AN ARRANGEMENT FOR SHIELDING AND/OR COOLING ELECTRONIC COMPONENTS MOUNTED ON A CIRCUIT BOARD

Abstract: The present invention relates to an arrangement for shielding and/or cooling electronic components mounted on a circuit board. The arrangement includes a generally planar shielding hood having downwardly extending side edges which extend around the perimeter of the hood and which are intended to surround the component, and cooling elements which have a generally planar underside and cooling fins disposed on the upper side thereof. According to the invention, the arrangement also includes fastener means (5) in the form of hook means (6) mounted on the surface of the circuit board (2) and holder means (7) mounted on the cooling elements (4) and coacting with the hook means, wherein the holder means (7) can be brought into resilient or spring engagement with the hook means. The shielding hood (3) is adapted to the component (1) and when the component is to be shielded is placed over the component. The cooling element (4) is also adapted to the component (1) and when the component is to be cooled is placed either on the component or when appropriate on the shielding hood (3) over the component. The fastener means (5) are intended to press the cooling elements (4) resiliently against the shielding hood (3) and against the component (1) respectively.

Description: An arrangement for shielding and/or cooling electronic components mounted on a circuit board. TECHNICAL FIELD The present invention relates to a arrangement for shielding and/or cooling electronic components mounted on a circuit board. The arrangement includes a generally planar shielding hood having downwardly extending side edges extending around the perimeter thereof and intended for enclosing the com¬ ponents, and a cooling element having a generally planar underside and cooling fins or flanges arranged on its upper side. DESCRIPTION OF THE BACKGROUND ART Present day IC-components are becoming more and more in¬ tegrated and therewith more complex. Furthermore, clock frequencies and power generation constantly increase. Microprocessors are a typical case. Parameters such as heat generation and disturbance sensitivity increase with the increasing complexity of IC-components, necessitating the need to shield and cool said components. At present, there is no effective economic or technical solution which combines these requirements, which in reality contradict one another. The importance of providing effective screening or shielding of IC-components is reflected among other things in the discussions in present day mass media concerning, for instan¬ ce, how mobile telephones render diserviceable the electro- nics of motor vehicles, such as cars. There is therefore a pronounced need of a technically simple and economic shiel¬ ding/cooling construction which will fullfil simultanoeusly the stringent requirements placed on both these facilities. DISCLOSURE OF THE INVENTION The object of the present invention is to solve the aforesaid problem at low costs, by providing an arrangement which can be used either to solely shield an electronic component or solely cool an electronic component or which can be used to both shield and cool an electronic component in a simple manner and at low cost. This object is achieved by means of an arran¬ gement having the characteristic features set forth in the following claims. The inventive arrangement functions on the principle that in addition to functioning as a shield, the shielding hood shall also conduct heat to a cooling element. The construction is extremely flexible, and enables the following combinations to be obtained with precisely the same elements: shielding and cooling, solely shielding or solely cooling. When needing to both cool and shield an electronic component, the shielding hood is used as a cooling means and as a heat conducting means and is placed betwen the heat source, for instance an IC-circuit, and a cooling element. In order not to obtain an excessively large thermal transition resistance, the shielding hood and cooling element must have well-defined abutment surfaces with the heat source. This is achieved by configuringboth the shielding hood and the cooling element in a manner appropriate to the purpose intended. The primary characteristic feature of the invention resides in the ability to combine cooling and shielding. An embodiment of the invention at present preferred includes significant characteristic features which will now be described in more detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of the elements included in the inventive arrangement. Figure 2 is a sectional view showing the arrangement mounted over a component. Figures 3 and 4 are respective perspective views of the arrangement when used solely for shielding and solely for cooling respectively. Figure 5 is an alternative embodiment of an arrangement which is effective for both shielding and cooling purposes. BEST MODE OF CARRYING OUT THE INVENTION Figure 1 illustrates in perspective those elements which are included in an inventive arrangement. The illustrated arrangement is intended for shielding and/or cooling a component 1, for instance an IC-component, mounted on a circuit board 2. The arrangement includes a generally planar shielding hood 3, a generally planar cooling element 4, fastener means 5 in the form of hook means 6 and holder means 7 respectively, and contact springs 8. The shielding hood 3 has downwardly extending side edges 31 and the size of the hood is adapted to the size of the com¬ ponent 1, so that the component will be fully surrounded by the side edges. The hood 3 is secured to the board 2, by pressing the side edges 31 into contact springs 8 which are surface mounted on the board around the component 1. The side edges include nibs 33 which function to lock the hood firmly in the contact springs. The hood 3 is intended primarily for shielding the component, although it shall also be capable of functioning as a means for conducting heat to the cooling element 4 when the arrangement is also intended for cooling purposes. To this end, it is necessary for the surface of the hood 3 that abuts the component to be well defined, so that the thermal transition resistance will not be too large. Accordingly, the hood has the form of a relatively rigid frame having a thinner central part 32 which is joined to the frame and which can move in relation thereto. The thinner part 32 functions as a movable diaphragm which is pressed against the component 1 with the aid of the cooling element 4. This mobility of the diaphragm enables the height of the hood or • cover in relation to the height of the component to be readily adapted so as to ensure that positive abutment is achieved with a small heat transition resistance between component and cooling element, as shown in the sectioned view of Figure 2. The heat emitting surface area of the cooling element 4 is enhanced with the aid of a plurality of cooling fins 41 disposed on the upper side of the element. In addition, the cooling element 4 has a well defined abutment surface cor¬ responding to the shielding hood 3, so as to reduce the resistance to thermal transition or transfer. As shown in the sectioned view of Figure 2 , the underside of the cooling element 4 has a downwardlydirected, flat outwardlyprojecting part 42 which may either lie against the central part, the diaphragm 32, of the hood 3 when both shielding and cooling are required, or directly against the component 1 when only cooling is required. The cooling element 4 is held in place on the circuit board 2 with the aid of anchoring means 5 which in addition to providing a force which presses the cooling element, and the central part 32 of the hood, against the component also connects the cooling element 4 electrically to earth. In this regard, it is important that the cooling element is connected to earth at each corner. The anchoring means 5 are comprised of hook means 6 mounted on the surface of the board 2, and holder means 7, mounted on the cooling element 4, which coact with respective hook means. Each hook means 6 has a generally U-shaped profile, whose one leg has the form of a solder pad 61, said solder pads being soldered to corresponding solder pads (not shown) on the board 2. Each other leg of the profile has the form of a hooked part 62, which is bent so as to be upstanding from the circuit board. The holder means 7 is made of a resilient material having a part 71 configured to enable said part to be clamped firmly between two cooling fins 41 on the cooling element, or, alternatively, in a specially configuredgroove (not shown) provided onthe cooling element, and a stepped second part 72 in which an opening 73 is provided and which can be brought into resilient or spring engagement with the hooked part 62 of the hook means 6, as illustrated in Figure 2. A holder means 7 is placed in each corner of the cooling element, and a hook means 6 is placed in a corresponding position on the board 2. The spring effect thus obtained causes the cooling element 4 to be pressed into positive abutment with the shielding hood 3 and the component 1 respectively, which, as before mentioned, ensures good thermal contact between component and cooling element. The cooling element is, at the same time, positively earthed through the holding means 7 and the hook means 6, since anchoring means 5 are placed in each corner. The above described arrangement is used when a component or components is/are to be shielded and cooled. When only shielding is required, only the shielding hood 3 will be used, as illustrated in Figure 3. The hood is secured in contact springs 8 placed around the component 1 on the circuit board 2 and disposed so that the side edges 31 on the hood 3 will be inserted into the springs 8. This provides effective shielding of the component. The contact springs are also disposed so that the shielding hood 3 will be secured in the springs with the aid of the nibs 33, which are arranged on the sides of the hood in the manner indicated in Figure 1. The contact spring 8, however, forms no part of the present invention. When only cooling is required, the procedure is the same as that described above although in this case only the cooling element 4 is used, as illustrated in Figure 4. The cooling element 4 is secured with the aid of four fastener means 5, in the same way as that described above. There is sometimes a need to shield a group of components. This is made possible by the present invention, in that the shielding hood 3 is provided in the central part or the diaphragm 32 with a plurality of openings 34 which form a defined hole pattern in the hood, as illustrated in Figure 5. When requiring to cool a component, a cooling element 4 is placed over the component. The cooling element is affixedwith the aid of four fasteners 5, wherein the hook means 6, and more specifically the hooked parts 62, extend up through the opening 34 in the shielding hood 3. In this way, it is possible to arrange one or more cooling elements 4 with associated fasteners 5 on the hood 3, above the component or components 1 that requires/require cooling. However, only one cooling element has been shown in the Figure for the sake of clarity. It will be understood that the aforedescribed and illustrated embodiment is merely shown by way of example and that various alternative embodiments are conceivable. For instance the design of both the cooling element 4 and the fastener 5 and associated details can be varied in several ways without departing from the inventive concept. Consequently, the invention is not restricted to the aforede- scribed and illustrated embodiments thereof, since modifica¬ tions can be made within the scope of the following claims.

Claims: CLAIMS 1. An arrangement for shielding and/or cooling electronic components mounted on a circuit board, the arrangement including a generally planar shielding hood having downwardly extending side edges which extend around the perimeter of the hood and which are intended to enclose the component, and a cooling element having a generally planar underside and cooling fins disposed on its upper side, characterized in that the arrangement also includes fastener means (5) in the form of hook means (6) mounted on the surface of the board (2) and holder means (7) mounted on the cooling element (4) and coacting with the hook means and which can be brought into resilient or spring engagement with the hook means; in that the hood (3) is adapted to the component (1) and when shiel- ding wishing to shield the component is placed over said component; in that the cooling element () is adapted to the component (1) and when wishing to cool the component is placed either on the component or, when applicable, on the hood (3) over the component (1) ; and in that the fastener means (5) are intended to press the cooling element (4) resiliently against the screening hood (3) or against the component (1) respec¬ tively. 2. An arrangement according to Claim 1, characterized in that the shielding hood (3) is configured as a relatively rigid frame having a central, thinner part (32) which is adapted to the component (1) and which has the form of a diaphragm which is movable in relation to the remainder of the hood so as to obtain abutment with the component and the cooling element respectively and so as to ensure good thermal heat transfer between component and cooling element (4) . 3. An arrangement according to Claim 2, characterized in that the underside of the cooling element (4) is provided with an outwardly projecting part (42) which corresponds to the central part (32) of the hood (3) . 4. An arrangement according to Claim 1, characterized in that the shielding hood (3) is provided with a regular pattern of through penetrating openings (34) which are adapted so that the hookmeans (6) mounted on the circuit board (2) is able to extend up through the openings. 5. An arrangement according to Claim 4, characterized in that the shielding hood (3) is adapted to and placed over a plurality of components (1) ; in that a cooling element (4) is placed over the component or components (1) that delivers/de¬ liver heat and requires/require cooling; and in that fastener means (5) which press respective cooling elements (4) against the shielding hood (3) are provided at each heat emitting component, wherein each cooling element (4) is secured by means of holder means (7) in engagement with hook means (6) extending through the openings (34) in the shielding hood. 6. An arrangement according to Claim 1, characterized in that the holder means (7) are intended to be clamped in grooves especially provided in the cooling element (4) to this end, or between the cooling fins (41) of the cooling element. 7. An arrangement according to Claim 1, characterized in that a fastener means (5) is placed in each corner of the cooling element (4) .

Inventors: ARVIDSSON STIG ARTUR, HENNINGSSON BO UNO EGON, ARVIDSSON, STIG, ARTUR, HENNINGSSON, BO, UNO, EGON
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON
Application year: 1995
Main classification: H05K7
IPC codes: H01L23, H05K7, H05K9