[MacBook Air Teardown] Air Plays Key Role in Thermal Design [Part 6]

Mar 6, 2008
Mayuko Uno, Nikkei Electronics

What measures were taken against the heat problem in the MacBook Air? After all, heat is what confronts engineers who design digital consumer electronics including personal computers.

With the help of engineers specializing in thermal design, we explored Apple's stance on this issue. We gradually found that the notebook was designed so that users hardly feel the heat. The company employed simple heat dissipation methods such as exhausting heat by using air and preventing the unnecessary heat transfer by providing a gap (air) between the heat source and the adjacent parts.

The distinctive features of the thermal design in the MacBook Air include the followings: (1) The adoption of a slim fan and the layout of the ventilation ports, (2) a heat dissipation mechanism to prevent heat generated by the microprocessor and other parts from being directly transferred to the chassis and (3) treatment of the heat from the battery.

Consideration for making the heat unnoticeable

Among the parts used in a notebook computer, microprocessor is the component most likely to be affected by heat. The MacBook Air seems to be mounted with Intel Corp's 1.6GHz Core 2 Duo with a 4Mbyte built-in cache memory designed for laptops. The thermal design power, which corresponds to the maximum power consumption, of this processor is 17W. Considering the dimensions of this notebook, heat dissipation does not seem to be a big problem.

However, there is a problem that the entire chassis is made of aluminum alloy, which easily conducts heat to the entire body. When heat generated from one component is transferred to a certain part of the chassis, it is highly possible that the palm rest or other portions, where users often feel heat, also become hot. The thermal design in the MacBook Air showed Apple's efforts to reduce the heat the users feel.

When the Nikkei Electronics Teardown Squad used the MacBook Air for a short period of time, the temperature rise was negligible. We did not measure the heat generation and power consumption because the excited Squad members started to break down the main unit right away.

Hiding the fan

One of the key features of the MacBook Air's thermal design is the ventilation ports located at the back of the body and under the hinge block. A slim fan is used to draw in external air from the back side and exhaust air heated by a heat source again from the back side.

The layout is well designed to prevent the heat of warm air from being conducted to the chassis as much as possible.

"The ventilation ports located on the back of the body prevent exhaust air from blowing on the user and make the fan noise lower," one of the engineers who attended the teardown operation said.

This is the advantage of using the proprietary thin Li polymer secondary battery. Many Japanese slim laptops mount the secondary battery on the back side of the body to reduce the thickness of its front portion and to improve the usability. And they usually use a general-purpose secondary battery.

In this case, ventilation ports are located at the lateral side of the body. This often brings an undesirable thermal condition due to the lack of ventilation port area. And users may be annoyed by hot exhaust air blowing on their hands.

Preventing the heat transfer to the chassis

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