HK40036487A - Adhesive film for printed wiring board - Google Patents

Description

Adhesive film for printed circuit substrate

Technical Field

The present application relates to a film for a printed wiring board, an electromagnetic wave shielding film, and a shielded wiring board.

Background

In order to protect an electronic circuit from electromagnetic noise, an electromagnetic wave shielding film attached to a printed circuit board base material is used. The electromagnetic wave shielding film comprises a conductive adhesive layer and an insulating protective layer, and is bonded to the grounding circuit of the printed circuit substrate through the conductive adhesive layer and is conducted.

The insulating protective layer may contain a colorant for the purpose of improving the appearance and visibility of printed matter. For example, in patent document 1, an insulating protective layer containing a black colorant is used to improve the visibility of printing.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2016-143751.

Disclosure of Invention

Technical problem to be solved by the invention

The printed circuit substrate comprises a base layer, a circuit pattern formed on the base layer and composed of copper foil, and a covering film for protecting the circuit pattern. By attaching the electromagnetic wave shielding film to the printed wiring substrate, the effect of covering the circuit pattern of the printed wiring substrate which cannot be visually recognized from the outside can also be expected. In recent years, it has been desired that the printed wiring substrate and the cover film are thin. When the cover film is thin, projections reflecting the circuit pattern are likely to be formed on the surface of the cover film. The present inventors have found that a conventional electromagnetic wave shielding film cannot sufficiently cover a circuit pattern if the cover film is thin and the height of the projection is high.

Further, the electromagnetic wave shielding function is not required, but the circuit pattern may be required to have a covering property.

The present application addresses the problem of achieving an electromagnetic wave shielding film or a printed circuit board substrate adhesive film that has good circuit pattern coverage even when the cover film is thin.

Means for solving the problems

The sticking film for a printed wiring substrate according to one aspect of the present invention includes an adhesive layer and an insulating protective layer, and a load area ratio (Smr 2) between a separation protrusion valley portion and a central portion of the insulating protective layer is 91% or less.

In one technical form of the adhesive film for a printed wiring substrate, the height (Svk) of the projecting valley portion of the insulating protective layer can be 0.45 μm or more.

In one embodiment of the adhesive film for a printed wiring board base material, the adhesive layer can have conductivity and functions as an electromagnetic wave shielding film. In this case, a shielding layer may be further included between the adhesive layer and the insulating protective layer.

The technical form of the shielding circuit substrate of the present application includes: a circuit substrate including a base layer, a circuit pattern provided on the base layer, and an insulating film bonded to the base layer so as to cover the circuit pattern; the electromagnetic wave shielding film of the present application is bonded to an insulating film.

Effects of the invention

According to the electromagnetic wave shielding film and the adhesive film for a printed wiring substrate of the present application, the covering property of a circuit pattern can be greatly improved even when the cover film is thin.

Drawings

FIG. 1 is a sectional view of a film for a printed wiring board according to an embodiment;

FIG. 2 is a sectional view of a shield circuit substrate according to an embodiment;

FIG. 3 is a plan view of a printed wiring board used for evaluation of coverability;

FIG. 4 is a photograph showing the observation result of a confocal microscope.

Detailed Description

The adhesive film for a printed wiring substrate according to the present embodiment is an electromagnetic wave shielding film 101 having an electromagnetic wave shielding function, and as shown in fig. 1, includes a conductive adhesive layer 111 and an insulating protective layer 112, and the ratio of the load area (Smr 2) between the protruding valley portions and the central portion of the insulating protective layer 112 is 91% or less, preferably 90% or less. In fig. 1, the conductive shield layer 113 is provided between the conductive adhesive layer 111 and the insulating protective layer 112, but when the conductive adhesive layer 111 also functions as a shield layer, the shield layer 113 may not be provided.

The electromagnetic wave shielding film 101 of the present embodiment is bonded to the printed wiring substrate 102 as shown in fig. 2. The printed wiring board 102 includes, for example, a base layer 121, a circuit pattern 122 provided on a surface of the base layer 121, and an insulating film 124 bonded to the base layer 121 via an adhesive layer 123 so as to cover the circuit pattern 122.

The base layer 121 is made of an insulating material. As the insulating material, an insulating resin composition, ceramics, or the like can be used. For example, at least one selected from the group consisting of polyimide resins, polyamide resins, polyetherimide resins, polyester imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide amide resins, polyetherimide resins, and polyphenylene sulfide resins can be used as the insulating resin composition.

The circuit pattern 122 is made of a conductive material. As the conductive material, a metal foil or a conductive material obtained by printing and curing a mixture of a conductive filler and a resin composition can be used, and a copper foil is preferably used from the viewpoint of cost.

The thickness of the circuit pattern 122 is not particularly limited, but is preferably 1 to 100 μm, and more preferably 1 to 50 μm. The thickness of the circuit pattern is 1 μm or more, which can reduce the manufacturing cost of the printed wiring substrate 102. The thickness of the printed wiring substrate 102 can be reduced to 100 μm or less.

The adhesive layer 123 is made of an insulating material. The insulating material is preferably an insulating resin composition, and for example, at least one selected from polyimide resins, polyamide-imide resins, polyamide resins, polyether imide resins, polyester-imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide-amide resins, polyether-imide resins, and polyphenylene sulfide resins can be used.

The thickness of the adhesive layer 123 is not particularly limited, but is preferably 1 μm to 50 μm.

The insulating film 124 is made of an insulating material. The insulating material is preferably an insulating resin composition, and for example, at least one selected from polyimide resins, polyamide-imide resins, polyamide resins, polyether imide resins, polyester-imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide-amide resins, polyether-imide resins, and polyphenylene sulfide resins can be used.

The thickness of the insulating film 124 is not particularly limited, but is preferably 1 μm to 100 μm, and more preferably 10 μm to 25 μm. A thickness of 1 μm or more can reduce the manufacturing cost of the printed wiring substrate 102. The thickness of the printed wiring substrate 102 can be reduced to 100 μm or less.

When the electromagnetic wave shielding film 101 is opaque by coloring the insulating protective layer 112, the circuit pattern 122 cannot be directly recognized by the naked eye. For example, if the circuit pattern 122 is covered with a film having a total light transmittance of preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less, the circuit pattern 122 can hardly be directly recognized with the naked eye. However, due to the circuit pattern 122, unevenness is formed on the surface of the insulating protective layer 112. The general circuit pattern 122 is formed of copper wires and has a height of several μm to tens of μm. Since the difference in height between the portion where the wire exists and the portion where the wire does not exist is reduced by the embedding of the adhesive layer 123 and the conductive adhesive layer 111, the height of the unevenness generated on the surface of the insulating protective layer 112 is several μm. However, even with such minute irregularities, the presence of the irregularities can be visually recognized on the glossy surface that reflects light easily, and the circuit pattern 122 cannot be covered.

Therefore, in order to cover the circuit pattern 122, the glossiness of the surface of the insulating protective layer 112 may be reduced. However, the inventors of the present application found that the hiding property of the circuit pattern was not related to the 85 ° gloss. The glossiness is largely affected by the surface roughness, but the inventors of the present invention have found that the hiding property of the circuit pattern is not related to the three-dimensional arithmetic average height (Sa) based on international organization for standardization (ISO) 25178, which is an index of general surface roughness.

On the other hand, the inventors of the present invention have found that the covering property of the circuit pattern is well correlated with the load area ratio (Smr 2) between the separated projected valley portions and the central portion based on international organization for standardization (ISO) 25178, and that the covering property of the circuit pattern is excellent when Smr2 is 91% or less, preferably 90% or less. This is because the presence of valley portions deviated from the central portion to some extent makes the incident light more easily scattered. Further, Smr2 is preferably 70% or more, more preferably 80% or more, and still more preferably 85%. When Smr2 is 70% or more, the ratio of valleys is small, surface reflection at the valleys can be suppressed, and hiding properties can be improved.

Since the deeper the projected valley, the more easily the incident light is scattered, the projected valley height Svk based on international organization for standardization (ISO) 25178 is preferably 0.45 μm or more, more preferably 0.49 μm or more, further preferably 0.60 μm or more, and further preferably 0.70 μm or more. Svk is preferably 3.0 μm or less, more preferably 2.0 μm or less, still more preferably 1.5 μm or less, and yet more preferably 1.0 μm or less. When Svk is 3.0 μm or less, the shape of the surface of the releasable substrate provided with the uneven shape is transferred to the insulating protective layer to produce an insulating protective layer having an uneven shape, the releasability of the releasable substrate from the insulating protective layer is good.

Fine particles may be added to the resin forming the insulating protective layer 112 so that Smr2 in the insulating protective layer 112 is 91% or less.

The fine particles added to the insulating protective layer 112 are not particularly limited, and for example, resin fine particles or inorganic fine particles can be used. The resin fine particles may be acrylic resin fine particles, polyacrylonitrile fine particles, polyurethane fine particles, polyamide fine particles, polyimide fine particles, or the like. The inorganic fine particles may be calcium carbonate fine particles, calcium silicate fine particles, clay, china clay, talc, silica fine particles, glass fine particles, diatomaceous earth, mica powder, alumina fine particles, magnesium oxide fine particles, zinc oxide fine particles, barium sulfate fine particles, aluminum sulfate fine particles, calcium sulfate fine particles, magnesium carbonate fine particles, or the like. These resin fine particles and inorganic fine particles can be used alone or in combination of plural ones.

In order to make Smr2 of the insulating protective layer 112 91% or less, it is preferable to provide unevenness on the surface. Examples of a method for providing the surface with the irregularities include the following methods: the surface of the releasable substrate provided with the irregular shape by embossing or the like is coated with a resin composition for the insulating protective layer 112 and dried, so that the irregular shape of the releasable substrate is transferred to the insulating protective layer 112. Instead of embossing, a film having a matte layer with irregularities on the surface thereof may be used as a release substrate. The matte layer can be formed by applying a resin composition containing fine particles to the surface of the film or embossing the resin layer formed on the surface of the film.

In addition to the use of a releasable substrate having irregularities, known methods include a method in which a resin composition containing fine particles is applied to the surface of a shield layer and dried to form an insulating protective layer 112 having irregularities, a method in which dry ice or the like is sprayed onto the surface of the insulating protective layer 112, and a method in which a curable composition having irregularities is applied to the surface of the shield layer, then a mold having the irregularities is pressed, the curable composition layer is cured, and the mold is released.

Further, a black colorant such as a black pigment or a mixed pigment obtained by subtractive mixing of a plurality of pigments and blackening is preferably applied to the insulating protective layer 112. The black pigment may be any one of carbon black, Ketjen black (Ketjen black), Carbon Nanotube (CNT), perylene black, titanium black, iron black, aniline black, and the like, or a combination thereof. The mixed pigment can be, for example, red, green, blue, yellow, violet, cyan, magenta, or the like.

The resin component constituting the insulating protective layer 112 can be, for example, a thermoplastic resin, a thermosetting resin, an active energy ray-curable resin, or the like.

The thermoplastic resin is not particularly limited, and a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, an imide resin, an acrylic resin, or the like can be used. The thermosetting resin is not particularly limited, and a phenol resin, an epoxy resin, a polyurethane resin, a melamine resin, a polyamide resin, an alkyd resin, or the like can be used. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least 2 (meth) acryloyloxy groups in the molecule, or the like can be used. The insulating protective layer 112 may be formed of a single material, or may be formed of 2 or more materials. The insulating protective layer 112 may be a laminate of 2 or more layers having different physical and chemical properties such as material, hardness, elastic modulus, and the like. In this case, Smr2 or the like on the surface of the uppermost layer may be controlled to be a predetermined value.

The insulating and protecting layer 112 may contain at least one of a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity improver, an anti-blocking agent, and the like, as necessary.

The thickness of the insulating protective layer 112 is not particularly limited, and may be appropriately set as needed, and is preferably 1 μm or more, more preferably 4 μm or more, preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less. The conductive adhesive layer 111 and the shield layer 113 can be sufficiently protected by setting the thickness of the insulating protective layer 112 to 1 μm or more. The thickness of the insulating protective layer 112 is 20 μm or less, and flexibility of the electromagnetic wave shielding film 101 can be ensured, so that the electromagnetic wave shielding film 101 can be easily applied to a member requiring flexibility.

If the shield layer 113 is provided, the shield layer 113 can be formed of a metal foil, a vapor deposited film, a conductive filler, or the like.

The metal foil is not particularly limited, and may be any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like, or a foil made of an alloy containing two or more of these metals.

The thickness of the metal foil is not particularly limited, but is preferably 0.5 μm or more, and more preferably 1.0 μm or more. When the thickness of the metal foil is 0.5 μm or more, the attenuation of a high-frequency signal can be suppressed when the high-frequency signal of 10MHz to 100GHz is transmitted to the shield printed wiring substrate. The thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, and still more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, a good elongation at break can be secured.

The vapor-deposited film is not particularly limited, and can be formed by vapor-depositing nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. The vapor deposition can be performed by an electroplating method, an electroless plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a Chemical Vapor Deposition (CVD) method, a metal organic vapor deposition (MOCVD) method, or the like.

The thickness of the vapor deposited film is not particularly limited, but is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the thickness of the deposited film is 0.05 μm or more, the electromagnetic wave shielding film of the substrate for shielding a printed wiring is excellent in the electromagnetic wave shielding property. The thickness of the vapor deposited film is preferably less than 0.5. mu.m, more preferably less than 0.3. mu.m. When the thickness of the deposited film is less than 0.5. mu.m, the electromagnetic wave shielding film is excellent in flexibility and the damage of the shielding layer due to the difference in height provided on the printed wiring substrate can be suppressed.

If the conductive filler is used, the shielding layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the insulating protective layer 112 and drying the applied solvent. As the conductive filler, a metal-coated resin filler, a carbon-based filler, or a mixture thereof can be used. The metal filler may be copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, or the like. These metal powders can be produced by electrolytic methods, atomization methods, and reduction methods. Examples of the shape of the metal powder include spherical, flaky, fibrous, and dendritic shapes.

In the present embodiment, the thickness of the shield layer 113 may be appropriately selected depending on the desired electromagnetic shielding effect and repeated bending resistance and seed slip property, and if a metal foil is used, it is preferably 12 μm or less from the viewpoint of securing elongation at break.

In the present embodiment, the conductive adhesive layer 111 contains a conductive filler and at least one of a thermoplastic resin, a thermosetting resin, and an active energy ray-curable resin.

When the conductive adhesive layer 111 contains a thermoplastic resin, examples of the thermoplastic resin include styrene resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, imide resin, and acrylic resin. These resins may be used alone in 1 kind or in combination of 2 or more kinds.

When the conductive adhesive layer 111 contains a thermosetting resin, examples of the thermosetting resin include phenol resins, epoxy resins, polyurethane resins, melamine resins, polyamide resins, polyimide resins, alkyd resins, and the like. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least 2 (meth) acryloyloxy groups in the molecule, or the like can be used. These resins may be used alone in 1 kind or in combination of 2 or more kinds.

The thermosetting resin includes, for example, a 1 st resin component containing a 1 st reactive functional group and a 2 nd resin component in which the 1 st functional group is reacted. The 1 st functional group can be, for example, an epoxy group, an amide group, a hydroxyl group, or the like. The 2 nd functional group may be selected according to the 1 st functional group, and for example, when the 1 st functional group is an epoxy group, the 2 nd functional group may be a hydroxyl group, a carboxyl group, an epoxy group, an amino group, or the like. Specifically, for example, when the 1 st resin component is an epoxy resin, the 2 nd resin component can use an epoxy-modified polyester resin, an epoxy-modified polyamide resin, an epoxy-modified acrylic resin, an epoxy-modified polyurethane polyurea resin, a carboxyl-modified polyester resin, a carboxyl-modified polyamide resin, a carboxyl-modified acrylic resin, a carboxyl-modified polyurethane polyurea resin, a polyurethane-modified polyester resin, or the like. Among them, carboxyl-modified polyester resins, carboxyl-modified polyamide resins, carboxyl-modified polyurethane polyurea resins, and polyurethane-modified polyester resins are preferable. When the 1 st resin component is a hydroxyl group, the 2 nd resin component can be an epoxy-modified polyester resin, an epoxy-modified polyamide resin, an epoxy-modified acrylic resin, an epoxy-modified polyurethane polyurea resin, a carboxyl-modified polyester resin, a carboxyl-modified polyamide resin, a carboxyl-modified acrylic resin, a carboxyl-modified polyurethane polyurea resin, a polyurethane-modified polyester resin, or the like. Among them, carboxyl-modified polyester resins, carboxyl-modified polyamide resins, carboxyl-modified polyurethane polyurea resins, and polyurethane-modified polyester resins are preferable.

The thermosetting resin may also contain a curing agent that promotes the thermosetting reaction. When the thermosetting resin contains the 1 st functional group and the 2 nd functional group, the curing agent can be appropriately selected depending on the kinds of the 1 st functional group and the 2 nd functional group. When the 1 st functional group is an epoxy group and the 2 nd functional group is a hydroxyl group, an imidazole-based curing agent, a phenol-based curing agent, a cationic curing agent, or the like can be used. The above-mentioned substances can be used alone in 1 kind, or in combination of 2 or more kinds. Other optional components may also include defoaming agents, antioxidants, viscosity modifiers, diluents, anti-settling agents, leveling agents, coupling agents, colorants, flame retardants, and the like.

The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon-based filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders can be produced by an electrolytic method, an atomization method, a reduction method, or the like. Among them, any of silver powder, silver-coated copper powder, and copper powder is preferable.

From the viewpoint of contact between the fillers, the average particle diameter of the conductive filler is preferably 1 μm or more, more preferably 3 μm or more, preferably 50 μm or less, more preferably 40 μm or less. The shape of the conductive filler is not particularly limited, and may be spherical, flaky, dendritic, fibrous, or the like.

The content of the conductive filler can be appropriately selected depending on the application, and is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 95% by mass or less, and more preferably 90% by mass or less in the total solid content. From the viewpoint of embeddability, it is preferably 70% by mass or less, and more preferably 60% by mass or less. In order to realize anisotropic conductivity, it is preferably 40% by mass or less, and more preferably 35% by mass or less.

From the viewpoint of embeddability, the thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm.

The conductive adhesive layer 111 may be a so-called adhesive layer having adhesiveness in an environment at normal temperature (for example, 20 ℃). The conductive adhesive layer 111 has adhesiveness in a normal temperature environment, and can easily attach the electromagnetic wave shielding film 101 to any position of the printed wiring substrate 102.

When the electromagnetic wave shielding film 101 includes the shielding layer 113 made of a metal foil or the like, the total light transmittance is usually almost 0. When the shielding layer 113 is not provided, the total light transmittance may be adjusted to be preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less by adjusting the amount of a colorant, a filler, or the like added to the insulating protective layer 112 and/or the conductive adhesive layer 111. The total light transmittance is 20% or less, so that it is difficult to visually recognize the circuit pattern 122 directly when the electromagnetic wave-shielding film 101 is attached to the printed wiring substrate 102. The total light transmittance can be measured in accordance with JIS K7136.

In the present embodiment, an example is shown in which the adhesive film for a printed wiring substrate is an electromagnetic wave shielding film, and it may be an adhesive film for a printed wiring substrate having no electromagnetic wave shielding function. In this case, a nonconductive adhesive layer containing no conductive filler can be used instead of the conductive adhesive layer. If the electromagnetic wave shielding function is not required, the shielding layer may not be provided. However, in order to reduce the total light transmittance, a metal foil or the like may be provided between the adhesive layer and the insulating protective layer.

Examples

The printed wiring substrate-attached film of the present application will be described in detail below with reference to examples. The following examples are illustrative and are not intended to limit the invention.

< production of peelable substrate >

A surface of a polyethylene terephthalate film (hereinafter referred to as a PET film) having a thickness of 25 μm was sprayed with dry ice particles to form irregularities, and then a release layer made of melamine resin was provided, thereby obtaining a releasable substrate 1.

A matte layer composition comprising silica particles, a melamine resin and toluene was prepared, and the composition was applied to the surface of a polyethylene terephthalate film having a thickness of 25 μm using a wire bar, followed by heating and drying to obtain a releasable substrate 2 having a matte layer having a thickness of 5 μm. The particle diameter and the addition amount of the silica particles were changed, and peeled substrates 3 to 9 having different surface states were obtained in the same manner. The surface properties of the surfaces (surfaces on which the masking layers were formed) of the releasable substrates 1 to 9 are shown in table 1.

[ Table 1]

< manufacture of insulating protective layer >

A resin composition for an insulating and protective layer was prepared by adding 100 parts by mass of a bisphenol A type epoxy resin (Mitsubishi chemical corporation, jER 1256), 0.1 part by mass of a curing agent (Mitsubishi chemical corporation, ST 14), and 15 parts by mass of CARBON particles (Tokai CARBON, Toka black # 8300/F) as a black coloring agent to toluene so that the amount of the solid content was 20% by mass. The composition was applied to the surface of a releasable substrate with a wire bar, and dried by heating, to form an insulating protective layer having a thickness of 5 μm on the surface of the releasable substrate. Then, a 0.1 μm Ag deposited film was formed as a shield layer on the protective layer.

< preparation of adhesive layer >

100 parts by mass of a bisphenol A type epoxy resin (manufactured by Mitsubishi chemical corporation, jER 1256), 0.1 part by mass of a curing agent (manufactured by Mitsubishi chemical corporation, ST 14), and 30 parts by mass of a dendritic silver-coated copper powder having an average particle diameter of 15 μm were added to toluene so that the solid content became 20% by mass, and the mixture was stirred and mixed to prepare an adhesive layer composition. The obtained adhesive layer composition was applied to a PET film (hereinafter referred to as a support film) whose surface was subjected to release treatment using a wire bar, and heated and dried, thereby forming an adhesive layer having a thickness of 5 μm on the surface of the support film.

< manufacture of printed Circuit Board base Material adhesive film >

The surface of the insulating protective layer formed on the surface of the releasable substrate on the Ag deposition film side was bonded to the adhesive layer formed on the surface of the support film, and the resultant was pressed at a pressure of 5MPa using 1 pair of metal rolls heated to 100 ℃.

< production of substrate for shielded Circuit >

Using a press at temperature: 170 ℃ and time: 3 minutes, pressure: and (3) bonding the obtained printed circuit base material attaching film and the printed circuit base material under the condition of 2-3 MPa, and peeling off the strippable substrate to obtain the shielding circuit base material.

The printed wiring board is produced by forming a circuit pattern 122 shown in fig. 4 on a base layer 121 made of a polyimide film. The circuit pattern 122 was formed of a copper foil having a line width of 0.1mm and a height of 12 μm. An adhesive layer having a thickness of 25 μm and a coverlay (insulating film) composed of a polyimide film having a thickness of 12.5 μm are provided on the base layer 121 to cover the circuit pattern 122.

< measurement of gloss >

The 85 ° gloss was measured using a portable gloss meter (BYKGardner, seeded micro-gross, manufactured by eastern seiko sperm machine) in accordance with JIS Z8741.

< measurement of surface roughness >

Any 5 positions on the surface were measured using a confocal microscope (20 times objective lens, opterliccs HYBRID, manufactured by Lasertec) based on ISO 25178. After that, tilt correction of the surface was performed using data analysis software (LMeye 7), and Smr2, Svk and Sa were measured. The cutoff wavelength of the S filter was 0.0025mm, and the cutoff wavelength of the L filter was 0.8 mm. Further, each numerical value is an average value of values at arbitrary 5 positions on the measurement surface.

< evaluation of covering Property >

The ability to visually recognize a circuit pattern from the insulating protective layer side was evaluated at an angle of 45 degrees from the height of the shield wiring base material at an illuminance of 500 lux on the surface of the shield wiring base material placed on a flat table. When the circuit pattern was not visually recognized, the coverage was good (O), and when the circuit pattern was visually recognized, the coverage was poor (X).

(example 1)

A printed wiring base material-attached film was formed by using the insulating protective layer formed on the releasable substrate 1, and a shielded wiring base material was obtained. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 90.1% and Svk of 0.62 μm. Further, the 85 ℃ gloss was 33.7 and Sa was 0.48. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was very good. The circuit pattern is hardly visually recognized even by observation with a confocal microscope.

(example 2)

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 2 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 90.8% and Svk of 0.55 μm. Further, the 85 ℃ gloss was 28.7 and Sa was 0.41. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was very good. The circuit pattern is hardly visually recognized even by observation with a confocal microscope.

(example 3)

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 3 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 90.0% and Svk of 0.71 μm. Further, the 85 ℃ gloss was 32.3 and Sa was 0.51. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was very good. The circuit pattern is hardly visually recognized even by observation with a confocal microscope.

(example 4)

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 4 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 89.6% and Svk of 0.49 μm. Further, the 85 ℃ gloss was 41.1 and Sa was 0.42. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was good. The circuit pattern can be slightly visually recognized by observation with a confocal microscope.

(example 5)

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 5 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 90.8% and Svk of 0.90 μm. Further, the 85 ℃ gloss was 12.6 and Sa was 0.83. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was very good. The circuit pattern is hardly visually recognized even by observation with a confocal microscope.

(example 6)

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 6 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had Smr2 of 89.1% and Svk of 0.63 μm. Further, the 85 ℃ gloss was 30.0 and Sa was 0.47. mu.m. In the visual inspection, the circuit pattern was not visually recognized, and the covering property was very good. The circuit pattern is hardly visually recognized even by observation with a confocal microscope.

Comparative example 1

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 7 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had a Smr2 content of 92.1% and a Smr Svk content of 0.39. mu.m. Further, the 85 ℃ gloss was 30.6 and Sa was 0.45. mu.m. In the visual inspection, the circuit pattern can be visually recognized, and the covering property is poor. The circuit pattern can be clearly recognized by naked eyes in observation by a confocal microscope.

Comparative example 2

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 8 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had a Smr2 content of 93.9% and a Smr Svk content of 0.29. mu.m. Further, the 85 ℃ gloss was 39.9 and Sa was 0.43. mu.m. In the visual inspection, the circuit pattern can be visually recognized, and the covering property is poor. The circuit pattern can be clearly recognized by naked eyes in observation by a confocal microscope.

Comparative example 3

A shield wiring base material was obtained in the same manner as in example 1, except that the releasable substrate 9 was used. The insulating protective layer of the shield wiring base material after removal of the releasable substrate had a Smr2 content of 92.8% and a Smr Svk content of 0.43. mu.m. Further, the 85 ℃ gloss was 37.0 and Sa was 0.45. mu.m. In the visual inspection, the circuit pattern can be visually recognized, and the covering property is poor. The circuit pattern can be clearly recognized by naked eyes in observation by a confocal microscope.

Table 2 shows the characteristics of the insulating protective layers and the circuit pattern covering properties of the examples and comparative examples. When Smr2 is 91 or less, the covering property is good.

[ Table 2]

Fig. 4 shows the results of observation by the confocal microscope in each of the examples and comparative examples. In each of the examples, the shape of the circuit pattern was hardly recognized, whereas in each of the comparative examples, the shape of the circuit pattern was clearly recognized.

Practicality of use

The electromagnetic wave shielding film and the printed wiring substrate-attached film of the present application are excellent in covering properties and useful in applications requiring covering of circuit patterns.

Reference numerals

101 electromagnetic wave shielding film

102 printed wiring substrate

111 conductive adhesive layer

112 insulating protective layer

113 shield layer

121 base layer

122 circuit pattern

123 adhesive layer

124 insulating film

Claims (5)

1. The utility model provides a printed wiring substrate is with pasting epiphragma which characterized in that:

comprises an adhesive layer and an insulating protective layer,

the load area ratio (Smr 2) between the separated protruding valley portions and the central portion of the insulating protective layer is 91% or less.

2. The adhesive film for a printed wiring substrate according to claim 1, wherein:

the height (Svk) of the protruding valley part of the insulating protection layer is 0.45 [ mu ] m or more.

3. The adhesive film for a printed wiring substrate according to claim 1 or 2, wherein:

the adhesive layer has conductivity and functions as an electromagnetic wave shielding film.

4. The adhesive film for a printed wiring substrate according to claim 3, wherein:

and a shielding layer is also arranged between the adhesive layer and the insulating protective layer.

5. A shielded circuit substrate, comprising:

a wiring substrate including a base layer, a circuit pattern provided on the base layer, and an insulating film bonded to the base layer so as to cover the circuit pattern;

the film according to claim 3 or 4, wherein the film is bonded to the insulating film.