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© 2011 ANSYS, Inc. June 18, 2012 1
ANSYS for Tablet Computer Design
Steven G. Pytel, PhD.
Signal Integrity Product Manager
Confidence by Design
Chicago, IL June 14, 2012
© 2011 ANSYS, Inc. June 18, 2012 2
Tablets are very entertaining, stylish and powerful
• Shopping, reading, emailing, accessing social network, playing games
• Schools, operating rooms, sports events
Tablets in our daily lives
Pictures source: www.istockphoto.com
© 2011 ANSYS, Inc. June 18, 2012 3
Problem Predict the performance of a tablet design while meeting strict electrical standards and design specifications
Solution Automated modeling and optimized analysis using ANSYS Electromagnetics tools allows for system simulation approach
Result Detailed and accurate system simulation approach enables tablets to be put on market on time with reduced testing costs
ANSYS for Tablet Designs
Pictures source: www.istockphoto.com
© 2011 ANSYS, Inc. June 18, 2012 4
3D CAD
Layout
Virtual Prototype
Vendor Specific Driver/Receiver Models
Vendor Specific VRM Models
Electronics
Virtual Compliance
Virtual System
Electromagnetic Extraction
Mechanical and Thermal
Virtual System Prototyping
© 2011 ANSYS, Inc. June 18, 2012 5
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 6
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 7
No moving parts present
• Use a thin layer of ITO (indium tin oxide) to sense the presence of a finger by capacitive coupling.
• Capacitive sensors are mounted underneath of hardened glass
• Finger adds a measurable capacitive change in the touch sensor
• Change in sensor capacitance relies on RC time constant change
Capacitive Touchscreen
© 2011 ANSYS, Inc. June 18, 2012 8
Model size, complexity and ….
• Simulate “projected” and/or “mutual-capacitance”
• Include Skin and Proximity Effects
• Build detailed 3D model
Touchscreen Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 9
Parameterized Example 10x10 electrodes model
Capacitive Touchscreen
© 2011 ANSYS, Inc. June 18, 2012 10
Adaptive Mesh Refinement
• Automatically tunes the mesh to the electrical performance of the device. This ensures simulations are correct the first time.
Mesh Convergence
• Real-Time update of performance per adaptive solution
Automatic and Robust Adaptive Meshing
Initial Mesh
Refined Mesh
© 2011 ANSYS, Inc. June 18, 2012 13
Focus on
• Area of contact
• Glass thickness
Finger Tip Effect
© 2011 ANSYS, Inc. June 18, 2012 14
Receiver Signal
Electrode scanning change at contacted ITO (Indium Tin Oxide) position
Non-contact
Proximity Effects (0.1mmGap)
Contact!
© 2011 ANSYS, Inc. June 18, 2012 15
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 16
• Perform Drop test of Tablet PC from height of 4 feet onto a concrete floor at an angle of 45 degree using ANSYS Explicit Dynamics
• The geometry of the Table PC was created from scratch using ANSYS DesignModeler
• The parts are simplified representations of parts in an actual Tablet PC.
Tablet Computer Case
© 2011 ANSYS, Inc. June 18, 2012 17
• The geometry of the Tablet PC was created from scratch using ANSYS DesignModeler
Tablet Case Project Schematic
© 2011 ANSYS, Inc. June 18, 2012 18
• Meshing: – ANSYS Workbench meshing with Explicit
Dynamics preference is used to create a mesh. – Hex dominant mesh is created to reduce the
number of elements – Total number of elements ~25,000
• Analysis settings: – Analysis is solved for 4 e-4 seconds. – Initial velocity of 4.9 m/sec is assigned to the
Tablet – The concrete floor is modeled as a rigid shell
body with fixed constraints – Automatic contact definition is use between
all parts. – Parts that are in contact but may separate due
to the drop test are assigned bonded contacts. – Bonded contacts are modeled as breakable
based on stress criteria for debonding.
Drop test
© 2011 ANSYS, Inc. June 18, 2012 19
Equivalent Stress Contours Back Cover Off
Equivalent Stress Contours Front
Drop Test Simulation Results
© 2011 ANSYS, Inc. June 18, 2012 21
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 22
CPU and Memory Applications
• Flip-chip BGA
• NAND Flash (BGA, FD-BGA SiP, PoP etc.)
Electrical and Thermal simulations
Tablet packages
Courtesy of EEMS
Courtesy of Amkor
© 2011 ANSYS, Inc. June 18, 2012 23
Design Challenges
• Accurate SYZ and RLGC solution
• Dealing with multiple vendors
Solution
• Automated merging capabilities
• Full-wave and Quasi-static solution
Tablet packages
Courtesy of EEMS
© 2011 ANSYS, Inc. June 18, 2012 24
Inside of Cadence SiP and APD and Allegro
• Setup of the HFSS ready to solve project in the Cadence environment
• Signal and pwr/gnd net selection
• Auto port creation on solderballs and bumps/bondwires
• Plane Extent and HFSS Solution Setup Options
HFSS in Cadence
HFSS Solution in progress
© 2011 ANSYS, Inc. June 18, 2012 25
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 26
Parameterized Transmission line model
• Accurate Zo analysis
• Trace spacing and offsets
• Solid vs. patterned ground
FLEX circuit analysis
HFSS Transient
© 2011 ANSYS, Inc. June 18, 2012 27
Interconnect Transmission line model
• Trace Thickness and Width
• Trace to Ground Space
• Ground Shape (Solid vs. Meshed) – Reduce the Interference with High Speed signal Traces or noisy LCD surface
FLEX circuit analysis
© 2011 ANSYS, Inc. June 18, 2012 28
Flex Optimization analysis
• Impact of multiple variables on overall designs
• Goal driven optimization
Design of Experiments
Parametric HFSS Design
WB DX Setup
Response Surface - TDR
© 2011 ANSYS, Inc. June 18, 2012 29
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 30
Antenna Design Challenges
• Location, Beam Forming
• Antenna type
• Human Body Effect – Hand, Body
• Operation Environments – Metal Desk
– Wooden Desk
Tablet Antenna
© 2011 ANSYS, Inc. June 18, 2012 31
Antenna Design Challenges
• Location, Beam Forming
• Human Body Effect – Hand holding tablet at different locations
– Close to antenna and away from antenna
Tablet Antenna
Radiation Efficiency @2.4Ghz :0.967907 Radiation Efficiency @2.4Ghz : 0.480466
© 2011 ANSYS, Inc. June 18, 2012 32
Antenna Design Challenges
• Operation Environments – Human Tissue
– Metal Desk
– Wooden Desk
Tablet Antenna
Human Tissue Metal Desk
Wooden Desk
Radiation Efficiency @2.4Ghz : 0.994337
Radiation Efficiency @2.4Ghz : 0.993303
Radiation Efficiency @2.4Ghz : 0.777207
© 2011 ANSYS, Inc. June 18, 2012 33
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 34
Circuit and Numerical Modeling of ESD Coupling to Shielded Cables HFSS Transient solver for numerical Modeling ESD approach
0.00 5.00 10.00 15.00 20.00 25.00 30.00Time [ns]
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
V(V
olt
ag
e1)
[kV
]
HFSSDesign1Input Voltage ANSOFT
Curve InfoV(Voltage1)
Setup1 : Transient
ESD Analysis
Courtesy of: HUWIN
© 2011 ANSYS, Inc. June 18, 2012 35
ESD Gun Simulation Results
: 6kV
: 5kV
: 4kV
: 2kV
Applied Voltage (kV)
Peak Current (A) IEC 61000-4-2 (ESD Test)
Peak Current (A) Simulation Results
2 7.5 7.75
4 15 15.5
5 18.75 19.3
6 22.5 23.25
Courtesy of: HUWIN
© 2011 ANSYS, Inc. June 18, 2012 36
ESD Gun Simulation Time length: 0 ns ~ 118 ns
ESD Gun and Metal Plate
ESD Animation
Courtesy of: HUWIN
© 2011 ANSYS, Inc. June 18, 2012 37
ESD gun applied on 1 driver and 1 receiver full length electrode
ESD Gun on Tablets touch electrodes
© 2011 ANSYS, Inc. June 18, 2012 38
ESD Gun Simulation Time length: 0 ns ~ 118 ns
ESD Gun effect on Tablets touch electrodes
© 2011 ANSYS, Inc. June 18, 2012 40
Designing the impossible
• Touchscreen
• Tablet Case
• Packages
• Flex circuitry
• Antenna
• ESD
• EMI
Tablets Design Challenges
© 2011 ANSYS, Inc. June 18, 2012 41
EMI Design Challenges
• Entire PCB + Case
• Driver & Receiver
• Near field, Fairfield
• Immunity
Tablet EMI
: Digital source Termination
Slot
=
+
© 2011 ANSYS, Inc. June 18, 2012 42
EMI Design Results • Near Field and Far Field Spectrum
Tablet EMI
Simulation vs. Measurement
Simulation
Measurement
© 2011 ANSYS, Inc. June 18, 2012 43
Tablet Design Simulations were performed using
• Touchscreen – Q3D Extractor and DesignerSI
• Tablet Case – ANSYS Explicit Dynamic
• Packages – – Electrical: HFSS in Cadence, Q3D Extractor and TPA
– Thermal: ANSYS Icepak
• Flex circuitry – HFSS and Q3D Extractor
• Antenna - HFSS
• ESD - HFSS Transient and DesignerSI
• EMI – HFSS, DesignerSI
Tablets Design Solution
© 2011 ANSYS, Inc. June 18, 2012 44
Problem Meeting numerous tablet design options while meeting strict electrical standards and design specifications
Solution Automated modeling and optimized analysis using ANSYS Electromagnetics tools allows for system simulation approach
Result Detailed system simulation enabled tablets to be put on market on time with reduced testing costs
Conclusions
Pictures source: www.istockphoto.com