GB2382932A

GB2382932A - Apertured printed circuit board for cooling air flow

Info

Publication number: GB2382932A
Application number: GB0228207A
Authority: GB
Inventors: Paul Newman; Edward Stradling
Original assignee: Semikron Ltd
Current assignee: Semikron Ltd
Priority date: 2001-12-05
Filing date: 2002-12-04
Publication date: 2003-06-11
Anticipated expiration: 2022-12-04
Also published as: GB0129042D0; GB2382932B; GB0228207D0

Abstract

A printed circuit board is provided with at least one hole 11,12,13 therethrough for the passage of cooling air. The PCB is particularly applicable to an installation in which boards are mounted in units (3, Fig 1) within a main housing (4), each unit having its own housing (6). The holes in the PCB are large enough to allow adequate air flow within the individual housing while still maintaining a back pressure to ensure that air flows to the other PCBs inthe installation.

Description

AIR FLOW COOLING CONTROL This invention relates to arrangements for and apparatus for air flow cooling of apparatus that generates undesired heat during its usage.

It is a common present day practice to produce electric/electronic apparatus which incorporates a number of components operationally provided upon or in operational relation to printed circuit boards. Generally such printed circuit boards and the associated components are enclosed in an appropriate housing to prevent damage to the boards and the components. In practice the amount of heat is related to the current consumption of the components mounted to the board.

! Since heat is produced it follows that arrangements need to be provided to ensure that excessive or overheating does not occur even thought the apparatus may be operational for long periods of time.

In many cases particularly for a single piece of apparatus adequate cooling can be achieved by reason of the freedom by which air is able to circulate with respect to the printed circuit board and any components mounted thereupon. Such cooling can be aided by the provision of heat sinks specifically associated with those components that are prone to the generate of significant amounts of heat and thus very likely to result in overheating damage.

Whilst in the case of a single electrical/electronic unit, as suggested, adequate cooling can be adequately achieved it has been found that cooling difficulties can arise when the apparatus in question comprises two or more individual units each involving a printed circuit board and components mounted thereupon and as is usually the case each unit is contained in its own housing, with all of the individual units housed in a larger outer supporting rack and housing assembly.

Such an arrangement can arise such as, for example, in relation to a complex lighting system switchboard arrangement in which for example some forty eight individual lights control units are rack mounted with each such individual unit involving a printed circuit board and associated components located within a local housing. In addition to the individual housings the rack and the individual light control units would be at least partially enclosed, particularly in those regions where electrical connections are made between the any equipment provided upon the rack to and the vanous light control units.

It has been found that the overall effect of the use of what is effectively a double housing arrangement is to restrict the flow of cooling air around the various light controls units and particularly within the housings of the latter. Furthermore, even in situations where arrangements are provided for producing a forced air flow through out the rack housing and these arrangements are of such nature as to intend to distribute a balanced supply of air to each of the individual unit the provision of printed circuit boards within the individual unit housings, in so far as the air flow is concerned, has been found effectively to act as a banner to air flow within the individual housings and as a result upsetting the balancing of air flows necessary to ensure adequate distribution of air through out the complete assembly and through each unit.

It is an object of the present invention to at least reduce the risk of insufficient air flow through the installation and individual units.

According to a first aspect of the invention there is provided a method of facilitating the cooling of printed circuit boards involved in an installation including a plurality of the individual electronic circuit units each including at least one printed circuit board, wherein the printed circuit boards are especially apertured to allow the passage of air there through thereby to prevent the printed

circuit board acting as a total block to air flow from one side of the board to the other.

Preferably the areal size of the apertures in the printed circuit boards are so selected that the air flow through any one unit is such as to ensure the air flow relative to any one unit does not reduce the air pressure to an extent that air flows through other units becomes inadequate.

A further aspect of the invention provides a method of controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barner to air flow of air through the associated individual housing, including the step of providing at least one aperture within the printed circuit board of such aril size as to allow adequate flow of air through the individual housing whilst at the same time maintaining a back pressure in the installation sufficient to ensure that the air pressure of the flow of air remains sufficient to flow through all of the other printed circuit boards included in the installation..

A further aspect of the invention provides apparatus for controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barrier to air flow of air through the associated individual housing, including a printed circuit board having at least one aperture therein of such areal size as to allow adequate flow of air through the individual housing whilst at the same time maintaining a back pressure in the installation sufficient to ensure that the air pressure of the flow of air remains sufficient to flow through all of the other printed circuit boards included in the installation.

According to a further aspect of the invention there is provided a printed circuit board including at least one aperture therein that is not associated with aperture required for receiving any element of electrical wiring, for mounting the board to a support or for mounting a component to the board any circuit arrangements provided upon the board, the aperture being of such dimentsions as to facilitate the flow of cooling air with respect to the printed circuit board.

For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawings in which: Figure I is an oblique fragmentary view of an electrical/electronic installation including a plurality of rack mounted units within a housing; Figure 2 illustrates a first embodiment of a printed circuit board incorporating the concepts of the invention and; Figure 3 illustrates a second embodiment of a printed circuit board incorporating the concepts of the invention.

Referring now to Figure I the installation I shown therein includes a rack framing arrangement 2 mounting a plurality of rows and columns of individual electrical/electronic circuit units 3. In practice the units 3 can be of the plug-in type in that they are adapted to plug into associated electrical connections provided as part of the rack framing arrangement 2. In practice, at least this part of the arrangement 2 is totally enclosed by a housing 4, the latter being shown part cut away in the Figure 1. To provide for forced air cooling of the installation a fan unit 5 is associated with the housing 4. The air introduced by the fan unit 5 distributes throughout the interior of the housing.

Each one of the individual units 3 is shown as including a rectangular block like housing 6. Each unit housing is provided with a number of openings 7 to allow air produced by the fan 5 to be introduced into the units. In the case of two of the units the housings are shown part cutaway to reveal the interior of the associated units. Each unit 3 incorporates a printed circuit board 8 which effectively divides the interior of the unit housing into two separate sections 9 and 10, of which the section 9 is in that part of the housing 6 having the apertures 7 whereby this part of the housing can receive the air being circulated by the fan unit 5. Whilst it might be possible for air to circulate through various apertures as a result of the design of the circuitry of the printed circuit board. This possibility is usually remote since any holes provided in a printed circuit board are normally intended to be location holes for receiving locating screws or connecting elements of components to be mounted to the boards. In practice any residual gaps/spaces offer very limited space for air flows. It will thus be apparent that by and large the board effectively acts as an effective barrier to air flows that are essential to the operational safety of the boards and any associated circuit components mounted thereupon To counteract this problem the printed circuit boards are especially apertured to provide openings 11,12 and 13, as is illustrated in the Figures 2 and 3. It should be mentioned that the remaining apertures depicted on the Figures 2 and 3 are those associated with the mounting of the board to its associated support apparatus/chassis and/or components or the like to be upon the printed circuit board and would in use be effectively closed against air flow there through.

The dimensional size and the number of the apertures such as apertures 11, 12 and 13 are such that the flow of air there through is effectively set to a level which is such that the air flow through any printed circuit board irrespective of the positioning of its associated unit is constrained to be at a flow rate that, whilst

allowing an adequate air flow for cooling purposes, is of a magnitude which ensures that all of the units 3 are able to receive an adequate supply of air.

Referring in particular to the Figures 2 and 3 it will be noted that the dimensions of the apertures 11, 12, and 13 of Figure 2 differ from the corresponding apertures of Figure 3.

Whilst the Figures 2 and 3 illustrate differently dimensioned apertures it should be appreciated that in some installations it is possible to provide the same sized apertures Il, 12 and 13 for all of the printed circuit board units involved.

Furthermore, whilst the Figures 2 and 3 have illustrated the same number of apertures for the printed circuit boards the numbers of apertures provided can differ by providing printed circuit boards with more or less than three apertures Also the apertures can be other than rectangular or mixtures of different shapes,

Claims

1. A method of facilitating the cooling of printed circuit boards involved in an installation including a plurality of the individual electronic circuit units each including at least one printed circuit board, wherein the printed circuit boards are especially apertured to allow the passage of air there through thereby to prevent the printed circuit board acting as a total block to air flow from one side of the board to the other.

2. A method as claimed in claim !, in which the areal size of the apertures in the printed circuit boards are so selected that the air flow through any one unit is such as to ensure the air flow relative to any one unit does not reduce the air pressure to an extent that air flows through other units becomes inadequate.

3. A method of controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barrier to air flow of air through the associated individual housing, including the step of providing at least one aperture within the printed circuit board of such aril size as to allow adequate flow of air through the individual housing whilst at the same time maintaining a back pressure in theinstallation sufficient to ensure that the air pressure of the flow of air remains sufficient to flow through all of the other printed circuit boards included in the installation..

4. A method as claimed in claim 3, and in which at least two apertures presenting the a similar area to a flow of air.

5. A method as claimed in claim 3, and in which differently dimensioned apertures are provided in the printed circuit board

6. A method as claimed in claim 4 or 5 and in which differently shaped apertures are provided in the printed circuit boards.

7. A method of controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barrier to air flow of air through the associated individual housing, substantially as herein before described with reference to the accompanying drawings.

8. Apparatus for controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barrier to air flow of air through the associated individual housing, including a printed circuit board having at least one aperture therein of such areal size as to allow adequate flow of air through the individual housing whilst at the same time maintaining a back pressure in the installation sufficient to ensure that the air pressure of the flow of air remains sufficient to flow through all of the other printed circuit boards Included in the installation.

9. An installation including at least one unit incorporating at least one printed circuit board, wherein at least selected ones of the printed circuit boards associated therewith include at least one aperture therein that is not associated with any apertures required for receiving any element of electrical wiring, for mounting the board to a support or for mounting a component to the board any circuit arrangements provided upon the board, the aperture being of such

dimentsions as to facilitate the flow of cooling air with respect to the printed circuit board.

10. An installation as claimed in claim 9, and wherein the board includes at least two differently dimensioned apertures.

11. An installation board as claimed in claim 9, and wherein the board has at least two apertures of different dimensions and/or shapes.

12. An installation incorporating a method of controlling a forced flow of air within an installation incorporating a main housing at least partially enclosing a plurality separate units each including a printed circuit board located within its own individual housing and each effectively acting as a barrier to air flow of air through the associated individual housing substantially as herein before described with reference to the accompanying drawings.

13. A printed circuit board including at least one aperture therein that is not associated with aperture required for receiving any element of electrical wiring, for mounting the board to a support or for mounting a component to the board any circuit arrangements provided upon the board, the aperture being of such dimentsions as to facilitate the flow of cooling air with respect to the printed circuit board.

14. A printed circuit board as claimed in claim 13, and wherein the board includes at least two differently dimensioned apertures.

15. A printed circuit board as claimed in claim 13, and wherein the board has at least two apertures of different dimensions and/or shapes.

16. A printed circuit board, constructed and arranged to operate substantially as herein before described with reference to the accompanying drawings.