JP2013021067A - Resin composition for forming protective film, dry film solder resist, coverlay film, flexible printed wiring board and manufacturing method of flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for forming a protective film which can ensure a required flexibility when used in a printed wiring board and can form a protective film having a high heat resistance in a required region.SOLUTION: The resin composition for forming a protective film that forms the protective film of a flexible printed wiring board 1 is constituted to contain a first curable resin component 5a and a second curable resin component 5b having different hardening conditions or hardening characteristics. A protective film having a required deformability is formed by principally curing the first curable resin component, and a protective film having a required heat resistance is formed by curing the first curable resin component and the second curable resin component.

Description

  The present invention relates to a protective film-forming resin composition, a dry film solder resist, a coverlay film, a flexible printed wiring board, and a method for producing a flexible printed wiring board. Specifically, the present invention relates to a resin composition for forming a protective film that can provide a flexible printed wiring board with a region having high heat resistance and a region having high flexibility when applied as a protective film for a flexible printed wiring board.

  Flexible printed wiring boards that are flexible and easy to process are frequently used in the field of electronic devices and the like. The flexible printed wiring board includes a conductive layer made of a copper foil laminated on a film-like insulating substrate, and is formed by forming a predetermined wiring pattern on the conductive layer.

  In the process of manufacturing the flexible printed wiring board, a protective film such as a solder resist or a coverlay film is laminated and formed for the purpose of protecting the wiring pattern.

  As the protective film, a photosensitive resist film used in photolithography is widely used. For example, a protective film composed of a photosensitive resin composition containing an epoxy resin compound as a curing component is laminated on a copper-clad laminate, cured by irradiating ultraviolet rays to the required part, and other parts dissolved and removed Known dry film resists are known.

  However, the conventional dry film resist has low flexibility after curing. For this reason, in the state where the dry film resist remains, it is difficult to use the flexible printed wiring board for bending. For this reason, a technique is often employed in which only the finely processed portion is processed using the dry film resist while the dry film resist is removed after processing and a cover lay film having high flexibility is laminated.

JP 2007-108761 A

  The cover lay film is formed by applying an adhesive to a polyimide film. The cover lay film is formed into a predetermined shape by a mold or the like before lamination, and is then attached to the wiring pattern surface by a hot press or the like. Since the coverlay film has high flexibility, the wiring pattern can be protected without impairing the flexibility of the flexible printed wiring board.

  However, the cover lay film is often attached using an adhesive having low heat resistance in order to enhance the flexibility of the flexible printed wiring board. For this reason, it is difficult to use it as a solder resist film when performing a solder reflow process for mounting an electronic component on a flexible printed wiring board. In recent years, photosensitive coverlay films with improved heat resistance have also been developed. However, the heat resistance for performing solder reflow processing for mounting electronic components is not sufficient, and the protective film is used as a wiring pattern formation surface. Problems such as peeling from the reinforcing plate often occur.

  The coverlay film is cut into a predetermined shape by a press or the like in advance according to the wiring pattern or the like, and laminated on the wiring pattern surface via the adhesive. However, it is difficult to align the coverlay film and the flexible printed wiring board, and a protective film cannot be formed with high accuracy. In addition, the manufacturing process is complicated, and there is a problem in that the yield is lowered.

  The present invention solves the above-mentioned conventional problems, and can be used for a flexible printed wiring board to ensure the required flexibility and to form a protective film-forming resin composition that can form a protective film with high heat resistance in a required region. The issue is to provide.

  The invention described in claim 1 is a resin composition for forming a protective film for forming a protective film of a flexible printed wiring board, wherein the first curable resin component and the second curable resin have different curing conditions or curing characteristics. And a protective film having a required deformability is formed by mainly curing the first curable resin component, and the first curable resin component and the first curable resin component. By curing the curable resin component 2, a protective film having required heat resistance is formed.

  The resin composition for forming a protective film according to the present invention includes a first curable resin component and a second curable resin component having different curing conditions and curing characteristics. For this reason, the resin cured product which has a required characteristic according to the said hardening process is formed by performing a different hardening process. In particular, the resin composition for forming a protective film according to the present invention is configured so as to be able to impart the deformability required as a protective film of a flexible printed wiring board and the heat resistance against the temperature that acts during component mounting.

  A combination of curable resin components having different curing conditions or curing characteristics is not particularly limited. For example, two types of curable resin components having different curing temperatures can be combined as the first curable resin component and the second curable resin component. Moreover, the curable resin component from which hardening operation differs can be combined. For example, a photocurable resin can be employed as the first curable resin component, and a thermosetting resin can be employed as the second curable resin component. The first curable resin component and the second curable resin component are not only a curable resin but also a concept including various additives for curing the resin. In addition, the first curable resin component and the second curable resin component can be configured to include a plurality of curable resins.

  In the present invention, a protective film having a required deformability is formed mainly by curing the first curable resin component, and the first curable resin component and the second curable resin component are cured. By doing so, a protective film having required heat resistance is formed.

  It is not required that the curing conditions of the first curable resin component and the second curable resin component be completely different. For example, in the step of curing the first curable resin component, a part of the second curable resin component is cured, and in the step of curing the second curable resin component, the first curable resin component is not yet formed. It can comprise so that a hardening part may harden | cure. Moreover, when hardening a 2nd curable resin component, it can also comprise so that the hardening degree of a 1st curable resin component may increase.

  The deformability obtained by curing the first curable resin may be any one that can ensure the required flexibility when applied to a flexible blind wiring board. The heat resistance obtained by curing the second curable resin component is such that the protective film is peeled off when an electronic component is mounted on the flexible printed wiring board provided with the protective film by solder reflow processing. The heat resistance is set so as not to deteriorate.

  As in the invention described in claim 2, the first curable resin component that is cured by applying light or / and heat and exerts the required deformability on the protective film, and the electron beam act It is preferable to include a second curable resin component that is cured by causing the protective film to exhibit required heat resistance.

  As the first curable resin component, a known photocurable resin and / or thermosetting resin can be employed. The first curable resin component does not need to be completely cured by applying light or / and heat, and is preferably cured to the extent that it has the required deformability. Further, after the first curable resin component is cured to a degree of cure having a required deformability, in the step of applying an electron beam, the first curable resin component is not yet added together with the second curable resin component. It can also comprise so that a hardening part may harden | cure.

  On the other hand, as the second curable resin component, it is preferable to adopt one that is not cured by the action of light or heat that acts when the first curable resin is cured, or that is difficult to cure. For example, when the second curable resin component has a property of being cured by either electron beam irradiation or heating, it is not cured at the heating temperature for curing the first curable resin, but is cured by electron beam irradiation. What has a characteristic can be employ | adopted as a 2nd curable resin component. In the step of curing the first curable resin component, a part of the second curable resin component may be cured, or may be configured to be cured with a low degree of curing (hardness).

  In addition, the electron beam curable resin requires a large energy to be cured as compared with a photocurable resin such as an ultraviolet curable resin. Moreover, it can harden | cure, without requiring a polymerization initiator and a catalyst. Further, it is desirable to cure in an atmosphere of inert gas or the like. For this reason, while adopting a conventional photocurable resin as the first curable resin component, a resin that does not cure under conditions for curing the conventional photocurable resin can be used as the second curable resin component. .

  The electron beam can be generated by a known electron beam irradiation apparatus. The electron beam irradiation apparatus artificially accelerates electrons and applies them to an object, and can supply a large amount of energy to the object and cause a crosslinking reaction of the resin composition. The intensity | strength of the said electron beam can be set according to a structure, form, etc. of the resin composition used as object. By performing the electron beam curing process on the region where high temperature acts before the solder reflow processing for mounting the electronic component on the printed wiring board, it becomes possible to impart high heat resistance to the region. Therefore, the problem that the protective film peels off from the wiring pattern surface or the reinforcing plate can be solved. That is, in the flexible printed wiring board, high flexibility can be secured in a required region, and heat resistance can be secured in a region where high temperature acts.

  On the other hand, in a normal flexible printed wiring board, heat resistance is required in a partial region of the flexible printed wiring board, and a region where high flexibility is required is also limited. For example, in an electronic component mounting region where a high temperature acts in solder reflow processing or the like, high heat resistance is required and a reinforcing plate or the like is often laminated, and flexibility is rarely required. On the other hand, electronic parts are rarely mounted on parts that require high flexibility. Therefore, even if the region having high flexibility and the region having high heat resistance are separately provided on one flexible printed wiring board, there is little problem. Furthermore, many electron beam curable resins can be cured without requiring a curing agent or the like, and many are stable even in an uncured state. Therefore, stable performance can be maintained even if uncured resin is present in a portion where deformability is required.

  The resin composition for forming a protective film according to the present invention is laminated with a predetermined thickness on the wiring layer of the flexible printed wiring board. The method for laminating the resin composition is not particularly limited. For example, the resin composition for forming a protective film formed in a film shape can be laminated on the wiring layer of the flexible printed wiring board using a hot press or the like. Moreover, it can also comprise by apply | coating a liquid resin composition to the said wiring layer by predetermined thickness.

  Solder resist with high dimensional accuracy and shape accuracy in flexible printed wiring boards by masking the laminated resin composition, irradiating light such as ultraviolet rays according to the required area or wiring pattern, and then developing. A film can be formed.

  As a result, the protective film formed from the resin composition for forming a protective film according to the present invention has a function as a solder resist film having heat resistance in a predetermined area, and a cover that requires flexibility in other areas. It becomes possible to have the function of a ray film. Therefore, a process of separately laminating the coverlay film is not required, and the manufacturing process can be simplified and the product yield can be increased.

  As in the invention described in claim 3, by curing the first curable resin component, a protective film having an elastic modulus of 1 GPa or less is formed, while the first curable resin component and the first curable resin component are formed. The second curable resin component is cured to form a protective film having a modulus of elasticity of 30% or more larger than that of the protective film formed by curing the first curable resin component. It is desirable to do.

  When the first curable resin component is cured, the deformability of the cured product can be secured by setting so that a cured product having an elastic modulus of 1 GPa or less is formed. Therefore, high flexibility can be ensured when applied to a flexible printed wiring board.

  On the other hand, the heat resistance required for the protective film formed by the resin composition according to the present invention can be set according to the temperature at which it acts and the laminated form. For example, when applied to a dry film solder resist when an electronic component is connected by a solder reflow process on a printed wiring board, the interface between the dry film solder resist and the copper foil constituting the wiring pattern or a polyimide film It is set so that floating (peeling) due to voids or the like does not occur at the interface.

  When the second curable resin component is cured in addition to the first curable resin component, the elastic modulus is 30 than the protective film formed by curing the first curable resin component. It is desirable that the protective film is formed so as to be larger than%. Thereby, the shape retention property of the area | region hardened by irradiating the said electron beam increases. For this reason, when it uses as a soldering resist film in a flexible printed wiring board, it becomes difficult to produce peeling etc. by heating, and it becomes possible to ensure high heat resistance.

  The kind and mixture ratio of the photocurable resin component and / or thermosetting resin component and the electron beam curable resin component are not particularly limited. Moreover, required flexibility and heat resistance can be set by adjusting the kind and mixture ratio of the said photocurable resin component and thermosetting resin component, and an electron beam curable resin component.

  As the invention described in claim 4, as the first curable resin component, for example, a resin component constituting a dry film solder resist can be adopted. For example, a urethane acrylate resin component or an epoxy acrylate resin component can be employed. Moreover, the hardening in a photocuring process and the hardening in a thermosetting process can be accelerated | stimulated by adding a photocuring accelerator and a thermosetting accelerator. On the other hand, what contains the radical polymerization initiator by electron beam irradiation as an electron beam curable resin component is also employable.

  When a urethane acrylate resin is employed as the photocurable resin component and the thermosetting resin component, resin components such as polyether (polypropylene glycol), polycarbonate polyol, and polyester diol can be employed as the soft segment. As the hard segment, aromatic isocyanate (tolylene diisocyanate), alicyclic isocyanate (isophorone diisocyanate, hydrogenated xylylene diisocyanate), aliphatic isocyanate (hexamethylene diisocyanate) and the like can be employed. Moreover, resin components such as hydroxyethyl, hydroxypropyl, hydroxybutyl acrylate and its ε-caprolactone adduct, glycerin diacrylate, and pentaerythritol triacrylate can be employed as the cross-linking portion.

  When an epoxy acrylate resin is used as the photocurable resin component and the thermosetting resin component, the phenol novolac type epoxy resin, bisphenol A type epoxy resin, glycerol polyglycidyl ether, 1,6 hexane glycidyl ether is used as the epoxy component. A resin component such as can be used. Moreover, resin components, such as acrylic acid, methacrylic acid, acrylic acid dimer, acrylic acid + lactone, can be employed as the acrylic component.

  When a photocurable resin is employed as the first curable resin component, a photocuring accelerator (photocuring initiator) or the like can be included as necessary. Moreover, when employ | adopting a thermosetting accelerator as a 1st curable resin component, a catalyst and a polymerization accelerator can be included.

  Moreover, when employ | adopting an electron beam curable resin component as a 2nd curable resin component, a radical polymerization initiator etc. can also be mix | blended as needed. For example, α-diketones such as benzyl and diacetyl; acyloins such as benzoin; acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; thioxanthone, 2,4-diethylthioxanthone, thioxanthone-4-sulfone Benzophenones such as acid, benzophenone, 4,4 · -bis (dimethylamino) benzophenone, 4,4 · -bis (diethylamino) benzophenone; acetophenone, p-dimethylaminoacetophenone, α, α-dimethoxy-α-acetoxybenzophenone, Acetophenones other than the above compounds such as α, α-dimethoxy-α-phenylacetophenone and p-methoxyacetophenone; quinones such as anthraquinone and 1,4-naphthoquinone; phenacyl Roratsuido, tribromomethylphenylsulfone, tris (trichloromethyl) -s-halogen compounds such as triazine; peroxides such as di -tert- butyl peroxide or the like can be employed.

  The protective film-forming resin composition according to the present invention can constitute various forms of protective films on a flexible printed wiring board.

  That is, a dry film solder resist containing the protective film-forming resin composition according to any one of claims 1 to 4 can be configured as in the invention described in claim 5.

  Moreover, the coverlay film containing the resin composition for protective film formation in any one of Claims 1-4 can be comprised like the invention described in Claim 6.

  The resin composition for forming a protective film according to the present invention is subjected to a photocuring step and a heat curing step, and then the electron beam curing step is performed by irradiating an electron beam to a required region. A region having high heat resistance and a region ensuring heat resistance can be provided. For example, as in the invention described in claim 7, a flexible print including a first region provided with a protective film having a required deformability and a second region provided with a protective film having a required heat resistance A wiring board can be constructed.

  In the flexible printed wiring board according to the present invention, as in the invention described in claim 8, in the first region, the first curable resin component is mainly cured, and the second In the region, the first curable resin component and the second curable resin component are cured. By adopting this configuration, a flexible printed wiring board having both flexibility and heat resistance can be obtained.

  Invention of Claim 9 is the manufacturing method of the flexible printed wiring board described in Claim 7 or Claim 8, Comprising: The lamination process of laminating | stacking the resin composition for protective film formation on a flexible printed wiring board, In the first curing step, in which the first curable resin component is primarily cured to cure the protective film-forming resin composition until it has the required deformability, and in the second region, the second mainly. And a second curing step of curing the protective film-forming resin composition until it has the required heat resistance.

  As described in claim 10, a photocuring step and / or a heat curing step can be adopted as the first curing step, and an electron beam curing step can be adopted as the second curing step.

  For example, the photocuring step is performed by irradiating a predetermined region with ultraviolet rays or the like corresponding to the wiring pattern. Then, by performing a development process, masking is performed to dissolve and remove a portion that has not been irradiated with ultraviolet rays, and a highly accurate solder resist film can be formed. Thereafter, a thermosetting process is performed to cure the thermosetting resin component and stabilize the resist film. At this stage, the electron beam curable resin component is not cured, and the flexibility of the flexible printed wiring board can be ensured.

  On the other hand, heat resistance with respect to the solder reflow process performed in order to mount an electronic component is not enough only by finishing the said heat curing process. For this reason, in this invention, the electron beam hardening process which irradiates an electron beam to the area | region where high temperature acts, and hardens an electron beam curable resin component is performed. By performing the electron beam curing step, the elastic modulus of the solder resist film is further increased. This makes it possible to ensure heat resistance in the solder reflow process.

  A flexible printed wiring board can be formed that can ensure flexibility and has high heat resistance in a required region.

It is a disassembled sectional view which shows the state which laminated | stacked the protective film and reinforcement board as a dry film solder resist on the double-sided flexible printed wiring board in which the wiring pattern was formed. It is a flowchart which shows the outline of the manufacturing process of the flexible printed wiring board which concerns on this invention. It is a top view which shows typically the state of the protective film before hardening laminated | stacked on the printed wiring board shown in FIG. It is a top view which shows typically the state which hardened the photocurable resin component and the thermosetting resin component of the predetermined area | region of the protective film of FIG. It is a top view which shows typically the state which developed and removed the protective film of the area | region which has not irradiated the ultraviolet-ray. It is a top view which shows typically the state after irradiating an electron beam to a predetermined area | region and performing an electron beam hardening process, after hardening a photocurable resin and a thermosetting resin. It is a top view which shows typically the state which mounted the electronic component in the area | region which removed the protective film. It is sectional drawing which follows the VIII-VIII line of the flexible printed wiring board shown in FIG.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In the present embodiment, the protective film-forming resin composition according to the present invention is applied to the solder resist film of the double-sided flexible printed wiring board 1.

  FIG. 1 is an exploded cross-sectional view showing each member when a flexible printed wiring board 1 is formed using the protective film-forming resin composition according to the present invention.

  A flexible printed wiring board 1 according to the present invention is formed by forming a wiring pattern on an insulating film-like substrate 2 and a copper foil laminated on both surfaces of the film-like substrate 2 via an adhesive layer (not shown). The wiring layers 3 and 4 are configured.

  Solder resist layers (DFSR layers) 5 and 6 formed from the protective film-forming resin composition according to the present invention are laminated on the wiring layers 3 and 4. Further, a reinforcing plate 7 formed of a stainless steel sheet is laminated via the solder resist layer 6 on the side where no electronic component is mounted.

  A manufacturing process of the flexible printed wiring board 1 according to the present embodiment will be described with reference to FIGS.

  First, the flexible printed wiring board 1 provided with the wiring layers 3 and 4 in which the wiring pattern shown in FIG. 1 is formed is prepared (S101). The solder resist layers 5 and 6 are formed on the wiring layers 3 and 4 (S102).

  The solder resist layers 5 and 6 can be provided by laminating the resin composition according to the present invention on the wiring layers 3 and 4. For example, the solder resist layers 5 and 6 can be provided by laminating a film (DFSR) formed from the resin composition on the wiring layers 3 and 4 using a hot press or the like. Alternatively, the solder resist layers 5 and 6 may be provided by applying the liquid resin composition on the wiring layers 3 and 4 with a predetermined thickness and drying.

  The resin composition constituting the solder resist layers 5 and 6 according to this embodiment includes a first curable resin component containing a photocurable resin and a thermosetting resin, and a second containing an electron beam curable resin. It is composed of a curable resin component. By curing the photocurable resin component and the thermosetting resin component, a cured product having an elastic modulus that can exhibit the required deformability is formed, while by curing all the curable resin components, A cured product having an elastic modulus capable of exhibiting required heat resistance is formed.

  The said photocurable resin component and the said thermosetting resin component which concern on this embodiment can be comprised including a urethane acrylate resin component or an epoxy acrylate resin component.

  When the urethane acrylate resin component is used as the photo-curable resin component and the thermosetting resin component, a resin component such as polyether (polypropylene glycol), polycarbonate polyol, polyester diol, etc. should be used as the soft segment. Can do. As the hard segment, aromatic isocyanate (tolylene diisocyanate), alicyclic isocyanate (isophorone diisocyanate, hydrogenated xylylene diisocyanate), aliphatic isocyanate (hexamethylene diisocyanate) and the like can be employed. Moreover, resin components such as hydroxyethyl, hydroxypropyl, hydroxybutyl acrylate and its ε-caprolactone adduct, glycerin diacrylate, and pentaerythritol triacrylate can be employed as the cross-linking portion.

  When an epoxy acrylate resin is used as the photocurable resin and the thermosetting resin, the epoxy component includes phenol novolac type epoxy resin, bisphenol A type epoxy resin, glycerol polyglycidyl ether, 1,6 hexane glycidyl ether, etc. Resin component can be used. Moreover, resin components, such as acrylic acid, methacrylic acid, acrylic acid dimer, acrylic acid + lactone, can be employed as the acrylic component.

  In addition, a photocuring accelerator (photocuring initiator) can be mix | blended as a photocurable resin component. Moreover, the catalyst etc. which accelerate thermosetting can be mix | blended as a thermosetting resin component.

  As said electron beam curable resin, various resin hardened | cured with an electron beam is employable. The electron beam curable resin is not limited to a resin that can be cured only by an electron beam. Any material that does not cure in the step of curing the photocurable resin and the thermosetting resin but cures by irradiation with an electron beam is sufficient. For example, the second curable resin is blended with a conventional photocurable resin that is not completely cured by ultraviolet irradiation and a thermosetting resin having a higher curing temperature than the thermosetting resin contained in the first curable resin component. A resin component can be constituted.

  In addition, in order to harden the said 2nd curable resin component completely with an electron beam, a radical polymerization initiator can be mix | blended. For example, as radical polymerization initiators, α-diketones such as benzyl and diacetyl; acyloins such as benzoin; acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; thioxanthone, 2,4-diethylthioxanthone Benzophenones such as thioxanthone-4-sulfonic acid, benzophenone, 4,4 · -bis (dimethylamino) benzophenone, 4,4 · -bis (diethylamino) benzophenone; acetophenone, p-dimethylaminoacetophenone, α, α-dimethoxy Acetophenones other than the above compounds such as -α-acetoxybenzophenone, α, α-dimethoxy-α-phenylacetophenone, p-methoxyacetophenone; anthraquinone, 1,4-naphthoquino Quinones and the like; phenacyl Crowlers Tsui de, tribromomethylphenylsulfone, tris halogen compounds such as (trichloromethyl) -s-triazine; may be employed peroxides such as di -tert- butyl peroxide.

  After the film-like resin composition (DFSR) formed by blending the curable resin component is laminated on the wiring layers 3 and 4 of the flexible printed wiring board 1, masking is performed on the regions 11 and 11 where the wiring layer is exposed. The photocuring step is performed by exposing the whole to ultraviolet rays (S103). In the present embodiment, as shown in FIG. 4, regions other than the masking regions 11 and 11 are cured.

  After the photocuring step (S103), development is performed (S104), and the resin composition in the regions 11 and 11 subjected to the masking is dissolved and removed. Thereby, as shown in FIG. 5, the opening parts 12 and 12 from which the electrode parts 8 and 8 to which the electronic components are connected are exposed are formed. In the present embodiment, the solder resist layer 6 on the side opposite to the side where the openings 12 and 12 for connecting the electronic components are formed is irradiated with ultraviolet rays to cure the photocurable resin, and the wiring layer 4. It is configured to function as a coverlay film that protects the camera.

  Next, the stainless steel reinforcing plate 7 is laminated and bonded to the region opposite to the side where the openings 12 and 12 are formed via an adhesive (not shown). By providing the reinforcing plate 7, the rigidity of the electronic component mounting area can be increased. The reinforcing plate 7 can be laminated after the electron beam curing step described later.

  After laminating the reinforcing plate 7, a heat curing step (S106) for curing the thermosetting resin component is performed. In the heat curing step, the electron beam curable resin component is set so as not to cure or to increase the degree of curing. For this reason, a protective film having a large deformability can be formed as compared with a protective film formed from a thermosetting resin component and an ultraviolet curable resin component. This stabilizes the ultraviolet curable resin component and the thermosetting resin component of the solder resist layers 5 and 6 and adjusts the elastic modulus of the solder resist layers 5 and 6. In this embodiment, the compounding component of the said curable resin is adjusted so that the elasticity modulus after performing the said heat-hardening process may be 1 GPa or less. By setting the elastic modulus of the solder resist layers 5 and 6 to 1 GPa or less, it is possible to ensure the flexibility of the flexible printed wiring board 1.

  Next, as shown in FIG. 6, an electron beam curing step of irradiating an electron beam to the rectangular regions 5b and 6b around the openings 12 and 12 to which the electronic components are connected to cure the electron beam curable resin component. Is performed (S107). The region 5b is a region where high temperature acts in the component mounting process (S108) by solder reflow. If the photocurable resin component and the thermosetting resin component are merely cured, the solder resist layers 5 and 6 may be lifted from the wiring layers 3 and 4 and the reinforcing plate 7.

  In this embodiment, when the lead-free solder is reflowed to connect the electronic component, a void is generated at the interface between the solder resist layers 5 and 6 and the wiring layers 3 and 4, and the solder resist layer 5 The heat resistance of the solder resist layer is set so as to have a heat resistance that does not lift up. For example, each curable resin component is added so that a protective film having an elastic modulus of 30% or more larger than that of the protective film after the heat curing process is formed in the region subjected to the electron beam curing process. It is desirable to adjust.

  In the component mounting step S108, the electronic component 10 is positioned and placed via the solder 9 applied on the electrode portions 8 and 8 exposed in the opening 12, and the electron beam curable resin is cured. This is done by heating the regions 5b, 6b. As shown in FIGS. 7 and 8, in the flexible printed wiring board 1 after the component mounting step (S108), the solder resist layers 5 and 6 in the rectangular areas 5b and 6b set so as to surround the electronic component 10 are formed. The elastic modulus is larger than the elastic modulus of the regions 5a and 6a outside the rectangular regions 5b and 6b. For this reason, the shape retaining property of the flexible printed wiring board 1 in the vicinity of the portion where the electronic component 10 is connected is improved, and the electronic component can be reliably held.

  On the other hand, other areas 5a. Since the elastic modulus of the solder resist layer in 6a is 1 GPa or less, the flexibility of the flexible printed wiring board 1 can be ensured.

  Moreover, the function of a coverlay film can be provided without removing the solder resist layers 5 and 6. For this reason, the process of laminating a coverlay film becomes unnecessary, and the manufacturing process can be simplified. It is also possible to increase the product yield.

  The scope of the present invention is not limited to the embodiment described above. The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not by the above-mentioned meaning but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  A flexible printed wiring board having high heat resistance and high flexibility can be manufactured.

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 2 Film-like base material 3 Wiring layer 4 Wiring layer 5 Solder resist layer 6 Solder resist layer 7 Reinforcement plate

Claims (10)

A protective film-forming resin composition for forming a protective film of a flexible printed wiring board,
While comprising a first curable resin component and a second curable resin component having different curing conditions or curing characteristics,
A protective film having a required deformability is formed by mainly curing the first curable resin component,
A protective film-forming resin composition in which a protective film having required heat resistance is formed by curing the first curable resin component and the second curable resin component. A first curable resin component which is cured by applying light or / and heat and exerts the required deformability on the protective film;
The resin composition for forming a protective film according to claim 1, comprising a second curable resin component which is cured by applying an electron beam and exhibits the required heat resistance of the protective film. object. While curing the first curable resin component, a protective film having an elastic modulus of 1 GPa or less is formed,
The elastic modulus is 30% or more than the protective film formed by curing the first curable resin component by curing the first curable resin component and the second curable resin component. The resin composition for forming a protective film according to claim 1, wherein a large protective film is formed. While the first curable resin component includes a urethane acrylate resin component or an epoxy acrylate resin component,
The resin composition for protective film formation of any one of Claims 1-3 in which the said 2nd curable resin component contains the radical polymerization initiator by electron beam irradiation.   The photosensitive dry film soldering resist which has the said resin composition for protective film formation of any one of Claims 1-4.   The coverlay film which has the resin composition for protective film formation of any one of Claims 1-5. A flexible printed wiring board having a protective film formed from the protective film-forming resin composition according to any one of claims 1 to 5,
A first region provided with a protective film having a required deformability;
A flexible printed wiring board comprising: a second region provided with a protective film having required heat resistance. In the first region, the first curable resin component is mainly cured,
The flexible printed wiring board according to claim 7, wherein the first curable resin component and the second curable resin component are cured in the second region. A method for producing a flexible printed wiring board according to claim 7 or claim 8,
A laminating step of laminating a protective film-forming resin composition on a flexible printed wiring board;
A first curing step of curing the protective film-forming resin composition until it has the required deformability by mainly curing the first curable resin component;
A flexible print comprising: a second curing step in which, in the second region, the second curable resin component is mainly cured to cure the protective film-forming resin composition until it has a required heat resistance. A method for manufacturing a wiring board. The first curing step is a photocuring step and / or a thermosetting step,
The method for manufacturing a flexible printed wiring board according to claim 9, wherein the second curing step is an electron beam curing step.

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