Cooling in a Confined Space: How Modern Miniature Devices Stay Thermally Manageable

1.The Thermal Challenge of the Miniaturization Era
2.Air Cooling at the Micro Scale: More than a small fan
3.Liquid Cooling at Miniature Scale: Targeted Heat Removal Where It Matters Most
4.BESTAR: A Comprehensive Supplier for Miniature Thermal Management
5.Conclusion

The Thermal Challenge of the Miniaturization Era
Electronics are shrinking. There is something that the latest generation of consumer gadgets have in common: they are all massive computing all capable in things that aren't even thought possible several years ago, such as smartwatches, VR headsets and ultra-thin laptops.
Heat does not shrink with the device. When power consumption is the same, a small chip at high clock speeds produces the same heat load as a large chip at lower clock speeds, but it's restricted by a much smaller surface area for heat to dissipate. The net effect is a power density problem, watts per square centimeter is steadily increasing and the physical space to accommodate the watts is remaining level or declining.
The traditional methods of achieving thermal management control don't easily transfer to this new condition. A large heatsink is not feasible or affordable in a VR headset. A bulky fan assembly is not going into a fitness tracker. Relying on limiting device performance to control heat isn't a solution acceptable to users who purchased the device to use it for its performance.
The question now for thermal engineers developing next generation of miniaturized electronics is how to remove heat efficiently, quietly and reliably from a space where there is little to no room to do so.
BESTAR has been working on solutions to just that question. BESTAR's competence in piezoelectric technology and MEMS relates specifically to the field of thermal management and is the reason why it has developed a product portfolio suited to today's actual thermal challenges which is found in modern devices. This blog will introduce two main technology, one is air cooling baed on micro piezoelectric silent fan and the other is a liquid cooling based on micro metal liquid pump. They should all be considered in depth.

Air Cooling at the Micro Scale: More than a small fan
The working principle of Air Cooling is very simple. When moving air across a hot surface, the heat will be transferred from the surface to the air that is moving, which will transport the heat away. The quicker the air can move and the greater the surface area the more heat you can remove per unit of time. This is known as convection cooling, and it has been the most widely-used approach for the cooling of electronics devices for many decades.
Air cooling is well developed and understood at the macro scale, in other words, at the level of the desktop computer, a server rack, an industrial piece of equipment.
Micro fans don't last long in this location due to a number of reasons. They have rotating parts(bearings) that wear as time goes on, and result in vibration over time. Their minimum thickness is determined by the geometry of the motor and blades. They utilise an energy source derived from a battery-powered device, and efficiency is directly related to runtime.
BESTAR's micro piezoelectric fan is so quiet and the fan is quiet enough to let people read and talk close by. Instead of a rotating motor which spins a blade assembly, they use piezoelectric actuation to drive airflow. Certain ceramic materials have a piezoelectric property, that is, they change shape with an applied electrical current, and BESTAR has far-ranging knowledge of the manufacture of such materials with the precision needed for actuator applications.
The physical implications of this solution are significant for the designers of devices. Since the fan contains no moving parts, it doesn't wear. The same thing should continue to work after years of continuous use. Vibration output becomes close to zero which is significant for devices that contain precision sensors, optical components or haptic feedback system which would be sensitive to the mechanical noise that occurs in the structure.
Micro Piezoelectric Cooling Silent Fan fulfills the thermal performance profile for the needs of mini devices. The fan provides a good flow per volume, making it provide a significant convective cooling effect at an acceptable form factor to a thermal designer. They have a response time of milliseconds which is crucial to devices that have heavy spikes in computation requirements.
The extremely thin dimensions of the BESTAR piezoelectric fan are not merely an advantage. In fact, it sometimes determines whether or not active cooling can be achieved in a certain device design. The other limiting factor is not thermal budget for many consumer electronics products, but size limitations to accept a cooling solution. When the design space is limited, a fan capable of fitting into the space will create of new design options which would not be possible with a thicker conventional fan.

Liquid Cooling at Miniature Scale: Targeted Heat Removal Where It Matters Most
When it comes to removing heat from surfaces, air cooling is very effective, but its effectiveness is limited when handling concentrated thermal loads. If the amount of heat being generated in a small area is high, then heat transfer from the top of the chip to the flowing air becomes the limiting factor. Heat can't be dissipated in the air as rapidly as it can in a liquid.
Liquid Cooling Technology uses its physical properties. Coolant fluids can absorb much more thermal energy per mass unit before their temperature increases, making it much larger than water, and even larger than air. Using just enough coolant to go around a hot chip, can remove considerably more of the heat from the chip than the same volume of moving air can remove.
Where liquid cooling technology is most readily seen to be useful in the case of miniature electronics is for those devices that have hot spots. An air-cooled system may not be able to manage a high thermal load from a high-performance processor on a small PCB, and the rest of the circuit temperature is relatively low. When the heat is removed in liquid form, engineers can direct the heat where it's needed, into a closed loop of fluid that can be channeled to the heat source and then brought back to a location where the heat can be dissipated.
The problem with liquid cooling is that it has involved using a pump, but pumps were invented and used to be bulky, noisy and expensive to use. It has been possible to build a liquid cooling loop into a gaming box this size. Until the pump size scales down to fit the envelope, it's very difficult to share the space, unless the device is made smaller than the mount.
To solve this problem, BESTAR has developed its miniaturized metal Liquid Pump (MMP10/MMP07). It provides the fluid circulation ability that a liquid cooling loop needs at a size and scale that makes them truly practical in compact devices. 
Due to the background expertise of BESTAR in piezo technology, the design way focuses on this. The absence of the conventional rotating pump mechanisms aids to make the unit more compact, user-friendly and with better life profile. If there are no mechanical wear elements in the pump, then the device doesn't decline during its operating life. The MMP10/MMP07 can solve the equation for thermal engineers designing high-performance, compact cooling systems. 

BESTAR: A Comprehensive Supplier for Miniature Thermal Management
BESTAR designs and produces the Micro Piezoelectric Cooling Silent Fan and Miniature Metal Liquid Pump that are the foundation of the company's thermal management products. The vertical integration guarantees control of the performance properties of the products of the BESTAR brand at the materials level. That is important when customers need the same performance throughout a high volume of production. 
While the company's engineering team assists customers with the component selection process, it also helps with integration. There are variables for heat transfer in application-related spaces that must be understood at the miniaturized level: thermal resistance of the surrounding package, flow characteristics of the insides of the package, thermal load profile in the particular chip that is being cooled, and which solution is applicable and how it must be configured. Instead, BESTAR helps developers deal with those variables, not that the user has to worry about integrating with a device.

Conclusion
In the coming years, the devices will be more sophisticated, smaller and more thermally challenging than the ones available now. The concept of piezoelectric air cooling, implemented in the BESTAR micro silent fan, provides convective heat removal without mechanical contact, near-silent performance and a very thin profile that fits into products where a conventional fan fails to fit. The BESTAR MMP10/MMP07 miniature pump is a liquid cooling system that provides high efficiency rinsing of the thermal load at a limited position and is compact enough to fit truly portable applications.
The thermal limit turns out to be an actual limitation for device performance. It is a thermal engineering problem if a device can't handle its own dissipation. When it's solved, the device could function at its intended level of performance, not at a reduced performance level because the temperature limits.
The practical benefit of what BESTAR creates is components that enable a miniature device to operate at optimal speed quietly, reliably and in the space necessary for the product design. The smaller and more capable devices become, this capability becomes more significant, rather than less.