Laptop Cooling Basics

Transcription

1 Client Platform Engineering Laptop Cooling Basics Ketan R. Shah Principal Engineer Intel Corporation Q, 20

2 Laptop Cooling Basics - Agenda Laptop Cooling Challenges Laptop System Cooling Heat transfer modes System & motherboard layout Airflow & venting System analysis & design - Component interactions CPU Cooling Heat transfer modes Heatpipe basics Heatpipe heat exchanger Summary Laptop Cooling is a System Level Problem. Slide 2

3 Laptop Cooling Challenge I: Thermodynamic Limit: What goes in must come out! Exhaust CPU power load heats attach and heat exchanger Temperature ERGO LIMIT 70 C Chipset Memory, Wireless, etc., also contribute to exhaust temperature Exhaust T ~ Heat Removed Fan Flow Rate 3 cfm fan flow 60W dissipation Ambient 35 C System power envelope is fixed by fan airflow capability! 3 Slide 3

4 Laptop Cooling Challenge - II: Skin Temperature Problem # Each customer picks their own skin temperature limits Problem #2 Most current limits stretch or exceed the human ergonomic comfort level Jury Study! Notebook Skin Temperature Limits (o C) deg C (Plastics are 5-0C higher) Problem #3 Material type, thickness, and surface finish all matter ( temperature is NOT ENOUGH) Problem #4 Usage matters too notebook does not equal tablet or handheld System power capability is constrained by skin temperature needs. 4 Slide 4

5 Laptop Cooling Challenge: III: Acoustics Manufacturers spec fan noise: Bare fan different from in-system! Free flow different from insystem! Data collection The notebook-relevant test methodology Simulating Notebook Geometry 5 Plenum Tests Fans Under Load Slide 5

6 The change in predicted response as y ou v ary one f actor at a time, Measured the other f actors at their current v alues. Click in the graph to chang Fan Noise current v alues of the factors. Acoustics - Optimization Combining Intel metrology with DOE analysis Point Installed fan acoustic optimization ± db improvement shown! 46 db 4 db Installed Performance Installed optimum at ~32 mm CFD analysis of fan aeroacoustics Point ± db 37 db 2 Case height Inlet Dia (mm) 30 Bare Fan Performance 32 Slide 6 Inlet Bare fan optimum at ~40 mm 48 Blade

7 Annoyance Rating Acoustics Jury Study Binaural recordings made of notebook noise 22 Systems, 4 manufacturers Jurors Geography: USA, Sweden, Japan Binaural recording Head Office <30 dba Office >30 dba Outdoor <35 dba Outdoor >35 dba Outer ear Sound quality Brain Inner ear An Annoyance Model was developed. Includes sound pressure (loudness) AND sound quality SPL (dba) System acoustics need to be <35-40 dba. 7 Slide 7

8 Laptop Cooling Challenges - Summary Thermodynamic limit: Exhaust temperature Skin Temperature Acoustics Maximum system ambient temperature (@ inlet): 35 C In addition to the Component temperatures CPU, GMCH, memory, COMMs, VRs, etc., etc. 8 Slide 8

9 Energy Flow Conduction Convection Radiation Heat Transfer 0 3 Modes of Heat Transfer Conduction felt (!) if you touch it Θcond ~ L/k*A Hot Convection felt in hot rising plume Θconv ~ /h*a Radiation felt from all directions Θrad ~ /εt 3 *A Cold Hot Stove Element Conduction Increasing Thermal Resistance Magnitude Heat Pipe Metals Plastics Nominal Units C/W Convection High Speed Low Speed Radiation Very High Temp High Temp Ambient 9 Slide 9

10 Convection Air Flow and Venting 4 D C 2 3 A Fan Inlet Slit Vent Mem Vents C Side Inlet B Gaposis Inlet Vent Inlet All roads lead to Rome (the fan) Good to distribute flow paths azimuthally 0 Memory Vents Fan Inlet Side Inlet Slit Slide 0 B Gaposis A C D

11 Component Interactions Many components at Tj_max simultaneously Component to component influence: Conduction Convection Each component has local ambient : T local = T ambient + T sys T sys airflow 2 Determining T sys requires detailed platform level thermal simulations Accuracy challenges Significant benchmarking/calibration required Intel presents seminars on modeling methodologies to OEMs/ODMs Power component = (T j T local )/Θ Slide

12 Conduction The Motherboard Motherboard is warm around all key components provides bottom side cooling GMCH 73 C Proximity aggravates thermal problem (T sys ) HDI Smaller FFs CPU VR 88.8 C Clock generator 79 C CPU 79 C 2 Slide 2

13 Getting Heat Out of CPU Bare die thermal attach Density Factor (power map) critical Thermal Interface Material (TIM) Solid copper attach block Attach TIM Bare die 3 Slide 3

14 Thermal Interface Materials (TIMs) Fills air gaps Copper Attach Surface Lower High Θ junction_hp Improves thermal contact TIM Various materials used: Compliant High thermal conductivity Key issues: Pressure required Long term reliability Available CPU Heat Die Surface Flow Paths Microscopic view 4 Slide 4

15 Heat Pipes Your notebook uses liquid cooling High effective thermal conductivity along length Key issues: Max heat throughput (dry out) Minimum thickness 5 Slide 5

16 Fan and Heat Exchanger FANS Basic centrifugal blower used in most systems Heat Exchangers Nearly all systems use uniformly spaced vertical copper fins 6 Acoustics and Air Flow are king! Fan air flow defines system power envelope Slide 6

17 Laptop Cooling Basics - Summary Summary Laptop system cooling is designed to work with constraints of component temperatures, exhaust and skin temperatures, as well as acoustics. CPU cooling relies on multiple technologies of TIM, heatpipe, centrifugal blower, and heat exchanger. Laptop Cooling Requires an Integrated Approach. Slide 7