BLACK&DECKER Jess Dibelka Mark Steimer Laura Traub Julianne Twomey 12/10/07

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 Circular Saw Current Profile Used to Over Constrain Design Heat Energy Trigger MOSFET Motor RjRj

Target Values

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 Volume Analysis Heat Sink Cast Aluminum 356 V = 9.37cm 3 Stamped Aluminum 6061 V = 9.99 cm 3 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 MaterialMass (g) Al Cu62.78

3 MOSFET Mounts = 3 Cast Designs Oval Flange D-Sink MOSFET wires bent 45 o MOSFET wires rotated 90 o MOSFET 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 ProfileHeat Sink in Drill Handle 97.4 o C 95.3 o C 1401 J

Thermal Modeling Results Heat Sink Temp Surface Plot Drill HandleTemp Surface Plot Design ConstraintsFlangeOvalD-Sink Max Heat Sink Temperature (Constraint < 98 o C) Max MOSFET Temperature (Constraint < 175 o C) Max Drill Handle Temperature (Constraint < 75 o C)

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 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 10 o C Temperature difference. FloWorks to Test Analysis Heat SinkFlangeOvalD-Sink Drill Handle10.42 ± ± ±.72 Box15.10 ± ± ± 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 ~96 o C. 3)Expect testing to yield a temperature of ~86 o C 4)Leaving a Margin of Safety of ~10 o C V = 6.45 cc Ultimate FloWorks ( o C) Expected Test Results ( o C) Maximum MOSFET Temperature 40 o C Ambient Maximum Outer Handle Temperature 40 o C Ambient Maximum Heat Sink Temperature 40 o C Ambient

Cost Analysis 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 ~10 o C 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

Test Data Delta T

Testing Target Value Results Heat Sinks Satisfied the Constraints with ~ 20 o C Margin of Safety Constraint Maximum MOSFET 40 o C Ambient 175 o C Constraint Maximum Outer Handle 40 o C Ambient 75 o C Constraint Maximum Heat Sink 40 o C Ambient 98 o C Quantity of Heat Absorbed JControlled 4 Qty Battery Cycles or Time before T j = 175 o C 2 or 732 sControlled 8 Max Temperature Change 1 o C Testing Prototype MetricsTarget ValueRankingD-Sink ActualFlange ActualOval Actual

Testing Results Flange Repeatability Plain English Statement Example of C V  Poor controlC v =.2 Fair controlC v =.1 Tight controlC v =.05 Excellent controlC v =.025 World classC v =.0125 Seldom achievedC v = Courtesy of Dr. Glancey Oval Test Repeatability Thermocouple12345 Coefficient of Variability Thermocouple Coefficient of Variability

Energy Analysis MOSFET Total Energy Equation Actual MOSFET Junction Temperature

Energy Calculations

Energy Analysis Heat Sink Volume of Heat Sink Required

Thermal Analysis Handle TPTP

Thermal Analysis Constants Equation Constants

Material Properties

Testing Calculations