WO2006136984A2

WO2006136984A2 - Thin film circuit connections

Info

Publication number: WO2006136984A2
Application number: PCT/IB2006/051920
Authority: WO
Inventors: Martin J. Edwards
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-06-21
Filing date: 2006-06-15
Publication date: 2006-12-28
Also published as: TW200705633A; WO2006136984A3

Abstract

An electronic device comprises a substrate (12) and thin film circuitry provided on the substrate and having a plurality of contact terminals (22) provided over the substrate. The thin film circuitry comprises at least first circuit elements (40). A connector foil arrangement (30) has a first foil portion (36) having conducting tracks (32) which connect to the contact terminals (22) and a second foil portion (38) which overlies the first circuit elements (40) of the thin film circuit. The second portion (38) has a conductor pad (42). This device uses a connector foil both to provide external connections to terminals of the thin film circuitry but also to overlie selected ones of the circuit elements. The conductor pad can be used for lower resistance connections, for heat dissipation purposes, or for electromagnetic shielding.

Description

DESCRIPTION

THIN FILM CIRCUIT CONNECTIONS

This invention relates to the formation of external connections to thin film circuits carried on a substrate. Particularly, but not exclusively, the invention relates to the formation of connections to thin film circuits provided on a substrate which also carries an active matrix array of thin film elements, and the thin film circuits are for addressing or other control of the array of elements.

The integration of circuit functions onto the substrates of active matrix devices is increasing as low temperature polysilicon technology allows high performance circuits to be formed on insulating substrates, such as glass or plastic. For example, in active matrix liquid crystal displays and active matrix LED displays, the row and column addressing circuits can be integrated onto the display substrates in order to produce lower cost, more compact and more robust displays.

In the future, it is expected that other circuit functions will be integrated, for example power supply circuits and amplifiers. In future, therefore, the electrical power dissipated within the circuits during normal operation may be significantly higher than at present.

The operation of thin film circuits formed on insulating substrates at these higher power levels results in significant heating of devices and components within the circuit and therefore of the surrounding materials including the substrate.

The resultant localised heating of the substrate can result in non- uniformity of the displayed images in the case of a display device or non- uniformity in the sensitivity of a sensing device. Excessive heating of the thin film devices or components may result in degradation of their properties and premature failure. In addition, operation of thin film circuits formed using large area electronics technology at higher power levels and increased current levels requires low resistance electrical connections to be made to the circuits in order to minimise power losses in the resistance of the connections. The metal layers conventionally used in large area electronics applications such as active matrix displays and sensors are relatively thin and therefore have a relatively high sheet resistance. This makes it difficult to make very low resistance electrical connections to circuits and between devices formed on the substrate. There are thus a number of problems associated with the integration of higher power circuitry onto the substrate carrying other thin film circuit elements, or indeed the formation of high power thin film circuits in general.

According to the invention, there is provided an electronic device, comprising: a substrate; thin film circuitry provided on the substrate and having a plurality of contact terminals provided over the substrate, the thin film circuitry comprising at least first circuit elements; a connector foil arrangement, comprising a first foil portion having conducting tracks which connect to the contact terminals and a second foil portion which overlies the first circuit elements of the thin film circuit and has a conductor pad.

This device uses a connector foil both to provide external connections to terminals of the thin film circuitry but also to overlie selected ones of the circuit elements. The conductor pad preferably has a greater width than the conducting tracks, and this enables it to be used for lower resistance connections, for heat dissipation purposes, or for electromagnetic shielding.

For example, the thin film circuitry may comprise first circuit elements and second circuit elements, and wherein the first circuit elements are heat generating circuit elements. The pad can then be used to dissipate heat from these elements, and can thus comprise a heat dissipation pad. The first and second foil portions can be part of the same foil, so that a single foil connection to the thin film circuitry substrate achieves multiple purposes.

The first and second foil portions can terminate along a common edge, and a notch can be provided between the first and second foil portions at the common edge. This provides a mechanical separation of the different foil portions.

In one example, the conductor pad can be electrically isolated from the first circuit elements, and then perform a heat dissipating function and/or an electromagnetic shielding function. An insulating layer and an adhesive layer are then provided between the first circuit elements and the second foil portion.

Alternatively, the conductor pad can comprise connection portions which provide internal connections between different circuit elements of the first circuit elements. These connections can be low resistance, both through choice of the materials on the foil and the dimensions of the pad or pads.

An insulating layer and a conductive adhesive layer can again be provided between the first circuit elements and the second foil portion, but vias through the insulator layer are provided to enable connection of the connection portions to the circuit elements. The conductor pad may further comprise heat dissipating portions.

The heat dissipating portions can also be used to connect to the circuit elements.

The device may further comprise a heat sink to which the conductor pad is connected, for example the device casing. The device may be an active matrix array device, comprising an array of thin film elements provided over the substrate, and the thin film circuitry provided on the substrate is then for the control of the thin film elements. These thin film elements may comprise display or sensor elements.

The invention also provides a method of connecting external circuitry to thin film circuitry provided on a substrate, the method comprising: making electrical connections between the external circuitry and a plurality of contact terminals provided over the substrate using conducting tracks of a first foil portion of a connector foil arrangement; and making internal electrical connections between circuit elements of the thin film circuitry using at least one conductor pad of a second foil portion of the connector foil arrangement which overlies the circuit elements.

The invention also provides a method of dissipating heat from thin film circuitry provided on a substrate, the method comprising: making electrical connections between external circuitry and a plurality of contact terminals provided over the substrate using conducting tracks of a first foil portion of a connector foil arrangement; and dissipating heat from circuit elements of the thin film circuitry using a conductor pad of a second foil portion of the connector foil arrangement which overlies the circuit elements. The invention also provides a method of providing electromagnetic shielding for thin film circuitry provided on a substrate, the method comprising: making electrical connections between external circuitry and a plurality of contact terminals provided over the substrate using conducting tracks of a first foil portion of a connector foil arrangement; and providing electromagnetic shielding for circuit elements of the thin film circuitry using a conductor pad of a second foil portion of the connector foil arrangement which overlies the circuit elements.

The invention also relates to the thin film circuit prepared for connection to the foil connector arrangement, and thus also provides an electronic device, comprising: a substrate; thin film circuitry provided on the substrate and having a plurality of contact terminals provided over the substrate, the thin film circuitry comprising at least first circuit elements; wherein the contact terminals are aligned adjacent an edge region of the substrate, and wherein the first circuit elements are arranged in a location in line with the line of contact terminals. The invention also relates to the foil connector arrangement, and thus also provides a connector foil arrangement for connection to thin film circuitry provided on a substrate, the connector foil arrangement comprising a first foil portion having conducting tracks for connection to contact terminals and a second foil portion comprising a conductor pad for overlying circuit elements of the thin film circuitry.

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a known thin film device with external electrical connections to the device using a connector foil;

Figure 2 shows the device of Figure 1 in cross section;

Figure 3 shows a first device of the invention in plan view;

Figure 4 shows the device of Figure 3 in cross section; Figure 5 shows a second device of the invention in plan view;

Figure 6 shows a third device of the invention in plan view;

Figure 7 shows the device of Figure 5 or 6 in cross section where no connections to the circuit elements are needed;

Figure 8 shows the device of Figure 5 or 6 in cross section where connections to the circuit elements are needed;

Figure 9 shows a fourth device of the invention in plan view;

Figure 10 shows a fifth device of the invention in side view;

Figure 11 is an example of circuit which may form first circuit elements of the circuitry in the devices of Figures 3 to 10; Figure 12 shows the thin film layout of the circuit of Figure 11 ;

Figure 13 shows how connections are made to the circuit of Figures 11 and 12 in accordance with the invention;

Figure 14 shows a first variation to the arrangement in Figure 13; and

Figure 15 shows a second variation to the arrangement in Figure 13.

The same reference numbers are used throughout the figures to refer to the same components. The invention provides an arrangement in which connector foils, comprising electrically and/or thermally conducting layers, are bonded to a substrate carrying thin film circuits so that part or all of the area occupied by the devices and components of the circuit is covered by the foil. This enables direct thermal or electrical connection to those devices or components which have a low electrical and/or thermal resistance. In this way, low resistance electrical connections can be made to the devices and components to improve circuit performance. Alternatively or additionally, heat can be transferred away from the devices and components. Alternatively or additionally, electromagnetic shielding can be provided.

In large area electronics applications such as active matrix displays and sensors, foils comprising metal layers carried on a flexible, insulating substrate are typically used to provide electrical connections between the large area electronics device and external electronic circuitry. Figure 1 illustrates an example of this known approach for an active matrix display device 10.

The display device 10 comprises a first substrate 12 which carries an array 14 of display pixels as well as column driver circuitry 16 and row driver circuitry 18. Additional circuitry 20 provides other functions, for example relating to timing, signal waveform generation, and power level generation.

External connections to the circuits are arranged as a linear array of terminals 22. These terminals are positioned along an edge 24 of the first substrate 12. A second substrate 13 is provided over the first substrate, and the liquid crystal layer is sandwiched between the two substrates. The second substrate 13 is provided over all of the area of the first substrate 12 other than the edge region 24, where connections need to be made to the array of terminals 22.

The connection is in the form of a flexible foil 30 which carries a metal layer patterned to form a number of conducting tracks 32 which carry signals between external circuits and the circuits 16,18,20 formed on the display substrate. These circuits use thin film devices and components, of the same technology type as the display pixels, for example polysilicon thin film transistors.

The foil 30 has contact regions 34 which are aligned with the terminals

22 on the display substrate. An anisotropic conducting adhesive is used to bond the foil 30 to the display substrate and to provide the electrical connection between the conductors on the foil and the corresponding conductors on the display substrate.

The known arrangement of the foils is further illustrated in Figure 2 which shows a cross section through the display and foil in the region where the electrical connections are made.

The invention provides a modification to the arrangement of the foil and the layout of the display (or other device) substrate, in order to allow circuits with improved performance to be integrated onto the substrate of the large area electronics device, in this example the display. Figure 3 shows a first example of device of the invention.

The connector foil has a first portion 36 provided with the tracks 32 and a second portion 38. This second portion is aligned with the first portion, and they share a common edge.

Part of the circuitry (referred to as "first circuit elements") is moved to a position under the second foil portion as shown at 40, so that the second foil portion 38 overlies the first circuit element. This foil portion 38 has a large area pad 42 rather than thin connection tracks, and this enables the pad to perform one or more of the functions of heat dissipation, low resistance interconnection and electromagnetic shielding. In one implementation, the first circuit elements moved to the location

40 are heat generating circuit elements, namely elements which require a degree of passive cooling. In another implementation, the circuit elements may be those requiring low resistance connections to be made either between themselves or to external control signals or driving voltages. In another implementation, the first circuit elements moved to the location 40 are circuit elements requiring electromagnetic shielding. These three approaches may also be combined. Electromagnetic shielding can be used to reduce electrical interference and electrical noise, by using the conducting pad on the foil as a ground plane to reduce radiation of electrical noise from circuits located beneath it on the substrate. An example of a possible circuit in this situation could be a high frequency oscillator circuit. Alternatively, electromagnetic shielding can be used to reduce the sensitivity of the circuits on the substrate to external sources of electrical interference. An example of a possible circuit in this situation could be a charge sensitive amplifier.

In the example of Figure 3, the pad 42 does not make electrical connection to the underlying circuit elements, and is simply a heat dissipation pad and/or an electromagnetic shielding pad.

The first and second foil portions 36, 38 can be part of the same foil, so that the single foil is used to provide connection of electrical power and control signals to the circuits on the substrate of the display, as well as the passive cooling. Little or no additional cost is thus incurred. However, there may be situations where the use of a separate foil is more appropriate.

Figure 4 shows the same arrangement in cross section. The circuits are located to one side of the conventional contact region, although other arrangements might also be appropriate. Although not shown in the schematic drawing of Figure 4, an increased overlap area can be formed between the circuits at the location 40 and the pad conductor on the foil in order to produce a low thermal resistance path between the two or to improve the electromagnetic shielding.

For the heat transfer example, heat is transferred from the circuits to the pad conductor on the foil. The area of the pad conductor on the foil away from the bond region can also be enlarged as shown in Figure 3 in order to promote transfer of heat to the environment through conduction, convection and radiation.

Figure 3 also shows a connection 44 from the pad conductor on the foil to the external circuits, and this can be used to connect the pad conductor 42 to a known potential, for example to form a ground plane for electromagnetic shielding. The conductive material on the foil forming the pad conductor 42 may be the same as that used to provide electrical conduction, namely the material of the tracks 32, and on the same side of the foil as those tracks, namely facing downwardly in Figure 3. Alternatively, a different material which is optimised for its thermal conduction properties or electromagnetic shielding properties might be used.

For example, it may be preferable to make use of a thicker layer of conducting material in this region than that used in the normal contact region in order to improve heat transfer. The adhesive used to bond the foil to the substrate may be the same in both contact regions or different adhesives may be used, one optimised for its electrical properties and the other, for example, for its thermal properties, for example the ability to withstand the stresses associated with temperature cycling. Figure 5 shows a modification to the example of Figure 4, in which the first and second foil portions terminate along a common edge, and a notch 50 is provided between the first and second foil portions at the common edge.

This mechanically isolates to some extent the high density terminal contact region of the foil from the area associated with heat transfer/electromagnetic shielding so as to avoid compromising the characteristics of the high density connections. Alternatively, separate foils can be used for the two regions to provide even greater isolation.

The examples of Figures 3 to 5 use the conducting pad 42 as a heat dissipating or electromagnetic shielding element. The conducting pad may be used to provide low resistance electrical connections to the circuits in addition to or instead of providing a means of removing heat from the circuits.

Figure 6 shows a further modification in which the conductive pad 42 is also used for making electrical connection to the underlying circuit elements and also to make internal electrical connections between the circuit elements. As shown, the pad 42 comprises two electrically separate regions

60,62, as well as an isolated link 64. The isolated link 64 enables low resistance interconnections to be made, and the regions 60,62 can connect to multiple points within the underlying circuitry.

This enables more than one signal to be provided to the circuit, and the different conductor regions enable this to be implemented. In the example of Figure 6, an interdigitated arrangement of the conductors is shown over the area of the circuit so that two different signals can be connected to different points within the area of the circuit. Where it is necessary to achieve a low connection resistance between devices or components within the circuit integrated on the substrate this can be achieved by forming the internal connections using the isolated link 64.

The thin film circuits formed on the display substrate will typically be covered by one or more insulating layers. This is illustrated in the more detailed cross section of the contact region shown in Figure 7. A single electrical insulation layer 70 is shown, and an adhesive layer 72. The adhesive layer may be able to conduct in the vertical direction, when compressed, so that conduction is possible between the foil conductors on the substrate. This conduction can be through conducting particles, with a relatively low density so that there is not conduction in the horizontal direction. These layers provide protection for the circuits, but must the insulating layer must be removed where electrical connections are to be made. The circuit elements are shown schematically as 73.

As illustrated in Figure 8 (not to scale), vias 80 are opened up through the insulating layer in order to provide electrical connections to the devices or nodes in the circuit. These connections can be formed in the same way as for the conventional signal connections by forming contact regions adjacent to the thin film devices within the circuit.

As shown in Figure 9, in order to improve the removal of heat from circuits on the display, the foil can be used as a means of transferring heat between the integrated circuitry and a heat sink 90, for example the metal case of the display module or a dedicated heat sink.

As shown in Figure 10, the second foil portion (at least) can be folded over to overlie both sides of the substrate. This further improves the transfer of heat away from the circuits integrated on the display substrate.

Figure 11 shows one example of a circuit which can be integrated onto a display substrate using low temperature polysilicon thin film transistors. The circuit has two input signals, Input A and Input B, and two output signals, Output A and Output B. An external load (not shown) is connected between the two output terminals, and the power supply voltage levels VDD and VSS for the circuit are supplied from external circuits. The circuit comprises four transistors T1 to T4. Figure 12 shows how the invention can be applied, and shows a possible layout for the circuit on the display substrate. For the transistor T3, drain connections D, gate connections G and source connections S are labeled. Each transistor T1 to T4 has the same basic layout, arranged as multiple parallel source and drain lines with gate lines interleaved between. The circuit has five contacts 120 on the substrate. The Output B is connected to the transistors at each end of the line of transistors (T3 and T4), and for this reason, two Output B contacts are provided. The circuit also has the two inputs provided to the gate lines G, and the topology shows four gates lines, one for each transistor. This configuration gives a low output resistance, by providing the transistors with a large width. The implementation of the transistors is in the form of a number of smaller devices which are connected in parallel and placed side by side with common drain connections, common gate connections and common source connections, and this gives a compact layout. The gate signals which are applied to the transistors can be generated by circuits which are also integrated on the display substrate.

Figure 13 shows the layout of the conductors on the foil which is bonded over the circuit. This drawing (and Figures 14 and 15) simply illustrates the principles of the technique and is not to scale. The positions of the contacts 120 are shown, and the conductor pad is configured to make a connection to each pad, as well as providing an internal connection 122 between the two Output B contacts. As mentioned above, one application of the invention is for low resistance connections and for heat dissipation. The manner in which these two objectives can be met in the layout of Figure 13 will now be discussed.

The low resistance connections are to achieve a low electrical resistance between the external signals and the devices forming the circuit on the display substrate, and/or between internal nodes of the circuit on the display substrate. The low resistance can be obtained by locating contacts to the conductors on the foil as close as possible to the source and drain terminals of the transistors. In this example circuit, this can be achieved by locating the transistors between the contact areas 120 which are formed on the display substrate. Corresponding contact regions are formed in the conductors on the foil as can be seen in Figure 13. Low resistance connections between conductors are formed by opening windows through the insulating layers overlying the circuits and by bonding the foil to the display substrate using a conducting adhesive in a conventional manner. In principle, it is possible to form the contact regions over the top of the transistors to produce a more compact layout (for example using a third pixel metal layer) although there is a risk that the bonding process could result in damage to the transistors below. Figure 13 shows a connection 122 between the drain terminal of T3 and the drain terminal of T4, which is required in order to form the circuit node Output B. This connection could of course be achieved by forming a conducting path between the transistors on the display substrate. However, the use of the foil enables the resistance of this connection to be low compared to the output resistance of the circuit. To achieve this with a conductor on the display substrate could require a very wide signal line. The foil conductor will have a much lower sheet resistance than the conductors formed on the display substrate.

In the example circuit, heat would be generated within the transistors T1 to T4, and the configuration of the invention can enable transfer of heat from those circuit elements. Some heat will be transferred to the conductors on the foil via the contacts at the source and drain terminals. However, the heat transfer can be improved further by extending the conductors on the foil over the transistors.

Figure 14 shows in more detail that the arrangement of Figure 13 provides heat dissipation using the VDD and VSS conductor pads, which overlie the four banks of transistors 140. In Figure 14, the combination of the foil conductor pattern and the circuit layout on the display substrate is illustrated.

It will not always be desirable to cover the circuit in this way, as the capacitance between the circuit and the conductors on the foil may degrade the circuit performance. If sufficient heat transfer can be obtained from the contacts 120 alone, and the main requirement is to achieve connections with a low electrical resistance, then the layout of the foil conductors shown in Figure

15 may be preferred, in which the conductor pad portions do not overlie the transistors. The invention is applicable to any thin film circuits formed on insulating substrates and is of particular relevance to large area electronics applications including displays and sensors.

The circuit described above is of course only one example of thin film circuit which can be positioned under the connection foil, and this example concentrates on heat dissipation and electrical connection resistance rather than electromagnetic shielding. Circuit elements other than transistors may require cooling and/or low resistance connections and/or electromagnetic shielding.

The pad or pad portions used to provide low resistance connections and/or heat dissipation and/or shielding will be designed according to the desired characteristics. Typically, each pad portion will have a greater width than the width of each normal connection track. However, this is not necessarily the case, as internal connections with a low resistance may be possible with narrow width tracks, if the tracks have low sheet resistance and/or large thickness. Indeed, the materials and thickness used can be tailored to provide the desired electrical and/or thermal conduction properties. The invention has been described in detail in connection with a display, in which an array of display pixels is formed using the same technology as the circuits which are overlapped by the connection foil. As mentioned above, the same considerations apply to sensor devices, but also to other array devices. Furthermore, the invention can be applied to thin film circuits generally, and is not restricted to a circuit carrying an array of device elements. An array of device elements is one example where multiple connections need to be made to the substrate and where a foil can be used for this purpose. However, there are other circuit designs in which a connection to the circuit using a foil is appropriate or possible, thereby enabling the benefits of the invention to be obtained.

Various other modifications will be apparent to those skilled in the art.

Claims

1. An electronic device, comprising: a substrate (12); thin film circuitry provided on the substrate and having a plurality of contact terminals (22) provided over the substrate, the thin film circuitry comprising at least first circuit elements (40); a connector foil arrangement (30), comprising a first foil portion (36) having conducting tracks (32) which connect to the contact terminals (22) and a second foil portion (38) which overlies the first circuit elements (40) of the thin film circuit and has a conductor pad (42).

2. A device as claimed in claim 1 , wherein the thin film circuitry comprises first circuit elements (40) and second circuit elements (20), and wherein the first circuit elements (40) are heat generating circuit elements.

3. A device as claimed in claim 1 or 2, wherein the conductor pad (42) of the second foil portion comprises a heat dissipation pad.

4. A device as claimed in any preceding claim, wherein the first and second foil portions (36,38) are part of the same foil.

5. A device as claimed in claim 4, wherein the first and second foil portions (36,38) terminate along a common edge, and a notch (50) is provided between the first and second foil portions at the common edge.

6. A device as claimed in any preceding claim, wherein the conductor pad (42) is electrically isolated from the first circuit elements (40).

7. A device as claimed in claim 6, wherein an insulating layer (70) and an adhesive layer (72) are provided between the first circuit elements (40) and the second foil portion.

8. A device as claimed in any one of claims 1 to 5, wherein the conductor pad (42) comprises connection portions (64) which provide internal connections between different circuit elements of the first circuit elements (40).

9. A device as claimed in claim 8, wherein an insulating layer (70) and a conductive adhesive layer (72) are provided between the first circuit elements (40) and the second foil portion (38), and wherein vias (80) through the insulating layer are provided to enable connection of the connection portions to the circuit elements.

10. A device as claimed in claim 8 or 9, wherein the conductor pad further comprises heat dissipating portions.

11. A device as claimed in claim 10, wherein the heat dissipating portions provide external electrical connections to different circuit elements of the first circuit elements.

12. A device as claimed in any preceding claim, further comprising a heat sink (90) to which the conductor pad (42) is connected.

13. A device as claimed in claim 12, wherein the heat sink comprises a device casing.

14. A device as claimed in any preceding claim, wherein the second foil portion (38) is folded over to overlie both sides of the substrate (12).

15. A device as claimed in any preceding claim, further comprising an array (14) of thin film elements provided over the substrate, and wherein the thin film circuitry provided on the substrate is for the control of the thin film elements.

16. A device as claimed in claim 15, wherein the thin film elements comprise display elements.

17. A method of connecting external circuitry to thin film circuitry provided on a substrate, the method comprising: making electrical connections between the external circuitry and a plurality of contact terminals (22) provided over the substrate (12) using conducting tracks (32) of a first foil portion (36) of a connector foil arrangement; and making internal electrical connections between circuit elements (40) of the thin film circuitry using at least one conductor pad (42) of a second foil portion (38) of the connector foil arrangement (30) which overlies the circuit elements (40).

18. A method of dissipating heat from thin film circuitry provided on a substrate, the method comprising: making electrical connections between external circuitry and a plurality of contact terminals (22) provided over the substrate (12) using conducting tracks (32) of a first foil portion (36) of a connector foil arrangement; and dissipating heat from circuit elements of the thin film circuitry using a conductor pad (42) of a second foil portion (38) of the connector foil arrangement (30) which overlies the circuit elements (40).

19. A method of providing electromagnetic shielding for thin film circuitry provided on a substrate, the method comprising: making electrical connections between external circuitry and a plurality of contact terminals (22) provided over the substrate (12) using conducting tracks (32) of a first foil portion (36) of a connector foil arrangement; and providing electromagnetic shielding for circuit elements (40) of the thin film circuitry using a conductor pad (42) of a second foil portion of the connector foil arrangement (30) which overlies the circuit elements (40).

20. An electronic device, comprising: a substrate (12); thin film circuitry provided on the substrate and having a plurality of contact terminals (22) provided over the substrate, the thin film circuitry comprising at least first circuit elements (40); wherein the contact terminals (22) are aligned adjacent an edge region of the substrate, and wherein the first circuit elements (40) are arranged in a location in line with the line of contact terminals (22).

21. A device as claimed in claim 20, wherein the thin film circuitry comprises first circuit elements (40) and second circuit elements (20), wherein the first circuit elements (40) are heat generating circuit elements.

22. A device as claimed in claim 21 , wherein the second circuit elements (20) are arranged in a location further away from the edge region of the substrate than the first circuit elements and the contact terminals.

23. A connector foil arrangement for connection to thin film circuitry provided on a substrate, the connector foil arrangement comprising a first foil portion (36) having conducting tracks (32) for connection to contact terminals (22) and a second foil portion (38) comprising a conductor pad (42) for overlying circuit elements (40) of the thin film circuitry.

24. An arrangement as claimed in claim 23, wherein the conductor pad (42) comprises a heat dissipating pad.

25. An arrangement as claimed in claim 23 or 24, wherein the conductor pad (42) comprises an internal connection pad for the circuit elements of the thin film circuitry.

26. An arrangement as claimed in claim 23, 24 or 25, wherein the conductor pad (42) comprises an electromagnetic shielding pad.