When designing embedded PC systems it is very important to take into consideration the thermal aspects of the system.
Embedded Industrial PC systems are typically required to operate continuously and in unusual environments where maintenance is difficult. It is therefore important for them to be able to dissipate the heat they create in order that they can operate reliably.
First thing's first...
The first thing to consider is selecting components with a low TDP (Thermal Design Power). This refers to the processor (CPU), graphics processor (GPU) and supporting chipsets. This keeps the power consumption and heat dissipation lower and reduces the need for convection or conduction cooling.
Convection cooling uses mechanical fans to force air to flow around the system components and then exhaust the heat out externally. Alternatively the conduction cooling method allows the heat to be conducted from the heat sources to the external surfaces of the system where it is then dealt with. Some systems also use a mixture of these methods with a heat exchanger being used to remove the heat from a sealed system.
In many applications, mechanical fans are not favoured as they are subject to wear which will eventually render them ineffective. This can be mitigated with preventative maintenance by changing the fans before predicted failure point but this adds a servicing cost and can be difficult to achieve in remote locations and unusual installations.
More typical embedded PC systems use the conduction cooling method to avoid the possibility of mechanical failure of the cooling system. Heat can be transferred away from the CPU, GPU and chipsets by using a variety of different solutions.
Direct connection with copper or aluminium blocks can be made if it is certain that there will be little chance of movement of the device in relation to the metal block. If there is likely to be movement then sprung loaded metal blocks can be used. Copper has better heat conduction than Aluminium but costs more.
There are other ways...
Alternatively, use can be made of heat pipes to transfer the heat away from the devices. This method uses sealed copper pipes containing water and the water carries the heat away as water vapour and then the cooled water wicks back to repeat the cycle again. Heat pipes are much more flexible and allow heat to be transferred in more difficult mechanical environments.
Thermal paste or thermal pads can also be used to improve the heat transfer from the device to the metal block or heat pipe. This mechanism is often used to transfer heat from a CPU to a cooler (a combination of a finned metal block and a fan). Make sure that the protective tabs are removed from the thermal pads!
Diamond coating can also improve conduction heat transfer but this is a very expensive method typically used in deeply embedded systems which may also be subjected to shock and vibration. The diamond coating allows for a mechanically robust thermal connection between the heat dissipating semiconductor devices and the conducting material.
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