GB2076141A

GB2076141A - A Cooling Device for Discrete Electronic Components and/or Circuit Boards on which Components are Mounted

Info

Publication number: GB2076141A
Application number: GB8113327A
Authority: GB
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1980-05-13
Filing date: 1981-04-30
Publication date: 1981-11-25
Also published as: IT8121675A0; IT1137472B; GB2076141B; SE8003579L; DE3117758A1

Abstract

The device comprises a hermetically sealed space containing a vapourisable medium, the space being provided by a cooling plate with a cooling flange member (5) attached to the upper portion of the plate, the member being provided with tapering flanges (51-54) and having its interior formed with an upwardly tapering cavity (6). The cooling plate, to which the components to be cooled are attached, comprises two mutually parallel flat walls (1, 2) which contain at least one cavity in the form of channels from the upper portion of the plate to its lower portion, and sealing means (7) for the channels at the lower part of the plate, the lower part of the tapering cavity (6) opening out into the channels. The flanges (51- 54) on one side of the tapering cavity (6) are offset from those on the opposite side whereby flanges on each side can partially engage in spaces between flanges of an adjacent cooling device. <IMAGE>

Description

SPECIFICATION A Cooling Device for Discrete Electronic Components and/or Circuit Boards on Which Components are Mounted The present invention relates to a cooling device for discrete electronic components and/or circuit boards on which components are mounted A suitable field of use is within aero engineering where great demands are made on restricted weight and volume.

Electronic components in the art of telecommunications as well as electric power engineering generally require some form of cooling. This is also particularly applicable for integrated circuits mounted in microcircuit capsules of different kinds to conduct away the heat generated in the semiconductor wafer, so that the properties of the semiconductor material are not unfavourably affected by the increase in temperature. So-called CCC capsules have been developed recently, i.e. capsules manufactured from ceramic material ("Ceramic-Circuit Carriers") which enclose the semiconductor wafer. CCC techniques permit a greater degree of packing than DIP capsules for example ("Dual-ln Package"), but the power (heat) generation is substantially the same, problems thus arising in respect of effectively cooling the system built up from such capsules.

It is previously known to cool an electronic system by a heavily forced airflow through channels in the system. This requires a given cleanliness of the airflow, since otherwise air can affect contacts, for example, and other sensitive elements, as will be seen from U.S. Patent 4,006,388, for example. It is also known to provide heavily dimensioned metallic conductors for heat conduction to one or more cooling flanges, as in U.S. Patent 3,991,346. This can mean that the weight of the system becomes unacceptably high when it is incorporated in airplane carried equipment, for example. The use of so-called heat tubes is also known, which conduct generated heat to cooling devices outside the system itself, the problem with contaminants in the airflow being thus eliminated as is described in U.S. Patent 3,631,325.Such cooling devices have a rather complicated 'structure and require increased space, however.

According to the present invention there is provided a cooling device for electronic components and/or circuit boards on which components are mounted, comprising a hermetically sealed space for containing a medium which, in use of the device, in a vapourization-condensation cycle, transfers heat from the components to a cooling location or a heat reception location, the space being provided by a cooling plate with a cooling flange member attached to the portion of the said plate which is uppermost in use of the device, the said member being provided with tapering flanges and having its interior formed with a cavity which tapers in a direction away from the plate (upwards in use of the device), wherein the cooling plate comprises first and second flat walls which are mutually substantially parallel, which contain at least one cavity in the form of channels from the upper portion of the plate to its lower portion, and sealing means for the channels at the lower part of the plate, the lower part of the said tapering cavity opening out into the said channels, and wherein the flanges project out on each side of the tapering cavity, with the flanges on one side being mutually offset from the flanges on the opposite side whereby flanges on each side can partially engage in spaces between flanges of an adjacent such cooling device.

The present invention will now be described by way of example with reference to the accompanying drawings, in which:~ Figure 1 illustrates a cooling device, partly in section; Figure 2 is a sectional view of a cooling plate included in the device of Figure 1; Figure 3 illustrates, partially in cross-section, a building module for ceramic plates in which a cooling device is included; Figure 4 is a sectional view of the module in Figure 3; and Figure 5 illustrates a closed cooling system with separately arranged cooling channels according to Figure 1.

Figure 1 illustrates a cooling device, partially in cross-section, containing a plurality of cooling channels 3 extending from top to bottom in the figure and which are defined by two substantially parallel walls 1 and 2 of metallic material, e.g.

extruded aluminium or copper. The design of the channels is best apparent from Figure 2, which is a section through A-A in Figure 1. As will be seen from Figure 2, the cooling channels comprise cavities 31-37, of which the cavities 31-33 form a group of cavities mutually in communication via narrow gaps. Between the groups 31-33 and 34-37 there is a strengthening portion 4 which forms a cross member to keep the two walls 1 and 2 together.

At given places along the portion 4 there are holes 8 (Figure 1) bored to enable attachment of components, circuit boards or other componentcarrying elements. A capillary material, e.g. glass fibre, is suitably arranged in intermediate cavities 32 and 35 along the height of the cooling device.

A cooling flange member 5 is attached to the upper edges of the two walls 1 and 2, joints 5a, Sb between member 5 and walls 1 and 2 being soldered by means of salt-bath soldering, which gives a good control of the tightness of the joints.

The cooling flange member 5 is made from extruded aluminium and is formed with flanges 51, 52, 53, 54 etc. In its interior there is a tapering cavity 6 the lower portion of which has a width equal to the major widths of the cooling channels. The flanges on one side are offset from the flanges on the other side so that a zig-zag type of profile is obtained, that is the flange 51 is offset from the flange 52, the flange 53 is offset from the flange 54, and so on. The object of this is that flanges of an adjacent (not shown) cooling device can mesh into the spaces between adjacent flanges, e.g. flanges 52, 54. An air gap will thus be formed between the flanges of two adjacent cooling nlange members, which gives great airflow speed due to its small width.

The lower openings of the cooling channels are closed by means of a sealing cover 7 having a Ushaped cross-section for example. There is thus obtained a hermetically sealed hollow space consisting of the cooling channels 31-33,34- 37 and the upper, tapering cavity 6 inside the cooling flange member.

As mentioned above, the holes 8 are intended forthe insertion of discrete electronic components or boards, e.g. ceramic circuit boards. In operation, the components or boards create heated portions on the cooling plates, and the generated heat is to be conducted away. The channels and cavities are hermetically sealed and filled with freon for this purpose. The freon is vaporized at the hot portions and is condensed at the cooling flange member, more specifically at the walls of the interior cavity 6. The liquid freon runs down through the cooling channels 31,33, 34, 36, 37 and all the other unillustrated "empty" channels. The liquid is sucked up by the capillary material in the channels 32, 35 and is thereby spread out over the whole surface of the two wall portions 1,2.The relationship between the quantities of liquid and gas, and pressure and temperature, are determined by supplied and dissipated heat. At room temperature and with no supplied heat the pressure is just over 1 atmosphere (ATA). If heat is supplied, the temperature and pressure will rise. For a supplied power of 100 W and cooling air at 250C, the pressure is calculated to be about 4 ATA, and the temperature at the cooling plate about 680C, and constant over the whole surface, i.e. there are no hot spots.

For certain profiles, a channel can be replaced by a homogeneous portion, and units such as power transistors can be screwed on, which thereby obtain very effective cooling.

Figure 3 illustrates in more detail how ceramic plates, carrying ceramic ("CCC") capsules, are fitted to the cooling device.

A parent board 10, made from a material such as an epoxy, is foldable along its middle and is large enough to cover the outer sides of the two walls 1 and 2 of the cooling device. There is a plurality of holes in the board 10 for ceramic plates 9, of which the upper ones, as illustrated in Figure 3, carry ceramic capsules 12 and 13.

Flexible flaps 111, 112, 113 of a foil of a material such as a polyimide, are associated with the board 10 and have soldering spots 14, 1 5 for connecting printed circuits in the foil to the ceramic capsules 12, 1 3.

Figure 4 is a cross-section through B-B in Figure 3. The ceramic plates 9 are laid on the outsides of the walls 1,2 and are kept in place by means of screwed fastenings 1 6, 1 7 and an intermediate fastening means 18 in a material such as polytetrafluoroethylene. The contacts of the circuit board 10 are attached to the flap 113, which has a certain amount of movement. The ceramic plates 9 are conventionally formed and of an optical size, with 'i5 layers of conductive print.

The cooling device is not necessarily built up as a plate consisting of cooling channel modules put together as illustrated in Figure 1.

In Figure 5 there is shown a cooling device made up from individual modules or channel sections 20-22, of which each has a single group of channels, e.g. 31-33 in accordance with Figure 2. The sections are soldered to the cooling flange member 5, as described above. The cavity 6 inside the cooling member 5 is closed off by means of blocks 23, each with a U-shaped cross section and with an upper portion 25 adapted to the width of the mouth of the cavity 6 to obtain good sealing. The lower parts of the sections 20-22 are connected by means of a longitudinal block 26, with a U-shaped cross section, where an upper portion 27 is soldered to the end edges of the channel sections. A plug 28 defines a cavity together with the interior surface of the block 26, this cavity being in communication with all the cavities in the sections 20 32. There is thus obtained a closed cooling system, which gives uniform cooling, for the circuit boards or components, which are attached in a suitable mode to the channel sections 20-22.

Claims

1. A cooling device for electronic components and/or circuit boards on which components are mounted, comprising a hermetically sealed space for containing a medium which, in use of the device, in a vapourization-condensation cycle, transfers heat from the components to a cooling location or a heat reception location, the space being provided by a cooling plate with a cooling flange member attached to the portion of the said plate which is uppermost in use of the device, the same member being provided with tapering flanges and having its interior formed with a cavity which tapers in a direction away from the plate (upwards in use of the device), wherein the cooling plate comprises first and second flat walls which are mutually substantially parallel, which contain at least one cavity in the form of channels from the upper portion of the plate to its lower portion, and sealing means for the channels at the lower part of the plate, the lower part of the said tapering cavity opening out into the said channels, and wherein the flanges project out on each side of the said tapering cavity, with the flanges on one side being mutually offset from the flanges on the opposite side whereby flanges on each side can partially engage in spaces between flanges of an adjacent such cooling device.

2. A cooling device as claimed in claim 1, wherein of the said channels, a certain number are in groups where the channels in a certain group are in mutual communication via gaps of smaller width.

3. A cooling device as claimed in claim 2, wherein at least one of the channels contains a capillary material for sucking up the condensed medium.

4. A cooling device as claimed in any of claims 1 to 3, wherein portions lying between the channel groups comprise strengthening members extending parallel to the said channels.

5. A cooling device, substantially in accordance with any example herein described with reference to the accompanying drawings.