JP2009021350A - Cover lay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cover lay which has superior size stability, superior heat resistance, and characteristics adaptive to an AOI and is also superior in traveling property (easy lubricating property) and adhesion. <P>SOLUTION: The cover lay is provided which uses a polyimide film mainly made up of 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether as a diamine component and pyromellitic dianhydride as a dianhydride component and has an adhesive layer formed on one surface of the polyimide film, the cover lay is characterized in that power mainly made up of inorganic particles of 0.01 to 1.5 μm in particle size and 0.05 to 0.7 μm in average particle size is dispersed in the film in an amount of 0.1 to 0.9% per film resin weight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cover lay, and more particularly to a cover lay obtained by forming an adhesive layer on one side of a polyimide film as a base material. More specifically, by adding an inorganic fine powder, the inorganic powder is not exposed and surface protrusions are generated in a state of being uniformly dispersed in the film, the surface state is controlled, and the runnability and adhesiveness of the film are controlled. In addition, the present invention relates to a cover lay using a heat-resistant polyimide film applicable to an automatic optical inspection system (AOI) of a flexible printed circuit board (FPC) and a chip-on-film (COF).

  Printed wiring boards are widely used in electronic and electrical equipment. Among them, a flexible printed wiring board that can be bent is widely used in bent portions of personal computers and mobile phones, and in portions that require bending such as hard disks. As the base material of such a flexible printed wiring board and the base material of a coverlay for protecting the wiring board, various polyimide films are usually used.

  A typical polyimide film includes a polyimide film using pyromellitic dianhydride as the acid dianhydride component and 4,4'-diaminodiphenyl ether as the diamine component. Such a polyimide film has a structure with an excellent balance between mechanical and thermal properties, and is widely used industrially as a general-purpose product. However, a polyimide film composed of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether has an advantage that it is easy to bend. However, when used as a coverlay, it is too soft and tends to generate wrinkles. When wrinkles are generated, air is caught in the portions, and the wiring is corroded. As a result, there is a problem that the wiring is defective.

  In addition, polyimide film consisting of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether has a large coefficient of thermal expansion (CTE) and hygroscopic expansion coefficient (CHE), and a high water absorption rate. The change is great. For this reason, when used as a cover lay, there has been a problem in that the dimensional change with the wiring board is shifted, and warping occurs when bonded.

  In order to solve such a problem, a method of forming a cover lay using a substrate having a small dimensional change other than a polyimide film, such as a liquid crystal film (see, for example, Patent Document 1) has been disclosed. Has inferior heat resistance compared to polyimide film, and has a problem that the base material is deformed during soldering. Especially in recent years, lead-free solders that do not use lead have spread due to environmental problems, but since most of the lead-free solders have a higher melting point than lead-containing solders, the problem of liquid crystal film substrate deformation has become more serious. It was.

Moreover, when a polyimide film is used for a coverlay, one of the important practical characteristics is the slipperiness (slidability) of the film. In various film processing steps, the film support (for example, rolls) and the slipperiness of the film and the slipperiness of the films are ensured, thereby improving the operability and handleability in each step. The occurrence of defective parts such as wrinkles can be avoided. However, in recent finer pitches of electronic components, inspection of flexible printed wiring boards with coverlays has been mainly conducted by visual inspection of wiring width, foreign matter, etc., but automatic optical inspection system (AOI) ) Is introduced, the conventional formulation in which the inorganic powder is mixed for the purpose of improving the slipperiness is considered to be a large obstacle because the inorganic powder is too large in the AOI and the facing powder is judged as a foreign substance. It has become. In the conventional smoothing technology for polyimide films, an inert inorganic compound (for example, alkaline earth metal orthophosphate, dibasic calcium phosphate anhydride, calcium pyrophosphate, silica, talc) is added to polyamic acid (Patent Document 2). Further, a method of performing plasma treatment after forming fine protrusions on the film surface with fine particles (see Patent Document 3) is known. However, there is a problem that the particles shown in these figures have a large particle size and cannot be applied to an automatic optical inspection system. In addition, the surface of the film has a large number of protrusions made of the inorganic particles, in which inorganic particles having an average particle diameter of 0.01 to 100 μm are held and embedded in the polyimide film surface layer. A method (see Patent Document 4) in which 1 × 10 to 5 × 10 ⁸ pieces / mm ² exists in a layer is known. This method is an object that effectively obtains a slippery effect by actively exposing protrusions on the surface and reducing the coefficient of friction on the film surface, but the film surface is exposed because some inorganic particles are exposed. There are problems such as scratches on the skin and poor appearance.
JP 2000-280341 A JP-A-62-68852 JP 2000-191810 A Japanese Patent Laid-Open No. 5-25295

  Accordingly, an object of the present invention is a cover lay which is suitable for bonding to a flexible printed wiring board using lead-free solder, which solves both the problem of dimensional change and heat resistance of the cover lay, and is easy to travel. An object of the present invention is to provide a coverlay that can satisfy (slidability), adhesiveness, and automatic optical inspection system (AOI) at the same time.

In order to achieve the above object, the present invention employs the following configuration.
(1) Using a polyimide film mainly composed of 3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as a diamine component and pyromellitic dianhydride as an acid dianhydride component, on one side of this polyimide film, A cover lay formed by forming an adhesive layer, mainly composed of inorganic particles having a particle diameter in the range of 0.01 to 1.5 μm and an average particle diameter of 0.05 to 0.7 μm. A cover lay characterized by using a polyimide film in which a powder is dispersed in a film at a ratio of 0.1 to 0.9% by weight per film resin weight.
(2) Mainly composed of 10 to 50 mol% of 3,4′-diaminodiphenyl ether and 50 to 90 mol% of 4,4′-diaminodiphenyl ether as a diamine component, and pyromellitic dianhydride as an acid dianhydride component. A coverlay according to (1), wherein a polyimide film is used.
(3) Heat shrinkage at an elastic modulus of 3 to 6 GPa, a linear expansion coefficient at 50 to 200 ° C. of 5 to 20 ppm / ° C., a humidity expansion coefficient of 25 ppm /% RH or less, a water absorption of 3% or less, and 200 ° C. for 1 hour. The coverlay according to (1) and (2), wherein a polyimide film having a rate of 0.10% or less is used.
(4) The coverlay according to any one of (1) to (3), wherein the adhesive mainly comprises at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin.
(5) The coverlay according to any one of (1) to (4), wherein inorganic particles are contained at a ratio of 0.3 to 0.8% by weight per film resin weight.
(6) The coverlay according to any one of (1) to (5), wherein the average particle diameter of the inorganic particles is 0.1 to 0.6 μm.
(7) The coverlay according to any one of (1) to (6), wherein the average particle size of the inorganic particles is 0.3 to 0.5 μm.
(8) In the particle size distribution of the inorganic particles, the particles having a particle size of 0.15 to 0.60 μm occupy a ratio of 80% by volume or more in all the particles. Coverlay.
(9) The coverlay according to any one of (1) to (8), wherein there are a plurality of protrusions on the surface of the film that are caused by the inorganic particles but the inorganic particles are not exposed on the surface.
(10) The coverlay according to (9), wherein among the plurality of protrusions, the number of protrusions having a height of 2 μm or more is 5/40 cm square or less.
(11) The coverlay according to any one of claims 1 to 10, wherein the film thickness is 5 to 175 µm.

  According to the present invention, the lead-free solder is not deformed, and by adding the inorganic fine powder, the inorganic powder is not exposed, and fine surface protrusions are expressed evenly dispersed in the film. In addition, since the runnability and adhesiveness of the film are improved, it is suitable as a cover lay for a flexible printed wiring board for forming fine wiring.

  The cover lay of the present invention uses a polyimide film as a base material and has an adhesive formed on one side of the polyimide film.

  Here, the polyimide film of the base material is a polyimide film mainly composed of 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether as the diamine component, and pyromellitic dianhydride as the acid dianhydride component. .

  That is, three types of 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, and pyromellitic dianhydride are essential components, and only these three types or a small amount of another component is added to these three types. It is a polyimide film obtained by this. Preferably, 10 to 50 mol% of 3,4′-diaminodiphenyl ether and 50 to 90 mol% of 4,4′-diaminodiphenyl ether are used as the diamine component, and pyromellitic dianhydride is used as the acid dianhydride component. It is the polyimide film which becomes. More preferably, the elastic modulus is 3 to 6 GPa, the linear expansion coefficient at 50 to 200 ° C. is 5 to 20 ppm / ° C., the humidity expansion coefficient is 25 ppm /% RH or less, the water absorption is 3% or less, and 200 ° C. for 1 hour. It is a polyimide film having a heat shrinkage rate of 0.10% or less. When the amount of 3,4'-diaminodiphenyl ether is too much, it becomes hard, and when it is too little, it is too soft, so 10 to 50 mol% is preferable, more preferably 15 to 45 mol%, and more preferably 20 to 40 mol%. When the amount of 4,4'-diaminodiphenyl ether is too much, it becomes soft, and when it is too little, it becomes hard, so it is preferably 50 to 90 mol%, more preferably 55 to 85 mol%, more preferably 60 to 80 mol%. The elastic modulus, which is an index of hardness, is preferably in the range of 3 to 6 GPa. The linear expansion coefficient is preferably 5 to 20 ppm / ° C., and if it exceeds 20 ppm / ° C., the dimensional change due to heat is too large, and if it is smaller than 5 ppm / ° C., the difference from the linear expansion coefficient with the metal used for the wiring increases. Therefore, warping occurs. When the humidity expansion coefficient exceeds 25 ppm /% RH, the dimensional change due to humidity is too large. Therefore, the humidity expansion coefficient is preferably 25 ppm /% RH or less. If the water absorption rate exceeds 3%, the dimensional change of the film becomes large due to the influence of the sucked water, so 3% or less is preferable. When the heat shrinkage rate at 200 ° C. for 1 hour exceeds 0.10%, the dimensional change due to heat becomes large, so the heat shrinkage rate is preferably 0.10% or less.

  As described above, a small amount of diamine may be added to the polyimide film in the present invention in addition to 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether. In addition to pyromellitic dianhydride, a small amount of acid dianhydride may be added. Specific examples of diamines and acid dianhydrides include, but are not limited to:

(1) Acid dianhydride 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3 ′, 3,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4 4′-benzophenone tetracarboxylic dianhydride, 2,3,6,7-naphthalenedicarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5 6-tetracarboxylic dianhydride, 1,2,4,5-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,4,5,8-deca Hydronaphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,5,6-hexahydronaphthalenetetracarboxylic dianhydride, 2,6-dichloro-1,4,5,8-naphthalenetetracarboxylic Acid dianhydride, 2,7-dichloro B-1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-tetrachloro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,8,9 , 10-phenanthrenetetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, , 1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis ( 3,4-dicarboxyphenyl) sulfone dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 3,4,3 ′, 4′-benzophenone tetracarboxylic dianhydride, and the like.

(2) Diamine 3,3′-diaminodiphenyl ether, metaphenylenediamine, paraphenylenediamine, 4,4′-diaminodiphenylpropane, 3,4′-diaminodiphenylpropane, 3,3′-diaminodiphenylpropane, 4,4 '-Diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, benzidine, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 2,6-diaminopyridine, bis- (4-aminophenyl) diethylsilane, 3,3′- Dichlorobenzidine, bis- (4 Aminophenyl) ethylphosphinoxide, bis- (4-aminophenyl) phenylphosphinoxide, bis- (4-aminophenyl) -N-phenylamine, bis- (4-aminophenyl) -N-methylamine 1,5-diaminonaphthalene, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,4′-dimethyl-3 ′, 4-diaminobiphenyl 3,3′-dimethoxybenzidine, 2,4- Bis (p-β-amino-t-butylphenyl) ether, bis (p-β-amino-t-butylphenyl) ether, p-bis (2-methyl-4-aminopentyl) benzene, p-bis- ( 1,1-dimethyl-5-aminopentyl) benzene, m-xylylenediamine, p-xylylenediamine, 1,3-diaminoadamantane, 3,3′-diamino 1,1′-diaminoadamantane, 3,3′-diaminomethyl 1,1′-diadamantane, bis (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylene Diamine, 3-methylheptamethylenediamine, 4,4'-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis (3-aminopropoxy) ethane, 2,2-dimethylpropylenediamine, 3-methoxy Hexaethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, 2,5-diamino-1, 3,4-oxa Azole, 2,2-bis (4-aminophenyl) hexafluoropropane, N-(3- aminophenyl) -4-aminobenzamide, 4-aminophenyl-3-aminobenzoate and the like.

  When manufacturing a polyimide film, usually, first, a polyamic acid that is a precursor is synthesized from polymerization of diamine and acid dianhydride, and then formed into a film, or after being formed into a film and then imidized to form a polyimide film. To do. In the present invention, at least two types of diamine components and at least one type of acid dianhydride are used, but these components may be mixed at once and polymerized at random, or may be mixed in order in an appropriate combination and blocked. Polymerization may be performed. For example, block polymerization in which 3,4′-diaminodiphenyl ether and pyromellitic dianhydride are reacted first and then 4,4′-diaminodiphenyl ether is added, or first, 4,4′-diaminodiphenyl ether and pyromellitic acid two are added. Examples thereof include block polymerization in which an anhydride is reacted and then 3,4'-diaminodiphenyl ether is added. Examples of the solvent used in the polymerization include, but are not limited to, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylformamide, dimethyl sulfoxide and the like. Further, various catalysts typified by tertiary amines such as β-picoline, various dehydrating agents typified by organic carboxylic acid anhydrides such as acetic anhydride, and the like may be used as appropriate.

The polymerization method may be performed by any known method, and examples thereof include (1) to (5).
(1) A method in which the total amount of the aromatic diamine component is first put in a solvent, and then the aromatic tetracarboxylic acid component is added so as to be equivalent to the total amount of the aromatic diamine component and polymerized.
(2) A method in which the total amount of the aromatic tetracarboxylic acid component is first put in a solvent, and then the aromatic diamine component is added in an amount equivalent to that of the aromatic tetracarboxylic acid component for polymerization.
(3) After one aromatic diamine compound is put in a solvent, the aromatic tetracarboxylic acid compound is mixed at a ratio of 95 to 105 mol% with respect to the reaction components, and then mixed for the other time. A method in which an aromatic diamine compound is added, and then an aromatic tetracarboxylic acid compound is added and polymerized so that the total aromatic diamine component and the total aromatic tetracarboxylic acid component are approximately equal.
(4) After putting the aromatic tetracarboxylic acid compound in the solvent, the aromatic tetracarboxylic acid compound is mixed for a time required for the reaction at a ratio of 95 to 105 mol% of one aromatic diamine compound with respect to the reaction component, and then the aromatic tetracarboxylic acid compound is mixed. A method in which a carboxylic acid compound is added, and then the other aromatic diamine compound is added and polymerized so that the total aromatic diamine component and the total aromatic tetracarboxylic acid component are approximately equal.
(5) A polyamic acid solution (A) is prepared by reacting one aromatic diamine component and an aromatic tetracarboxylic acid in a solvent so that either one becomes excessive, and the other aromatic diamine in another solvent. The polyamic acid solution (B) is prepared by reacting the component and the aromatic tetracarboxylic acid so that either one becomes excessive. A method of mixing the polyamic acid solutions (A) and (B) thus obtained to complete the polymerization. At this time, when adjusting the polyamic acid solution (A), if the aromatic diamine component is excessive, the polyamic acid solution (B) contains excessive aromatic tetracarboxylic acid component, and the polyamic acid solution (A) contains aromatic tetracarboxylic acid. When the acid component is excessive, the polyamic acid solution (B) makes the aromatic diamine component excessive, and the polyamic acid solutions (A) and (B) are combined to form the wholly aromatic diamine component and wholly aromatic compound used in these reactions. Adjustment is made so that the amount of the tetracarboxylic acid component is approximately equal.

  The polymerization method is not limited to these, and other known methods may be used.

  The polyamic acid solution thus obtained contains a solid content of 5 to 40% by weight, preferably 10 to 30% by weight, and its viscosity is 10 to 2000 Pa · s as measured by a Brookfield viscometer, preferably 100-1000 Pa · s is preferably used for stable liquid feeding. Moreover, the polyamic acid in the organic solvent solution may be partially imidized.

  The inorganic fine powder added to form protrusions on the film surface of the present invention needs to be insoluble in all chemical substances that are contacted in the polyimide film manufacturing process. In view of this, silica, particularly silica produced by a wet pulverization method using a sol-gel method, is stable in a varnish-like polyamic acid solution and physically stable, and does not affect various physical properties of the polyimide.

  Furthermore, the fine silica powder is agglomerated by using it as a silica slurry that is uniformly dispersed in a polar solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, and n-methylpyrrolidone. It is preferable to prevent this. Since this slurry has a very small particle size, the sedimentation rate is slow and stable. Even if it settles, it can be easily redispersed by re-stirring.

  In the present invention, the particle diameter of the inorganic powder added to form protrusions on the surface of the polyimide film is in the range of 0.01 to 1.5 μm, and the average particle diameter is 0.05 μm to 0.00. When the thickness is in the range of 7 μm, more preferably in the range of 0.1 to 0.6 μm, and even more preferably in the range of 0.3 to 0.5 μm, the inspection with the automatic optical inspection system of the polyimide film can be applied without any problem. . Further, it can be used without causing deterioration of the mechanical properties of the film. On the other hand, if the average particle diameter is less than these ranges, sufficient slipperiness to the film cannot be obtained, and if it exceeds, the particles are judged to be foreign matter by an automatic inspection and inspection system, which is not preferable. Moreover, since the thickness of a normal film is 5 micrometers-175 micrometers, the particle | grains in this particle diameter range are not exposed to the surface.

  The inorganic particles are preferably 0.1 to 0.9% by weight per film resin weight, and more preferably 0.3 to 0.8% by weight. If the amount is 0.1% by weight or less, the film surface is insufficient in number of protrusions, so that sufficient slipperiness to the film cannot be obtained, the transportability is deteriorated, and the film winding shape when wound on a roll is also deteriorated. Therefore, it is not preferable. If it is 0.9% by weight or more, the slipperiness of the film will be improved, but the coarse protrusions due to abnormal aggregation of particles will increase, and this will be judged as a foreign substance by the automatic inspection system, resulting in an obstacle. It is not preferable.

  The surface protrusions of the inorganic particles also increase the film surface area, and the surface is sufficiently roughened so that the anchor effect is observed and the adhesiveness is not impaired.

  It is better that the particle size distribution of the inorganic particles is narrow, that is, the proportion of particles having a similar size to the whole particles is high. Specifically, particles having a particle size of 0.15 to 0.60 μm are all particles. It is preferable to occupy a ratio of 80% by volume or more. If the ratio of particles below 0.15 μm is higher than this range, the slipperiness of the film decreases, which is not preferable. In addition, it is possible to remove coarse particles with a 5 μm cut filter or a 10 μm cut filter when sending inorganic particles, but if the proportion of particles of 0.60 μm or more increases, the filter will frequently clog. This is not preferable because the process stability is impaired and coarse aggregation of particles is likely to occur.

The film in the present invention has a plurality of protrusions due to inorganic particles on the film surface, but it is important that the protrusions do not have the inorganic particles exposed on the surface.
In the film surface protrusion caused by the inorganic particles, the number of protrusions having a height of 2 μm or more is 5 pieces / 40 cm square or less, more preferably 3 pieces / 40 cm square or less, and even more preferably 1 piece / 40 cm square or less. That is. If it is more than this, the automatic inspection / inspection system determines that the particle is a foreign substance and causes a failure.

  A slurry in which such inorganic particles are dispersed in the same polar solvent as the organic solvent used in the production of polyimide is added to the polyamic acid solution in the polyimide production process, followed by decyclization and desolvation to obtain a polyimide film. Although it is preferable to obtain, after adding inorganic particle slurry in the organic solvent before polyamic acid polymerization, polyamic acid polymerization, decyclization and desolvation, etc., to obtain a polyimide film, etc. in the step before decyclization and desolvation It is possible to add the inorganic particle slurry in any process.

  Although it does not specifically limit about the thickness of a polyimide film, Preferably it is 5-175 micrometers, More preferably, it is 3-150 micrometers, More preferably, it is 5-125 micrometers. When it is too thick, it becomes easy to cause winding slip when it is made into a roll, and when it is too thin, wrinkles and the like are likely to enter.

  A coverlay is formed on one side of the polyimide film as described above via an adhesive. As the adhesive, at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin is preferable. These adhesives may be provided with various rubbers, plasticizers, curing agents, phosphorus-based flame retardants, and other various additives for the purpose of providing flexibility. The polyimide resin is mainly thermoplastic polyimide, but may be thermosetting polyimide. In the case of a polyimide resin, a solvent is usually unnecessary, but a polyimide soluble in an appropriate organic solvent may be used.

  The thickness of the adhesive is not particularly limited as long as the wiring of the flexible wiring board can be sufficiently embedded and the wiring can be protected. For example, when the wiring thickness is 18 μm, the adhesive thickness is 10 to 100 μm. An adhesive thickness of 15-50 μm is preferred. For example, when the wiring thickness is 8 μm, an adhesive thickness of 5 to 50 μm is preferable, and an adhesive thickness of 12.5 to 25 μm is more preferable. If the adhesive is too thin, it may not be possible to sufficiently embed between the wirings, and air may be caught. Further, if the adhesive is too thick, it affects the dimensional change of the polyimide film of the base material, so the thickness in the above range is selected.

  The cover lay thus formed is preferably provided with a protective sheet until just before being bonded to the flexible wiring board for the purpose of protecting the adhesive. As the protective sheet, polyester film, polyethylene film, polypropylene film. A polyvinyl chloride film etc. are mentioned, and what coated the well-known slight adhesive on these films is used.

  The coverlay of this invention is used by bonding with a flexible printed wiring board. Examples of the method for forming wiring on the wiring board include a subtractive method, a semi-additive method, and a full additive method. The subtractive method is a method of forming a wiring by attaching a copper foil on a polyimide film via an adhesive and etching the copper foil into a wiring pattern. Alternatively, the copper layer is polyimide directly without using an adhesive. It means a method of forming a wiring by forming on a film and etching a copper layer into a wiring pattern. When affixing a copper foil, a rolled copper foil or an electrolytic copper foil is used as the copper foil. Also, when forming wiring, a photoresist layer is usually formed on a copper foil, and this photoresist layer is subjected to selective exposure and development to be patterned into a wiring shape, and the patterned photoresist layer is used as an etching mask. The copper is etched and then the photoresist layer is completely removed. Here, a liquid or dry film resist is used as the photoresist, and a solution such as iron chloride, copper chloride, or peracid is used as the etchant.

  In the semi-additive method, a metal layer to be a seed layer is first formed directly on a polyimide film or via an adhesive, a photoresist layer is formed on the seed layer, and the photoresist layer is selectively exposed and developed. By patterning into a wiring shape by processing, using the patterned photoresist layer as a plating mask, wiring is formed on the seed layer by electroless plating or electrolytic plating, and then the photoresist is completely removed, and finally other than wiring This means that the seed layer is removed by etching. Here, as the seed layer metal, nickel, chromium, aluminum, lead, copper, tin, zinc, iron, silver, gold or the like is used alone or as an alloy. In addition, a liquid or dry film resist is used as a photoresist, lead, copper, nickel, chromium, tin, zinc, silver, gold or the like is used as a metal for electroless plating or electrolytic plating, and as an etching solution, An etchant that matches the metal of the seed layer is used.

  In the full additive method, a photoresist layer is formed directly on a polyimide film or on an adhesive, and the photoresist layer is subjected to selective exposure and development to pattern it into a wiring, and the patterned photoresist layer is plated. It means a method of forming a wiring by electroless plating as a mask and then completely removing the photoresist. Here, a liquid or dry film resist is used as the photoresist, and copper, nickel, lead, chromium, tin, zinc, silver, gold or the like is used as the electroless plating metal.

  As a metal used for the above-mentioned various wiring formation methods, copper is mainly preferred. The formed wiring is used as an electric / electronic circuit, but a metal having a higher resistance than copper is not preferable because electric conductivity is deteriorated. In addition, it is not preferable that the metal has a lower density than copper because the electrical conductivity is deteriorated. However, since copper has a drawback that it is easily rusted and corroded, it is optional to form a metal such as tin, lead, aluminum, nickel, silver, or gold on the copper for the purpose of protecting the copper. In addition, since copper easily diffuses into the polyimide film, nickel, chromium, silver, gold, tin, or the like may be arbitrarily placed between the polyimide film and copper as a barrier layer for the purpose of preventing copper diffusion.

  Hereinafter, specific examples will be described. In addition, although the polyimide film used by the Example uses what was formed into a film by the method of the synthesis examples 1-4, it is not limited to these. Moreover, the polyimide film used by Comparative Examples 1-4 uses what was formed by the synthesis examples 5-8. Furthermore, as the adhesive used in the examples, those prepared in Synthesis Examples 9 to 10 are used, but are not limited thereto. The film thickness, linear expansion coefficient, elastic modulus, humidity expansion coefficient, water absorption rate, and heat shrinkage rate were measured by the following methods (1) to (10).

(1) Film thickness It measured using the lightmatic (Series318) made from Mitutoyo.

(2) Linear expansion coefficient TMA-50 manufactured by Shimadzu Corporation was used, and measurement was performed under the conditions of measurement temperature range: 50 to 200 ° C and temperature increase rate: 10 ° C / min.

(3) Elastic modulus RTM-250 manufactured by A & D was used, and measurement was performed under the condition of a tensile speed of 100 mm / min.

(4) Humidity expansion coefficient A film was installed in a TM7000 furnace at 25 ° C., dried by sending dry gas into the furnace, and then the inside of the TM7000 furnace was 90% RH by supplying air from an HC-1 type steam generator. The humidity expansion coefficient was determined from the dimensional change during the period.

(5) Water absorption rate It left still in the desiccator of 98% RH atmosphere for 2 days, and evaluated by the weight increase with respect to the weight at the time of drying.

(6) Heat shrinkage rate A film of 20 cm × 20 cm was prepared, and the film size (L1) after being left in a room adjusted to 25 ° C. and 60% RH for 2 days was measured, followed by heating at 200 ° C. for 60 minutes. Thereafter, the film size (L2) was measured after being left in a room adjusted to 25 ° C. and 60% RH for 2 days, and evaluated by the following formula calculation.
Heat shrinkage rate = − (L2−L1) / L1 × 100

(7) Friction coefficient (Static friction coefficient)
The processed surfaces of the films were overlapped and measured according to JIS K-7125 (1999). That is, using a slip coefficient measuring apparatus Slip Tester (manufactured by Technonez Co., Ltd.), the film processing surfaces are overlapped with each other, a 200 g weight is placed thereon, one of the films is fixed, and the other is 100 mm / min Tensile and friction coefficients were measured.

(8) Automatic optical inspection (AOI)
The base film was inspected using an Orbotech SK-75. The case where a foreign substance and a fine particle could be distinguished was evaluated as “◯”, while the case where the size of the foreign substance and the fine particle was similar and could not be distinguished from each other was evaluated as a “x” evaluation.

(9) Evaluation of inorganic particles Using a laser diffraction / scattering particle size distribution measuring apparatus LA-910 manufactured by HORIBA, Ltd., a sample dispersed in a polar solvent was measured and analyzed, and the particle size range, average particle size, and particle size were obtained. The occupancy ratio for all particles of 0.15 to 0.60 μm was read.

(10) Number of abnormal protrusions The number of protrusions having a height of 2 μm or more was counted per 40 cm square area of the film. The height is measured with a scanning laser microscope “1LM15W” manufactured by Lasertec Co., Ltd., using a Nikon 100 × lens (CF Plan 100 × / 0.95∞ / 0 EPI) in the “SURFACE1” mode. This was confirmed by photographing and analyzing the surface.

(Synthesis Example 1)
Pyromellitic dianhydride (molecular weight 218.12) / 4,4′-diaminodiphenyl ether (molecular weight 200.20) / 3,4′-diaminodiphenyl ether (molecular weight 200.20) in a molar ratio of 4/3/1. The mixture was mixed at a ratio and polymerized with a DMAc (N, N-dimethylacetamide) 18.5 wt% solution to obtain a polyamic acid. The particle size is 0.01 μm or more and 1.5 μm or less, and particles having an average particle size of 0.30 μm and a particle size of 0.15 to 0.60 μm are composed of 87.2% by volume of silica N, N— A dimethylacetamide slurry was added to the varnish-like polyamic acid solution in an amount of 0.3% by weight per resin weight, and was sufficiently stirred and dispersed. A conversion agent consisting of acetic anhydride (molecular weight 102.09) and isoquinoline was mixed and stirred at a ratio of 50% by weight to the polyamic acid solution. At this time, it prepared so that acetic anhydride and isoquinoline might be 2.0 and 0.4 molar equivalent with respect to the amic acid group of a polyamic acid, respectively. The obtained mixture was cast on a stainless steel drum at 100 ° C. rotated by a T-shaped slit die to obtain a gel film having a self-supporting property with a residual volatile component of 55% by weight. This gel film was peeled off from the drum, and both ends thereof were gripped and treated in a heating furnace at 200 ° C. for 30 seconds, 350 ° C. for 30 seconds, and 550 ° C. for 30 seconds to obtain a polyimide film having a thickness of 25 μm. The physical properties are shown in Table 1.

(Synthesis Example 2)
Pyromellitic dianhydride (molecular weight 218.12) / 4,4′-diaminodiphenyl ether (molecular weight 200.20) / 3,4′-diaminodiphenyl ether (molecular weight 200.20) in a molar ratio of 10/7/3 The mixture was mixed at a ratio and polymerized with a DMF (N, N-dimethylformamide) 18.5 wt% solution to obtain a polyamic acid. Particles having a particle size of 0.01 μm or more and 1.5 μm or less, an average particle size of 0.38 μm, and a particle size of 0.15 to 0.60 μm are composed of 86.3% by volume of silica N , N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution in an amount of 0.35% by weight per resin weight and sufficiently stirred and dispersed. At this time, pyromellitic dianhydride and 3,4'-diaminodiphenyl ether were first reacted, and then block polymerization was performed by adding 4,4'-diaminodiphenyl ether. A conversion agent consisting of acetic anhydride (molecular weight 102.09) and isoquinoline was mixed and stirred at a ratio of 50% by weight to the polyamic acid solution. At this time, it prepared so that acetic anhydride and isoquinoline might be 2.0 and 0.4 molar equivalent with respect to the amic acid group of a polyamic acid, respectively. The obtained mixture was cast on a stainless steel drum at 100 ° C. rotated by a T-shaped slit die to obtain a gel film having a self-supporting property with a residual volatile component of 55% by weight. The gel film was peeled off from the drum, and both ends thereof were gripped and treated in a heating furnace at 200 ° C. for 30 seconds, 350 ° C. for 30 seconds, 550 ° C. for 30 seconds to obtain a polyimide film having a thickness of 12.5 μm. . The physical properties are shown in Table 1.

(Synthesis Example 3)
Pyromellitic dianhydride (molecular weight 218.12) / 4,4′-diaminodiphenyl ether (molecular weight 200.20) / 3,4′-diaminodiphenyl ether (molecular weight 200.20) in a molar ratio of 5/4/1 The mixture was mixed at a ratio and polymerized with a DMAc (N, N-dimethylacetamide) 18.5 wt% solution to obtain a polyamic acid. N particles of silica having a particle size of 0.01 μm or more and 1.5 μm or less, an average particle size of 0.45 μm, and a particle size of 0.15 to 0.60 μm is 87.7% by volume of all particles. , N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution in an amount of 0.3% by weight per resin weight and sufficiently stirred and dispersed. At this time, pyromellitic dianhydride and 4,4′-diaminodiphenyl ether were first reacted, and then block polymerization was performed in which 3,4′-diaminodiphenyl ether was added. A conversion agent consisting of acetic anhydride (molecular weight 102.09) and isoquinoline was mixed and stirred at a ratio of 50% by weight to the polyamic acid solution. At this time, it prepared so that acetic anhydride and isoquinoline might be 2.0 and 0.4 molar equivalent with respect to the amic acid group of a polyamic acid, respectively. The obtained mixture is cast on an endless belt from a T-shaped slit die and heated with hot air at 70 ° C. to obtain a gel film having a self-supporting property of 55% by weight of residual volatile components and a thickness of about 1.00 mm. It was. This gel film was peeled off from the endless belt, and both ends thereof were gripped and treated in a heating furnace at 200 ° C. for 60 seconds, 350 ° C. for 60 seconds, and 550 ° C. for 45 seconds to obtain a 125 μm thick polyimide film. The physical properties are shown in Table 1.

(Synthesis Example 4)
Pyromellitic dianhydride (molecular weight 218.12) / 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (molecular weight 322.20) / 4,4′-diaminodiphenyl ether (molecular weight 200.20) / 3,4'-diaminodiphenyl ether (molecular weight 200.20) is mixed at a molar ratio of 9/1/8/2 and polymerized to a DMAc (N, N-dimethylacetamide) 18.5 wt% solution. A polyamic acid was obtained. N particles of silica having a particle size of 0.01 μm or more and 1.5 μm or less, an average particle size of 0.35 μm, and a particle size of 0.15 to 0.60 μm is 87.0% by volume in all particles. , N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution in an amount of 0.5% by weight per resin weight and sufficiently stirred and dispersed. A conversion agent consisting of acetic anhydride (molecular weight 102.09) and isoquinoline was mixed and stirred at a ratio of 50% by weight to the polyamic acid solution. At this time, it prepared so that acetic anhydride and isoquinoline might be 2.0 and 0.4 molar equivalent with respect to the amic acid group of a polyamic acid, respectively. The obtained mixture was cast on an endless belt from a T-shaped slit die and heated with hot air at 50 ° C. to obtain a gel film having a self-supporting property with a residual volatile component of 55% by weight. This gel film is peeled off from the endless belt, both ends thereof are gripped, and processed in a heating furnace at 150 ° C. × 30 seconds, 300 ° C. × 30 seconds, 400 ° C. × 20 seconds, 550 ° C. × 20 seconds, and a thickness of 12. A 5 μm polyimide film was obtained. The physical properties are shown in Table 1.

(Synthesis Example 5)
In Synthesis Example 1, a polyimide film was obtained in the same manner as in Synthesis Example 1 except that silica was not added. Table 1 shows the physical properties of this polyimide film.

(Synthesis Example 6)
The silica used in Synthesis Example 2 has a particle diameter of 0.1 μm or more and 4.5 μm or less, particles having an average particle diameter of 1.1 μm and a particle diameter of 0.15 to 0.60 μm in all particles. In the same manner as in Synthesis Example 2, except that the silica was changed to 27.3% by volume and 0.2% by weight of N, N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution per resin weight. A polyimide film was obtained. Table 1 shows the physical properties of this polyimide film.

(Synthesis Example 7)
The silica used in Synthesis Example 3 has a particle size of 0.01 μm or more and 0.3 μm or less, particles having an average particle size of 0.03 μm and a particle size of 0.15 to 0.60 μm in all particles. The silica was changed to 31.4% by volume, and N, N-dimethylacetamide slurry was added in the same manner as in Synthesis Example 3 except that 0.35% by weight per resin weight was added to the varnish-like polyamic acid solution. A polyimide film was obtained. Table 1 shows the physical properties of this polyimide film.

(Synthesis Example 8)
The silica used in Synthesis Example 4 has a particle diameter of 0.01 μm or more and 2.0 μm or less, particles having an average particle diameter of 0.4 μm and a particle diameter of 0.15 to 0.60 μm in all particles. The same procedure as in Synthesis Example 4 was conducted except that the N, N-dimethylacetamide slurry was changed to 72.6% by volume of silica and 0.35% by weight of the varnish-like polyamic acid solution was added to the varnish-like polyamic acid solution. A polyimide film was obtained. Table 1 shows the physical properties of this polyimide film.

(Synthesis Example 9)
19 parts by weight of aluminum hydroxide “H-43” manufactured by Showa Denko K.K., 9 parts by weight of epoxy resin “Epicoat” 828 manufactured by Yuka Shell Co., Ltd., and phosphorus-containing epoxy resin “FX279BEK” manufactured by Toto Kasei Co., Ltd. 35 parts by weight, 3.5 parts by weight of curing agent 4,4′-DDS (4,4′-diaminodiphenylsulfone) manufactured by Sumitomo Chemical Co., Ltd., 26 parts by weight of JSR “NBR (PNR-1H)” Was mixed with 200 parts by weight of methyl isobutyl ketone at 30 ° C. to obtain an adhesive solution.

(Synthesis Example 10)
9 parts by weight of epoxy resin “Epicoat” 834 manufactured by Yuka Shell Co., Ltd., 17 parts by weight of phosphorus-containing epoxy resin “ZX-1548-3” manufactured by Tohto Kasei Co., Ltd., curing agent 4,4 manufactured by Sumitomo Chemical Co., Ltd. '-DDS 3.5 parts by weight, JSR "NBR (PNR-1H)" 26 parts by weight, Showa Denko Co., Ltd. aluminum hydroxide "H-43" 20 parts by weight methyl ethyl ketone 30 parts by weight The mixture was stirred and mixed at 0 ° C. to obtain an adhesive solution.

Example 1
Using the polyimide film formed in Synthesis Example 1, the adhesive of Synthesis Example 9 was applied to one side of the film and dried by heating at 150 ° C. for 5 minutes to form an adhesive layer having a dry film thickness of 25 μm to obtain a coverlay. It was.

  Using a copper-clad laminate F-30VC1 for flexible printed circuits manufactured by Nikkan Kogyo Co., Ltd., the copper foil surface and the adhesive layer of the coverlay were bonded at 100 ° C. and 0.27 MPa. Using the copper-clad laminate and coverlay bonded together in this way, peel strength (peel strength), solder heat resistance, and flame retardance based on UL were evaluated. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, a coverlay was formed in the same manner as in Example 1 except that the polyimide film formed in Synthesis Example 1 was changed to the polyimide film formed in Synthesis Example 5, and the same evaluation as in Example 1 was performed. Carried out. The results are shown in Table 1.

(Example 2)
Using the polyimide film formed in Synthesis Example 2, the adhesive of Synthesis Example 10 was applied to one side of the film and dried by heating at 150 ° C. for 5 minutes to form an adhesive layer having a dry film thickness of 15 μm to obtain a coverlay. It was.

  Using a copper-clad laminate F-30VC1 for flexible printed circuits manufactured by Nikkan Kogyo Co., Ltd., the copper foil surface and the adhesive layer of the coverlay were bonded at 100 ° C. and 0.27 MPa. Using the copper-clad laminate and coverlay bonded together in this way, peel strength (peel strength), solder heat resistance, UL-based flame retardance, and adhesiveness were evaluated. The results are shown in Table 1.

(Comparative Example 2)
In Example 2, a coverlay was formed in the same manner as in Example 2 except that the polyimide film formed in Synthesis Example 2 was changed to the polyimide film formed in Synthesis Example 6, and the same evaluation as in Example 2 was performed. Carried out. The results are shown in Table 1.

(Example 3)
In Example 1, except that the polyimide film formed in Synthesis Example 1 was changed to the polyimide film formed in Synthesis Example 3, a coverlay was formed in the same manner as in Example 1, and the same evaluation as in Example 2 was performed. Carried out. The results are shown in Table 1.

(Comparative Example 3)
In Example 3, a coverlay was formed in the same manner as in Example 3 except that the polyimide film formed in Synthesis Example 3 was changed to the polyimide film formed in Synthesis Example 7, and the same evaluation as in Example 3 was performed. Carried out. The results are shown in Table 1.

Example 4
In Example 1, except that the polyimide film formed in Synthesis Example 1 was changed to the polyimide film formed in Synthesis Example 4, a coverlay was formed in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. did. The results are shown in Table 1.

(Comparative Example 4)
In Example 4, a coverlay was formed in the same manner as in Example 4 except that the polyimide film formed in Synthesis Example 4 was changed to the polyimide film formed in Synthesis Example 8, and the same evaluation as in Example 4 was performed. Carried out. The results are shown in Table 1.

  According to the present invention, it is possible to provide a cover lay which is excellent in dimensional stability and heat resistance, has characteristics applicable to AOI, and is excellent in running property (easiness of sliding) and adhesiveness.

Claims (11)

A polyimide film mainly composed of 3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as a diamine component and pyromellitic dianhydride as an acid dianhydride component is used, and an adhesive layer is formed on one side of the polyimide film. A powder mainly composed of inorganic particles having a particle diameter in the range of 0.01 to 1.5 μm and an average particle diameter of 0.05 to 0.7 μm. A coverlay comprising a polyimide film dispersed in a film at a ratio of 0.1 to 0.9% by weight per film resin weight. A polyimide film mainly composed of 10 to 50 mol% 3,44'-diaminodiphenyl ether and 50 to 90 mol% 4,4'-diaminodiphenyl ether as a diamine component, and pyromellitic dianhydride as an acid dianhydride component The coverlay according to claim 1, wherein the coverlay is used. Elastic modulus 3-6 GPa, linear expansion coefficient at 50-200 ° C. 5-20 ppm / ° C., humidity expansion coefficient 25 ppm /% RH or less, water absorption 3% or less, heating shrinkage at 200 ° C. for 1 hour is 0 3. The coverlay according to claim 1 or 2, wherein a polyimide film of 10% or less is used. The coverlay according to claim 1, wherein the adhesive mainly comprises at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin. The coverlay according to any one of claims 1 to 4, wherein the inorganic particles are contained in an amount of 0.3 to 0.8% by weight per film resin weight. The coverlay according to any one of claims 1 to 5, wherein the average particle diameter of the inorganic particles is 0.1 to 0.6 µm. The coverlay according to any one of claims 1 to 6, wherein the average particle diameter of the inorganic particles is 0.3 to 0.5 µm. 8. The coverlay according to claim 1, wherein in the particle size distribution of the inorganic particles, particles having a particle size of 0.15 to 0.60 μm account for 80% by volume or more of all particles. The coverlay according to any one of claims 1 to 8, wherein a plurality of protrusions that are caused by inorganic particles but are not exposed on the surface are present on the surface of the film. The coverlay according to claim 9, wherein among the plurality of protrusions, the number of protrusions having a height of 2 μm or more is 5 pieces / 40 cm square or less. The coverlay according to claim 1, wherein the film thickness is 5 to 175 μm.