013
Comment on Measured Data Accuracy
Measurement Accuracy
Quality of the Fixture
Measured vs 3D-EM Simulated
Requires Symmetry
Measure
Model
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Conclusion
12 ‘SPI 2013
� Matching Measurement with Simulation needs PCB Test Structures
� Transmission line losses only require 2 test coupon structures
� The addition of a series resonant structure enables estimates of as
fabricated dimensions for accurate EM simulations
� PCB test structures validate both PCB fabrication requirements as well as
simulation set-ups.