WO2006118211A1

WO2006118211A1 - Circuit board and method for manufacturing same

Info

Publication number: WO2006118211A1
Application number: PCT/JP2006/308878
Authority: WO
Inventors: Hiroyuki Ohata
Original assignee: Japan Gore-Tex Inc.
Priority date: 2005-04-28
Filing date: 2006-04-27
Publication date: 2006-11-09
Also published as: JP4630120B2; JP2006305921A

Abstract

Disclosed is a circuit board with excellent durability wherein a liquid crystal polymer is used for an insulating sheet and embrittlement of the liquid crystal polymer film is suppressed. Also disclosed is a method for manufacturing such a circuit board. Specifically disclosed is a method for manufacturing a circuit board which is characterized in that a liquid crystal polymer film is used as at least one of the surface sheets among the insulating sheets constituting the circuit board. This method is further characterized in that a fluorine-containing porous film is used as a releasing material when the liquid crystal polymer film is subjected to thermal compression bonding. A circuit board manufactured by such a method is excellent in durability.

Description

Specification

Circuit board and manufacturing method thereof

Technical field

The present invention relates to a circuit board using a liquid crystal polymer film and a method for manufacturing the circuit board.

Background art

[0002] A circuit board is also configured with a conductor and an insulating force. A single-sided board in which a circuit is formed on one side of an insulating sheet, a double-sided board in which a circuit is formed on both sides, and a plurality of insulators It is classified as a multi-layer board that consists of sheets and has three or more layers. As this insulator, a material having a composite material strength in which a glass cloth is impregnated with a highly heat-resistant resin such as an epoxy resin or a polyimide resin has been conventionally used.

[0003] In such a prior art, a multilayer board is manufactured together with a core sheet or the like having a circuit pattern formed on one or both sides after first producing a semi-cured pre-impregnated substrate by impregnating a resin with a resin. It is manufactured by laminating and thermocompression bonding. In some cases, a thick glass epoxy substrate is used as the core sheet, and a laminated body in which a copper foil is coated with a resin and B-staged is bonded thereto by thermocompression bonding. At this time, a release material is sandwiched between the hot pressing part of the thermocompression bonding apparatus and the laminate to facilitate peeling.

[0004] As this release material, JP-A-4-179520 discloses a release material (release protection sheet for hot press lamination) made of a porous fluorine resin sheet. In this technique, a dent due to the presence of foreign matter is solved by a release material having a cushioning property. Further, although not related to a circuit board, as a mold release material when press-molding using a pre-preda which is also a thermosetting resin and a reinforcing material, JP-A-6-31744 discloses a porous resin film cover. There is described a release material (release film) that has excellent air permeability and the like. In this technique, it is said that gas can be released by a porous release material.

[0005] By the way, since the resin used for the insulating sheet as the circuit board described above is non-thermoplastic, it cannot be melted by heating. Therefore, recycling is difficult because the copper and glass fiber resin that form the circuit cannot be separated efficiently. Therefore, the viewpoint of effective use of resources and environmental protection is not satisfactory. Also, the method of manufacturing a multilayer circuit board once via a pre-preda is never efficient.

[0006] As another insulator sheet, a circuit board using a film made of a non-thermoplastic resin such as polyimide has been developed. However, although such a technique does not require the use of a pre-preda, it is not difficult to recycle, and since an adhesive may be required for lamination, it is still not efficient. In addition, the use of adhesives can give rise to electrical properties.

[0007] On the other hand, if a substrate material made of thermoplastic resin is used, it can be recycled by heating, so that it can be recycled. Furthermore, by laminating the sheets and then thermocompression bonding to melt and soften the resin, the sheets can be easily fused without using an adhesive. Therefore, in recent years, circuit boards using thermoplastic resin as a substrate material have been developed, and thermoplastic resin is used as an insulating material, such as an all thermoplastic circuit board in which all insulating materials are thermoplastic resins. Technology related to the circuit board used has also been developed.

[0008] For example, in Japanese Patent Application Laid-Open No. 2003-273511, a film made of a thermoplastic resin is laminated with a circuit pattern formed thereon, and a thermocompression unit and a laminate of a thermocompression bonding apparatus are used for thermocompression bonding. A technique of disposing a cushioning material between the two is disclosed. This buffer material is formed by molding metal fibers or the like into a plate shape, and can suppress local stress concentration due to the presence or absence of a partial circuit pattern. As a result, the problem of circuit pattern misalignment can be solved. Moreover, it has the effect of suppressing the generation of voids by releasing the air remaining between the resin films. Further, there is a description that a release material may be disposed between the buffer material and the thermocompression unit of the thermocompression bonding apparatus.

[0009] By the way, among thermoplastic resins, a film containing a liquid crystal polymer as a main component (hereinafter referred to as "liquid crystal polymer film" t), which is excellent in low water absorption, heat resistance, electrical characteristics and dimensional stability. ) Is attracting attention. This liquid crystal polymer film can be used as a cover sheet or a core sheet of a circuit board.

[0010] Particularly, in order to cope with the recent increase in information processing speed, the dielectric constant should be reduced. In addition, it is effective to use a material with a low dielectric loss tangent (dielectric loss) in order to reduce transmission loss. In addition to being excellent in these characteristics, the liquid crystal polymer can form a cover sheet or constitute a multilayer circuit board without using an adhesive that causes the electrical characteristics to be abandoned.

Disclosure of the invention

[0011] As described above, Japanese Patent Application Laid-Open No. 2003-273511 discloses a technique for manufacturing a laminated circuit board having a thermoplastic resin film as a constituent element. However, the thermoplastic resin mainly used in Japanese Patent Application Laid-Open No. 2003-273511 is a mixture of a polyether ether ketone resin and a polyetherimide resin, and although there is a description of a liquid crystal polymer, it is merely an example. Only. Polytetrafluoroethylene is also exemplified as a mold release material, but this resin itself cannot release gas generated during thermocompression bonding, which is not porous. Is recommended. Furthermore, in this technique, if a separate material is used as the cushioning material and the release material, and the release material that is in direct contact with the force circuit surface has no cushioning property, particularly when a substrate having a fine circuit is manufactured, Even if a release material is used, problems such as circuit deformation may occur. In addition, when both the cushioning material and the release material are used, there is a risk that the sheet is easily transferred to the circuit board.

[0012] In addition, JP-A-4-179520 and JP-A-6-31744 describe a porous polytetrafluoroethylene sheet (film) as a release material. However, the material to be thermocompression-bonded used in these technologies is a pre-preda in which a glass cloth or the like is impregnated with an epoxy resin or polyimide resin, and the description is also suggested for the liquid crystal polymer film. It has not been done.

That is, when a circuit board is manufactured by using a liquid crystal polymer film as an insulator material and melt-softening the liquid crystal polymer film to integrate the sheets, a fluorine-based porous film is used as a release material. The example I had was strong.

[0014] Under such circumstances, for example, when a liquid crystal polymer film is disposed on the outermost surface of the laminate and thermocompression-bonded, if a film such as polyimide is used as a release material, the liquid crystal polymer film becomes extremely brittle. It has been clarified by the present inventor. Such embrittlement has a low yield. It becomes a big problem in actual use situations such as shortening the product life just by connecting to the bottom.

[0015] Therefore, a problem to be solved by the present invention is a circuit board having a liquid crystal polymer film as an insulator sheet, in which brittleness of the liquid crystal polymer film is suppressed and excellent in durability. It is to provide a method for manufacturing a circuit board.

[0016] The inventor has conducted extensive research on the thermocompression bonding conditions of the liquid crystal polymer film in the manufacturing process of the circuit board that solves the above-described problems. As a result, the brittleness of the surface liquid crystal polymer film in the prior art is caused by a hydrolysis reaction with water derived from the liquid crystal polymer film itself, and if the conditions for suppressing this reaction are adopted, the above-mentioned problems will occur. As a result, the present invention was completed.

That is, in the method for manufacturing a circuit board according to the present invention, a liquid crystal polymer film is used as a surface sheet of at least one of the insulator sheets constituting the circuit board, and the liquid crystal polymer film is thermocompression bonded. In this case, a fluorine-based porous film is used as a release material. Since the fluorine-based porous film has low water absorption, it has a water-porosity if it has almost no water, so that water derived from the sheet material can be discharged to the outside. As a result, the durability of the circuit board can be remarkably improved, for example, by suppressing hydrolysis of the liquid crystal polymer film and remarkably suppressing its embrittlement. The “liquid crystal polymer film” in the present invention refers to a film containing a liquid crystal polymer as a main component.

[0018] As the liquid crystal polymer film, it is preferable to use a film that is substantially liquid crystal polymer only. This is because the excellent characteristics of the liquid crystal polymer can be used effectively.

[0019] It is preferable that each insulator sheet of the circuit board is composed of a liquid crystal polymer film. It is also a preferred embodiment that a circuit pattern is formed on one or both sides of the liquid crystal polymer film, and the liquid crystal polymer film is placed on the circuit pattern and thermocompression bonded. This is because a flexible circuit board having a low dielectric constant and low dielectric loss can be obtained.

[0020] It is preferable to use a stretched porous polytetrafluoroethylene film as the fluorine-based porous film. The high effects are demonstrated by the examples described later. Power.

[0021] The circuit board of the present invention is manufactured by the above method and is characterized by excellent durability. Since the circuit board has the brittleness of the liquid crystal polymer film suppressed, the folding resistance and brittleness are improved, and the circuit board has excellent durability.

[0022] The method for producing a circuit board according to the present invention uses a fluorine-based porous film that has low water absorption and is porous as a release material. Therefore, the liquid crystal polymer film is not given moisture at the time of thermocompression bonding of the surface liquid crystal polymer film, and the water content of the liquid crystal polymer film can be released to the outside, so that the hydrolysis reaction can be suppressed. As a result, the folding resistance and toughness of the circuit board are improved as compared with the prior art, and the durability can be remarkably improved. In addition, since the fluorine-based porous film can exhibit both an effect as a mold release material and an effect as a buffer material, it is only necessary to facilitate the separation between the hot pressure part of the thermocompression bonding device and the circuit board. The cushioning force, especially the pressure on the circuit surface, can be made uniform. As a result, since deformation of the circuit pattern is suppressed, it becomes possible to manufacture a circuit board having an accurate circuit pattern. Compared to the technology that requires the use of both mold release material and cushioning material, it is particularly effective in the production of circuit boards having a dense circuit pattern, and the use of both is the cause of the problem. There is no risk that this phenomenon will be transferred to the surface of the circuit board. Furthermore, it becomes possible to reduce the number of necessary members and simplify the process, thereby reducing the cost.

[0023] Further, the circuit board manufactured by the method has a high durability because the brittleness of the surface liquid crystal polymer film that is a constituent element thereof is remarkably suppressed, and an accurate circuit pattern. It has excellent characteristics such as having In particular, since the flexible circuit board according to the present invention has excellent folding resistance and toughness, it is possible to prevent damage to the board itself and the circuit when inserted into a compact device such as a mobile phone.

Therefore, the circuit board and the manufacturing method thereof according to the present invention are extremely useful industrially.

Brief Description of Drawings

FIG. 1 is a diagram showing an embodiment of a circuit board according to the present invention. In the figure, 1 indicates a circuit pattern sheet, 2 indicates a cover layer, 3 indicates a fluorine-based porous film as a release material, and 4 indicates a hot press part of a thermocompression bonding apparatus. BEST MODE FOR CARRYING OUT THE INVENTION

[0026] The method for producing a circuit board according to the present invention uses a liquid crystal polymer film as at least one surface sheet of the insulator sheets constituting the circuit board, and thermocompression-bonds the liquid crystal polymer film. The main point is that a fluorine-based porous film is used as a release material.

[0027] The circuit board is mainly classified into a single-sided board, a double-sided board, and a multilayer board. In the present invention, a liquid crystal polymer film is used as at least one surface sheet of the insulating sheets constituting the circuit board. One of the features is that the film is thermocompression-bonded.

[0028] In a single-sided plate or a double-sided plate, a circuit is formed on one or both sides of a core sheet, and a cover layer is generally provided on the circuit surface. In the present invention, since a liquid crystal polymer film is used as at least one surface sheet, in the case of a single-sided plate, a force that makes only the core sheet or only the cover sheet a liquid crystal polymer film, both the core sheet and the force sheet are liquid crystal. A polymer film is used. In the case of a double-sided plate, at least one surface force bar layer is a liquid crystal polymer film.

The same applies to the case of a multilayer board, and a liquid crystal polymer film is used as at least one surface sheet. Therefore, when the cover layer is provided, the cover sheet is a liquid crystal polymer film, and when the cover layer is not provided, at least one of the outermost core sheets (the sheet on which the circuit is provided) is a liquid crystal polymer film. Consists of.

[0030] Here, the surface sheet is a sheet existing on the outermost surface of the insulating sheet constituting the circuit board at the time of thermocompression bonding, and a case where it is a cover sheet and a circuit on the surface thereof. It may be a core sheet. When manufacturing a circuit board using this surface sheet as a liquid crystal polymer film, the liquid crystal polymer film on the surface is directly affected by the release material during thermocompression bonding. However, in the past, when a liquid crystal polymer film was used as a circuit board material, there was a strong example in which a fluorine-based porous film was used as a release material. In other words, the present invention can be clearly distinguished from the prior art by the requirement that a liquid crystal polymer film is used as at least one surface sheet and a fluorine-based porous film is used as a release material.

[0031] It can be used as a material for an insulator sheet, and other than the liquid crystal polymer For example, ceramic; silicon; carbon fiber, glass fiber and other fibers impregnated with epoxy resin, polyimide resin, polyphenylene ether resin, BT resin; polyimide sheet, polyether ether ketone sheet , Polyetherimide sheets, polyethylene naphthalate sheets, polyethylene terephthalate sheets, and mixed resin sheets thereof (hereinafter, “sheet” includes a film).

[0032] In the above embodiment, it is preferable not to use a sheet containing a hydrophilic resin as a main component for the core sheet of the double-sided board and the inner layer of the multilayer board. Since such a sheet contains a relatively large amount of moisture, when used in the inner layer of a multilayer board, moisture is not diffused to the outside during thermocompression bonding, and the liquid crystal polymer film in the vicinity may be brittle. Because there is. Examples of hydrophilic resins include polyimide resins and polyetherimide resins. However, such influence is smaller than that given to the surface liquid crystal polymer film by a polyimide sheet or the like as a release material.

[0033] Preferably, all the insulating sheets are made of a thermoplastic resin, and can be composed of a liquid crystal polymer film from the viewpoint of electrical characteristics and the like because thermocompression bonding can be performed without using an adhesive. Is preferred.

[0034] The liquid crystal polymer film used in the present invention contains a liquid crystal polymer as a main component. Here, “as the main component” can be defined as the proportion of the liquid crystal polymer in the entire film being 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably Is 90% by mass or more. In particular, it is preferable that the liquid crystal polymer film of the present invention has substantially only a liquid crystal polymer. This is because the liquid crystal polymer is excellent in low water absorption, heat resistance, electrical characteristics, and dimensional stability. Further, since the liquid crystal polymer is thermoplastic, thermocompression bonding is possible without using an adhesive, and the productivity of the circuit board can be improved. Not using an adhesive is also significant in terms of reducing the dielectric constant and dielectric loss. Here, “substantially” means that everything except unavoidable impurities is composed of a liquid crystal polymer.

[0035] As the liquid crystal polymer constituting the liquid crystal polymer film, for example, there is a thermopick liquid crystal polymer that exhibits liquid crystallinity in a molten state. In the present invention, a thermopick pick liquid crystal polymer is suitable, and more specifically, the thermopick pick liquid crystal polyester is thermotropic. Prefer liquid crystal polyester amide.

[0036] Thermopick-pick liquid crystal polyester (hereinafter simply referred to as "liquid crystal polyester"!) Is synthesized, for example, mainly from an aromatic dicarboxylic acid and a monomer such as aromatic diol or aromatic hydroxycarboxylic acid. An aromatic polyester that exhibits liquid crystal properties when melted. A typical example is type I [formula (1)] synthesized from norhydroxybenzoic acid (PHB), terephthalic acid, and 4,4'-biphenol. PHB and 2,6-hydroxynaphtho Π-type synthesized from acids [Formula (2)], PHB, terephthalic acid, and ΠΙ-type synthesized from ethylene glycol (Formula (3)).

[0037] [Chemical 1]

[0038] As the liquid crystal polymer according to the present invention, for example, as long as it exhibits liquid crystallinity (particularly, thermo-mouth-pick liquid crystallinity), for example, a unit represented by the above formulas (1) to (3) is mainly used (for example, liquid crystal polymer). It may be a copolymer type polymer having 50 mol% or more in one whole constituent unit and having other units. Examples of the other unit include a unit having an ether bond, a unit having an imide bond, and a unit having an amide bond.

[0039] In obtaining the liquid crystal polymer film, various known methods may be employed depending on the resin constituting the liquid crystal polymer film. In addition, as a film using the above exemplified liquid crystal polyester particularly suitable in the method of the present invention, for example, “BIAC (registered product) manufactured by Japan Gore-Tex Co., Ltd. Commercially available products such as “registered trademark” ”can be used.

[0040] The liquid crystal polyester amide corresponds to the above liquid crystal polyester having an amide bond as another unit, and examples thereof include those having a structure of the following formula (4). For example, in formula (4), it is known that the molar ratio of s unit, t unit and u unit is 70Z15Z15.

[0041] [Chemical 2]

( Four )

5 t U

[0042] When the liquid crystal polymer film of the present invention contains a polymer other than the liquid crystal polymer, the polymer may be merely mixed with the liquid crystal polymer or may be chemically bonded. Examples of such an alloy polymer include polymers having a melting point of 220 ° C or higher, preferably 280 to 360 ° C, such as polyetheretherketone, polyethersulfone, polyimide, polyetherimide, polyamide, polyamideimide. And powers such as polyarylate are not limited to these. The mixing ratio of the liquid crystal polymer and the alloying polymer is not particularly limited, but for example, the mass ratio is preferably 50:50 to 90:10, more preferably 70:30 to 90:10. Polymer alloys including liquid crystal polymers can also possess superior properties due to liquid crystal polymers.

[0043] In the liquid crystal polymer film, it is preferable that the linear expansion coefficient in a direction parallel to the film plane is adjusted to 25 ppmZ ° C or less. More preferably, it is 21 ppmZ ° C or less. The lower limit of the linear expansion coefficient of the liquid crystal polymer film is desirably 8 ppmZ ° C. The linear expansion coefficient of the liquid crystal polymer film is from instrumental analysis (TMA method, Thermal Mechanical Analysis), and the specimen width is 4.5 mm, the distance between chucks is 15 mm, the load is lg, and the temperature rises from room temperature to 200 ° C. After cooling (heating rate: 5 ° CZ minutes), cooling rate: 5 ° CZ, when cooling at 5 ° CZ minutes, the value obtained from the dimensional change of the specimen measured between 160 ° C and 25 ° C Yes, for example, the linear expansion coefficient in the MD direction of the film (traveling direction during film production) and the linear expansion coefficient in the TD direction (direction orthogonal to the MD direction) need only satisfy the above range. [0044] The thickness of the liquid crystal polymer film is not particularly limited, but 10 μm force and 1000 μm are preferable. If it is less than 10 m, the strength may be insufficient, and it may be difficult to make a film exceeding 1000 / zm.

[0045] In the following, each step of the method of the present invention will be described with reference to FIG. 1. FIG. 1 is merely an example, and the scope of the present invention is not limited to this.

First, a circuit pattern is formed by a conductor on one or both surfaces of an insulator sheet (core sheet) constituting the circuit pattern sheet 1 in accordance with a conventional method. The type of insulating material for the circuit pattern sheet is not particularly limited, and conventional ones can be used. Preferably, a liquid crystal polymer film is used.

[0047] Examples of the conductor for forming the circuit pattern include copper, aluminum, gold, silver, and alloys mainly composed of these metals. For the circuit pattern, a conventional method can be used, for example, etching is performed after a thin film having a metallic force is provided on a circuit pattern sheet. As a method for forming a metal thin film, in addition to a method of bonding an insulator sheet and a metal plate (including metal foil, metal film, etc.), a vacuum deposition method, a sputtering method, an ion plating method, Methods such as plating and CVD can also be used.

[0048] When a thermoplastic resin is used as the insulator sheet of the circuit pattern sheet 1, the method of bonding the metal plates is preferably a heat-sealing method. As the heat fusion method, the surface of the thermoplastic resin is softened by heating and a metal plate is laminated thereon and then cooled, or an insulator sheet and a metal plate are stacked and heated between a pair of heated rolls. It is possible to adopt a method of heat-sealing through a heat sink and then cooling.

[0049] Further, if a metal plate such as a metal foil having a roughened surface on the side in contact with the insulator sheet is used, the adhesion between the insulator sheet and the metal plate can be further enhanced.

[0050] In the method of the present invention, after a metal layer is provided on one or both surfaces of an insulator sheet, a desired circuit pattern is formed by etching. The metal layer forming the circuit pattern may be a single layer or a laminate of two or more metal layers.

[0051] In the embodiment shown in FIG. 1, the force in which the cover layer 2 is provided on the circuit pattern sheet 1 In the present invention, at least one cover layer 2 is composed of a liquid crystal polymer film. Liquid crystal polymer This is to effectively utilize one excellent low water absorption, heat resistance and dimensional stability. Another reason is to exhibit the characteristics of a fluorine-based porous film as a release material that does not cause brittleness of the liquid crystal polymer film present on the surface during thermocompression bonding. If a plurality of non-thermoplastic resin is used as a part of the sheet constituting the laminate and it is necessary to bond them to each other, use an adhesive or the like in advance. . However, by devising the arrangement of the liquid crystal polymer film, it is possible to perform thermocompression bonding without using an adhesive in the next process. As a result, it is possible to prevent the electrical characteristics from being deteriorated by the adhesive, which can simplify the manufacturing process. Further, if all the insulator sheets are made of a liquid crystal polymer film, it is possible to obtain a circuit board that is particularly excellent in electrical characteristics such as low dielectric constant and low dielectric loss.

[0052] Also, from a laminate in which a circuit pattern is formed on one or both sides of a liquid crystal polymer film and a liquid crystal polymer film is disposed as a cover layer on the circuit pattern, only the liquid crystal polymer film is used as a sheet and the number of sheets laminated Therefore, a flexible circuit board with particularly excellent electrical characteristics can be manufactured.

[0053] In order to improve the adhesion of the surfaces in contact with each other in each sheet to be laminated, it is preferable to perform a surface treatment using ultraviolet rays or plasma.

Next, the laminate is thermocompression bonded by a thermocompression bonding apparatus. The conditions at the time of thermocompression bonding may be according to a conventional method. For example, the pressure may be 0.1 to: LOMPa and the time may be about 1 to 30 minutes. The thermocompression bonding temperature is preferably a temperature at which the liquid crystal polymer is sufficiently soft, but if it exceeds the melting point, the resin may flow due to pressure. From such a viewpoint, it is preferable that the liquid crystal polymer to be used has a temperature in which the elastic modulus measured in the tensile mode of the DMA method (Dynamic Mechanical Analysis) is in the range of 1Z10 to 1Z1000 in the room temperature range. The specific temperature is about 200 to 350 ° C depending on the type of liquid crystal polymer used.

[0055] The type of the thermocompression bonding apparatus is not particularly limited. For example, a flat plate press, a continuous belt press, a roll laminator, or the like can be used. In these, since a water | moisture content can be removed efficiently, a vacuum type flat plate press can be used suitably.

[0056] When a ceramic sheet is used as the core sheet and a liquid crystal polymer film is used as the cover sheet, heating and thermocompression bonding may be considered by heating only from the liquid crystal polymer film side. available. However, in order to improve the heat uniformity, it is preferable to perform double-sided force heating even in such a case.

[0057] In addition, when a liquid crystal polymer film is provided on one surface and a sheet containing hydrophilic resin as a main component is used on the other surface, a fluorine-based porous material as a release material is also provided on the hydrophilic resin sheet side. It is preferable to use a quality film. This is in order to reduce the influence on the liquid crystal polymer film in the vicinity by dissipating the moisture of the hydrophilic resin sheet to the outside.

[0058] In the present invention, at least a liquid crystal polymer film is used as a surface sheet, and the liquid crystal polymer film is required to be thermocompression bonded. The insulating layer is not only a liquid crystal polymer film but also an thermoplastic resin. In the production of a multilayer board having a sheet, generally, the inner layer can be thermocompression bonded together with the liquid crystal polymer film on the surface at a time.

[0059] When a circuit board is manufactured by thermocompression bonding, a release material having high heat resistance is required in order to prevent fusion between the thermocompression bonding apparatus and the thermoplastic resin. Therefore, polyimide has been conventionally used as a mold release material. However, as described above, a high temperature of 200 to 350 ° C. is required when the liquid crystal polymer film is hot-pressed. Therefore, when a release material such as polyimide that has high water retention and hydrophilicity and no air permeability is used, the molecules that make up the liquid crystal polymer film on the surface are exposed to high temperatures in the presence of water derived from polyimide. It will be hydrolyzed. This was a cause of deteriorating the durability of the circuit board.

[0060] Further, during thermocompression bonding, the pressure applied to the circuit pattern sheet becomes uneven due to the unevenness of the circuit pattern. As a result, circuit pattern flow and partial adhesion failure due to partial pressure failure occur. Therefore, conventionally, a cushioning material has been used. However, when both the mold release material and the cushioning material are used, the circuit pattern may be disturbed especially when a fine circuit board is manufactured. There was a risk of transfer onto the surface of the circuit board.

[0061] The present invention has been completed after recognizing these problems of the prior art, and is the largest in that a fluorine-based porous film is used as a release material in thermocompression bonding of a liquid crystal polymer film. Has characteristics. Fluorine-based porous film contains almost no water due to its manufacturing conditions and high hydrophobicity, and it can release liquid-derived polymer-derived water to the outside. The hydrolysis reaction during thermocompression bonding can be suppressed. In addition, since the fluorine-based porous film has high cushioning properties, it can function as a release material as well as a buffer material.

[0062] Examples of the resin constituting the fluorinated porous film include polytetrafluoroethylene (PTFE), PTFE-perfluoroalkyl butyl ether copolymer, PTFE-hexafluoropropylene. Examples include copolymers and PTFE-ethylene copolymers. Among these, expanded porous polytetrafluoroethylene (EPTFE), in which PTFE is preferred, is preferably used. Conventional methods can be used as a film forming method and a porous method for these resin.

[0063] The thickness of the fluorine-based porous film is not particularly limited, but may be, for example, 50-500 μm. If it is above, it has sufficient strength as a mold release material, and there is no possibility of breaking when the circuit board force is peeled off after heat-sealing, and also a force capable of exhibiting sufficient cushioning properties. On the other hand, if it exceeds 500 m, it is disadvantageous in terms of cost.

[0064] The porosity of the fluorine-based porous film is not particularly limited, but is preferably 60 to 98%, more preferably 70 to 90%. If it is less than 60%, the pores may be crushed during thermocompression bonding, making it difficult to release moisture. If it exceeds 98%, the strength will be insufficient, and the liquid crystal polymer will flow into the pores and will be difficult to peel off. There is a force that may be.

[0065] A metal plate is provided between the fluorine-based porous film and the thermocompression bonding section of the thermocompression bonding apparatus in order to improve the maintainability of the apparatus and at the same time improve the quality of the circuit board after thermocompression bonding. May be. Even if both a fluorine-based porous film and a metal plate are used, it will not cause paper transfer.

[0066] After thermocompression bonding of the laminate using the fluorine-based porous film, the laminate that is still covered with the fluoroporous film is taken out with a thermocompression bonding apparatus and cooled sufficiently. The system porous film is peeled off.

[0067] When the circuit is exposed on the outermost surface, a solder resist layer may be provided in accordance with a conventional method in order to prevent bridging of the conductive portion and protect the circuit surface after the thermocompression bonding of the liquid crystal polymer film.

[0068] The circuit board obtained by the above method is composed of a liquid crystal polymer film as a constituent element thereof. The brittleness at the time of thermocompression bonding is suppressed, and the durability is remarkably improved. Therefore, not only the occurrence of defects during manufacturing is suppressed, but also damage to the substrate itself and circuits in actual use is reduced. In particular, when a flexible circuit board is produced by the method of the present invention, the brittleness of the liquid crystal polymer film, which is the main component, is remarkably suppressed, so that the folding resistance and toughness of the circuit board are improved. Durability is remarkably improved. Therefore, when the flexible circuit board according to the present invention is inserted into a compact device such as a mobile phone or a personal computer, the occurrence of damage to the board itself or the circuit is reduced, and the life of the circuit board itself is extended. In this respect, the circuit board of the present invention is very useful as it can meet the demand for longer life of electronic devices in recent years.

[0069] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as well as the present invention. It is also possible to carry out with addition, and they are all included in the technical scope of the present invention.

Example

Production Example 1 Production of a liquid crystal polymer film circuit board by the method of the present invention

Double-sided copper clad with liquid crystal polymer film (Japan Gotex Corp., BIAC CC BCO 50F-B12B17, substrate thickness: 50 / zm, copper foil thickness: m, liquid crystal polymer melting point: 310.C) Etching was performed to form a linear circuit pattern with a line Z space of 100Z100 μm. Separately, one side of a liquid crystal polymer film (BIAC BC050F, manufactured by Japan Gore-Tex Co., Ltd., thickness: 50 m) was subjected to ultraviolet ray treatment with an integrated light amount of 4, OOOmjZcm ² using a low-pressure mercury lamp. The liquid crystal polymer film was laminated on the copper-clad plate with the ultraviolet-treated surface as an adhesive surface. Furthermore, stretched porous PTFE film (manufactured by Japan Gore-Tex, HRCF-090) shown in Table 1 is placed on both sides as a release material, and thermocompression bonding equipment (Kitakawa Seiki Co., Ltd., vacuum hot 'cold press VH3-1377) Was thermocompression bonded at a temperature of 285 ° C. and a pressure of 3 MPa for 5 minutes. The obtained laminated film was cut into a 15 × 130 mm rectangle to obtain a test piece.

[0071] Comparative Production Example 1 A laminated film was produced in the same manner as in Production Example 1 except that a polyimide film shown in Table 1 (manufactured by Toray DuPont, Kapton 200EN) was used instead of the stretched porous PTFE film as a release material. Sarakuko cut the laminated film to obtain a test piece similar to Production Example 1.

[0072] Comparative Production Example 2

Three layers of stretched porous PTFE film (manufactured by Japan Gore-Tex Co., Ltd., HR CF-090) used in Production Example 1 above are stacked and a thermocompression bonding device (Kitakawa Seiki Co., Ltd., vacuum hot 'cold press VH 3-1377) A non-porous PTFE film was obtained by thermocompression bonding at a temperature of 330 ° C and a pressure of 4 MPa for 5 minutes.

[0073] The obtained non-porous PTFE film was used as a release material in place of the stretched porous PTFE film in the method of Production Example 1 to produce a laminated film. Further, the laminated film was cut to obtain a test piece similar to Production Example 1.

[0074] Test Example 1 Folding resistance test

In accordance with JIS C6471, the specimens obtained in Production Example 1 and Comparative Production Examples 1 and 2 were subjected to a folding resistance test. For details, attach the test piece to the MIT testing machine (MIT-D, manufactured by Toyo Seiki Seisakusho), and set the direction parallel to the linear circuit (MD) until the film breaks under the condition of R = 0.4 and load: 500g. The number of folds in the orthogonal direction (TD) was measured. In addition, the presence or absence of deformation of the circuit pattern due to thermocompression bonding before the test and the presence or absence of peeling of the circuit surface protective layer (the outermost liquid crystal polymer film) after the test were confirmed. The results are shown in Table 1.

[0075] [Table 1]

As a result, when a polyimide film or a fluorine-based non-porous film was used as a release material, the circuit pattern was deformed before the test. This is Polly The cushioning properties of the mid film and non-porous PTFE film are inadequate! This is considered to be due to the uneven pressure applied to the circuit surface during thermocompression bonding. In addition, peeling of the circuit surface protective layer was observed after the test. This is thought to be due to non-uniform pressure as well as circuit pattern deformation.

On the other hand, when the stretched porous PTFE film was used as a release material, neither pattern deformation nor peeling of the circuit surface protective layer was observed. This is due to the fact that the stretched porous PTFE film has excellent tackiness, and the pressure during thermocompression bonding was uniform. In addition, the folding resistance of the laminate when using the stretched porous PTFE film as a release material is significantly improved as compared with the case where another material is used as the release material. This is because the stretched porous PTFE film contains almost no water, and the ability to be porous has also suppressed the hydrolysis of the liquid crystal polymer by releasing the water derived from the liquid crystal polymer film during thermocompression bonding. It's a good night.

Claims

The scope of the claims

[1] A method of manufacturing a circuit board,

Among the insulating sheets constituting the circuit board, a liquid crystal polymer film is used as at least one surface sheet, and a fluorine-based porous film is used as a release material in thermocompression bonding the liquid crystal polymer film. A method of manufacturing a circuit board.

[2] The method for producing a circuit board according to [1], wherein the liquid crystal polymer film is one having substantially only a liquid crystal polymer.

[3] The method for manufacturing a circuit board according to claim 1 or 2, wherein each of the insulator sheets of the circuit board is composed of a liquid crystal polymer film.

[4] The method for producing a circuit board according to any one of claims 1 to 3, wherein a circuit pattern is formed on one or both sides of the liquid crystal polymer film, the liquid crystal polymer film is disposed on the circuit pattern, and thermocompression bonding is performed.

[5] The method for producing a circuit board according to any one of claims 1 to 4, wherein a stretched porous polytetrafluoroethylene film is used as the fluorine-based porous film.

[6] A circuit board manufactured by the method according to any one of claims 1 to 5 and having excellent durability.