DE4128261A1 - ANISOTROP ELECTRICALLY CONDUCTING COMPOSITE MEMBRANE AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

The invention relates to a composite or composite membrane an anisotropic electrical conductivity and a Method of making this membrane. The invention relates in particular to an anisotropically electrically conductive Composite membrane used to manufacture an electrical Connection between different electronic parts or Devices can be used. This membrane can for example for the connection between a glass substrate for a liquid crystal display console and a flexible, printed Serve to create a driver circuit or a circuit Provide support in the form of a film, with an IC on such a printed circuit is present. It is also possible, a so-called chip-on-glass connection with a to provide directly mounted IC. The invention relates also a method for producing such a membrane.

It is known a connector (interconnector) made of an electrically conductive rubber is made for Establishing an electrical connection between the glass substrate of a liquid crystal display panel, which follows is referred to as LCD (liquid crystal display panel), and a flexible printed circuit, hereinafter referred to as FPC (flexible printed circuit board) is used, to provide a driver circuit for the LCD. Given the development in recent years, according to which the distance of Arranging the arrays between the glass substrate of the LCD and the FPC electrodes to be connected, which was previously around 0.4 mm or above was reduced to 0.3 mm or less by  the considerable increase in the number of picture elements To take into account that in a large format LCD modern electronic instruments sometimes required are increasingly anisotropic electrical these days conductive membranes of the dispersion type for producing a such electrical connection used. It is about a composite membrane in which fine particles from one electrically conductive material, for example made of metal, in the matrix is dispersed from a hot melt adhesive. As Anisotropic electrically conductive membranes are used today frequently used those that are manufactured by uniform dispersion of roughly spherical particles made of a plastic resin covered with a metal or a solder alloy are plated and a diameter of 10 to 30 microns own, in the matrix of a hot melt adhesive from a thermoplastic resin, such as a copolymer with a block structure of styrene-butadiene-styrene, where a Means to increase stickiness, a retarding aging Agent, a latent hardener and the like are mixed will. A resin composition is obtained formed into a film with a thickness of 20 to 30 microns is spread by spreading the composition onto a substrate film whose surface supports detachment. The film is then cut into strips with a width of 2 cut up to 3 mm. Such an anisotropic electrical conductive hot melt type membrane in the form of a strip becomes removable after removing the protective surface Film between the arrays of electrodes to form a Sandwiches inlaid. Then the order at 130 up to 190 ° C for a period of 10 to 20 s, to get a heat seal and the to establish anisotropically electrically conductive connection.

The usual anisotropically electrically conductive described above Membrane, in which electrically conductive particles in the matrix of a hot melt adhesive are dispersed, but have various Disadvantages and causes problems. Because the electrically conductive Particles dispersed in the matrix in a non-controlled manner are, for example, aggregates often form  primary particles. This may lead to failure the electrical insulation between adjacent electrodes. The insulation between adjacent electrodes can also be done by Chains of the electrically conductive particles are interrupted, which after the production of the flowable state in the course of Heating under pressure in the adhesive material around the heat sealed Sections are formed. Contains the powder coarse and fine from the electrically conductive particles Particles with a big difference in particle size, then can only have a good electrical connection between the coarse particles trapped in the electrodes be while the connection between the electrodes that trap relatively fine particles between them, due to the insufficient contact situation between the opposite electrodes and the particles more or is less bad. If also the amount of electrical conductive particles mixed with the adhesive is reduced to prevent that described above Interruption of isolation between neighboring Electrodes is prevented, then this can lead to no electrically conductive particles between the opposite as well as to be electrically connected to one another Electrodes are included. This naturally leads to the fact that no electrical connection can be made. Furthermore it is assumed that the minimum distance in the Electrode arrangements on the glass substrate of an LCD and an FPC using an anisotropic electrical conductive membrane of the type described electrically together can be connected, is approximately 0.2 mm. In Given the future increase in the number of picture elements, which is partly due to the fact that more and more monochromatic displays through colored displays to be replaced, it is necessary to be ever finer To provide electrode arrangements in which the distance is less than 0.2 mm.

The object of the present invention is to create a new anisotropic to provide electrically conductive composite or composite membrane, to establish an electrical connection from  Electrode arrays can be used with a small distance can, this membrane being free from those described above Is disadvantage and is not associated with the problems, those in the previously known anisotropically electrically conductive Compound membranes of the dispersion type occur. Task of The invention is also an efficient method of manufacture to provide such a membrane.

This object is achieved by the anisotropic method according to the invention electrically conductive composite membrane, which is marked by

• (a) a film of an electrically insulating polymer material with a variety of perforations and
• (b) a variety of double-headed metal pins, one of which one through one of the perforations in the film from the electrically insulating polymer resin essentially perpendicular protrudes to the surface of the film and is secured there or is held, each of the heads over the surface of the Harz film protrudes.

This anisotropically electrically conductive composite membrane according to the invention can be produced by the method according to the invention which is characterized in that one

• (a) a film of an electrically insulating polymer resin made on the surface of a metal substrate,
• (b) a variety of perforations in the film from one electrically insulating polymer resin on the surface of the Metal substrate, preferably by irradiation with a Laser beam or by photolithography
• (c) the surface of the metal substrate on which the film is made the electrically insulating polymer resin is formed by the perforations in the resin film to make recesses etches in
• (d) a double-headed pin made of a metal in each of the Creates perforations by electroforming or electroforming, each head of the double-headed pins over the The surface of the resin film protrudes and  
• (e) the metal substrate from the film from the electrically insulating Polymer resin that has perforations, each a double-headed metal stick protruding through the film keep, separates.

FIG. 1a shows a perspective view of the anisotropically electrically conductive composite membrane according to the invention, while FIG. 1b shows an enlarged cross-sectional view of this membrane in the direction indicated by the arrows Ib-Ib in FIG. 1a.

FIGS. 2a to 2e show schematically one of the successive stages of the method according to the invention for producing the anisotropically electroconductive inventive composite membrane in cross section.

The anisotropically electrically conductive membrane according to the invention consists of an insulating resin film with a variety of Perforations and a variety of double-headed metal pins, each through one of the perforations in the as a carrier sheet for the resin film serving the pins protrudes through the pin in the perforation in the film is secured or held, with each of the heads over the corresponding surface protrudes on the resin film.

FIGS. 1a and 1b show schematically an inventive anisotropically electroconductive composite membrane in a perspective view and in cross sectional view. The composite membrane consists of an electrically insulating polymer resin film 1 with a plurality of perforations 1 a, 1 a,. . ., which are arranged so that they have a suitable distribution or a suitable spacing, and a plurality of double-headed metal pins 2, 2 ,. . ., each of which has two heads 2 a, 2 a, all of which protrude beyond the surface of the resin film 1 . If such a composite membrane is inserted between the electrode arrays on the one hand on the glass substrate of an LCD and on the other hand an FPC or an IC chip under an appropriately selected contact pressure in the manner of a sandwich, then the electrodes arranged opposite one another on the two parts are reliable by one or more of the double-headed, through the perforations 1 a in the resin film 1 protruding pins 2 electrically connected, while the insulation between adjacent electrodes on the glass substrate of the LCD is completely given, since the metal pins 2, 2 ,. . . are reliably isolated from each other. It is readily understandable that the spacing of the arrangement or the distribution of the metal pins 2, 2 should be sufficiently fine in accordance with the spacing (pitch) of the electrode arrangements.

The polymeric resin film 1 , which acts as a carrier sheet or carrier film for the double-headed metal pins 2, 2 ,. . . serves, must have such a mechanical strength that it can be handled. In addition, it must be chemically stable enough to withstand the conditions prevailing in the etching and electroforming steps (c) and (d) of the process described above for producing the composite membrane. In addition, it must be sufficiently heat-resistant so that it can be used safely and is durable. Suitable polymeric resins from which the film can be made are polyimide resins, poly (amidimide) resins, polycarbonate resins, polyester resins, poly (etherimide) resins, polyarylate resins, poly (phenylene oxide) resins, poly (phenylene sulfide) resins, polysulfone resins, Poly (4-methylpentene) resins, poly (parabanic acid) resins, poly (ether sulfone) resins, poly (ether ether ketone) resins and the like.

If the step (b) for the production of the perforation 1 a, 1 a carried out in the resin film 1 by means of photolithography explained in more detail below, it is advantageous to select a polymer resin for the film 1 from those which aqueous in organic solvents or alkaline Solutions are soluble. Such resins are preferably selected from the group consisting of polyimide resins, poly (amidimide) resins, polycarbonate resins, poly (etherimide) resins, polysulfone resins, poly (4-methylpentene) resins and poly (parabanic acid) resins.

The polymeric resin film 1 should have a thickness of about 5 µm to about 500 µm, or preferably about 10 µm to about 200 µm. If the thickness of the film 1 is too small, the film can sometimes break in the course of the manufacturing process of the composite membrane. Films made of a highly resistant resin such as polycarbonate, polyester and polyimide resins break relatively rarely, even if the film thickness is small, for example 5 to 10 µm. On the other hand, if the film 1 is too thick, this can lead to difficulties in the production of the perforations 1 a with an accurately cylindrical configuration in the resin film 1 , since the perforations 1 a then sometimes have a tapered shape. In addition, the problem may arise that the etching solution used in stage (c), which is intended to penetrate the perforations 1 a, takes a very long period of time and that in stage (d) a long period of time is required for the electrical shaping of the double-headed metal pins 2 .

With regard to the metal from which the double-headed pins 2 are made, which protrude through the perforations 1 a formed in the polymeric resin film 1 , there are no particular restrictions, but the metal should have good electrical conductivity and with regard to durability Environmental influences should be stable. For step (d) for producing the double-headed pins 2 in the perforations 1 a, this step being carried out with the aid of electroforming, it is preferred to choose a metal which can be deposited with high efficiency during electroforming. Gold and silver can of course be used for such electroforming, but they are too expensive as an industrial material. Therefore, less expensive stainless steels, copper and nickel, are preferably used as metal for the double-headed pins 2 , which protrude through the perforations 1 a in the polymeric resin film 1 . It should hardly be worth mentioning that the body 2 b of the double-headed metal pins 2 has such a diameter that it just fits into the perforations 1 a, since the pins 2 are secured and held in the perforations 1 a. Each of the heads 2 a, which protrude beyond the surface of the resin film 1 , advantageously have a diameter of 150 microns or less. Their height above the surface is advantageously 2 to 100 microns. However, these dimensions are only preferred embodiments and are not restrictive. In addition, the dimensions of course depend on the distance or the distribution of the pins 2 . The diameter of the pin head 2 a is expediently at least 2 μm larger than the diameter of the perforation 1 a, through which the pin protrudes, in order to ensure that the pins 2 are held in the perforations 1 a. The pin heads 2 a should of course not be too large to ensure reliable insulation between two adjacent pins 2 .

The method according to the invention for producing the anisotropically electrically conductive composite membrane described above is explained in more detail below with reference to FIGS. 2a to 2e. In step (a) of this process, a film is produced from a polymer resin 1 on the surface of an electrically conductive substrate 3 , as is shown in cross section in FIG. 2a. The material of the substrate 3 is preferably a metal, since the substrate should have sufficient mechanical strength so that it does not break during the process, and because the etching and electroforming process in steps (c) or (d) must be suitable. Another important property of the metal substrate 3 is that the adhesive effect between the substrate surface and the film 1 formed thereon from a polymer resin is not too strong, so that the resin film can be gently removed from the substrate surface in step (e). Suitable such metals are, for example, stainless steel, nickel, iron and copper. Nickel-plated substrates of iron and copper can also be used. If desired, the surface of the metal substrate 3 can be coated before the step (a) with an agent which facilitates detachment from the surface. The metal substrate 3 should have a thickness such that it is not broken during the process in steps (a) to (e). In addition, the thickness of the substrate 3 should be so large that it is greater than the depth of the cavities 3 a formed by etching in step (c). On the other hand, the thickness of the substrate 3 should not be too large, since it is difficult to process a continuous film from the substrate 3 with a large thickness into a roll. In addition, this affects handling and is disadvantageous for the requirements of mass production. For this reason, the metal substrate 3 should have a thickness of 10 to 1000 microns or preferably 20 to 300 microns.

There are no particular restrictions on the method of forming a film 1 of a polymer resin on the surface of the metal substrate 3 in the step (a). Any of the usual methods of making films can be used. For example, if the resin is a thermoplastic, a melt of the resin can be extruded through a T-die to form a film of suitable thickness, which is continuously placed on the metal substrate in the form of a continuous film. If the resin is soluble in an organic solvent, the film is made from the resin by pouring a resin solution onto the metal substrate 3 using a suitable coating machine, for example a lip coater, a coating machine with a spatula , a reverse coater, an engraving coater or an air knife coater. The solvent is then evaporated off. If a thermosetting resin is used as the resin, the resin film formed on the substrate surface is cured by heating, and if necessary a post-curing treatment is carried out. If the polymer resin is produced in the form of a preformed film, the film can be adhered to the surface of the metal substrate by using a suitable adhesive which enables or allows peeling or peeling.

In step (b) of the method according to the invention, a large number of perforations 1 a are produced in the polymer resin film 1 formed on the surface of the metal substrate 3 , as is shown schematically in FIG. 2 b. Since the perforations 1 a have a very small diameter, they can hardly be obtained by mechanical means, for example by drilling. One of the methods that can be found for the production of the perforations a 1 application is, the irradiation with a laser beam using, for example, a carbon dioxide laser, a YAG laser or an excimer laser. Using a suitable lens system, the laser beams should be focused on the corresponding points on the resin film 1 where the perforations 1 a are to be produced. If the energy density of the laser beam is sufficient to produce perforations before focusing, then irradiation with laser beams can also be carried out using a mask having perforations, each of these perforations having a diameter which corresponds to that of the perforation 1 a to be produced in the resin film . In addition, the distribution pattern corresponds to the distribution pattern of the perforations 1 a to be formed in the resin film 1 . If desired, the power of the laser beam can also be modeled beforehand using a magnifying mask, the magnification ratio of which corresponds to the magnification of the focusing lens system and which has enlarged perforations which are arranged in an enlarged distribution, the irradiation taking place through the lens system.

The resin film 1 , which is to be provided with the perforations 1 a, is usually provided in the form of a continuous film. Expediently, the laser beam is allowed to move in the transverse direction of the film 1 while the film 1 is moved continuously or in sections in the longitudinal direction. The energy density of the laser beam should be selected appropriately depending on the thickness of the resin film to be processed. If the energy density is too high, not only the resin film 1 is processed with the laser. Rather, the surface of the metal substrate is also attacked by the laser beam, a cavity being formed which can possibly influence the accuracy of the subsequent etching treatment of the substrate surface in step (c) to produce cavities. It is sometimes preferred not to produce the perforation 1 a with a single pulse irradiation with a high energy density, but by irradiation with several pulses of the laser beam with a reduced energy density. The reduction in the energy density of the laser beam can of course be achieved by reducing the power of the laser. Alternatively, a laser beam can be divided into several branch beams using a suitable mirror system, so that each of the branch beams has a reduced energy density. In this way, the laser beam can be used for the simultaneous production of several perforations 1 a.

Another method that can be used to produce the perforations 1 a in the resin film 1 in step (b) is the so-called photolithography, which is well described in the prior art. In this case, the surface of the resin film 1 is first coated with a photoresist in liquid form. It is also possible to place a photoresist preformed in the form of a dry film on the surface. Subsequently, in the form of a pattern, actinic rays, for example ultraviolet light and electron beams, are irradiated through a patterned photomask, so that the photoresist layer has greater solubility in organic matter at the points where the perforations to be produced in the resin film 1 are located Solvents is awarded. The photoresist composition is then removed from the soluble point-shaped zones using an organic solvent. So-called negative-working as well as positive-working photoresist compositions can be used. However, it is preferred to use positive-working compositions because they have good solubility compared to the negative-working compositions and because the composition of the developer solution can be easily controlled. A typical positive-working photoresist composition of the soluble type consists, for example, of a cresol novolak resin, a photosensitizer, which is mainly a naphthoquinonediazide ester compound, and an organic solvent, each with a small amount of a decomposition accelerator, one Stabilizing agent and the like is added. A typical positive-working photoresist composition in the form of a dry film is, for example, the film made of a poly (o-nitrobenzyl methyl acrylate), in which the photochemical reaction of the o-nitrobenzyl groups is used.

The layer of the photoresist composition should have a thickness of 0.5 to 30 µm in the dry state if the composition is of the soluble type and 0.5 to 100 µm if it is in the form of a dry film. If the thickness is too small, craters may form and the resistance of the resistant layer to the developer solution would decrease too much. If the thickness is too large, the ability to dissolve when manufacturing the pattern will be reduced too much. After a type of pattern has been applied to the positive-working photoresist layer with the aid of a positive photomask, the photoresist layer is developed with the aid of an aqueous alkaline solution, for example tetramethylammonium hydroxide, in order to detach the photoresist composition in the punctiform zones, a large number of Perforations in the photoresist layer is obtained at locations that correspond to the perforations 1 a to be produced in the resin film 1 .

After the photoresist layer has been developed as described above, the perforations 1 a are formed in the resin film 1 . If the resin of film 1 is soluble in an alkaline solution as in the positive-working photoresist composition, for example polyimide resins, poly (amidimide) resins and poly (parabanic acid) resins, then the film with the patterned photoresist layer can be used immediately after development, immerse in an alkaline solution capable of dissolving the resin film 1 under the perforations formed in the photoresist layer. If the resin film 1 is insoluble in an alkaline solution but soluble in an organic solvent, the solvent resistance of the patterned photoresist can be increased by post-sintering at, for example, 100 ° C or above, after the development and before immersion in an organic solvent to dissolve the resin film in the zones under the perforations in the photoresist layer. The organic solvent used depends, of course, on the type of resin forming film 1 . For example, aromatic hydrocarbon solvents such as toluene and xylene can be used for a polycarbonate resin film and dimethylformamide, tetrahydrofuran and propylene carbonate, or a mixture thereof for a poly (parabanoic acid) resin film. After having the perforations 1 a produced in the resin film 1 is removed, the patterned photoresist layer by means of a remover solution. However, there is no disadvantage in not removing the photoresist layer, as long as the thickness of the photoresist layer is small enough and the adhesion between the photoresist layer and the resin film 1 is very strong.

The diameter of each perforation 1 a and the spacing of the arrangement of the perforations 1 a naturally depends on the electrode arrays which are to be connected to one another with the aid of the anisotropically electrically conductive composite membrane according to the invention. Since there is a trend to reduce the spacing of the electrode arrangement to 0.2 mm or less, the spacing of the perforations should also be chosen to be small enough to be 0.2 mm or less. The diameter of the perforations is preferably 0.1 mm or less, since it has been shown in the experiment that if the ratio of the diameter of the pins 2 and the distance between adjacent pins 2 is 1: 1, there will be no insulation problems, whereby however, the prerequisite is that the diameter of the pins 2 is 0.1 mm or less. If the perforations 1 a are not arranged orthogonally in the manner shown in FIG. 1 but in the form of a multiple “cross stitch” with respect to the longitudinal direction of a band-like membrane, then this has the advantage that the effective distance between the double-headed pins 2 is considerably smaller than the distance between two orthogonally spaced pins 2 .

Each of the perforations 1 a thus produced in the resin film 1 a is filled with the aid of electroforming with a metal serving as a connector pin. However, one must first carry out step (c), in which the metal substrate 3 is subjected to an etching treatment through the perforation 1 a in order to form a cavity 3 a, as shown in FIG. 2 c, so that the head 2 a of the pin 2 can protrude beyond the surface of the resin film 1 . The etching step can be carried out either non-electrolytically or electrolytically depending on the type of metal. For example, an etching solution can be used in non-electrolytic etching which contains a metal chloride, for example iron (III) chloride. Alternatively, one can electrolytically etch by anodic oxidation in an electrolytic bath using the metal substrate 3 as an anode. The process of electrolytic etching can be carried out continuously; this provides an efficient way of producing the desired anisotropically electrically conductive membrane in the form of a tape of continuous length.

If the diameter of the perforations 1 a formed in the resin film 1 a is relatively small, then it is advisable to achieve a complete etching of the substrate 3 through the perforations 1 a, without air bubbles remaining therein, from the etching solution or the electrolyte solution under pressure eject a nozzle or subject the solution to an ultrasonic vibration treatment. The depth of the cavities 3 a formed in the substrate 3 naturally depends on the diameter of the perforations 1 a. This depth is generally 2 to 100 microns. If the depth of the recesses or cavities 3 a is too small, then the height of the head 2 a of the double-headed pin 2 protruding beyond the surface of the resin film 1 is necessarily so small that no permanent and reliable electrical contact between the pin head 2 a and of the electrode to be connected to it can be achieved. On the other hand, if the depth of the recesses 3 a is too large, this can possibly lead to pin-to-pin contact on the pin heads 2 a, 2 a of adjacent pins 2, 2 , since an increase in the depth of a recess 3 a is necessarily associated with an increase in the diameter of the recess 3 a. This consequently leads to an excessively large diameter of the electroforming of the pin head 2 a carried out in stage (d).

The perforated resin film 1 on the substrate 3 is then subjected to the etching treatment in step (c) in step (d) of an electroforming to fill the perforations 1 a with metal pins 2, as shown in Fig. 2d. With regard to the metal to be deposited in the perforations 1 a, there are no particular restrictions if the metal can be deposited electrically. For example, gold and silver can of course be used; however, this is less advantageous for cost reasons. In this regard and in view of the versatility in the choice of the electrolyte bath, copper and nickel are preferably used. The electrolytic bath should not be too alkaline or too acidic to carry out the electroforming process so that the resin film 1 is not chemically attacked. In addition, the electrolytic bath should be selected from those that are suitable for a method of electroforming at a moderate temperature so as not to adversely affect the resin film 1 . Suitable electrolyte baths are, for example, a copper pyrophosphate bath or a copper sulfate bath, if the metal is copper, and a Watts bath and nickel sulfamate bath, if the metal is nickel. The electroforming process is carried out by so long until the pin head 2 a by a height of about 2 to 100 microns protrudes beyond the surface of the resin film.

If the metal of the double-headed pins 2 produced by electroforming was copper or nickel, then the surface of the pins 2 is preferably plated with a metal with a high corrosion resistance, since copper and nickel are not completely resistant to oxidation and corrosion, which means that a decrease in electrical conductivity is caused. One can carry out electroless plating, for example, prior to the electroforming to form on the surface of the perforations 1 a a corrosion resistant layer. Following the electroforming, the surface of one of the two pin heads 2 a is then plated before the resin film is separated from the substrate. Finally, the film 1 is separated from the substrate 3 or lifted off and then the surface of the other pin head 2 a is plated. In this way, the two pin heads 2 a, 2 a can be plated with different metals in accordance with the metals that the corresponding electrodes with which they are to come into contact. It is of course also possible that after lift-off of the film 1 from the substrate 3 are both pin heads 2 is a, a plated simultaneously. 2 The corrosion-resistant metal for plating can be a noble metal that has excellent corrosion resistance or a metal that can form an electrically conductive corrosion-resistant oxide. The surface of the pin heads 2 a, 2 a can alternatively be coated with a solder alloy, so that the solder metal layer serves to produce a bond by soldering when assembling the glass substrate of an LCD and an FPC using the anisotropically electrically conductive composite membrane according to the invention. Suitable metals and alloys for plating are, for example, gold, silver, palladium, platinum, tin, indium, molybdenum and chromium as well as alloys of these metal elements and solder alloys. The thickness of the corrosion-resistant plated layer is in the range of 0.01 to 10 µm because the protection would be incomplete if the thickness was too small. On the other hand, if the thickness is too large, the cost of plating is too high. If pins 2 made of copper are equipped with a corrosion-resistant gold plating, then preferably nickel is plated first before plating with gold, since direct contact of a gold layer with the pin 2 made of copper leads to a decrease in corrosion resistance, since the gold lasts diffused into the copper. If desired, in order to better peel or lift off the resin film 1 , which has the double-headed pins 2 , which were produced in the perforations 1 a, from the metal substrate 3 , a treatment to form a surface layer before the process for electroforming the pins 2 perform, which is easier to peel or lift off. This includes, for example, anodic oxidation that only lasts for a short time or immersion in an aqueous sodium chromate or sodium sulfide solution.

The resin film 1 , which has the perforations provided with the double-headed pins 2 , is separated or then lifted off from the metal substrate in step (e), as shown in FIG. 2e. This separation can be carried out in any known manner. For example, the resin film 1 on the metal substrate 3 can be immersed in a suitable solvent, or one can eject or spray a solvent onto the resin film 1 from a nozzle, if necessary into an array of ultrasonic waves. If the substrate 3 is a copper foil and the adhesion between the resin film 1 and the substrate 3 is so strong that no suitable solvent is available, the copper foil of the substrate 3 can be removed by etching in a suitable etching solution. However, this method is applicable only in those cases where the double-headed pins 2 are not made of copper, but made of nickel or other etch-resistant metals, although are not excluded with nickel plated copper pins. 2 A suitable etching solution for copper foils is, for example, an aqueous sodium or ammonium chlorite solution which has been made alkaline with ammonia water (pH of 10 or higher). If the resin film 1 can be attacked by an alkaline etching solution, the surface of the resin film 1 opposite to the substrate should be protected by a masking layer, which may be a layer of an adhesive, if it is desired that Product has an adhesive layer on a surface.

The anisotropically electrically conductive composite membrane obtained in the manner described above is usually used in the form of a tape which has been cut to a suitable width. Since the membrane is placed between two arrays of electrodes, the surfaces of the membranes are advantageously given a certain stickiness in order to improve their adhesion to the electrodes. So you can coat the membrane with a solution of a hot melt adhesive. It is then dried to form an adhesive layer on each of the surfaces. You can also laminate a film of hot melt adhesive onto the surfaces. The thickness of this hot melt adhesive layer should be such that the heads 2 a of the double-headed pins 2 are covered with the adhesive layer with a thickness of 5 to 50 microns. If the thickness is too small, no reliable adhesion can be achieved between the membrane and the electrodes. If the thickness of the adhesive layer is too large, care must be taken to ensure that an excessive volume of the adhesive does not flow through the space between the pin head 2 a and the electrode during the adhesive bonding by long-lasting pressing when heat is applied, so that the Effectiveness of the trained bond decreases. In this context, the adverse effects caused by the mass of the adhesive held between the membrane and the FPC should also be mentioned, which may result in a deformation of the FPC or a decrease in the reliability of the electrical connection due to an increase in voltage. There are no particular restrictions with regard to the adhesive used. For example, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, polyester resins saturated with copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-isobutyl acrylate copolymers, nylon-11, nylon-12, Ionomer resins and other thermoplastic resins or elastomers, which, if desired, can be mixed with a tackifying agent such as spruce resin or resin derivatives, unmodified or modified terpene resins, petroleum resins, coumarone-indene resins, phenolic resins, alkyd resins and the like, a latent hardener such as epoxy resins, polyisocyanates and the like, a photo-curable resin, an antioxidant, a stabilizing agent, etc. and an organic solvent such as toluene, methyl ethyl ketone, ethyl acetate, ethylene glycol monoethyl ether and the like to prepare a solution of the adhesive. Since the surface properties of the glass substrate of the LCD and the FPC, between which the anisotropically electrically conductive composite membrane of the invention is to be inserted and connected, of course differ from one another, it is sometimes advantageous to coat the membrane on one or the other surface with hot melt adhesives of different types Depending on the properties of the surface to be bonded. The anisotropically electrically conductive composite membrane according to the invention described above can advantageously be used to establish an electrical connection between two arrays of electrodes without the disadvantages and difficulties that arise when using conventional connecting membranes of the dispersion type, in which fine particles of an electrically conductive Material dispersed in the polymer matrix occur.

Below, the anisotropic electric of the present invention becomes electric conductive composite membrane and the process for its manufacture explained in more detail using preferred embodiments.

Example 1

A copper foil with a thickness of 100 µm and a width of 225 mm continuous length in the form of a roll on a surface with a poly (parabanic acid) resin varnish (Sollac XT-101, a product of Nitto Chemical Industry Co., Ltd.) with the help of an application machine equipped with a spatula coated. The film coated with the varnish was from the uncoated surface for 30 s at 100 ° C preheated. It was then continuous in an oven at 150 ° C for 60 seconds heated so that the varnish to form a resin film  with a thickness of 30 µm on the copper foil as Substrate was dried.

The resin film on the substrate surface was subjected to spot irradiation with a pulsed laser beam with a wavelength of 1.06 µm. The laser beam was emitted on a continuously excited YAG laser with TEM _oo oscillation mode with a maximum power of 12 watts (SL115L, manufactured by NEC Corp.). A YAG laser scriber with an ultrasonic Q-switch unit (SL231G, manufactured by NEC Corp.) built therein was used. The pulsed laser beam had a repeating frequency of 1 kHz, a peak output of at least 20 kW and a pulse width of about 80 ns. The laser beam was converged using precision optical lenses so that it had a diameter of 50 µm. As a result, a perforation with a diameter of approximately 50 μm could be produced with the aid of a single pulse irradiation in the poly (parabanic acid) resin film.

A first series of perforations was made in the transverse direction of the Resin film made by the pulsed radiation with the laser beam was repeated every time after the laser beam around 100 µm in the transverse direction of the film with continuous Length by means of a numerically controlled tape was shifted, forming a series of perforations were, each with a diameter of 50 microns and a Have a distance of 100 microns. After the first row of Perforations were made, the resin film was around 100 microns in Moved in the longitudinal direction. Then the laser beam irradiation performed as described above to a second series of To make perforations. More rows were then made Repeat this cycle. The perforations in the second, fourth, sixth, eighth, etc. row regarding the perforations in the first, third, fifth, seventh, etc. row not an orthogonal arrangement, but rather a multiple cross stitch arrangement. After the perforations in the manner described above were the surface of the perforated  Resin film with a gauze soaked in methyl alcohol grated and then rinsed with pure water to remove the in laser beam irradiation to produce the perforations remove any residues formed. Then was dried.

Thereafter, the one opposite to the resin film Surface of the copper foil with a pressure sensitive adhesive film Laminated for masking purposes. The perforated resin film on the copper foil was placed in an aqueous iron (III) chloride solution of 40 ° tree´ immersed in an etching tank while the caustic Solution was ejected from a nozzle onto the resin film. The Solution in the tank was vibrated with ultrasonic waves so that the perforations in the resin film are complete were filled with the etching solution until wells or cavities formed with a depth of 20 microns in the copper foil each corresponding to the perforations in the resin film. The resin film on the copper foil then became thorough rinsed with water and then in an aqueous for 1 s 1N sodium chromate solution dipped to a removable surface film to build. Then was with water washed.

The resin film on the substrate was then placed in a Watts bath submerged. The electroforming of nickel was carried out until a double-headed nickel pin in each of the perforations was trained. The pens had heads, each protruded by 20 µm over the surface of the resin film. in the The next step was the masking adhesive film on the back the copper foil is lifted off or peeled off. For complete Removal of the copper foil was the resin film on the Copper foil in an alkaline etching solution with a pH of 10 submerged. It was an aqueous ammonium chlorite solution, which was mixed with ammonia water (alkali Etch, a product of the Yamatoya Company). It remained the same Resin film with the double-headed pins back. Subsequently was washed with water and dried. That way The obtained poly (parabanic acid) resin film had double-headed Nickel pins, each about 50 µm in diameter  and with a distance of 100 µm in a multiple Cross-stitch arrangement were arranged to be anisotropic to serve electrically conductive composite membrane.

The surface of the double-headed nickel pins was covered with a Gold plating layer with a thickness of 0.015 µm electroless plating. On each of the surfaces of the An adhesive film was placed on the membrane as well as under pressure laminated and heated. The adhesive film had one Hot melt adhesive layer with a thickness of 30 µm (in dry Condition) and was made by using a polyester film a thickness of 50 microns with a silicone-based agent to make it easier to lift off the surface (Cellapeel Q-1, a product of Toyo Metalizing Co., Ltd.) coated was coated with an adhesive solution that was obtained was made by dissolving 100 parts by weight of one with copolymers saturated polyester resin with a glass transition point of 6 ° C and a softening point of 123 ° C (determined according to the ring-and-ball method; Bilon No. 300, a product of Toyoba Co., Ltd.) in 200 parts by weight of toluene, using an application machine was used with a spatula and where was then dried.

The anisotropically electrically coated with an adhesive conductive membrane was then cut into strips with a width of 3 mm cut up. The strip was between an array of Tin-plated electrodes on an FPC made from a 1 oz Copper foil with a thickness of 36 microns had been produced and which is 0.075 mm wide in an array with one Spaced 0.15 mm, and another array of Electrodes placed on an ITO electrode glass substrate, at the electrode width and the distance of the electrode arrangement were the same as above. By pressing with a Pressure of 40 kgf / cm² over a period of 10 s at 150 ° C the whole thing was connected.

The arrangement of two electrode arrays and the thus obtained connecting membrane was in terms of connection resistance between the pairs of opposing electrodes  thanks to the double-headed pins and the insulation resistance tested between two neighboring electrodes. It it turned out that with a thousand tested Electrode pairs the connection resistance between the Electrode pairs were 0.5 ohms / pin and that the Insulation resistance was at least 10¹⁰ ohms.

Example 2

A film made of a poly (parabanic acid) resin with a thickness of 30 µm was on the surface of a copper foil as in Example 1 prepared. The resin film was with a positive-working photoresist (ODUR-1010, product from Tokyo Ohka Kogyo Co., Ltd.) with the help of a roller coating device coated. The thickness of the coating was dry Condition 2 µm. The mixture was then precured at 120 ° C. for 20 minutes. On the other surface of the copper foil was a masking adhesive film applied. A positive photomask molten silica glass with one separated from the vapor phase Chrome plating layer that had a dot pattern, each of the points being 50 µm in diameter and was placed at a distance of 100 microns, was placed and brought into direct contact with the photoresist layer that through the photomask for a period of 10 s an exposure machine (PLA 520F CM-290, manufactured by Canon, Inc.) was exposed to ultraviolet light. The photoresist layer was then developed by: in a developer solution of a certain composition (ODUR 1010 Developer, product of the company listed above) during a Was immersed for 2 min at 23 ° C with stirring. It was then rinsed by placing it in a rinsing solution certain composition (ODUR 1010 Rinse, product of the above listed company) for a period of 1 min Stir was immersed. The one so patterned Photoresist layer that had perforations on the resin film, was dried and a post-curing treatment was carried out at 100 ° C. for 20 minutes subject. Then she was in for 5 min immersed a 5% by weight aqueous sodium hydroxide solution, so that the poly (parabanic acid) resin through the perforations in  the photoresist layer was removed, the perforations were formed in the resin film.

The subsequent stages of manufacture for an anisotropic electrically conductive composite membrane and the using of the perforated one obtained as described above Resin film, were the same as in Example 1. Die Test results show that the connection resistance between neighboring electrodes with a thousand electrode pairs tested was always 0.5 ohms / pin or less. The insulation resistance was always between adjacent electrodes at least 10¹⁰ ohms.

Claims (9)

1. Anisotropically electrically conductive composite membrane with

• (a) a film of an electrically insulating polymer resin with a plurality of perforations and
• (b) a plurality of double-headed metal pins each projecting through one of the perforations in the electrically insulating polymer resin film substantially perpendicular to the surface of the film holding it, each of the heads projecting above the surface of the resin film.

2. Anisotropically electrically conductive composite membrane Claim 1 characterized, that the film is made of an electrically insulating polymer resin has a thickness of 5 to 500 microns. 3. Anisotropically electrically conductive composite membrane Claim 1 or 2, characterized, that the perforations in the resin film have a diameter of not have more than 100 µm. 4. Anisotropically electrically conductive composite membrane after a of claims 1 to 3, characterized, that the head of the double-headed metal pin by one Height from 2 to 100 µm over the surface of the resin film protrudes.   5. Anisotropically electrically conductive composite membrane after a of the preceding claims, characterized, that that makes up the double-headed metal pins Material is copper or nickel. 6. Process for producing an anisotropically electrically conductive composite membrane

• (a) a film of an electrically insulating polymer resin with a plurality of perforations and
• (b) a plurality of double-headed metal pins each protruding through one of the perforations in the film of the electrically insulating polymer resin substantially perpendicular to the surface of the film holding it, whereby each of the heads protrudes above the surface of the resin film,

characterized in that one after the other

• (a) produces a film of an electrically insulating polymer resin on the surface of a metal substrate,
• (b) forming a plurality of perforations in the resin film made of an electrically insulating polymer resin on the surface of the metal substrate,
• (c) etching the surface of the metal substrate on which the electrically insulating polymer resin film is formed through the perforations in the resin film to form voids under the corresponding perforations,
• (d) a double-headed pin made of a metal in each of the perforations by electroforming, each head of these double-headed metal pins projecting above the surface of the resin film, and
• (e) separates the metal substrate from the film of the electrically insulating polymer resin, which has perforations, each of which holds a double-headed metal pin protruding through the film.

7. Process for making an anisotropic electrical conductive composite membrane according to claim 6, characterized, that the perforations in the resin film in step (b) produced by irradiation with laser beams. 8. Process for making an anisotropic electrical conductive composite membrane according to claim 6, characterized, that the perforations in the resin film in step (b) with the help of photolithography.