JP2011228493A - Method for manufacturing flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flexible wiring board which can simplify a manufacturing process, reduce a manufacturing cost and also allow for continuous production.SOLUTION: The method for manufacturing a flexible wiring board includes: a conductive layer forming step of forming a copper foil 12 having a through hole-forming portion, on one main face of a resin layer 11 containing an alkali soluble resin composition; a through hole forming step of melting and removing the resin layer 11 of blind via-forming portions 12a-12c through the copper foil 12 to form through holes 15a-15c; a blind via forming step of providing a copper foil 16 on the other main face of the resin layer 11 having the through holes 15a-15c formed therein to form blind vias 17a-17c; and a plating step of providing a copper plating film 18 over the blind vias 17a-17c to electrically connect the copper foil 12 with the copper foil 16.

Description

  The present invention relates to a method for manufacturing a flexible wiring board used in electronic equipment and the like, and more particularly to a method for manufacturing a flexible wiring board that can be suitably used in a build-up method.

  In recent years, flexible wiring boards employed in mobile phone terminals and the like have been required to have finer and multilayered (double-sided or multilayered) wiring circuits in order to improve component mounting density. As a result, the ratio of double-sided flexible wiring boards and multilayer flexible wiring boards has increased, and the production volume has increased rapidly.

  Conventionally, in a manufacturing process of a double-sided flexible wiring board or a multilayer flexible wiring board, interlayer connection of each conductive layer has been performed by through vias formed using drilling. Recently, in order to increase the wiring density, flexible wiring boards in which each conductive layer is interlayer-connected by blind vias formed using laser processing are increasing. However, in laser processing, since holes are processed one by one, production efficiency is poor, and laser processing debris (smear) must be removed after laser processing, which is a major obstacle to cost reduction. Moreover, since it is necessary to perform blind via formation at the beginning of the manufacturing process, it is a major obstacle to expansion of continuous production by roll-to-roll.

  Blind via formation technology is widely used for double-sided flexible boards mainly used as the core board of double-sided flexible wiring boards, multilayer flexible wiring boards, or rigid / flexible wiring boards. Double-sided flexible boards include double-sided flexible boards with adhesive, with copper foil attached to both sides of polyimide film, and double-sided flexible boards without adhesive, with copper foil attached to both sides of polyimide resin, but blind When forming a via, a double-sided flexible substrate without an adhesive is generally used because of laser processability. The outline of the blind via forming technique used for the double-sided flexible wiring board and the multilayer flexible wiring board will be described below.

  FIG. 5A to FIG. 5F schematically show a manufacturing process of a general double-sided flexible wiring board. First, of the copper foils 102 and 103 of the double-sided flexible substrate 101 shown in FIG. 5 (a), a photosensitive dry film (DF) (not shown) serving as an etching resist is laminated on one copper foil 102, and exposure and development are performed. Then, through the etching process, the copper foil 102 in the blind via forming portions 102a and 102b is removed (FIG. 5B).

  Next, using a laser processing machine, laser light is irradiated using the remaining copper foil 102 as a mask, and the polyimide layer 104 (insulating substrate) is removed to form blind vias 104a and 104b (FIG. 5C). ). As the laser beam, a carbon dioxide gas laser or a YAG laser is generally used. In the case of a flexible copper-clad laminate (FCCL), it is often performed in a fixed state, similar to drilling.

  Next, desmear processing is performed. In the desmear process, it is immersed in a strong alkali heating solution such as potassium permanganate solution to remove the smudges of polyimide adhering to the copper foil surface during laser processing, and uniform copper plating is applied to the blind vias 104a and 104b. The surfaces of the copper foils 102 and 103 are cleaned for application.

  Next, in order to make the polyimide layer 104 on the inner walls of the blind vias 104a and 104b conductive, an electroless copper plating process is performed, and then the copper plating 105 having a thickness of about 15 μm is usually formed on the inner walls of the blind vias 104a and 104b and the copper foil 102. , 103, and the copper foils 102, 103 are connected for electrical connection (FIG. 5D). Recently, instead of the electroless copper plating process, a method of attaching carbon particles to the polyimide layer 104 and performing the electrolytic copper plating process using the carbon particles as a nucleus is also used.

  Next, circuit formation is performed by a subtractive method. First, the photosensitive dry film 106 used as an etching resist is laminated on both surfaces (FIG. 5E). Next, formation of a predetermined circuit pattern 107 is completed through an exposure / development and etching process (FIG. 5F).

  6 (a) to 6 (e) show an outline of a manufacturing process of a general multilayer flexible wiring board. First, cover lays 112a and 112b are provided on both sides of the double-sided flexible wiring board 111 to form the core substrate 113 (FIG. 6A). Next, an adhesive layer 114a, 114b is provided by temporarily fixing an interlayer adhesive or prepreg on the upper and lower surfaces of the core substrate 113. Here, the adhesive layers 114a and 114b are removed in advance from a portion to be the flexible portion 120 using a mold or the like. Next, the two single-sided flexible boards 115a and 115b are temporarily fixed on the adhesive layers 114a and 114b from above and below, and are laminated by pressurization and heat curing using a hot press (FIG. 6B).

  Next, through vias 116 are formed by drilling and blind vias 117a and 117b are formed by laser processing, copper plating 118 is applied by electroless copper plating and electrolytic copper plating, and single-sided flexible boards 115a and 115b are formed. Are electrically connected to the conductive layer of the core substrate 113 (FIG. 6C). Next, a photosensitive dry film 119 is laminated on the single-sided flexible substrates 115a and 115b (FIG. 6D). Next, a predetermined circuit pattern is formed through exposure / development and etching processes.

  Finally, in order to form the flexible portion 120 of the multilayer flexible wiring board, the outer layer is peeled off. In the outer layer peeling step, a part of the outer layer single-sided flexible boards 115a and 115b is removed by router processing or the like to form the flexible part 120 (FIG. 6E).

  As a method for forming through vias and blind vias used in the above-described double-sided flexible wiring board manufacturing process and multilayer flexible wiring board manufacturing process, a build-up method using photolithography using a photosensitive resin has been proposed. (For example, refer to Patent Document 1 and Patent Document 2).

JP 2005-26297 A JP 2000-91743 A

  However, in the conventional method for manufacturing a flexible wiring board, as described above, it is necessary to process each hole by using a laser processing machine for forming a blind via, so that a great cost (processing time) is required. Also, roll-to-roll continuous production of flexible wiring boards using laser processing machines has many problems in terms of transport methods and quality control, and its introduction has been delayed. Therefore, blind via formation requires a lot of processing time and is a process that is difficult to automate. Moreover, since the production amount of flexible wiring boards is increasing as described above, further improvement in productivity and reduction in manufacturing cost are desired.

  Furthermore, in the manufacturing process of the conventional multilayer flexible wiring board, in order to enable bending and bending, the outer layer substrate is removed in the final process to form the flexible portion. This outer layer substrate peeling process is a major obstacle in terms of cost and quality.

  The present invention has been made in view of the above points, and it is possible to simplify the manufacturing process, reduce the manufacturing cost, and provide a method for manufacturing a flexible wiring board that can be used for continuous production. The purpose is to provide.

  The method for producing a flexible wiring board of the present invention includes a conductive layer forming step of forming a first conductive layer having a through hole forming portion on one main surface of a resin layer containing an alkali-soluble resin composition, and the first conductive A through-hole forming step of forming a through-hole by dissolving and removing the resin layer at the through-hole forming portion through a layer, and a second conductive layer on the other main surface of the resin layer in which the through-hole is formed A blind via forming step of forming a blind via and a plating step of plating the blind via to electrically connect the first conductive layer and the second conductive layer. To do.

  The method for manufacturing a flexible wiring board of the present invention is a method for manufacturing a flexible wiring board in which a core substrate made of any one of a single-sided flexible wiring board, a double-sided flexible wiring board, and a multilayer flexible wiring board and an outer layer substrate are laminated. An external conductive layer forming step of forming an external conductive layer having a through hole forming site on one main surface of the resin layer containing the alkali-soluble resin composition, and forming the through hole via the external conductive layer A step of forming a through hole in the outer layer substrate by dissolving and removing the resin layer of the portion; and the outer layer substrate so that the through hole of the outer layer substrate matches a predetermined portion of the core substrate. Blind via forming step of laminating the core substrate to form a blind via, and plating the blind via to form an inner conductive layer and an outer layer base of the core substrate Characterized by comprising the outer conductive layer and a plating step of electrically connecting.

  In the method for manufacturing a flexible wiring board of the present invention, in the external conductive layer forming step, the external conductive layer in the flexible portion forming portion is removed, and in the through hole forming step, the resin layer in the flexible portion forming portion is removed. It is preferable to form a flexible part by dissolving and removing.

  In the manufacturing method of the flexible wiring board of this invention, it is preferable that the said alkali-soluble resin composition contains the polyimide precursor which has a polyamic acid structure at least.

  In the manufacturing method of the flexible wiring board of this invention, it is preferable that the said polyimide precursor contains the block copolymer which has a polyamic-acid structure and a polyimide structure as a structural unit, respectively.

  In the manufacturing method of the flexible wiring board of this invention, it is preferable that the said polyimide precursor has a polyalkylene ether structure and / or a siloxane structure.

  In the method for producing a flexible wiring board of the present invention, it is preferable that the alkali-soluble resin composition further contains a dissolution inhibitor.

  In the method for producing a flexible wiring board of the present invention, the dissolution inhibitor is preferably an amide compound or a urea compound.

  In the manufacturing method of the flexible wiring board of this invention, it is preferable that the said alkali-soluble resin composition contains a phosphorus compound further.

  In the manufacturing method of the flexible wiring board of this invention, it is preferable that the said phosphorus compound is a phosphate ester compound and / or a phosphazene compound.

  In the method for producing a flexible wiring board of the present invention, the resin layer is a sodium hydroxide of a resin layer having a film thickness of 25 μm obtained after coating an alkali-soluble resin composition on a conductive film substrate and removing the solvent by heating. The dissolution rate in an aqueous solution is 0.50 μm / sec or more, the dissolution rate in a sodium hydroxide aqueous solution obtained by heating the resin layer at 160 ° C. or more is 0.05 μm / sec or less, and the resin The elastic modulus of the layer is preferably 0.2 GPa to 1.5 GPa, and the glass transition temperature of the resin layer is preferably 150 ° C. or lower.

  The flexible wiring board of the present invention is manufactured by the above-described method for manufacturing a flexible wiring board.

  According to the present invention, a manufacturing method of a double-sided flexible wiring board and a manufacturing method of a multilayer flexible wiring board that can simplify the manufacturing process, reduce the manufacturing cost, and can cope with continuous production are provided. can do.

It is a figure which shows the outline of the manufacturing process of the double-sided flexible wiring board which concerns on embodiment of this invention. It is a figure which shows the outline of the manufacturing process of the core board | substrate used for the multilayer flexible wiring board which concerns on embodiment of this invention. It is a figure which shows the outline of the manufacturing process of the multilayer flexible wiring board which concerns on embodiment of this invention. It is a figure which shows the outline of the manufacturing process of the multilayer flexible wiring board which has a flexible part which concerns on embodiment of this invention. It is a figure which shows the outline of the manufacturing process of a general double-sided flexible wiring board. It is a figure which shows the outline of the manufacturing process of a general multilayer flexible wiring board.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the method for manufacturing a flexible wiring board according to one embodiment of the present invention, a single-sided flexible board comprising a resin layer containing an alkali-soluble resin composition as an adhesive layer and a conductive layer provided on the resin layer To manufacture a flexible wiring board. In the present embodiment, by using a resin layer containing an alkali-soluble resin composition, it is possible to dissolve and remove the resin layer without performing laser processing and drilling, so that a through hole can be formed. Can be simplified and the manufacturing cost can be reduced. Hereinafter, the manufacturing process of the double-sided flexible wiring board and the manufacturing process of the multilayer flexible wiring board using the manufacturing method of the flexible wiring board according to the present embodiment will be described.

(Manufacturing process of double-sided flexible wiring board)
FIG. 1A to FIG. 1F schematically show the manufacturing process of the double-sided flexible wiring board according to the embodiment of the present invention. For manufacturing a double-sided flexible wiring board, a single-sided flexible wiring board 13 including a resin layer 11 containing an alkali-soluble resin composition and a copper foil 12 provided on one main surface of the resin layer 11 is used. (FIG. 1 (a)).

  First, a photosensitive dry film (not shown) is laminated on the copper foil 12, and the dry films of the blind via forming portions 12a to 12c (through hole forming portions) are removed by exposure and development. Next, the copper foil 12 in the blind via forming portions 12a to 12c is removed by etching to form a conformal mask 14 (FIG. 1B). Next, the resin layers 11 of the blind via forming portions 12a to 12c are dissolved and removed with an alkaline solution to form the through holes 15a to 15c (FIG. 1C). The alkali solution is not particularly limited as long as it can dissolve the alkali-soluble resin composition used as the resin layer 11, and an aqueous sodium carbonate solution, an aqueous sodium hydroxide solution, and an aqueous potassium hydroxide solution can be used. Moreover, the alkali spray apparatus etc. which are used by the manufacturing process of the general flexible wiring board can be used for melt | dissolution removal of the resin layer by an alkali liquid.

  Next, the blind vias 17a to 17c are formed by bonding the copper foil 16 from the other main surface side of the resin layer 11 provided with the through holes 15a to 15c (FIG. 1D). Next, the inner walls of the blind vias 17a to 17c and the surface of the copper foil 12 are subjected to electroless copper plating to make the resin layer 11 in the blind vias 17a to 17c conductive. Next, copper plating 18 is applied to the inner walls of the blind vias 17a to 17c and the surface of the copper foil 12 to connect the copper foil 12 and the copper foil 16 to electrical connection (FIG. 1 (e)).

  Next, a photosensitive dry film (not shown) is laminated on a predetermined portion of the copper plating 18, and the photosensitive dry film is patterned by exposure and development. Next, the copper foil 12 is removed by etching to form a circuit pattern 19 (FIG. 1 (f)). The double-sided flexible wiring board 20 is manufactured by the above process.

(Manufacturing process of multilayer flexible wiring board)
Next, the manufacturing process of a multilayer flexible wiring board is demonstrated. The multilayer flexible wiring board is manufactured by bonding a core substrate manufactured using a double-sided flexible wiring board and an outer layer substrate manufactured using a single-sided flexible substrate.

  2A to 2E show an outline of the manufacturing process of the core substrate 29 used for the multilayer flexible wiring board. The core substrate 29 includes a resin layer 21 containing an alkali-soluble resin composition, a copper foil 22 provided on one main surface of the resin layer 21, and a copper foil 23 provided on the other main surface. It manufactures using the double-sided flexible wiring board 24 (Fig.2 (a)). The core substrate can also be manufactured using various flexible wiring boards such as a single-sided flexible wiring board, a double-sided flexible wiring board, or a multilayer flexible wiring board.

  First, a dry film (not shown) is laminated on the copper foil 22, and the dry film of the blind via forming portion 21a (through hole forming portion) is removed by exposure and development. Next, the copper foils 22 and 23 are removed by etching to form a conformal mask. Next, the resin layer 21 at a position corresponding to the blind via forming portion 21a is dissolved and removed with an alkaline solution to form a through hole 25, and the dry film is removed (FIG. 2B). The alkali liquid is not particularly limited as long as it can dissolve the alkali-soluble resin composition used as the resin layer 21.

  Next, the inner wall of the through hole 25 and the surfaces of the copper foils 22 and 23 are subjected to electroless copper plating to make the resin layer 21 in the through hole 25 conductive. Next, copper plating 26 is applied to the inner wall of the through hole 25 and the surfaces of the copper foils 22 and 23 to connect the copper foil 22 and the copper foil 23 to electrical connection (FIG. 2C).

  Next, a photosensitive dry film 27 is laminated on a predetermined portion of the copper plating 26, and the photosensitive dry film 27 is patterned by exposure and development (FIG. 2D). Next, the copper foils 22 and 23 are patterned by etching to form a circuit pattern 28. The core substrate 29 is manufactured through the above steps (FIG. 2E).

  3A to 3E show an outline of the manufacturing process of the multilayer flexible wiring board. First, outer layer substrates 33 and 34 are manufactured using two single-sided flexible wiring boards in which a copper foil 30 and a resin layer 31 as an adhesive layer containing an alkali-soluble resin composition are laminated. First, a photosensitive dry film (not shown) is laminated on the copper foil 30, and the blind via forming portions 30a to 30d (through hole forming portions) are removed by exposure and development. Next, the copper foils 30 of the blind via forming portions 30a to 30d are removed by etching, and the resin layer 31 is dissolved and removed with an alkaline solution to form the through holes 32a to 32d, thereby manufacturing the outer layer substrates 33 and 34 (FIG. 3). (A)).

  Next, the outer substrate 33 is bonded so that the circuit pattern 28 on one main surface side of the core substrate 29 and the resin layer 31 face each other, and the circuit pattern 28 on the other main surface side and the resin layer 31 face each other. In this manner, the outer substrate 34 is bonded (FIG. 3B). Here, blind vias 35 a to 35 d are formed by the through holes 32 a to 32 d of the outer layer substrates 33 and 34. The circuit pattern 28 of the core substrate 29 becomes the inner conductive layer 36, and the copper foil 30 of the outer layer substrate 33 and the copper foil 30 of the outer layer substrate 34 become the outer conductive layer 37.

  Next, electroless copper plating is performed on the surface of the external conductive layer 37 and the inner walls of the blind vias 35a to 35d to make the resin layer 31 in the blind vias 35a to 35d conductive. Next, copper plating 38 is applied to the inner walls of the blind vias 35a to 35d and the surface of the external conductive layer 37 to electrically connect the internal conductive layer 36 and the external conductive layer 37 (FIG. 3C).

  Next, a photosensitive dry film 39 is laminated on a predetermined portion of the copper plating 38 and patterned by exposure and development (FIG. 3D). Next, the external conductive layer 37 is patterned by etching to form a circuit pattern 40, and the photosensitive dry film 39 is removed to manufacture the multilayer flexible wiring board 41 (FIG. 3E).

  Next, the manufacturing method of the multilayer flexible wiring board which has a flexible part is demonstrated. The outline of the manufacturing process of the multilayer flexible wiring board which has a flexible part in Fig.4 (a)-FIG.4 (e) is shown. In the following description, differences from the above-described multilayer flexible wiring board manufacturing method will be mainly described to avoid duplication of description.

  First, a dry film (not shown) is laminated on the copper foil 50, and the blind via forming part (through hole forming part) and the copper foil 50 in the flexible part 50a are removed by exposure and development. Next, the resin layer 51 containing the alkali-soluble resin composition is dissolved and removed with an alkali solution to form the through holes 52a to 52d at the blind via formation sites, and the resin layer 51 of the flexible portion 50a is removed. The outer layer substrates 53 and 54 are manufactured as described above (FIG. 4A).

  Next, the outer substrate 53 is bonded so that the circuit pattern 28 on one main surface side of the core substrate 29 and the resin layer 51 face each other, and the circuit pattern 28 on the other main surface side and the resin layer 51 face each other. In this manner, the outer substrate 54 is bonded (FIG. 4B). Here, blind vias 55a to 55d are formed by the through holes 52a to 52d provided in the outer layer substrates 53 and 54, respectively. The circuit pattern 28 of the core substrate 29 becomes the inner conductive layer 56, and the copper foil 50 of the outer layer substrate 53 and the copper foil 50 of the outer layer substrate 54 become the outer conductive layer 57.

  Next, an electroless copper plating process is performed on the surface of the external conductive layer 57 and the inner walls of the blind vias 55a to 55d to make the resin layer 51 in the blind vias 55a to 55d conductive. Next, copper plating 58 is applied to the inner walls of the blind vias 55a to 55d and the surface of the external conductive layer 57 to electrically connect the internal conductive layer 56 and the external conductive layer 57 (FIG. 4C).

  Next, a photosensitive dry film 59 is laminated on a predetermined portion of the copper plating 58, and the photosensitive dry film 59 is patterned by exposure and development (FIG. 4D). Next, the external conductive layer 57 is patterned by etching to form a circuit pattern 60. Finally, by removing the photosensitive dry film 59, the multilayer flexible wiring board 61 is manufactured (FIG. 4E).

  According to the embodiment described above, the resin layer can be dissolved and removed by the alkali solution by using the resin layer containing the alkali-soluble resin composition. For this reason, a blind via can be easily formed without requiring laser processing or drilling. Further, since no foreign matter (smear) is generated on the surface of the copper foil, desmear processing or the like is not required. Therefore, the cost of forming blind vias can be greatly reduced, roll-to-roll production can be facilitated, and double-sided flexible wiring boards and multilayer flexible wiring boards that can greatly reduce production lead time can be produced.

  Further, in the above-described embodiment, as an interlayer adhesive having a function of an interlayer insulator of a double-sided flexible wiring board or a multilayer flexible wiring board, an alkali imparted again with adhesiveness after heat curing instead of a conventional thermosetting adhesive. A soluble resin composition can be used. For this reason, it is possible to use an etching apparatus, an alkaline liquid spray apparatus, a laminating equipment, etc. that are generally used in the manufacturing process of a flexible printed wiring board without using laser processing to form a blind via for interlayer connection. It becomes possible. Moreover, it can be applied not only to the formation of blind vias on double-sided flexible wiring boards but also to the formation of blind vias on multilayer flexible wiring boards.

  Moreover, according to the said embodiment, it becomes possible to comprise a multilayer flexible wiring board, without providing a coverlay between a core board | substrate and an outer layer board | substrate. For this reason, it is possible to simplify the configuration as compared with the multilayer flexible wiring board manufactured by the conventional multilayer flexible wiring board manufacturing method, and it is possible to greatly simplify the manufacturing process.

  Furthermore, according to the above embodiment, in the manufacturing process of the multilayer flexible wiring board, it is possible to form the flexible part by removing the outer layer board as well as forming the blind via. For this reason, the blind via forming technology is applied to the outer layer substrate peeling process of the multilayer flexible wiring board, and simultaneously with the blind via forming process, the copper foil etching of the outer layer removing portion and the alkali-soluble resin composition as the insulating layer are dissolved and removed. As a result, the outer layer substrate can be easily peeled off to form the flexible portion.

(Alkali-soluble resin composition)
Next, the alkali-soluble resin composition used in the method for producing a flexible wiring board according to the present embodiment will be described. The alkali-soluble resin composition is used for forming a resin layer as an adhesive that forms an interlayer insulating layer of a flexible wiring board. The alkali-soluble resin composition is not limited as long as it contains at least an alkali-soluble resin. The alkali-soluble resin is not particularly limited as long as it is dissolved by a dissolution treatment with an alkaline solution after the conformal mask is formed.

  The resin layer preferably has a low elastic modulus in order to impart flexibility at the flexible portion of the flexible wiring board or to enable molding by a roll-to-roll method. The resin layer having a film thickness of 25 μm obtained after coating on the conductive film substrate of the resin layer and desolvation by heating has a dissolution rate in a sodium hydroxide aqueous solution of 0.50 μm / sec or more. The dissolution rate in an aqueous sodium hydroxide solution obtained by heating at a temperature of not less than 0.05 ° C. is 0.05 μm / sec or less, the elastic modulus of the resin layer is 0.2 GPa to 1.5 GPa, and the glass transition temperature is 150 ° C. or less. Preferably there is. When the alkali dissolution rate of the resin layer is within the above range, the alkali solubility of the resin layer can be easily controlled, and an alkaline liquid spray device generally used in the flexible printed wiring board manufacturing process can be used. Moreover, if the elasticity modulus of a resin layer is 0.2 GPa-1.5 GPa, the curvature of a board | substrate is small and it is excellent in a softness | flexibility. A glass transition temperature of 150 ° C. or lower, preferably 50 ° C. to 120 ° C., is preferable because lamination using a general laminating apparatus can be performed.

  For the resin layer, the alkali-soluble resin composition may be applied to the conductive substrate film, or may be laminated on the conductive substrate after being once formed on the film. By heating the obtained resin layer as needed, an adhesive resin layer is formed.

  Examples of the alkali-soluble resin include novolak resins, acrylic resins, copolymers of styrene and acrylic acid, polymers of hydroxystyrene, polyvinylphenol, poly α-methylvinylphenol, polyimide resins, polybenzoxazole resins, and the like. Can be mentioned.

  The alkali-soluble resin is preferably a resin having a carboxyl group in the molecular chain in order to have alkali solubility. Furthermore, from the viewpoint of heat resistance and flexibility of the resin layer obtained after heating at 200 ° C. or lower, a polyimide having a carboxyl group in the molecule (hereinafter referred to as a carboxyl group-containing one having a carboxyl group in the molecule), a polyimide precursor Body, carboxyl group-containing polybenzoxazole, and carboxyl group-containing polybenzoxazole precursor are preferred. A polyamic acid represented by the following general formula (1) and a polymer having a polyamic acid ester structure having a carboxyl group in the molecule (hereinafter, containing a carboxyl group) are more preferable.

  In this embodiment, by using a polyimide precursor, a polyamic acid represented by the following general formula (1), and a carboxyl group-containing polymer having a polyamic acid ester structure, it is relatively weak used in a normal production line. The resin layer can be dissolved with a basic aqueous solution, and a flexible wiring board having excellent circuit board quality can be obtained.

（式（１）中、Ｒ_１は４価の有機基である。Ｒ_２、Ｒ_３は水素又は炭素数１〜炭素数２０の有機基であり、それぞれ同一でも異なっていてもよい。Ｒ_４は２価〜４価の有機基である。Ｒ_５、Ｒ_６は水素又は炭素数１〜炭素数２０の有機基であり、それぞれ同一でも異なっていてもよい。ただし、Ｒ_２及びＲ_３が水素でないとき、ｍ＋ｎ＞０かつｎ＞０であり、Ｒ_５は水素又は炭素数１〜炭素数２０の有機基、Ｒ_６は水素である。Ｒ_２、Ｒ_３の少なくとも一方が水素のときｍ＋ｎ≧０であり、かつＲ_５、Ｒ_６は水素又は炭素数１〜炭素数２０の有機基であって、それぞれ同一でも異なっていてもよい。）

(In Formula (1), R ₁ is a tetravalent organic group. R ₂ and R ₃ are hydrogen or an organic group having 1 to 20 carbon atoms, and may be the same or different. R ₄ Is a divalent to tetravalent organic group, R ₅ and R ₆ are hydrogen or an organic group having 1 to 20 carbon atoms, which may be the same or different, provided that R ₂ and R ₃ are When not hydrogen, m + n> 0 and n> 0, R ₅ is hydrogen or an organic group having 1 to 20 carbon atoms, R ₆ is hydrogen, m + n when at least one of R ₂ and R ₃ is hydrogen ≧ 0, and R ₅ and R ₆ are hydrogen or an organic group having 1 to 20 carbon atoms, which may be the same or different.

  As the alkali-soluble resin, a polyamic acid represented by the following general formula (2) is more preferable.

（式（２）中、Ｒ_７は炭素数２以上である４価の有機基を示し、Ｒ_８は炭素数２以上の２価の有機基を示す。）

(In Formula (2), R ₇ represents a tetravalent organic group having 2 or more carbon atoms, and R ₈ represents a divalent organic group having 2 or more carbon atoms.)

  The polyimide precursor is preferably produced by polymerizing tetracarboxylic dianhydride and diamine. Examples of the tetracarboxylic dianhydride and diamine used include those shown below.

  Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetra. Carboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3 '-Benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1, 1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride , Screw (2, -Dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,3'-oxydiphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, 2,2 -Bis (4- (4-aminophenoxy) phenyl) propane, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester, 4- (2,5-dioxo Tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7 -Naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,2-bis 3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 2,2-bis (4- (3,4-dicarboxyphenoxy) phenyl) hexafluoropropane dianhydride, 2,2-bis (4- ( 3,4-dicarboxybenzoyloxy) phenyl) hexafluoropropane dianhydride, 2,2′-bis (trifluoromethyl) -4,4′-bis (3,4-dicarboxyphenoxy) biphenyl dianhydride, etc. Can be mentioned.

  Examples of the aliphatic tetracarboxylic dianhydride include cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, and 2,3,5,6-cyclohexanetetracarboxylic acid. Dianhydride, 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1,2-dicarboxylicsan dianhydride, ethylene glycol-bis-trimellitic anhydride ester, bicyclo [2,2,2] Oct-7-ene-2,3,5,6 tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more.

  Among these tetracarboxylic dianhydrides, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid dianiline is used from the viewpoint of increasing the flexibility of the insulating layer formed through the heat treatment. Anhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone Tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2 , 3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane anhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane anhydride, bis (3 , 4-Di Ruboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfon dianhydride, 3,3′-oxydiphthalic dianhydride, 4,4 '-Oxydiphthalic acid dianhydride, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene Preferred are esters, ethylene glycol-bis-trimellitic anhydride esters. These may be used alone or in combination of two or more.

  Examples of the diamine include 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and 3,4′-diaminodiphenyl ether. 3,3′-dimethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl 3,7-diamino-dimethylbenzothiophene-5,5-dioxide, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis (4-aminophenyl) sulfide, 4,4 '-Diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 1, n-bis (4-aminopheno B) Alkane, 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane, 9,9-bis (4-amino) Phenyl) fluorene, 5 (6) -amino-1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4- Aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2- Bis (4-aminophenoxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2, -Bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 4,6-dihydroxy-1,3-phenylenediamine, 3,3 ' -Dihydroxy-4,4'-diaminobiphenyl, 1,4-bis (4-aminophenoxy) pentane, 1,5-bis (4'-aminophenoxy) pentane, bis (γ-aminopropyl) tetramethyldisiloxane, 1,4-bis (γ-aminopropyldimethylsilyl) benzene, bis (4-aminobutyl) tetramethyldisiloxane, bis (γ-aminopropyl) tetraphenyldisiloxane, diamino represented by the following general formula (3) Examples thereof include siloxane compounds. These may be used alone or in combination of two or more.

In the general formula (3), R ₉ and R ₁₀ represent an organic group having 1 to 30 carbon atoms, and may be the same or different. Examples of the organic group (R ₉ ) having 1 to 30 carbon atoms include an aliphatic saturated hydrocarbon group, an aliphatic unsaturated hydrocarbon group, a functional group including a cyclic structure, and a group obtained by combining them. .

  Examples of the aliphatic saturated hydrocarbon group include primary hydrocarbon groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, and hexyl group, secondary hydrocarbon groups such as isobutyl group and isopentyl group, and tertiary hydrocarbon groups such as t-butyl group.

  Examples of the aliphatic unsaturated hydrocarbon group include a hydrocarbon group containing a double bond such as a vinyl group and an allyl group, and a hydrocarbon group containing a triple bond such as an ethynyl group.

  Examples of the functional group containing a cyclic structure include a monocyclic functional group such as a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclodecyl group, and a cyclooctyl group; a polycyclic functional group such as a norbornyl group and an adamantyl group; pyrrole, furan, A heterocyclic functional group having a thiophene, imidazole, oxazole, thiazole, tetrahydrofuran, dioxane structure; an aromatic hydrocarbon group containing a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring structure.

The organic group (R ₉ ) having 1 to 30 carbon atoms may contain a halogen atom, a hetero atom, and a metal atom. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Moreover, oxygen, sulfur, nitrogen, and phosphorus are mentioned as a hetero atom. Examples of the metal atom include silicon and titanium.

In addition, when the organic group (R ₉ ) having 1 to 30 carbon atoms includes a hetero atom and / or a metal atom, the organic group (R ₉ ) is directly bonded to the bonded hetero atom and / or metal atom. Alternatively, they may be bonded via a hetero atom and / or a metal atom.

  Examples of the compound represented by the general formula (3) include silicone diamine (manufactured by Shin-Etsu Chemical Co., Ltd., PAM-E, KF-8010, X-22-161A, X-22-1660B-3).

The carbon number of R ₉ is preferably 1 or more and 20 or less in consideration of flame retardancy. Furthermore, from the viewpoint of solvent solubility of the polyimide to be produced, the carbon number of R ₉ is particularly preferably 1 or more and 10 or less.

  Moreover, it is also preferable to use the diamine which has chain | strand-shaped polyether in a molecular structure as a diamine, and it is preferable to use the compound represented by the following general formula (4) or the following general formula (5).

（式（４）中、ｂは１〜５０の整数を表し、Ｒ_１１はそれぞれ独立に炭素数２〜炭素数１０のアルキレン基を表す。)

(In formula (4), b represents an integer of 1 to 50, and R ₁₁ independently represents an alkylene group having 2 to 10 carbon atoms.)

（式（５）中、Ｒ_１２、Ｒ_１３、Ｒ_１４、Ｒ_１５、Ｒ_１６はそれぞれ独立して炭素数１〜炭素数２０のアルキレン基を表し、それぞれ独立して炭素数１〜炭素数５のアルキル基を１個以上、有していても良い。ｃ、ｄ、ｅはそれぞれ独立して０以上の整数を表す。）

(In Formula (5), R < ₁₂ >, R <_13> , R <_14> , R <_15> , R < ₁₆ > each independently represents an alkylene group having 1 to 20 carbon atoms, and each independently represents 1 to 5 carbon atoms. And may have one or more alkyl groups, and c, d and e each independently represents an integer of 0 or more.)

  Examples of the diamine represented by the general formula (4) include polytetramethylene oxide-di-o-aminobenzoate, polytetramethylene oxide-di-m-aminobenzoate, polytetramethylene oxide-di-p-amino. Examples include, but are not limited to, benzoate, polytrimethylene oxide-di-o-aminobenzoate, polytrimethylene oxide-di-m-aminobenzoate, polytrimethylene oxide-di-p-aminobenzoate. Among them, those having both ends at the p-aminobenzoic acid ester group are preferable, and among them, polytetramethylene oxide-di-p-aminobenzoate is preferably used. Two or more diamines may be used.

  The diamine represented by the general formula (4) contains 25 to 55 mol% of the diamine represented by the general formula (4) with respect to the total diamine. Preferably they are 25 mol%-50 mol%, More preferably, they are 30 mol%-50 mol%. If it is 25 mol% or more, flexibility is shown, and if it is 55 mol% or less, it is excellent in solvent resistance and heat resistance.

  Examples of the diamine represented by the general formula (5) include polyoxyethylene diamine such as 1,8-diamino-3,6-dioxyoctane, polyoxypropylene diamine, and other oxyalkylene groups having different lengths. And polyoxyalkylene diamines such as those containing As polyoxyalkylene diamines, polyoxyethylene diamines such as Jeffamine EDR-148 and EDR-176 by Huntsman, Inc., polyoxypropylene diamines such as Jeffamine D-230, D-400, D-2000 and D-4000, Commercial products such as those having different oxyalkylene groups such as HK-511, ED-600, ED-900, ED-2003, XTJ-542 are listed as examples of use. In particular, EDR-148, D-230, D-400, HK-511, etc., which have relatively low molecular weights, can be polymers having a relatively high glass transition temperature, and therefore are used in applications that require heat resistance and chemical resistance. can do. On the other hand, D-2000 having a relatively high molecular weight is excellent in flexibility, low boiling point solvent solubility and the like. In addition, it is easier to obtain a high molecular weight polyamic acid when the one having high purity is used, preferably 95% or more, more preferably 97% or more, and further preferably 98.5% or more.

  It is preferable that the diamine represented by the said General formula (5) is 25 mol%-60 mol% with respect to all the diamines. More preferably, it is 25 mol%-50 mol%, More preferably, it is 30 mol%-50 mol%. If it is 25 mol% or more, flexibility is shown, and if it is 60 mol% or less, it is excellent in solvent resistance and heat resistance.

  Among these diamines, 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 4,4′-diamino are used from the viewpoint of enhancing the flexibility of the insulating layer formed through the heat treatment. Diphenylmethane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-dianobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 3, , 7-diamino-dimethylbenzothiophene-5,5-dioxide, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis (4-aminophenyl) sulfide, 4,4′- Diaminodiphenylsulfone, 4,4′-diaminobenzanilide, 1, n-bis (4-aminophenoxy) alkane, 1 3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane, 9,9-bis (4-aminophenyl) fluorene, 5 ( 6) -Amino-1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, , 3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2-bis (4-aminophenoxy) Phenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 4,6-dihydroxy- , 3-phenylenediamine, 3,3′-dihydroxy-4,4′-diaminobiphenyl, 1,4-bis (4-aminophenoxy) pentane, 1,5-bis (4′-aminophenoxy) pentane, bis ( γ-aminopropyl) tetramethyldisiloxane, 1,4-bis (γ-aminopropyldimethylsilyl) benzene, bis (4-aminobutyl) tetramethyldisiloxane, bis (γ-aminopropyl) tetraphenyldisiloxane, the above The diaminosiloxane compound represented by the general formula (3), the general formula (4) having a chain polyether in the molecular structure, or the compound represented by the general formula (5) is preferable. These may be used alone or in combination of two or more.

  In addition to the polyamic acid structure, the polyimide precursor preferably has a polyimide structure. The imidation ratio is preferably in the range of 0% to 99.9%, more preferably in the range of 0% to 90%, and still more preferably in the range of 0% to 80%.

  Next, a method for producing a polyimide precursor will be described. The polyimide precursor can be easily synthesized by a known method described in the latest polyimide, basics and applications, edited by Japan Polyimide Research Group, pp4 to pp49. Specifically, a method of reacting a tetracarboxylic dianhydride and a diamine at a low temperature to 100 ° C. or lower, a tetracarboxylic dianhydride and an alcohol are reacted to synthesize a diester, and then a diamine in the presence of a condensing agent. And a method of reacting tetracarboxylic dianhydride with an alcohol to synthesize a diester, and then converting the remaining dicarboxylic acid into an acid chloride and then reacting with a diamine. A method in which tetracarboxylic dianhydride and diamine are reacted at a low temperature to 100 ° C. or less is preferred.

  The reaction is preferably performed in an organic solvent. As a solvent used in such a reaction, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 1,3 -Dioxane, 1,4-dioxane, dimethyl sulfoxide, benzene, toluene, xylene, mesitylene, phenol, cresol and the like. These may be used alone or in combination of two or more.

The density | concentration of the reaction raw material in this reaction is 2 mass%-60 mass% normally, Preferably it is 5 mass%-50 mass%, More preferably, it is 10 mass%-45 mass%.

  The molar ratio of the acid dianhydride to be polymerized and the diamine is in the range of 0.8 to 1.2. Within this range, the molecular weight can be increased, and the elongation and the like are excellent. Preferably it is 0.9-1.1, More preferably, it is 0.95-1.05.

  The weight average molecular weight of the polyimide precursor is preferably 5000 or more and 100,000 or less. Here, the weight average molecular weight refers to a molecular weight measured by gel permeation chromatography using polystyrene having a known number average molecular weight as a standard. The weight average molecular weight is more preferably from 10,000 to 60,000, and most preferably from 20,000 to 50,000. When the weight average molecular weight is 5,000 or more and 100,000 or less, the warp of the insulating layer obtained using the resin composition is improved, and the flexibility and heat resistance are excellent.

  In order to introduce an imide structure, the polyimide precursor obtained above is preferably heated to 100 ° C. to 400 ° C. to imidize, or chemically imidized using an imidizing agent such as acetic anhydride. A polyimide having a repeating unit structure corresponding to the polyamic acid structure is obtained. In the case of imidization by heating, in order to remove by-product water, dehydration is carried out under reflux using a Dean-Stark type dehydrator in the presence of an azeotropic agent (preferably toluene or xylene). Is also preferable.

Moreover, it is also preferable to obtain a polyimide by carrying out the reaction at 80 ° C. to 220 ° C. to advance both the generation of the polyimide precursor and the thermal imidization reaction. That is, the diamine component and the acid dianhydride component are suspended or dissolved in an organic solvent and reacted under heating at 80 ° C. to 220 ° C. to cause both generation of a polyimide precursor and dehydration imidization. It is also preferable to obtain polyimide.

  The polyimide precursor is preferably a block copolymer having a polyamic acid structure and a polyimide structure as structural units, respectively, from the viewpoint of controlling alkali solubility.

  A polyimide precursor having a polyimide structure and a polyamic acid structure as repeating units, respectively, is a step of synthesizing a first stage polyamic acid by reacting acid dianhydride and diamine in an unequal molar amount (step 1), followed by imide It can be produced by the step (Step 2) to synthesize, and then the step (Step 3) for synthesizing the second stage polyamic acid.

  Furthermore, as a polyamic acid-polyimide block body, any of the diamine having a chain siloxane structure represented by the above general formula (3) in the molecular structure in the polyimide block, the above general formula (4), and the above general formula (5) It is preferable to introduce a diamine having a chain polyether represented by the formula: By converting the terminal of these diamines into an imide structure, the storage stability of the alkali-soluble resin composition can be improved. Hereinafter, each process will be described.

(Process 1)
The process of synthesizing the first stage polyamic acid will be described. The step of synthesizing the first stage polyamic acid is not particularly limited, and a known method can be applied. More specifically, it is obtained by the following method. First, diamine is dissolved and / or dispersed in a polymerization reaction solvent, acid dianhydride powder is added thereto, and the mixture is stirred for 0.5 hours to 96 hours, preferably 0.5 hours to 30 hours using a mechanical stirrer. In this case, the monomer concentration is 0.5% by mass or more and 95% by mass or less, preferably 1% by mass or more and 90% by mass or less. By performing polymerization in this monomer concentration range, a polyamic acid solution can be obtained.

  Examples of the reaction solvent used in the production of the polyamic acid include dimethyl ether, diethyl ether, methyl ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether. Ether compounds of: ketone compounds having 2 to 6 carbon atoms such as acetone and methyl ethyl ketone; saturated compounds having 5 to 10 carbon atoms such as normal pentane, cyclopentane, normal hexane, cyclohexane, methylcyclohexane and decalin Hydrocarbon compounds; aromatic hydrocarbon compounds having 6 to 10 carbon atoms such as benzene, toluene, xylene, mesitylene, tetralin; methyl acetate, ethyl acetate ester compounds having 3 to 9 carbon atoms such as γ-butyrolactone and methyl benzoate; halogen-containing compounds having 1 to 10 carbon atoms such as chloroform, methylene chloride and 1,2-dichloroethane; acetonitrile, Nitrogen-containing compounds having 2 to 10 carbon atoms such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone; and sulfur-containing compounds such as dimethyl sulfoxide. These may be one kind or a mixture of two or more kinds as necessary. Particularly preferable solvents include ether compounds having 2 to 9 carbon atoms, ester compounds having 3 to 9 carbon atoms, aromatic hydrocarbon compounds having 6 to 10 carbon atoms, and 2 to carbon atoms. A nitrogen-containing compound of several tens or less is mentioned. These can be arbitrarily selected in consideration of industrial productivity and influence on the next reaction.

  The reaction temperature for producing the first stage polyamic acid is preferably 100 ° C. or higher and 250 ° C. or lower from the viewpoint of the reactivity of the silicone diamine. If it is 100 degreeC or more, reaction will be started, and if it is 250 degrees C or less, there will be no influence of a side reaction. Preferably they are 120 degreeC or more and 220 degrees C or less, More preferably, they are 120 degreeC or more and 200 degrees C or less. The time required for the reaction of the polyamic acid varies depending on the purpose or reaction conditions, but is usually within 96 hours, particularly preferably 30 to 30 hours.

(Process 2)
Next, a method for imidizing polyamic acid will be described. When manufacturing the polyimide site | part which concerns on this invention, it can obtain even by adding a well-known imidation catalyst or without a catalyst. The imidization catalyst in the present invention is not particularly limited, but an acid anhydride such as acetic anhydride, γ-valerolactone, γ-butyrolactone, γ-tetronic acid, γ-phthalide, γ-coumarin, and γ-phthalido acid. Examples include lactone compounds, pyridine, quinoline, N-methylmorpholine, tertiary amines such as triethylamine, and the like. Moreover, 1 type or 2 or more types of mixtures may be sufficient as needed. Among these, a mixed system of γ-valerolactone and pyridine and a non-catalyst are particularly preferable from the viewpoint of high reactivity and influence on the next reaction.

  The amount of the imidization catalyst added is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, based on 100 parts by mass of the polyamic acid. As the reaction solvent, the same solvent as used for the production of polyamic acid can be used. In that case, the polyamic acid solution can be used as it is. Moreover, you may use the solvent different from what was used for manufacture of a polyamic acid.

  Examples of such solvents include ether compounds having 2 to 9 carbon atoms such as dimethyl ether, diethyl ether, methyl ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; acetone, methyl ethyl ketone, and the like. A ketone compound having 2 to 6 carbon atoms; a saturated hydrocarbon compound having 5 to 10 carbon atoms, such as normal pentane, cyclopentane, normal hexane, cyclohexane, methylcyclohexane, decalin; benzene, toluene, xylene Aromatic hydrocarbon compounds having 6 to 10 carbon atoms such as mesitylene and tetralin; methyl acetate, ethyl acetate, γ-butyrolactone, benzoic acid Ester compounds having 3 to 9 carbon atoms such as chill; halogen-containing compounds having 1 to 10 carbon atoms such as chloroform, methylene chloride and 1,2-dichloroethane; acetonitrile, N, N-dimethylformamide N, N-dimethylacetamide, N-methyl-2-pyrrolidone and other nitrogen-containing compounds having 2 to 10 carbon atoms; sulfur-containing compounds such as dimethyl sulfoxide.

  These may be one kind or a mixture of two or more kinds as necessary. Particularly preferable solvents include ether compounds having 2 to 9 carbon atoms, ester compounds having 3 to 9 carbon atoms, aromatic hydrocarbon compounds having 6 to 10 carbon atoms, and 2 to carbon atoms. A nitrogen-containing compound of several tens or less is mentioned. These can be arbitrarily selected in consideration of industrial productivity and influence on the next reaction.

  In the production of the polyimide according to the present invention, the reaction temperature is preferably 15 ° C. or more and 250 ° C. or less. If it is 15 degreeC or more, reaction will be started, and if it is 250 degrees C or less, there will be no deactivation of a catalyst. Preferably they are 20 degreeC or more and 220 degrees C or less, More preferably, they are 20 degreeC or more and 200 degrees C or less. The time required for the reaction varies depending on the purpose or reaction conditions, but is usually within 96 hours, particularly preferably in the range of 30 minutes to 30 hours.

(Process 3)
Next, the process of synthesizing the second stage polyamic acid will be described. The method of synthesizing the second stage polyamic acid can be carried out in the same manner as the first stage polyamic acid.

  The polymerization reaction temperature in the second stage is preferably 0 ° C. or higher and 250 ° C. or lower, preferably 0 ° C. or higher and 100 ° C. or lower, and particularly preferably 0 ° C. or higher and 80 ° C. or lower from the viewpoint of the molecular weight of the resulting polyimide precursor. Recovery of the polyimide precursor after completion of production can be performed by distilling off the solvent in the reaction solution under reduced pressure.

  Examples of the method for purifying the polyimide precursor include a method of removing insoluble acid dianhydride and diamine in the reaction solution by vacuum filtration, pressure filtration, or the like. Moreover, the purification method by what is called reprecipitation which adds a reaction solution to a poor solvent and precipitates can be implemented. Further, when a particularly high-purity polyimide precursor is required, purification by an extraction method using supercritical carbon dioxide is also possible.

  The end of the polymer main chain of the polyimide precursor is preferably end-capped with an end-capping agent made of a monoamine derivative or a carboxylic acid derivative. Storage stability is improved by end-capping the polymer main chain of the polyimide precursor.

  Examples of the end capping agent comprising a monoamine derivative include aniline, o-toluidine, m-toluidine, p-toluidine, 2,3-xylidine, 2,6-xylidine, 3,4-xylidine, and 3,5-xylidine. O-chloroaniline, m-chloroaniline, p-chloroaniline, o-bromoaniline, m-bromoaniline, p-bromoaniline, o-nitroaniline, p-nitroaniline, m-nitroaniline, o-aminophenol P-aminophenol, m-aminophenol, o-anisidine, m-anisidine, p-anisidine, o-phenetidine, m-phenetidine, p-phenetidine, o-aminobenzaldehyde, p-aminobenzaldehyde, m-aminobenzaldehyde, o-aminobenzonitrile, p-aminobenzonitrile Lyl, m-aminobenzonitrile, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2-aminophenylphenyl ether, 3-aminophenylphenyl ether, 4-aminophenylphenyl ether, 2-aminobenzophenone, 3 -Aminobenzophenone, 4-aminobenzophenone, 2-aminophenyl phenyl sulfide, 3-aminophenyl phenyl sulfide, 4-aminophenyl phenyl sulfide, 2-aminophenyl phenyl sulfone, 3-aminophenyl phenyl sulfone, 4-aminophenyl phenyl sulfone , Α-naphthylamine, β-naphthylamine, 1-amino-2-naphthol, 5-amino-1-naphthol, 2-amino-1-naphthol, 4-amino-1-naphthol, 5-amino Aromatic monoamines such as 2-naphthol, 7-amino-2-naphthol, 8-amino-1-naphthol, 8-amino-2-naphthol, 1-aminoanthracene, 2-aminoanthracene, 9-aminoanthracene Of these, derivatives of aniline are preferably used. These may be used alone or in combination of two or more.

  Examples of the terminal blocking agent comprising a carboxylic acid derivative include carboxylic anhydride derivatives, such as phthalic anhydride, 2,3-benzophenone dicarboxylic anhydride, 3,4-benzophenone dicarboxylic anhydride, 2,3- Dicarboxyphenyl phenyl ether anhydride, 3,4-dicarboxyphenyl phenyl ether anhydride, 2,3-biphenyl dicarboxylic acid anhydride, 3,4-biphenyl dicarboxylic acid anhydride, 2,3-dicarboxyphenyl phenyl sulfone anhydride 3,4-dicarboxyphenyl phenyl sulfone anhydride, 2,3-dicarboxyphenyl phenyl sulfide anhydride, 3,4-dicarboxyphenyl phenyl sulfide anhydride, 1,2-naphthalenedicarboxylic acid anhydride, 2, 3-Naphthalenedicarboxylic anhydride, 1,8-naphthalene Carboxylic acid anhydride, 1,2-anthracene dicarboxylic acid anhydride, 2,3-anthracene dicarboxylic acid anhydride, 1,9-aromatic dicarboxylic acid anhydrides such as anthracene dicarboxylic acid anhydride. Of these aromatic dicarboxylic acid anhydrides, phthalic anhydride is preferably used. These may be used alone or in combination of two or more.

  In addition to the polyamic acid structure in the main chain, the polyimide precursor preferably has a functional group selected from the group consisting of a carboxyl group, an aromatic hydroxyl group, and a sulfonic acid group. Such a polyimide precursor may be copolymerized with, for example, a diamine having a carboxyl group, an aromatic hydroxyl group, or a sulfonic acid group, or a carboxyl group or aromaticity in the molecular structure with the diamine-terminated polyimide precursor. It can also be obtained by reacting with an acid anhydride having a hydroxyl group or a sulfonic acid group, or by reacting an acid anhydride terminal polyimide precursor with an amine compound having a carboxyl group, an aromatic hydroxyl group or a sulfonic acid group. Can do.

  Examples of the amine compound having a carboxyl group, an aromatic hydroxyl group, or a sulfonic acid group in the molecular structure include 2-aminobenzoic acid, 3-aminobenzoic acid, and 4-aminobenzoic acid.

  Examples of the acid anhydride having a carboxyl group, an aromatic hydroxyl group, or a sulfonic acid group in the molecular structure include carboxyl group-containing acid anhydrides such as trimellitic acid anhydride.

  As for the introduction rate of the site derived from the functional group selected from a carboxyl group, an aromatic hydroxyl group, and a sulfonic acid group at the end of the polymer main chain, in order to improve developability, the range that does not impair the flexibility of the resulting resin layer To decide. Preferably, it is 0.5 mol% or more and 10 mol% or less.

  Further, for the purpose of controlling the alkali solubility of the alkali-soluble resin, a dissolution inhibitor may be included. In the present invention, the dissolution inhibitor refers to a compound that hydrogen bonds with a carboxyl group of an alkali-soluble resin containing a carboxyl group. When the carboxyl group of the alkali-soluble resin is hydrogen-bonded with the dissolution inhibitor, it is shielded from the alkaline liquid and the dissolution can be controlled.

  Examples of the compound having a group capable of hydrogen bonding with a carboxyl group include a carboxylic acid compound, a carboxylic acid ester compound, an amide compound, and a urea compound. An amide compound and a urea compound are preferable from the viewpoint of the effect of inhibiting dissolution in an alkaline aqueous solution and storage stability.

  Examples of the amide compound include N, N-diethylacetamide, N, N-diisopropylformamide, N, N-dimethylbutyramide, N, N-dibutylacetamide, N, N-dipropylacetamide, N, N-dibutylformamide. N, N-diethylpropionamide, N, N-dimethylpropionamide, N, N′-dimethoxy-N, N′-dimethyloxamide, N-methyl-ε-caprolactam, 4-hydroxyphenylbenzamide, salicylamide, salicylanilide , Acetanilide, 2′-hydroxyphenylacetanilide, 3′-hydroxyphenylacetanilide, 4′-hydroxyphenylacetanilide.

  Among these, from the viewpoint of lowering the Tg of the insulating layer after heat curing, an amide compound containing an aromatic hydroxyl group is more preferable. Specific examples include 4-hydroxyphenylbenzamide, 3'-hydroxyphenylacetanilide, and 4'-hydroxyphenylacetanilide. These may be used alone or in combination of two or more.

  Examples of the urea compound include 1,3-dimethylurea, tetramethylurea, tetraethylurea, 1,3-diphenylurea, and 3-hydroxyphenylurea. Among these, from the viewpoint of lowering the Tg of the insulating layer after heat curing, a urea compound containing an aromatic hydroxyl group is more preferable. Specific examples include 3-hydroxyphenylurea. These may be used alone or in combination of two or more.

  In the case of using an amide compound, the dissolution inhibitor is preferably blended in an amount of 0.1 mol to 1.5 mol or less from the viewpoint of the dissolution inhibition effect with respect to 1 mol of the carboxylic acid of the alkali-soluble resin. It is more preferable to add 0 mol.

  When a urea compound is used, the dissolution inhibitor is preferably 0.1 mol to 1.5 mol or less from the viewpoint of the dissolution inhibition effect with respect to 1 mol of the carboxyl group of the alkali-soluble resin. From the viewpoint of the dissolution inhibiting effect and the mechanical properties of the polyimide obtained by curing after alkali development, it is more preferable to add 0.15 mol to 0.5 mol.

  Moreover, when using both an amide compound and a urea compound, the total amount of an amide compound and a urea compound is 0.1 mol-1.5 mol with respect to 1 mol of carboxylic acids of alkali-soluble resin from a viewpoint of a dissolution inhibitory effect. The range of is preferable.

  Moreover, it is preferable to contain a phosphorus compound from the point of the resin layer flame retardance by an alkali-soluble resin composition. A phosphorus compound will not be limited if it is a compound which contains a phosphorus atom in a structure. Examples of such compounds include phosphate ester compounds and phosphazene compounds.

  Examples of the phosphoric acid ester compound include trimethyl phosphate, triethyl phosphate, tributyl phosphate, triisobutyl phosphate, tris (2-ethylhexyl) phosphate, phosphate ester having tris (2-ethylhexyl) phosphate as a substituent, tris (butoxyethyl) phosphate ( Aromatics such as phosphate esters, triphenyl phosphates, tricresyl phosphates, trixylenyl phosphates, resorcinol bis (diphenyl phosphates) substituted with aliphatic organic groups containing oxygen atoms such as TBXP) Examples thereof include phosphate ester compounds having an organic group as a substituent. Among these, TBXP and triisobutyl phosphate are preferable from the viewpoint of developability.

  Examples of the phosphazene compound include structures represented by the following general formula (6) and the following general formula (7).

（上記一般式（６）及び上記一般式（７）で表されるホスファゼン化合物におけるＲ_１７、Ｒ_１８、Ｒ_１９、及びＲ_２０としては、炭素数１〜炭素数２０の有機基であれば限定されない。炭素数１以上であれば、難燃性が発現する傾向にあるため好ましい。炭素数２０以下であれば、ポリイミド前駆体と相溶する傾向にあるため好ましい。この中で、難燃性発現の観点から、炭素数６以上炭素数１８以下の芳香族性化合物に由来する官能基が特に好ましい。）

(R ₁₇ , R ₁₈ , R ₁₉ , and R ₂₀ in the phosphazene compound represented by the general formula (6) and the general formula (7) are limited as long as they are organic groups having 1 to 20 carbon atoms. If it has 1 or more carbon atoms, it is preferable because flame retardancy tends to be exhibited, and if it has 20 or less carbon atoms, it is preferable because it tends to be compatible with the polyimide precursor. From the viewpoint of expression, a functional group derived from an aromatic compound having 6 to 18 carbon atoms is particularly preferable.)

  As such a functional group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 2-hydroxyphenyl group, 3-hydroxyphenyl group, 4-hydroxyphenyl group, 2-cyanophenyl Group, functional group having a phenyl group such as 3-cyanophenyl group and 4-cyanophenyl group, functional group having a naphthyl group such as 1-naphthyl group and 2-naphthyl group, pyridine, imidazole, triazole, tetrazole and the like. And functional groups derived from nitrogen heterocyclic compounds. These compounds may be used alone or in combination of two or more as required. Among these, a compound having a phenyl group, a 4-hydroxyphenyl group, and a 4-cyanophenyl group is preferable because of availability.

  X in the phosphazene compound represented by the general formula (6) is not limited as long as it is an integer of 3 or more and 25 or less. When X is 3 or more, flame retardancy is exhibited, and when it is 25 or less, solubility in an organic solvent is high. Among these, X is preferably 3 or more and 10 or less because of availability.

  Y in the phosphazene compound represented by the general formula (7) is not limited as long as it is an integer of 3 or more and 10,000 or less. If Y is 3 or more, flame retardancy is exhibited, and if it is 10,000 or less, the solubility in organic solvents is high. Among these, Y is preferably 3 or more and 100 or less because of availability.

A and B in the phosphazene compound represented by the general formula (7) are not limited as long as they are organic groups having 3 to 30 carbon atoms. In this, A is _{-N = P (OC 6 H 5} ) 3, -N = P (OC 6 H 5) 2 (OC 6 H 4 OH), - N = P (OC 6 H 5) (OC 6 _{H 4 OH) 2, -N =} P (OC 6 H 4 OH) 3, -N = P (O) OC 6 H 5, -N = P (O) (OC 6 H 4 OH) are preferred. B is _{-P (OC 6 H 5) 4} , -P (OC 6 H 5) 3 (OC 6 H 4 OH), - P (OC 6 H 5) 2 (OC 6 H 4 OH) 2, -P ( _{OC 6 H 5) (OC 6} H 4 OH) 3, -P (OC 6 H 4 OH) 4, -P (O) (OC 6 H 5) 2, -P (O) (OC 6 H 4 OH) _2, such as _{-P (O) (OC 6 H} 5) (OC 6 H 4 OH) are preferred. A phosphorus compound may be used alone or in combination of two or more.

  The addition amount of the phosphorus compound is preferably 50 parts by mass or less from the viewpoint of photosensitivity with respect to 100 parts by mass of the polyimide precursor. From the viewpoint of flame retardancy of the cured product, 45 parts by mass or less is preferable, and 40 parts by mass or less is more preferable.

  The alkali-soluble resin composition may contain a solvent in which a polyimide precursor, a phosphorus compound, and the like can be uniformly dissolved and / or dispersed as necessary. As a solvent, the solvent used for the synthesis | combination of the above-mentioned polyimide precursor can be used.

  The solvent which comprises the alkali-soluble resin composition containing a polyimide precursor will not be limited if it can melt | dissolve and / or disperse | distribute a polyimide precursor uniformly. Examples of such solvents include C2-C9 ether compounds such as dimethyl ether, diethyl ether, methyl ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; acetone, methyl ethyl ketone, and the like. Ketone compounds having 2 to 6 carbon atoms; saturated hydrocarbon compounds having 5 to 10 carbon atoms such as normal pentane, cyclopentane, normal hexane, cyclohexane, methylcyclohexane and decalin; benzene, toluene, xylene, mesitylene, Aromatic hydrocarbon compounds having 6 to 10 carbon atoms such as tetralin; 3 to 3 carbon atoms such as methyl acetate, ethyl acetate, γ-butyrolactone, methyl benzoate 9-prime ester compounds; halogen-containing compounds having 1 to 10 carbon atoms such as chloroform, methylene chloride, and 1,2-dichloroethane; acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl Examples thereof include nitrogen-containing compounds having 2 to 10 carbon atoms such as -2-pyrrolidone; sulfur-containing compounds such as dimethyl sulfoxide. These may be one kind or a mixture of two or more kinds as necessary. Particularly preferable solvents include ether compounds having 2 to 9 carbon atoms, ester compounds having 3 to 9 carbon atoms, aromatic hydrocarbon compounds having 6 to 10 carbon atoms, and 2 to 10 carbon atoms. A nitrogen-containing compound is mentioned. Moreover, 1 type or 2 or more types of mixtures may be sufficient as needed. From the viewpoint of solubility of the polyimide precursor, triethylene glycol dimethyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N-dimethylformamide, and N, N-dimethylacetamide are preferable.

  The density | concentration of the polyimide precursor in the alkali-soluble resin composition which consists of a polyimide precursor and a solvent will not be restrict | limited especially if it is a density | concentration with which a resin molding is manufactured. The concentration of the polyimide precursor is preferably 1% by mass or more from the viewpoint of the film thickness of the resin molded body to be produced, and the concentration of the polyimide precursor is preferably 90% by mass or less from the uniformity of the film thickness of the resin molded body. From the viewpoint of the film thickness of the resulting resin layer, it is more preferably 2% by mass or more and 80% by mass or less.

  It is also preferable to add a crosslinking agent to the alkali-soluble resin composition. This makes it possible to increase the molecular weight of the alkali-soluble resin during curing. As the crosslinking agent, for example, a diamine compound having a carbonate protecting group or a carbamate protecting group is preferable. It is preferable to add 0.1 mass part-10 mass parts of compounding quantities of a crosslinking agent with respect to 100 mass parts of polyimide precursors.

  The alkali-soluble resin composition can contain other compounds as long as the performance is not adversely affected. Specific examples include heterocyclic compounds for improving adhesion. The heterocyclic compound is not limited as long as it is a cyclic compound containing a hetero atom. Here, examples of the hetero atom include oxygen, sulfur, nitrogen, and phosphorus.

  Heterocyclic compounds include 2-methylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, imidazole such as 2-phenylimidazole, and N-alkyl group-substituted imidazole such as 1,2-dimethylimidazole. Aromatic group-containing imidazole such as 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1- Cyanoethyl-containing imidazole such as cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, imidazole compounds such as silicon-containing imidazole such as imidazolesilane, 5-methylbenzotriazole, 1- (1 ′, 2′- The And triazole compounds such as 1- (2-ethylhexylaminomethylbenzotriazole), tetrazole compounds such as 5-phenyltetrazole, and oxazole compounds such as 2-methyl-5-phenylbenzoxazole. .

  The addition amount of other compounds is not limited as long as it is 0.01 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polyimide precursor. If it is 0.01 mass part or more, there exists a tendency for adhesiveness to fully improve, and if it is 30 mass parts or less, there will be no bad influence on alkali solubility.

  Other specific additives include adhesion improvers, surfactants, antioxidants, UV inhibitors, light stabilizers, plasticizers, waxes, fillers, pigments, dyes, foaming agents, extinguishing agents. Examples include foaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, leveling agents, dispersants, and ethylenically unsaturated compounds.

  The alkali-soluble resin composition according to the present invention can be prepared by mixing the above components by a conventional method. Specifically, for example, a laika machine equipped with a stirring device and a heating device, a three-roll, a ball mill, a planetary mixer, and the like can be used. Moreover, you may use these mixing apparatuses in combination of 2 or more types suitably.

  The alkali-soluble resin composition according to the present invention can be suitably used for a single-sided flexible substrate suitable for manufacturing double-sided and multilayer flexible printed wiring boards having blind vias. From the viewpoint of producing a single-sided flexible substrate, the concentration of the polyimide precursor in the alkali-soluble resin composition is preferably 1% by mass or more and 90% by mass or less. The concentration of the polyimide precursor is preferably 1% by mass or more from the viewpoint of the film thickness of the single-sided flexible substrate, and preferably 90% by mass or less from the viewpoint of the viscosity of the alkali-soluble resin composition and the uniformity of the film thickness. From the viewpoint of the film thickness of the obtained single-sided flexible substrate, it is more preferably 2% by mass or more and 80% by mass or less.

  Next, the manufacturing method of a single-sided flexible substrate is demonstrated. First, a base material is coated with an alkali-soluble resin composition. The substrate is not particularly limited as long as it is a coating and drying facility capable of continuous production in roll-to-roll. Examples of such a substrate include a metal film, a glass cloth, and a carrier film. A carrier film is preferable from the viewpoint of continuous productivity and handling. In the present invention, examples of the carrier film include polyethylene terephthalate fill. A polyethylene terephthalate film is particularly preferable from the viewpoint of good handling and peelability after pressure bonding to the substrate.

  Examples of the coating method include bar coating, roller coating, die coating, blade coating, dip coating, doctor knife, spray coating, flow coating, spin coating, slit coating, and brush coating. After coating, if necessary, heat treatment called pre-baking may be performed with a hot plate or the like.

  When using an alkali-soluble resin composition, a solution obtained by applying a solution of the alkali-soluble resin composition on an arbitrary substrate such as a carrier film by an arbitrary method and then drying, and forming a laminate obtained by forming the alkali-soluble resin composition layer into a dry film Form. An optional antifouling or protective cover film may be provided on the alkali-soluble resin composition layer of the laminate. In the laminate according to the present invention, the cover film is not limited as long as it is a film that protects an alkali-soluble resin composition such as low-density polyethylene.

  Next, a conductive base material is heat-pressed to the laminate to form a single-sided flexible substrate composed of three layers of conductive base material / alkali-soluble resin layer composition layer / carrier film. As such a forming method, the protective cover film is peeled off from the alkali-soluble resin composition layer of the present invention and in contact with the conductive substrate, hot pressing, thermal laminating, thermal vacuum pressing, thermal vacuum Examples include a method of laminating. Among these, from the viewpoint of adhesiveness with the alkali-soluble resin composition layer, a heat vacuum press and a heat vacuum laminate are preferable. Furthermore, from the viewpoint of productivity by roll-to-roll, thermal vacuum lamination is particularly preferable. Examples of the conductive substrate include electrolytic copper foil, rolled copper foil, electrodeposition film, film with conductive paste, aluminum foil film, and stainless steel foil film. The conductive base film in the present invention is preferably an electric field copper foil from the viewpoint of electrical conductivity and adhesiveness with a resin layer.

  The heating temperature at the time of bonding the alkali-soluble resin composition layer is not limited as long as it is a temperature capable of being in close contact with the conductive substrate. From the viewpoint of adhesion to the conductive substrate, 50 ° C. or higher and 150 ° C. or lower is preferable. More preferably, it is 50 degreeC or more and 120 degrees C or less.

  The alkaline solution is not limited as long as the alkali-soluble resin composition layer can be dissolved. Examples of such a solution include a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and a tetramethylammonium hydroxide aqueous solution. From the viewpoint of generally used production equipment and process conditions, an aqueous sodium carbonate solution and an aqueous sodium hydroxide solution are preferred. Examples of the development method include spray development, immersion development, and paddle development.

  Subsequently, the single-sided flexible substrate comprising the alkali-soluble resin layer of the present invention and a conductive substrate is cured by heating. The heat curing is preferably performed at a temperature of 120 ° C. or higher and 400 ° C. or lower from the viewpoint of solvent removal, side reaction, decomposition, and the like, and from the viewpoint of imidization of the polyamic acid. More preferably, it is 150 degreeC or more and 300 degrees C or less.

  The reaction atmosphere in heat curing can be carried out in an air atmosphere or an inert gas atmosphere. Although the time required for heat curing varies depending on the reaction conditions, it is usually within 24 hours, particularly preferably 1 to 8 hours.

  In the method for producing a flexible printed wiring board using the alkali-soluble resin composition as an insulating layer in the present invention, the alkali-soluble resin composition is used in the blind via forming step for interlayer connection of the flexible wiring board instead of the conventional laser processing. By using a resin layer as an interlayer adhesive containing, a blind via can be easily formed using an alkaline liquid spray device or the like generally used in the manufacturing process of a flexible printed wiring board. For this reason, the manufacturing method of the double-sided flexible wiring board and multilayer flexible wiring board which can reduce a blind via formation cost significantly, can perform roll-to-roll production easily, and can reduce a production lead time significantly is realizable.

(Example)
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples made to clarify the effects of the present invention, but the present invention is not limited to these examples.

[Alkali dissolution test of alkali-soluble resin]
Evaluation of the solubility characteristics of the alkali-soluble resin was carried out according to the following procedure. A polyester film (R-310-25 / Mitsubishi Polyester Co., Ltd.) was laid on a coating table (Matsuki Kagaku Co., Ltd.) that can be vacuum-adsorbed and heated, and the polyester film was attached by vacuum adsorption. The alkali-soluble resin was applied onto the polyester film using an applicator (manufactured by Matsuki Kagaku) with a gap of 250 μm. Thereafter, the solvent was removed with a dryer (SPH-201 / Espec Corp.) at 95 ° C. for 30 minutes.

  The obtained film is overlaid on the resin layer side of the electrolytic copper foil (F1-WS / Furukawa Circuit Foil Co., Ltd.) on the rough surface side, using a vacuum press (Tester Sangyo Co., Ltd.) at 90 ° C. and 0.5 MPa. Pressure bonding was performed for 1 minute. Furthermore, after laminating a dry film resist (DFR) (Sanfort AQ2578, manufactured by Asahi Kasei E-Materials Co., Ltd.) on the electrolytic copper foil side to form a 500 μmφ circular hole pattern, The copper foil was removed by etching.

  Thereafter, a 3 wt% sodium hydroxide aqueous solution heated to 50 ° C. is sprayed at a pressure of 0.18 MPa, and the dissolution time is defined as the time required for the film to be completely dissolved. Was calculated by dividing the film thickness (μm) before dissolution by the dissolution time (sec) and multiplying by 100.

[Elastic modulus]
It formed into a film on copper foil so that it might become a film thickness of about 30 micrometers using an alkali-soluble resin composition. Then, it heat-processed at 120 degreeC for 1 hour, and 180 degreeC for 1 hour, Then, the copper foil part was dissolved with the ferric chloride aqueous solution, and it was made to dry at room temperature after washing with tap water, and the film was obtained. The obtained film was cut out into 5 mm x 100 mm, and it was set as the test piece. The obtained test piece was measured with a tensile tester (RTG-1210 / A & D).

[Glass transition temperature]
It formed into a film on copper foil so that it might become a film thickness of about 30 micrometers using an alkali-soluble resin composition. Then, it heat-processed at 120 degreeC for 1 hour, and 180 degreeC for 1 hour, Then, the copper foil part was dissolved with the ferric chloride aqueous solution, and it was made to dry at room temperature after washing with tap water, and the film was obtained. The obtained film was cut into 3 mm x 50 mm, and it was set as the test piece. The obtained test piece was measured with a TMA tester (EXSTAR6000 / manufactured by Seiko Instruments Inc.).

〔reagent〕
As reagents, silicone diamine (KF-8010) (manufactured by Shin-Etsu Chemical Co., Ltd.), ethylene glycol-bis-trimellitic anhydride ester (TMEG) (manufactured by Shin Nippon Chemical Co., Ltd.), 1,3-bis (3-aminophenoxy) Benzene (APB-N) (manufactured by Mitsui Chemicals), tris (butoxyethyl) phosphate (TBXP) (manufactured by Daihachi Chemical Co., Ltd.), phosphazene compound (FP-100) (manufactured by Fushimi Pharmaceutical Co., Ltd.), toluene (Wako Pure Chemical Industries, Ltd.) Kogyo Co., Ltd. (for organic synthesis), γ-butyrolactone (Wako Pure Chemical Industries, Ltd.), and triethylene glycol dimethyl ether (Wako Pure Chemical Industries, Ltd.) were used without any special purification.

[Preparation Example]
In a separable flask under nitrogen atmosphere, γ-butyrolactone (42.0 g), triethylene glycol dimethyl ether (18.0 g), toluene (20.0 g), silicone diamine (KF-8010, 19.54 mmol), TMEG (40 0.0000 mmol), a Dean-Stark apparatus and a refluxer were attached, and the mixture was heated and stirred at 180 ° C. for 30 minutes. After removing toluene, which is an azeotropic solvent, the mixture was cooled to 25 ° C., silicone diamine (KF-8010, 4.89 mmol) and APB-N (15.56 mmol) were added, and the mixture was stirred at 25 ° C. for 5 hours. After stirring, a mixed solvent of γ-butyrolactone / triethylene glycol dimethyl ether was added so that the polymer solid concentration would be 30% by weight to obtain a polyimide precursor solution. Furthermore, with respect to 100 mass parts of polyimide precursors, TBXP (10 mass parts) and FP-100 (7 mass parts) were mixed to prepare an alkali-soluble resin composition. The alkali dissolution rate after lamination with the electrolytic copper foil was 3 μm / sec, the elastic modulus after the heating treatment was 0.25 GPa, and the glass transition temperature was 58 ° C.

Example 1
Examples of the double-sided flexible wiring board using the method for manufacturing a flexible wiring board according to the above embodiment will be described.

  The alkali-soluble resin composition solution of the adjustment example was applied on a polyester film using a die coater, and dried at 95 ° C. for 30 minutes to prepare a film having a thickness of 25 μm. This laminated film is laminated on the rough side of an electrolytic copper foil (thickness 12 μm, F1-WS / Furukawa Circuit Foil Co., Ltd.) and laminated at 90 ° C. and 0.5 MPa for 1 minute using a vacuum press to form a single-sided flexible substrate. Produced.

  A dry film was laminated on the copper foil, exposed and developed, and then a conformal mask having a 75 μmφ circular hole was formed by etching using ferric chloride. Further, a 3% sodium hydroxide solution was sprayed for 30 seconds at the site where the copper foil was removed to dissolve and remove the resin layer, thereby forming a blind via. In general, copper foil etching and sodium hydroxide solution spraying can be performed in a continuous apparatus.

  Next, after peeling the polyester film on the back surface, the resin layer (adhesive) containing the alkali-soluble resin composition was cured by heating at 180 ° C. for 1 hour using a curing and drying furnace.

  Next, using a vacuum press, the rough surface side of another electrolytic copper foil is laminated so as to be in contact with the resin layer (adhesive) and laminated at 120 ° C. and 1.0 MPa for 1 minute to form a laminated via via. A flexible substrate was produced. In addition, bonding with copper foil can also be performed continuously using a laminator. Resin residue was not observed on the wall surface and bottom of the obtained blind via, the blind via formation was good, and the desmear process was unnecessary.

  Next, blind via plating similar to the conventional double-sided flexible wiring board was performed. First, after electroless copper plating or carbon fine particles were adhered to the resin layer on the inner wall of the hole, electrolytic copper plating was applied to complete electrical connection on both sides. Next, the same circuit formation process as the conventional double-sided flexible wiring board was performed. Subsequent steps were performed in the same manner as the conventional method for manufacturing a double-sided flexible wiring board.

  As described above, in the conventional blind via formation of the double-sided flexible wiring board, since each hole was processed using a laser processing machine, a great deal of cost and time were required. In the present invention, by using an alkali-soluble resin composition having adhesiveness, a conventional copper etching apparatus, alkali spray apparatus, and laminator can be used, and a blind via can be formed at low cost and in a short time. Became possible. In addition, since roll-to-roll production is easy, continuous automated production by roll-to-roll including the subsequent processes has become possible.

(Example 2)
Next, examples of the multilayer flexible wiring board using the method for manufacturing a flexible wiring board according to the above embodiment will be described.

  First, a double-sided flexible wiring board is manufactured as a core substrate. You may use the double-sided flexible wiring board produced by Example 1 as a core board | substrate. In parallel, two sets of single-sided flexible substrates laminated with copper foil using an alkali-soluble resin composition as an adhesive are prepared. The alkali-soluble resin composition solution of the adjustment example was applied on a polyester film using a die coater, and dried at 95 ° C. for 30 minutes to prepare a film having a thickness of 25 μm. This laminated film is laminated on the rough side of an electrolytic copper foil (thickness 12 μm, F1-WS / Furukawa Circuit Foil Co., Ltd.) and laminated at 90 ° C. and 0.5 MPa for 1 minute using a vacuum press to form a single-sided flexible substrate. Produced.

  A dry film was laminated on the copper foil, exposed and developed, and then the copper foil at a predetermined position was removed by ferric chloride etching to form a conformal mask having a 75 μmφ circular hole at the site. Further, a 3% sodium hydroxide solution was sprayed for 30 seconds at the site where the copper foil was removed, and the resin layer was dissolved and removed to form a blind via. In general, copper foil etching and sodium hydroxide solution spraying can be performed in a continuous apparatus.

  Next, after peeling the polyester film on the back surface, the resin layer (adhesive) containing the alkali-soluble resin composition was cured by heating at 180 ° C. for 1 hour using a curing and drying furnace.

  Next, the single-sided flexible board on which the blind vias are formed is positioned at predetermined positions on both the upper and lower surfaces of the core board and laminated by using a vacuum press at 120 ° C. and 1.0 MPa for 1 minute. A multilayer flexible substrate consisting of four layers formed with blind vias was produced. Bonding with copper foil can also be performed continuously using a laminator. Resin residue was not observed on the wall surface and bottom of the obtained blind via, the blind via formation was good, and the desmear process was unnecessary.

  Next, blind via plating similar to that for the multilayer flexible wiring board was performed. First, after electroless copper plating or carbon fine particles were adhered to the resin layer on the inner wall of the hole, electrolytic copper plating was applied to complete electrical connection on both sides. Next, the same circuit formation process as the conventional multilayer flexible wiring board was performed. The subsequent steps were performed in the same manner as the conventional method for manufacturing a flexible wiring board.

  As described above, the conventional blind via formation of the multilayer flexible wiring board has been processed one hole at a time using a laser processing machine, and therefore requires a great deal of cost and time. In the present invention, by using an alkali-soluble resin composition having adhesiveness, a copper etching apparatus, an alkali spray apparatus, and a laminator can be used conventionally, and a blind via can be simultaneously formed at low cost and in a short time. It became possible to form.

(Example 3)
Next, an example of a multilayer flexible wiring board having a flexible part using the method for manufacturing a flexible wiring board according to the above embodiment will be described.

  First, a double-sided flexible wiring board is manufactured as a core substrate. You may use the double-sided flexible wiring board by Example 1 as a core board | substrate. In parallel, two types of single-sided flexible substrates prepared by laminating copper foil with an alkali-soluble resin composition as an adhesive are prepared. The alkali-soluble resin composition solution of the adjustment example was applied on a polyester film using a die coater, and dried at 95 ° C. for 30 minutes to prepare a film having a thickness of 25 μm. This laminated film is laminated on the rough side of an electrolytic copper foil (thickness 12 μm, F1-WS / Furukawa Circuit Foil Co., Ltd.) and laminated at 90 ° C. and 0.5 MPa for 1 minute using a vacuum press to form a single-sided flexible substrate. Produced.

  A dry film was laminated on the copper foil, exposed and developed, and then the copper foil at a predetermined position was removed by ferric chloride etching to form a conformal mask having a 75 μmφ circular hole at the site. At the same time, the copper foil was also removed by etching for the flexible portion where the outer layer substrate had to be peeled off.

  Next, spray 3% sodium hydroxide solution for 30 seconds on the part where the copper foil has been removed, dissolve and remove the resin layer to form a blind via, and simultaneously dissolve and remove the resin layer part that needs to be peeled off the outer substrate. did. In general, copper foil etching and sodium hydroxide solution spraying can be performed in a continuous apparatus.

  Next, after peeling the polyester film on the back, the adhesive made of the alkali-soluble resin composition was cured by heating at 180 ° C. for 1 hour using a curing and drying furnace.

  Next, single-sided flexible substrates with blind vias formed on the upper and lower surfaces of the core substrate are respectively aligned at predetermined positions, and laminated using a vacuum press at 120 ° C. and 1.0 MPa for 1 minute. A double-sided flexible substrate with blind vias was prepared.

  As a result, a blind via is formed between the core substrate on which the circuit has been formed and the single-sided flexible substrate. The outer layer peeling portion is laminated on the core substrate with the outer resin layer cut out.

  Next, blind via plating similar to that for the multilayer flexible wiring board was performed. In this step, a plating mask is applied to the peeling portion of the outer layer in order to prevent blind via plating adhesion. For this reason, although a dry film is laminated | stacked on this part, while preventing plating adhesion by this, the reinforcement | strengthening of a base material can be achieved in a subsequent process. Then, after electroless copper plating or carbon fine particles were adhered to the resin layer on the inner wall of the hole, electrolytic copper plating was performed to complete the electrical connection on both sides. Next, a circuit forming process similar to that of the conventional multilayer flexible wiring board is performed. At this time, the outer layer cut-out portion is performed in a state protected by the above-described dry film. The subsequent steps were performed in the same manner as the conventional method for manufacturing a flexible wiring board.

  As described above, in the conventional multilayer flexible wiring board, the peeling process of the outer substrate has been an obstacle, but according to the present invention, it can be easily performed simultaneously with the blind via forming process.

  The flexible wiring board of the present invention can be suitably used for various electronic components.

11, 21, 31, 51 Resin layer 12, 16, 22, 23, 30, 50, 102, 103 Copper foil 12a-12c, 21a, 30a-30d, 102a, 102b Blind via formation site 13, 115a, 115b Single-sided flexible Substrate 14 Conformal mask 15a-15c, 25, 32a-32d, 52a-52d Through hole 17a-17c, 35a-35d, 55a-55d, 104a, 104b, 117a, 117b Blind via 18, 26, 38, 58, 118 Copper plating 19, 28, 40, 60, 107 Circuit pattern 20, 24, 101, 111 Double-sided flexible substrate 27, 39, 59, 106, 119 Photosensitive dry film 29, 113 Core substrate 33, 34, 53, 54 Outer layer substrate 36, 56 Internal conductive layer 37, 57 Bushirubedenso 41,61 multilayer flexible wiring board 50a, 120 flexible portion 104 polyimide layer 112a, 112b coverlay 114a, 114b adhesive layer 116 through vias

Claims (12)

  A conductive layer forming step of forming a first conductive layer having a through hole forming site on one main surface of the resin layer containing the alkali-soluble resin composition; and the through hole forming site through the first conductive layer. A through hole forming step of forming a through hole by dissolving and removing the resin layer, and a blind via forming in which a second conductive layer is provided on the other main surface of the resin layer in which the through hole is formed to form a blind via A method of manufacturing a flexible wiring board, comprising: a step; and a plating step of electrically connecting the first conductive layer and the second conductive layer by plating the blind via. A core substrate made of either a single-sided flexible wiring board, a double-sided flexible wiring board, or a multilayer flexible wiring board, and an outer layer substrate are laminated, and a manufacturing method of a flexible wiring board,
An external conductive layer forming step of forming an external conductive layer having a through hole forming site on one main surface of the resin layer containing the alkali-soluble resin composition; and the resin at the through hole forming site through the external conductive layer A through hole forming step of forming a through hole in the outer layer substrate by dissolving and removing a layer; and the outer layer substrate and the core substrate so that the through hole of the outer layer substrate and a predetermined portion of the core substrate coincide with each other. And forming a blind via to form a blind via, and a plating step of electrically connecting the inner conductive layer of the core substrate and the outer conductive layer of the outer substrate by plating the blind via. A method for producing a flexible wiring board, comprising:   In the external conductive layer forming step, the external conductive layer in the flexible portion forming portion is removed, and in the through hole forming step, the resin layer in the flexible portion forming portion is dissolved and removed to form a flexible portion. The manufacturing method of the flexible wiring board of Claim 2.   The said alkali-soluble resin composition contains the polyimide precursor which has a polyamic acid structure at least, The manufacturing method of the flexible wiring board in any one of Claims 1-3 characterized by the above-mentioned.   The said polyimide precursor contains the block copolymer which has a polyamic-acid structure and a polyimide structure as a structural unit, respectively, The manufacturing method of the flexible wiring board of Claim 4 characterized by the above-mentioned.   6. The method for producing a flexible wiring board according to claim 4, wherein the polyimide precursor has a polyalkylene ether structure and / or a siloxane structure.   The method for producing a flexible wiring board according to claim 1, wherein the alkali-soluble resin composition further contains a dissolution inhibitor.   The method for producing a flexible wiring board according to claim 7, wherein the dissolution inhibitor is an amide compound or a urea compound.   The method for producing a flexible wiring board according to claim 1, wherein the alkali-soluble resin composition further contains a phosphorus compound.   The method for producing a flexible wiring board according to claim 9, wherein the phosphorus compound is a phosphate ester compound and / or a phosphazene compound.   The resin layer is obtained by applying an alkali-soluble resin composition on a conductive film substrate and removing the solvent layer having a thickness of 25 μm obtained after desolvation by heating in an aqueous sodium hydroxide solution of 0.50 μm / sec or more. Furthermore, the dissolution rate in a sodium hydroxide aqueous solution obtained by heating the resin layer at 160 ° C. or higher is 0.05 μm / sec or less, and the elastic modulus of the resin layer is 0.2 GPa to 1.5 GPa. The glass transition temperature of the resin layer is 150 ° C. or less, The method for manufacturing a flexible wiring board according to claim 1, wherein the resin layer has a glass transition temperature of 150 ° C. or lower.   The flexible wiring board manufactured by the manufacturing method of the flexible wiring board in any one of Claims 1-11.

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