GB2256540A

GB2256540A - Electrical device.

Info

Publication number: GB2256540A
Application number: GB9112254A
Authority: GB
Inventors: Alan Raymond Moore
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1991-06-07
Filing date: 1991-06-07
Publication date: 1992-12-09
Anticipated expiration: 2011-06-07
Also published as: GB9112254D0; GB2256540B

Abstract

An electrical device and a method of manufacturing the device, the electrical device comprising a support structure including a moulded synthetic resin support (11), a circuit element (27, 28, 29) supported by said support structure, a plurality of electrical terminals (14B, 15B) carried by the support structure and a flexible printed circuit conductor array (16, 17, 18) embedded in the support moulding (11) and providing electrical connections between said terminals (14B, 15B) and said circuit element (27, 28, 29). A cover (19) and apertured heat sink (23) complete the support structure. <IMAGE>

Description

ELECTRICAL DEVICE This invention relates to an electrical device of the kind wherein a moulded synthetic resin support has embedded therein electrical conductors which provide electrical connections between terminals carried by the support and a circuit element such, for example as a printed circuit board or a thick film circuit mounted on the support.

The conventional method of producing an electrical device of the kind specified is to mould the support around a sheet metal fret defining the conductors. The fret is stamped from metal sheet and contains the conductors and integral bridges interconnecting the conductors so that the fret can be handled as a single component. The bridges are cut away after moulding to electrically separate the conductors as necessary.

Generally the fret also defines a plurality of terminal pins which are exposed at a surface of the moulding to permit external connections to be made to the conductors.

After the bridges of the fret have been removed the circuit element is mounted on the moulded support and electrical connections are produced as necessary between the circuit element and appropriate parts of the conductors protruding from the support moulding.

The known technique is disadvantageous in a number of respects. For example, a substantial amount of material is wasted in the production of the fret, and the thickness of the fret is chosen to accommodate the physical and electrical constraints imposed upon the terminal pins and also to accommodate the requirements of the conductor of the fret which in use is to carry the highest electrical current. Thus although some of the conductors of the fret may carry only signal currents they would nevertheless be formed from material the thickness of which is chosen to suit conductors which are to carry power current. Complex conductor arrangements may necessitate the use of more than one fret and/or the use of jumper connections between conductors within the same or different frets.Such jumper connectors must be attached after manufacture of the fret, and thus do not lie in the plane of the fret. These factors may in turn necessitate moulding the support in two or more stages to ensure that the frets are held in appropriate locations relative to one another, and to ensure also that jumper connections are not distorted, with the attendant risk of short circuiting, during the moulding process. When the support has been moulded there is then the need to remove the bridges between the conductors of the or each fret electrically to isolate the conductors as necessary.

Certain conductors may need to be shaped to provide resilient sinuous connection regions to accommodate differential thermal expansion of the conductor and the circuit element or alternatively may require to be connected to the circuit element by way of a flexible wire. It is an object of the present invention to provide an electrical device, and a method of manufacturing an electrical device wherein the aforementioned disadvantages are minimised.

In accordance with the present invention there is provided an electrical device comprising a support structure including a moulded synthetic resin support, a circuit element supported by said support structure, a plurality of electrical terminals carried by the support structure and a flexible printed circuit conductor array embedded in the support moulding and providing electrical connections between said terminals and said circuit element.

In accordance with a further aspect of the present invention there is provided a method of manufacturing an electrical device comprising effecting electrical connection between a plurality of electrical terminals and respective conductors of a flexible printed circuit conductor array, introducing said array into a mould, moulding a synthetic resin support within which parts of said array are embedded, mounting a circuit element in relation to said moulded synthetic resin support, and effecting appropriate electrical connections between conductors of said array and said circuit element.

The term flexible printed circuit conductor array" is used herein to mean a flexible element including a predetermined pattern of flexible electrical conductors supported by at least one flexible synthetic resin sheet. Conveniently the conductor array will be sandwiched between two flexible synthetic resin sheets with an aperture or apertures appropriately positioned to permit electrical connection to be made to the conductors.

One example of the invention is illustrated in the accompanying drawings wherein: Figure 1 is an exploded perspective view of an electronic unit for use in an automobile electrical system, and Figure 2 is an enlarged, diagrammatic, cross sectional view of part of the unit illustrated in Figure 1.

Referring to the drawings the unit comprises a moulded synthetic resin support 11 generally in the form of a rectangular frame defining within it first and second rectangular windows 12, 13. The support 11 is moulded around first and second plug units 14, 15 and first, second and third flexible printed circuit conductor arrays 16, 17, 18. The plug unit 14 comprises moulded synthetic resin body 14A housing a plurality of metal blade terminals 14B. At one end the plate terminals 14B project into a recess of the body 14A to receive an external electrical connector, and at their opposite end the blade terminals 14B protrude from the base of the body 14A and are connected to the flexible printed circuit conductor array 16. Each terminal 14B is electrically connected to a predetermined respective conductor of the array 16, the unit 14 and the array 16 comprising a sub-assembly.The plug unit 15 is comparable with the plug unit 14 although of course its shape and the number of its terminals 15B may differ. The terminals 15B of the plug unit 15 are similarly connected to conductors of the array 18 the plug unit 15 and the array 18 defining a second sub-assembly.

Prior to moulding of the support 11 the subassembly 14, 16, the sub-assembly 15, 18, and the array 17 are introduced into the mould which defines the shape of the support 11 and the support 11 is then moulded around the sub-assemblies and the array 17 so that parts of the plug units 14, 15 and parts of the arrays 15, 17, 18 are embedded in the material of the support 11. The end of the array 16 remote from the unit 14 and one end of the array 17 project, co-planar with one another, into the window 12 and the opposite end of the array 17 and the end of the array 18 remote from the unit 15 project similarly into the window 13 of the support 11. A top cover 19, conveniently formed from electrically insulating synthetic resin material, is shaped to overlie the top surface of the support 11 thereby closing the windows 12, 13. The cover 19 has an aperture 21 through which the body of the plug unit 15 projects and a hollow chimney 22 into which the body 14A of the unit 14 extends. It will be recognised therefore that the terminals 14B, 15B are accessible at the upper face of the device.

Engagable with the lower face of the support 11 is a die-cast base or heat sink 23. The upper face of the base 23 contains three rectangular pockets 24, 25, 26 for receiving respective electrical and/or electronic circuit element 27, 28, 29 respectively. When the circuit elements 27-29 are positioned in the pockets 24-26 and the base 23 is engaged with the lower face of the support 11 then the parts of the arrays 16, 17, 18 protruding from the moulded support 11 overlie predetermined connection areas of the circuit elements 27, 28, 29 respectively.Thus after engagement of the base 23 with the support 11, and before positioning of the cover 19 the conductors of the arrays 16, 17, 18 can be electrically connected with appropriate terminal pads or conductors of the circuit elements 27, 28, 29 for example by soldering, so that appropriate electrical connections are made between the terminals 14B, 15B and the electrical circuits of the elements 27, 28, 29 by way of the arrays 16 and 18, the array 17 effecting electrical interconnections between the circuit element 29 and the circuit elements 27 and 28.

It will be understood that although in the example described above the flexible printed circuit conductor array 17 does not connect directly to either of the sets of terminals 14B, 15B, there may be applications in which in addition to providing interconnections between circuit elements the array 17 or an equivalent array provides direct electrical connections between circuit elements and terminals. Thus using the arrangement illustrated in Figure 1 as an example it will be recognised that the array 18 is generally L-shaped having one limb which extends within, and protrudes from one side part of the support 11, and a second limb which lies beneath the plug unit 15 with its conductors connected to respective terminals 15B.Where the array 17 is to be directly connected to certain of the terminals 15B then the array 17 can also be of L-shaped configuration having one limb also lying beneath the plug unit 15 to facilitate connection of appropriate conductors to respective terminals 15B and a second limb which is embedded within, and protrudes at both sides from, the integral cross member of the moulded support 11. It will be understood that a single array of conductors can provide connections between one or more sets of terminals and one or more circuit elements.

It will be recognised that the circuit elements of the electrical or electronic device can take a wide variety of different forms. For example, they can be relatively simple, rigid printed circuit boards having conventional wire ended components mounted thereon; they can be more complex rigid printed circuit boards having surface mounted components thereon; or rigid circuit elements of the ceramic tile type having surface mounted components connected to conductors and resistors printed on the tile.

Similarly the flexible printed circuit arrays may take a number of different forms, and of course their shape and conductor pattern will be determined by the connections to be made. Convenient flexible printed circuit conductor arrays are of the type wherein thin metallic foil conductors are supported and electrically insulated from each other and the surrounding environment by being sandwiched between two sheets of flexible synthetic resin material. The two sheets are adhesively bonded, or welded together, between the conductors, and one or both sheets have one or more appropriately positioned apertures through which conductors are exposed for electrical connection to the terminals and the circuit elements.The conductors of the arrays can have solder pads bonded thereto to permit them to be soldered readily to the circuit elements, or can be apertured to receive connection pins, or can have combinations of these and other known termination methods. There may be applications in which it is convenient to alter the assembly sequence described above, for example by moulding the support around the array before connecting the terminals of the or each plug unit to the conductors of the array.

It will be recognised that by comparison with the conventional fret connection method the use of flexible printed circuit conductor arrays permits a much higher conductor density to be achieved within the same space constraints, and furthermore complex conductor patterns are much less problematic to produce. Thus the use of jumper connections between conductors of a fret can largely be avoided, and, since the arrays are selfsupporting units it is unlikely that multi-stage moulding techniques will be needed in the production of the support 11. Furthermore, since the conductors of the flexible printed circuit array are electrically insulated by their synthetic resin carrier sheet arrays can be positioned on top of the other without the risk of short circuiting thereby permitting the routing of large numbers of connections in a restricted space. The inherent flexibility of the conductors readily accommodates the effects of differential thermal expansion and so avoids the need for special treatment of the regions of connection to the circuit elements.

Claims

1. An electrical device comprising a support structure including a moulded synthetic resin support, a circuit element supported by said support structure, a plurality of electrical terminals carried by the support structure and a flexible printed circuit conductor array embedded in the support moulding and providing electrical connections between said terminals and said circuit element.

2. An electrical device as claimed in Claim 1, in which the conductor array is sandwiched between two flexible synthetic resin sheets with at least one aperture positioned to permit electrical connection to the conductors of the conductor array.

3. An electrical device as claimed in Claim 1 or Claim 2, in which the support moulding is moulded around at least one plug unit including said terminals.

4. An electrical device as claimed in any one of the preceding claims, in which the support structure defines an opening.

5. An electrical device as claimed in any one of the preceding claims, in which the circuit element comprises a rigid printed circuit board having components mounted thereon.

6. An electrical device as claimed in any one of Claims 1 to 4, in which the circuit element comprises a ceramic tile type element having surface mounted components connected thereto.

7. An electrical device as claimed in any one of the preceding claims, in which, in use, the circuit element is positioned within a pocket formed in a base arranged to engage with the lower surface of the support structure.

8. An electrical device as claimed in Claim 7, in which the base is arranged to act as a heat sink.

9. A method of manufacturing an electrical device comprising effecting electrical connection between a plurality of electrical terminals and respective conductors of a flexible printed circuit conductor array, introducing said array into a mould, moulding a synthetic resin support within which parts of said array are embedded, mounting a circuit element in relation to said moulded synthetic resin support, and effecting appropriate electrical connections between conductors of said array and said circuit element.

10. A method as claimed in Claim 9, in which the conductor array is sandwiched between two flexible synthetic resin sheets with an aperture or apertures appropriately positioned to permit electrical connection to be made to the conductors of the conductor array.

11. An electrical device substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of manufacturing an electrical device substantially as hereinbefore described.