1. Field of the Invention
This invention relates in general to an electrically-operated heat exchanger release mechanism, and more particularly, to a memory metal apparatus for providing a high engagement force between a heat exchanger and a central processing unit (CPU) while facilitating insertion and withdrawal of a printed circuit board (PCB).
2. Description of Related Art
It is common knowledge that CMOS integrated circuits can be chilled to sub-zero temperatures, thus creating an environment that allows higher operating frequencies. A common method of effectively chilling a CPU is to hold a heat exchanger (HEX) in intimate contact with the CPU's heated surface. One means of biasing the two surfaces together is to provide appropriate spring action. However, the best heat transfer is achieved when the spring pressure is high.
Further, a system PCB can normally be inserted and withdrawn from a card cage merely by pushing or pulling. Any other method of inserting or withdrawing the PCB is highly objectionable, especially if a tool is required. In most designs, the CPU is part of a PCB assembly. It is thus necessary to engage/disengage a CPU with/from its heat exchanger when the system PCB is inserted or withdrawn.
It should therefore be apparent that there are two conflicting requirements. First, optimum heat transfer is achieved when the spring pressure is high. Secondly, it is desirable to insert and withdraw the PCB from a card cage merely by pushing or pulling. Nevertheless, a high spring pressure between the CPU surface and the heat exchanger does not facilitate PCB insertion and withdrawal. On the contrary, the required high spring pressure makes it difficult to insert or withdraw the PCB. Furthermore, reducing spring pressure to ease insertion and withdrawal compromises heat transfer characteristics.
Accordingly, mechanisms have been designed to solve this dilemma. However, prior designs have exhibited disadvantages that make them undesirable. They are generally bulky, require manual operation to secure and release, easily broken, difficult to repair, and thus become stuck and are usually expensive.
It can be seen then that there is a need for providing the necessary high spring force while still facilitating insertion and withdrawal of the PCB.
It can also be seen that there is a need for a means for maximizing cooling while simultaneously facilitating insertion and withdrawal of the PCB without the use of tools.