The Cooling Trends & Techniques Of Consumer Electronic Devices

An interesting study on the cooling trends of consumer electronic devices.

→ 90% of the laptops utilize the [heat pipe> heat sink > forced convection cooling using fan] system as a whole to manage the thermals combining it with different types of heat spreaders.This is somewhat an active cooling by varying the cooling as a result of fan speed variation.

?→The Most used heat spreader is obviously the copper plate and on top of that Graphite Sheets are used a lot. Why ? Check out the report inside.

→ Thermal heat interface materials such as silica gel and other types of thermal pastes made up of zinc oxide and other compositions too are used.

→ The fans utilized have the ability to vary their RPM and hence variable heat transfer(greater the rpm, greater air volume CFM as well as static pressure) by using PWM[Pulse width modulation] tech.Mostly the fans are centrifugal because of the lower footprint and its ability to operate quietly* while delivering more static pressure to overcome the channels within the heat sink and within the overall package.

→ Another thing which is very much noticeable is the black powder coating on most of the heat pipes and heat? sinks on the top most visible surface. While it may be for aesthetic purposes, it also has its thermal contributions.We very well know that black coating/paints are good in absorbing heat and hence, retaining it for longer duration. The heat pipes need a certain temperature to change the phase of its working fluid(mostly liquid water to its vapor state) and as an effect of capillary action, the vapor flows to the cooler section which is the heat sink continuously cooled by a centrifugal fan, where the vapor condenses to regain its liquid state again. This process repeats and hence, the cooling is achieved.So, the black coat/paint on top surface allows the heat pipe to retain the working temperature across its operating window.?

→ Another interesting thing to note is the thermal gradient across the heat pipe is within 5-6 degree Celsius.

→ Fanless tech used mostly in Apple Macbook M1 and M2(not pro) uses vapor chamber cooling combined with graphite sheet heat spreaders and obviously their aluminum chassis as the heat rejection means. They don’t have any kind of active cooling like fans. The only drawback which I see here is if the rated temperature goes beyond the designed temperatures, then obviously de-rating happens(clock speed/frequency reduction) and hence, overall performance drop to achieve thermal equilibrium.Graphite sheets are almost everywhere within the macbook and Iphone.

→ To my surprise, Iphones don’t use heat pipes or even vapor chambers. But, the logic board uses quite thick copper pads sandwiched between the two stacked PCBs. Again, graphite sheets are present all across the top surface to spread the heat across a larger surface area.

→ The premium smartphone industry(except Iphones), uses a combination of vapor chamber, heat pipes, graphite sheets, graphene sheets, screen and the chassis itself as heat sink to achieve greater thermal efficiency.

→ To sum it up, the heat pipe based cooling and the vapor chamber based cooling has the majority in today’s consumer electronic devices cooling.

→ Another very interesting thing was the PGS[pyrolytic Graphite Sheet] from Panasonic which has a thermal conductivity of almost 1950 W/m.k(5x of copper). Properties and applications shown inside. If it works the way shown, it truly has remarkable properties specially for heat management of small form factor components with very high rates of heat generation over a small surface area.