Thermal Solution

Experience in Thermal Design of Electronic Devices
电子产品散热设计经验
The experience in and notes on the thermal solution design of electronic devices are summarized on the basis of years of design experience  and experimental analysis summary, specifically as follows:

以下我们根据多年的设计经验和实验分析总结,电子设备的热设计经验及注意事项如下:
1: Enough natural convection space should be ensured. There should be a certain distance at least 13mm, between components  and structures to facilitate air flow and enhance the heat dissipation of natural convection.
      保证足够的自然对流空间,元器件与结构之间应该保持一定距离,通常至少13mm,以利于空气流动,增强自然对流的散热.
2: The gap between the components on a vertically mounted board and surrounding PCB should be at least 19mm.
       垂直安装的电路板上的元件与周边PCB板之间间隙至少19mm
3: In terms of the heat conduction path, the metal or heat conduction material with high heat conduction coefficient can be used to  connect components with the shell or the cold plate for heat dissipation via larger surface area.
     导热的路径,可以利用导热系数较高的金属或是导热材料将元器件与外壳或是冷板相连,将热量通过更大的表面积散热.
4: The emissivity can be as high as 1 by radiant heat transfer and powder coat. In the same sealed shell, the temperature rise of  painted components is 10% lower than that of unpainted ones on average.
    应用辐射的传热,外壳表面喷涂烤漆,发射率可以达到很高,接近1,在同样一个密封的壳体中,表面烤漆比不烤漆的 元器件温升平均下降10%
5: If large radiator cannot be installed due to high heat flux components and limited assembly space, heat pipe or vapor chamber may be used; or the heat may be led to another location where there is enough space to install a radiator.
   如果高热流密度元品器件,而且装配空间有限,无法安装大散热器,可以采用热管或均温板将热量导到其它有足够空间 安装散热器的位置
6: Within the design life of the product, the failure rate of cooling system, such as the fan, should be lower than that of components.
    产品设计寿命内,冷却系统,比如风扇、水泵等,故障率应比元器件故障率低。
7: The safety margin must be considered upon thermal design. At least a safe temperature of 20-30 ℃ should be reserved; and a safe design margin should also be  reserved in consideration of an increase in heat consumption and flow resistance caused  by the failure of electronic devices during use.
  热设计必须考虑安全余量,至少要保留20-30度的安全温度,考虑电子设备使用过程中发生故障造成热耗和 流动阻力的增加的状态下,安全的设计余量
8: Natural convection, low speed fan and other highly reliable cooling modes should be used as far as possible.
  尽量采用自然冷却或是低转速的风扇等,这是可靠性相对高的冷却方式
9: When using the fan, attention should be paid to noise parameters, which must meet the design requirements for noise. Meanwhile,dust prevention and the protection device in front of the fan should be considered.  
  使用风扇时,要注意噪音的参数,符合噪音的设计要求,同时要考虑防尘和风扇前面的保护装置。
10: Product cost should be considered upon thermal design to ensure optimized cooling solution, simple product structure, high reliability, small volume and  cost.
  热设计时要考虑产品的成本,在保证散热方案优化,产品结构简单,可靠性、体积小,成本低。
11: Cooling system, such as the fan, should be easy to monitor and maintain.
  冷却系统 ,比如风扇等要考虑便于监控和维护
12: Each air duct should have clear air inlet and air outlet. Different air ducts should be isolated. Air flow short circuit between  different air ducts should be avoided, for example, the air outlet of air duct A should not be the air inlet of air duct B.
  每个风道要有明确的进风口和出风口,不同的风道要有隔离,对于不同的风道之间要防止气流短路,不能A风道的出风口是B 风道的进风口
13: In case of any vacancy of standard cabinet, a guide plate should be installed to prevent air flow short circuit for the air flow short circuit in the cabinet has great impact on the heat dissipation of components.
  标准的机柜如果有空缺位时,要装导流板,防止气流短路,机箱内部气流短路对元器件散热有影响非常大
14: The cooling by natural convection is applicable to sealed electronic devices with small volume and dense components.
  自然对流冷却适用于体积小、密封、元器件密集的电子设备。
15: The air is a poor conductor of heat. When the distance between heated surfaces is very short, the heat conduction by surrounding  air actually exists. In such case, The air is a poor conductor. A large number of our experiments proved that if the distance between
 two surfaces < 6.35mm, the heat transfer between the two surfaces is mainly realized through the air; and the heat transfer by natural convection can be neglected. If the distance between two surfaces > 12.7mm, heat dissipation is mainly realized by convection and radiation.

空气是散热的不良导体,当受热表面之间的距离很小,周围的空气产生热传导是真实存在的,此时空气为不良导体,我们大量的实验证明,如果两个面之间距离 <6.35mm ,则两面之间主要是通过空气进行换热,自然对流 换热可以忽略不计,如果两个面之间的距离>12.7mm,散热主要是通过对流 、辐射。
16: The black anodize surface can ensure excellent heat absorption and high emissivity, while polished surface has low emissivity and  can be used to shield heat radiation, for example, the emissivity of polished copper plate is 0.023 and that of black anodize can be as high as 0.95.
表面黑色会有良好的热辐射吸收,而且有较高的发射率,而抛光的表面发射率低,可以做屏蔽热辐射,比如 抛光的铜板发射率0.023,黑色氧化铁的发射率则高达0.95
17: The reflectivity of metal surface is associated with roughness: the reflectivity of shinny surface is higher than that of rough surface If a polished metal surface is powder coat black, its reflectivity will be improved.
金属表面反射率与粗糙度有关,光亮的表面反射率要高于粗糙表面的反射率,一个抛光的金属面,如果喷涂黑色后发射率会提高
18: In order to realize the maximum radiation heat transfer, it is suggested that the surface of the fin be black. It certainly should  not be understood as all surfaces should be black, for example, at 100 ℃, the emissivity of glass is equivalent to the reflectivity  of black powder coating. With the increase of temperature, the emissivity of glass may be 5-10% higher than that of black coating.
 为了实现最大辐射换热,建议散热片采用阳极黑色的表面,当然不能理解所有表面是黑色,比如玻璃在温度100时发射率与黑色涂层的反射率相当,并且随着温度升高,发射率会比黑色涂层的发射率还会高5-10%
19: Do not choose high-density fins for natural convection
 自然冷却时,不要选择高密集的散热片
20: At least a 30mm clearance should be reserved for the air inlet of the fan. If the air inlet is blocked, the noise will be 2-3 times higher. Besides, at least a 10mm clearance should be reserved for the air outlet for exhaust
 风扇进风口至少要保留30mm的距离,风扇进风口如果受阻产生噪音将是高于2-3倍,风扇的出风口至少保留 10mm的距离,需要排风。
21: Fans with different interfaces and different flows should not operate in parallel.
不要使用接口不同的风扇并联工作,也不要使用流量不同的风扇并联工作
22: If the fan adopts a filter, the loss of pressure drop should be considered.
如果风扇采用过滤防尘网时必须考虑压降的损失,确认开孔率对风压的影响。
23: For transformer, attention must be paid to the maximum temperature value of winding group. If the maximum temperature is  exceeded, the transformer will be damaged. Once the transformer is damaged, the whole device cannot work. If the transformer has a shielding case, it should be connected to the base as far as possible. The shell, magnetic core and base should be wrapped  with copper strips to enhance heat conduction.
变压器必须要注意绕线组的最高温度值,如果超过最高温度就会击穿绝缘层,造成变压器损坏,如果变压器坏整个设备将无法工作,如果变压器有屏蔽罩,应该尽量将屏蔽罩与底座连接,在外壳、磁芯、底座之间用铜带包围,加强热传导
24: Experiments showed that the heat consumption of hollow coil is low, thus no serious problem of heat dissipation will occur for  natural convection may be adopted. Upon thermal simulation, hollow coil can be taken as a cylinder. If only the natural convection
 of the external surface can be calculated when the coil is horizontally installed, when it is vertically installed, both the internal  surface and the external surface will cool down naturally.

实验表明,空心的线圈热耗较小,不会不产生严重的散热问题,可以采用自然冷却,在热仿真时可以当成一个圆柱体,线圈垂直安装时内表面和外表面都会自然冷却,如果水平安装只能计算外表面的自然冷却
25: During circuit design, long components should be distributed vertically (along the direction of gravity). Vertically distributed components should be alternatively arranged in horizontal direction.
在电路设计时,体积比较长的元器件应该采用垂直分布(沿着重力方向),垂直分布的元器件在水平方向应该交错排列
26: The heat emitted from the human body is about 100W, thus such heat should be considered during the thermal scheme calculation for outer space capsule.
人体的散热量约100W,如果进行航空领域外太空舱热方案计算时,要考虑人体的散热量。
27: For electronic device to be used outdoors in harsh environment, protector must be considered and installed in the protective shell as far as possible.
用于户外恶劣环境的电子设备必须要考虑保护装置,尽量安装在保护机壳内面,通道宽度在6.35 – 12.7mm 之间.
28: For a natural convection electronic device with an opening, the design of the shell should ensure that the air can flow in  from the bottom and flow out from the top and that the width of the air opening is between 6.35 – 12.7mm.
对于自然冷却的电子设备,有开口的,外壳在设计时应该重点考虑使空气从底部流入,从顶部流出,空气的通道宽度在6.35 – 12.7mm 之间
29: Sometimes, radiation must be controlled. Since the requirements for temperature rise are low, components with poor
temperature tolerance should be protected to avoid damage when heated. Generally, the use of smooth metal material as a  shielding case can effectively protect such components from thermal radiation, but there should be a permanent connection  between the thermal radiation and the PCB or the shell to form a feat transfer path.

有时要必须对热辐射进行控制,对温升要求低,耐温差的元器件要进行保护,以免受热损坏,一般将表面光滑的金属材料做屏蔽罩可以有效的保护这些元器件受到热辐射,但是屏蔽罩必须要与PCB板或是外壳有固定连接,形成传热的路径
30: Thermal design should consider ambient temperature, if a natural convection electronic product is installed in a cabinet,  with the increase of cabinet temperature, the design of natural convection probably cannot meet the ambient temperature in  the cabinet. If two forced convection devices are place in parallel,  the distance between them should be considered, otherwise the hot air discharged from one device may enter the air inlet of the other device, causing temperature rise.
设计要考虑环境温度,如果一个自然冷却的电子产品安装在机柜内,随着机柜的温度升高,可能自然冷却的设计就不能满足机柜内的环境温度,如果两个强迫冷却的设备并排放置在一起就要考虑放置的距离,否则一台设备排出的热空气会进入到另一台设备的进气口,造成温度上升
31: For electronic devices, ambient humidity should be considered. In addition, waterproof and dustproof designs should be  completed, or components will be damaged. Of course, attention should also be paid to the min  temperature. If the  min  temperature is lower than the min operating temperature of components, a heating unit should be equipped.
 电子设备要考虑环境的湿度,有防水,防尘的设计,否则造成元器件损坏,当然也要注意最低温度,如果温度低于元器件的最低工作温度要求,就需要考虑加热装置。
32: During natural convection, the temperature boundary is thick; if the fin spacing is too small, thermal boundary crossing will  occur, affecting surface convection. Therefore, it is suggested that the fin spacing > 12mm during natural cooling. If the fin  height is below 10 mm, the fin spacing can be calculated from the fin spacing > 1.2 times of the height.
自然冷却时温度边界比较厚,如果散热片间距太小,会产生热的边界交叉,影响表面的对流,所以一般在做自然冷却时建议散热片的Fin 之间的间距>12mm, 如果散热片Fin的高度低于10mm,可以按Fin的间距>1.2倍的高度来计算Fin之间的距离
33: During natural convection, the surface heat transfer ability of the fin is weak, the addition of corrugation on the fin has no impact on natural heat dissipation, thus the addition of corrugation on the fin is not recommended. Generally, during natural convection, black anodizing is recognized for it can increase the emissivity and radiation heat transfer on the heat-transfer surface.
自然冷却时散热片的表面换热能力比较弱,在Fin上面增加波纹对于自然散热没有影响,所以建议不要增加散热片Fin上面的波纹。自然冷却时一般建议采用黑色阳极氧化处理,可以增大散热表面的发射率和辐射换热
34: Since the thermal balance time of natural convection is long, the thickness of fin bottom plate and the fin adopting natural  convection should be considered to resist the impact of instantaneous thermal load. The thickness of fin bottom plate has great  impact on thermal capacity and thermal resistance. If the bottom plate is too thin, the thermal capacity is too small. If it is too  thick, thermal resistance will increase instead. According to experimental recommendation, the bottom plate should be 3-6mm  thick and the fin 2-5mm thick.
由于自然对流的热平衡时间比较长,所以采用自然对流的散热片的底板厚度和Fin的厚度需要考虑, 以抗击瞬时热负荷的冲击,散热片的底板厚度对于热容量及热阻有很大的影响,如果厚度太薄热容量小,如果过厚造成热阻反而增大,根据实验建议,底板厚度3-6mm, Fin的厚度 2-5mm
35: When forced cooling is adopted, it is suggested to add corrugation on the fin. The addition of corrugation on the surface can
 increase 10-20% of heat dissipation capability. If the corrugation is less than 0.5mm in height and is 0.5-1.0mm wide, the
 effect of heat convection can be enhanced.

强迫风冷,散热片建议增加Fin的波纹,表面增加波纹可以增强10-20%的散热能力,波纹高度小于0.5mm宽度 0.5-1.0mm,可以增强对流换热的效果
36: when the wind speed is higher than 1m/s, the natural cooling of the fin can be neglected.
当风速大于1m/s 时,可以忽略散热片的自然冷却
37: When fluid cooling solution is adopted, the pipe must be sealed. Pipe bending should be avoided as much as possible to
 reduce the loss of resistance; and the sharp expansion or contraction of the pipe should be avoided. Rectangular or square
 cooling plate should be used as much as possible, so as to polish the surface and reduce the thermal resistance.

采用流体散热方案时,管道必须密封,尽量避免管道弯曲,减少阻力损失,避免管道急剧的扩张或收缩,冷却板尽量使用长方形或是正方形,以便于抛光表面,降低接触热阻。
38: The material of air duct should be as smooth as possible on the surface to reduce air friction and minimize the airflow resistance.
 风道的材质尽量采用光滑表面,减少空气的摩擦,使气流阻力最小
39: For electronic device installed on walls, the air inlet and outlet should not be designed on the back of the device. If the air inlet
and outlet must be designed outside, the clearance between the device and the wall should be greater than 100mm.

 安装在墙体的电子设备,进出气口不能设计在设备的后面,如果必须要设计在外部,需要增加设备与墙体的距离大于100mm.

———————————————————————————————————————————————————————————————————————

Offers one of the highest quality and most diverse ranges of thermal management hardware in the world
To be able to make a sound evaluation and a better selection of thermal products for use in solving your thermal management
issues, you first need the most comprehensive range from which to make your choice. Renxin Seiko diverse range of the
highest quality thermal products and materials can facilitate in making this decision process easier. Renxin.Seiko extensive
product range has defined categories of product types. These have been arranged based on their physical and technical properties
for easier understanding. Deciding on which product best suits your application is crucial to the success and reliability of your
project. Renxin Thermal experienced engineers will gladly review your project and offer a design suggestion and product selection
from our extensive range. Free samples are readily available from our office for evaluation, please do not hesitate in completing
your request for samples as required. Our products are supported by our comprehensive and dependable technical support to help
you make the right engineering and commercial decisions, so feel free to email an enquiry or call our sales office today.