In a heating element to be mounted in electronic equipment including a computer, a heating value has increased in association with achievement of high performance. For example, the heating value is particularly large in a central processing unit (CPU) mounted in the electronic equipment, and therefore a thermal conductor such as a heat sink is generally installed in the CPU. In the thermal conductor, weight increases according to achievement of size increase the like for responding to increase of the heating value in association with achievement of high speed of the CPU. If the weight of the thermal conductor increases, transport of the electronic equipment is liable to become difficult, and simultaneously an excessive load is liable to be applied to the CPU in which the thermal conductor is installed. Moreover, the increase of weight of the thermal conductor to be mounted in an automobile or the like results in deterioration of fuel consumption.
For the above reason, provision of a lightweight thermal conductor without reducing heat-dissipation performance is required, and as one means therefor, study has been conducted on using graphite having thermal conductivity equivalent to or higher than the conductivity of copper or the like, and density lower than the density of copper for a material to be used in the thermal conductor.
Specific examples of a conventional technology on a heat dissipator in which such a kind of graphite is used include an art in Patent literature No. 1.
As described above, the heating value has recently increased in the electronic equipment in association with achievement of high performance and high function, and therefore use of a thermal conductor having superb heat-dissipation characteristics is required in the equipment. An art to the effect of using as such a thermal conductor a laminate prepared by causing adhesion of a graphite sheet and a metal sheet by an adhesive is disclosed (Patent literature Nos. 2 to 5).
The Patent literature No. 3 describes an art to the effect of using a rubber-like elastic adhesive or a silicone-based thermally conductive adhesive as an adhesive, the Patent literature No. 4 describes an art to the effect of using an adhesive in which an electrically conductive filler, such as silver, gold and copper is contained, and the Patent literature No. 5 describes an art to the effect of using an acryl-based adhesive.
Moreover, Patent literature No. 6 describes that achievement of high performance of heat-dissipation performance and weight reduction can be realized by a heat sink configured by forming a laminate of a graphite sheet and a metal thin sheet into a corrugated shape, and connecting the laminate on a heat sink base in a metal thin sheet part.