Introduction of Thermal

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Introduction of Thermal

• GGT/RE Environment Test Team

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Primary Mechanic of Heat Transfer

• Thermal energy transport
• cause by temperature difference, high T -gt low T
• Conduction
• Heat transferring by solid medium
• Convection
• Transferring energy between solid surface and
  fluid
• Mass transport
• Natural (free) convection
• Forced convection
• Radiation
• Heat transferring by electromagnetic waves

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Conduction

• Fouriers Law
• Q -KA ?T/?L
• Q heat transfer rate
• A cross-sectional area of heat flux
• ?T/?L temperature gradient
• K thermal conductivity (W/mk)
• Ex. Al 230
• Cu 380
• Mylar 1.8

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Convection

• Newtonian cooling Law
• Qc hc As (Ts Ta)
• Qc convection heat transfer rate
• As surface area
• Ts surface temperature of solid
• Ta tmperature of ambient
• hc heat transfer coefficient, f(flow type,
  body geometry, physical property, temperature,
  velocity, viscosity)
• Natural convection Forced convction
• hc of air, natural convection 0.00150.015
  W/in2?
• forced convection 0.0150.15
  W/in2?

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Radiation

• Qa esAF1-2( Ts4 Ta4)
• Qa radiation heat transfer rate
• e emissivity, 0 ? e ? 1
• s Stefan-Boltzmann constant
• A surface area
• F1-2 view factor
• Ts temperature of body s
• Ta temperature of body a

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Thermal Resistance

• R V / I
• V voltage ?T temperature difference
• I current Q heat
• Conduction
• Rk ?L/KAk
• Convection
• Rs 1 / hcAs
• Radiation
• Ra (Ts Ta) /esAF1-2( Ts4 Ta4)

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Basic Concepts for NB Thermal Design

• Thermal Design Target
• Thermal design must meet thermal spec. of CPU,
  all key components (HDD, FDD, CD-ROM, PCMCIA),
  and all IC chips (Chipset, VGA, RAM, PCMCIA),
  and all IC chips (Chipset, VGA, RAM, Audio) in
  each user conditions
•  Thermal Resistance
• Tj-a (Tj Ta) / Pcpu
• T j-a CPU junction to ambient thermal
  resistance
• Tj CPU junction temperature
• Ta ambient temperature
• Pcpu CPU power

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Basic Concepts for NB Thermal Design

• System Thermal Coupling effect
• Tj-a (Tj Ta Tsys) / Pcpu
• Tsys system temperature Psys T
• SPi?i, (i DRAM, Chipset, HDD, FDD,
  CD-ROM)
• R thermal coupling factor between Pcpu and Psys
• Tj CPU spec. for Intel 100?
• Ta OEM spec., 35?
• Tj-a, Tsys OEM design dependent, Tsys 1015?

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Basic Concepts for NB Thermal Design

• Thermal Solutions
• Passive thermal solution
• Active thermal solution
• Hybrid thermal solution
• RHE
• Remote Heat Exchanger

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Basic Concepts for NB Thermal Design

• Characteristic of a good passive components
• Spreader plate connected to CPU should be as
  large as possible
• Temperature variation on spreader plate should
  be minimal
• Characteristic of a good active component
• Air inlet and outlet should be clearly defined
• Length of air passage through NB should be small
  to keep pressure drop low, flow rate high
• Possible reduce noise level of the fan
• Design must be capable of venting a portion of
  hot air from NB inside

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Important Components For Thermal Design

• Heat Sink
• Heat Pipe
• Fan
• TIM ( Thermal Interface Material)
• Combination of aforementioned components

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Heat Sink

• Material
• Material A1050 A6063 ADC12
  C1100
• K(W/mk) 230 210 192
  384
• Specific gravity 2.71 2.69 2.70
  8.92
• Production
• Die-casting
• Extruded
• Q -KA?T/?L
• Fin, Q hA?T
• Die-casting, extrusion, folder, stack, soldering
  fins

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Heat Pipe

• Basic configuration and characteristic
• Basic specification
• Material copper
• Working fluid pure water
• Standard working temperature 0100?
• Size ?3, ?4, ?5, ?6, ?8
• Typical heat pipe wick structures
• Fiber, mesh, groove, powder
• Typical modification of heat pipe
• Flattening
• Bending
• Heat Plate

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Fan

• Structure
• Rotator magnetic blade, shaft
• Stator bearing, wire, stainless plate
• Control circuit
• Theory
• Type
• Axial fan
• Blower fan
• Selection
• Total cooling requirement
• Q Cp m ?T ? Cp CFM ?T
• Total system resistance / system characteristic
  curve
• System operating point

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Fan

• Parallel and series operation
• Acoustical noise level (dB)
• To achieve low noise should consider
• System impedance
• Flow disturbance
• Fan speed and size
• Temperature rise
• Vibration
• Voltage variation
• Design considerations

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TIM

• Thermal Interface Material
• To reduce contact thermal resistance between CPU
  die and thermal module
• Important of TIM
• Material
• Various material silicon-base, carbon
• Non-phase change
• Phase change
• Pressure effect
• Pressure spec. on CPU spec. 100psi

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Thermal Design Procedure
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Thermal Design Guides

• Design guide for thermal (Ver. 0.2)

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• Thank You!

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fiber
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groove
Powder ?? ???????Heat Pipe??, ??????
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S
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N
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Static pressure
Fan curve
System resistance curve
System operating point
CFM(ft3/min)
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Thermal Module

• Reserve space for thermal module (Intel
  recommendation)
• Coppermine 705011.5mm
• Tualatin 755511.5mm
• Northwood 856019mm
• It should reserve a gap between thermal module
  and top cover (keyboard cover)

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1. Thermal Module

1. The gap between thermal module exit and NB case
   vent should be sealed well so the hot air
   couldnt flow back to system. If leave an open
   gap along air flow path, it will affect thermal
   efficiency and acoustic noise.

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1. Thermal Module

• The thermal module and CPU should contact well.
• The max pressure of the thermal module on CPU is
  100psi. Within SPEC, efficiency of thermal module
  increases with pressure.
• Its better to fix module on M/B by four screws
  (avoiding three screws) and spring design.

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2. Fan

• Fan inlet constraints gap 35mm is needed.
• 3mm 80 performance
• 4mm 90 performance
• 5mm 100 performance
• Configuration of air inlet outlet vents can
  make dramatically flow resistance therefore high
  open rate is better.

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2. Fan

• Dont place blocks (large ICs or connector) near
  or below the fan to affect airflow induced into
  fan.
• It is better for fixing fan by rubber instead of
  metal screws to avoid vibration.

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2. Fan

• The fan space design has some restrictions.
• For efficiency and acoustic, the gap between fins
  and fan blade should keep a distance of L 5 10
  mm.
• The distance W is better to keep as large as
  possible for good efficiency.
• Fan blade should close to fan tongue for better
  efficiency.

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3. PCMCIA Card

• Dont place PCMCIA on lower side of M/B, near
  hotter ICs, and stacked up key components (HDD,
  CD-ROM, DVD, FDD).
• If it needs to place PCMCIA near heat source, it
  is necessary to induce airflow to cool it.
• (Ex. For J2I, L1R, it is removed metal plate on
  PCMCIA slot and makes holes above PCMCIA if there
  is an Al plate upon it. By this way, air can flow
  through this area to cool PCMCIA card.)

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3. PCMCIA Card

1. Due to aforementioned solution, PCMCIA should
   place near fan in order to induce airflow to
   cool.

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4. Key Components

• Because HDD, CD-ROM, FDD thermal SPCE is low,
  these key components need to be placed in colder
  region.
• (Avoid placing them in the middle of the system
  and upon M/B with hot ICs, and stacking up each
  other).
• Its better to place FDD alone, not to put
  on/beneath CD-ROM or HDD.

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5. Palm-Rest and Glid Pad

1. It should avoid placing hot components and ICs
   below palm-rest and glid pad.
2. It should reserve a gap to make a thermal
   resistance between palm-rest and the hot
   components or to add a metal plate for spreading
   heat.

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6. LCD Inverter

• It should reserve a gap between Inverter and LCD
  cover to make a thermal resistance or to add a
  metal plate for spreading heat.

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7. Bottom case and Dimm Door

1. It should reserve a gap between IC chips and
   bottom case(gap gt 3mm is better).
2. It might have a large Al-plate on bottom case
   for spreading heat.
3. M/B has a hole below fan in order to induce
   airflow under M/B.
4. Its better to place hotter chips on upper side
   of M/B.
5. It should reserve a gap between Memory chips and
   dimm door (gape gt 1.5mm is better).

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8. M/B Layout

• If theres thermal issue of ICs, it should
  reserve space for thermal solutions
• (Ex. Dont place higher components beside these
  ICs, so it could put metal plate on ICs in
  future)
• Dont place low temperature spec ICs and
  components near hotter region or high temperature
  spec ICs and components.

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9. Others

• Its better to use the thinner or phase change
  TIM (thermal interface material)
• Ex. 28W CPU
• (phase change) Powerstrate
  0.08mm 75?
• (phase change) T-pcm
  0.25mm 83?
• T-pcm
  0.50mm 86?
• (phase change with Al)
• T-mate
  0.50mm 83?
• (non-phase change) Tx
  0.25mm 90?
• Tx
  0.5mm 96?

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9. Others

1. Heat pipes on thermal module have some
   restrictions
2. The thickness shouldnt be less than 2mm when be
   made flat.
3. The curve radius should be larger than triple
   diameter at least when be bended.
4. It might need some holes on bottom case and
   sidewall of NB in order to induce airflow to
   dissipate heat.

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3mm 80 performance 4mm 90 performance 5mm
100 performance
Air flow
35mm
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Bad design
Blocks
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Tongue
L ??, Fan???? ??, ????.
L
W
?????Fan ????, ?Noise ??????
W ????, ???
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Pressure
Single fan
Parallel
Double fan
CFM
Pressure
Single fan
Series
Double fan
CFM
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