JP2008166555A - Flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed wiring board in which minute wiring can be formed and which has proper running performance (easy slidability) and will not deform, even if lead-free solder is used. <P>SOLUTION: The flexible printed wiring board contains a polyimide film, principally comprising 3,4'-diaminophenylether and 4,4'-diaminodiphenylether as a diamine component and a pyromellitic acid dihydride as an acid dihydride component, and further containing minute inorganic particles, wherein wiring is formed on one surface or on both surfaces of the polyimide film, with or without an adhesive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed wiring board, and more specifically, it is possible to form fine wiring obtained by forming wiring on one side or both sides of a polyimide film as a base material, and runnability (sliding property). ) And a flexible printed wiring board that does not deform even when lead-free solder is used.

  In recent years, printed wiring boards have been widely used in electronic and electrical equipment. In particular, foldable flexible printed wiring boards are widely used in bent parts of personal computers and mobile phones, and parts that need to be bent such as hard disks. Various polyimide films are 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, but it is too soft and the substrate is bent when mounting a semiconductor, resulting in poor bonding. Had the problem of becoming. 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. There is a problem that when the fine wiring is formed, the change is large and the desired wiring width and wiring cannot be formed.

  As a means for solving such a problem, a method of forming a flexible printed wiring board using a base material having a small dimensional change other than a polyimide film, for example, a liquid crystal film (see, for example, Patent Document 1) is known. However, the liquid crystal film is inferior in heat resistance to the 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 base deformation has become more serious. It was.

  Moreover, in a polyimide film, the slipperiness (slidability) of a film is mentioned as an important practical characteristic when used for a printed wiring board use. 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. This is because the occurrence of defective parts such as wrinkles can be avoided.

  As an easy lubrication technique in a conventional polyimide film, a method of adding an inert inorganic compound (for example, an alkaline earth metal orthophosphate, dicalcium phosphate anhydrate, calcium pyrophosphate, silica, talc) to a polyamic acid (for example, Further, a method of performing plasma treatment after forming fine protrusions on the film surface with fine particles (see, for example, Patent Document 3) is known. However, these inorganic particles have a problem that they have a large particle size and are not suitable for automatic optical inspection systems.

In addition, inorganic particles having an average particle diameter of 0.01 to 100 μm are held on the surface layer of the polyimide film by embedding a part of each particle, and a large number of protrusions made of partially exposed inorganic particles are formed on the surface of the film. A method (for example, see Patent Document 4) in which 1 × 10 to 5 × 10 ⁸ pieces / mm ² exists in a layer is known. This method effectively obtains a slippery effect by actively exposing protrusions on the surface and reducing the coefficient of friction on the film surface, but the inorganic particles are partially exposed on the film surface. For this reason, there was a problem that the film surface was scratched, resulting in poor appearance.
JP 2000-343610 A JP-A-62-68852 JP 2000-191810 A Japanese Patent Laid-Open No. 5-25295 JP-A-62-68852

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

  Therefore, the object of the present invention is to satisfy both dimensional change and heat resistance, enable fine wiring formation, good running property (sliding property), and no deformation even when lead-free solder is used. It is to provide a flexible printed wiring board.

In order to achieve the above object, according to the present invention,
3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as the diamine component, pyromellitic dianhydride as the acid dianhydride component, and an average particle size of 0.01 to 1.5 μm. Using a polyimide film in which a powder mainly composed of inorganic particles of 0.05 to 0.7 μm is dispersed in the film at a ratio of 0.1 to 0.9% by weight per film resin weight, A flexible printed wiring board characterized in that wiring is formed on one or both sides via an adhesive,
3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as the diamine component, pyromellitic dianhydride as the acid dianhydride component, and an average particle size of 0.01 to 1.5 μm. Using a polyimide film in which a powder mainly composed of inorganic particles of 0.05 to 0.7 μm is dispersed in the film at a ratio of 0.1 to 0.9% by weight per film resin weight, A flexible printed wiring board characterized in that wiring is formed on one or both sides without an adhesive, and 3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as diamine components, acid dianhydride It is mainly composed of pyromellitic dianhydride as a physical component and has a particle size of 0.01 to 1.5 μm. Use a polyimide film in which a powder mainly composed of inorganic particles having an average particle diameter of 0.05 to 0.7 μm is dispersed in a film at a ratio of 0.1 to 0.9% by weight per film resin weight There is provided a flexible printed wiring board characterized in that a wiring is formed on one side of the polyimide film without an adhesive and on the other side without an adhesive.

Furthermore, in the flexible printed wiring board of the present invention,
The proportion of each component in the polyimide film is 10 to 50 mol% paraphenylenediamine and 50 to 90 mol% 4,4'-diaminodiphenyl ether as a diamine component, and 100 mol% pyromellitic as an acid dianhydride component. Consisting of acid dianhydride,
The elastic modulus of the polyimide film 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. The heat shrinkage is 0.10% or less,
The wiring is mainly made of copper,
The adhesive mainly comprises at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin;
The wiring is formed by etching a metal layer,
The wiring is formed by plating,
The coverlay is stacked on top of the wiring,
In the particle size distribution of the inorganic particles, particles having a particle size of 0.15 to 0.60 μm account for a proportion of 80% by volume or more of all particles, and the number of protrusions having a height of 2 μm or more in the film surface protrusions caused by the inorganic particles. Is 5 pieces / 40 cm square or less in any case.

  According to the present invention, as described below, it is possible to obtain a flexible printed wiring board capable of forming fine wiring, having good running properties (slidability), and not deforming even when lead-free solder is used. it can.

  Hereinafter, the present invention will be described in detail.

  The flexible printed wiring board of the present invention uses a polyimide film as a base material, and wiring is formed on one or both sides of this polyimide film.

  The polyimide film used as a substrate in the present invention is a polyimide formed using 3,4'-diaminodiphenyl ether and 4,4'-diaminodiphenyl ether as the diamine component, and pyromellitic dianhydride as the acid dianhydride component. It is a film. 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.

  In said polyimide film, since it will become hard when there are too many 3,4'- diamino diphenyl ethers and it will be too soft when there are too few, 1-70 mol% is preferable, More preferably, it is 5-60 mol%, More preferably, it is 10-50. 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 20 to 99 mol% is preferable, 40 to 95 mol% is more preferable, and 50 to 90 mol% is more preferable.

  The elastic modulus, which is an index of the hardness of the polyimide film, is preferably in the range of 3 to 6 GPa. If it exceeds 6 GPa, it is too hard, and if it is less than 3 GPa, it is too soft.

  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 of 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 Paraphenylenediamine, 3,3′-diaminodiphenyl ether, metaphenylenediamine, 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 is first reacted with pyromellitic dianhydride, 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.

  In the polyimide film used in the present invention, it is essential to add inorganic particles in order to improve the running property (slidability). The travelability mentioned here appears in the static friction coefficient, and when the static friction coefficient exceeds 1, the travelability is extremely deteriorated. Therefore, the purpose is to make the static friction coefficient less than 1.

  In such inorganic particles, the powder particle diameter is in the range of 0.01 to 1.5 μm, and the average particle diameter is in the range of 0.05 μm to 0.7 μm, more preferably 0.1 to 0. When the thickness is in the range of .6 μm, and more preferably in the range of 0.3 to 0.5 μm, the polyimide film can be adapted to inspection with an automatic optical inspection system without any problem. Further, the film can be used without causing deterioration of mechanical properties of the film. Conversely, if the average particle size is below these ranges, sufficient slipperiness to the film cannot be obtained, and if it exceeds, the inorganic particles will be judged as foreign matter by the automatic inspection system and cause trouble. It is not preferable.

  The content of the inorganic particles is preferably from 0.1 to 0.9% by weight per film resin weight, and more preferably from 0.3 to 0.8% by weight. When the content is 0.1% by weight or less, not only the film surface has a sufficient number of protrusions, but sufficient slipperiness to the film cannot be obtained. It is not preferable because the appearance deteriorates. On the other hand, 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 object by the automatic inspection system and cause trouble. This is not preferable.

  The content of the inorganic particles is preferably from 0.1 to 0.9% by weight per film resin weight, and more preferably from 0.3 to 0.8% by weight. When the content is 0.1% by weight or less, not only the film surface has a sufficient number of protrusions, but sufficient slipperiness to the film cannot be obtained. It is not preferable because the appearance deteriorates. On the other hand, 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 object by the automatic inspection system and cause trouble. This is not preferable.

  The surface protrusion due to the inorganic particles also increases the film surface area, and the surface is sufficiently roughened to show an anchor effect without impairing the adhesiveness.

  It is better that the inorganic particles have a narrow particle size distribution, that is, the proportion of particles having similar sizes in the total particles is preferably 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 proportion of particles below this range and 0.15 μm or less increases, 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 feeding inorganic particles, but if the proportion of particles of 0.60 μm or more increases, the filter will frequently clog. As a result, not only the process stability is impaired, but also coarse aggregation of particles tends to occur.

  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. It is desirable to be. If it is more than this, it is not preferable because the inorganic particles are judged as foreign substances by the automatic inspection system and cause trouble.

  A slurry in which such inorganic particles are dispersed in the same polar solvent as the organic solvent used for 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.

Next, a method for polymerizing polyimide will be described. 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 diamine component is first put in a solvent, and then the acid dianhydride component is added so as to be equivalent to the total amount of the diamine component and polymerized.
(2) A method in which the total amount of the acid dianhydride component is first put in a solvent, and then the diamine component is added in an amount equivalent to that of the acid dianhydride component to polymerize.
(3) After putting one diamine component in a solvent, after mixing for the time required for reaction in the ratio which an acid dianhydride component becomes 95-105 mol% with respect to the reaction component, the other diamine compound is added. And then polymerizing by adding the acid dianhydride component so that the total diamine component and the total acid dianhydride component are substantially equal.
(4) After the acid dianhydride component is put in the solvent, the diamine component is mixed for a time necessary for the reaction at a ratio of 95 to 105 mol% of one diamine component with respect to the reaction component, and then the acid dianhydride component is added. And then polymerizing the other diamine compound so that the total diamine component and total acid dianhydride component are approximately equal.
(5) A polyamic acid solution (A) is prepared by reacting one of the diamine components and the acid dianhydride component in a solvent so that either one is excessive, and the other diamine component and the acid dianhydride in another solvent. The polyamic acid solution (B) is prepared by reacting either one of the anhydride components in excess. A method of mixing the polyamic acid solutions (A) and (B) thus obtained to complete the polymerization. (At this time, when the polyamic acid solution (A) is prepared, 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 component. When the carboxylic acid component is excessive, the polyamic acid solution (B) makes the aromatic diamine component excessive, mixes the polyamic acid solutions (A) and (B), and the wholly aromatic diamine component and total fragrance used in these reactions. (Adjust so that the amount of the tetracarboxylic acid component in the group is approximately equal.)
Etc.

  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.

  Next, the polyamic acid solution is extruded from the die, cast onto a drum or belt, for example, to form a film, then peeled off from the drum or belt, and converted to polyimide by applying an appropriate temperature. When casting on a drum or belt, imidization and solvent removal may be promoted by applying an appropriate temperature.

  Although it does not specifically limit about the thickness of a polyimide film, Preferably it is 1-225 micrometers, More preferably, it is 3-175 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.

  In the present invention, wiring is formed on one side or both sides of the polyimide film as described above via an adhesive or without an adhesive to form a flexible printed wiring board.

  As an adhesive in the case of using an adhesive, at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin is preferable. Among these, epoxy resins and polyimide resins are particularly preferable. For the purpose of imparting flexibility, these adhesives may be provided with various rubbers, plasticizers, curing agents, phosphorus-based flame retardants, and other various additives. The polyimide resin is mainly thermoplastic polyimide in many cases, 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.

  Examples of the wiring formation method include a subtractive method, a semi-additive method, a full additive method, and the like. 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.

  A rolled copper foil or an electrolytic copper foil is used as the copper foil when the copper foil is attached.

  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, a metal having a density lower than that of copper is not preferable because electric conductivity is deteriorated. However, since copper also has the disadvantage of being easily rusted and corroded, it is optional to form a metal such as tin, lead, aluminum, nickel, silver, or gold on copper for the purpose of protecting copper. . Also, since copper easily diffuses into the polyimide film, nickel, chromium, silver, gold, tin, or the like can be arbitrarily placed as a barrier layer between the polyimide film and copper in order to prevent copper diffusion. .

  The flexible wiring board formed as described above may be used as it is, but preferably it is used with a coverlay attached for protection. In this case, a coverlay in which an adhesive layer is formed on a polyimide film is usually used. Here, the polyimide film used for the coverlay is not particularly limited, but a polyimide film having the same or similar composition as that used for the flexible wiring board is preferably used. Moreover, as a coverlay adhesive, an epoxy resin, an acrylic resin, a polyimide resin, or the like is used. The coverlay may protect the entire wiring, or may protect only the portion excluding the semiconductor mounting portion. The coverlay is usually bonded to the wiring board with a polyimide film pre-applied on the wiring board. In some cases, the adhesive is applied to the wiring board, and then the polyimide film is applied. May be attached.

  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 an 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, heat shrinkage rate, friction coefficient (static friction coefficient), automatic optical inspection (AOI), inorganic particle evaluation, and the number of abnormal protrusions are as follows. It measured by the method of (1)-(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 a measurement temperature range: 50 to 200 ° C and a 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 fixed at 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 determined. 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 polyamic acid. A conversion agent composed 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. In this mixture, particles having a particle size of 0.01 μm or more and 1.5 μm or less, an average particle size of 0.30 μm, and a particle size of 0.15 to 0.60 μm were 87.2% by volume in all particles. The N, N-dimethylacetamide slurry of silica was added to the varnish-like polyamic acid solution in an amount of 0.3% by weight per resin weight, sufficiently stirred and dispersed, and then rotated by a T-type slit die made of stainless steel at 100 ° C. Casting on a drum, a gel film having a self-supporting property of 55% by weight of residual volatile components and a thickness of about 0.20 mm was obtained. 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. Table 1 shows the physical properties of this polyimide film.

(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. 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 composed 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. In this mixture, 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 were 86.3% by volume in all particles. The N, N-dimethylacetamide slurry of silica was added to the varnish-like polyamic acid solution in an amount of 0.35% by weight per resin weight, sufficiently stirred and dispersed, and then rotated by a T-type slit die made of stainless steel at 100 ° C. The gel film was cast on a drum to obtain a self-supporting gel film having a residual volatile component of 55% by weight and a thickness of about 0.10 mm. 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. . Table 1 shows the physical properties of this polyimide film.

(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. 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 composed 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. In this mixture, the particle size is 0.01 μm or more and 1.5 μm or less, the average particle size is 0.45 μm, and the particle size is 0.15 to 0.60 μm. The silica N, N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution in an amount of 0.3% by weight per resin weight, sufficiently stirred and dispersed, and then cast onto an endless belt from a T-shaped slit die. The gel film was heated with hot air at 70 ° C. to obtain a self-supporting gel film having a residual volatile component of 55% by weight and a thickness of about 1.00 mm. 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. Table 1 shows the physical properties of this polyimide film.

(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. A conversion agent composed 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. In this mixture, particles 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 are 87.0% by volume in all particles. The N, N-dimethylacetamide slurry of silica was added to the varnish-like polyamic acid solution in an amount of 0.5% by weight per resin weight, sufficiently stirred and dispersed, and then cast onto an endless belt from a T-shaped slit die. The gel film was heated with hot air at 50 ° C. to obtain a self-supporting gel film having a residual volatile component of 55% by weight and a thickness of about 0.20 mm. 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. Table 1 shows the physical properties of this polyimide film.

(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. A polyimide film was prepared 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. Got. 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. A polyimide film was prepared in the same manner as in Synthesis Example 3, except that the silica was changed to 31.4% by volume and N, N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution at 0.35% by weight per resin weight. Got. 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. A polyimide film was prepared in the same manner as in Synthesis Example 4 except that 72.6% by volume of silica was used and 0.35% by weight of N, N-dimethylacetamide slurry was added to the varnish-like polyamic acid solution per resin weight. Got. Table 1 shows the physical properties of this polyimide film.

(Synthesis Example 9)
50 parts by weight of epoxy resin “Epicoat” 834 manufactured by Yuka Shell Co., Ltd., 100 parts by weight of phosphorus-containing epoxy resin FX279BEK75 manufactured by Tohto Kasei Co., Ltd., 6 weights of curing agent 4,4′-DDS manufactured by Sumitomo Chemical Co., Ltd. Part, JSR NBR (PNR-1H) 100 parts by weight, Showa Denko Co., Ltd. aluminum hydroxide 30 parts by weight methyl isobutyl ketone 600 parts by stirring at 30 ° C. and mixed, adhesive solution Got.

(Synthesis Example 10)
50 parts by weight of epoxy resin “Epicoat” 828 manufactured by Yuka Shell Co., Ltd., 80 parts by weight of phosphorus-containing epoxy resin FX279BEK75 manufactured by Tohto Kasei Co., Ltd., 6 weights of curing agent 4,4′-DDS manufactured by Sumitomo Chemical Co., Ltd. Part, JSR Co., Ltd. NBR (PNR-1H) 100 parts by weight, Showa Denko Co., Ltd. 10 parts by weight of aluminum hydroxide was mixed with methyl isobutyl ketone 600 parts by weight at 30 ° C., and the adhesive solution Got.

[Example 1]
Using the polyimide film formed in Synthesis Example 1, the adhesive of Synthesis Example 9 was applied to one side of the polyimide film and dried by heating at 150 ° C. for 5 minutes to form an adhesive layer having a dry film thickness of 10 μm. This polyimide film with a single-sided adhesive and 1/2 ounce copper foil (manufactured by Nikko Gould Foil Co., Ltd., JTC foil) were laminated at a laminating temperature of 160 ° C. and a laminating pressure of 196 N / cm (20 kgf / cm) using a hot roll laminator. cm) and laminating speed of 1.5 m / min, thermal lamination was performed to produce a single-sided flexible copper-clad plate.

Using the obtained copper-clad plate, a photoresist AZP4620 manufactured by Clariant Japan Co., Ltd. was formed on a single-sided copper foil with a film thickness of 10 μm after drying at 105 ° C. for 10 minutes, and line width / space width = 35 μm / 35 μm. Using a glass photomask manufactured by Mitani Electronics Co., Ltd. in which a comb-shaped pattern of No. 1 is disposed, exposure is performed at 400 mJ / cm ² (full wavelength), and development is performed with a developer of AZ400K / water = 25/75 (weight ratio). The photoresist was patterned into a comb shape. Then, copper etching was performed at 40 ° C. for 90 seconds using a 30 wt% aqueous solution of iron chloride to remove the copper where the photoresist was not formed. After the copper etching was completed, the photoresist was peeled off at 40 ° C. for 1 minute using a 2.5 wt% sodium hydroxide aqueous solution. In this way, a circuit pattern of line / space = 35/35 μm was formed on one side to obtain a single-sided flexible printed wiring board.

  The static friction coefficient, AOI, and number of abnormal protrusions of the polyimide film part of the obtained single-sided flexible printed wiring board were measured. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, a flexible wiring board 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 as in Example 1. Evaluation was conducted. The results are shown in Table 1. The coefficient of static friction exceeded 1 and the running performance was extremely bad.

[Example 2]
The polyimide film formed in Synthesis Example 2 was used, and the adhesive of Synthesis Example 10 was applied to both sides of the polyimide film, followed by heating and drying at 150 ° C. for 5 minutes to form an adhesive layer having a dry film thickness of 10 μm. This polyimide film with double-sided adhesive and 1/2 ounce copper foil (manufactured by Nikko Gould Foil Co., Ltd., JTC foil) were laminated at a laminating temperature of 160 ° C. and a laminating pressure of 196 N / cm (20 kgf) using a hot roll laminator. / Cm) and a laminating speed of 1.5 m / min were used for thermal lamination to produce a double-sided flexible copper-clad plate.

Using the obtained copper-clad plate, a photoresist AZP4620 manufactured by Clariant Japan Co., Ltd. was formed on both sides of the copper foil with a film thickness of 10 μm after drying at 105 ° C. for 10 minutes, and line width / space width = 25 μm / 25 μm. Using a glass photomask manufactured by Mitani Electronics Co., Ltd. in which a comb-shaped pattern of No. 1 is disposed, exposure is performed at 400 mJ / cm ² (full wavelength), and development is performed with a developer of AZ400K / water = 25/75 (weight ratio). The photoresist was patterned into a comb shape. Thereafter, copper etching was performed at 40 ° C. for 2 minutes using a 30% by weight aqueous solution of copper chloride to remove the copper where the photoresist was not formed. After the copper etching was completed, the photoresist was peeled off at 40 ° C. for 1 minute using a 2.5 wt% sodium hydroxide aqueous solution. In this way, a circuit pattern of line / space = 25/25 μm was formed on both sides to obtain a double-sided flexible printed wiring board.

  The static friction coefficient, AOI, and number of abnormal protrusions of the polyimide film portion of the obtained double-sided flexible printed wiring board were measured. The results are shown in Table 1.

[Comparative Example 2]
In Example 2, a flexible wiring board 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 as in Example 2. Evaluation was conducted. The results are shown in Table 1. There were many abnormal protrusions and the AOI was also poor.

[Example 3]
The polyimide film formed in Synthesis Example 3 was used, the vacuum chamber was brought to an ultimate pressure of 1 × 10 ⁻³ Pa, and then nickel / chromium = 95/5 by DC magnetron sputtering at an argon gas pressure of 1 × 10 ⁻¹ Pa. (Weight ratio) nichrome alloy was sputtered on one side so as to have a thickness of 5 nm, and copper was further sputtered so as to have a thickness of 50 nm. Next, a copper layer having a thickness of 6 μm was laminated by electrolytic plating using a copper sulfate bath under the condition of a current density of ² A / dm ² to prepare a single-sided flexible copper-clad plate. The composition of the copper sulfate bath was a solution in which an appropriate amount of additives was added to copper sulfate pentahydrate 80 g / liter, sulfuric acid 200 g / liter, and hydrochloric acid 50 mg / liter.

Using the obtained copper-clad plate, a photoresist AZP4620 made by Clariant Japan Co., Ltd. was formed on a single-sided copper foil with a film thickness of 5 μm after drying at 105 ° C. for 10 minutes, and the line width / space width = 15 μm / 15 μm Using a glass photomask manufactured by Mitani Electronics Co., Ltd., in which a comb-shaped pattern is arranged, exposure is performed at 400 mJ / cm ² (full wavelength), development is performed with a developer of AZ400K / water = 25/75 (weight ratio), and photo The resist was patterned into a comb shape. Then, copper etching was performed at 40 ° C. for 90 seconds using a 30 wt% aqueous solution of iron chloride to remove the copper where the photoresist was not formed. After the copper etching was completed, the photoresist was peeled off at 40 ° C. for 1 minute using a 2.5 wt% sodium hydroxide aqueous solution. In this way, a circuit pattern of line / space = 15/15 μm was formed on one side to obtain a single-sided flexible printed wiring board.

  The static friction coefficient, AOI, and number of abnormal protrusions on the polyimide film side of the obtained single-sided flexible printed wiring board were measured. The results are shown in Table 1.

[Comparative Example 3]
In Example 3, a flexible wiring board 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 as in Example 3. Evaluation was conducted. The results are shown in Table 1. The coefficient of static friction exceeded 1 and the running performance was extremely bad.

[Example 4]
The polyimide film formed in Synthesis Example 4 was used, the vacuum chamber was brought to the ultimate pressure of 1 × 10 ⁻³ Pa, and then nickel / chromium = 90/10 (by DC magnetron sputtering at an argon gas pressure of 1 × 10 ⁻¹ Pa. (Weight ratio) nichrome alloy was sputtered on both sides to a thickness of 3 nm, and copper was further sputtered to a thickness of 10 nm. Next, a copper layer having a thickness of 5 μm was laminated by electrolytic plating using a copper sulfate bath under the condition of a current density of ² A / dm ² to prepare a double-sided flexible copper-clad plate. The composition of the copper sulfate bath was a solution in which an appropriate amount of additives was added to copper sulfate pentahydrate 80 g / liter, sulfuric acid 200 g / liter, and hydrochloric acid 50 mg / liter.

Using the obtained copper-clad plate, a photoresist Opt ER N-350 made by Nippon Paint Co., Ltd. was formed on a double-sided copper foil with a film thickness of 5 μm after drying at 105 ° C. for 5 minutes, and the line width / space width = Using a glass photomask manufactured by Mitani Electronics Co., Ltd., on which a 35 μm / 35 μm comb-shaped pattern is arranged, exposure is performed at 50 mJ / cm ² (full wavelength), and development is performed using a 1% by weight aqueous solution of sodium carbonate. Was patterned into a comb shape. Then, copper etching was performed at 40 ° C. for 90 seconds using a 30 wt% aqueous solution of iron chloride to remove the copper where the photoresist was not formed. After the copper etching was completed, the photoresist was peeled off at 40 ° C. for 1 minute using a 2.5 wt% sodium hydroxide aqueous solution. In this way, a circuit pattern of line & space = 35/35 μm was formed on both sides to obtain a double-sided flexible printed wiring board.

  The static friction coefficient, AOI, and number of abnormal protrusions on the polyimide film side of the obtained double-sided sibling printed wiring board were measured. The results are shown in Table 1.

[Comparative Example 4]
In Example 4, a flexible wiring board 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 as in Example 4. Evaluation was conducted. The results are shown in Table 1. There were many abnormal protrusions and the AOI was also poor.

  The flexible wiring board of the present invention has characteristics that can be applied to AOI, can form fine wiring, has good running properties (slidability), and does not deform even when lead-free solder is used. It is extremely useful as a high-performance flexible printed circuit board (FPC) that forms fine wiring.

Claims (12)

3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as the diamine component, pyromellitic dianhydride as the acid dianhydride component, and an average particle size of 0.01 to 1.5 μm. Using a polyimide film in which a powder mainly composed of inorganic particles of 0.05 to 0.7 μm is dispersed in the film at a ratio of 0.1 to 0.9% by weight per film resin weight, A flexible printed wiring board, wherein wiring is formed on one side or both sides via an adhesive. 3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as the diamine component, pyromellitic dianhydride as the acid dianhydride component, and an average particle size of 0.01 to 1.5 μm. Using a polyimide film in which a powder mainly composed of inorganic particles of 0.05 to 0.7 μm is dispersed in the film at a ratio of 0.1 to 0.9% by weight per film resin weight, A flexible printed wiring board, wherein wiring is formed on one side or both sides without an adhesive. 3,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl ether as the diamine component, pyromellitic dianhydride as the acid dianhydride component, and an average particle size of 0.01 to 1.5 μm. Using a polyimide film in which a powder mainly composed of inorganic particles of 0.05 to 0.7 μm is dispersed in the film at a ratio of 0.1 to 0.9% by weight per film resin weight, A flexible printed wiring board, wherein wiring is formed on one side without an adhesive and on the other side without an adhesive. The proportion of each component in the polyimide film is 10 to 50 mol% paraphenylenediamine and 50 to 90 mol% 4,4'-diaminodiphenyl ether as a diamine component, and 100 mol% pyromellitic as an acid dianhydride component. It consists of an acid dianhydride, The flexible printed wiring board of any one of Claims 1-3 characterized by the above-mentioned. Polyimide film has 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 heating at 200 ° C. for 1 hour. The flexible printed wiring board according to claim 1, wherein the shrinkage rate is 0.10% or less. The flexible printed wiring board according to any one of claims 1 to 5, wherein the wiring is mainly made of copper. The flexible printed wiring board according to any one of claims 1, 3, 4, and 5, wherein the adhesive mainly comprises at least one selected from an epoxy resin, an acrylic resin, and a polyimide resin. The flexible printed wiring board according to claim 1, wherein the wiring is formed by etching a metal layer. The flexible printed wiring board according to claim 1, wherein the wiring is formed by plating. The flexible printed wiring board according to any one of claims 1 to 9, wherein a coverlay is laminated on the wiring. 11. The flexible wiring board 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 occupy a ratio of 80% by volume or more in all particles. . The flexible wiring board according to any one of claims 1 to 11, wherein in the film surface protrusions 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.