JPH0481504B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a flexible printed wiring board having excellent heat-resistant dimensional stability, solder resistance, electrical insulation, and mechanical properties. (Prior art) In recent years, flexible printed wiring boards (hereinafter broadly used to include flat cables and integrated circuit chip carrier tapes) have become increasingly popular as electronic devices become smaller, lighter, thinner, and more dense. , the demand for it is increasing. The base materials used for flexible printed wiring boards and their coverlay films are mainly polyethylene terephthalate film and polyimide film, with a small amount of glass cloth reinforced epoxy resin sheets and aramid paper also being used. . (Problems to be solved by the invention) Although polyester film has excellent mechanical properties, electrical properties, and chemical resistance, its heat resistance is not sufficient, and it ℃
Even when heated to such temperatures, the shrinkage rate is large and its use is severely restricted. Although polyimide film has excellent mechanical properties and heat resistance, it has poor water resistance, and requires sufficient moisture control during the coverlay lamination process and soldering process, as well as deterioration of electrical properties due to moisture absorption. . Another problem is that it is expensive. Although glass cloth-reinforced epoxy resin sheets have excellent electrical insulation, chemical resistance, and moisture resistance, they suffer from extremely poor flexibility, which is required for flexible printed wiring boards. In some cases, aramid paper (Nomex Paper manufactured by Dupont) is used in place of film.
There are many practical problems such as water resistance, dimensional change resistance, and curling. As described above, current flexible printed wiring boards each have their own problems. (Means for Solving the Problems) The present invention provides a new type of flexible printed wiring board that solves these problems. That is, the present invention provides a flexible material in which an electrically insulating layer made by impregnating a nonwoven fabric mainly composed of aromatic polyamide with a resin composition consisting of an epoxy resin and a rubber resin is used as a base material and/or a coverlay. It is a printed wiring board. In the nonwoven fabric mainly composed of aromatic polyamide used in the present invention, the type of aromatic polyamide (hereinafter referred to as aramid) is not particularly limited, but it usually consists of the following structural units. Formula 1: -HN-R ₁ -NHOCR ₂ CO- Formula 2: -HNR ₃ CO- (wherein R ₁ , R ₂ , R ₃ are substituted or unsubstituted aromatic rings,

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】 (However, X is -O-, -S-,

[Formula] −CH ₂ −,

[Formula] etc. Substituents for the aromatic ring of R ₁ , R ₂ and R ₃ include an alkyl group having 1 to 3 carbon atoms, a chlorine atom, a bromine atom, and a phenyl group. ) The aramid in the present invention includes aromatic polyamide polymers (including copolymers) having structural units represented by the above formula 1 and/or formula 2, preferably polymethaphenylene isophthalamide or polyparaphenylene isophthalamide. It is nylenterephthalamide. Aramid nonwoven fabric (including so-called paper in the present invention) can be produced by either a dry method or a wet method. The dry method includes a card method (web formation using woolen card, garnet, etc.) and an air flow method (land web, proctor web, hunter web), and the wet method uses an ordinary paper machine. The aramid nonwoven fabric of the present invention is particularly preferably formed by a dry method, an airflow method, or a wet method. This is because if the fiber orientation of the nonwoven fabric is directional, the mechanical properties, dimensional change rate, etc. of the flexible printed wiring board will be directional, which is not convenient. The bonding between the aromatic polyamide fibers in the nonwoven fabric may be mechanical bonding or/and bonding using a binder, but bonding using a binder is preferable for the nonwoven fabric used in the present invention (this is preferable for thin nonwoven fabrics). can get). Preferably used binders include aramid fibrous binders or thermoplastic heat-resistant polymer fibrous binders (polyesters such as polyethylene terephthalate, polyamides such as 6,6-nylon, polysulfone, polyphenylene sulfide). and so on. Of course, it is also possible to use water-soluble or water-dispersible binders, powdered binders, or dissected-soluble binders used for ordinary synthetic fiber nonwoven fabrics and paper. The nonwoven fabric mainly composed of aromatic polyamide of the present invention has an aramid component of 60% by weight, preferably 70% by weight.
It is contained in an amount of 90% by weight or more, particularly preferably 90% by weight or more.
The aramid component includes short aramid fibers and binders such as aramid fibrous binders (usually aramid fibrids). Components other than aramid in the nonwoven fabric are mainly binders other than aramid mentioned above, other short synthetic resin fibers, short glass fibers, short ceramic fibers, and the like. Aramid short fibers usually have a denier of 1.5 to 10 and a cut length of 5 to 100 mm, preferably 5 to 80 mm. The thickness of the aramid nonwoven fabric used in the present invention is 20μ
-150μ, preferably 30μ-60μ, and the basis weight is 10g/m ² -50g/m ² , preferably 15g/m ² -
It is 50g/ ^m2 . One feature of the flexible printed wiring board of the present invention is that it uses an electrical insulating layer made of an aramid nonwoven fabric impregnated with resin, and the resin is present inside the nonwoven fabric and on both surface layers. For this reason, conventional flexible printed circuit boards with aramid paper laminated together suffer from () curling, () poor water resistance, () deterioration due to penetration of chemicals into the insulating layer (structure of the aramid nonwoven fabric), and () While the flexible printed wiring board of the present invention has drawbacks such as a low translayer withstand voltage due to voids, these drawbacks can be overcome with the flexible printed wiring board of the present invention. In order to completely impregnate the resin into the aramid nonwoven fabric, the apparent density of the aramid nonwoven fabric used in the present invention is preferably 0.15 g/cm ³ to 0.5 g/cm ³ . It is preferable that the fiber component is contained in an amount of 60% by weight or more of the total weight. Furthermore, various surface treatments may be applied to improve the adhesion between the aramid paper and the resin. The resin constituting the insulating layer of the present invention has an epoxy resin/rubber resin ratio in the range of 20/80 to 70/30 (weight ratio). An epoxy resin is a compound containing one or more, preferably two or more epoxy rings in its molecule, and the curing agent, curing catalyst, etc. of the epoxy compound are not included in the weight of the epoxy resin. If the ratio of epoxy resin/rubber resin is less than 20/80,
Solder resistance, chemical resistance, and heat aging resistance deteriorate,
It's inconvenient. Moreover, if it is larger than 70/30, the flexibility will be poor, which is inconvenient. Epoxy compounds include bisphenol-type epoxy compounds obtained by reacting bisphenol with epichlorohydrin, novolak-type epoxy compounds obtained by reacting epichlorohydrin with novolak-type phenolic resins and cresol resins, and other glycerol-based epoxy compounds (glycerol diglycidyl). ether, etc.), cycloaliphatic epoxy compounds (cyclopentadiene dioxide, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, epoxy compounds derived from polybutadiene, etc.) , nitrogen-containing epoxy compounds, and halogenated epoxy compounds in which one or more hydrogen atoms of these epoxy compounds are brominated. Usually epoxy equivalent: 180~
Something around 1000 is preferable. As curing agents, amines (ethylenediamine, diethylenetriamine, triethylenetetramine, metaphenylenediamine, p, p'-diaminodiphenylmethane, naphthylenediamine, dicyandiamide, diphenyldiaminosulfone, imidazole derivatives, etc.), carboxylic acids or/and carboxylic Acid anhydrides (succinic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, 3,3',
4,4′-benzophenonetetracarboxylic anhydride, etc.), polyamide resin, polysulfide resin,
Examples include phenol-formalin resin, melamine resin, and aniline resin. Examples of the catalyst include Lewis acids (such as boron trifluoride), tertiary amines (such as dimethylbenzylamine), and quaternary ammonium salts. Among the resin components constituting the insulating layer of the present invention, epoxy resin has electrical insulation, mechanical properties, water resistance,
It is a resin with excellent solvent resistance, heat resistance, etc., and this resin component is effective in imparting the above-mentioned performance to printed wiring boards. On the other hand, since epoxy resin is usually hard and brittle, it is necessary to impart flexibility and toughness for use in flexible printed wiring boards, and a rubber-based resin component is added as a resin component that imparts flexibility and toughness. do. This component is preferably one that chemically bonds with the epoxy resin, but it may be simply mixed, or one part may be bonded and the other part may be mixed. Rubber resin components (or/and monomers or oligomers forming the resin component) that provide such flexibility and toughness include isoprene rubber, chloroprene rubber, nitrile/butadiene rubber, and acrylic. Examples include thermoplastic elastomers such as rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, silicone rubber, fluorine rubber, polyurethane (polyester urethane, polyether urethane, etc.), copolymer polyester, copolymer polyamide, and the like. The resin of the present invention may contain lubricants (silica, talc, silicone, etc.), flame retardants (halides, phosphorus compounds, aluminum hydroxide, antimony trioxide, etc.), and stabilizers within the range that does not impair the performance of the present invention. agents (antioxidants, ultraviolet absorbers, polymerization inhibitors, etc.),
A mold release agent (silicone type, fluorine type, inorganic type) and other inorganic or organic fillers (talc, titanium oxide, fluorine type polymer fine particles, pigment, dye, calcium carbide, etc.) may be added. Coverlay or/and electrically insulating layer specific to the present invention
And the flexible wiring board used as the base material is: (1) The base material is an electrically insulating layer unique to the present invention, and a conductor pattern is formed on at least one side of the base material. As a method for forming a conductor pattern,
Conventional techniques such as additive and subtractive methods (etched oil method) are used. In the case of the subtractive method, a sheet is produced in which a base material and metal foil (copper foil, aluminum foil, etc.) are laminated in advance. The metal foil and the base material may be laminated with an adhesive between them, or the base materials having adhesive properties may be laminated without using an adhesive. (2) This is a case where the electrical insulating layer unique to the present invention is used for a coverlay of a flexible printed wiring board. When using a resin sheet containing aramid nonwoven fabric in advance and coating it with adhesive in the same form as a normal coverlay film, if the resin layer itself containing aramid nonwoven fabric has adhesive properties, it may be necessary to use adhesive. It can be used as a coverlay without coating. The electrical insulating layer unique to the present invention may be used only in the base material of the flexible printed wiring board in (1) above, or may be used only in the coverlay in (2) above,
It may also be used in conjunction with (1) and (2) above. Base material or/
When the electrical insulating layer of the present invention is used as a coverlay, the heat resistance and dimensional stability required for a flexible printed wiring board and the stiffness of the wiring board as a whole (this is difficult to achieve during component mounting and other processing). or provide useful tools to improve workability during handling. At the same time, this electrical insulating layer has electrical insulation, solder resistance, chemical resistance, tear resistance,
It has excellent flexibility. A method for forming an electrically insulating layer in which a nonwoven fabric mainly composed of aromatic polyamide, which is unique to the present invention, is impregnated with resin will be described. The nonwoven fabric described above is impregnated with an epoxy resin solution, and if necessary, after drying the solvent,
Just let it harden. However, when bonding metal foils together without using an adhesive or bonding them to a wiring board as a coverlay, it is necessary to bond them together using heat and pressure while they still have thermal adhesive properties, and then cure them. , forming an electrically insulating layer with desired performance. Instead of impregnating the aramid nonwoven fabric with a resin solution, a solid resin sheet is formed in advance, and the aramid nonwoven fabric is sandwiched between them and heated and pressurized to form an electrically insulating layer of the aramid nonwoven fabric impregnated with resin. It is also possible to form. A commonly used horizontal and/or vertical impregnation machine can be used to impregnate the aramid nonwoven fabric with the resin solution, and impregnation can be performed once or multiple times. Furthermore, it is also possible to apply coating from one side of the aramid nonwoven fabric, and then, if necessary, to coat from the opposite side, a so-called coating method. No special drying is required after impregnation and/or coating. If the impregnated sheet after drying is sticky, a release sheet may be optionally used in an appropriate step. As the release sheet, ordinary cellulose paper or film coated with a release agent, polypropylene film, polyvinyl alcohol film, etc. can also be used as they are. (Effects of the Invention) As described above, the printed wiring board of the present invention () uses aramid nonwoven fabric as a reinforcing material, has excellent thermal dimensional stability, is flexible, and is strong at the same time. , has excellent workability, () has a structure in which the aramid nonwoven fabric exists inside the resin layer, which (a) prevents curling of flexible printed circuit boards; and (b) improves water resistance, which is a disadvantage of aramid paper. (3) There is no penetration of chemicals into the nonwoven fabric, (d) Few voids, and () Excellent electrical insulation properties of epoxy resin. It has characteristics such as being endowed with flexibility and toughness through modification while retaining water resistance and mechanical properties, and can exhibit well-balanced performance as a flexible printed wiring board. (Example) Next, the present invention will be explained in more detail with reference to Examples. The measurement method used in the examples is as follows. (1) Perform circuit formation using the following steps. () Print a circuit pattern on the copper surface of the copper-clad sheet with UV-curable etching resist ink UER110 (blue) manufactured by Toyobo Co., Ltd. using a 300-mesh polyester fiber-covered screen. () Irradiate 700mJ/ ^cm2 with a high-pressure mercury lamp to harden the resist. () Using a 38-40° Baume ferric chloride solution,
Etched at 40℃ for 100 seconds. () Peel off the etching resist with a 4% by weight aqueous caustic soda solution. () A desired circuit is formed by washing with water and drying. (2) Electrical insulation resistance Using the circuit formation method in (1), a test pattern was formed with a circuit width of 1.0 mm, distance between circuits of 1.0 mm, circuit length of 25 mm, and a land for electrode connection (circular shape with a diameter of 5 mm). Measure the electrical resistance after applying 500V DC to both ends for 1 minute. Measuring instrument: Yokogawa Heuretsu Packard High Insulation Resistance Meter 4329A (3) Electrical breakdown voltage Using the same pattern as for measuring electrical insulation resistance in (2), apply 0.2 AC and read the voltage at which the insulation breaks down. . Measuring instrument: Kokuyo Electric Industry Co., Ltd. Voltage-proof insulation automatic tester
MODEL MS-5 (4) Copper foil peel strength A copper foil pattern with a width of 1 mm and a length of 100 mm was made using the circuit formation method described in (1) and peeled off at 90° using IPC FC241. Tensile speed: 50 mm/〓, Measuring device: Toyo Seiki Co., Ltd. Tensilon UTM-type (5) Folding strength: 2 at the center of a 15 mm wide board using the circuit formation method described in (1).
Create a mm copper foil pattern using the MIT method (JIS P8115)
The number of times it took to break the conduction was determined using a load of 500gR = 1.0mm. (6) Heat shrinkage rate (dimensional change rate) Determine the heat shrinkage rate before and after treatment at 150°C for 30 minutes using IPC FC241 C method. (7) Solder resistance Observe swelling and color change according to JIS C6481.
Post flux uses solder light MH820V manufactured by Tamura Chemical Research Institute.

【table】

[Table] Example 1 Bisphenol A type epoxy resin Epicoat
828 (Ciel Sekiyu Co., Ltd.) 60g, acrylonitrile/butadiene copolymer Nipol 1001B (Nippon Zeon Co., Ltd.)
) 40g, curing catalyst, Kyuazol 2E4MZ: 2-
Ethyl-4-methylimidazole (Shikoku Kasei Co., Ltd.)
A resin solution was prepared by dissolving 2g of the product (manufactured by the company) in 150g of methyl ethyl ketone. Aramid nonwoven fabric ANW-1 shown in Table 1 was impregnated with the above solution, dried at 60°C for 2 minutes and at 100°C for 2 minutes,
A resin-impregnated aramid nonwoven fabric sheet with a resin adhesion amount of 70 g/m ² was produced. On the other hand, apply the above resin solution to 35μ electrolytic copper foil (Nippon Mining Co., Ltd.).
JTC foil) applied, dried, and resin coated (15g/m2 ⁾
DRY) Copper foil was manufactured, and the copper foil and the resin-impregnated sheet were roll laminated at 100℃ and 11.8Kg/cm, and then pressed between rolls at 150℃ and 10Kg/cm, and then at 130℃ for 16 hours. Resin sheet copper clad board (120μ) cured and reinforced with aramid nonwoven fabric
was manufactured. Table 2 shows the performance of the flexible printed wiring board manufactured from this copper clad board. Example 2 Novolac type epoxy resin Epicoat 154 (Ciel Sekiyu Co., Ltd.) 60g, polyepichlorohydrin
A resin solution was prepared by dissolving 40 g of HERCLOR 100H (Nippon Zeon Co., Ltd.) and 2 g of curing catalyst Kyuazol 2E4MZ (Shikoku Kasei Co., Ltd.) in 150 g of methyl ethyl ketone. The aramid nonwoven fabric (ANW-2) shown in Table 1 was impregnated with the above solution and dried at 60°C for 2 minutes and at 100°C for 2 minutes to produce a resin-impregnated aramid nonwoven fabric sheet with a resin adhesion amount of 80 g/m ² . On the other hand, the resin solution was applied to a 35μ electrolytic copper foil (TSTO-HD foil manufactured by Furukawa Circuit Oil Co., Ltd.) and dried to produce a resin-coated (15 g/m ² DRY) copper foil. Copper foil and the above resin impregnated sheet at 100℃, 12Kg/
After roll lamination at cm, further 150℃, 10
After pressing between rolls at Kg/cm, 16 at 130℃
A resin sheet copper clad plate (130μ) was manufactured by curing for a period of time and reinforced with aramid nonwoven fabric. Table 2 shows the performance of the flexible printed wiring board manufactured from this copper clad board. Example 3 60 g of brominated novolac type epoxy resin Blen S (manufactured by Nippon Kayaku Co., Ltd.), 40 g of chlorosulfonated polyethylene Hypalon 20 (manufactured by Dupont Co., Ltd.), and 2 g of curing catalyst Kyuazol 2E4MZ (manufactured by Shikoku Kasei Co., Ltd.). A resin solution was prepared by dissolving in 40 g of methyl ethyl ketone and 160 g of toluene. The aramid nonwoven fabric (ANW-3) shown in Table 1 was impregnated with the above solution and dried at 60°C for 2 minutes and at 100°C for 2 minutes to produce a resin-impregnated aramid nonwoven fabric sheet with a resin adhesion amount of 70 g/m ² . On the other hand, the resin solution was applied to a 35μ electrolytic copper foil (TSTO-HD foil manufactured by Furukawa Circuit Oil Co., Ltd.) and dried to produce a resin-coated (15 g/m ² DRY) copper foil. Copper foil and the above resin impregnated sheet at 150℃, 12Kg/
After roll lamination at cm, the resin sheet was further cured at 130°C for 16 hours to produce a resin sheet copper clad board (110μ) reinforced with aramid nonwoven fabric. Table 2 shows the performance of the flexible printed wiring board manufactured from this copper clad board. Example 4 Novolac type epoxy resin Epicoat 154 (Ciel Sekiyu Co., Ltd.) 17 g, brominated novolac type epoxy resin Blen S (Nippon Kayaku Co., Ltd.) 43 g, acrylic copolymer (acrylic rubber) Nipole AR31
(Nippon Zeon Co., Ltd.) 40g, curing catalyst Kyuazol
2E4MZ (Shikoku Kasei Co., Ltd.) 2g to methyl ethyl ketone
150g to prepare a resin solution. The aramid nonwoven fabric (ANW-4) shown in Table 1 was impregnated with the above solution to produce a resin-impregnated aramid nonwoven fabric sheet with a resin adhesion amount of 70 g/m ² . On the other hand, the above resin solution was applied to a 35μ electrolytic copper foil (TSTO-HD foil manufactured by Furukawa Circuit Oil Co., Ltd.) and dried to produce a resin-coated (15 g/m ² DRY) copper foil. Copper foil and the above resin impregnated sheet at 150℃, 12Kg/
After roll lamination at cm, the resin sheet was further cured at 130°C for 16 hours to produce a resin sheet copper-clad board (120μ) reinforced with aramid nonwoven fabric. Table 2 shows the performance of the flexible printed wiring board manufactured from this copper clad board. Example 5 The aramid nonwoven fabric ANW-4 listed in Table 1 was impregnated with the resin solution used in Example 1, and heated at 60°C for 2 minutes.
After drying at 100℃ for 2 minutes, sandwich it between the release agent coated sides of a 25μ mold release agent coated polyester film and a 125μ mold release agent coated polyester film.
Laminated at 150℃ and press pressure 15Kg/cm (impregnated amount
50g/ ^m2 ). Peel off the 25μ mold release agent-coated polyester film (this has better mold release properties) and attach the aramid-impregnated sheet surface to a polyimide-based flexible printed wiring board (Nitsukan Kogyo Co., Ltd. Nikaflex F-).
(manufactured from 30T25C11) was laminated on the circuit surface. Next, after pressing at 150°C, post-curing was performed at 100°C for 16 hours. After lamination, the 125μ polyester film was peeled off to form a coverlay layer reinforced with aramid nonwoven fabric. The performance of the laminate is shown in Table 2. Comparative Example 1 A flexible printed wiring board (Nicalex F- manufactured by Nikkan Kogyo Co., Ltd.) in which Du Pont's aramid nonwoven fabric and Nomex paper are bonded to copper foil using an adhesive (epoxy resin).
Table 3 shows the performance of the flexible printed wiring board (manufactured from 20VC150C11), which showed significant curling after etching and was very poor in terms of workability. Comparative Examples 2 and 3 A flexible copper-clad flexible printed wiring board was manufactured in exactly the same manner as in Example 1 except that the following resin composition solution was used. Resin solution composition used in Comparative Example 2 Bisphenol A type epoxy resin (Epicote 828 manufactured by Ciel Sekiyu Co., Ltd.) 15 g Acrylonitrile/butadiene copolymer (Nipole 1001B manufactured by Nippon Zeon Co., Ltd.) 85 g Curing catalyst 2-ethyl-4 -Methylimidazole (Kyuazole 2E4MZ manufactured by Shikoku Kasei Co., Ltd.) 2g Methyl ethyl ketone 150g Resin solution composition used in Comparative Example 3 Bisphenol A type epoxy resin (Epicote 828 manufactured by Ciel Sekiyu Co., Ltd.) 80g Acrylonitrile/butadiene copolymer (Japan) Nipole 1001B (manufactured by Zeon Co., Ltd.) 20 g Curing catalyst 2-ethyl-4-methylimidazole (Kyuazol 2E4MZ, manufactured by Shikoku Kasei Co., Ltd.) 2 g Methyl ethyl ketone 150 g Comparative example 4 Glass paper (basis weight) instead of aromatic polyamide nonwoven fabric ANW-1 A copper clad board and a printed wiring board were manufactured in exactly the same manner as in Example 1, except that a copper clad plate (30 g/m ² , 100 μm) was used. The performance is shown in Table 3.

[Table] Copper foil peel strength was measured by peeling parallel to the machine direction.

【table】

[Table] As is clear from Tables 2 and 3, the flexible printed wiring board of the present invention has electrical insulation,
Excellent performance in copper foil peeling, bending strength, heat shrinkage rate, solder resistance, and no curling after etching. If the ratio of the epoxy resin to the rubber resin is outside the range of the present invention, the solder resistance and heat aging resistance will be poor, or the flexibility will be poor.

Claims (1)

[Claims] 1 A nonwoven fabric whose main component is aromatic polyamide,
A flexible printed wiring board characterized in that an electrically insulating layer impregnated with a resin composition consisting of an epoxy resin and a rubber-based resin is used as a base material and/or a coverlay.