1. Field of the Invention
The invention relates to a cooling apparatus based on the principle of using a working liquid to remove heat energy.
The need for cooling electronic components is an old and known problem, the significance of which is becoming more pronounced with increasing power and integration densities, since all electronic components generate heat, which has to be dissipated to accomplish an optimal and reliable operation of the components. As the field of electronics continuously progress in a direction where increasingly high powers are processed in increasingly small volumes, the dissipation of heat from components has become a decisive planning criterion. Many current electronic appliances need a cooling capacity that cannot be achieved by conventional metallic cooling fins.
2. Description of Related Art
New methods, such as heat pipes, have recently emerged along with conventional convection cooling. A heat pipe transfers heat very efficiently; its effective thermal conductivity is of the order of 1000 times that of copper. A heat pipe transfers heat from one end to the other as latent heat of phase transition, i.e. a liquid boils and evaporates in the hot end (an evaporator) of the pipe, and the created pressure difference makes the vapour move to the other, cold end (a condenser) of the pipe, where the vapour emits its latent heat and returns as a liquid to the evaporator, driven, for example, by capillary force. Heat pipes have been commercially available since 1960""s. Basically they can respond to the heating needs of electronics, but the industry has only recently begun to regard heat pipes as a reliable and advantageous solution for the cooling problems of the most demanding electronics applications.
Until now, heat pipes have generally transferred heat directly from a hot component to the cooling apparatus by each component having a separate heat pipe. It is extremely difficult, space-consuming and clumsy to place the heat pipes efficiently using this principal, particularly if there are several components requiring cooling on the same circuit board. In prior art solutions the heat pipes are generally either at the circuit board level, in which case the condensers of the pipes are cooled by heat sinks or the like on the sides of the board, or vertically against the circuit boards, in which case the heat sink is parallel to the circuit board.
U.S. Pat. No. 5,527,588 presents a cooling apparatus for cooling a heat source using heat energy bound to working fluid in phase transition. The cooling apparatus comprises a plurality of elongated cooling elements extending parallel in at least two levels so as to form a two-dimensional matrix of cooling elements. In addition, the cooling apparatus comprises a heat conducting material binding the cooling elements. In this cooling apparatus the cooling elements are used to transfer heat in two directions, parallel to the level of the cooling element matrix.
An object of the present invention is to provide a cooling apparatus for cooling electronic components which is superior to the ones used until now and by which the problems of placing heat pipes can be avoided. An exemplary embodiment of the invention provides a cooling apparatus comprising elongated cooling elements containing a working fluid. The elongated cooling elements extend in at least two different directions in order to form a matrix of cooling elements. The apparatus also comprises a heat conducting material configured for binding together the matrix of cooling elements.
The invention is based on multi-directional heat pipes integrated into a metal matrix composite structure.
The cooling apparatus of the invention is characterized in that the elongated cooling elements are arranged parallel to the circuit board level and in at least one direction deviating from the circuit board level.
The invention can significantly improve the cooling of thermally critical components and thus enable the implementation of more and more efficient electronic systems and/or reduce the costs caused by conventional cooling systems.