JP2008198732A - Adhesive film for circuit board, coverlay and circuit board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive film having an adhesive layer thinned as much as possible, having surface smoothness and capable of preventing an adhesive material from flowing to an opening of a terminal portion of a wiring pattern in a multilayer circuit board, and to provide a coverlay film. <P>SOLUTION: Adhesive layers (102, 103, ...) having different flowability are laminated in at least two or more layers as an adhesive layer 104 of the adhesive film 105 and the coverlay film 100, and a surface (103 side) having less flowability of the adhesive layer 104 is provided on the wiring pattern. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an adhesive film and a coverlay film used for a circuit board.

  A flexible circuit board has a circuit wiring pattern formed on a copper-clad laminate with a copper foil provided on the surface of a flexible insulating base material. On this circuit wiring pattern, an electronic component such as a circuit component or an external substrate, or a circuit It is manufactured by forming a surface protective layer having an opening at a portion where a terminal for connection to the substrate is formed, punching it out with a mold or the like, and processing the outer shape. Moreover, a multilayer circuit board is manufactured by laminating each circuit board using an adhesive film.

  Here, the surface protective layer is a flexible insulating film having an adhesive layer on one side and is called a coverlay film. An opening is formed by punching this with a mold or the like, and this coverlay film is bonded onto the circuit wiring pattern to form a surface protective layer.

  In the production of a multilayer circuit board, an adhesive film and a coverlay film are attached to the multilayer circuit board using a method such as vacuum pressing. An IC chip is mounted on the surface of the multilayer circuit board, but due to the increase in size of the chip and the change to the BGA type, the adhesive layer of the adhesive film and coverlay film has a circuit embedding property and a surface smoothness after pressing. Required.

  A cover lay film is used as the inner layer of the multilayer circuit board. However, if the cover lay film surface has irregularities after pressing, the surface of the multilayer board is also affected, so surface smoothness is also important in the cover lay film.

  With the miniaturization of circuit wiring patterns, it is difficult for the adhesive layer to sufficiently embed between the wirings. In addition, even if embedded, there are not a few uneven steps on the surface of the adhesive layer, and repeated stacking causes deterioration of positional accuracy, warping of the substrate, variations in each layer, and the like. In order to flatten the unevenness, a process such as polishing is required, and the manufacturing method is limited.

  In the multilayer circuit board manufactured by such a manufacturing process, it is preferable to use an adhesive having a high flow property for the adhesive layer of the adhesive film and the coverlay film in order to obtain the surface smoothness.

  However, using an adhesive with high flowability improves the surface smoothness of the multilayer circuit board, but the adhesive for the adhesive film and coverlay film flows out to the opening of the wiring pattern terminal part, etc. There are problems such as difficult or impossible operations such as attaching and plating.

  On the other hand, if an adhesive with low flowability is used, the adhesive of the adhesive film and coverlay film will not flow out to the opening part of the wiring pattern terminal part etc., but the surface smoothness of the multilayer circuit board cannot be obtained. In addition, there is a problem that a predetermined adhesive strength cannot be obtained because a gap or a void is partially generated due to insufficient penetration between the wirings.

  In order to suppress the flow of the adhesive material to the opening portion of the wiring pattern terminal portion and the like with excellent surface smoothness after pressing as much as possible, for example, adhesive layers having different flow properties as adhesive layers of adhesive films and coverlay films A method of laminating two or more layers has been proposed (see, for example, Patent Document 1).

In addition, in a multilayer circuit board, a method has been proposed in which at least two adhesive layers having different flowability are stacked as an interlayer adhesive layer, and an adhesive layer having a low flowability of the adhesive layer is provided on the wiring pattern. (For example, refer to Patent Document 2). Specifically, in the invention described in Patent Document 2, the circuit pattern is formed in a multilayer circuit board that is laminated by adhering a layer having a surface on which the circuit pattern is formed and another layer with an adhesive layer. A laminar body having a first adhesive layer is formed by heat laminating a low flowable adhesive on the other surface, and a high flowable adhesive is heat laminated on the surface in contact with the other layer. A laminate having an adhesive layer is formed, and then these laminates are further bonded together by thermal lamination to form an interlayer adhesive layer to obtain a multilayer circuit board.
JP 2003-198107 A JP 2006-073934 A (paragraphs 0016 to 0021, FIG. 2)

  However, the technique described in Patent Document 1 has a problem that sufficient surface smoothness of the multilayer circuit board cannot be obtained when an adhesive layer having a relatively high flow property is provided on the wiring pattern.

  In the method described in Patent Document 2, the surface smoothness after pressing (thermal lamination) at the time of forming the second adhesive layer is excellent, and the wiring pattern terminal portion and the like are formed at the time of forming the first adhesive layer. Although it is possible to obtain the effect of suppressing the flow of the adhesive material to the opening portion of the film as much as possible, it is necessary to make the first adhesive layer provided on the pattern larger than the pattern thickness. There was a problem that could not be made.

  Therefore, in view of the above problems, an object of the present invention is excellent in surface smoothness, and can suppress the flow of an adhesive material to an opening portion such as a wiring pattern terminal portion as much as possible, and has a thinner adhesive layer. An adhesive film for a circuit board, a coverlay, and a circuit board using the same are provided.

  In order to achieve this purpose, it is excellent in surface smoothness and can suppress the flow of the adhesive material to the opening part such as the wiring pattern terminal part as much as possible, and as a result of earnestly examining the demand for a thinner adhesive layer, In the multilayer circuit board, the present inventors have invented an adhesive film and a coverlay film that have two or more adhesive layers and have a wiring pattern with a surface having a small flowability.

  That is, the present invention lies in an adhesive film comprising an inclined arrangement in which at least two adhesive layers having different flow properties are laminated.

  Furthermore, the present invention comprises an adhesive film layer formed by laminating at least two adhesive layers having different flow properties on one surface of a film substrate, and the flow property in the adhesive film layer is the film. The cover lay film is characterized in that the cover lay film is formed so as to be inclined (in the thickness direction of the adhesive film) so as to decrease from the base material side to the outer side (the adhesive film layer surface side).

  According to the present invention, by laminating at least two adhesive layers having different flow properties as an adhesive layer of an adhesive film and a coverlay film, and providing a surface having a small flow property of the adhesive layer on the wiring pattern. It is possible to provide an adhesive film and a coverlay film that are excellent in surface smoothness after pressing and that can suppress the adhesive material from flowing out to an opening portion such as a wiring pattern terminal portion as much as possible.

  Furthermore, in the present invention, an adhesive layer having a low flow property is obtained by forming an adhesive layer that is inclined in the thickness direction of the film so that the flow property decreases from the film substrate side to the outside (film surface). Even if the thickness is less than the pattern thickness, it is excellent in surface smoothness after pressing, and the adhesive material is prevented from flowing out to the opening part such as the wiring pattern terminal part as much as possible. It is possible to provide an adhesive film for a circuit board having a layer), a coverlay film, and a circuit board using the same.

  The adhesive film for a circuit board according to the present invention is characterized by having an inclined arrangement in which at least two adhesive layers having different flow properties are laminated.

  Further, the circuit board coverlay film of the present invention is provided with the circuit board adhesive film layer of the present invention formed by laminating at least two adhesive layers having different flow properties on one side of a film base material. It is a thing characterized by being inclinedly arranged so that the flow property in the said adhesive film layer may become small from the said film base material side to an outer side.

  Furthermore, the multilayer circuit board of the present invention is formed by laminating at least two adhesive layers having different flow properties, and is arranged so that the smaller flow property is on the circuit pattern side. Is.

  Furthermore, the flexible circuit board of the present invention is characterized by using the above-described circuit board cover lay film.

  Here, the adhesive layers having different flow properties used in the adhesive film for circuit boards, the cover lay film for circuit boards, the multilayer circuit board, and the flexible circuit board of the present invention include a plurality of adhesive layers having different flow properties. Can be obtained by an inclined arrangement.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view schematically showing an adhesive film for a circuit board according to the present invention. FIG. 2 is a schematic cross-sectional view schematically illustrating a circuit board cover lay film of the present invention and a configuration of a multilayer circuit board on which a counterpart circuit pattern to which the circuit board cover lay film is applied is formed. It is.

  As shown in FIGS. 1 and 2, in the configuration of the adhesive layer 104 composed of a plurality of layers having different flow properties, the thickness of the adhesive layer 102 having a large flow property is 25 μm or less, preferably 15 to 25 μm. . When the thickness of the adhesive layer 102 having a large flowability exceeds 25 μm, it is difficult to control the flowability. On the other hand, the lower limit of the thickness of the adhesive layer 102 having a large flow property is not particularly limited, but it is not dependent on the circuit pattern and is intended to obtain the surface smoothness of the circuit board. 15 μm or more is desirable.

  In addition, the adhesive layer 103 having a low flow property is combined with the adhesive layer 102 having a high flow property in consideration of the pattern embedding property, and if it is equal to or larger than the thickness of the conductor (the conductive (or circuit) pattern 201 in FIG. 2). What is necessary is just to employ | adopt suitably by the conductive (or circuit) pattern 201 thickness. For example, with respect to a conductive (or circuit) pattern 201 formed of copper foil (thickness 35 μm; 1 ounce), an adhesive layer 104 in which an adhesive layer 103 having a low flow property and an adhesive layer 102 having a high flow property are combined. If the total thickness of the film is 35 μm or more, and if the copper plating is formed on the copper foil with a thickness of 15 μm, the thickness is 50 μm or more. Thereby, even if the adhesive layer 103 having a small flow property is less than the thickness of the pattern 201, the surface smoothness after pressing is excellent, and the flow of the adhesive material to the opening portion such as the wiring pattern terminal portion is suppressed as much as possible. A circuit board adhesive film 105 having a thin adhesive layer (adhesive layer 104 in which two or more layers are laminated), a coverlay film 100, and a multilayer circuit board or flexible circuit board 300 using the same can be provided. The thickness of the adhesive layer 104 may be equal to or greater than the thickness of the conductive (or circuit) pattern 201 as described above, but preferably the thickness of the conductive (or circuit) pattern 201 is in the range of 2 to 20 μm. Is desirable. If the thickness of the conductive (or circuit) pattern 201 is less than +2 μm, there is a concern that air remains around the circuit. On the other hand, when the thickness of the conductive (or circuit) pattern 201 exceeds +20 μm, which is one of the operational effects (objects) of the present invention, the adhesive film for the circuit board having the thinner adhesive layer 104, the coverlay, It may be difficult to provide a circuit board using the circuit board.

  As shown in FIGS. 1 and 2, the adhesive layer 104 having different flow properties (consisting of a plurality of layers) according to the present invention includes two adhesive layers 102 and 103 having different flow properties, respectively, and a plurality of adhesive layers. It can be obtained by an inclined arrangement in which an adhesive layer is laminated. A specific method for reducing the flow property of the adhesive layer 103 (not shown in the third and subsequent layers) after the second layer relative to that of the adhesive layer 102 as the first layer will be described below. .

  The circuit board adhesive film 105 is formed by first applying a thermosetting adhesive on one surface of a release-treated paper, a polyethylene terephthalate (hereinafter, also referred to as PET) film-based separator, and drying. A first adhesive layer 102 is provided.

  Next, a thermosetting adhesive is similarly applied to another separator as the second adhesive layer 103 and dried. The adhesive layer 103 as the second layer is, for example, dried at a temperature higher or longer than the drying conditions of the first adhesive layer 102, or after drying under the same conditions as the first adhesive layer 102, Furthermore, by using at least one of the method of performing additional heat treatment, the method of changing the ratio of the resin, the inorganic filler, and the curing agent in the adhesive composition, the adhesive layer has a smaller flowability than the first layer. 103. Adhesion for circuit boards having an adhesive layer 104 composed of a plurality of layers having different flow properties by an inclined arrangement in which an adhesive layer 103 as a second layer is laminated on the first adhesive layer 102 using a laminator or the like. A film 105 can be obtained (FIG. 1 does not show a release-treated paper, a film-based separator, or the like).

  In order to obtain a suitable adhesive film outflow amount (unit: g / 10 min) as shown below, for example, the flow conditions of the adhesive layers 102 and 103 are adjusted by changing the drying conditions as shown in the examples. As the drying conditions in this case, it is difficult to define uniquely because it varies depending on the type of adhesive and the like, but the following conditions are preferable.

  That is, in the case of forming a first large flowable adhesive layer, after applying a thermosetting adhesive on the separator or film substrate, using a hot air dryer or the like, The drying is preferably performed at 90 to 110 ° C. for 2 to 7 minutes, preferably 3 to 6 minutes. When the temperature is lower than 70 ° C., the adhesive cannot be sufficiently dried. When the temperature exceeds 130 ° C., there is a possibility that the lower limit of the desired flowability is not reached. If it is less than 2 minutes, the adhesive cannot be sufficiently dried, and if it exceeds 7 minutes, there is a possibility that it falls below the lower limit of the desired flowability.

  In the case of forming a second small flowable adhesive layer, after applying a thermosetting adhesive on the separator or film substrate, using a hot air dryer or the like, preferably at 70 to 130 ° C., preferably Is dried at 90 to 110 ° C. for 2 to 7 minutes, preferably 3 to 6 minutes. When the temperature is lower than 70 ° C, the adhesive cannot be sufficiently dried. When the temperature is higher than 130 ° C, the lower limit of the desired flow property may be lost. If it is less than 2 minutes, the adhesive cannot be sufficiently dried, and if it exceeds 7 minutes, there is a possibility that it falls below the lower limit of the desired flowability. When the drying conditions are the same as the drying conditions for forming the first large-flowing adhesive layer, or when the drying conditions are low or short, 70 to 130 ° C., preferably 90 to 110 ° C. is additionally provided. By performing the heat treatment for 2 to 15 minutes, preferably 3 to 12 minutes, the overall drying condition when forming the second small flowable adhesive layer is the first large flowable adhesion. What is necessary is just to adjust so that it may become high temperature or long-lasting than the drying conditions at the time of forming an agent layer. When the temperature is lower than 70 ° C., the adhesive cannot be sufficiently dried. When the temperature exceeds 130 ° C., there is a possibility that the lower limit of the desired flowability is not reached. If it is less than 2 minutes, the adhesive cannot be sufficiently dried, and if it exceeds 15 minutes, the desired flowability may be lower than the lower limit. However, in the present invention, these drying conditions are not limited at all, and depending on the type of the thermosetting adhesive, the following preferable adhesive film outflow amount can be satisfied even if it is outside this range. Sometimes you can. Therefore, it can be said that it is desirable to conduct a preliminary experiment or the like in advance to obtain conditions satisfying the following preferable adhesive film outflow. Further, even when the flowability of the adhesive layers 102 and 103 is adjusted by a method other than the drying condition, it is necessary to perform a preliminary experiment or the like in advance to obtain a condition that satisfies the following preferable adhesive film outflow amount. This is desirable.

  The obtained adhesive film 105 for circuit boards was thermocompression bonded at a temperature of 170 ° C., a pressure of 9.8 MPa, and a time of 1 minute, and degreased with methyl ethyl ketone (hereinafter also referred to as MEK). Diameter 1.0 mm, Length 1.0 mm, Material The flow rate of the adhesive layer 102 of the first layer is 70 to 120 g / 10 minutes, preferably 80 to 110 g / 10, when the flow rate of the adhesive film from the stainless steel die (unit: g / 10 minutes) is calculated as an index of flow properties. The flowability of the second adhesive layer 103 is preferably in the range of 10 to 50 g / 10 minutes, preferably 20 to 40 g / 10 minutes. It can be appropriately selected within a range where the flowability is smaller than that of the first adhesive layer 102. When there are three or more adhesive layers having different flow properties according to the present invention, the flow properties of the third or more adhesive layers may be smaller than the flow property of the second adhesive layer. Here, when the flow property of the first adhesive layer 102 is less than 70 g / 10 minutes, the surface smoothness of the circuit board cannot be obtained, and when it exceeds 120 g / 10 minutes, the adhesive flows out to the opening. The amount increases. On the other hand, when the flowability of the second adhesive layer 103 is less than 10 g / 10 minutes, sufficient adhesiveness as an adhesive cannot be obtained, and when it exceeds 50 g / 10 minutes, the adhesive is applied to the opening portion. The amount of flowing out increases.

  When producing the adhesive layer 102 of the first layer, instead of the separator, as shown in FIG. 2, by using a film (coverlay-structured base film) 101 serving as a coverlay film substrate, the flow property is A circuit board cover lay film 100 having adhesive layers 102 and 103 that become smaller from the film base 101 side to the outside (the adhesive film layer surface side = the adhesive layer 103 side) can be obtained.

  The thermosetting adhesive used for the adhesive layers 102 to 103 is not particularly limited. For example, (i) based on a rubber having flexibility, (ii) a thermosetting resin, (iii) And an adhesive containing (iv) a curing agent, (iv) an inorganic filler, and (v) other additives used as necessary.

  In addition, the solution of the adhesive composition used in the examples refers to a solution obtained by dissolving (or dispersing) each compounding component of the adhesive in (vi) an appropriate solvent.

(I) Rubber having flexibility (base component) As the rubber having the flexibility of the base component used in the thermosetting adhesive, generally used are acrylic rubber, nitrile rubber (hereinafter referred to as acrylonitrile butadiene rubber). Or styrene isoprene styrene block copolymer (hereinafter also referred to as SIS), preferably acrylic rubber containing carboxylic acid as a functional group.

  The acrylic rubber containing the carboxylic acid as a functional group is a vinyl monomer containing an acrylic acid alkyl ester (including a methacrylic acid ester, the same shall apply hereinafter) as a main component and a carboxylic acid as a functional group, and if necessary. A copolymer containing acrylonitrile, styrene and the like.

  Examples of the alkyl acrylate ester include ethyl acrylate (including ethyl methacrylate, the same applies hereinafter), propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, undecyl acrylate, Monomers such as lauryl acrylate, monomers having hydroxyl groups such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and allyl alcohol, and epoxy groups of epichlorohydrin modification products such as glycidyl acrylate and dimethylaminoethyl acrylate And the like. From these, one type or two or more types can be selected and used.

  Examples of the vinyl monomer containing the carboxylic acid as a functional group include, but are not limited to, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, and maleic anhydride. From these, one type or two or more types can be selected and used.

  A method for polymerizing the acrylic rubber is not particularly limited, and a general suspension polymerization method can be used. For example, a dispersant such as polyvinyl alcohol (hereinafter also referred to as PVA), azobisisobutyronitrile, and the like. A mixture of two or more of the above acrylic monomers is dropped into a liquid in which a polymerization initiator such as (AIBN) or lauryl peroxide (LPO) is dispersed in an aqueous medium and polymerized. The polymer is washed with purified water to remove impurities, washed with water and dried by heating to remove residual monomers and moisture. The number average molecular weight of the polymer is preferably about 50,000 to 500,000, more preferably 40000 to 400,000. In addition to the suspension polymerization method, for example, conventionally known polymerization methods such as emulsion polymerization, solution polymerization, and bulk polymerization can be used.

  The polymerization method for the flexible rubber (other than acrylic rubber) which is the base component of the thermosetting adhesive is not particularly limited, and a general suspension polymerization method is used. Etc. can be used. Further, the number average molecular weight of the obtained polymer (flexible rubber) is preferably about 50,000 to 500,000, more preferably 40000 to 400,000. In addition to the suspension polymerization method, conventionally known polymerization methods such as emulsion polymerization and bulk polymerization can be used.

  The compounding amount of the flexible rubber which is the base component of the thermosetting adhesive is determined from (ii) thermosetting resin, (iii) curing agent, and (iv) described later from the thermosetting adhesive. It is a residue obtained by subtracting the total amount of blending specified by the inorganic filler (further, other additive (v) blended as necessary). That is, the blending amount of the rubber having flexibility is in the range of 30 to 80 parts by weight, preferably 40 to 60 parts by weight with respect to 100 parts by weight of the total amount of the blending components of the adhesive. When the amount of the rubber having flexibility is less than 30 parts by weight, sufficient adhesion cannot be obtained, and when it exceeds 80 parts by weight, the heat resistance is lowered.

(Ii) Thermosetting resin The thermosetting resin used in the thermosetting adhesive is preferably an epoxy resin or a phenol resin. These may be used alone or in combination with an epoxy resin and a phenol resin.

  Here, the epoxy resin is a compound having two or more epoxy groups in the molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac. Type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F novolak type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, bifunctional Diglycidyl etherified products of phenols, diglycidyl etherified products of difunctional alcohols, hydrogenated products thereof and the like can be used. These compounds can be used alone or in combination of two or more. The amount of the epoxy resin is 10 to 100 parts by weight, preferably 100 parts by weight of rubber (base component of a thermosetting adhesive) having flexibility such as acrylic rubber containing carboxylic acid as a functional group. Is preferably 30 to 80 parts by weight. When the amount is less than 10 parts by weight, sufficient heat resistance cannot be obtained, and when the amount is more than 100 parts by weight, the peel adhesion strength decreases, which is not preferable.

  The phenol resin may be of a resol type, and the molecular weight, softening point, hydroxyl equivalent, etc. of the phenol resin are not particularly limited. The resol-type phenol resin is obtained by adding excess formaldehyde to phenol and reacting with an alkali catalyst. When the resol-type phenol resin is heated or an acid is added, the reaction proceeds at room temperature and self-condenses. Further, in the present invention, not only the self-condensation of phenol resin, but also reactivity with a rubber having flexibility (such as a base component of a thermosetting adhesive) such as an acrylic rubber containing a carboxylic acid as a functional group. Since it has, reflow solder heat resistance and volume resistance are improved. The blending amount of the phenol resin is 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of a flexible rubber (base of thermosetting adhesive) such as acrylic rubber. When the amount is less than 5 parts by weight, the crosslink density is lowered and sufficient reflow soldering heat resistance cannot be obtained. When the amount is more than 50 parts by weight, the storage stability in the B-stage state is impaired, and the peel adhesion strength is lowered. Cause problems.

  When the epoxy resin and the phenol resin are used in combination as the thermosetting resin, the mixing ratio is not particularly limited, but epoxy resin: phenol resin (mass ratio) = 30 to 300: 100, preferably It is in the range of 50 to 250: 100. If the epoxy resin is less than 30 parts by weight relative to 100 parts by weight of the phenol resin, sufficient heat resistance cannot be obtained. When the amount exceeds 300 parts by weight, the peel strength decreases, which is not preferable.

(Iii) Curing Agent The curing agent used for the thermosetting adhesive is a curing agent or curing catalyst for a thermosetting resin such as an epoxy resin. For example, aromatic polyamines, boron trifluoride amine complexes such as boron trifluoride triethylamine complex, imidazole derivatives such as 2-alkyl-4-methylimidazole and 2-phenyl-4-alkylimidazole, phthalic anhydride, Known acids such as organic acids such as merit acid, dicyandiamide, triphenylphosphine, diazabicycloundecene and hydrazine can be used. In addition, these hardening | curing agents and hardening catalysts may be used independently, and may use 2 or more types together as needed. In order to improve the storage stability at the B stage, it is preferable that the curing agent and the curing catalyst hardly react at room temperature.

  The compounding amount (addition amount) of these curing agents or curing catalysts is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of a thermosetting resin such as an epoxy resin. If the amount is less than 0.01 parts by weight, sufficient curing of the thermosetting resin such as an epoxy resin cannot be obtained, and the heat resistance of the solder is lowered. If the amount is more than 10 parts by weight, the peel adhesion strength is lowered and stored. This causes problems such as reduced stability.

(Iv) About Inorganic Filler The inorganic filler used in the thermosetting adhesive can be used as long as it is essentially electrically insulating, such as aluminum hydroxide and magnesium hydroxide. And metal oxides such as aluminum oxide and calcium oxide, silica, mica, talc, clay and the like. These can be used alone or in combination of two or more as required.

  The amount of the above inorganic filler is effective as acrylic rubber containing a carboxylic acid as a functional group (base component flexible rubber) + epoxy resin (thermosetting resin) + phenol resin (thermosetting resin). The amount is 10 to 100 parts by weight, preferably 20 to 80 parts by weight, based on 100 parts by weight of the total components. When the amount is less than 10 parts by weight, sufficient flame resistance cannot be obtained. When the amount is more than 100 parts by weight, problems such as a decrease in peel adhesion strength occur.

  The inorganic filler is adjusted to a particle size of 10 μm or less using a ball mill or the like (the particle size here refers to the maximum particle size). When the particle size of the inorganic filler is larger than 10 μm, when it is used as an adhesive film or a coverlay film, irregularities are generated on the film surface, and the peel adhesion strength, the solder heat resistance is lowered, and the appearance is impaired.

(V) Other Additives that may be Used as Needed In the above-described thermosetting adhesive, further, other additives that may be used as needed are within a range that does not impair the effects of the present invention. You may mix | blend inside. Specifically, for example, various silane coupling agents and the like can be appropriately mixed and used.

(Vi) About a suitable solvent Moreover, although it does not restrict | limit especially as a suitable solvent used in order to melt | dissolve (or disperse | distribute) each compounding component of the said adhesive agent, methyl ethyl ketone, toluene, DMF (N, N′-dimethylformamide), ethyl acetate, methanol, isopropyl alcohol, ethylene glycol and the like can be suitably used. In addition, the solvent may not be particularly used when it is in a solution form that can be suitably applied with only each component of the adhesive. In this case, the solvent is handled as a solution of adhesive = adhesive composition. be able to.

  As a compounding quantity of this solvent, it is 100-1000 weight part with respect to 100 weight part of total amounts of each compounding component of the said adhesive agent, Preferably it is the range of 200-600 weight part. When the amount of the solvent is 100 parts by weight, the viscosity of the adhesive solution is too high to be applied, and when it exceeds 1000 parts by weight, an adhesive layer having a desired thickness cannot be obtained.

  The release-based paper-based separator is not particularly limited. For example, the paper-based separator such as high-quality paper, kraft paper, roll paper, glassine paper, and the like such as clay, polyethylene, polypropylene, etc. A coating layer of a stopper is provided, and a silicone-based, fluorine-based, or alkyd-based release agent is coated on each coated layer, and polyethylene, polypropylene, ethylene-α-olefin copolymer, propylene -Various olefin films such as -α-olefin copolymer alone, and those obtained by applying the above release agent on a film such as polyethylene terephthalate, but the release force with the adhesive layer, silicone adversely affects the electrical properties For example, it is preferable to use polypropylene sealant on both sides of high-quality paper and use an alkyd release agent on it. Yes.

  The thickness of the release-based paper-based separator is not particularly limited, but is in the range of 50 to 150 μm, preferably 80 to 120 μm. When the thickness of the paper-based separator subjected to the release treatment is less than 50 μm, the strength as the separator is insufficient, and when it exceeds 150 μm, the curl may be increased when winding with a roll. .

  The PET film-based separator subjected to the release treatment is not particularly limited, and examples thereof include those using an alkyd release agent on a polyester film. Preferred polyesters used in the polyester film include polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, polybutylene terephthalate and its copolymer, polybutylene naphthalate and its copolymer, polyhexamethylene naphthalate and Mention may be made of the copolymers. These polyester films have the advantages that they generate less dust and generate less gas during heating.

  The thickness of the release-treated PET film-based separator is not particularly limited, but is in the range of 25 to 100 μm, preferably 38 to 75 μm. When the release-treated PET film-based separator has a thickness of less than 25 μm, it is difficult to remove when the separator is peeled off, and the workability is reduced. When the separator exceeds 100 μm, curling occurs when winding with a roll. May grow.

  Although it does not specifically limit as the flexible insulating film (coverlay structure base film) 101 used as the said coverlay film base material, For example, a polyimide film, PET film, a polyethylene naphthalate film etc. are mentioned.

  The thickness of the flexible insulating film (coverlay-constituting base film) 101 serving as the coverlay film substrate is not particularly limited, but is 4 to 50 μm, preferably 12 to 25 μm. If the thickness of the flexible insulating film (coverlay-constituting base film) 101 is less than 4 μm, the yield during coating is significantly reduced, and if it exceeds 50 μm, the thickness of the circuit board is unfavorable. .

  Moreover, in this invention, in order to form the adhesive bond layer 104 which consists of several layers (102,103, ...) from which flow property differs, the some adhesive agent from which flow property differs can be used. For example, an adhesive having a high flow property is used for the first adhesive layer 102, and an adhesive having a low flow property is used for the second adhesive layer 103, and the first and second adhesive layers are used. The adhesive film 105 having the adhesive layer 104 having different flow properties can be obtained by the inclined arrangement in which the layers 102 and 103 are laminated. Here, as the plurality of adhesives, those having different rubber / resin ratios of adhesive materials, or those having the same rubber / resin ratio but having different flow properties due to addition of additives and fillers, etc. It is done.

  The surface of the adhesive film 105 thus obtained with a low flowability (adhesive layer 103 side) or the adhesive surface of the coverlay film 100 (adhesive layer 103 side) is placed on the insulating substrate (lower substrate 203). By pasting on a required wiring pattern (conducting or circuit pattern) 201 formed on a metal layer portion (of the circuit board 200 configuration base film 202), it has excellent surface smoothness and an opening portion such as a wiring pattern terminal portion. Thus, the multilayer circuit board 300 having the thinner adhesive layer 104 can be obtained.

  That is, in the multilayer circuit board 300 of the present invention, as the adhesive layer 104, at least two adhesive layers having different flow properties such as an adhesive layer 102 having a high flow property and an adhesive layer 103 having a low flow property are used. It is characterized by being laminated and arranged such that the one with the lower flowability (adhesive layer 103) is on the pattern (201) side. The flexible circuit board 300 of the present invention is characterized by using the circuit board coverlay film 100 of the present invention. That is, even in the flexible circuit board 300 of the present invention, the adhesive layer 104 includes at least two adhesive layers having different flow properties, such as the adhesive layer 102 having a high flow property and the adhesive layer 103 having a low flow property. It is characterized by being laminated and arranged such that the one with the lower flowability (adhesive layer 103) is on the pattern (201) side. In other words, in the flexible circuit board 300 of the present invention, at least two adhesive layers having different flow properties are laminated, such as the adhesive layer 102 having a high flow property and the adhesive layer 103 having a low flow property. The adhesive film layer 104 is provided, and is disposed so as to be inclined so that the flowability in the adhesive film layer 104 decreases from the film substrate 100 side to the outside (pattern 201 side = adhesive layer 103 side). It can be said that it is characterized by. Therefore, it can be said that the circuit board 200 is a component used for a multilayer circuit board or a flexible circuit board.

  Here, the surface of the adhesive film 105 with low flowability (adhesive layer 103 side) or the adhesive surface of the coverlay film 100 (adhesive layer 103 side) is placed on the insulating substrate (lower substrate 203) (circuit board 200). The conditions for adhering to the required wiring pattern (conduction or circuit pattern) 201 formed on the metal layer portion of the constituent base film 202 are not particularly limited, and a conventionally known method is applied. Can do. For example, a method of hot pressing (heating and pressing) such as heat laminating, a method of roll laminating with a heating roll, and the like can be applied.

  The conditions for using the method of hot pressing (heating and pressurizing) such as the above heat laminating include adhesive layers 102 and 103, flexible insulating film 101 serving as a coverlay film substrate, release-treated paper, What is necessary is just to determine suitably according to heat resistance, such as a PET film base separator, and melting temperature (or glass transition temperature etc.). Specifically, it is 70 to 130 ° C., preferably 80 to 120 ° C., 0.5 to 5 MPa, preferably 1 to 3 MPa, and thermocompression bonding (thermal lamination) in the range of 5 to 120 seconds, preferably 10 to 60 seconds. ) Is desirable. Here, when it is less than 70 ° C., the adhesive layer does not adhere, and when it exceeds 130 ° C., the PET separator may be deformed. If it is less than 0.5 MPa, the adhesive layer does not adhere, and if it exceeds 5 MPa, the amount of the adhesive flowing out to the opening may increase. If it is less than 5 seconds, the adhesive layer does not adhere, and if it exceeds 120 seconds, the amount of the adhesive flowing out to the opening portion may increase. In addition, the conditions in the case of using the method of roll laminating with a heating roll can be performed under substantially the same conditions as in the case of using the method of hot pressing (heating and pressurizing) such as the above-mentioned thermal lamination.

  An adhesive layer 103 having a relatively low flow property is pasted on the wiring pattern (conducting or circuit pattern) 201. This adhesive layer 103 is sufficiently embedded between the wiring and has a partial gap. It is necessary to design so as to obtain a flow property to such an extent that does not occur.

  In the case of the adhesive layer 103 alone, the adhesive does not flow out to the opening portion such as the wiring pattern terminal portion, but the surface smoothness of the multilayer circuit board 300 or the flexible circuit board (not shown) cannot be obtained. In the present invention, the adhesive layer 103 is laminated on the above-mentioned adhesive layer 103 so that the adhesive layer 102 is relatively thin, so that the adhesive can flow out while being the thinnest adhesive layer (interphase adhesive layer) 104. It is possible to achieve both suppression and surface smoothness of the multilayer circuit board.

  That is, in the adhesive film 105 or the coverlay film 100 of the present invention, by placing the adhesive layer 102 having a relatively high flow property on the adhesive layer 103 having a relatively low flow property, the inclined arrangement is performed. When affixing on the wiring pattern (conduction or circuit pattern) 201 by press (thermal lamination) or the like, first, the adhesive layer 103 having a relatively low flow property comes into contact first, and the low flow property of the adhesive layer By this, it is possible to sufficiently enter between the wirings of the wiring pattern 201 without causing voids and voids partially, and a predetermined adhesive strength can be obtained. Furthermore, in the adhesive layer 102 having a relatively high flow property that is inclinedly disposed on the adhesive layer 103, the adhesive layer 103 follows and changes the fine and complicated pattern shape of the wiring pattern 201, and the same shape. And the wiring of the wiring pattern 201 after the adhesive layer 102 has already entered, in a form that continuously traces (follows) the shape of the adhesive layer 102. It can be continuously inserted between the wirings. For this reason, even the adhesive layer 102 having a relatively high flow property can be sufficiently penetrated without causing a gap or a void between the wirings of the wiring pattern 201. In the adhesive layer 104 after being pressed and attached in this manner (such as heat lamination), it is possible to achieve both the suppression of the flow of the adhesive and the surface smoothness of the multilayer circuit board.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to only the forms shown in the following examples.

Example 1
(1) Preparation of solution of adhesive composition ESCN-195 of cresol novolac type epoxy resin with respect to 60 parts by weight of acrylic rubber WS02 3D R (manufactured by Nagase ChemteX; number average molecular weight 110000) containing carboxylic acid as a functional group -10 (manufactured by Sumitomo Chemical Co., Ltd.), 20 parts by weight of a resol type phenolic resin, butanol H2181 (manufactured by Hitachi Chemical Co., Ltd.), 0.6 part by weight of dicyandiamide as a curing agent, aluminum hydroxide as an inorganic filler 20 parts by weight of Hijilite H42M (manufactured by Showa Denko KK) was dissolved and dispersed in methyl ethyl ketone to obtain a 20 wt% nonvolatile solution. This solution was adjusted to a particle size of 5 μm or less using a ball mill, and sufficiently dispersed to prepare an adhesive composition solution.

(2) Production of Adhesive Film As the first adhesive layer 102, a 98 μm-thickness release-based paper-based separator (alkyd release agent / PET (thickness 16 μm) / quality paper / PET (thickness) 16 μm)), the solution of the adhesive composition obtained in (1) above was applied so that the thickness of the adhesive layer 102 after drying was 20 μm, and dried in a hot air dryer at 100 ° C. for 5 minutes. Thus, the adhesive layer 102 having high flowability was obtained. Subsequently, as a second adhesive layer 103, a 50 μm thick PET film-based separator (alkyd release agent / PET (thickness 50 μm)) obtained by the above (1) was obtained. The same adhesive composition solution was applied so that the thickness of the adhesive layer 103 after drying was 20 μm, dried in a hot air dryer at 100 ° C. for 5 minutes, and further heated at 100 ° C. for 10 minutes. To give an adhesive layer 103 with low flowability. The obtained two adhesive layers 102 and 103 were laminated by thermal lamination (100 ° C., 2 MPa, laminating time 30 seconds), and inclined to form an adhesive film 105 having an adhesive layer 104. The obtained adhesive film 105 was evaluated for the following characteristics.

(Characteristic evaluation)
(3) Press workability Adhesive film 105 having adhesive layers 104 having different flow properties is pasted on the polyimide surface of a copper-clad laminate formed of a polyimide film having a thickness of 25 μm and copper foil A having a thickness of 35 μm. Combined. At this time, the paper-based separator on which the adhesive film 105 was subjected to the mold release treatment was peeled off, and then the surface of the adhesive film 105 having a high flowability (adhesive layer 102 side) was bonded to the polyimide surface of the laminate (adhesion). Matching conditions: thermal lamination, 100 ° C., 2 MPa, 30 seconds). Subsequently, the PET film base separator from which the adhesive film 105 has been subjected to the release treatment is peeled off, and then the surface of the adhesive film 105 having a low flowability (adhesive layer 103 side) is provided with a copper-clad laminate having a required wiring pattern. Bonded to the copper foil surface (wiring pattern surface) of (a copper-clad laminate formed of a 35 μm thick copper foil wiring pattern and a 25 μm thick polyimide base film) (bonding conditions; heat Lamination, 100 ° C., 2 MPa, 30 seconds). Next, thermocompression bonding was performed at a press temperature of 170 ° C., a pressure of 2.0 MPa, and a time of 5 minutes, and the surface smoothness of the outermost layer copper foil A and the flowability from the end were evaluated. The obtained results are shown in Table 1 below.

(4) Flowability After peeling off the release-treated paper-based separator and the release-treated PET film-based separator of the produced adhesive film 105, the adhesive film 105 was subjected to a temperature of 170 ° C., a pressure of 9.8 MPa, The adhesive film flow amount (unit: g / 10 minutes) from a stainless steel die having a diameter of 1.0 mm and a length of 1.0 mm was calculated as a flowability index by thermocompression bonding for 1 minute. The obtained results are shown in Table 1 below.

Example 2
In Example 1, when the second adhesive layer 103 was prepared, an adhesive composition solution containing 50 parts by weight of aluminum hydroxide Heidilite H42M (manufactured by Showa Denko KK) was used. The same procedure as in Example 1 was performed except that the additional heat treatment of the eye adhesive layer 103 was not performed. Table 1 below shows the results of characteristic evaluation (surface smoothness, flowability from the end portion, and flowability) of the obtained adhesive film 105.

Example 3
In Example 1, when producing the first adhesive layer 102, a flexible insulating film (coverlay-constituting base film) serving as a coverlay film substrate instead of the paper-based separator subjected to the release treatment The same procedure as in Example 1 was performed except that a polyimide film having a thickness of 25 μm was used as 101 and the coverlay film 100 was used. The obtained cover lay film 100 was evaluated for the following characteristics.

(Characteristic evaluation)
(3) Press workability After peeling off the release-treated PET film-based separator of the coverlay film 100, the surface of the coverlay film 100 having a low flowability (adhesive layer 103 side) is placed on the required wiring pattern. Bonded to the copper foil surface (wiring pattern surface) of a copper-clad laminate (a copper-clad laminate formed of a 35 μm thick copper foil wiring pattern and a 25 μm thick polyimide base film) (Lamination conditions: thermal lamination, 100 ° C., 2 MPa, 30 seconds). Next, thermocompression bonding was performed at a press temperature of 170 ° C., a pressure of 2.0 MPa, and a time of 5 minutes, and the surface smoothness of the coverlay film substrate 101 of the outermost layer and the flowability from the end were evaluated. The obtained results are shown in Table 1 below.

(4) Flowability After removing the release-treated PET film-based separator of the produced coverlay film 100, the coverlay film 100 was thermocompression bonded at a temperature of 170 ° C., a pressure of 9.8 MPa for 1 minute. The amount of the coverlay film outflow (unit: g / 10 minutes) from a stainless steel die having a diameter of 1.0 mm and a length of 1.0 mm was calculated as an index of flowability. The obtained results are shown in Table 1 below. Here, in the case of the coverlay film whose one side is a coverlay film base material, the adhesive layer was peeled off from the polyimide film of the coverlay film base material and measured.

Comparative Example 1
In Example 1, the adhesive composition solution was applied so that the thickness of the adhesive layer after drying was 40 μm as the first adhesive layer 102 and dried in a hot air dryer at 100 ° C. for 5 minutes. The same procedure as in Example 1 was conducted except that the adhesive film 105 (consisting of the adhesive layer 102) was used. The obtained adhesive film 105 was evaluated for the following characteristics.

(Characteristic evaluation)
(3) Press workability An adhesive film 105 composed of the single-layer adhesive layer 102 was bonded to a polyimide surface of a copper-clad laminate formed of a polyimide film having a thickness of 25 μm and a copper foil A having a thickness of 35 μm. . At this time, the surface of the adhesive layer 102 on which the release separator of the adhesive film 105 was not formed was first bonded to the polyimide surface of the laminate (bonding conditions; thermal lamination, 100 ° C., 2 MPa, 30 seconds). Subsequently, the paper-based separator from which the adhesive film 105 was subjected to the release treatment was peeled off, and then the adhesive layer 102 of the adhesive film 105 was placed on a copper-clad laminate having a required wiring pattern (a copper foil wiring having a thickness of 35 μm). Bonded to the copper foil surface (wiring pattern surface) of the pattern and a 25 μm thick polyimide base film made of polyimide (bonding conditions; thermal lamination, 100 ° C., 2 MPa, 30 seconds) ). Next, thermocompression bonding was performed at a press temperature of 170 ° C., a pressure of 2.0 MPa, and a time of 5 minutes, and the surface smoothness of the outermost layer copper foil A and the flowability from the end portion were evaluated. The obtained results are shown in Table 1 below.

(4) Flowability After the release-processed paper-based separator of the produced adhesive film 105 was peeled off, the adhesive film 105 was subjected to thermocompression bonding at a temperature of 170 ° C., a pressure of 9.8 MPa for 1 hour, and a diameter of 1. The amount of adhesive film outflow (unit: g / 10 minutes) from a stainless die having a length of 0 mm and a length of 1.0 mm was calculated as an index of flowability. The obtained results are shown in Table 1 below.

Comparative Example 2
In Example 1, when the first adhesive layer 102 was produced, an example was used except that an adhesive composition solution containing 50 parts by weight of aluminum hydroxide Heidilite H42M (manufactured by Showa Denko) was used. 1 was performed. Table 1 below shows the results of characteristic evaluation (surface smoothness, flowability from the edge and flowability) of the obtained adhesive film 105.

  The number of parts (parts by weight) of the solution of the adhesive composition used for forming each adhesive layer in the table represents the ratio by weight of the active ingredient excluding the solvent.

  The circuit board configuration A in the table is a copper-clad laminate having a copper-clad laminate / adhesive film / required wiring pattern.

  The circuit board configuration B in the table is a copper-clad laminate having a coverlay film / required wiring pattern.

  The determination of the surface smoothness in the table was performed using a laser displacement meter as shown in FIG. All were performed for 5 samples.

○ The height of the unevenness is less than 8 μm for all samples. × Even with one sample, the height of the unevenness is 8 μm or more.

  Judgment of the flowability (from the end) in the table was performed using a caliper and evaluated in two stages as follows. All were performed for 5 samples.

○ The longest part of the flow-out part is 100 μm or less. X The longest part of the flow-out part exceeds 100 μm.

  As is clear from the above description, at least two adhesive layers having different flow properties are laminated as an adhesive layer of an adhesive film and a coverlay film, and the surface with a small flow property of the adhesive layer is placed on the wiring pattern. By providing, an adhesive film and a cover lay film that have excellent surface smoothness after pressing (thermocompression bonding) in the above characteristic evaluation and can suppress the flow of the adhesive material to the opening portion of the wiring pattern terminal portion as much as possible. Can be provided.

It is the cross-sectional schematic which represented typically the adhesive film for circuit boards of this invention. It is the cross-sectional schematic which represented typically the structure of the multilayer circuit board in which the circuit pattern of the other party which applies this circuit board coverlay film of this invention and the circuit board coverlay film of this invention is formed. It is explanatory drawing which represented typically a mode that surface smoothness (surface unevenness | corrugation) was measured about the adhesive film obtained in the Example using the laser displacement meter.

Explanation of symbols

100 coverlay film,
101. A flexible insulating film (coverlay composition base film) to be a coverlay film base material,
102 Adhesive layer with high flowability,
103 Adhesive layer with low flowability,
104 Adhesive layer composed of a plurality of layers having different rheological properties,
105 adhesive film for circuit boards,
200 circuit board,
201 conduction (or circuit) pattern,
202 circuit board configuration base film,
203 Lower layer substrate (insulating substrate),
300 Multi-layer circuit board or flexible circuit board.

Claims (5)

  An adhesive film for a circuit board, comprising an inclined arrangement in which at least two adhesive layers having different flow properties are laminated. A flow rate of adhesive film outflow (unit: g / 10 min) from a stainless steel die having a diameter of 1.0 mm and a length of 1.0 mm by thermocompression bonding at a temperature of 170 ° C. and a pressure of 9.8 MPa for 1 minute. Is calculated as
The flowability of the first adhesive layer is in the range of 70 to 120 g / 10 min.
The flowability of the second adhesive layer is in the range of 10-50 g / 10 minutes,
When there are three or more adhesive layers, the flow property of the nth adhesive layer is smaller than the flow property of the (n-1) th layer (where n is an integer from 3 to the number of laminated adhesive layers). An adhesive film for circuit boards. An adhesive film layer formed by laminating at least two adhesive layers having different flow properties according to claim 1 or 2 on one side of a film substrate,
A cover lay film for a circuit board, wherein the adhesive film layer is arranged so as to be inclined so that the flowability of the adhesive film layer decreases from the film base to the outside.   A multilayer circuit board comprising a plurality of adhesive layers having different flow properties according to claim 1 or 2 laminated and arranged such that the smaller flow property is on the pattern side.   A flexible circuit board using the circuit board coverlay film according to claim 3.

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