Ssi New Generation Dfss Case Study

DFSS Case Study Development Of A Robust Keypad

Project Summary

Client:

Large Telecommunication Equipment Manufacturer

Challenge: Design of a Robust Key Pad Goal: •Reduce generic contact problem: Target < 0,5% •Reduce total cost of the system: Target > 50% •Increase the click ratio (feeling): Target > 25%

Results: Following Results achieved due to DFSS implementation: •Project Savings > € 3,000,000 •Generic contact problem: Actual ~ 0 •Total cost reduction of the system: Actual > 75% •Increase the click ratio (feeling): Actual > 40% •Reduction in design Cycle Time: 1 months

IDOV Page 1

Identify •Project goals and objectives identified •All Critical To Satisfaction elements collected through Voice Of the Customer (VOC) process •Project team assembled and project plan created

IDOV Page 2

Identify •Detailed analysis of the existing Design and its failure modes •Analysis of Functional Requirements and Design Parameters

1. The key will be pushed down to the rocking point

2. Before clicking down the polydomefoil, the silicone key will be compressed

IDOV Page 3

Identify •Detailed analysis of the existing Design and its failure modes •Analysis of Functional Requirements and Design Parameters

3. After the abrupt click down of the polydome foil, the carbon coated inside of the polydome is contacting the carbon meander on the printed circuit board, genearating a short circuit

4. After this click feeling, usually customer will not push the key anymore, and if at this moment the carbon meander on the printed circuit board is not short circuited, then a contact failure will happen. If some additional force is applied, the carbon meander on the printed circuit will be short circuited, which is the unwanted situation Page 4

Identify Quantifying and measuring of the CTS after completed MSA (Measurement System Analysis):

force diagram

resistance diagram

X

shift “X” = bad function

F2

IDOV Page 5

Design Flow Down And Uncouple/Decouple Constraints Customer Domain

Deliverytime, Deliverytime,Cost Cost

Voice Of the Customer (VOC) (Customer Requirements (Y) Input

Constraints Physical Domain

Deliverytime, Deliverytime,Cost Cost

Generate Concepts

Generate Concepts

Evaluate Concepts

Evaluate Concepts

Input

Input

Disturbance

Disturbance

(Noise, Coupling)

Functional Requirements {FR}

Design Transfer Matrix

{FR} = [ D ]{DV }

Process Domain

Design Variables {DV}

(Noise, Coupling)

Process Transfer Matrix

Process Variables {PV}

{DV } = [ P]{PV }

IDOV Page 6

Design Flow Down And Uncouple/Decouple

{Y} = [I ]{FR}

{FR} = [D]{DV} {Y } = [ F ]{ X } {DV} = [P]{PV}

{Y} = [I] [P][D]{PV} 1424 3 [F ]

[I] = Unity Matrix [P] = Process Transfer Matrix [D] = Design Transfer Matrix [F] = System Transfer Matrix [FR] = Functional Requirements {DV } = Design Variables (Inputs, Control Parameters) {PV } = Process Variables (Inputs, Control Parameters) {Y} = Customer Requirement (CR)

IDOV Page 7

Design Flow Down And Uncouple/Decouple •Transferring Customer Attributes to Keypad Design Functions Y1 : To be able to dial and send SMS to different persons (Spoken, Performance) Y2 : To be able to notice the dialing (unspoken, must-be) Y3 : Quick access to telephone functions (unspoken, excitement) Y4 : Nice actuation of keys (unspoken, must-be) Y5 : To be able to transportation in trouser pocket/bag etc. (unspoken, must-be) Y6 : T be able to dial despite rainy days (unspoken, must-be) Y7 : Cool printing on keys (Spoken, Performance)

FD1 : Provide Dialing/Writing FD2 : Provide Dialing Signal FD3 : Provide Navigation FD4 : Prevent Key Stucking (%) FD5 : Provide Dust Protection (Norm) FD6 : Provide Spray Water Protection (Norm)

⎧Y 1 ⎫ ⎡1 ⎪Y 2 ⎪ ⎢0 ⎪ ⎪ ⎢ ⎪Y 3 ⎪ ⎢0 ⎪ ⎪ ⎢ ⎨Y 4 ⎬ = ⎢0 ⎪Y 5 ⎪ ⎢0 ⎪ ⎪ ⎢ ⎪Y 6 ⎪ ⎢0 ⎪Y 7 ⎪ ⎢ ⎩ ⎭ ⎣0

0 0 1 0 0 1 0 0 0 0 0 0 0 0

0 0 0 0 ⎤ ⎧ F D1 ⎫ 0 0 0 0 ⎥⎥ ⎪⎪ F D 2 ⎪⎪ 0 0 0 0 ⎥ ⎪ FD 3 ⎪ ⎪ ⎥⎪ 1 0 0 0 ⎥ ⎨ FD 4 ⎬ 0 1 0 0 ⎥ ⎪ FD 5 ⎪ ⎪ ⎥⎪ 0 0 1 0 ⎥ ⎪ FD 6 ⎪ ⎪ ⎪ 0 0 0 1 ⎥⎦ ⎩ F D 7 ⎭

FD7 : Provide 3D Surface Printing

IDOV Page 8

Design

Flow Down And Uncouple/Decouple •Transferring Keypad Design Functions to Design Variables FD1 : Provide Dialing

FD11 Transformation of a mechanical linear movement to displacement

FD111 F max

FD112 @ Displacement x max

FD12 Snapping (Click Feeling) (F min at x min)

X D1 : Actuating Keypad System

FD13 Contact on PCB (< 300 Ohm, Contact > 99 %)

FD121 F min

XD111-1 Silicon Hardness

FD131 < 300 Ohm

FD122 @ Displacement x min

X D11 Actuator

FD132 > 99 %

XD111-2 Web Design

XD112 Plunger Height

X D12 Polydome

XD121-1 Thickness

XD122 Height

XD121-2 Diameter

X D13 Carbon PCB / Polydome

XD131-1 Type

XD131-2 Pitch

XD132 Plunger Diameter

IDOV Page 9

Design

Flow Down And Uncouple/Decouple •Transferring Keypad Design Functions to Design Variables Hierarchy 1 FD2 : Dialing Signal

X D2 : Audio Signal (Original Design : Speaker)

FD3 : Navigation

X D3 : Navigation Key

FD4 : Key Stucking (%)

X D4 : Key Gap

FD5 : Dust Protection (Norm)

X D5 : Dust Sealing

FD6 : Spray Water Protection (Norm)

X D5 : Water Sealing

FD7 : 3D Surface Printing

X D7 : Tampon Print

⎧ F D1 ⎫ ⎡ A11 ⎪ FD 2 ⎪ ⎢ 0 ⎪ ⎢ ⎪ ⎪ FD 3 ⎪ ⎢ 0 ⎪ ⎢ ⎪ ⎨ FD 4 ⎬ = ⎢ 0 ⎪ FD 5 ⎪ ⎢ 0 ⎪ ⎢ ⎪ ⎪ FD 6 ⎪ ⎢ 0 ⎪ FD 7 ⎪ ⎢ ⎭ ⎣ 0 ⎩

0

0

0

0

0

A 22 0

0 A33

0 0

0 0

0 0

0

0

A 44

0

0

0 0

0 0

0 0

A55 0

0 A66

0

0

0

0

0

0 ⎤ ⎧ X D1 ⎫ 0 ⎥⎥ ⎪⎪ X D 2 ⎪⎪ 0 ⎥ ⎪ XD 3 ⎪ ⎪ ⎥⎪ 0 ⎥ ⎨ XD 4 ⎬ 0 ⎥ ⎪ XD 5 ⎪ ⎪ ⎥⎪ 0 ⎥ ⎪ XD 6 ⎪ ⎪ ⎪ A77 ⎥⎦ ⎩ X D 7 ⎭

Design Variables XD1, XD2 are integrated in the same physical area (New Design :Actuator) to reduce the complexity

Design Variables XD5, XD6 are integrated in the same physical area (New Design :Polydome foil sticked on PCB) to reduce the complexity

IDOV Page 10

Design

Flow Down And Uncouple/Decouple •Transferring Keypad Design Functions to Design Variables Hierarchy 2

⎧ F D11 ⎫ ⎡ A11 ⎪ ⎢ ⎪ ⎨ F D12 ⎬ = ⎢ 0 ⎪ F D13 ⎪ ⎢ 0 ⎭ ⎣ ⎩

0 A 22 0

0 ⎤ ⎧ X D11 ⎫ ⎪ ⎪ 0 ⎥⎥ ⎨ X D12 ⎬ A33 ⎥⎦ ⎪⎩ X D13 ⎪⎭

Independency of Design Functions Uncoupled Design Transfer Matrix

IDOV Page 11

Design

Flow Down And Uncouple/Decouple •Transferring Keypad Design Functions to Design Variables Hierarchy 3 ⎧ F D111 ⎫ ⎡ A11 ⎪ F D112 ⎪ ⎢ 0 ⎪ ⎢ ⎪ ⎪⎪ F D121 ⎪⎪ ⎢ 0 ⎬=⎢ ⎨ D122 F ⎪ ⎢ 0 ⎪ ⎪ F D131 ⎪ ⎢ 0 ⎪ ⎢ ⎪ ⎪⎩ F D132 ⎪⎭ ⎢⎣ 0

A12 0 0 0 0 0

0 A 23 0 0 0 0

0 0 A34 0 0 0

0 0 A35 0 0 0

0 0 0 A 46 0 0

0 0 0 0 A57 0

0 0 0 0 A58 0

⎧ X D111 − 1 ⎫ ⎪ X D111 − 2 ⎪ ⎪ 0 ⎤⎪ ⎪ X D112 ⎪ 0 ⎥⎥ ⎪ ⎪ X D121 − 1 ⎪ ⎪ 0 ⎥⎪ ⎪ ⎥ ⎨ X D121 − 2 ⎬ 0 ⎥⎪ X D122 ⎪ ⎪ 0 ⎥⎪ ⎥ ⎪ X D131 − 1 ⎪ A69 ⎥⎦ ⎪ ⎪ D131 − 2 X ⎪ ⎪ ⎪⎩ X D132 ⎪⎭

Redundant Design Variables Coupled Design Transfer Matrix but the Sensitivities will be checked experimentely

IDOV Page 12

Design

Concept Generation & Selection Concept Generation, Selection, and Feasibility using structured methodologies:

IDOV Page 13

Design

Preliminary Design Not critical key height (less compression)

Old System

Expensive gold meander on the old PCB system Easier to contact because of the min. pitch and low contact resistance of gold

Critical key height (high compression)

New System

Inexpensive graphite meander on the new PCB system Difficult to contact because of the min. pitch (technology limitation) and high contact resistance

IDOV Page 14

Design

Detailed Design

Hardcap Silicone Polydomfoil Spacerfoil

IDOV Page 15

Design

Functional Block Diagramming •Function Block & P-Diagramming Noise Factors Compression Input Signal : Linear Mechanical Movement

Snap-In Output Signal (Functional Requirement) : F max at x max

F F max

Output Signal (Functional Requirement) : F min at x min

F

1

F min

β x max

x

x min

x

Control Factors (Design Parameters) Silicon Hardness

Plunger Height

Polydome Hight

Web Design

Polydome Thickness Polydome Diameter

Project Boundry (Projekt Focus)

Page 16

Design

Functional Block Diagramming •Function Block & P-Diagramming Noise Factors Force to Signal Converter (Key Contact on PCB Meander) Input Signal : F min at x min

F F max

Output Signal Short on Meander (< 300 Ohm, 99%)

Time Delay

Electric to Acoustic Converter Output Signal (Functional Requirement) : Audio Signal

1

x max

x

Control Factors (Design Parameters) Carbon Type

Plunger Diameter Carbon Meander Pitch

Project Boundry (Projekt Focus)

Page 17

Design

Robustness Noise Factors

Make the Design robust to noise factors.

Control Factors

IDOV Page 18

Noise Factor Effect (Function Dialkeys) Main Effects Plot for Means

Operator

Device

Act.Directio

149

Mean

147

145

143

141

S

er g aa

t n le 1 e u B

2

rt. e V

iz. r o H

CNF2 (Compoung Noise Factor 2) = Op1 + Device 1 + Actuator Direc. Vertical CNF1 (Compound Noise Factor 1) = Op 1 + Device 2 + Actuator Direc. Horizontal

IDOV Page 19

Control Factor Effect for S/N Ratio Function Dialkeys Main Effects Plot for S/N Ratios

PCB Pitch

Plunger Dia

Spacer

PET

Dome Dia

Dome Shape

48,0

S/N Ratio

45,5

43,0

40,5

38,0

6 0,

8 0, D

E 75u

0u 00u 5 1 1

5u mm 2 1 5

l m rma 6m no

t f la

= Control Factor Levels already implemented in design

IDOV Page 20

Control Factor Effect for Means Function Dialkeys

Main Effects Plot for Means

PCB Pitch

Plunger Dia

Spacer

PET

Dome Dia

Dome Shape

280

Mean

240

200

160

120 6 0,

8 0,

D

E

u 75

0u 00u 1 15

5u mm 12 5

al m 6m norm

t fla

IDOV Page 21

Design

Transfer Functions Utilize Design of Experiments to create transfer functions A

B

C

D

E

F

0,6

E

75u

100u

5mm

normal

0,6

E

75u

125u

6mm

flat

0,6

D

150u

100u

5mm

flat

0,6

D

150u

125u

6mm

normal

0,8

E

150u

100u

6mm

normal

0,8

E

150u

125u

5mm

flat

0,8

D

75u

100u

6mm

flat

0,8

D

75u

125u

5mm

normal

First rough samples with holes in the plungers to increase the contact area and forces

Main Effects Plot for Means

A

B

C

D

E

F

220

Mean

190

160

130

100

0,

6

8 0,

D

E

75

u

15

0u

10

0u

12

5u

5m

m

6m

m no

rm

al

fl a

IDOV

t

Page 22

Design

Correction of Transfer Matrix •Transferring Keypad Design Functions to Design Variables FD1 : Dialing

FD11 Transformation of a mechanical linear movement to displacement

FD111 F max

FD12 Snapping (Click Feeling) (F min at x min)

X D1 : Actuating Keypad System

FD13 Contact on PCB (< 300 Ohm, Contact > 99 %)

FD121 F min

X D11 Actuator

XD111-1 Silicon Hardness

FD131 < 300 Ohm

XD111 Web Design

X D12 Polydome

XD121-1 Thickness

XD121-2 Diameter

X D13 Carbon PCB / Polydome

XD131 Type

XD131-2 Pitch

XD121 Plunger Hole Depth FD112 @ Displacement x max

FD122 @ Displacement x min

FD132 > 99 %

XD112 Plunger Height

XD122 Height

Design Variables fixed to a choosed value Patent Pending

XD132 Plunger Diameter XD132 Plunger Hole Dia.

IDOV Page 23

Design

Correction of Transfer Matrix •Correction of Design Transfer Matrix Hierarchy 3 ⎧ F D111 ⎫ ⎡ A11 ⎪ F D112 ⎪ ⎢ 0 ⎪ ⎪ ⎢ ⎪⎪ F D121 ⎪⎪ ⎢ 0 ⎨ ⎬=⎢ F D122 ⎪ ⎪ ⎢ 0 ⎪ F D131 ⎪ ⎢ 0 ⎪ ⎪ ⎢ ⎪⎩ F D132 ⎪⎭ ⎢⎣ 0

0 A 22

0 0

0 0

0 0

0

A303

0

0

0 0

0 0

A 44 0

0 A55

0

0

0

0

0 ⎤ ⎧ X D111 ⎫ 0 ⎥⎥ ⎪⎪ X D112 ⎪⎪ 0 ⎥ ⎪⎪ X D121 ⎪⎪ ⎬ ⎥⎨ 0 ⎥ ⎪ X D122 ⎪ 0 ⎥ ⎪ X D131 ⎪ ⎥⎪ ⎪ A66 ⎥⎦ ⎪⎩ X D132 ⎪⎭

Design Variables introduced in same physical area

Uncoupled Design Transfer Matrix

IDOV Page 24

Design

Flow Down And Uncouple/Decouple •Transferring Keypad Design Variables to Process Variables Hierarchy 3 XD111 : Web Design

X P112 : Insert 1

XD112 : Plunger Height

X P112 : Insert 2

XD121 : Plunger Hole Depth

X P112 : Insert 3

XD122 : Polydome Height

X P1221 : Temperature X P1222 : Cycle-Time X P1223 : Pressure

XD131 : Carbon Type

X P131 : Temperature

XD132 : Plunger Hole Diameter

X P132 : Insert 4

IDOV Page 25

Design

Transfer Functions •Checking design parameter to process variable relation and fixing redundant process variables (cycle time, pressure) to obtain robust parameter XD122 Polydome Height

Polydome Height Temperature

74.0

Cycletime

Pressure

Temperature

Cycletime

Pressure

37.20

71.5 S/N Ratio

Mean

36.95

69.0

36.70 36.45

66.5

36.20

64.0 0 12

0 14

0 15

5

7

9

6

7

11

0 12

0 14

0 15

5

7

9

6

7

11

IDOV Page 26

Design Correction of Transfer Matrix •Transferring Keypad Design Variables to Process Variables Hierarchy 3 XD111 : Web Design

X P112 : Insert 1

XD112 : Plunger Height

X P112 : Insert 2

XD121 : Plunger Hole Depth

X P112 : Insert 3

XD122 : Polydome Height

X P1221 : Temperature X P1222 : Cycle-Time X P1223 : Pressure

XD131 : Carbon Type

X P131 : Temperature

XD132 : Plunger Hole Diameter

X P132 : Insert 4

Process Variables fixed to a choosed value

IDOV Page 27

Optimization

Surface Plot of C NS

quantifying of the optimum functionality of the dialkey

8 7 6

C NS

5 4

Surface Plot of Q D4

3 2, 2,5

X

3,0

1,0

1,1 1 1

1,2

1,3

1,4

1,,5

1,6

Z

3,5

350

300

Q D4

250

200 2, 2,5

X

3,0

1,0

1,1

1,2

1,3

1,4

1,,5

Z

1,6

quantifying of the optimum volume of noise of the Navikey

3,5

IDOV Page 28

Optimization

IDOV Page 29

Control Factors for Taguchi DOE

•

We will focus to change the keypad plunger design to enlarge the contact area

•

The following factors will be defined with 3 levels as controllable factors

Hol e dept h

Hol e di amet er Pl unger di amet er Pl unger Di st ance

IDOV Page 30

Taguchi DOE Analysis for Noise Factors

Main Effects Plot for Means

customer

case

Contact poin

294

Mean

293

292

291

290 r ee Pi

ou Zh

A

B

ak Pe

de Si

IDOV Page 31

Taguchi DOE Analysis for Control Factors •

Analysis result: Main Effects Plot for Means of left key inside

Main Effects Plot for S/NRatios of left key inside Actuator

Offset Plung

Web Thicknes

Plunger Slan

Actuator

Offset Plung

Web Thicknes

Plunger Slan

300 49.2 280

Mean

S/N Ratio

48.4

47.6

240

46.8

220

46.0 2 1. 6* 2. 4*

•

260

.2 *1 .9 *1 3 3.

1* 1. 5* . 2

1 0. A-

A

.1 +0 A

20 0.

27 0.

35 0.

0

6

12

2 1. 6* 2. 4*

.2 *1 .9 *1 3 3.

1* 1. 5* . 2

1 0. A-

A

.1 +0 A

20 0.

27 0.

35 0.

0

6

12

After cross-functional discussion with Suppliers, the following parameter will be used in verify phase for the confirmation run:

IDOV Page 32

Validate

Force

Resistance

Quantifying and measurement of CTS after project completion:

no shift = good function

IDOV Resistance

Displacement Page 33

Validate Validate the Design using Life Cycle Tests Version:

New Keypad System

Number of samples:

2x2 pcs/cavity

Number of hits:

200.000

testing cycles:

Force-Stroke-Measurement 50.000 times --> F/s diagram OK 100.000 times --> F/s diagram OK 150.000 times --> F/s diagram OK

Testing result: No. of cycles 0 50.000 100.000 150.000

4 7 8 9 9 9 ? ? ? ? ? ? 4 cracks 9 9 at cavity 4 only the navi-key was damaged

15 9 ? ? 9

IDOV Page 34

Project Results

•Time frame: Target 4 months, achieved 3 months •Generic contact problem: Target < 0,5%, achieved almost 0 •Reduce total cost of the system: Target > 50%, achieved > 75% •Increase the click ratio (feeling): Target > 25%, achieved > 40% •Savings due to achieved results > 3 Million Euro •Development Cycle Time reduction for the next product generation because of the cancelled second iteration with soft tools •Same keypad system implemented in all the families of the existing and the next product generation •Patent Application for: “Polydomfoil Keypad with Optimized actuators”

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