《产品的热设计》PPT课件

Characteristic of a good passive components
1. Spreader plate connected to CPU should be as large as possible
2. Temperature variation on spreader plate should be minimal
Introduction of Thermal
GGT/RE – Environment Test Team
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Primary Mechanic of Heat Transfer
Thermal energy transport:
cause by temperature difference, highl Resistance
R=V/I
V: voltage = ΔT: temperature difference I: current = Q: heat
Conduction
Rk = ΔL/KAk
Convection
Rs = 1 / hcAs
Radiation
Ra = (Ts – Ta) /εσAF1-2( Ts4 – Ta4)
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Basic Concepts for NB Thermal Design
System Thermal Coupling effect
Θj-a = (Tj – Ta – Tsys) / Pcpu
Tsys: system temperature = Psys *Θ = ΣPi*θi, (i: DRAM, Chipset, HDD, FDD, CD-ROM…)
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…)
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
R: thermal coupling factor between Pcpu and Psys
Tj: CPU spec. for Intel: 100℃ Ta: OEM spec., 35℃ Θj-a, Tsys: OEM design dependent, Tsys = 10~15℃
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Basic Concepts for NB Thermal Design
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
Fourier’s Law
Q= -KA ΔT/ΔL Q: heat transfer rate A: cross-sectional area of heat flux ΔT/ΔL: temperature gradient K: thermal conductivity (W/mk)
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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
Qa: radiation heat transfer rate ε: emissivity, 0 ≦ ε ≦ 1 σ: Stefan-Boltzmann constant A: surface area F1-2: view factor Ts: temperature of body s Ta: temperature of body a
Thermal Resistance
Θj-a = (Tj – Ta) / Pcpu Θ j-a : CPU junction to ambient thermal resistance
Tj: CPU junction temperature
Ta: ambient temperature
Pcpu: CPU power
Characteristic of a good active component
Natural convection & Forced convction
hc of air, natural convection: 0.0015~0.015 W/in2℃ forced convection: 0.015~0.15 W/in2℃
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Radiation
Qa = εσAF1-2( Ts4 – Ta4)