Abstract:
On a fastening element for securing a thermal conducting bag filled with liquid comprising a frame a number indivudual resilient tongues are attached. Such an arrangement obtains that a pad or bag filled with liquid securely can be positioned in the frame at the same time as the indivdually resilient tongues maintains the flexible characteristics of the pad filled with liquid

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a device for cooling of electronic components. In particular the invention relates to a fastening means for fastening a pad or bag filled with fluid as a thermal element of contact.  
         BACKGROUND OF THE INVENTION AND PRIOR ART  
         [0002]    Today a rapid miniaturisation takes place in electronics. A problem then occurring is that traditional methods of cooling and cooling devices no longer are able to provide the cooling required for correct operation of the electronics.  
           [0003]    Another consequence of this miniaturisation is that the need for screening of components increases. Thus, higher clock frequencies are uses, which increases radiation.  
           [0004]    In FIGS. 1 a - 1   c  a structure which can be uses for obtaining booth proper cooling and proper screening is shown. Thus, as its shown in FIG. 1 a,  the electronic components are located on different levels located in a frame comprising cooling flanges. In this tower structure the components are contained in metal cassettes which are connected to the outer cooling flanges in the common frame. FIG. 1 b  is a cross section of such a cassette where the different electronic components  101  are shown.  
           [0005]    In such a structure shown in FIG. 1 a  and FIG. 1 b  the components are mainly cooled via thermal conduction in the circuit board. Thus, the components generating much thermal heat must be located close to the cassette edge as is shown in FIG. 1 c.    
           [0006]    One possibility to increase the freedom in location of the components is to thermally connect the upper sides of the components to the walls  113  of the metal cassette, as is shown in FIG. 2. In FIG. 2, which is similar to FIG. 1 b,  thermal contact elements  103  are located between the inner electronic components and the housing  113  of the cassette. Such a thermal connection can be achieved in a number of different ways. One way of obtaining such a thermal connection is by means of using a pad or bag filled with liquid. In for example U.S. Pat. Nos. 5,640,303 and 5,720,338 such pads filled with liquid are described in different embodiments.  
           [0007]    However, there is a problem of securing or fastening such thermal conducting pads filled with liquid. Thus, a pad filled with liquid provided for being in contact with one or several electronic components in order to conduct thermal heat from these electronics components can come out of position. This is of course not desired since large part of the cooling then is lost and the component may be overheated.  
         SUMMARY  
         [0008]    Its an object of the present invention to provide a fastening element for a thermally conducting pad filled with liquid which securely keeps the pad at the intended position without reducing the flexible characteristics of the pad.  
           [0009]    This object and others are obtained by a fastening element comprising a frame on to which a number of individually resilient tongues are attached.  
           [0010]    Such an arrangement achieves that a pad or bag filled with liquid securely can be fixed within the frame, while the individually resilient tongues achieves that the desired flexible characteristics of the pad filled with liquid are maintained. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention will now be described in more detail with reference to the accompanying drawings, in which:  
         [0012]    [0012]FIGS. 1 a - 1   c  illustrates the principle for locating electronics components in a so called tower structure.  
         [0013]    [0013]FIG. 2 is a view of an electronic structure similar to the view in FIG. 1 b.    
         [0014]    [0014]FIG. 3 shows a fastening element for a pad filled with liquid.  
         [0015]    [0015]FIG. 4 shows a cross section of a pad filled with liquid attached to an electronic component.  
         [0016]    [0016]FIGS. 5 a -  5   c  shows a fastening element according to another embodiment. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]    In FIG. 3 a fastening element  105  for a pad or bag filled with liquid is shown. The fastening element  105  comprises a frame  107  in which a number of tongues  109  are provided. In the embodiment shown in FIG. 3 the tongues project in towards the center of the frame  107 .  
         [0018]    In FIG. 4 a bag  111  filled with liquid provided as a thermal element of contact on an electronic component  101  is shown. The bag ill filled with liquid thermally connects the upper side of the component  101  with a cooling wall  113 . The wall  113  can for example be a part of the housing of the cassette as described above.  
         [0019]    The bag  111  filled with liquid is fastened to the wall  113  using a fastening element  105 . Using a fastening element having multiple individually resilient tongues projecting toward the center of the fastening element and thus also to the center of the bag filled with liquid when this is secured in the fastening element will achieve that these tongues will, using a resilient force, press the content of the bag towards the center of the bag.  
         [0020]    At the same time the resilient tongues achieves that the content of the bag is pressed upwards and downwards in the figure, respectively. This results in that the bag will press against the component as well as the cool wall  113 . When the content of the bag is a material with good thermal conducting characteristics an efficient cooling of the components will be obtained in this way.  
         [0021]    The content in the bag can suitably be a material having good thermal conducting characteristics. For example, a fat, an oil, a wax or a paraffin like material can be used. The liquid in the bag can also be electrically conducting. Thus the bag can also contain particles of metal, which significantly increases the thermal conduction.  
         [0022]    The bag or pad itself can suitably be made of a metal film coated with a plastics material, such as an aluminium film.  
         [0023]    In FIGS. 5 a - 5   c  another embodiment of a fastening element with an associated bag filled with liquid is shown. The fastening element as shown in FIG. 5 b  is designed to fasten a bag filled with liquid provided to act as a thermal conducting element for several electrical components located in a line. In FIG. 5 a,  a bag  141  in especially design for cooling a number of electronic components located in a line is shown.  
         [0024]    In FIG. 5 b  a fastening element  143  which can be used for fastening the bag  141  shown in FIG. 5 a  is shown. The fastening element  143  in FIG. 5 b  comprises an elongated frame having a resilient tongues formed on it&#39;s long sides.  
         [0025]    Since the bag  141  is provided for cooling a multitude of components located on a line, the fastening element  143  is designed to efficiently secure the elongated bag at the same time as the ability of the bag to even out differences in size of the electronic components and maintaining a pressure to the wall and to the electronic component is maintained.  
         [0026]    In FIG. 5 c  a view from the side where the fastening element  143  is used for fastening a bag  141  for cooling of electronic components  101  located on a circuit board is shown. The bag  141  secured in this way conducts thermal heat from the electronic component to a cooling wall, such as the cassette wall described above.  
         [0027]    The fastening element as described herein can also be designed for fastening a bag provided for thermally connecting an entire matrix of electronic components, such as an entire plane of the tower structure described above.  
         [0028]    Even if the fasten element has been shown as formed in one single work piece, it is also possible to manufacture the frame and the tongues in different materials if this should turn out advantageous in some application. Further more, it is not necessary that the fastening element is shaped as a closed structure and it is thus also possible to form a fastening device comprising a number of the different sub-elements which together form an entire fastening element.  
         [0029]    For example, the fastening element as shown in FIG. 5 b  could be formed by two different sub-elements, i.e. the two rows of tongues could be formed on two different sub-elements, which when they are fasten to a wall co-operates and forms an entire fastening element.  
         [0030]    By means of using the fastening elements as described herein a bag or pad filled with liquid can be securely positioned at the same time as the individually resilient tongues achieves that the desired flexible characteristics of the pad filled with liquid is maintained.