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August 19, 2004
http://www.parnell-eng.com
Finite Element Analysis and Design for Six Sigma
Important Tools Used in Conjunction with HALT
T. Kim Parnell, Ph.D.,P.E. PEC, www.parnell-eng.com OEI, www.ozeninc.com
Mike Silverman, CRE Ops A La Carte,www.opsalacarte.com
August 19, 2004
August 19, 2004
http://www.parnell-eng.com
FEA & DFSS
• FEA – Finite Element Analysis
• DFSS – Design for Six Sigmaalso includes:– Design sensitivity– Materials (variations)– Geometry (tolerance)– DOE – Design of Experiments– Distribution of results rather than just a
single result
August 19, 2004
http://www.parnell-eng.com
How do you use FEA?
• Finite Element Software– ANSYS– MSC.MARC, MSC.NASTRAN– ALGOR– ABAQUS– COSMOS
• Understanding of Loads, BCs, Materials• Create the model & Run the analysis
August 19, 2004
http://www.parnell-eng.com
FEA Model CreationSpeaker Normal Mode Analysis
Dia : 17mm
Thickness : 0.016mm
Mat : aluminum
E : 71e9 N/m^2
v : 0.3
p : 2700 kg/m^3
Element : Shell 63
: Mass 21
August 19, 2004
http://www.parnell-eng.com
FEA & DFSS Application Example:
MEMS Device - Linear Resonator
August 19, 2004
http://www.parnell-eng.com
• Package
• Chip is inside package
• Device is on chip19 mm
0.2 mm
Quality of MEMS Devices: Linear Resonator
August 19, 2004
http://www.parnell-eng.com
Device markets & Applications• ABS
• Seatbelt restraint/ tensioning
• Active suspension
• Rollover detection
• Headlight leveling
• Joysticks
• Mouse
• Earthquake detection
(gas shutoff)
• Electro-Mechanical Filter
Quality of MEMS Devices: Linear Resonator
August 19, 2004
http://www.parnell-eng.com
Multi-Physics Problem: Multi-Physics Problem: Electromagnetic & Structure InteractionElectromagnetic & Structure Interaction
Equilibrium between electro-magnetic forces and moving comb spring back
Random Input
• 14 different manufacturing tolerances +/- 10%
• Young’s Modulus +/- 10%
• Poisson’s Ratio +/- 10%
Output
Maximum Deflection
Quality of MEMS Devices: Linear Resonator
August 19, 2004
http://www.parnell-eng.com
One Tooth Model One Tooth Model only geometryonly geometry parameters studied parameters studied
Moving Comb Finger WidthMoving Comb Spine WidthMoving Comb Finger Thickness
• Only 3 out of 14 geometry parameters are important• Efficiently guide the design process to product
improvement• Efficiently guide the quality control process
Quality of MEMS Devices:Linear Resonator
August 19, 2004
http://www.parnell-eng.com
Entire Resonator Model Entire Resonator Model geometry and material studied studied
• Very good agreement between Monte Carlo (400 FEA) and Response Very good agreement between Monte Carlo (400 FEA) and Response Surface Methods (49 FEA + 10’000 on Response Surface)Surface Methods (49 FEA + 10’000 on Response Surface)
• Scatter Range of “Maximum Displacement” has about a factor of 3 Scatter Range of “Maximum Displacement” has about a factor of 3 between lowest and largest valuebetween lowest and largest value
Histogram of Maximum Distplacement
0
50
100
150
200
250
300
350
0.00
45
0.00
55
0.00
66
0.00
76
0.00
87
0.00
98
0.01
08
0.01
19
0.01
29
0.01
40
Response Surface
Monte Carlo Simulations
Quality of MEMS Devices:Linear Resonator
August 19, 2004
http://www.parnell-eng.com
• Very good agreement between Monte Carlo (400) and Response Surface Methods (49)
• Results enable a “Design for Reliability” (lower scrap rate, lower quality control cost, lower warranty costs)
Cumulative Distribution Function
0%
20%
40%
60%
80%
100%
0.0045 0.0065 0.0085 0.0105 0.0125 0.0145Maximum Deflection
Pro
ba
bili
tie
s
Monte CarloSimulationsResponseSurface
Quality of MEMS Devices:Linear Resonator
August 19, 2004
http://www.parnell-eng.com
Monte Carlo (400) Response SurfaceMethods (49)
• Very good agreement between Monte Carlo (400) and Response Surface Methods (49)
• Same 3 geometry parameters and Young’s Modulus are important• More efficiently guide the design process to product improvement• Efficiently guide the quality control process• Efficiently guide and justify lab test spending
Quality of MEMS Devices:Linear Resonator
August 19, 2004
http://www.parnell-eng.com
Random Input
• Drop Height
• Inclination angle
• Horizontal angle
• Densities
• …
Output
Maximum Stress
Reliability of Electronic Devices: Dropping of a Cell Phone
August 19, 2004
http://www.parnell-eng.com
Most Probable Scenarios
Wide range of results (ratio ~ 60), single deterministic run will not cover the real scenario
Reliability of Electronic Devices: Dropping of a Cell Phone
August 19, 2004
http://www.parnell-eng.com
•More efficiently guide the design process to product improvement
•Efficiently guide the quality control process
•Efficiently guide and justify lab test spending
Reliability of Electronic Devices: Dropping of a Cell Phone
August 19, 2004
http://www.parnell-eng.com
Summary
• Finite Element Analysis (FEA) and Design for Six Sigma (DFSS) techniques are both useful tools in their own right.
• They provide valuable insights and guidance when used in conjunction with a HALT program.
• Use them at both the front end (pre-HALT) and the back end (post-HALT).