Http:// August 19, 2004 Finite Element Analysis and Design for Six Sigma Important Tools Used in...

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


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


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


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


FEA & DFSS Application Example:

MEMS Device - Linear Resonator

August 19, 2004


• Package

• Chip is inside package

• Device is on chip19 mm

0.2 mm

Quality of MEMS Devices: Linear Resonator

August 19, 2004


Device markets & Applications• ABS

• Seatbelt restraint/ tensioning

• Active suspension

• Rollover detection

• Headlight leveling

• Joysticks

• Mouse

• Earthquake detection

(gas shutoff)

• Electro-Mechanical Filter


August 19, 2004


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


August 19, 2004


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


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


August 19, 2004


• 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


August 19, 2004


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


August 19, 2004


FEA & DFSS Application Example:

Cell Phone Drop Test

August 19, 2004


Random Input

• Drop Height

• Inclination angle

• Horizontal angle

• Densities

• …

Output

Maximum Stress

Reliability of Electronic Devices: Dropping of a Cell Phone

August 19, 2004


Most Probable Scenarios

Wide range of results (ratio ~ 60), single deterministic run will not cover the real scenario


August 19, 2004


•More efficiently guide the design process to product improvement

•Efficiently guide the quality control process

•Efficiently guide and justify lab test spending


August 19, 2004


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).

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