JP2002084050A - Flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-sided or double-sided flexible printed wiring board, which is modified in dimensional stability without marring the physical properties of the board, excellent in a migration resistance and suitable to a fine patterning. SOLUTION: A flexible printed wiring board is constituted using an electrically insulative film of a thickness of 10 to 30 μm, a bonding agent of a thickness of 5 to 15 μm, a copper foil of a thickness of 5 to 15 μm and a board of a total thickness of 20 to 60 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board used for a flexible printed wiring board and the like.

[0002]

2. Description of the Related Art A flexible printed wiring board is manufactured by laminating and integrating a metal foil on an electrically insulating film via an adhesive or directly, and a circuit is formed on a flexible printed wiring board. It is based on a coverlay film in which a material film and an adhesive are laminated and integrated. In recent years, as electronic devices have become smaller, lighter, and higher in density, flexible printed wiring boards have been required to have more advanced characteristics corresponding thereto. As these situations evolve,
Adhesion, heat resistance, flexibility,
Various properties such as electrical insulation are desired. In recent years, with the rapid progress of fine pattern formation due to high density, a lighter, higher adhesiveness and higher dimensional stability than before has been required. Conventionally, to solve these requirements, epoxy / acrylic, epoxy / NBR
Various adhesives such as epoxy-based and epoxy / polyester-based adhesives have been used, but for fine pattern applications, copper is directly laminated on the polyimide film due to problems such as dimensional stability of the polyimide film and deterioration of adhesiveness. Layer types are being considered.

[0003]

The method using an adhesive in each of the above-mentioned methods is, for example, a method using NBR having a functional group as an adhesive raw material, since excellent adhesiveness can be obtained, so that it is practically used. ing. However, in this case, the dimensional stability is significantly reduced, and it has been difficult to obtain high dimensional stability while maintaining high adhesiveness and other characteristics sufficient for producing a fine pattern circuit having a width of several tens of μm. . Further, in the case of the two-layer type, it is necessary to perform a complicated surface treatment in order to maintain the adhesiveness, but it is difficult to obtain stable adhesiveness, and the cost is increased. . An object of the present invention is to solve these problems.

[0004]

The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, the thickness of each of the constituent base materials is as follows, and the total thickness of the substrate is 20 to 6
It has been found that a single-sided flexible printed wiring board having a thickness of 0 μm solves the above problem. 1) The thickness of the electrically insulating film is 10 to 30 μm, 2) the thickness of the adhesive is 5 to 15 μm, and 3) the thickness of the copper foil is 5 to 15 μm. That is, the present invention seeks to provide a single-sided or double-sided flexible printed wiring board with improved dimensional stability suitable for fine patterning without impairing the physical properties of the flexible printed wiring board due to the substrate structure according to the present invention. Is what you do.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrically insulating film used in the present invention must have a thickness of 10 to 30 .mu.m. 10 μm electrical insulating film
If it is less than 10, the mechanical properties of the substrate for flexible printed wiring will be remarkably deteriorated, and the workability during production and processing will be remarkably reduced. If it is more than 30 μm, the flexibility will be reduced.
Examples of the electrically insulating film used in the present invention include a polyimide film, a polyester film, and a polyphenylene sulfide film. Among them, in order to sufficiently obtain the effects of the present invention, the elastic modulus is 3.0 to 8.0 G.
A polyimide film of Pa, more preferably, a polyimide film having an elastic modulus of 4.0 to 6.0 GPa is preferable. If the elastic modulus is less than 3.0 GPa, the dimensional stability is remarkably reduced in the shrinking direction. If the elastic modulus is more than 8.0 GPa, the polyimide film becomes hard and brittle, and the flexibility tends to decrease. In addition, one or both surfaces of these electrically insulating films may be subjected to a surface treatment. As the surface treatment, a low-temperature plasma treatment, a corona discharge treatment, a sandblast treatment or the like is preferable.

[0006] A method of producing a polyimide film is generally known in which a polyimide film is formed by reacting an aromatic dianhydride with an aromatic diamine to produce a polyamic acid, forming the polyamic acid into a film, and further heating or dehydrating imidation. I have. The mechanical properties of the polyimide film are derived from the chemical structures of the aromatic dianhydride and the aromatic diamine as raw materials, and the elastic modulus is favorably controlled by a combination of these. For example, pyromellitic dianhydride is used as the aromatic dianhydride, a mixture of 4,4 ^, -diaminodiphenyl ether and p-phenylenediamine is used as the aromatic diamine, and the mixing ratio of both is 90/10 to 10 by weight. The reaction was carried out by using the mixture at 40/60, and the obtained elastic modulus was 3.8 to 8.0.
A GPa polyimide film or the like is preferable. As the method for producing a polyimide film in the present invention, a known method of reacting an aromatic dianhydride with an aromatic diamine can be used. For example, a mixture of 4,4 ^, -diaminodiphenyl ether and p-phenylenediamine as an aromatic diamine is blended so that the weight ratio of both is 90/10 to 40/60, and the atmosphere of an inert gas such as nitrogen is mixed. Where N,
In a polar solvent such as N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone,
Finally, the solid content is dissolved so as to have a concentration of 5 to 30% by weight, the solution temperature is maintained at 0 to 30 ° C., and a diamine and an equivalent of pyromellitic dianhydride are substantially added, and the mixture is stirred for 1 to 10 hours. The polyamic acid solution is cast on a smooth surface, and 90-120
C. for 5 to 60 minutes, and partial imidization proceeded.
A self-supporting polyamic acid film is obtained. This film was fixed to a frame and heated at 150 to 200 ° C. for about 30 to 90 minutes to completely remove the solvent, and further heated at 300 to 450 ° C. for 1 to 90 minutes to complete imidization. Thus, a polyimide film is obtained. As a method of chemically imidizing, a polyimide film can be obtained by mixing a fatty acid anhydride such as acetic anhydride as a dehydrating agent and a nitrogen-containing compound such as isoquinoline as a dehydrating catalyst. In addition, the measurement of the elastic modulus of the polyimide film was performed according to ASTM D882.

[0007] The thickness of the copper foil to be laminated on the electrically insulating film via the adhesive layer used in the present invention needs to be 5 to 15 µm, and preferably 6 to 14 µm. If the thickness of the copper foil is thinner than 5 μm, the mechanical properties of the copper foil deteriorate, and the workability remarkably deteriorates. If the thickness is larger than 15 μm, it becomes difficult to sharpen the copper edge at the time of etching.
When fabricating a circuit having a fine pattern of μm or less, it is extremely difficult to adjust the distance between circuits to a desired value. Examples of the type of copper foil include a rolled copper foil, an electrolytic copper foil, and the like, and these can be used as appropriate according to the application.

The thickness of the adhesive used in the present invention must be 5 to 15 μm, preferably 6 to 1 μm.
0 μm. When the thickness of the adhesive is 5 μm or less, the adhesiveness is remarkably reduced, and sufficient adhesiveness cannot be obtained. When the thickness is 15 μm or more, the dimensional stability is reduced. The total thickness of the flexible printed wiring board is 20 μm to 60 μm.
m, preferably 20 μm to 50 μm. 20
If the thickness is smaller than μm, the strength is remarkably reduced, and it becomes extremely difficult to fabricate a substrate for flexible printed wiring. If the thickness is greater than 60 μm, the dimensional stability is reduced, and the present situation requires space saving and fine patterning.

The main components of the adhesive used in the present invention include epoxy / NBR resin, epoxy / acrylic resin, epoxy / polyester resin, epoxy / nylon resin, phenol / NBR resin, phenol / nylon. A resin or the like can be used.

In the present invention, the following composition is required as an adhesive composition in order to obtain more excellent high dimensional stability suitable for fabricating a fine pattern circuit while maintaining various characteristics. That is, A) 1 as an adhesive composition
Epoxy resin 10 having two or more epoxy groups in the molecule
0 parts by weight, B) 30 to 100 parts by weight of nitrile rubber, C)
1 to 30 parts by weight of a curing agent, D) one or more curing accelerators selected from imidazole compounds, tertiary amine tetraphenylborates, borofluorides and octylates 0.1 to 3 Parts by weight and the nitrile rubber is i) a nitrile rubber containing a carboxyl group and i
i) The content of acrylonitrile having no functional group at the terminal is 2
It is necessary to use an adhesive composition comprising a nitrile rubber of 5 to 45% by weight and a compounding ratio i) / ii) of 95/5 to 55/45.

The epoxy resin having two or more epoxy groups in one molecule of (A) in the adhesive composition used in the present invention includes bisphenol A type epoxy resin,
Bisphenol F-type epoxy resin, phenol novolak-type epoxy resin, alicyclic epoxy resin, glycidylamine-type epoxy resin, and halogenated epoxy resin can be used. Among these, a commercially available product is Epicoat (hereinafter sometimes abbreviated as EK) 8
28, 5050, 5049, 5048, 504
5, 154, 604, 1001 (trade name, manufactured by Japan Epoxy Resin), Sumiepoxy ELA115, 127, ESCN-195XL, ELM120, ESB
400 (trade name, manufactured by Sumitomo Chemical Co., Ltd.), BREN-S (trade name, manufactured by Nippon Kayaku Co., Ltd.), EP-4100 (trade name, manufactured by Asahi Denka Co., Ltd.)
Etc. are exemplified.

The nitrile rubber (acrylonitrile butadiene rubber: NBR) used in the present invention includes i) carboxyl group-containing NBR, ii)
NBR having no functional group is required. If the amount of the nitrile rubber is less than 30 parts by weight with respect to 100 parts by weight of (A), sufficient adhesiveness cannot be obtained, and if the amount is more than 100 parts by weight, heat resistance and electrical properties deteriorate. The compounding ratio i) / ii) is 9
If it exceeds 5/5, the adhesiveness is reduced, and furthermore, the dimensional stability is deteriorated, which is not preferable for the production of fine patterns. If it is smaller than 55/45, the electrical properties deteriorate. Examples of the NBR having a carboxyl group include, for example, a copolymer obtained by carboxylating the terminal group of a copolymer of acrylonitrile and butadiene and a copolymer rubber obtained by copolymerizing acrylonitrile, butadiene, and a monomer containing a carboxyl group. Can be These commercially available products include Nipol (hereinafter sometimes abbreviated as NP) 1072J and 1072J.
B, DN631, DN601 (trade name, manufactured by Zeon Corporation)
Is exemplified. As the NBR having no functional group, those having an acrylonitrile content of 25% by weight to 45% by weight are preferable from the viewpoints of adhesiveness, solvent resistance and the like. Commercial products include NP1031, 1032, 1001, and DN22
5, DN1041, DN1042, 1043, Zet
Examples are pole2000, 2020, and 3110 (trade names, manufactured by Zeon Corporation).

As the curing agent used in the present invention, known epoxy resin curing agents can be used. Examples thereof include aliphatic amine-based curing agents, alicyclic amine-based curing agents, aromatic amine-based curing agents, acid anhydride-based curing agents, dicyandiamide, and boron trifluoride amine complex salts. The compounding amount of these curing agents is required to be 1 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the epoxy resin. If the amount is less than 1 part by weight, sufficient curing of the epoxy resin cannot be obtained, and further, other properties, solvent resistance, electric properties, etc. are also reduced,
If it exceeds 30 parts by weight, the adhesiveness and solder heat resistance will be reduced.

The curing accelerator used in the present invention includes:
Imidazole compounds such as 2-alkyl 4-methylimidazoles; tertiary amine tetraphenylborates such as triethyleneammonium triphenylborate; borofluorides such as zinc borofluoride, tin borofluoride and nickel borofluoride Octylates such as tin octylate, zinc octylate and nickel octylate can be used. These can be used alone or in combination of two or more. Of these, borofluoride; octylate is preferred. The amount of these curing accelerators is 0.1% with respect to 100 parts by weight of the epoxy resin.
３3 parts by weight are required, and preferably 0.3-2.0 parts by weight. If the compounding amount of the accelerator is less than 0.1, the time required for curing becomes longer, the curing of the epoxy resin becomes insufficient, the migration resistance, electric properties, and solvent resistance decrease. The preservability of the agent deteriorates, the workability decreases, and further, the adhesiveness and solder heat resistance decrease.

In the adhesive composition used in the present invention, other resins and additives may be added as long as various properties are not reduced. Examples thereof include phenolic resins, zinc oxide having a vulcanizing effect, halides of organic compounds as flame retardants, antimony trioxide, aluminum hydroxide, and silicon dioxide.

Solvents used by mixing with the adhesive in the present invention include methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone, toluene, trichloroethylene, 1,4-dioxane, 1,3
-Dioxane, dioxolan and the like. The solid concentration of the solvent solution may be 10 to 45% by weight, preferably 20 to 35% by weight. If the solid content is more than 45% by weight, the coating property is deteriorated due to the increase in viscosity and the compatibility is lowered, and the workability is reduced. If the solid content is less than 10%, coating unevenness is liable to occur. Increases, causing environmental and uneconomical problems. These adhesive compositions are mixed using a pot mill, a ball mill, a roll mill, a homogenizer, a super mill, or the like.

The dimensional stability of the flexible printed wiring board of the present invention is calculated by the calculation formula described in the embodiment. Fabrication of a fine pattern circuit having a width requires a higher dimensional stability than before, and the value is preferably from -0.1% to + 0.1%.

Next, a method of manufacturing the flexible printed wiring board of the present invention will be described. An adhesive solution prepared by adding a predetermined amount of a solvent to the adhesive composition prepared in advance is applied to the electrical insulating film using a reverse roll coater, a comma coater or the like. This was treated with an inline dryer at 80 to 140 ° C. for 2 to 10 minutes to dry and remove the solvent of the adhesive to make it into a semi-cured state. cm, 6
Crimping is performed at 0 to 150 ° C. The obtained laminated film may be heated for further curing. The heating temperature is 8
The treatment is performed at 0 to 200 ° C. for 1 minute to 24 hours. The substrate for flexible double-sided printed wiring of the present invention is used when multilayering the circuit of the flexible wiring board, and the manufacturing method can be performed according to the above-mentioned method. In addition, by using a polyimide film having an elasticity of 3.8 to 8.0 GPa, an adhesive composition, and a copper foil, which belong to the scope of the present invention, the mutual balance between the electrically insulating film, the adhesive thickness, and the copper foil is good. Thus, a flexible printed wiring board is obtained in which dimensional stability is greatly improved while maintaining high adhesiveness, and which is suitable for producing a fine pattern with a copper circuit interval of 50 μm or less.

[0019]

Next, the present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited to these examples. In addition,% is weight%.

Method of measuring characteristic values (measurement of peel strength) A sample was cut into a circuit width of 1 mm in accordance with JIS C6481, and 50 mm in a 90 ° direction.
The force required to peel off to the copper foil side at a rate of / min is measured. (Solder heat resistance) According to JIS C6481, a sample is cut into a 25 mm square, floated on a flow solder for 30 seconds, and the maximum temperature at which swelling, peeling, etc. does not occur is measured.

(Dimensional stability) In accordance with IPC FC 241, heat treatment of flexible printed wiring board (150
(° C., 30 minutes), the change in the dimension in the application direction (MD) is determined by the following formula. Dimensional stability [%] = 100 × [(dimension after heat treatment) − (dimension before heat treatment)] / (dimension before heat treatment) (Solvent resistance test) 1 mm width flexible printed wiring board heated to 70 ° C. toluene Immersion for 10 minutes, and immediately lifted to perform the above-mentioned peel strength test. (Production of fine pattern circuit and its evaluation) 50 μm between lines
Etching the copper foil so that it becomes a circuit of m pitch,
A comb-shaped circuit was prepared, the cross section of the circuit was observed with a magnifying glass, and the presence or absence of a defective portion due to copper etching residue was evaluated. ：: no defective portion due to copper etching residue is not observed at all; △: defective portion due to copper etching residue is partially present; x: defective portion due to copper etching residue is observed in a considerable portion between lines. (Measurement of Elastic Modulus) The elastic modulus is measured in an atmosphere at a temperature of 25 ° C. based on ASTM D882.

Example 1 An adhesive having the composition shown in Table 1 was used and stirred with 500 g of MEK as a solvent.
The mixture was mixed and completely dissolved to obtain an adhesive solution having a solid concentration of 28%. Then, thickness 25μm, 200mm × 200m
m Kapton (a trade name of polyimide film manufactured by Toray DuPont) with a thickness of 10 μm after drying with an applicator.
The solution was applied so as to be thick, and the adhesive was semi-cured at 120 ° C. for 10 minutes using an inline dryer. A 14 μm thick, 200 mm × 200 mm JTC is applied to the adhesive-coated surface of this semi-cured film with adhesive.
(1/3 oz electrolytic copper foil manufactured by Japan Energy Co., Ltd.) are superimposed, heated and pressed by a roll laminator at a temperature of 100 ° C., a linear pressure of 100 N / cm, and a line speed of 2 m / min, and further heat-cured at 170 ° C. for 3 hours. Thus, a substrate for flexible printed wiring was obtained. Each characteristic of this flexible printed wiring board was measured by the above-mentioned method and is shown in Table 2.

(Examples 2 to 6) Same as Example 1 except that each of the adhesive compositions A, B, and C described in (Table 1) was used, and each of the base materials described in (Table 2) was used. Thus, a substrate for flexible printed wiring was produced. The characteristics of the flexible printed wiring board were measured in the same manner, and the results are shown in (Table 2). Apical used in Examples 3 and 5 is a trade name of a polyimide film manufactured by Kanegafuchi Chemical Co., Ltd.

Reference Example A method for producing a polyimide film used in Examples will be described below. As aromatic diamines, 4,4 ^, -diaminodiphenyl ether and p-
A 50/50 (weight ratio) mixture of phenylenediamine is dissolved in a N, N-dimethylformamide solution in a nitrogen gas atmosphere, and then pyromellitic diacid is added while cooling to keep the temperature of the solution at 25 ° C. The anhydride was slowly added so that the theoretical amount of the anhydride was finally equal to that of the aromatic diamine mixture, and the mixture was stirred and mixed for about 3 hours while maintaining the solution temperature at 25 ° C. I got This polyamic acid solution was applied on a glass plate using an applicator so that the film thickness finally became 25 μm, heated at 110 ° C. for 1 hour, dried, and desolvated to some extent. The polyamic acid film was peeled off from the glass plate, fixed on an iron frame, further heated at 200 ° C. for 1 hour to completely remove the solvent, further heated at 350 ° C. for 1 hour, dehydrated imidized, and elasticized. A polyimide film having a rate of 4.5 GPa was obtained.

(Examples 7 and 8) A flexible printed wiring board was prepared in the same manner as in Example 1 except that the polyimide films obtained in Reference Examples were used, and the substrates described in (Table 2) were used. Produced. These were measured for characteristic values in the same manner, and the results are shown in (Table 2).

(Comparative Examples 1 to 5) A flexible printed wiring board was prepared in the same manner as in Example 1 except that the composition of the base material described in Table 3 was used in accordance with each adhesive composition described in Table 1. Produced. The characteristics of the flexible printed wiring board were measured in the same manner, and the results are shown in (Table 3).

Hereinafter, the trade names and abbreviations used in Tables 1 to 3 will be described. EK5050: trade name of epoxy resin manufactured by Japan Epoxy Resin Co., Ltd. EK5045: trade name of epoxy resin manufactured by Japan Epoxy Resin Co., Ltd. NP-1072: carboxyl group-modified N manufactured by Zeon Corporation
BR trade name, NP-1001: NBR trade name manufactured by Zeon Corporation Nitrile amount 40.5%, NP-1032: NBR trade name manufactured by Zeon Corporation Nitrile amount 33.5%, DDM: 4,4′-diaminodiphenylmethane, DDS: 4,4'-diaminodiphenyl sulfone, JTC: Trade name of electrolytic copper foil manufactured by Japan Energy.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

(Summary of Examples) Comparing and examining the respective characteristic values of Examples 1 to 8 and Comparative Examples 1 to 5, the characteristic values of the examples are almost excellent. It can be seen that the circuit using the flexible printed wiring board of the example is superior to that of the comparative example. Also, from the results of Example 7, it can be seen that the combination of the inventions of the claims of the present invention greatly improves dimensional stability while maintaining high adhesiveness.

[0032]

According to the present invention, there is provided a single-sided or double-sided flexible printed wiring board having improved dimensional stability, excellent migration resistance, and suitable for fine patterning without impairing the physical properties of the flexible printed wiring board. be able to.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09J 201/00 C09J 201/00 H05K 1/02 H05K 1/02 B 3/38 3/38 E (72) Inventor Yoshiji Sakaguchi 1F, Towada, Kamisu-cho, Kashima-gun, Ibaraki Prefecture F-term (reference) in Shin-Etsu Chemical Co., Ltd. JG04A JK07A JK17 JL04 YY00 YY00A YY00B 4J040 CA071 CA072 EB031 EB032 EC001 EC041 EC061 EC071 EC121 EC151 ED001 ED002 EG001 EG002 GA07 HA32 HC05 HC08 HC24 JA09 JB02 KA16 KA17 A03 A02 A01 A03 A03 A02 MA03 A01 A03 A02 AA38 BB05 BB14 BB24 BB67 CC02 CC03 CC06 DD80 EE21 GG02 GG08

Claims (5)

[Claims] 1. A single-sided flexible printed wiring board, wherein the thickness of each of the constituent base materials has the following value, and the total thickness of the board is 20 to 60 μm. 1) The thickness of the electrically insulating film is 10 to 30 μm, 2) the thickness of the adhesive is 5 to 15 μm, and 3) the thickness of the copper foil is 5 to 15 μm. 2. The method according to claim 1, wherein the electrically insulating film has an elastic modulus of 3.0 to 3.0.
2. The flexible printed wiring board according to claim 1, wherein the substrate is a 8.0 GPa polyimide film. 3. An adhesive composition comprising: A) 100 parts by weight of an epoxy resin having two or more epoxy groups in one molecule; B) 30 to 100 parts by weight of a nitrile rubber; C) 1 to 30 parts by weight of a curing agent; ) One or more curing accelerators selected from imidazole compounds, tertiary amine tetraphenylborates, borofluorides and octylates; 0.1 to 3 parts by weight; and The nitrile rubber is composed of i) a nitrile rubber having a carboxyl group and ii) a nitrile rubber having a terminal acrylonitrile content of 25 to 45% by weight and having a compounding ratio i) / ii) of 95 / 5-
The flexible printed wiring board according to claim 1, wherein the ratio is 55/45. 4. The dimensional stability after heat treatment is -0.1% or more.
2. The flexible printed wiring board according to claim 1, wherein the content is + 0.1%. 5. A five-layer structure in which copper foil is laminated on both sides of an electrically insulating film via an adhesive, wherein the thickness of each of the constituent substrates is as follows, and the total thickness of the substrate is Is from 30 μm to 90 μm. 1) The thickness of the electrically insulating film is 10 to 30 μm, 2) the thickness of the adhesive is 5 to 15 μm, and 3) the thickness of the copper foil is 5 to 15 μm.