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Physics and Modeling of Vias in Printed Circuit Boards
Jan Birger Preibisch & Christian Schuster
Institute of Electromagnetic Theory
Hamburg University of Technology (TUHH)
18th European IBIS Summit Meeting
May 13th, 2015 Berlin, Germay
Jan Preibisch & Christian Schuster – 2
(1) The Problem with Vias
(2) Physics of Vias
(3) Models for Vias
(4) Application Example
(5) Conclusions
Outline
Jan Preibisch & Christian Schuster – 3
(2)
The Problem with Vias
Jan Preibisch & Christian Schuster – 4
The Problem with Vias …
Power Plane Ground Plane
Driver Via
Receiver DC Power Supply
PCB
Jan Preibisch & Christian Schuster – 5
Signal Integrity Problems:
Attenuation, Reflection, Dispersion, Interference, Crosstalk
The Problem with Vias …
Jan Preibisch & Christian Schuster – 6
Power Integrity Problems:
Voltage Drop, Switching Noise, Crosstalk
The Problem with Vias …
Jan Preibisch & Christian Schuster – 7
Electromagnetic Compatibility Problems:
Near Field Coupling, Radiated Emissions
The Problem with Vias …
Jan Preibisch & Christian Schuster – 8
(2)
Physics of Vias
Jan Preibisch & Christian Schuster – 9
Currents on Via Structures
Figures by R. Rimolo-Donadio
Via current Port 1
Conduction
return current
Ground
via
Displacement
return Current
Via (Signal) Current
Conduction Return Current
Displacement Return Current
Jan Preibisch & Christian Schuster – 10
Electric Fields Between Plates
Top View, 5th Cavity
Excitation: Gaussian pulse (fmax = 40 GHz)
Figures by R. Rimolo-Donadio
Jan Preibisch & Christian Schuster – 11
Electric Fields Between Plates
Top View, 5th Cavity
Infinite Planes Finite Planes
Top View, 5th cavity
Figures by R. Rimolo-Donadio
Jan Preibisch & Christian Schuster – 12
Influence of Ground Vias
1 Ground Via:
1 GND via
GND Via
SIG Via
Jan Preibisch & Christian Schuster – 13
Influence of Ground Vias
2 Ground Vias:
Jan Preibisch & Christian Schuster – 14
Influence of Ground Vias
4 Ground Vias:
Jan Preibisch & Christian Schuster – 15
Influence of Ground Vias
6 Ground Vias:
Jan Preibisch & Christian Schuster – 16
Influence of Ground Vias
Frequency [GHz]
Magnitude o
f S
12 [dB
]
1 GND vias
2 GND vias
4 GND vias
6 GND vias
Jan Preibisch & Christian Schuster – 17
Influence of Ground Vias
Effect of location
of ground vias:
4 GND Vias, s=80 mil 4 GND Vias, s=40 mil
4 GND Vias, s=160 mil No GND Vias
GND Via
s
Jan Preibisch & Christian Schuster – 18
Physics of Vias – Summary
Vias „live“ within a parallel plate environment
Shape and size of the plates have an impact
Ground vias can be used to control that impact
Return currents are a mixture of displacement
and conduction currents
!
Jan Preibisch & Christian Schuster – 19
(3)
Models for Vias
Jan Preibisch & Christian Schuster – 20
PCB Teardown
Picture courtesy IBM Yorktown (Y. Kwark)
Power Planes
Stripline
Signal and
Power Vias
Transmission
Line Models
Planar Circuit
Models
Via Models
Jan Preibisch & Christian Schuster – 21
A “Physics-Based” Model for Vias
Via Cross Section
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ipp
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10
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Cp
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Cp
Cp
Zpp
Current
Current
Jan Preibisch & Christian Schuster – 22
A “Physics-Based” Model for Vias
Zpp
~60 fF
~60 fF
C
C
Port 1
Port 2
Port 1
Port 2
PMC
360x360 mil
8mil
r=4.4
tan=0.02
Via centered:
Radius 5mil
Antipad 10mil
Simple example:
Jan Preibisch & Christian Schuster – 23
Planar Circuit Model I
x
y
z
(0,0,0) (a,0,0)
(a,b,0)
(a,b,d)
Port i Port j (xi,yi)
Open
Plane
Edges
Voltage
Current
(xj,yj)
Filling with and m
CRM
m
kb
nk
a
mk
ynxm,,
otherwise 2 and 0,for 1 , nmCCnm
0 0
222
22pp)cos()cos()cos()cos(
)(
m n ynxm
jynjxmiynixm
nmij
kkk
ykxkykxkCC
ab
djZ
m
Jan Preibisch & Christian Schuster – 24
x
y
z
Separation d
Port i Port j (xi,yi)
No
Plane
Edges Voltage
Current
(xj,yj)
Filling with and m
)(
)(
2)(
0
)2(
1
)2(
0
0
pp
m
kH
kHjdZ
ij
ij
m k,dist.port,radiusport00
RWM
Planar Circuit Model II
Jan Preibisch & Christian Schuster – 25
25
x
y
z
Separation d
Port i Port j (xi,yi)
Any
Open
Plane
Edges Voltage
Current
(xj,yj)
Filling with and m
CIM
jikaHkaJ
jikRHkaJkaJ
j
akU
ii
jij
ij)2(
10
)2(
010
jikaHkaJ
jikRHkaJkaJdkH
ii
ji
ij)2(
00
)2(
000
2
HUZ
1pp
Planar Circuit Model III
Jan Preibisch & Christian Schuster – 26
Effect of Multiple Scatterings
Fields “seen by” CRM & RWG Fields “seen by” CIM
X. Duan, R. Rimolo-Donadio, S. Müller, K. Han, X. Gu, Y. Kwark, H.-D. Brüns, C.
Schuster, „Impact of Multiple Scattering on Passivity of Equivalent-Circuit Via
Models“, IEEE Electrical Design of Advanced Package & Systems Symposium
(EDAPS), Hangzhou, China, December 12-14, 2011.
Jan Preibisch & Christian Schuster – 27
Trace between planes:
2 Modes: Stripline + Parallel Plate
Stripline Mode
Parallel Plate Mode (pp)
Including Striplines
Jan Preibisch & Christian Schuster – 28
Complete Model for One Cavity
tlYkk
tlYkk
tlYkk
tlYkk
tlYk0
0tl
Yk
)()(
)()(
)( 22
22
1
vl
vu
Y0
0Y
l
u
I
I
T T
1uv
1ui
2uv
2ui
3uv
3ui
1lv
1li
2lv
2li
3lv
3li
u
uI
V
l
lI
V
pppp
pppp
YY
YY
Ztl Ztl
Zpp Zpp Zpp Zpp
l
u
V
V
vC
vC
vC
vC
vC v
C
R. Rimolo-Donadio, X. Gu, Y. H. Kwark, M. B. Ritter, B. Archambeault, F. D. Paulis, Y.
Zhang, J. Fan, H.-D. Brüns, C. Schuster, “Physics-based via and trace models
for efficient link simulation on multilayer structures up to 40 GHz,” IEEE Trans.
on Microwave Theory and Techniques, vol. 57, no. 8, pp. 2072-2083, August 2009.
Jan Preibisch & Christian Schuster – 29
Complete Model for Full PCB
Cavity
representation S-Parameter
Matrix
Port 1 Port n
Cavities merged
using
segmentation
techniques
Zpp Ztl
Decap
Linterc.
Zpp Ztl
Decap
Linterc.
Decap
Linterc.
Decoupling capacitor model
Cavity
representation
Port 1 Port n
Port k
R. Rimolo-Donadio, X. Gu, Y. H. Kwark, M. B. Ritter, B. Archambeault, F. D. Paulis, Y.
Zhang, J. Fan, H.-D. Brüns, C. Schuster, “Physics-based via and trace models
for efficient link simulation on multilayer structures up to 40 GHz,” IEEE Trans.
on Microwave Theory and Techniques, vol. 57, no. 8, pp. 2072-2083, August 2009.
Jan Preibisch & Christian Schuster – 30
6 Vias, 4 traces case
Centered striplines at two
levels, and thru vias in a 6
cavity stackup
Full-wave model
Comparison with Full-Wave Results
Mag
nit
ud
e of
S12 [
dB
]
Frequency [GHz]
Model
FEM simulation
FIT simulation Full-wave model M
agn
itu
de
of
S14 [
dB
]
Frequency [GHz]
Model
FEM simulation
FIT simulation
Jan Preibisch & Christian Schuster – 31
Comparison with Full-Wave Results
R. Rimolo-Donadio, X. Gu, Y. H. Kwark, M. B. Ritter, B. Archambeault, F. D. Paulis, Y.
Zhang, J. Fan, H.-D. Brüns, C. Schuster, “Physics-based via and trace models
for efficient link simulation on multilayer structures up to 40 GHz,” IEEE Trans.
on Microwave Theory and Techniques, vol. 57, no. 8, pp. 2072-2083, August 2009.
Computation is 2 to 3 orders of magnitude faster in comparison
to general-purpose numerical methods!
3D Model required
Field information available
High level description (text-based)
Network Parameters
Jan Preibisch & Christian Schuster – 32
• 119 vias (76 signal,
43 ground)
• 14 differential
striplines (2D)
• 6 cavities
• Terminations
Comp. time: < 3 min
Assumption
of infinite
plates
Comparison with Measurements
R. Rimolo-Donadio, X. Gu, Y. H. Kwark, M. B. Ritter, B. Archambeault, F. D. Paulis, Y.
Zhang, J. Fan, H.-D. Brüns, C. Schuster, “Physics-based via and trace models
for efficient link simulation on multilayer structures up to 40 GHz,” IEEE Trans.
on Microwave Theory and Techniques, vol. 57, no. 8, pp. 2072-2083, August 2009.
Jan Preibisch & Christian Schuster – 33
Models capture the salient features of the
hardware response despite simplifications
|S13| [dB] - FEXT |S12| [dB] - IL
Link 10 -
S3 Stripline
Link 17 -
S5 Stripline
Link 10 -
S3 Stripline
Link 17 -
S5 Stripline
Measurement Link 10
Measurement Link 17
Model Link 10
Model Link 17
Comparison with Measurements
Jan Preibisch & Christian Schuster – 34
Comparison with Measurements
Horizontal Eye Opening [ps] (10 ps/div)
Vert
ical E
ye O
penin
g [V
]
Model
0.598 V
65.63 ps
tr=10 pS
15 Gbps
Measurement
0.552 V
65.63 ps
Link L5
Simulation of the time domain link performance up to
15 Gbps within 10% accuracy!
Jan Preibisch & Christian Schuster – 35
Models for Vias – Summary
Physics based via models can predict SI, PI,
and EMC issues on PCBs up to tens of GHz
They do this (very) efficiently
They do this (quite) accurately
… but limitations exist with regard to shape,
size, and proximity of vias!
!
Jan Preibisch & Christian Schuster – 36
(4)
Application Example
Jan Preibisch & Christian Schuster – 37
1. Design of Controlled Vias
Calculation of Ground and Displacement Return Currents using CIM
Jan Preibisch & Christian Schuster – 38
1. Design of Controlled Vias
Effect of Number of Ground Vias
Jan Preibisch & Christian Schuster – 39
1. Design of Controlled Vias
Engineering Rules for Design
Jan Preibisch & Christian Schuster – 40
1. Design of Controlled Vias
Application Example
The via shows a typical transmission line behavior (reflection)
The transmission is above -1dB up to 40GHz 13 layers
Jan Preibisch & Christian Schuster – 41
Application Examples – Summary
Physics based via models can be used to
mitigate common SI and PI issues
They are especially useful for pre-layout analysis
Due to their efficiency PCB layout automation
and optimization become „viable“
!
Jan Preibisch & Christian Schuster – 42
For More Information
Published in IEEE Transactions on Components, Packaging,
and Manufacturing Technology, vol. 3, no. 3, March 2013
Jan Preibisch & Christian Schuster – 43
Contact Information
Jan Birger Preibisch,
Prof. Dr. sc. techn. Christian Schuster
Institut für Theoretische Elektrotechnik
Technische Universität Hamburg-Harburg
Harburger Schloss Str. 20
21079 Hamburg, Germany
Tel: +49 40 42878 3116
WWW: http://www.tet.tu-harburg.de/
E-Mail: jan.preibisch@tuhh.de, schuster@tuhh.de
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