产品的热设计.

1、 Introduction of Thermal GGT/RE Environment Test Team Primary Mechanic of Heat Transfer Thermal energy transport: cause by temperature difference, high T - low T Conduction Heat transferring by solid medium Convection Transferring energy between solid surface and fluid Mass transport Natural (free)

2、convection Forced convection Radiation Heat transferring by electromagnetic waves 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 Convection Newtonian cooling Law

3、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 therefore high open rate is better. 2. F

4、an 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. 2. Fan The fan space design has some restrictions. nFor efficiency and acoustic, the gap between fins and fan blad

5、e should keep a distance of L= 5 10 mm. nThe distance W is better to keep as large as possible for good efficiency. nFan blade should close to fan tongue for better efficiency. 3. PCMCIA Card Dont place PCMCIA on lower side of M/B, near hotter ICs, and stacked up key components (HDD, CD-ROM, DVD, FD

6、D). 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.) 3. PCMCIA Card

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

8、cking up each other). Its better to place FDD alone, not to put on/beneath CD-ROM or HDD. 5. Palm-Rest and Glid Pad It should avoid placing hot components and ICs below palm-rest and glid pad. It should reserve a gap to make a thermal resistance between palm-rest and the hot components or to add a m

9、etal plate for spreading heat. 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. 7. Bottom case and Dimm Door It should reserve a gap between IC chips and bottom case(gap 3mm is better). It might have a lar

10、ge Al-plate on bottom case for spreading heat. M/B has a hole below fan in order to induce airflow under M/B. Its better to place hotter chips on upper side of M/B. It should reserve a gap between Memory chips and dimm door (gape 1.5mm is better). 8. M/B Layout If theres thermal issue of ICs, it sho

11、uld 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. 9. Others Its better to use the thinner or phas

12、e 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 9. Others Heat pipes on thermal module have some restrictions The thickness sh

13、ouldnt be less than 2mm when be made flat. The curve radius should be larger than triple diameter at least when be bended. It might need some holes on bottom case and sidewall of NB in order to induce airflow to dissipate heat. 35mm Air flow Fan 3mm 80% performance 4mm 90% performance 5mm 100% perfo

14、rmance Fan Blocks Bad design L W Tongue 該縫隙越小該縫隙越小Fan 效效 率越高率越高, 但但Noise 也會隨之上升也會隨之上升 L: 太大太大, Fan效率效率 下降下降; 太小太小, 噪音上升噪音上升. W: 作為風道作為風道, 盡量大盡量大 Single fan Double fan Parallel CFM Pressure Pressure CFM Single fan Double fan Series TIM: thermal interface material 考慮將散熱器固定於發熱器件的方法時, 重要的 是要使二者之間界面熱傳到處效率最大. 也應考慮其他要求, 如介電特性, 電導性, 附著強 度和再次安裝的可能性. 發熱組件和散熱器之間界面的熱傳輸效率取決於 空氣殘留, 填充物類型和黏合曾的厚度等參數. 方 法優 點缺 點 機