JP5223325B2 - Metal-coated polyethylene naphthalate substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a metal-coated polyethylene naphthalate substrate and a method for producing the same, and more particularly, a polyethylene naphthalate that is suitably used as a material for electronic components such as organic packages, printed wiring boards, flexible printed boards, and chip-on-film tapes. A metal-coated polyethylene naphthalate substrate having a metal layer comprising a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface of the phthalate-based film, the metal layer and the film Metal-coated polyethylene naphthalate substrate that has high initial adhesion strength, heat-resistant adhesion strength, etc., and can reduce the thickness of the entire substrate including the film thickness as required, and the efficiency of the substrate Relates to a method of manufacturing the same.

  In general, polyimide resin is often used as an insulating substrate material used for electronic components such as organic packages (organic PKG), printed wiring boards (PWB), flexible printed boards (FPC), and tapes for film on chip (COF tape). Yes. An organic PKG, PWB, FPC, or COF tape using such a polyimide resin is manufactured by processing a metal-coated polyimide substrate in which a metal layer such as copper is coated on at least one surface of a polyimide film.

  By the way, in recent years, with the progress of thinning, small size, light weight, high functionality, etc. of electronic devices, the speed of information transmission and information processing has further advanced, and when the frequency of signals has increased, in the use of polyimide film, There is a concern that transmission loss at high frequencies due to its high dielectric constant will increase. Furthermore, although polyimide films are excellent in heat resistance, there are limits to the production of thin films due to the properties of polyimide polymers, production methods, etc. Therefore, there is an economic problem due to high costs and low elasticity. The weakness of was a problem.

For this reason, attention has been focused on the use of a polyethylene naphthalate-based film that can withstand solder reflow and has high mechanical strength, as an insulating substrate material used in electronic components, instead of a conventional polyimide film.
For example, a polyethylene naphthalate film has the following features (a) to (d).
(A) Polyimide film has a dielectric constant of 3.3, whereas polyethylene naphthalate film has a dielectric constant as low as 2.9. Therefore, noise is generated even in a high frequency range of several GHz to hundred GHz. Signals can be transmitted at a low speed with little.
(B) The water absorption of the polyethylene naphthalate film is 0.3%, which is as low as about 1/4 of the polyimide film. Therefore, unlike a polyimide film, the high-frequency characteristics do not change due to water absorption, which is suitable for fields that require strict reliability, such as automobiles.
(C) Polyethylene naphthalate film has a rupture strength of 280 MPa, which is about the same as a polyimide film, but the Young's modulus is 6.1 GPa, which is about 1.7 times higher than that of a polyimide film. Even when the thickness of the film is reduced, the transportability of the film is good.
(D) Since the light transmittance in the visible light region of the polyethylene naphthalate film is superior to that of the polyimide film, in the polyethylene naphthalate film, a visible light curable adhesive can be used at the connection site. .

As a metal-coated substrate using such a polyethylene naphthalate film, a three-layer flexible substrate in which a copper foil serving as a conductor layer is bonded to a polyethylene naphthalate film using an adhesive (see, for example, Patent Document 1). And a two-layer flexible substrate in which a copper coating layer or the like directly forming a conductor layer is formed on a polyethylene naphthalate-based film by a dry plating method and / or a wet plating method without using an adhesive.
When a three-layer flexible substrate is used, a three-layer flexible wiring board can be manufactured by forming a desired wiring pattern on the substrate by a subtractive method. When a two-layer flexible substrate is used, a two-layer flexible wiring board can be manufactured by forming a desired wiring pattern on the substrate by a subtractive method or an additive method.

  By the way, conventionally, as a flexible substrate, the use of a three-layer flexible substrate that has a simple manufacturing method and can be manufactured at a low cost has been dominant. However, in recent years, with the increase in the density of electronic devices, a wiring board with a narrower wiring width has been required. However, when manufacturing a wiring board using a three-layer flexible substrate, there are the following problems (e) to (h).

(E) When the copper coating layer formed on the polyethylene naphthalate-based film is etched according to a desired wiring pattern to form a wiring portion, side surfaces of the wiring portion are etched, so-called side etching occurs, The cross-sectional shape of the wiring part tends to be a trapezoid with a wide skirt. In order to solve this problem, if etching is performed until electrical insulation between the wiring portions is ensured, the wiring pitch width becomes too wide. Therefore, a copper foil having a thickness of 35 μm that has been conventionally used is used as an adhesive. As long as a three-layer flexible substrate bonded with a polyethylene naphthalate film is used, there is a limit to narrowing the pitch of the wiring portion of the manufactured wiring board.

(F) In the above-described signal of several GHz to hundred GHz in the high frequency region, the signal flows intensively in a very thin region on the surface of the wiring layer. Therefore, when the unevenness of about several to several tens of μm is formed on the surface of the copper foil for the purpose of anchoring effect for obtaining adhesion with the polyethylene naphthalate film, the size of the unevenness of the copper foil is small. As a result, a large number of impedance discontinuities are formed, resulting in an increase in transmission loss. This reduces the advantage of using a polyethylene naphthalate film.
(G) In this case, in the region where the copper foil is removed by etching, the unevenness of the copper foil is transferred to the adhesive layer and the light transmittance is lowered. Therefore, the advantage of using a polyethylene naphthalate film having good light transmittance Will be reduced.
(H) Since the thickness of the adhesive layer is usually as thick as 20 to 40 μm, there is a problem that the thickness of the entire flexible substrate becomes considerably thick.

On the other hand, the two-layer flexible substrate forms a copper conductor layer directly on an insulator film without an adhesive, and the thickness of the substrate itself can be made thinner than that of a three-layer flexible substrate. The thickness of the copper coating layer is also advantageous in that it can be adjusted to an arbitrary thickness.
Such a two-layer flexible substrate includes a polymer film having at least one surface modified by plasma etching, a layer comprising a first metal nitride layer on the film, and the first metal nitride layer. A composite (see, for example, Patent Document 2) composed of an upper second metal nitride layer and a conductive metal layer on the second metal nitride layer has been proposed. However, in this composite proposal, no specific plasma etching amount is described, and in the case where a polyethylene naphthalate film is used as the polymer film, disclosure relating to adhesiveness closely related to reliability is sufficiently disclosed. It is hard to say that it is being done.

  In addition, the surface of the resin substrate that has been roughened so that the center line average roughness (Ra) is 30 to 300 nm is made of Al, Cr, Co, Ni, Cu, and Ag by sputtering. A printed wiring board (see, for example, Patent Document 3) in which a porous metal film made of at least one element selected from the group is coated has been proposed. However, this proposal only considers the formation of fine conductor wiring and adhesion to the substrate after the formation, and no suggestion is made regarding the adhesion (heat-resistant adhesion) in a heat-resistant environment. Still, the improvement of the adhesion in a severe heat environment has not been obtained.

  In addition to these, as the surface roughness, the value (Ra1) measured with a cutoff value of 0.002 mm of arithmetic average roughness is 0.05 to 1 μm, and this value and the cutoff value of 0.1 mm A laminate in which a metal layer is formed on the surface of a resin film having at least one surface shape such that the ratio (Ra1 / Ra2) to the measured value (Ra2) is 0.4 to 1 (see, for example, Patent Document 4) .) Has been proposed. However, in this laminate as well, the improvement in adhesion is only disclosed as the adhesive strength at normal temperature, and no suggestion is made regarding the adhesion in a heat-resistant environment.

  As described above, in the conventional two-layer flexible substrate using a polyethylene naphthalate-based film, the initial adhesion between the polyethylene naphthalate-based film and the metal layer is not sufficient, and in particular, the adhesion in a heat-resistant environment. There was a problem to be solved such as force (hereinafter sometimes referred to as heat-resistant adhesion).

JP 2006-013135 A (first page, second page) JP 2002-511809 (first page, second page) International Publication WO2003 / 103352 Specification JP-A-2004-276401 (first page, second page)

  In view of the above-mentioned problems of the prior art, the object of the present invention is a polyethylene naphthalate-based film that is suitably used as a material for electronic components such as organic packages, printed wiring boards, flexible printed boards, and chip-on-film tapes. A metal-coated polyethylene naphthalate substrate having a metal layer comprising a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface, wherein the metal layer and the film are in initial contact with each other Metal-coated polyethylene naphthalate substrate capable of reducing the overall thickness of the substrate, including the film thickness, if necessary, and a method for efficiently producing the substrate. Is to provide.

  In order to achieve the above object, the present inventors have a metal layer comprising a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface of the polyethylene naphthalate film. As a result of extensive research on the metal-coated polyethylene naphthalate substrate, the surface of the polyethylene naphthalate-based film in contact with the base metal layer has a specific roughness, and the formed base metal layer has a specific composition and thickness. When the nickel alloy layer has a metal-coated polyethylene layer having high adhesion such as initial adhesion and heat-resistant adhesion between the metal layer and the film and a thin substrate as a whole, including the film thickness, if necessary. A phthalate substrate can be obtained, and the manufacturing method thereof includes a dry surface so that a polyethylene naphthalate film has a predetermined roughness. Subjected to reason, then was formed a predetermined base metal layer by a dry plating method, they found that the above-described metallized polyethylene naphthalate substrate is obtained efficiently, and have completed the present invention.

That is, according to the first aspect of the present invention, a metal having a metal layer composed of a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface of the polyethylene naphthalate film. A coated polyethylene naphthalate substrate,
The following requirements (1) and (2) are satisfied , the initial adhesion between the metal layer and the polyethylene naphthalate film, and the heat-resistant adhesion measured at room temperature after standing in the atmosphere at 150 ° C. for 168 hours. All are provided with a metal-coated polyethylene naphthalate substrate having a peel strength of 400 N / m or more .
(1) The centerline average roughness (Ra) of the surface of the polyethylene naphthalate-based film in contact with the base metal layer is 0.5 to 4 nm.
(2) The base metal layer contains 7 to 20% by mass of at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum formed by a dry plating method , with the balance being nickel. a nickel alloy, and its thickness is 3 to 50 nm.

According to a second aspect of the present invention, there is provided a metal-coated polyethylene naphthalate substrate according to the first aspect, wherein the polyethylene naphthalate film has a thickness of 1 to 50 μm. .

According to the third invention of the present invention, the surface of at least one side of the polyethylene naphthalate film is subjected to a dry surface treatment so that the center line average roughness (Ra) is 0.5 to 4 nm, then, on its surface, the chromium by a dry plating method, vanadium, at least one metal selected from the group consisting of titanium and molybdenum containing 7 to 20 wt% based on the total, the balance is nickel alloy nickel, A metal-coated polyethylene naphthalate substrate according to the first or second invention, wherein a base metal layer having a thickness of 3 to 50 nm is formed, and then a copper coating layer is laminated on the base metal layer. A manufacturing method is provided.

According to a fourth aspect of the present invention, in the third aspect , the dry surface treatment is performed by subjecting to an ultraviolet irradiation treatment and / or a plasma treatment in an oxygen gas atmosphere. A method of manufacturing a metal-coated polyethylene naphthalate substrate is provided.

According to a fifth invention of the present invention, in the third or fourth invention, the dry plating method is any one of a vacuum deposition method, a sputtering method, and an ion plating method. A method of manufacturing a coated polyethylene naphthalate substrate is provided.

According to the sixth invention of the present invention, in laminating the copper coating layer in any one of the third to fifth inventions, first, the copper coating layer is formed by a dry plating method, and then Furthermore, a method for producing a metal-coated polyethylene naphthalate substrate is provided, wherein a copper coating layer is formed by a wet plating method.

According to a seventh invention of the present invention, in any one of the third to sixth inventions, the thickness of the polyethylene naphthalate-based film is 1 to 50 μm, The metal-coated polyethylene naphthalate A method for manufacturing a substrate is provided.

  According to the metal-coated polyethylene naphthalate substrate of the present invention, there is an adhesive force such as an initial adhesive force and a heat-resistant adhesive force between a metal layer comprising a base metal layer and a copper coating layer laminated on the base metal layer and a film. It can be used as a material for electronic components such as organic packages, printed wiring boards, flexible printed circuit boards, chip-on-film tapes, etc. In particular, it can be suitably used for a flexible wiring board having wiring portions with a narrow width and a narrow pitch. Furthermore, since the dielectric constant of polyethylene naphthalate film is lower than that of polyimide film, it can transmit signals at high speed with less noise even in the high frequency range of several GHz to hundred GHz, compared with polyimide film. In addition, since the water absorption rate is low, the high frequency characteristics do not change due to water absorption, and therefore, there is an advantage that it is suitable for a field where strict reliability is required such as an automobile.

  Moreover, according to the manufacturing method of this invention, the said metal coating polyethylene naphthalate board | substrate can be manufactured efficiently. For example, since the Young's modulus of polyethylene naphthalate film is high, the film transportability is good even when the film is thin, and the light transmittance in the visible light region is superior to the polyimide film Therefore, there is an advantage that a visible light curable adhesive can be used at the connection site. Therefore, these industrial values are extremely large.

Hereinafter, the metal-coated polyethylene naphthalate substrate of the present invention and the production method thereof will be described in detail.
1. Metal-coated polyethylene naphthalate substrate The metal-coated polyethylene naphthalate substrate of the present invention is a metal comprising a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface of a polyethylene naphthalate film. A metal-coated polyethylene naphthalate substrate having a layer, which satisfies the following requirements (1) and (2) , an initial adhesion between the metal layer and the polyethylene naphthalate film, and 150 ° C. in the air Any of the heat-resistant adhesion measured at room temperature after standing for 168 hours is characterized by a peel strength of 400 N / m or more .
(1) The centerline average roughness (Ra) of the surface of the polyethylene naphthalate-based film in contact with the base metal layer is 0.5 to 4 nm.
(2) The base metal layer contains 7 to 20% by mass of at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum formed by a dry plating method , with the balance being nickel. a nickel alloy, and its thickness is 3 to 50 nm.

  In the metal-coated polyethylene naphthalate substrate of the present invention, it is particularly important that the surface of the polyethylene naphthalate-based film that is in contact with the base metal layer and the base metal layer satisfy the requirements (1) and (2) above. It is. As a result, a two-layer flexible substrate that has high adhesion such as initial adhesion between the metal layer and the film closely related to reliability, heat-resistant adhesion, and the like, and if necessary, the total thickness of the substrate including the film thickness is thin Can be obtained.

First, a film, a base metal layer and a copper coating layer constituting the metal-coated polyethylene naphthalate substrate of the present invention will be described.
(1) Polyethylene naphthalate film The polyethylene naphthalate film used for the substrate is not particularly limited, and a conventionally known polyethylene naphthalate film can be used. Examples thereof include those commercially available as Teonex (registered trademark) from Teijin / DuPont Films.

  The polyethylene naphthalate-based film may contain various known additives such as an antioxidant and an antistatic agent as long as the physical properties of the film and flexible substrate are not impaired. In addition, for the purpose of improving the handleability as a film, a material to which an inorganic material such as silica or clay is appropriately added can be used.

  Although it does not specifically limit as thickness of the said polyethylene naphthalate type | system | group film, It can select from the range of 1-50 micrometers as needed. Thereby, the thickness of the whole board | substrate including film thickness can be made into a 2 layer flexible board | substrate thin compared with the case of the conventional polyimide film. That is, when the thickness of the film is less than 1 μm, the stiffness as a film becomes weak, so that not only the handling property is lowered but also the film strength is not sufficient. On the other hand, when the thickness of the film exceeds 50 μm, it is not preferable because the film becomes too stiff and difficult to bend, and the thickness of the entire substrate increases.

  Here, it is important that the centerline average roughness (Ra) of the surface of the polyethylene naphthalate-based film in contact with the base metal layer is adjusted to 0.5 to 4 nm. Thereby, the adhesive force such as the initial adhesive force and the heat-resistant adhesive force between the metal layer composed of the base metal layer and the copper coating layer laminated on the base metal layer and the film is improved.

  That is, as a surface treatment, when a polyimide film surface is generally subjected to dry surface treatment such as plasma treatment or corona discharge, or wet surface treatment, a weak boundary of the surface is removed and a carboxyl group is simultaneously removed. It is known that a hydrophilic functional group such as a hydroxyl group or a hydroxyl group is introduced to improve the adhesion to a metal. However, in a polyethylene naphthalate-based film, in a two-layer flexible substrate produced by performing a dry surface treatment under the same conditions as a polyimide film, the adhesion is reduced after the heat resistance test. The cause of this is that, from the result of detailed analysis of the peel interface after measuring the adhesion strength of the two-layer flexible substrate, the temperature of the film surface exceeded the glass transition temperature (about 155 ° C.) by dry surface treatment. It was considered that the strength was lowered, and thus the adhesion was lowered. Therefore, in order to ensure a good balance of initial adhesion and heat-resistant adhesion, control of dry surface treatment, that is, control of the surface roughness of the polyethylene naphthalate film with which the base metal layer obtained by dry surface treatment is in contact is appropriately controlled. It is essential to do.

In addition, as the surface roughness of the surface of the polyethylene naphthalate-based film that is in contact with the base metal layer, the center line average roughness (Ra) is adjusted to 0.5 to 4 nm while actually in contact with the base metal layer. It is required to be done. However, since the surface roughness of the film hardly changes due to the coating of the metal layer, any value obtained in the state before coating the metal layer or after removing the metal layer after coating is used as the surface roughness. be able to.
The surface roughness is based on JIS B0601-2001. Here, an atomic force microscope is used and the measurement range is 1 μm × 1 μm. The centerline average roughness (Ra) is extracted from the roughness curve by a reference length in the direction of the average line, the X-axis is taken in the direction of the extracted portion, the Y-axis is taken in the vertical direction, and y = f (x) The value obtained by the following equation 1 is expressed.

（但し、式中のＬは基準長さを表す。）

(However, L in the formula represents a reference length.)

That is, when the center line average roughness (Ra) is less than 0.5 nm, hydrophilic functional groups such as carboxyl groups and hydroxyl groups are not sufficiently introduced into the polyethylene naphthalate film surface, so that the adhesion strength between the metal layer and the film is high. Run short.
On the other hand, if the center line average roughness (Ra) is strong or long, the film surface temperature exceeds the glass transition temperature (about 155 ° C.) and the film strength decreases. The adhesion strength between the layer and the film decreases. In addition, uniform coating with the underlying metal layer is not possible, so that copper diffuses from the copper coating layer to the polyethylene naphthalate film, causing the adhesion between the metal layer formed on the film and the film. descend.

(2) Underlying metal layer The underlying metal layer used for the substrate includes, as a main component, a nickel alloy containing at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum, and has a film thickness of It is important that it is 3-50 nm.
That is, the composition of the base metal layer includes, as a main component, a nickel alloy containing at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum. These metals are added to nickel. By using an alloy, corrosion resistance and heat resistance are remarkably improved. In addition, copper can be prevented from diffusing into the polyethylene naphthalate film from the copper coating layer laminated on the base metal layer, and the adhesion between the metal layer and the film can be improved. In addition to the nickel alloy containing at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum, the base metal layer is included when it is taken in during the production of the target used in the dry plating method. 1% by mass or less of inevitable impurities may be present as a subcomponent with respect to the whole.

The composition of the nickel alloy is not particularly limited, and a nickel alloy containing at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum is used. Among them, chromium, It is preferable that at least one metal selected from the group consisting of vanadium, titanium and molybdenum is contained in an amount of 7 to 20% by mass with respect to the total amount, with the balance being nickel. That is, if the total value of chromium, vanadium, titanium, and molybdenum is less than 7% by mass with respect to the total amount, it may not be possible to prevent the heat resistant adhesion from being significantly reduced due to thermal degradation. On the other hand, if the total value of chromium, vanadium, titanium, and molybdenum exceeds 20% by mass, the energy required for film formation by the dry plating method increases, and the temperature of the film surface changes to the glass transition during film formation. Since the temperature is exceeded, the adhesion may be reduced.
For the purpose of improving the heat resistance and corrosion resistance of the nickel alloy, a transition metal element can be appropriately added according to the target characteristics. Here, as the additive metal, cobalt or tungsten is particularly preferable.

  The film thickness of the base metal layer is 3 to 50 nm, but when the film thickness of the base metal layer is less than 3 nm, the etching solution is interposed between the film and the base metal layer when wiring processing is performed using the substrate. The peel strength of the wiring portion is significantly reduced due to the penetration and the floating of the wiring portion. On the other hand, when the film thickness of the base metal layer exceeds 50 nm, the film surface temperature exceeds the glass transition temperature due to heat inclusion during the formation of the base metal layer, and thus the adhesion is reduced.

  As described above, by combining the polyethylene naphthalate film whose surface roughness is controlled as described above and the base metal layer having the above composition and film thickness, the action is combined. Thus, it is possible to achieve greater adhesion than in the past.

(3) Copper coating layer The copper coating layer used for the substrate is not particularly limited as long as it is formed as a conductive layer on the base metal layer, but is formed by a dry plating method or a wet plating method. Is used.

  Although it does not specifically limit as a film thickness of the said copper coating layer, It is preferable that it is 10 nm-18 micrometers. That is, when the film thickness is less than 10 nm, the electric resistance as the conductive layer increases, which is not preferable. On the other hand, when the film thickness exceeds 18 μm, not only the productivity at the time of film formation is lowered but also the thickness of the entire substrate is increased, which is not preferable.

Next, the adhesion strength of the metal-coated polyethylene naphthalate substrate of the present invention will be described.
In the above substrate, the initial adhesion between the metal layer composed of the base metal layer and the copper coating layer laminated on the base metal layer and the polyethylene naphthalate film and left in the atmosphere at 150 ° C. for 168 hours. Any of the heat-resistant adhesion strengths measured later at room temperature can provide sufficient adhesion as a metal-coated resin substrate used for electronic components such as organic packages, printed wiring boards, flexible printed boards, and chip-on-film tapes.
Further, among these, the composition of the nickel alloy of the base metal layer contains 7 to 20% by mass of the total amount of at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum, with the balance being nickel. In this case, both the initial adhesion strength and the heat-resistant adhesion strength can achieve a peel strength of 400 N / m or more.

  That is, in the metal-coated polyethylene naphthalate substrate, although not particularly limited, not only the initial adhesion after forming the copper coating layer but also the heat adhesion in a heat resistant environment is the same as that of the three-layer flexible substrate. The above adhesion is desired. That is, since the adhesion strength of the three-layer flexible substrate is usually 400 N / m in peel strength, if these adhesion strengths are less than 400 N / m in peel strength, the wiring can be used when components or elements are mounted at high temperatures. There is a risk of problems such as deformation and peeling. In addition, it can measure by the method based on IPC-TM-650 and NUMBER2.4.9, using peel strength as an index of the adhesion. Here, the peel strength tends to show a higher value as the copper thickness increases, but the measurement is based on a measurement with a copper thickness of 5 to 12 μm, which is equivalent to a metal-coated resin substrate that is currently widely used.

2. Method for Producing Metal-Coated Polyethylene Naphthalate Substrate The method for producing a metal-coated polyethylene naphthalate substrate of the present invention is such that the surface of at least one side of the polyethylene naphthalate film has a center line average roughness (Ra) of 0.5 to 4 nm. Then, it is subjected to a dry surface treatment, and then contains 7 to 20% by mass of at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum on the surface by a dry plating method. the balance is nickel alloy nickel, and the film thickness to form a base metal layer is 3 to 50 nm, followed by characterized by laminating a copper coating layer on the lower ground metal layer. Thereby, the metal-coated polyethylene naphthalate substrate of the present invention can be produced efficiently.

  Although it does not specifically limit as a specific embodiment of the said manufacturing method, For example, using a polyethylene naphthalate type film, the dehydration process and dry-type surface treatment, formation of a base metal layer, and a copper coating layer It is performed by the method including each process of formation.

  As the polyethylene naphthalate film, the same polyethylene naphthalate film as that described in the explanation of the metal-coated polyethylene naphthalate substrate of the present invention is used. That is, the polyethylene naphthalate film is not particularly limited, and a conventionally known polyethylene naphthalate film can be used. Examples thereof include those commercially available as Teonex (registered trademark) from Teijin / DuPont Films. The thickness of the polyethylene naphthalate film is not particularly limited, but can be selected from a range of 1 to 50 μm as necessary. As a result, it is possible to obtain a two-layer flexible substrate in which the thickness of the entire substrate including the film thickness is thinner than that of a conventional polyimide film. That is, when the thickness of the film is less than 1 μm, the stiffness as a film becomes weak, so that not only the handling property is lowered but also the film strength is not sufficient. On the other hand, when the thickness of the film exceeds 50 μm, it is not preferable because the film becomes too stiff and difficult to bend, and the thickness of the entire substrate increases.

Below, the manufacturing method of the metal coating polyethylene naphthalate board | substrate of this invention is demonstrated for every said process.
(1) Dehydration treatment step of polyethylene naphthalate film The dehydration treatment step is performed as necessary, and is a step of removing water contained in the polyethylene naphthalate film. A commercially available polyethylene naphthalate-based film usually contains moisture, and before forming the base metal layer by a dry plating method, it is heated in the air and / or in vacuum to remove moisture present in the film. It is desirable to remove it. If this moisture removal is insufficient, the adhesion between the film and the underlying metal layer may be reduced. However, since polyethylene naphthalate is not as heat-resistant as polyimide, it is preferably heated under conditions weaker than the polyimide film, for example, a heater temperature lower than 150 ° C. and a short processing time.

(2) Dry surface treatment step In the dry surface treatment step, at least one surface of the polyethylene naphthalate film obtained in the dehydration treatment step has a center line average roughness (Ra) of 0.5 to 4 nm. It is the process of attaching | subjecting to a dry-type surface treatment.

  That is, when the center line average roughness (Ra) is less than 0.5 nm, for example, when there is no dry surface treatment or when the dry surface treatment is too weak, hydrophilicity such as carboxyl groups and hydroxyl groups on the polyethylene naphthalate film surface is obtained. Since the functional functional group is not sufficiently introduced, the adhesion strength between the metal layer and the film is insufficient. Normally, it is difficult to control the center line average roughness (Ra) to less than 0.5 nm by dry surface treatment, and stable production cannot be achieved.

  On the other hand, when the center line average roughness (Ra) exceeds 4 nm, the polyethylene naphthalate is processed because the processing is performed under the strong condition of removing the weak boundary (fragile layer) on the surface of the polyimide film as in the case of the polyimide film. Since the film surface has essentially no weak boundary (fragile layer) and the glass transition temperature is not as high as that of the polyimide film, the film surface temperature exceeds the glass transition temperature (about 155 ° C), resulting in a decrease in adhesion strength. Wake up. Furthermore, since the surface roughness becomes large, uniform coating with the underlying metal layer cannot be performed, and therefore, copper diffuses from the copper coating layer to the polyethylene naphthalate film, and is thus formed on the film. The adhesion between the metal layer and the film is reduced.

The dry surface treatment method used in the above process is not particularly limited, and the polyethylene naphthalate film does not have the heat resistance as that of the polyimide film. A method capable of performing the treatment so that the roughness (Ra) is 0.5 to 4 nm is selected. However, it is preferable to perform an ultraviolet irradiation treatment and / or a plasma treatment in an oxygen gas atmosphere. Moreover, it is more preferable to perform a corona discharge, an ion irradiation process, etc. before these processes.
As the ultraviolet irradiation treatment, for example, by using a low-pressure mercury lamp or an excimer lamp and treating in an oxygen atmosphere, a desired surface roughness can be obtained.

  Further, when the modified layer is formed by the plasma treatment, for example, any of a direct current method, an alternating current method, and a high frequency method can be used. As an apparatus for performing this plasma treatment, the shape of the electrode is not particularly limited, and various shapes of electrodes such as a plate shape, a ring shape, and a rod shape can be used. For example, a method in which a roll-shaped polyethylene naphthalate film is unwound from an unwinder installed inside the plasma processing apparatus, passed between discharge electrodes and wound by a winder, and is effective. It is preferable.

In the dry surface treatment method described above, the surface roughness can be controlled by adjusting the oxygen gas pressure or the input energy. Therefore, these may be adjusted so as to obtain a desired surface roughness. Moreover, since the temperature of the polyethylene naphthalate film surface is important, it is preferable to select the surface treatment conditions so as to be lower than the glass transition temperature.
For example, by processing at a lower input energy than in the case of a polyimide film, the film surface roughness is adjusted to a centerline average roughness (Ra) of 0 while adjusting the temperature of the polyethylene naphthalate film surface to less than the glass transition temperature. Control to be 5 to 4 nm.

(3) Formation process of base metal layer The formation process of the base metal layer includes chromium, vanadium, titanium, and molybdenum on the surface of the polyethylene naphthalate film subjected to the dry surface treatment in the dry surface treatment process by a dry plating method. Forming a base metal layer having a nickel alloy containing at least one metal selected from the group consisting of as a main component and a film thickness of 3 to 50 nm.

  The composition of the nickel alloy used in the above process is not particularly limited, and a nickel alloy containing at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum is used. It is preferable that at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum is contained in an amount of 7 to 20% by mass with respect to the total amount, with the balance being nickel. That is, if the total value of chromium, vanadium, titanium, or molybdenum is less than 7% by mass with respect to the total amount, it may not be possible to prevent the heat-resistant adhesion from being significantly reduced due to thermal deterioration. On the other hand, if the total value of chromium, vanadium, titanium, or molybdenum exceeds 20% by mass with respect to the total amount, the energy required for film formation by the dry plating method increases, and the temperature of the film surface during the film formation causes the glass transition temperature to increase. Therefore, the adhesion may decrease.

  In addition, when the thickness of the base metal layer is less than 3 nm, when the wiring processing is performed using the substrate, the etching solution penetrates between the film and the base metal layer, and the wiring portion floats. The peel strength of the part is significantly reduced. On the other hand, when the film thickness of the base metal layer exceeds 50 nm, the film surface temperature exceeds the glass transition temperature due to heat inclusion during the formation of the base metal layer, and the adhesion is reduced.

  The dry plating method used in the above step is not particularly limited, and any one of a vacuum vapor deposition method, a sputtering method, and an ion plating method is preferable, and a sputtering method is more preferable. For example, when a base metal layer is formed on the surface of the polyethylene naphthalate film using a film winding type sputtering apparatus, there is usually almost no deviation in the composition of the sputtering target and the resulting metal thin film, An alloy target having a composition equivalent to the composition of the desired base metal layer may be used as the sputtering cathode. The film thickness of the base metal layer can be controlled to a desired film thickness by controlling the film conveyance speed and sputtering conditions.

More specifically, the polyethylene naphthalate film subjected to the dehydration treatment and the dry surface treatment is set in a sputtering apparatus, the sputtering apparatus is evacuated, Ar gas is introduced, and the interior of the apparatus is reduced to 0. Hold at about 13 to 1.3 Pa. In this state, power is supplied from the DC power source for sputtering connected to the cathode while the polyethylene naphthalate film mounted on the winding / unwinding roll in the sputtering apparatus is transported at a speed of about 1 to 20 m / min. Then, sputtering discharge is performed on the alloy target, and a desired base metal layer is continuously formed on the film.
Here, the power density supplied from the DC power source for sputtering is preferably in the range of 1 to ²⁰ W / cm ² . By this sputtering film formation, it contains at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum in a total amount of 7 to 20% by mass, and the remainder includes nickel alloy as a main component, And the base metal layer whose film thickness is 3-50 nm is formed on a film.

(4) Formation process of a copper coating layer The formation process of the said copper coating layer is a process of laminating | stacking a copper coating layer on the base metal layer formed at the formation process of the said base metal layer.
The method for forming the copper coating layer used in the above process is not particularly limited, and either a dry plating method or a wet plating method can be selected. In the case of forming the film, it is preferable to form a copper coating layer by a dry plating method and then form a copper coating layer thereon by a wet plating method. Thereby, the copper film layer which has the desired thickness calculated | required as a conductive layer can be formed economically. On the other hand, when the copper coating layer is formed thin, for example, when only a thin film of 50 nm or less is required, the copper coating layer can be formed only by the dry plating method.

  As the dry plating method used in the above process, any one of a vacuum deposition method, a sputtering method, and an ion plating method can be used. For example, a copper coating layer can be formed using a copper target and a sputtering apparatus similar to the case of forming the base metal layer. At this time, the base metal layer and the copper coating layer are preferably formed continuously in the same vacuum chamber.

  In addition, when a copper coating layer is further laminated by a wet plating method on a copper coating layer by a dry plating method, an electroless copper plating treatment or a secondary plating as a primary plating method, or as a primary plating. Any of the methods performed by combining wet plating methods such as electrolytic copper plating may be selected. Here, the method of the wet copper plating treatment is not particularly limited, and various conditions according to ordinary methods may be adopted. At this time, the thickness of the copper coating layer by dry plating is preferably 10 nm or more. That is, if it is less than 10 nm, the conductivity of the copper coating layer is low, and a sufficient power supply amount cannot be ensured when performing electrolytic copper plating or the like. By forming the copper coating layer on the base metal layer by the above method, a two-layer flexible substrate having a high degree of adhesion of the copper coating layer can be obtained.

3. Flexible wiring board A flexible wiring board is obtained by individually forming a wiring pattern on at least one surface of the metal-coated polyethylene naphthalate substrate. Also, via holes for interlayer connection can be formed at predetermined positions on the substrate, and used for various purposes.
As a more specific method of forming the wiring pattern, for example, the following wiring patterns (A) to (C) are used.
(A) A high-density wiring pattern is individually formed on at least one surface of the flexible sheet. (B) A via hole penetrating the wiring layer and the flexible sheet is formed in the flexible sheet on which the wiring layer is formed.
(C) In some cases, the via hole is filled with a conductive substance to make the inside of the hole conductive.

  As a method for forming the wiring pattern, a conventionally known method such as photoetching can be used. For example, a metal-coated polyethylene naphthalate substrate having a metal layer formed on at least one surface is prepared, and screen printing is performed on the metal layer. Alternatively, after laminating a dry film to form a photosensitive resist film, patterning is performed by exposure and development, and then the metal layer is selectively etched away with an etching solution such as ferric chloride solution, and then the resist is removed. To form a predetermined wiring pattern. Here, in order to further increase the density of the wiring, it is preferable to prepare a two-layer flexible substrate in which metal layers are formed on both surfaces, and pattern the both surfaces to form wiring patterns on both surfaces of the substrate. Whether or not the entire wiring pattern is divided into the number of wiring areas depends on the distribution of the wiring density of the wiring pattern. For example, the wiring pattern has a wiring width and a wiring interval of 50 μm or less, respectively, and other wiring areas. In consideration of the difference in thermal expansion from the printed circuit board and convenience in handling, the size of the wiring board to be divided may be set to about 10 to 65 mm and divided appropriately.

  As a method for forming the via hole, a conventionally known method can be used. For example, a via hole penetrating the wiring pattern and the flexible sheet is formed at a predetermined position of the wiring pattern by laser processing or the like. The diameter of the via hole is preferably reduced within a range that does not hinder the conductivity in the hole, and is usually 100 μm or less, preferably 50 μm or less. The via hole is filled with a conductive metal such as copper by plating, vapor deposition, sputtering or the like, or a conductive paste is press-fitted and dried using a mask having a predetermined opening pattern, and the hole is made conductive. To make electrical connection between layers. Examples of the conductive metal include copper, gold, and nickel.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis method of the metal used by the Example and the comparative example, centerline average roughness (Ra), the initial adhesion force by peel strength, and the evaluation method of heat-resistant adhesion force are as follows.
(1) Metal analysis: ICP emission analysis was performed.
(2) Measurement of centerline average roughness (Ra): The obtained substrate was etched with a ferric chloride solution to remove the metal layer consisting of the base metal layer and the copper coating layer, and then the atomic force microscope NS- The center line average roughness (Ra) of the surface was measured by III D5000 system (made by DI company).

(3) Measurement of initial adhesion: Peel strength was measured by a method based on IPC-TM-650 and NUMBER 2.4.9. First, a dry film is laminated on a part of the obtained substrate to form a photosensitive resist film, exposed and developed, the metal layer is etched away with a ferric chloride solution, and then the resist is removed. A 1 mm wide lead for peel strength evaluation was formed. The peel angle was 90 °. Leads were formed by the subtractive method or the semi-additive method. Although the peel strength tends to show a higher value as the copper thickness increases, the adhesion strength was measured based on the measurement at a copper thickness of 8 μm, which is equivalent to a metal-coated resin substrate that is currently widely used.
(4) Measurement of heat-resistant adhesion The film substrate on which a 1 mm lead was formed was left in an oven at 150 ° C. for 168 hours, taken out to room temperature, and then the same as the measurement of the initial adhesion. Performed by the method.

Example 1
A polyethylene naphthalate film having a thickness of 25 μm (manufactured by Teijin DuPont Films, trade name “Teonex Q83”) was used. The film was heated in a vacuum vessel at a temperature of 150 ° C. or lower, and then exposed to plasma for several seconds in an atmosphere with an oxygen gas pressure of 1.0 Pa to perform dehydration treatment and dry surface treatment of the polyethylene naphthalate film. Subsequently, the obtained film was subjected to a DC sputtering method using a 7 mass% Cr-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, and then the 7 mass% Cr-Ni alloy foundation. A metal layer was deposited to a thickness of 7 nm. Subsequently, a copper film layer having a thickness of 100 nm was formed thereon by a direct current sputtering method using a Cu target (manufactured by Sumitomo Metal Mining Co., Ltd.) as a second layer. Thereafter, a copper coating layer was laminated to 8 μm by electroplating to obtain a metal-coated polyethylene naphthalate substrate.

  Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 2)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 1 except that the plasma atmosphere was changed to an oxygen gas pressure of 2.0 Pa.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 3)
A 7 mass% V-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) was used as the first layer of the foundation metal layer, and a 7 mass% V-Ni alloy foundation metal layer was formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

Example 4
A 7.5% by mass Ti—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) was used as the first layer of the base metal layer, and a 7.5% by mass Ti—Ni alloy base metal layer was formed at 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed to a thickness.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 5)
Using a 10% by mass Mo—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the underlying metal layer, a 10% by mass Mo—Ni alloy underlying metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 6)
Using a 20 mass% Cr-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 20 mass% Cr-Ni alloy foundation metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 7)
Using a 20% by mass Mo—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the underlying metal layer, a 20% by mass Mo—Ni alloy underlying metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 8)
A 6 mass% Cr-10 mass% Mo-Ni alloy was formed by DC sputtering using a 6 mass% Cr-10 mass% Mo-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the base metal layer. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the base metal layer was formed to a thickness of 7 nm.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

Example 9
Using a 4 mass% V-10 mass% Mo-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the base metal layer, a 4 mass% V-10 mass% Mo-Ni alloy was formed by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the base metal layer was formed to a thickness of 7 nm.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 10)
Using a 7 mass% Ti-10 mass% Mo-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the base metal layer, a 7 mass% Ti-10 mass% Mo-Ni alloy was formed by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the base metal layer was formed to a thickness of 7 nm.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 11)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 6 except that the plasma atmosphere was changed to an oxygen gas pressure of 3.0 Pa.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 12)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 6 except that the base metal layer was formed to a thickness of 3 nm.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 13)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 6 except that the base metal layer was formed to a thickness of 30 nm.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Example 14)
Using a 6 mass% Cr-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 6 mass% Cr-Ni alloy foundation metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 14 is a reference example.

(Example 15)
Using a 6 mass% V-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 6 mass% V-Ni alloy foundation metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 15 is a reference example.

(Example 16)
Using a 6 mass% Ti-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 6 mass% Ti-Ni alloy foundation metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 16 is a reference example.

(Example 17)
Using a 6% by mass Mo—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the underlying metal layer, a 6% by mass Mo—Ni alloy underlying metal layer is formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 17 is a reference example.

(Example 18)
Using a 21 mass% Cr—Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 21 mass% Cr—Ni alloy foundation metal layer was formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 18 is a reference example.

(Example 19)
Using a 21 mass% Mo-Ni alloy target (manufactured by Sumitomo Metal Mining Co., Ltd.) as the first layer of the foundation metal layer, a 21 mass% Mo-Ni alloy foundation metal layer was formed to a thickness of 7 nm by DC sputtering. A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 2 except that the film was formed.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1. This Example 19 is a reference example.

(Comparative Example 1)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 6 except that only corona discharge was performed in the atmosphere as a dry surface treatment.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

(Comparative Example 2)
A metal-coated polyethylene naphthalate substrate was obtained in the same manner as in Example 1 except that the plasma treatment time was 10 seconds or longer and the conditions were the same as those of the polyimide film.
Thereafter, the center line average roughness (Ra) of the obtained substrate was measured in accordance with the above-described method for measuring the center line average roughness (Ra). The results are shown in Table 1. Moreover, according to the method for measuring the initial adhesion and the heat-resistant adhesion, the initial adhesion and the heat-resistant adhesion due to the peel strength of the obtained substrate were obtained. The results are shown in Table 1.

From Table 1, in Examples 1 to 19 (however, Examples 14 to 19 are reference examples) , the center line average roughness (Ra) of the surface of the polyethylene naphthalate film of the metal-coated polyethylene naphthalate substrate, and the base metal layer It can be seen that high initial adhesion and heat-resistant adhesion can be obtained because the composition and film thickness were performed according to the method of the present invention. In particular, in Examples 1 to 13, the underlying metal layer is a nickel alloy containing 7 to 20% by mass of at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum, based on the total amount of the alloy. Both the initial adhesion force and the heat-resistant adhesion force between the metal layer and the polyethylene naphthalate film can provide a peel strength of 400 N / m or more. In Examples 14 to 19 (reference examples) , the content of at least one metal selected from the group consisting of chromium, vanadium, titanium, and molybdenum in the base metal layer does not meet these conditions. Somewhat low in heat-resistant adhesion.

  On the other hand, in Comparative Example 1 or 2, since the center line average roughness (Ra) of the polyethylene naphthalate film surface of the metal-coated polyethylene naphthalate substrate does not meet these conditions, the initial adhesion strength and the heat-resistant adhesion strength are In either case, it can be seen that satisfactory results cannot be obtained.

As described above, according to the metal-coated polyethylene naphthalate substrate of the present invention, the initial adhesion strength and heat-resistant adhesion between the metal layer and the film comprising the base metal layer and the copper coating layer laminated on the base metal layer. Since the overall thickness of the board including the film thickness can be reduced if necessary, such as organic packages, printed wiring boards, flexible printed boards, chip-on-film tapes, etc. It is used as a material for electronic components, and is particularly suitable for a flexible wiring board having a narrow width and a narrow pitch wiring portion suitable for high-frequency signal transmission and capable of high-density mounting. Furthermore, since the polyethylene naphthalate film has a lower dielectric constant than a polyimide film, it is possible to transmit a signal at high speed with less noise generation even in a high frequency region of several GHz to hundred GHz, Since the water absorption rate is low, the high frequency characteristics do not change due to water absorption. Therefore, it is used in fields such as automobiles where strict reliability is required.
Further, according to the production method of the present invention, for example, since the Young's modulus of a polyethylene naphthalate film is high, the transportability of the film is good even when the film is thinned, and the light transmission in the visible light region. Since the property is excellent, it is possible to make use of advantages such as the ability to use a visible light curable adhesive at the connection site.

Claims (7)

A metal-coated polyethylene naphthalate substrate having a metal layer composed of a base metal layer and a copper coating layer laminated on the base metal layer on at least one surface of the polyethylene naphthalate film,
The following requirements (1) and (2) are satisfied , the initial adhesion between the metal layer and the polyethylene naphthalate film, and the heat-resistant adhesion measured at room temperature after standing in the atmosphere at 150 ° C. for 168 hours. Both are metal-coated polyethylene naphthalate substrates having a peel strength of 400 N / m or more .
(1) The centerline average roughness (Ra) of the surface of the polyethylene naphthalate-based film in contact with the base metal layer is 0.5 to 4 nm.
(2) The base metal layer contains 7 to 20% by mass of at least one metal selected from the group consisting of chromium, vanadium, titanium and molybdenum formed by a dry plating method , with the balance being nickel. a nickel alloy, and its thickness is 3 to 50 nm.   The metal-coated polyethylene naphthalate substrate according to claim 1, wherein the polyethylene naphthalate-based film has a thickness of 1 to 50 μm. The surface of at least one side of the polyethylene naphthalate film is subjected to a dry surface treatment so that the center line average roughness (Ra) is 0.5 to 4 nm, and then chromium is formed on the surface by a dry plating method. A base metal layer containing at least one metal selected from the group consisting of vanadium, titanium and molybdenum in an amount of 7 to 20% by mass with respect to the total amount, a remaining nickel alloy , and a thickness of 3 to 50 nm. formed, subsequently, metallized polyethylene naphthalate substrate manufacturing method according to claim 1 or 2, characterized in that laminating a copper coating layer on the lower ground metal layer. The method for producing a metal-coated polyethylene naphthalate substrate according to claim 3 , wherein the dry surface treatment is performed by subjecting to an ultraviolet irradiation treatment and / or a plasma treatment in an oxygen gas atmosphere. The method for producing a metal-coated polyethylene naphthalate substrate according to claim 3 or 4 , wherein the dry plating method is any one of a vacuum deposition method, a sputtering method, and an ion plating method. When laminating | stacking the said copper coating layer, first, a copper coating layer is formed by the dry-type plating method, Then, a copper coating layer is formed on it by the wet-plating method, The 3-5 of Claims 3-5 characterized by the above-mentioned. The manufacturing method of the metal-coated polyethylene naphthalate board | substrate in any one. The thickness of the said polyethylene naphthalate type | system | group film is 1-50 micrometers, The manufacturing method of the metal-coated polyethylene naphthalate board | substrate in any one of Claims 3-6 characterized by the above-mentioned.