JPH0320052A - Chip carrier - Google Patents

Abstract

PURPOSE:To enable metallic wiring to be fined and to obtain enough finger strength by forming the inner lead part of metallic wiring on a flexible fin member. CONSTITUTION:The whole inner lead part 1a of metallic wiring 1 is formed on a flexible film member 2. That is, the inner lead part 1a is supported and reinforced up to the top by the flexible film member 2, so even if the thickness of the metallic wiring 1 itself is decreased, it can withstand heating, pressure, etc., in a bonding process enough in the meaning of strength. Hereby, the metallic wiring 1 can be thinned without lowering finger strength, and superfining of metallic wiring of the metallic wiring becomes possible.

Description

[Detailed Description of the Invention] [Field of Application in Industry] The present invention provides a method for using the terminal portion of a semiconductor chip such as an IC or LSI.
It relates to chip carriers used when connecting to external containers (so-called packages) or terminals of circuit boards. [Prior Art] Conventionally, a plurality of #IIM pads or punch portions of a semiconductor device chip are connected to a lead frame by a bonding wire or a lead wire C formed on a tape-shaped or patch-type film chip carrier. Or it was connected to the terminal section of the circuit board. Here, the classification of bonding wires and film chip carriers depends on the pitch between the bumps of the semiconductor device chip. For example, when the pitch is 200 to 300 uI1 or less, film chip carriers are generally used. be. Conventional film chip carriers use polyimide film. A device hole for inserting a semiconductor device chip is formed in an electrically insulating flexible film made of polyester film or the like, and at the periphery of the opening of the device hole on one side of the flexible film, A large number of metal wires (lead wires) with inner leads protruding radially from the device opening are formed. The inner lead of this lead wire protrudes over the opening of the device hole, and when a semiconductor device chip is inserted into the device hole, the inner lead part and the bump of the semiconductor device chip are connected to each other. is pressure bonded. Incidentally, in recent years, there has been a remarkable trend towards higher integration of semiconductor device chips, and as a result, the number of input/output connection pads has also increased, and semiconductor device chips with a bump-to-bump pitch of less than 100 μ field are now at the stage of practical application. ing.

However, it is extremely difficult to fabricate a film chip carrier with inner lead portions with a fine pitch that can accommodate semiconductor device chips with such a very narrow pitch between bumps. That is, the general method for forming the metal wiring of a chip carrier is to deposit a copper foil of about 35 μm thick on a flexible film member by vapor deposition or the like, or to attach a piece of copper foil to the flexible film member, and then to etch this copper foil. Alternatively, a catalytic active layer for electroless plating is provided on the surface of the flexible film member in a predetermined wiring pattern,
the? & It is formed by applying copper plating, but if the pitch between inner leads is made very narrow, the following problems will occur. In the case of the former etching method, for example, if the target pitch between inner leads is 70μ, the width of the conductor in the inner lead part will be about 35μ, but if the thickness of the copper foil layer is 35μ.
If the ratio is 1, the ratio of conductor width/conductor thickness will be less than 1, and in such a case, side etching will be significant and the cross-sectional shape of the inner lead portion of each wiring will become trapezoidal.

In addition, in the case of the latter plating method, there is a possibility that bumps protrude in the pitch direction from the stacked plating layers, causing a short circuit between wirings.
-, it may even reach about 20μ so. In order to solve such problems, it is desirable to reduce the thickness of the metal wiring in any of the above methods. In other words, in the etching method, copper 7i! i
7! ! If the thickness of the plating is thin, side etching will not progress much and wiring with an almost rectangular cross section will be obtained.Even in the plating method, if the plating thickness is thin, the bumps will not grow as much and the risk of short circuits will be reduced. [Problems to be Solved by the Invention] However, as described above, the inner lead portion of the metal wiring in a conventional chip carrier has an overhang structure protruding from the opening of the device hole, so it is difficult to connect with the semiconductor device chip. The metal wiring alone must withstand the pressure during bonding. This pressure resistance (hereinafter referred to as “
It is said that 5 to 15 g is necessary for the finger strength (referred to as "finger strength"), but if the copper foil layer is made thinner, for example, 25 μm width.
The finger strength of copper foil wiring with a thickness of 18 μl is 12 g, and metal wiring with such a thin thickness may not be able to withstand the pounding of semiconductor device chips, which is a factor that reduces product reliability. It had become. An object of the present invention is to provide a chip carrier that allows finer metal wiring, has sufficient finger strength, and has excellent bonding workability and durability. [Means for Solving the Problems] To achieve the above object, according to the present invention, a plurality of sets of metal wirings each having an inner lead portion connected to a terminal portion of a semiconductor device chip to be mounted are connected to a flexible film member. A chip carrier is provided which is formed radially toward a region on which the chip is to be placed on one surface of the chip carrier, and in this chip carrier, each of the metal wirings includes at least the inner lead portion and is connected to the metal wiring. In a limited first region formed on a flexible film member and in which the flexible film member includes the inner lead portion, a portion between each metal wiring and inside the tip of each inner lead portion. It has an opening.

In the chip carrier according to another aspect of the present invention, the flexible film member is reduced in a second region surrounding the opening and including the inner lead portion on a side opposite to the surface with the metal wiring. In this second region, the film member has a relatively thinner wall thickness than in the surrounding third region. In one form of the chip carrier in the wood invention, the film member is in the shape of a long flexible tape, and the tape has a plurality of rows of regions on which the chips are to be placed, each of which has a shape of a flexible tape. The metal wiring is placed in each of the storage areas. In another embodiment, the film member is in the form of a batch type in which the film member is separated into one or more chip placement sections. Here, the first region includes a region (area A) surrounded by the tip of the inner lead portion of the flexible film member, and a region (area B) in which at least the inner lead portion of the metal wiring is formed. The opening formed in the first region is a space (film component does not exist)
It is sufficient as long as it forms. Further, the second area includes area A and extends outward from it,
However, it is narrower on the inside than the entire area where the metal wiring is formed (the area surrounded by the actor lead part or the outer tip of the metal wiring), and the third area has a normal thickness around the second area. Any area may exist, and in some cases, the second area may be the same as the first area.

[Function J] In the chip carrier according to the present invention, the inner lead portion of the metal wiring does not have an overhang structure of a single metal wiring as in the conventional case, and the entire length of the inner lead portion is made of a flexible film. formed on the member. For this reason, the inner lead part is supported and reinforced by the flexible film member up to its tip, so even if the thickness of the metal wiring itself is reduced, it can withstand sufficient strength against heating and pressure during the bonding process. can. Therefore, the metal wiring can be made thinner without reducing the finger strength, making it possible to make the metal wiring ultra-thin, which was previously impossible. In addition, since the inner lead part is reinforced with a flexible film member, the inner lead part may be deformed due to contact with some object, etc., or the adjacent inner lead may be damaged due to disorder of the arrangement of the tip part. Accidents such as short-circuiting due to contact with other parts are less likely to occur. In particular, when the present invention is applied to a tape carrier, the orderly arrangement of inner leads is maintained from the time of manufacturing the tape carrier to the time of bonding with a semiconductor device chip. In addition, the chip carrier of the present invention has an opening in the first region, particularly in a region between the inner leads and inside the tip of the inner lead portion. Here, the planar shape of the flexible film member that reinforces and supports each metal wiring in the first region is preferably the same shape as the metal wiring, at least in the inner lead portion, but it may be larger. ．． That is, in the first region, the flexible film member does not need to span the metal dispensing space, but should just form a space there. This is to make each inner lead part electrically and structurally independent in the pitch direction between the connection pads of the semiconductor chip by providing an opening between at least the inner lead parts of each metal wiring. It is. This opening eliminates the influence of thermal stress caused by the difference in coefficient of thermal expansion between the metal wiring and the flexible resin member, at least in the pitch direction. Further, in the present invention, by forming the above opening,
A space is created here without the presence of the flexible film member. Therefore, it is advantageous in preventing impurity ions contained in the flexible film member from transferring to the semiconductor chip and destroying the semiconductor device chip. Furthermore, in the present invention, in the second region, the thickness of the flexible film member supporting the metal wiring is made thin within a range where a predetermined figure strength can be obtained. Thermal stress caused by differences in expansion coefficients can be further reduced, especially in the length direction of the wiring. In addition, thermal deformation of the inner lead part is less likely to occur, so very good bonding workability can be obtained, and fatigue failure of the connected part due to thermal changes after connection is less likely to occur. Furthermore, in the present invention, the thickness of the flexible film member in the third region is maintained as in the conventional chip carrier;
It is possible to maintain the necessary film strength required for a chip carrier, such as strength against feeding by a sprocket. Especially in the case of tape carriers,
This simplifies the tape winding process and other handling steps from tape manufacturing to bonding with semiconductor device chips. Note that if this second heavy region is made to correspond to the conventional device hole drilling region, this opening can have the same function as the conventional device hole. Furthermore, the first region may include, for example, an outer lead portion of metal wiring. In this case, the opening is formed over a wider area than the conventional device hole drilling method, but since each metal wiring is reinforced and supported by a flexible film member, each metal wiring has its own strength as a lead. Can be retained. In this case, use an appropriate bridge (film member) between each metal wiring.
It is also possible to support this in common. On the other hand, if necessary, the flexible tape member may be removed from a limited area including the actor lead part or the like, or the thickness may be reduced to form a thinner interior area, separately from the first heavy area. good. This is a problem when attaching a semiconductor chip to the tape carrier described above to make a semiconductor device, and then connecting it to the terminal section of an external circuit device. When electrically connecting by direct bonding, it is desirable to form a thin film part in the above areas to increase the finger strength of the outer lead part. In addition, when selling a general semiconductor device, for example, if the arrangement of the terminal part of the external circuit device is different from the arrangement of the outer lead part, or if the bonding position is on the back side, the outer lead In some cases, the area C including the outer lead portion may not be formed into a flexible film member, taking into consideration the bendability of the material, electrical bonding conditions, etc. By the way, the thickness of the flexible film member described above may be determined individually taking into consideration the film strength required as a chip carrier, the above-mentioned finger strength, bendability during bonding or use, etc.
For example, bendability may be ensured by reducing or removing the thickness of only the bent portion. In addition, separate C
When a thin wall part is provided, a part that maintains the normal thickness remains between the inner lead part and the outer lead part, but this part can be given the function of a support ring. The method for manufacturing the tape carrier according to the present invention is as follows. Note that the following method is an example, and is not limited to this method. First, polyimide. Polyphenylene sulfide. polyethylene terephthalate. By spatter deposition method, it is applied to one side of a flexible film member with a thickness of about 10 to 200 μ- made of a material with excellent heat resistance such as liquid crystal polymer.
Thickness o. l~1μ1 metal skin It! (For example, copper.
chromium. Nickel, etc.) are formed. Then, if necessary, further copper plating is applied to 1 to 20 μm.
The metal foil layer is made mainly of copper, and this metal foil layer is etched, or after the metal film is formed, unnecessary parts are masked (masked with a negative pattern) and copper plating is applied, and then the metal film is flashed. , a metal wiring is formed by etching.

After that, in the first region, the flexible film member in the part where the metal wiring is not formed is removed by etching or the like, and openings are formed between the metal wiring and in the area inside the tip of the inner lead wire. At this time, if necessary, the flexible film member is removed by etching or the like from the side of the flexible film where the metal wiring is not formed (back side). Furthermore, when forming a thin portion of the flexible film member in the second area, the flexible tape member is removed from the back side of the area excluding the opening from the second area. A thin section with a predetermined thickness is formed on the surface. Furthermore, before forming the openings in the first region, the flexible film member in the second region may be previously removed from the back side, and then the openings may be formed in the first region. Here, as a method for reducing the thickness of a flexible tape member made of a polymer film, there is, for example, plasma etching as a dry etching method. In this method, E
By spraying plasma-activated gas onto the surface to be etched using CR plasma or the like, the polymer film in that area is removed. In addition, if the flexible tape member is made of polyamide film, a mixed solution mainly consisting of hydrazine and ethylenedia. Favorable results can also be obtained by wet etching using a solution of an alkaline chemical such as potassium hydroxide dissolved in ethanol or water. Note that the thickness of the thin film portion formed in the second region of the flexible tape is preferably approximately 5 μm or more in order to ensure sufficient finger strength for the inner lead portion of the metal wiring. In order to prevent deformation of the inner lead portion due to thermal stress, it is preferable that the thickness be equal to or thinner than the metal wiring.

For example, when the flexible tape member is made of polyimide film, it is desirable to have a thickness in the range of 5 to 25 μm from the point of view of finger strength. In addition, if you want to remove all the flexible tape member or shape the thin part in the area including the outer lead part, etc., you can do it according to the above method. [Example] An example of the present invention will be described with reference to the drawings. The following example describes the case where a tape carrier is used as the chip carrier, but the case of a single batch type is almost the same. FIG. 1 and FIG. 2 show the first embodiment of the present invention.
FIG. 2 is a partial plan view and a partial cross-sectional view of a tape carrier according to an embodiment of the present invention. In this example, first, a 0.2 μm thick copper film was attached to one side of a flexible tape 2 made of a polyimide film with a thickness of 50 μm by sputter deposition, and then electrolytic copper plating was applied to make the tape thicker. A #4 foil layer with a diameter of 10 mm was formed. Then, the copper foil layer was etched using a ferric chloride aqueous solution to form a plurality of sets of metal wiring 1 of a predetermined length in the longitudinal direction, each having a conductor @ d = 2 sμ 1 and a conductor pitch P = 50 μl. In addition, in Figure 1, the number of wires in the four sets of metal wires is omitted. In the metal arrangement in the wooden embodiment, the inner lead portion 1a to be bonded to the pump 7 of the semiconductor device chip 6 is placed on the inside, and the actor lead portion 1b to be connected to the terminal portion of the lead frame or external circuit board is placed on the outside. They are arranged radially in four directions as shown in Figure ■. Here, in the metal wiring 1 of this embodiment, an outer lead part 1b is provided in a one-to-one correspondence with an inner lead part 1a, and each actor lead part 1b is connected to an outer circuit such as a lead frame or a circuit board. Although it is designed to be connected to the terminal of the device, it is not limited to this. That is, the metal wiring formed on the tape carrier according to the present invention is not limited to the case where wiring having an inner lead portion at one end and an outer lead portion at the other end are lined up at a predetermined pitch as shown in FIG. In some cases, the outer lead part and the inner lead part correspond to one another, or the inner lead part is connected to a predetermined circuit formed on the outside thereof. Also. In this embodiment, only one inner lead portion to which a semiconductor device chip is attached is formed in one metal wiring, but in some cases, one inner lead portion may be formed.
A plurality of inner leads may be formed on the metal wiring of the book. Thereafter, an opening 3 is formed in a first region consisting of a region A inside the tip of each inner lead and a region B including the inner lead portion and surrounded by the inner lead portion. First, the inner lead portion of the flexible tape 2 has heavy metal wiring in area A and area B inside the tip of the inner lead wire 1a! The entire front and back surfaces of the tape 2 are coated with an alkali-resistant etching resist, except for the portion where a is not formed. That is, the outside of the first region and the portion where the metal wiring is formed inside the first region are protected.

This tape 2 was placed in 5N potassium hydroxide aqueous solution.
l. at 0°C. After soaking for s hours, it was washed with water. As a result, the portions of the polyamide film that were not protected by the etching resist are removed, and openings 3 are formed between the area A in the first area and each metal wiring. In this embodiment, since the second region is the same region as the conventional device hole drilling section, the device hole is defined by the opening 3. In addition, subrocket holes 5 and outer lead portions Ib&: are provided at a predetermined pitch in the longitudinal direction of both sides of the tape 2.
When providing the actor lead hole 4 formed in the corresponding part, for example, the part other than the hole part (4.5) is covered with an alkali-resistant etching resist, similar to the method used to form the FTF film hole described above. The holes 4.5 can be formed by etching with an alkaline solution.

However, these are not necessarily necessary; for example, if it is possible to feed the tape 11 times without using a subrocket, the subrocket hole 5 is not necessary, and the outer The outer lead hole 5 is not necessary when connecting the lead portion 1b to a terminal portion of a circuit board or the like. Regarding the tape carrier produced as described above, as shown in the enlarged cross-sectional view near the inner lead part in FIG.
When bonding the bump 7, since the inner lead part 1a is reinforced and supported by the flexible tape 2,
The inner lead portion 1a did not bend due to the pressure applied during pounding, and the pounding processability was very good. Next, a second embodiment of the present invention will be described. In this embodiment C, the tape carrier produced in the same manner as in the first embodiment is further processed, and as shown in FIG.
A thin wall 208 is formed in the second region including the part where the thin wall is formed. In this second embodiment, on the back side of the tape 202, the flexible tape 202 is
The entire front and back surfaces of the tape 202 were protected with an alkali-resistant etching resist, and then the tape 202 was immersed in a 5N aqueous potassium hydroxide solution at 50° C. for 1 hour, and then washed with water.
As a result, the thickness of the remaining bulge in the area C that was not protected by the etching resist was 9μ. That is, in this embodiment, the flexible tape 20 is etched by wet etching.
The thickness of the second region of No. 2 is reduced from the back of the tape 202 (on the back side of the page) to form a thin portion 208 (region C in FIG. 3). In this example, since the thin wall portion 208 is as thin as 9μ, the inner lead portion 201a is not thermally deformed due to thermal stress caused by heating during bonding, and bonding workability and stability after connection are very good. there were. On the other hand, in this second embodiment, a thin wall portion is also formed in the portion corresponding to the actor lead hole 4 in FIG. Along with miniaturization,
It maintains the strength required for connection wiring to the terminals of Uiro circuit devices, and provides high bonding workability despite the miniaturized wiring. In this example, Mitsubishi Chemical Corporation ■, product name rNOVAXJ, is used as the flexible tape member, which has excellent etching resistance as described above, and is also translucent, so it is easy to use during bonding. This is because image processing and the like in alignment can be easily performed.

Therefore, if other products are used as the flexible tape member, the etching conditions etc. will be different. Here, in the embodiment of the present invention, the metal wiring 20! of the tape 202! Although the semiconductor device chip 206 is located on the formation surface side, the present invention is not limited to this. for example. Metal wiring 20 forming the inner lead portion 201a from the back side of the i-thickness portion 208
A semiconductor device chip 2 is formed on the back side of the thin film part by a method such as providing a perforation that reaches the hole and extending a protruding electrode made of a conductor bonded to the metal wiring into the perforation.
06 can be installed. As shown in the enlarged cross-sectional view of the vicinity of the device hole 203 in FIG. 3 for the tape carrier manufactured as described above, when the inner lead portion 201a and the punch 207 of the semiconductor device chip 206 were bonded, the inner lead portion However, since the inner lead 201a is reinforced with the thin wall 208 of the flexible tape 202, the inner lead 201a does not bend due to pressure. In addition, in this embodiment, since the opening hole 203 having the same function as the device hole is provided, when performing resin fixation at the product stage, the opening hole 203 is used as the device hole to secure the adhesively fixed resin. It has the advantage that the work can be done easily because the information can be poured into the system. Next, the lead strength of the metal wiring reinforced and supported by a flexible film member will be explained for the third example. 4 and 5 are a partial plan view and a partial sectional view of a tape carrier according to a third embodiment of the present invention. In this example, the region D including the actor lead portion 50lb of the metal wiring 19501 is the first region and the second region, and the flexible tape 502 in the region D is removed by almost the same method as above, As shown in Figure 5, the metal wiring 501 is reinforced and supported only by the thin wall 508. In this embodiment, a polyimide resin film is used as the flexible film member 502, and C is used as the metal wiring 501.
I used u. Further, the thickness of the metal wiring 501 and the thickness of the thin portion 508 of the film 502 are each 7μ, and the surface of the metal wiring 501 has an additional 0.5μ of S.
N-plated. 4') Regarding the tape carrier of the third embodiment, as shown in FIG. 5 (enlarged sectional view near the device hole), when the inner lead part 501a and the terminal part of the semiconductor chip 506 were bonded, the inner lead part 501a and the terminal part of the semiconductor chip 506 were bonded. Section 501
Since a is reinforced and supported by the thin wall portion 508,
The inner lead 501a did not bend due to pressure, and the bonding workability was very good. Here, the strength of the metal wiring (lead part) reinforced by the thin-walled part in this example will be explained. For comparison with this example, the following two samples CB), (C)
(Both are coated with Sn plating for 0.5 μs.
) is used.・Sample (B) The formation method and size of the metal wiring are the same as in this example, and there is no reinforcing support part.・Sample (C) A copper foil with a thickness of 18μ is used as the original fabric, the thickness of the metal wiring is 18μ, and there is no reinforcing support part. For each of the above chip carriers, the inner lead part of the metal wiring was bonded to 44 semiconductor chips with gold bumps, and the outer lead part was further bonded to the connection part on the glass epoxy substrate, and then the tensile strength of the lead part was measured. did. The results are shown below. As is clear from the table above, in this example, the strength of the lead portion is approximately three times that of the case of only metal wiring of the same thickness (^), and the thickness is approximately 2.5 times. It is clear that the material is stronger than the material (B) consisting only of metal wiring. As described above, in this example, the lead strength is maintained even if the thickness of the metal wiring is reduced. In the above embodiments, copper metal wiring was formed, but the metal wiring of the present invention is not limited to copper, and may have a two-layer structure of copper and other metals, or may be composed of only metals other than copper. Needless to say, it's a good thing. Next, as a fourth embodiment, common examples of the tape carriers produced in the first to third embodiments will be described. First, semiconductor device chips were placed over multiple device holes in a tape carrier using the usual method, creating multiple semiconductor devices connected on the tape. These semiconductor devices were separated into individual parts by cutting the carrier tape, and the outer lead portion on one side of the resulting single semiconductor device and the manual terminals of the electrode substrate of a liquid crystal panel, which was a separately prepared display device, were separated. The parts were electrically connected. Anisotropic conductive adhesive was used for this electrical connection. In addition, the actor lead section on the other side of the semiconductor device was electrically connected to the clapper section of the circuit board for drive control of the liquid crystal panel. The same anisotropic conductive adhesive as above was used for this electrical connection. When we assembled a liquid crystal display unit using this liquid crystal panel, we obtained a very good liquid crystal display unit with high reliability against disconnections. In this fourth embodiment, an example was described in which a semiconductor device using a chip carrier according to the present invention is applied to a liquid crystal display unit, but it can also be applied to a plasma display unit, an electroluminescent display unit, etc. Needless to say, it is possible. [Effects of the Invention] As described above, the chip carrier according to the present invention can reduce the thickness of the metal wiring, so it is possible to reduce the width and pitch of the metal wiring. It becomes possible to Therefore, it is possible to support the mounting of semiconductor device chips with a very narrow pitch between bins, which is extremely useful as semiconductor device chips are becoming increasingly highly integrated. Furthermore, if you use this chip carrier and combine it with a semiconductor device chip to create a product as a semiconductor device,
The labor and cost at the manufacturing stage can be reduced, and the occurrence of defective products is also reduced, so product costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 shows a partial plane view of a tape carrier according to a first embodiment of the invention, FIG. 2 shows a partial cross section of a tape carrier according to a first embodiment of the invention, and FIG. , shows a partial cross-sectional view of a tape carrier according to a second embodiment of the present invention, FIG. 4 shows a partial plane view of a tape carrier according to a third embodiment of the present invention, and FIG. A partial cross section of a tape carrier according to a third embodiment is shown. [Description of symbols of main parts] 1...Metal wiring 1a...Inner lead portion 2...Flexible tape 3...Device hole 6...Semiconductor chip 7...Bump 8... Thin film part

Claims (1)

[Claims] 1. A plurality of sets of metal wires each having an inner lead portion connected to a terminal portion of a semiconductor device chip to be mounted, on which the chip is placed on one side of a flexible film member. The chip carrier is formed radially toward a desired area, wherein each of the metal wirings is formed on the flexible film member including the inner lead portion, and the flexible film member is formed on the flexible film member. A chip carrier characterized in that, in a limited first region including the inner lead portion, an opening is provided between each metal wiring and in a portion inside the tip of each inner lead portion. 2. The chip carrier according to claim 1, wherein the flexible film member is arranged on the side where the metal wiring is located in a second region including the inner lead portion around the opening. A chip carrier characterized in that the thickness is reduced on the opposite side, and the film member has a relatively thinner wall thickness in this second region than in a surrounding third region. 3. A chip carrier according to claim 1, wherein the film member is in the shape of a long flexible tape, and the tape has a plurality of areas on which the chips are to be placed. A chip carrier characterized in that the metal wiring is arranged in rows and the metal wiring is arranged in each mounting area. 4. A combination of a chip carrier, a semiconductor device chip, and a display device according to claim 1, comprising:
The semiconductor device chip is mounted on the chip carrier, and the semiconductor device chip and the display device are electrically connected to each other via the metal wiring of the chip carrier, so that the combination forms a display unit. Something characterized by the fact that it consists of 5. A combination according to claim 4, characterized in that the display device comprises a liquid crystal display panel.