BLACK&DECKERBLACK&DECKERJess Dibelka Jess Dibelka

Mark SteimerMark SteimerLaura Traub Laura Traub Julianne TwomeyJulianne Twomey

12/10/0712/10/07

Introduction

• Lithium-ion battery pack

• Metal Oxide Semiconductor Field Effect Transistor (MOSFET)

• Electrical switch that controls the speed of the drill head

• Introduces an electrical resistance

• Continuous current loading raises MOSFET temperature

MOSFET

• Small Voltage applied to gate

• Creates electric field across +p substrate

• Conduction bands allow large currents to flow through MOSFET

Trigger

Motor

75°C(OSHA)

Objectives

98 °C(Plastic Deformation

Temperature)

175°C

Goal: Reduce the temperature of the MOSFET junction during use to avoid failure

Quantity of Energy Absorbed

18V Circular Saw ABR Test Loading

0

10

20

30

40

0 200 400 600 800 1000

Time (s)

Cu

rren

t (A

)

JtRIE j 85.14012 Circular Saw Current Profile Used to Over Constrain Design

Heat Energy

Trigger

MOSFET

Motor

Rj

Target Values

Ranking Concept Metrics Target Value

1 Quantity of Heat Absorbed 1401.85 J2 Mass of Device 20.3 g3 Volume of Device <12 cm3

4 Qty Battery Cycles Before Tj = 175 oC 2

5 MOSFET Orientation 0 o Angle6 Unit Production Cost $0.137 Number of Assembly Parts 38 Number of Processing Steps 49 DOF of Device Within Casing 0

Heat Removal Concepts

Final Heat Sink Concept

Design Issues

• MOSFET Attachment/Orientation• Geometric fit within handle• Heat Absorbed • Thermal

– Thermal Gradient– Cp, K, ρ

Required Volume

CCT

cmTc

EV

oo

p

4098

37.9 3

Volume Analysis Heat Sink

Cast

• Aluminum 356

• V = 9.37cm3

Stamped

• Aluminum 6061

• V = 9.99 cm3

Using Law of Energy Conservation

Detailed Design Process

1) SolidWorks Modeling

2) Geometrically Fit in 3D Drill Handle

3) Thermal Model of Drill Handle

Thermal Model Drill Handle

Solid Works Design

Fit Design in Drill Handle

Stamped Concepts Eliminated

• Maximum gage thickness of 3 mm

•Stamping designs occupy more space than cast

• Copper mass significantly higher

Material Mass (g)

Al 6061 26.98

Cu 62.78

3 MOSFET Mounts = 3 Cast Designs

Oval Flange D-Sink

MOSFET wires bent 45oMOSFET wires rotated 90oMOSFET wires un-bent

Thermal Modeling

• Initial Solid Modeling

• Apply 1401 J of energy to heat sink

• Natural convection from heat sink

• Apply adiabatic wall on outer drill

handle

Heat Sink Temp Profile Heat Sink in Drill Handle

97.4 oC

95.3 oC

1401 J

Thermal Modeling Results

Heat Sink Temp Surface Plot

Drill HandleTemp Surface Plot

Design Constraints Flange Oval D-Sink

Max Heat Sink Temperature (Constraint < 98oC)

81.2 75.5 81.4

Max MOSFET Temperature (Constraint < 175oC)

85.3 76.3 83.4

Max Drill Handle Temperature (Constraint < 75oC)

67.4 44.0 62.2

Testing Overview

1) Indicate Heat Sink temperatures with simplified Box

Test

2) Test Heat Sink in Drill Handle

a. Heat Sink Thermal Repeatability

b. Test Procedure Repeatability

Testing Procedure

1) Attach thermocouples

2) Attach resistor and apply

thermal grease

3) Place Heat Sink in Box

4) Apply 1401 J of energy over

732 s

5) Obtain temperature profiles

Thermocouples

Test 1: Box Test

Testing Set-Up

Testing Procedure

Test 2: Drill Handle Test

1) Identical procedure

2) Heat sink placed in drill

handle

3) Thermal repeatability:

Flange tested 3 times

4) Test procedure repeatability:

Oval tested 2 times Thermocouples

Testing Data Collected

For each trial collected thermocouple readings for:

•Heat Sink•MOSFET•Handle

Heat Sink Testing Conclusions

Maximum MOS FET Temperature @ 40

oC Ambient 79.5 81.4 79.1

Maximum Outer H andle T emperature @ 40

oC Ambient 49.0 47.0 54.0

Maximum Heat S ink Temperature @ 40 o C Ambient 70.2 69.7 70.6

Max H eat S ink Temperature D ifference1.09 2.14 0.62

MOSF ET W ire Bend A ngle0 45 90

D-Sink TestingFlange TestingConstraints/ Metrics Oval Testing

9.93 cm3

Qty Battery Cycles before T j= 175oC 2.0.9 J /goC

• Relatively No Thermal Change Between Heat Sinks• Flange has Best MOSFET Attachment • Therefore : Flange is Best Design•Heat Sink Loading and Test Procedure Proved Repeatable

Design Process Conclusion

Temperature difference due to Adiabatic wall condition in Modeling.

Can re-design using FloWorks assuming 10oC Temperature difference.

FloWorks to Test Analysis

Heat Sink Flange Oval D-Sink

Drill Handle 10.42 ±.45 11.55 ± 2.46 9.36 ±.72

Box 15.10 ± 2.26 15.31 ± 2.93 13.10 ± 2.46

Average ∆T (FloWorks - Testing) ± Standard Deviation

Ultimate Re-Design

1) Incorporates 0° wire bend angle MOSFET attachment

2) Use FloWorks to yield max heat sink temperature of ~96oC.

3) Expect testing to yield a temperature of ~86oC

4) Leaving a Margin of Safety of ~10oCV = 6.45 cc

Ultimate FloWorks (oC)

Expected Test

Results (oC)

Maximum MOSFET Temperature 40 oC Ambient 102.2 92.2

Maximum Outer Handle Temperature 40

oC Ambient 66.4 56.4

Maximum Heat Sink Temperature 40

oC Ambient 95.95 85.8

Cost Analysis

Cost ($)Prototyping Machinist $2,100.00

Material $0.72Testing 20 Thermocouples $15.00Total $2,115.72

Production Heat Sink Cost $0.13

Validation Resources

•Machinist

• 10 hrs at $70/hr

•Material

•$2/lb, 50% scrap

•Thermocouples

•Production cost

•$30,000 tooling cost

•700,000 total parts

Path Forward- B&D• Confirm Predicted Test Results of Ultimate Design• Use Design Methodology to Develop Heat Sinks in Future

Tools• Receive Cost Quotes from Heat Sink Suppliers• Test Reliability of Bolt and Nut Attachment Under Long

Term Thermal Cycling• Adapt If Needed To Fit Other Tools

Summary

•All constraints and target values are achieved in heat sink design!!!

•Heat sinks and testing procedure are repeatable

• Difference in heat sink performance between FloWorks and Testing is ~10oC

•New “Ultimate” heat sink is lighter and incorporates positives of previous heat sinks

• Cost for Black and Decker to implement Ultimate is approximately 13 ¢ per heat sink

Questions

Thank You:Black and Decker

Daniel Brisach (Thermal Modeling Help)Roger Stahl (Rapid Prototypes)

& Dr. Glancey

Test Data CV

Flange Thermocouple 1 2 3 4 5Trial 1 52.29 52.95 52.99 53.44 53.09Trial 2 54.39 54.84 53.10 55.24 54.96Trial 3 53.14 54.04 53.00 54.43 53.99Average 53.27 53.94 53.03 54.37 54.01Standard Deviation 1.055 0.951 0.060 0.902 0.940CV 0.020 0.018 0.001 0.017 0.017

Oval Thermocouples 6 7 8 9 10Trial 1 54.90 54.95 55.25 54.80 55.56Trial 2 54.75 54.92 54.47 55.23 55.11Average 54.83 54.94 54.86 55.01 55.33Standard Deviation 0.1093 0.0215 0.5486 0.3079 0.3178CV 0.0020 0.0004 0.0100 0.0056 0.0057

Test Data Delta TBOX TESTFlange Thermoucouples 1 2 3 4 5Trial 1 49.6157 50.192 46.2467 48.9612 50.2699Flow Works oC 65.85 64.991 66.634 66.054 64.694Delta T 16.2343 14.799 20.3873 17.0928 14.4241Oval Thermocouples 6 7 8 9 10Trial 1 48.6948 46.136 49.6454 49.4585 48.3986Flow Works oC 64.912 64.387 64.451 64.397 64.355Delta T 16.2172 18.251 14.8056 14.9385 15.9564D-Sink 11 12 14 15 16Trial 1 50.7996 51.8578 51.6556 50.893 51.1887Flow Works oC 64.11 63.87 63.69 63.61 63.69Delta T 13.3104 12.0122 12.0344 12.717 12.5013Average Delta T 15.04543Standard Deviation 2.39503

Test Data Delta THANDLE TESTFlange Thermoucouples 1 2 3 4 5Trial 1 52.29 52.95 52.99 53.44 53.09Trial 2 54.39 54.84 53.10 55.24 54.96Trial 3 53.14 54.04 53.00 54.43 53.99Flow Works oC 66.06 66.25 67.11 66.17 65.53Delta T Trial 1 13.76 13.30 14.11 12.72 12.44Delta T Trial 2 11.67 11.41 14.01 10.92 10.57 Delta T Trial 3 12.92 12.20 14.11 11.74 11.53Oval Thermocouples 6 7 8 9 10Trial 1 54.90 54.95 55.25 54.80 55.56Trial 2 54.75 54.92 54.47 55.23 55.11

Flow Works oC 67.18 66.6 66.644 66.482 66.623Delta T Trial 1 12.28 11.65 11.40 11.69 11.07Delta T Trial 2 12.43 11.68 12.17 11.25 11.52D-Sink Thermocouples 11 12 13 14 15 16Trail 1 53.95 53.44 53.36 54.70 52.55 54.48Flow Works oC 65.54 65.46 65.61 65.69 65.38 65.50Delta T Trial 1 11.59 12.02 12.25 10.99 12.83 11.02Average Delta T 12.10Standard Deviation 0.97

Testing Target Value Results

Heat Sinks Satisfied the Constraints with ~ 20oC Margin of

Safety

2 Mass of Heat Sink (g) 25.91 25.26 25.78 24.80 29.82 25.05

3 Volume of Heat Sink (g) 9.39 9.36 9.34 9.19 9.36 9.28

Ranking Testing Prototype Metrics Flange Target Flange Actual D-Sink Target D-Sink Actual Oval Target Oval Actual

ConstraintMaximum MOSFET Temperature

@ 40 oC Ambient 175oC 79.5 81.4 79.1

ConstraintMaximum Outer Handle Temperature

@ 40 oC Ambient 75oC 49.0 47.0 54.0

ConstraintMaximum Heat Sink Temperature

@ 40 oC Ambient 98oC 70.2 69.7 70.6

1 Quantity of Heat Absorbed 1401.9 J Controlled Controlled Controlled

4 Qty Battery Cycles or Time before T j= 175oC 2 or 732 s Controlled Controlled Controlled

8 Max Temperature Change 1 oC 1.1 2.1 0.6

Testing Prototype Metrics Target ValueRanking D-Sink ActualFlange Actual Oval Actual

Testing ResultsFlange Repeatability

Plain English Statement

Example of CV

Poor control Cv = .2

Fair control Cv = .1

Tight control Cv = .05

Excellent control Cv = .025

World class Cv = .0125

Seldom achieved Cv = .000625

Courtesy of Dr. Glancey

Oval Test Repeatability

Thermocouple 1 2 3 4 5

Coefficient of Variability 0.083 0.077 0.004 0.076 0.082

Thermocouple 6 7 8 9 10

Coefficient of Variability 0.009 0.002 0.047 0.027 0.028

Energy Analysis MOSFET

JtRIE jin 85.14012

CT

RR

TT

t

E

oJ

TGJC

Jin

102

max

Total Energy Equation

Actual MOSFET Junction Temperature

Energy Calculations

Total Energy (J)Junction

Temperature (oC)

2 Battery Packs Resistance 150oC

1401.85 102.75

2 battery Packs Resistance 100oC

1168.21 101.96

Rotor Lock 1160.70 103.48

Energy Analysis Heat Sink

399.9 cmV

Tc

EV

TVcEE

p

in

pstin

Volume of Heat Sink Required

Thermal Analysis Handle

CT

TThATTL

kAWE

qqEE

oP

HSPHSout

convcondoutst

25.58

)()(91.1 21

TP

Thermal Analysis Constants

CT

R

R

cmA

cmASA

cmLcmK

Wk

oHS 98

0053.

0063.

7.23

3.4..6

1

3.

002.

100

150

22

21

CCT

W

CR

W

CR

stKcm

Wh

CT

oo

o

TG

o

JC

oHS

4098

2

48.

732

002.

98

2

Equation Constants

Material Properties Cp Al 6061

(J/goC)

Cp Al 356 (J/goC)

Cp Cu Anneal (J/goC)

ρ Al 6061 (g/cc)

ρ Al A356 Cast

(g/cc)

ρ Cu Anneal (g/cc)

K 6061 (W/mK)

K Al 356 (W/mK)

K Cu Anneal (W/mK)

0.896 0.963 0.385 2.700 2.680 8.960 167 151 385

V Stamping Al 6061 (cm3)

V Cast Al 356 (cm3)

V Stamping Cu (cm3)

m Al 6061 (g)

m Al 356 (g)

m Cu Anneal

(g)

9.99 9.37 7.01 26.98 25.10 62.78

Testing Calculations

AmpsI

VV

R

P

IRV

RIWP

18.6

309.

05.

91.1

)( 2