JP6776087B2 - Manufacturing method of metal-clad laminate and manufacturing method of circuit board - Google Patents

Description

The present invention relates to a method for manufacturing a metal-clad laminate used for a circuit board such as a flexible circuit board (FPC) used for an electronic product, and a method for manufacturing a circuit board.

Since FPC has flexibility and potential for three-dimensional wiring, it is widely applied to electronic products such as computers and their peripheral devices, communication devices represented by smartphones, and the like. The FPC is manufactured by circuit processing a metal layer of a metal-clad laminate having a structure in which a metal layer and an insulating resin layer are laminated.

With the miniaturization of electronic devices, FPCs are becoming thinner, denser, and more multifunctional. However, when the metal-clad laminate, which is the raw material of FPC, is made thinner, its rigidity is lowered, so that the handling property is lowered in the manufacturing process of FPC, and defects such as breakage, damage, and peeling of the wiring layer due to bending occur. It is easy to occur. Since these defects reduce the yield and reliability of electronic products that use FPC, countermeasures are required.

In order to compensate for the decrease in rigidity of the metal-clad laminate, a method is used in which a carrier such as a PET film is attached to the metal-clad laminate with an adhesive, and the carrier is peeled off after processing the FPC. However, this method has a problem that the heat resistance and dimensional stability of the metal-clad laminate are impaired by the use of a carrier or an adhesive. Therefore, a method for manufacturing a circuit board in which a metal sheet is used as a carrier, a polyimide layer as an insulating resin layer and a metal layer are sequentially laminated and formed, the metal layer is circuit-processed, and then the metal sheet is peeled off is used. It has been proposed (for example, Patent Document 1). In the technique of Patent Document 1, since a metal sheet is used as a carrier, it may be difficult to identify the alignment mark formed on the metal layer via the carrier in the processing process of FPC.

A method has been proposed in which a new polyimide layer is formed by applying a polyamic acid solution on the polyimide layer of a metal-clad laminate to imidize it, and the polyimide layer is peeled off as a polyimide film (for example, Patent Document 2). However, Patent Document 2 merely uses a metal-clad laminate as a support for producing a polyimide film as a product, and is not a technique for producing a metal-clad laminate as a raw material for a circuit board.

Japanese Patent No. 5276950 (Fig. 1, Fig. 2, etc.) Japanese Patent No. 4260530 (Claim 1 and the like)

In the present invention, in order to cope with the thinning of a circuit board such as an FPC, even if the insulating resin layer of the metal-clad laminate is thinned, sufficient rigidity can be ensured and the handleability can be maintained. It is an object of the present invention to provide a method and a method for manufacturing a circuit board.

As a result of diligent studies, the present inventors have been able to solve the above problems by forming a removable polyimide layer by a casting method on the insulating resin layer side of the metal-clad laminate and using this as a support. The present invention was completed.

That is, in the method for producing a metal-clad laminate of the present invention, the first laminate in which the metal layer and the insulating resin layer are laminated and the insulating resin layer of the first laminate are detachably laminated. It is a method of manufacturing a metal-clad laminate provided with a support.
The method for manufacturing a metal-clad laminate of the present invention includes a step of preparing the first laminate and a step of preparing the first laminate.
A step of forming the support by applying a resin solution to the surface of the insulating resin layer of the first laminated plate, and
Including
The support is made of polyimide, and the resin solution is a polyimide solution or a polyamic acid solution.

In the step of forming the support in the method for producing a metal-clad laminate of the present invention, the polyamic acid solution may be applied and then heat-treated to imidize the polyamic acid.

In the method for producing a metal-clad laminate of the present invention, the insulating resin layer may be a polyimide layer made of polyimide as a resin component.

In the method for producing a metal-clad laminate of the present invention, the thickness of the insulating resin layer may be in the range of 1 to 20 μm.

The method for manufacturing a circuit board of the present invention includes a step of circuit-processing the metal layer in the metal-clad laminate manufactured by the method for manufacturing a metal-clad laminate to form a wiring layer.

The method for manufacturing a circuit board of the present invention may further include a step of forming a coverlay film layer covering the wiring layer.

The method for manufacturing a circuit board of the present invention may further include a step of separating the support.

In the method for manufacturing a metal-clad laminate of the present invention, the rigidity of the metal-clad laminate can be ensured by forming a removable polyimide support by a casting method, so that the insulating resin layer can be made as thin as possible. it can. That is, by providing the support, the rigidity is increased as compared with the state of the first laminated plate, and it is possible to prevent the occurrence of defects such as breakage, damage, and peeling of the wiring layer due to bending in the FPC manufacturing process. Therefore, the handleability when manufacturing the FPC using the thin metal-clad laminate is improved, and the thin FPC can be efficiently manufactured, for example, by the roll-to-roll method.

Further, according to the method for manufacturing a metal-clad laminate and the method for manufacturing a circuit board of the present invention, by forming the support from polyimide, it becomes easy to control the coefficient of linear thermal expansion of the support and the adhesive can be used. Since it is no longer necessary, the heat resistance and dimensional stability of the metal-clad laminate are not impaired. Further, unlike the case where a metal support is used, visibility is ensured through the support. Therefore, in the process of manufacturing the FPC using the metal-clad laminate, the alignment mark provided on the metal layer can be easily recognized, and the yield and reliability of the FPC itself and the electronic product using the FPC can be improved. it can.

It is a process drawing of the manufacturing method of the metal-clad laminated board of one Embodiment of this invention. It is a schematic cross-sectional view which shows one structural example of the insulating resin layer which constitutes a metal-clad laminate. It is a schematic cross-sectional view which shows another structural example of the insulating resin layer which constitutes a metal-clad laminate. It is a schematic cross-sectional view which shows still another structural example of the insulating resin layer which constitutes a metal-clad laminate. It is a process drawing of the manufacturing method of the circuit board of one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate.

[Manufacturing method of metal-clad laminate]
FIG. 1 is a process diagram of a method for manufacturing a metal-clad laminate according to an embodiment of the present invention. As shown in FIGS. 1 (a) and 1 (b), the metal-clad laminate 20 manufactured in the present embodiment includes a first laminate 10 in which a metal layer 101 and an insulating resin layer 102 are laminated, and a first laminate 10. A support 103 that is detachably laminated on the insulating resin layer 102 of the first laminated plate 10 is provided. The method for manufacturing the metal-clad laminate 20 of the present embodiment can include the following steps (I) and (II).

<Process (I)>
The step (I) is a step of preparing the first laminated board 10. As shown in FIG. 1A, the first laminated plate 10 is formed by laminating a metal layer 101 and an insulating resin layer 102.

(Metal layer)
It is preferable to use a metal foil for the metal layer 101 from the viewpoint of adhesiveness. Metal foil metals include, for example, copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth, indium or Examples thereof include metals selected from these alloys and the like. Particularly preferred in terms of conductivity is a copper or copper alloy metal foil. When the metal-clad laminate 20 is continuously produced, a long metal foil obtained by winding a metal foil having a predetermined thickness into a roll shape is used as the metal foil.

Further, the surface roughness of the surface of the metal layer 101 in direct contact with the insulating resin layer 102 is preferably 0.1 to 7 μm in Rz. This is because the adhesive strength with the insulating resin layer 102 becomes better within this range. Further, when Rz is 0.3 to 3.0 μm, it is more preferable because it is possible to achieve both a suitable adhesive force and a good etching property required at the time of forming a high-density wiring. Here, Rz indicates the ten-point average roughness defined in JIS B 0601 (1994).

(Insulating resin layer)
The insulating resin layer 102 is preferably a polyimide layer in which the resin component is polyimide. In this case, the polyimide layer may have a single-layer structure or a multi-layer structure in which a plurality of polyimide layers are laminated. When the insulating resin layer 102 has a multilayer structure, it may have a multilayer structure including a thermoplastic polyimide layer and a non-thermoplastic polyimide layer. Here, the "thermoplastic polyimide" is generally a polyimide in which the glass transition temperature (Tg) can be clearly confirmed, but in the present invention, it is measured using a dynamic viscoelasticity measuring device (DMA), 30 A polyimide having a storage elastic modulus at ° C. of 1.0 × 10 ⁹ Pa or more and a storage elastic modulus at 320 ° C. of less than 3.0 × 10 ⁸ Pa. The "non-thermoplastic polyimide" is a polyimide that generally does not soften or show adhesiveness even when heated. In the present invention, the storage elastic modulus at 30 ° C. measured by DMA is 1. A polyimide having a storage elastic modulus of 3.0 × 10 ⁸ Pa or more at 320 ° C. and 0 × 10 ⁹ Pa or more.

2A to 2C show a preferable configuration example of the insulating resin layer 102. First, in the example shown in FIG. 2A, the insulating resin layer 102 has adhesiveness to the thermoplastic polyimide layer 102A having adhesiveness and the non-thermoplastic polyimide layer 102B as the base resin layer from the side in contact with the metal layer 101. The thermoplastic polyimide layer 102C to have has a multilayer structure in which the thermoplastic polyimide layers 102C are laminated in this order. Here, the surface S1 of the thermoplastic polyimide layer 102C of the insulating resin layer 102 is the surface on the side on which the support 103 is laminated.

Next, in the example shown in FIG. 2B, in the insulating resin layer 102, the thermoplastic polyimide layer 102A and the non-thermoplastic polyimide layer 102B as the base resin layer are laminated in this order from the side in contact with the metal layer 101. It has a multi-layer structure. Here, the surface S1 of the insulating resin layer 102 in the non-thermoplastic polyimide layer 102B is the surface on the side on which the support 103 is laminated.

Next, in the example shown in FIG. 2C, the insulating resin layer 102 is formed of a single layer. When the insulating resin layer 102 is a single layer, it is preferable that the resin component is made of non-plastic polyimide. Here, the surface S1 of the insulating resin layer 102 is the surface on the side on which the support 103 is laminated.

In the examples shown in FIGS. 2A to 2C, it is preferable that all the polyimide layers constituting the insulating resin layer 102 are formed by a casting method in which a resin solution is applied onto the metal foil to be the metal layer 101. Further, in the examples shown in FIGS. 2A to 2B, the coefficient of linear thermal expansion of the non-thermoplastic polyimide layer 102B is 20 × 10 ^-6 (1 / K) or less, preferably 1 × 10 ^{-6 to} 17 × 10 ^-6. The range is preferably (1 / K). The same applies to the insulating resin layer 102 of FIG. 2C.

The thickness of the insulating resin layer 102 is preferably in the range of, for example, 1 to 20 μm, preferably in the range of 2 to 12 μm, from the viewpoint of realizing thinning of the circuit board such as FPC obtained by processing the metal-clad laminate 20. Is more preferable. If the thickness of the insulating resin layer 102 is less than 1 μm, functions such as electrical insulation may be impaired. If the thickness of the insulating resin layer 102 exceeds 20 μm, it becomes difficult to reduce the thickness of a circuit board such as an FPC.

The overall coefficient of linear thermal expansion of the insulating resin layer 102 is preferably as close as possible to the coefficient of linear thermal expansion of the metal layer 101. By making the overall coefficient of linear thermal expansion of the insulating resin layer 102 close to the coefficient of linear thermal expansion of the metal layer 101, it is possible to suppress the occurrence of warpage in the processing process of the FPC. From this point of view, in the metal-clad laminate 20, the coefficient of linear thermal expansion E1 of the entire insulating resin layer 102 and the coefficient of linear thermal expansion E2 of the metal layer 101 are, for example, 0.7 × E1 ≦ E2 ≦ 1. It is preferable to form the insulating resin layer 102 so as to have a relationship of 1 × E1.

Further, for example, when the metal layer 101 is made of copper foil, the coefficient of linear thermal expansion of the entire insulating resin layer 102 is preferably 15 × ^10-6 regardless of whether it is a single layer or a multi-layer. It is in the range of ~ 30 × 10 ^-6 (1 / K), more preferably in the range of 18 × 10 ^{-6 to} 25 × 10 ^-6 (1 / K). When the overall coefficient of linear thermal expansion of the insulating resin layer 102 is out of the above range, in step (I) (step of obtaining the first laminated plate 10), the warp of the widthwise end portion of the first laminated plate 10 is caused. It becomes large and tends to hinder stable production. Further, even after the first laminated plate 10 and the support 103 are laminated in the subsequent step (II), the warp of the end portion in the width direction is likely to be folded inward, which may hinder stable production. There is. When the insulating resin layer has a multilayer structure including a thermoplastic polyimide and a non-thermoplastic polyimide, the linear expansion coefficient of the thermoplastic polyimide is preferably 40 × 10 ^-6 (1 / K) or more, and the non-thermoplastic. The linear expansion coefficient of polyimide is preferably 20 × 10 ^-6 (1 / K) or less.

The overall storage elastic modulus of the insulating resin layer 102 is from the viewpoint of ensuring the rigidity of the metal-clad laminate 20 and preventing the occurrence of defects such as breakage, damage, and peeling of the wiring layer due to bending in the processing process of FPC. For example, the range of 3.0 × 10 ^{9 to} 12.0 × 10 ⁹ Pa is preferable, and the range of 4.0 × 10 ^{9 to} 9.0 × 10 ⁹ Pa is more preferable.

(Filler)
The insulating resin layer 102 may contain a filler regardless of whether it is a single layer or a multi-layer. For example, in the structure illustrated in FIG. 2A, 0.5 to 10 fillers 105 are added to the polyimide constituting the thermoplastic polyimide layer 102C located on the outermost layer (layer having the surface S1) on the side where the support 103 is laminated. It is preferably contained in the range of% by weight, and more preferably in the range of 2 to 6% by weight. In this case, if the content of the filler 105 in the thermoplastic polyimide layer 102C is less than 0.5% by weight, there is a problem that the insulating resin layer adheres to the smooth surface of the apparatus and it becomes difficult to transport the FPC. May occur. On the other hand, if the content of the filler 105 exceeds 10% by weight, the unevenness of the surface becomes large and the smoothness is impaired in appearance, or the adhesion at the lamination boundary with the support 103 becomes strong, and the support 103 is separated. At that time, even if the separation becomes impossible or the separation is possible, the circuit board is stretched at the time of separation and warpage is likely to occur. The filler 105 may be distributed throughout the insulating resin layer 102. For example, in the structure illustrated in FIG. 2A, the thermoplastic polyimide layer 102A and the non-thermoplastic polyimide layer 102B may also contain the filler 105. Although not shown, the insulating resin layer 102 illustrated in FIGS. 2B and 2C can also contain the filler 105.

Examples of the material of the filler 105 include silica, alumina, and aluminum nitride, and among these, silica is preferable. The shape of the filler 105 is preferably spherical rather than crushed from the viewpoint of uniformity of dispersion in the resin. Furthermore, it is more preferable that the average particle size of the filler 105 is 0.5 to 10 μm. The spherical shape means a true sphere or a rounded particle state having substantially no corners, and the crushed shape means a particle state having an arbitrary shape with corners possessed by the crushed particles. , Can be confirmed with an electron microscope or other microscope.

For example, when the insulating resin layer 102 is formed by the casting method, the filler 105 is mixed in a polyimide solution or a polyamic acid solution in advance, and casting is performed in the insulating resin layer 102 (or a part of the polyimide layer thereof). ) Can be contained.

<Process (II)>
The step (II) is a step of forming the support 103 as shown in FIG. 1 (b) by applying the resin solution to the surface S1 of the insulating resin layer 102 of the first laminated plate 10 having the above structure. Is. That is, in the step (II), the support 103 is formed by the casting method.
Since the support 103 is composed of polyimide in the step (II), a polyimide solution or a polyamic acid solution is used as the resin solution. That is, in the step (II), the surface S1 of the insulating resin layer 102 of the first laminated plate 10 may be coated with a polyamic acid solution and then heat-treated to be imidized to form the support 103. Alternatively, the support 103 may be formed by applying the surface S1 of the insulating resin layer 102 of the first laminated plate 10 in the form of a solution in which a pre-imidized polyimide is dissolved in a solvent and drying the mixture. The raw material acid anhydride and diamino compound used for forming the support 103 are not particularly limited, but as will be described later, the raw material acid anhydride and the polyimide raw material for forming the insulating resin layer 102 and The same as the diamino compound can be used. Further, when the insulating resin layer 102 is formed, the solvent used for forming the support 103, the heat treatment temperature for drying and imidization, the heat treatment method, the concentration of the resin solution, the coating method on the insulating resin layer 102, and the like are also used. Can be done in the same way as.

The support 103 formed in the step (II) has an effect of imparting thickness to the metal-clad laminate 20 and increasing its rigidity. By having the support 103, the metal-clad laminate 20 has more excellent mechanical properties than the state without the support 103 (the state of the first laminate 10). Therefore, the metal-clad laminate 20 is subjected to breakage of the wiring layer due to bending in the FPC processing process including wet process processing such as exposure, development, etching, and plating processing, and processing in a high temperature region such as baking and high-speed pressing. It is possible to prevent the occurrence of problems such as damage and peeling.

The thickness of the support 103 is, for example, 5 to 50 μm from the viewpoint of increasing the rigidity of the metal-clad laminate 20 and preventing the occurrence of defects such as breakage, damage, and peeling of the wiring layer due to bending in the FPC processing process. The range is preferably within the range, and more preferably within the range of 10 to 25 μm. If the thickness of the support 103 is less than 5 μm, it becomes difficult to impart sufficient rigidity and supportability to the metal-clad laminate 20, and if the thickness exceeds 50 μm, the polyimide material used for the support 103 increases. It leads to cost increase.

From the same viewpoint, in the metal-clad laminate 20, the total thickness of the insulating resin layer 102 and the support 103 is preferably in the range of 10 to 60 μm, more preferably in the range of 20 to 30 μm. That is, when the insulating resin layer 102 is formed to be relatively thin (for example, to a thickness of 1 to 5 μm) in relation to the thickness of the insulating resin layer 102 described above, a relatively support is provided so as to complement it. It is preferable to form 103 thickly (for example, to a thickness of 25 to 50 μm). On the contrary, when the insulating resin layer 102 is formed to be relatively thick (for example, to a thickness of 15 to 20 μm), the support 103 can be formed to be relatively thin (for example, to a thickness of 5 to 10 μm).

In the present embodiment, by forming the support 103 from polyimide, heat resistance in heat treatment in the manufacturing process of FPC can be ensured, and the coefficient of linear thermal expansion of the support 103 is set to the entire line of the insulating resin layer 102. Since it becomes easy to control so as to approximate the coefficient of thermal expansion, it is possible to surely suppress the occurrence of warpage in the processing process of FPC. From this point of view, in the metal-clad laminate 20, the coefficient of linear thermal expansion E1 of the entire insulating resin layer 102 and the coefficient of linear thermal expansion E3 of the support 103 are, for example, 0.9 × E1 ≦ E3 ≦ 1. It is preferable to form the insulating resin layer 102 and the support 103 so as to have a relationship of 1 × E1. From the same viewpoint, in the metal-clad laminate 20, the coefficient of linear thermal expansion E2 of the metal layer 101 and the coefficient of linear thermal expansion E3 of the support 103 are, for example, 0.7 × E3 ≦ E2 ≦ 1.1 × E3. It is preferable to form the insulating resin layer 102 so as to have the above relationship.

(Polyimide)
Next, the polyimide for forming the insulating resin layer 102 and the support 103 will be described. Polyimide is obtained by imidizing a polyamic acid which is a precursor, and is produced by reacting a specific acid anhydride with a diamino compound. Therefore, by explaining the acid anhydride and the diamino compound, the polyimide can be prepared. Specific examples are understood. The term polyimide in the present invention means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazolimide, in addition to polyimide.

The diamino compound which is a polyimide material, the aromatic diamino compound, such as can be used aliphatic diamino compounds, e.g., aromatic diamino compound represented by NH ₂ -Ar1-NH ₂ can be mentioned as suitable. Here, Ar1 is selected from the groups represented by the following formulas, and the substitution position of the amino group is arbitrary, but the p and p'positions are preferable. Ar1 may have a substituent, but preferably does not, or if it does, the substituent is a lower alkyl or lower alkoxy group having 1 to 6 carbon atoms. Only one of these aromatic diamino compounds may be used, or two or more thereof may be used in combination.

Examples of the tetracarboxylic acid compound to be reacted with the diamino compound include aromatic tetracarboxylic acid and its acid anhydride, esterified product, and halide, but aromatic tetracarboxylic acid compound is preferable, and polyamic acid is synthesized. The acid anhydride is preferred in terms of ease. The aromatic tetracarboxylic acid compound is not particularly limited, but for example, a compound represented by O (CO) ₂ Ar2 (CO) ₂ O is preferable. Here, Ar @ 2 is preferably a tetravalent aromatic group represented by the following formula, although the substitution position of an acid anhydride group [(CO) 2 _O] is optional, the position of symmetry is preferred. Ar2 may have a substituent, but preferably does not have it, or if it does, the substituent is preferably a lower alkyl group having 1 to 6 carbon atoms.

As illustrated in FIG. 2A, the insulating resin layer 102 can have a multilayer structure including the thermoplastic polyimide layers 102A and 102C and the non-thermoplastic polyimide layer 102B, and is therefore used for each of the thermoplastic polyimide and the non-thermoplastic polyimide. Preferred examples of the acid anhydride and the diamino compound will be described. The same applies to the case where a thermoplastic polyimide or a non-thermoplastic polyimide is used for forming the support 103.

Thermoplastic polyimide:
When the polyimide is a thermoplastic polyimide, a diamino compound containing 50 mol% or more of 4,4'-diaminodiphenyl ether (DAPE) is used as a diamino component, and this and an acid anhydride are used. Those obtained by reaction are preferable. By containing 50 mol% or more of DAPE, the peelability between the thermoplastic polyimide layer 102C and the support 103 is improved, and the risk of the circuit board being stretched and warped at the time of separation is suppressed. A more preferred content of DAPE is in the range of 70-100 mol%.

When the polyimide is a thermoplastic polyimide, it is not particularly limited, but contains 50 mol% or more of 3,3', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) as an acid anhydride component. It is preferable that the acid anhydride is obtained by reacting it with a diamino compound. By containing 50 mol% or more of BTDA, the peelability between the thermoplastic polyimide layer 102C and the support 103 is improved, and the risk of the circuit board being stretched and warped at the time of separation is suppressed. A more preferred content of BTDA is in the range of 70-100 mol%. In addition, among preferable aromatic tetracarboxylic acid compounds, those other than BTDA include, for example, biphenyltetracarboxylic acid anhydride (BPDA), pyromellitic acid anhydride (PMDA), 3,3', 4,4'-diphenyl. It is preferably sulfonetetracarboxylic dianhydride (DSDA) and 4,4′-oxydiphthalic anhydride (ODPA) or a combination thereof. Only one kind of these tetracarboxylic acid compounds may be used, or two or more kinds may be used in combination.

Non-thermoplastic polyimide:
When the polyimide is a non-thermoplastic polyimide, the diamino compound is not particularly limited, but as the diamino compound, the aromatic diamino compound represented by NH _2- Ar1-NH ₂ is used as in the case of the above-mentioned thermoplastic polyimide. , The one obtained by reacting with a tetracarboxylic acid compound is preferable. However, the coefficient of linear thermal expansion of the non-thermoplastic polyimide layer 102B should be in the range of 20 × ^10-6 (1 / K) or less, preferably 1 × ^{10-6 to} 17 × ^10-6 (1 / K). It is often preferable to select a suitable aromatic diamino compound in order to achieve this condition. For example, a compound obtained by reacting a diamino compound containing 50 mol% or more of 4,4'-diamino-2,2'-dimethylbiphenyl (m-TB) with a tetracarboxylic acid compound is preferable. Further, it is more preferable to select a diamino compound containing 70 mol% or more.

When the polyimide is a non-thermoplastic polyimide, the tetracarboxylic acid compound is not particularly limited, but the same compound as in the case of the above-mentioned thermoplastic polyimide can be used. A more preferable aromatic tetracarboxylic dian compound in order to have a linear thermal expansion coefficient of 20 × ^10-6 (1 / K) or less, preferably in the range of 1 × ^{10-6 to} 17 × ^10-6 (1 / K). Is biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) or a combination thereof.

In the above thermoplastic polyimide and non-thermoplastic polyimide, the linear thermal expansion coefficient is selected by selecting the types of acid anhydride and diamino compound and the molar ratio of each when two or more kinds of acid anhydride and diamino compound are applied. , Storage elasticity, glass transition temperature, etc. can be controlled. In the present embodiment, the material of the insulating resin layer 102 and the support 103 is made of polyimide formed by the casting method, so that the orientation of the polyimide molecules of the support 103 is changed to the orientation of the polyimide molecules of the insulating resin layer 102. It becomes possible to approach the properties, and it becomes easy to control the linear thermal expansion coefficient and storage elasticity of each layer, the adhesiveness between layers, and the peel strength. From this point of view, it is also preferable to use the same type of acid anhydride and diamino compound used for forming the insulating resin layer 102 and the support 103.
In the above-mentioned thermoplastic polyimide and non-thermoplastic polyimide, when a plurality of structural units of polyimide are present, they may exist as blocks or randomly, but they preferably exist randomly.

For the polyimide constituting the insulating resin layer 102 and the support 103, for example, the above diamino compound and tetracarboxylic dianhydride are mixed in a solvent at a ratio of approximately equal moles, and the reaction temperature is in the range of 0 to 200 ° C. It can be obtained by preferably reacting in the range of 0 to 100 ° C. to obtain a resin solution of polyamic acid, which is further imidized. As the solvent, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, Examples thereof include dioxane, tetrahydrofuran, jiglime and triglime.

Usually, the polyamic acid is synthesized in a reaction vessel or the like before being applied to the metal foil to be the metal layer 101. For example, in step (I), a polyimide layer can be obtained by applying a resin solution of polyamic acid on the metal layer 101 and drying to form a polyamic acid layer, and then imidizing the polyamic acid layer by heat treatment. Overlapping, the coating may be repeated on the already formed polyamic acid layer or on the polyimide layer. Alternatively, in step (I), the insulating resin layer 102 may be formed by applying the pre-imidized polyimide in the form of a solution dissolved in a solvent to the surface of the metal foil to be the metal layer 101 and drying the mixture. Good.
Similarly, in step (II), a resin solution of polyamic acid is applied and dried on the surface S1 of the insulating resin layer 102 to form a polyamic acid layer, and the polyimide layer is imidized by a subsequent heat treatment to form a polyimide layer. Obtainable. Overlapping, the coating may be repeated on the already formed polyamic acid layer or on the polyimide layer. Alternatively, in step (II), the support 103 may be formed by applying the surface S1 of the insulating resin layer 102 in the form of a solution in which a pre-imidized polyimide is dissolved in a solvent and drying the mixture.

When the insulating resin layer 102 or the support 103 has a multi-layer structure, in the step (I), it is sequentially placed on the metal foil that becomes the metal layer 101, and in the step (II), it is sequentially placed on the surface S1 of the insulating resin layer 102. A method of forming a plurality of polyamic acid resin layers and then collectively imidizing them to form an insulating resin layer 102 or a support 103 is preferable, but the method is not limited thereto. That is, a plurality of polyamic acid resin layers are collectively applied to the metal foil or insulating resin layer 102 to be the metal layer 101 by a multilayer die or the like, dried, and then imidized by heat treatment. A plurality of polyimide layers may be formed in the above, or a plurality of resin layers of polyamic acid may be sequentially applied and then dried and imidized all at once. Further, the polyimide layer may be formed one by one by sequentially applying and drying a plurality of polyamic acid resin solutions to imidization. In forming the plurality of polyimide layers, each of these treatments can be arbitrarily combined.

The method of applying the polyimide solution or the polyamic acid solution on the metal foil to be the metal layer 101 or on the surface S1 of the insulating resin layer 102 is not particularly limited, and for example, a coater such as a comma, a die, a knife, or a lip is used. It is possible to apply. When forming the multilayer polyimide layer, a method of repeatedly applying a polyimide solution (or a polyamic acid solution) to the substrate and drying the substrate is preferable.

As a method for drying and heat imidization treatment, any method such as a batch treatment method or a continuous treatment method can be selected. In the batch processing method, a resin solution of polyamic acid is applied to a long metal foil, and then the laminate is wound into a roll in a non-imidized state in a hot air drying furnace that can be set to a predetermined temperature. This is a method of completing imidization by allowing the resin to stand for a certain period of time and finally heat-treating at a high temperature of 200 ° C. or higher. In the continuous treatment method, after applying a resin solution of polyamic acid to a long metal foil, it is continuously moved in a drying furnace to secure a predetermined heat treatment time, and finally the temperature is raised to 200 ° C. or higher. This is a method of performing heat treatment. Any method may be selected from the viewpoints of productivity, yield, etc., but for the purpose of preventing oxidation of the metal layer 101, heat treatment at a high temperature of 200 ° C. or higher is performed in a reducing gas atmosphere under a reduced pressure environment. It is preferable to carry out under or under a reducing gas atmosphere and a reduced pressure environment. The solvent of the polyamic acid resin is removed and imidized by heating in the drying and imidization treatment steps. At this time, if a rapid heat treatment is performed at a high temperature, a skin layer is formed on the resin surface and the solvent is formed. Is difficult to evaporate and foaming occurs. Therefore, it is preferable to perform the heat treatment while gradually raising the temperature from a low temperature to a high temperature. Further, in the heating imidization step, it is preferable to finally heat-treat at a temperature of 300 to 400 ° C.

The concentration of the polyamic acid resin solution applied on the surface S1 of the metal foil or the insulating resin layer 102 to be the metal layer 101 is preferably 5 to 30% by weight, although it depends on the degree of polymerization of the polyamic acid as a polymer. It is preferably 10 to 20% by weight. If the polymer concentration is 5% by weight or more, a sufficient film thickness can be obtained by one application, and if it is 30% by weight or less, the viscosity of the resin solution does not become too high, and the resin solution can be applied uniformly and smoothly. Because.

In the metal-clad laminate 20 obtained as described above, the first laminate 10 constituting the metal-clad laminate 20 can be separated from the support 103 by mechanical force. The peel strength (peeling strength) required to separate the metal-clad laminate 20 into the first laminate 10 and the support 103 is preferably in the range of, for example, 1 to 50 N / m, and is preferably 5 to 5. It is more preferably in the range of 30 N / m, and further preferably in the range of 5 to 20 N / m. If the peel strength is less than 1 N / m, peeling at the lamination boundary between the insulating resin layer 102 and the support 103 is likely to occur due to a mechanical external force in the FPC manufacturing process. If the peel strength exceeds 50 N / m, the first laminated plate 10 and the support 103 cannot be separated from each other, or even if the peeling is possible, the first laminated plate 10 is stretched and warped at the time of separation. It will be easier. The adhesive strength / peel strength between the insulating resin layer 102 and the support 103 of the first laminated plate 10 depends on the type and ratio of the raw material monomers of the respective polyimides constituting the insulating resin layer 102 and the support 103, the heat treatment conditions, and the like. Can be controlled. It is preferable that the insulating resin layer 102 and the support 103 are separated after the circuit is processed, as will be described later.

[Manufacturing method of circuit board]
FIG. 3 is a process diagram of a method for manufacturing a circuit board according to an embodiment of the present invention. The method for manufacturing the metal-clad laminate 20 of the present embodiment includes at least the following steps (I) to (III), and further includes steps (IV) and steps (V) as arbitrary steps. be able to. Therefore, the circuit board manufactured in this embodiment may have the embodiment shown in any of FIGS. 3 (b) to 3 (d). That is, as shown in FIG. 3B, a circuit board in which a support 103 and an insulating resin layer 102 are laminated, and a wiring layer 101A in which a metal layer 101 is circuit-processed is included on the insulating resin layer 102. It may be 30. Further, as shown in FIG. 3C, the circuit board 40 may be further provided with the coverlay film layer 104 covering the wiring layer 101A of the circuit board 30. Further, as shown in FIG. 3D, the circuit board 50 may be in a state where the support 103 is separated from the circuit board 40.

<Process (I), (II)>
In the method for manufacturing the circuit board of the present embodiment, the steps (I) and (II) are the same as the steps (I) and (II) in the above-mentioned "method for manufacturing the metal-clad laminate". (Fig. 1 is also used).

<Process (III)>
In this step, as shown in FIGS. 3A and 3B, the metal layer 101 of the metal-clad laminate 20 obtained in the step (II) is circuit-processed to form the wiring layer 101A. This is a step of manufacturing the circuit board 30. The circuit processing of the metal layer 101 can be performed by a conventional method, and is not particularly limited. For example, for patterning the metal layer 101, a method of combining known photolithography technology and etching, a nanoimprint technology, or the like can be adopted.

<Process (IV)>
In this step, as shown in FIGS. 3 (b) and 3 (c), a circuit is formed by forming a coverlay film layer 104 that covers the wiring layer 101A of the circuit board 30 obtained in the step (III). This is a step of manufacturing the substrate 40. The coverlay film layer 104 can be formed by a conventional method, and is not particularly limited. For example, by using a film of a thermosetting resin such as an epoxy resin or a polyimide resin processed into a predetermined shape according to the pattern of the wiring layer 101A and laminating it so as to cover the wiring layer 101A by a thermocompression bonding method. The coverlay film layer 104 can be formed. Thermocompression bonding can be performed by a known thermocompression pressing method. In the present embodiment, the coverlay film layer 104 is formed with the support 103. By thermocompression bonding the film to be the coverlay film layer 104 with the support 103 provided, the thermal shrinkage of the insulating resin layer 102 is suppressed, and the dimensional change of the wiring layer 101A formed on the insulating resin layer 102 is changed. It can be suppressed and the dimensional accuracy of the wiring layer 101A can be maintained.

In the circuit board 40 obtained as described above, the insulating resin layer 102 and the support 103 constituting the circuit board 40 can be separated by mechanical force. The peel strength (peeling strength) required for peeling the support 103 from the circuit board 40 is preferably in the range of 1 to 50 N / m, and preferably in the range of 5 to 30 N / m. More preferably, it is in the range of 5 to 20 N / m. If the peel strength is less than 1 N / m, peeling at the lamination boundary between the insulating resin layer 102 and the support 103 is likely to occur due to a mechanical external force in the FPC manufacturing process. If the peel strength exceeds 50 N / m, the insulating resin layer 102 and the support 103 cannot be separated from each other, or even if the peel strength can be peeled off, the circuit board 50 is stretched and warped easily. The insulating resin layer 102 and the support 103 can be separated in the next step (V).

<Process (V)>
This step is a step of separating the support 103 from the circuit board 40 obtained in the step (IV) to form the circuit board 50. In this case, the surface S1 of the insulating resin layer 102 and the surface S2 of the support 103 are separated from each other. That is, the surfaces S1 and S2 are peeled surfaces.
As shown in FIGS. 3C and 3D, a circuit including the insulating resin layer 102, the wiring layer 101A, and the coverlay film layer 104 by separating the support 103 and the insulating resin layer 102. The substrate 50 can be manufactured. In this way, the circuit processing is performed with the support 103 provided, and the support 103 is separated after the circuit processing to improve the dimensional accuracy of the wiring layer 101A when the circuit board 50 is particularly long. The effect of maintaining is increased. Therefore, it is preferable that at least each step before the step of peeling the support 103 and the insulating resin layer 102 to produce the circuit board 50 is performed by the roll-to-roll method. Even if the support 103 is peeled off, the coverlay film layer 104 is formed in the previous step (IV), so that the rigidity of the circuit board 50 is ensured, and the wiring layer is broken or damaged due to bending. It is possible to prevent the occurrence of problems such as peeling.

In the above description, only the characteristic steps of the method of the present invention have been described. That is, when manufacturing the circuit boards 30, 40, 50, steps other than the above, such as through-hole processing in the pre-process, terminal plating in the post-process, and outer shape processing, are performed according to a conventional method. The explanation is omitted because it can be done. Further, the circuit boards 30, 40, 50 are made of nickel, cobalt, chromium, molybdenum, silicon, or the like in order to secure the adhesion between the insulating resin layer 102 and the wiring layer 101A. It may have a metal as a main component, an ultrathin layer of an alloy thereof, a thermoplastic resin layer, or the like).

As described in detail above, according to the method for manufacturing the metal-clad laminate and the method for manufacturing the circuit board of the present embodiment, the removable polyimide is supported on the insulating resin layer 102 side of the first laminate 10. By forming the body 103 by the casting method, the rigidity of the metal-clad laminate 20 can be ensured, so that the insulating resin layer 102 can be made as thin as possible. That is, by providing the support 103, the rigidity becomes higher than that of the first laminated plate 10, and it is possible to prevent the occurrence of defects such as breakage, damage, and peeling of the wiring layer 101A due to bending in the FPC manufacturing process. it can. Therefore, the handleability when manufacturing the FPC using the metal-clad laminate 20 is improved, and for example, a thin-layer FPC can be efficiently manufactured by a roll-to-roll method.

Further, according to the method for manufacturing the metal-clad laminate and the method for manufacturing the circuit board of the present embodiment, the linear thermal expansion coefficient of the support 103 can be easily controlled by forming the support 103 from polyimide. Since no adhesive is required, the heat resistance and dimensional stability of the metal-clad laminate 20 are not impaired. Further, unlike the case where a metal support is used, visibility is ensured through the support 103. In particular, when the insulating resin layer 102 and the support 103 are both made of polyimide and the insulating resin layer 102 and the support 103 are both formed by the casting method, the orientation of the polyimide molecules of the support 103 is determined. The orientation of the polyimide molecule of the insulating resin layer 102 can be approached. Therefore, sufficient visibility is ensured via the support 103, and in the process of manufacturing the FPC using the metal-clad laminate 20, the alignment mark provided on the metal layer 101 can be easily recognized, and the FPC itself. And the yield and reliability of electronic products using FPC can be improved.

Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified in the examples of the present invention, various measurements and evaluations are as follows. The abbreviations used in this example are as described above.

[Measurement of coefficient of linear thermal expansion]
To measure the coefficient of linear thermal expansion, use a thermomechanical analyzer (manufactured by Seiko Instruments Inc.) to raise the temperature to 255 ° C at a rate of 20 ° C / min, hold at that temperature for 10 minutes, and then further 5 ° C / min. Cooled at a constant rate. The average coefficient of thermal expansion (linear thermal expansion coefficient) from 240 ° C. to 100 ° C. during cooling was calculated.

(Synthesis Example 1)
In a nitrogen-substituted reaction vessel, 308.00 g of N, N-dimethylacetamide was placed, and 27.14 g (0.066 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added in the vessel. It was dissolved while stirring with. Next, 14.86 g (0.068 mol) of pyromellitic dianhydride was added. Then, stirring was continued for 3 hours to prepare a resin solution a of a polyamic acid having a solution viscosity of 2,850 mPa · s (hereinafter, also referred to as a thermoplastic polyimide precursor a).

(Synthesis Example 2)
297.50 g of N, N-dimethylacetamide was placed in a nitrogen-substituted reaction vessel. In this reaction vessel, 25.27 g (0.119 mol) of 4,4'-diamino-2,2'dimethylbiphenyl was dissolved with stirring in the vessel. Next, 6.87 g (0.023 mol) of 3,3'-4,4'-biphenyltetracarboxylic dianhydride and 20.36 g (0.093 mol) of pyromellitic dianhydride were added. .. Then, stirring was continued for 3 hours to prepare a resin solution b of polyamic acid having a solution viscosity of 21,000 mPa · s (hereinafter, also referred to as non-thermoplastic polyimide precursor b).

[Example 1]
<Preparation of single-sided flexible copper-clad laminate>
The thermoplastic polyimide precursor a prepared in Synthesis Example 1 was uniformly applied to one side of a long rolled copper foil (thickness 12 μm), and then heated and dried at 130 ° C. to remove the solvent. Next, the non-thermoplastic polyimide precursor b prepared in Synthesis Example 2 was uniformly coated on the coated surface side, and dried by heating at 130 ° C. to remove the solvent. Next, the thermoplastic polyimide precursor a prepared in Synthesis Example 1 is uniformly coated on the coated surface side, dried at 130 ° C., and then heat-cured to 380 ° C. over about 10 minutes to insulate the copper foil. A copper-clad laminate A1 composed of a polyimide layer a1 (thickness 12 μm) as a resin layer was prepared. The coefficient of linear thermal expansion of the polyimide layer a1 at this time was 23 ppm / K. The thickness of the thermoplastic polyimide precursor a after curing was 1 μm.

<Formation of supporting base material>
The non-thermoplastic polyimide precursor b prepared in Synthesis Example 2 is uniformly applied to the surface of the copper-clad laminate A1 on the insulating resin layer side, dried at 130 ° C., and then heat-cured to 380 ° C. over about 10 minutes. By doing so, a copper-clad laminate B1 having a polyimide layer b1 (thickness 25 μm) as a supporting base material was prepared. The coefficient of linear thermal expansion of the polyimide layer b1 at this time was 23 ppm / K.

<Preparation of circuit wiring board>
The copper foil of the copper-clad laminate B1 with a supporting base material was etched to prepare a circuit wiring board A1 having a pitch of 50 μm.

A coverlay film (manufactured by Nikkan Kogyo Co., Ltd., trade name: Nikaflex, base film thickness 25 μm, adhesive layer thickness 25 μm) was attached to the wiring side surface of the circuit wiring board A1 with a support base material, and the temperature was 160 ° C. for 1 hour. The circuit wiring board B1 in which the coverlay film was laminated was prepared by the heating press of. The support base material of the circuit wiring board B1 was peeled off to prepare the circuit wiring board C1.

Although the embodiments of the present invention have been described in detail for the purpose of illustration, the present invention is not limited to the above embodiments. For example, in the above embodiment, the mode in which the support 103 is separated from the circuit board 40 after the coverlay film layer 104 is provided is shown, but the mode in which the support 103 is separated at the stage of the circuit board 30 is also present. It is included in the scope of the invention.

10 ... 1st laminate, 20 ... Metal-clad laminate, 30, 40, 50 ... Circuit board, 101 ... Metal layer, 101A ... Wiring layer, 102 ... Insulating resin layer, 102A ... Thermoplastic polyimide layer, 102B ... Non Thermoplastic polyimide layer, 102C ... Thermoplastic polyimide layer, 103 ... Support, 104 ... Coverlay film layer, 105 ... Filler, S1, S2 ... Surface

Claims (6)

A metal-clad laminate comprising a first laminate in which a metal layer and an insulating resin layer are laminated, and a support detachably laminated on the insulating resin layer of the first laminate is manufactured. Process and
A step of forming a wiring layer by circuit processing the metal layer in the manufactured metal-clad laminate.
It is a manufacturing method of a circuit board including
The process of manufacturing the metal-clad laminate is
The step of preparing the first laminated board and
A step of forming the support by applying a resin solution to the surface of the insulating resin layer of the first laminated plate, and
Including
A method for producing a circuit board, wherein the support is made of polyimide and the resin solution is a polyimide solution or a polyamic acid solution. The method for manufacturing a circuit board according to claim 1, wherein in the step of forming the support, the polyamic acid solution is applied and then heat-treated to imidize the polyamic acid. The method for manufacturing a circuit board according to claim 1 or 2, wherein the insulating resin layer is a polyimide layer made of polyimide as a resin component. The method for manufacturing a circuit board according to any one of claims 1 to 3, wherein the thickness of the insulating resin layer is in the range of 1 to 20 μm. The method for manufacturing a circuit board according to claim 1 , further comprising a step of forming a coverlay film layer covering the wiring layer. The method for manufacturing a circuit board according to claim 1 or 5 , further comprising a step of separating the support.

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