Method for manufacturing printed wiring board

Abstract

[Problem] To provide a method for manufacturing a printed wiring board in which adhesion between an insulating layer and traces can be improved further. [Solution] A metal foil 12 with a roughened surface is stacked on an insulating layer 11, and then heat and pressure are applied thereon to form a laminated sheet 13. Subsequently, the metal foil 12 is removed using an etching solution to expose the insulating layer 11. Thereafter, a heat treatment is applied to the insulating layer 11. Next, , electroless plating is performed on the roughened surface of the insulating layer 11 to form an electroless plating layer 16, a resist pattern is formed, an electroplating layer is formed, after which the resist pattern is stripped, and the exposed portion of the electroless plating layer 16 is etched away to form a trace pattern.

Description

Printed wiring board manufacturing method

[0001] The present invention relates to a method for manufacturing a printed wiring board using a laminate in which a metal foil having a surface roughened is laminated on at least one surface of an insulating layer.

[0002] In recent years, printed wiring boards, which are widely used in electronic devices, communication devices, personal computers, and the like, have become increasingly dense, highly integrated, and lighter and thinner. Conventionally, a method for forming circuits on printed wiring boards has been known, for example, through the semi-additive process. In the semi-additive process, for example, the surface of an insulating layer is roughened by resin etching such as desmearing, and then the roughened surface is subjected to electroless plating to form a seed layer. A resist pattern is then formed thereon corresponding to non-circuit areas, and a circuit is formed by plating. This semi-additive process is suitable for forming fine circuits.

[0003] Recently, instead of roughening the surface of an insulating layer by resin etching such as desmearing, a method has been proposed in which a roughened metal foil is laminated on the surface of the insulating layer and the roughened shape of the metal foil is transferred to the insulating layer to roughen it (see, for example, Patent Document 1). This method does not require optimization of the conditions for roughening the insulating layer by desmearing or the like, and can easily roughen the insulating layer, while also forming a roughened surface with higher adhesion than when roughening by desmearing or the like.

[0004] International Publication WO2022 / 039062

[0005] However, in order to cope with the trend toward higher density and higher precision of printed wiring boards, there is a demand for further improvement in the adhesion between the insulating layer and the wiring.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a method for manufacturing a printed wiring board that can further improve the adhesion between an insulating layer and wiring.

[0007] The present invention is as follows: [1] A method for manufacturing a printed wiring board, comprising: a laminate forming step of laminating a metal foil having a roughened surface on at least one surface of an insulating layer, and applying heat and pressure to form a laminate; an insulating layer exposing step of removing the metal foil from the laminate using an etching solution to expose the insulating layer; a heat treatment step of applying heat treatment to the insulating layer after the insulating layer exposing step; an electroless plating step of applying electroless plating to the roughened surface of the insulating layer after the heat treatment step to form an electroless plated layer; a photoresist film laminating step of laminating a photoresist film on the surface of the electroless plated layer; a resist pattern forming step of exposing and developing the photoresist film to form a resist pattern; an electrolytic plating step of applying electrolytic plating to the electroless plated layer through the resist pattern to form an electrolytic plated layer; a resist pattern peeling step of peeling off the resist pattern; and a wiring pattern forming step of etching away the portion of the electroless plated layer exposed by peeling off the resist pattern to form a wiring pattern. [2] The method for manufacturing a printed wiring board according to [1], wherein the heating step is performed at a heating temperature of 100°C or higher and 200°C or lower for a heating time of 30 minutes or higher and 600 minutes or lower. [3] The method for manufacturing a printed wiring board according to [1] or [2], wherein the laminate formation step includes: a curing step of forming a non-through hole from the metal foil to the inner layer circuit by forming the insulating layer from a material containing a thermosetting resin, and arranging the insulating layer and the metal foil in this order on an inner layer substrate having an inner layer circuit formed thereon, and applying heat and pressure to harden the insulating layer; and a non-through hole forming step of forming a non-through hole from the metal foil to the inner layer circuit. [4] The method for manufacturing a printed wiring board according to [1] or [2], wherein the laminate formation step includes: a curing step of forming the insulating layer from a prepreg or a resin sheet in which a base material is impregnated with or coated with a thermosetting resin composition, and laminating the metal foil on at least one side of the insulating layer, and applying heat and pressure to harden the insulating layer; and a through hole forming step of forming a through hole that penetrates the insulating layer and the metal foil.

[0008] According to the present invention, after the insulating layer exposing step, the insulating layer is subjected to a heat treatment, which can increase the adhesion between the insulating layer and the wiring, thereby improving the formability of a fine wiring pattern.

[0009] In particular, a higher effect can be obtained by setting the heating temperature in the heat treatment step to 100° C. or higher and 200° C. or lower and the heating time to 30 minutes or higher and 600 minutes or lower.

[0010] 1 is a diagram showing each step of a method for manufacturing a printed wiring board according to a first embodiment of the present invention; FIG. 2 is a diagram showing each step following FIG. 1; FIG. 3 is a diagram showing each step of a method for manufacturing a printed wiring board according to a second embodiment of the present invention; and FIG. 4 is a diagram showing each step following FIG.

[0011] Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0012] 1 and 2 illustrate steps in a method for manufacturing a printed wiring board according to a first embodiment of the present invention. First, for example, a metal foil 12 having a roughened surface is laminated on at least one side of an insulating layer 11, followed by heating and pressure to form a laminate 13 (laminate formation process). Specifically, as shown in FIG. 1A , the laminate formation process includes a curing process in which the insulating layer 11 is made of a material containing a thermosetting resin, the insulating layer 11 and the metal foil 12 are placed in this order on an inner layer substrate 14 having an insulating substrate 14A and an inner layer circuit 14B formed thereon, and the insulating layer 11 is cured by heating and pressure. The insulating layer 11 and the metal foil 12 may be laminated on both sides of the inner layer substrate 14, or on only one side.

[0013] The inner layer substrate 14 can be manufactured by a conventionally known method. To explain an example of the manufacturing process for the inner layer substrate 14, first, through holes (not shown) are formed in an insulating substrate 14A made of a resin substrate such as a glass epoxy or polyimide resin, and then electrolytic copper plating is performed on both the top and bottom surfaces of the insulating substrate 14A and the inner surfaces of the through holes using electroless copper plating as a base. Next, a resist pattern is formed on the surface, and a conductor pattern and through-hole conductors are formed as the inner layer circuit 14B by etching, and the cavities in the through-hole conductors are filled with a filling resin such as epoxy to flatten the surface.

[0014] Before laminating the insulating layer 11 and the metal foil 12 on the inner layer substrate 14, it is preferable to roughen the surface of the inner layer substrate 14, specifically the surface of the inner layer circuit 14B, for example, by etching or the like.

[0015] The insulating layer 11 can be formed, for example, from an insulating prepreg or resin sheet containing a thermosetting resin. Examples of prepregs include those obtained by impregnating or coating a substrate, such as a fibrous reinforcing material such as glass cloth or carbon fiber, with a thermosetting resin composition containing a thermosetting resin mixed with additives such as a curing agent and a coloring agent, and then semi-curing the prepreg. Examples of resin sheets include those obtained by semi-curing a thermosetting resin composition containing a thermosetting resin mixed with additives such as a curing agent and a coloring agent. Examples of thermosetting resins used in prepregs or resin sheets include polyimide resins, epoxy compounds, cyanate ester compounds, maleimide compounds, phenolic compounds, polyphenylene ether compounds, benzoxazine compounds, organic group-modified silicone compounds, and compounds having polymerizable unsaturated groups. The prepreg or resin sheet constituting the insulating layer 11 is cured by heating in a curing process.

[0016] The metal foil 12 of this embodiment preferably has a surface roughness Rz of 2.0 μm or less on at least one side, as measured in accordance with JIS B0601 1994. The surface roughness Rz of the metal foil 12 is more preferably 1.8 μm or less, even more preferably 1.5 μm or less, and may even be 1.0 μm or less. Furthermore, while a surface roughness Rz of more than 0 μm is practical, it is preferably 0.2 μm or more, and more preferably 0.5 μm or more. By setting the surface roughness Rz of the metal foil 12 to the lower limit or greater, adhesion between the insulating layer 11 and the plating layer tends to be further improved. Furthermore, by setting the surface roughness Rz to the upper limit or less, the time required for the process of removing the metal foil 12 by etching tends to be further shortened. Furthermore, the time required for the flash etching process (e.g., etching in which part of the electroless plating layer 16 is etched to expose the insulating layer 11 in the wiring pattern formation process described below) can be further shortened, which tends to facilitate the formation of a wiring pattern with smaller lines and spaces.

[0017] The thickness of the metal foil 12 is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, even more preferably 1.2 μm or more, and may be 1.5 μm or more. The thickness of the metal foil 12 is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, and may be 2.5 μm or less, or 2.0 μm or less. By making the thickness of the metal foil 12 equal to or greater than the lower limit, handleability tends to be improved. By making the thickness equal to or less than the upper limit, the time required for the process of removing the metal foil 12 by etching can be further shortened, thereby reducing the manufacturing cost of the printed wiring board.

[0018] The metal constituting the metal foil 12 is at least one metal selected from copper, aluminum, nickel, titanium, iron, gold, silver, platinum, tin, zinc, tantalum, molybdenum, niobium, and other alloys, and copper is preferred. Examples of copper foil include rolled copper foil and electrolytic copper foil. The metal foil 12 may also be subjected to various surface treatments on its surface, which has a surface roughness Rz of 2.0 μm or less. Examples of such treatments include roughening treatment, heat-resistant treatment, rust-proofing treatment, and silane coupling agent treatment. The metal foil 12 may be subjected to any one of these treatments or a combination of two or more of them. When two or more of the above treatments are performed, the order of roughening treatment, heat-resistant treatment, rust-proofing treatment, and silane coupling agent treatment is preferred. These treatments can be any known surface treatment for metal foils. The surface roughening treatment of the metal foil 12 only needs to be performed on at least the surface on the insulating layer 11 side. The roughening treatment of the metal foil 12 may be, for example, electrolytic roughening treatment.

[0019] The laminate 13 can be formed, for example, by placing the insulating layer 11 on the inner layer substrate 14, placing the metal foil 12 thereon, and then heating and pressurizing the laminate. In this case, the metal foil 12 may be placed alone, or a metal foil with a carrier support may be used, with the metal foil 12 placed on the insulating layer 11, and the carrier support may be peeled off to form the laminate. Alternatively, the laminate 13 may be formed, for example, using a resin-layered metal foil in which an insulating resin layer containing a thermosetting resin is formed on the metal foil 12, or a composite sheet in which an insulating resin layer containing a thermosetting resin is formed on the metal foil 12 of a metal foil with a carrier support, with the resin layer serving as the insulating layer 11 being placed against the inner layer substrate 14, and then heating and pressurizing the laminate. Examples of materials constituting the resin layer include those similar to the prepreg or resin sheet described above. The method for providing the metal foil 12 on the surface of the resin sheet is not particularly limited, and can be achieved, for example, by applying a solution (varnish) of a thermosetting resin dissolved in a solvent to the metal foil 12 and drying it. Examples of application methods include a gravure coater, a bar coater, a die coater, a doctor blade, and a baker applicator.

[0020] In this embodiment, it is preferable to provide the metal foil 12 on the surface of the resin layer using a metal foil with a carrier support, which is a laminate of the metal foil 12 and a carrier support. Specifically, for example, a thin copper foil with a carrier copper foil, which has a thickness of 1.5 μm and a surface roughness Rz of 2 μm or less as the metal foil 12 and a carrier copper foil with a thickness of 18 μm as the carrier support, is arranged on the surface of the insulating layer 11 made of a prepreg, a resin sheet, or the like so that the surface of the metal foil 12 with a surface roughness Rz of 2 μm or less is in contact with the surface of the insulating layer 11, and after laminate molding, the carrier copper foil is removed, thereby providing the metal foil 12 on the surface of the insulating layer 11.

[0021] Examples of the carrier support include metal foil and resin film, with metal foil being preferred and copper foil being more preferred. When the carrier support is copper foil, it is often referred to as carrier copper foil. For resin films, the description in paragraph 0031 of WO 2017 / 086418 can be referred to, the contents of which are incorporated herein by reference. The thickness of the carrier support is, for example, 5 μm or more, preferably 8 μm or more, and 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less. The carrier support-attached metal foil 12 may have other layers (such as an adhesive layer, a release layer, a roughening treatment layer, a heat-resistant treatment layer, a rust-proofing treatment layer, or a silane coupling agent treatment layer) provided between the carrier support and the metal foil 12.

[0022] The heating temperature in the curing step is, for example, preferably 150°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher. The heating temperature is, for example, preferably 350°C or lower, more preferably 300°C or lower, and even more preferably 250°C or lower. The applied pressure in the curing step is, for example, preferably 1.0 MPa or higher, more preferably 1.5 MPa or higher, and even more preferably 2.0 MPa or higher. The applied pressure is, for example, preferably 5.0 MPa or lower, more preferably 4.5 MPa or lower, and even more preferably 4.0 MPa or lower. As a result, the roughened shape of the metal foil 12 is transferred and cured on the surface of the insulating layer 11 against which the metal foil 12 is abutted.

[0023] The thickness of the insulating layer 11 is, for example, 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and even more preferably 25 μm or more. It is also preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, and particularly preferably 35 μm or less. By setting the thickness at or above the lower limit, insulation reliability tends to improve. Furthermore, by setting the thickness at or below the upper limit, product thickness tends to be reduced.

[0024] The laminate forming process may also include, after the curing process, a non-through hole forming process in which, for example, as shown in Fig. 1(B) , non-through holes 15 are formed from the metal foil 12 to the inner layer circuits 14B. In the non-through hole forming process, for example, holes are drilled in the metal foil 12 and the insulating layer 11 by laser processing using a carbon dioxide laser or the like to form the non-through holes 15 that reach the inner layer circuits 14B. Thereafter, as necessary, wet desmearing such as etching, or dry desmearing by plasma treatment or UV treatment is performed to remove smears remaining in the non-through holes 15.

[0025] After the laminate formation step, for example, as shown in Fig. 1(C), the metal foil 12 is removed from the laminate 13 using an etching solution to expose the insulating layer 11 (insulating layer exposing step). Etching can be performed by known methods such as spraying or swing immersion. Examples of the etching solution include hydrogen peroxide, sulfuric acid, persulfates, organic acids, hydrochloric acid, and cupric chloride.

[0026] After the insulating layer exposing step, the exposed insulating layer 11 is subjected to a heat treatment (heat treatment step). This is because it can improve the adhesion between the insulating layer 11 and the wiring formed thereon. In this embodiment, the inclusion of the heat treatment step improves the adhesion between the insulating layer 11 and the electroless plating layer 16 (described later), even when a metal foil 12 with a small surface roughness Rz is used. This improves the adhesion between the formed wiring pattern 19 and the insulating layer 11, thereby presumably resulting in a finer wiring pattern 19 than conventionally formed. Furthermore, since the wiring pattern 19 can be formed on the insulating layer 11 with a small surface roughness derived from the metal foil, it is also advantageous in that a semiconductor device with low electrical transmission loss and low energy loss can be obtained. In the heat treatment step, the heating temperature is preferably, for example, 100°C or higher and 200°C or lower, and more preferably 120°C or higher and 180°C or lower. If the heating temperature is too low, the insulating layer will not dry sufficiently, and if it is too high, decomposition of the resin component of the insulating layer will proceed. In the heat treatment step, the heating time is preferably, for example, from 30 minutes to 600 minutes, and more preferably from 60 minutes to 400 minutes. If the heating time is too short, the insulating layer will not be sufficiently dried, and if it is too long, decomposition of the resin component of the insulating layer 11 will proceed.

[0027] After the heat treatment step, for example, as shown in Fig. 1(D), electroless plating is performed on the roughened surface of the insulating layer 11 to which the roughened shape of the metal foil 12 has been transferred, to form an electroless plated layer 16 (electroless plating step). At that time, if non-through holes 15 are formed in the insulating layer 11 by the non-through hole forming step described above, the electroless plated layer 16 is also formed on the inner walls of the non-through holes 15.

[0028] In this embodiment, even if the electroless plated layer 16 is formed without performing a roughening treatment on the surface of the insulating layer 11 after etching and removing the metal foil 12, it is possible to form an electroless plated layer 16 with excellent adhesion to the insulating layer 11, and thus an electrolytic plated layer 18, which will be described in detail below. This simplifies the manufacturing process and significantly reduces the environmental impact in the method for manufacturing a printed wiring board. In this embodiment, drying is preferably performed after the electroless plating process to remove any encapsulated moisture. As for drying conditions after the electroless plating process, any drying conditions sufficient to remove moisture are effective, but heating at 100°C to 170°C for 1 hour to 5 hours is more preferred. Such drying not only removes moisture but also further improves adhesion between the insulating layer 11 and the metal layer (electroless plated layer 16 and / or wiring pattern 19). The electroless plating is preferably copper electroless plating.

[0029] After the electroless plating step, a photoresist film is laminated on the surface of the electroless plated layer 16 by thermocompression bonding a dry film (photoresist film lamination step). The compression temperature is, for example, 50° C. to 140° C., and the compression pressure is, for example, 1 kgf / cm. ２ ~15kgf / cm ２ The pressure bonding time is preferably set to, for example, 5 to 300 seconds.

[0030] Next, as shown in FIG. 2(E), the photoresist film is exposed and developed to form a resist pattern 17 (resist pattern formation process). The resist pattern 17 is formed, for example, corresponding to the area from which the electroless plating layer 16 is removed in the etching process described below. During exposure, active energy rays are irradiated onto predetermined portions of the photoresist film, curing the irradiated areas. The active energy rays may be irradiated through a mask pattern, or a direct writing method may be used in which the active energy rays are directly irradiated. The active energy rays are not particularly limited, but examples include ultraviolet light, visible light, electron beams, and X-rays. It is desirable to select an appropriate active energy ray depending on the type of resist. The development is not particularly limited, but developers such as alkaline aqueous solutions, aqueous developers, and organic solvents are used as long as they selectively dissolve the unexposed portions. Development methods can be performed using known methods, such as spraying, swing immersion, brushing, and scraping.

[0031] Next, as shown in FIG. 2(F), electrolytic plating is applied to the electroless plated layer 16 via the resist pattern 17 to form an electrolytic plated layer 18 (electrolytic plating step). The electrolytic plating is preferably copper electrolytic plating. Next, the resist pattern 17 is stripped (resist pattern stripping step). Thereafter, as shown in FIG. 2(G), the portions of the electroless plated layer 16 exposed by the stripping of the resist pattern 17 are removed by etching to expose the insulating layer 11, thereby forming a wiring pattern 19 (wiring pattern formation step). After forming the wiring pattern 19, it is preferable to perform a heat treatment at 150°C to 200°C for 20 to 90 minutes. This is because this can further improve and stabilize the adhesion between the wiring pattern 19 and the insulating layer 11.

[0032] As described above, according to this embodiment, after the insulating layer exposing step, the insulating layer is subjected to a heat treatment, thereby improving the adhesion between the insulating layer and the wiring, and improving the formability of fine wiring patterns.

[0033] In particular, a higher effect can be obtained by setting the heating temperature in the heat treatment step to 100° C. or higher and 200° C. or lower and the heating time to 30 minutes or higher and 600 minutes or lower.

[0034] 3 and 4 show the steps of a method for manufacturing a printed wiring board according to a second embodiment of the present invention. The method for manufacturing a printed wiring board according to this embodiment includes the same steps as those of the first embodiment, except for the specific step in the laminate formation step in which a metal foil 22 having a roughened surface is laminated on at least one surface of an insulating layer 21, and then heated and pressed to form a laminate 23.

[0035] 3A, the laminate formation process in this embodiment includes a curing process in which an insulating layer 21 is formed from a prepreg or a resin sheet in which a base material is impregnated with or coated with a thermosetting resin composition, a metal foil 22 having a roughened surface is laminated on at least one surface of the insulating layer 21, and the insulating layer 21 is cured by heating and pressurizing. The configurations of the prepreg or resin sheet and the metal foil 22, as well as the heating temperature and pressure in the curing process, are the same as those in the first embodiment. The thicknesses of the insulating layer 21 and the metal foil 22 are also the same as those in the first embodiment.

[0036] The laminate forming step in this embodiment may also include, after the curing step, a through-hole forming step of forming through-holes 24 that penetrate the insulating layer 21 and the metal foil 22, as shown in Fig. 3(B) . In the through-hole forming step, the through-holes 24 are formed by laser processing using a carbon dioxide laser or the like. Thereafter, as necessary, wet desmearing such as etching, or dry desmearing using plasma treatment or UV treatment is performed to remove smears remaining in the through-holes 24.

[0037] After the laminate formation process, for example, similar to the first embodiment, an insulating layer exposing process (see FIG. 3(C)), a heat treatment process, an electroless plating process (see FIG. 3(D)), a photoresist film laminating process, a resist pattern forming process (see FIG. 4(E)), an electrolytic plating process (see FIG. 4(F)), a resist pattern peeling process, and a wiring pattern forming process (see FIG. 4(G)) are performed.

[0038] Specifically, as shown in FIG. 3C, the metal foil 22 is first removed from the laminate 23 using an etching solution to expose the insulating layer 21 (insulating layer exposing step). Next, the exposed insulating layer 21 is subjected to a heat treatment (heat treatment step). Next, as shown in FIG. 3D, the roughened surface of the insulating layer 21 to which the roughened shape of the metal foil 22 has been transferred is subjected to electroless plating to form an electroless plated layer 25 (electroless plating step). Next, a photoresist film is laminated on the surface of the electroless plated layer 25 by thermocompression bonding a dry film (photoresist film laminating step). Next, as shown in FIG. 4E, the photoresist film is exposed and developed to form a resist pattern 26 (resist pattern forming step). Next, as shown in FIG. 4F, electrolytic plating is applied to the electroless plated layer 25 through the resist pattern 26 to form an electrolytic plated layer 27 (electrolytic plating step). Next, the resist pattern 26 is peeled off (resist pattern peeling step). 4(G), the portions of the electroless plating layer 25 exposed by the peeling of the resist pattern 26 are removed by etching to form the wiring pattern 28 (wiring pattern forming step). The specific conditions for each step are the same as those in the first embodiment.

[0039] In this embodiment, as in the first embodiment, the insulating layer is subjected to a heat treatment after the insulating layer exposure step, thereby increasing the adhesion between the insulating layer and the wiring and improving the formability of fine wiring patterns.

[0040] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation, etc., measurements can be made using other instruments with equivalent performance. In the following examples, the heating temperature and pressure applied are the set temperature and set pressure of the instruments.

[0041] Example 1 A test piece was prepared as follows.

[0042] <Laminate Forming Step / Curing Step (See FIG. 1(A))> A glass cloth-based BT resin copper-clad laminate (conductor thickness 12 μm, thickness 0.1 mm, HL832NS manufactured by Mitsubishi Gas Chemical Company, Inc.) was prepared as the inner layer substrate 14, and its surface was roughened. Specifically, first, as a pretreatment, the inner layer substrate 14 was cleaned with a residue remover (CA5330 manufactured by MEC Co., Ltd.), and after rinsing with water, the copper surface was roughened with a microetching agent (CZ8101 manufactured by MEC Co., Ltd.), and after rinsing with water, it was rust-prevented with a rust inhibitor (CL8300 manufactured by MEC Co., Ltd.), and then rinsed with water and dried.

[0043] After roughening the surface of the inner layer substrate 14, a prepreg (thickness: 0.015 mm: manufactured by Mitsubishi Gas Chemical Company, Inc., product name: GHPL-830NS SP68) made by impregnating a base material made of glass cloth (glass fiber) with bismaleimide triazine resin (BT resin) and bringing it to a B-stage (semi-cured state) was placed on top of the inner layer substrate 14 (both the front and back sides) as the insulating layer 11. The prepreg had an 18 μm thick carrier copper foil (thickness: 2 μm, surface roughness Rz: 1.3 μm: manufactured by Mitsui Mining & Smelting Co., Ltd., product name: MT18FL) and contained a metal foil 12 whose surface had been roughened. The laminate 13 was produced by laminating these components in a vacuum press under conditions of a pressure of 2.5±0.2 MPa, a temperature of 220±2°C, and a holding time of 60 minutes.

[0044] <Insulating Layer Exposing Step (See FIG. 1(C))> The carrier copper foil on the surface of the produced laminate 13 was peeled off, and the copper foil serving as the metal foil 12 was removed using an etching solution. The etching solution used was CPE-770D (manufactured by Mitsubishi Gas Chemical Company, Inc.), and copper etching was performed at a solution temperature of 35°C. The liquid composition of the etching solution CPE-770D contained water, 2.1 w / v % hydrogen peroxide, 4 w / v % sulfuric acid, and 2.6 w / v % alcohol as an auxiliary agent.

[0045] <Heat Treatment Step> After the insulating layer exposing step, a heat treatment was performed on the exposed insulating layer 11. Specifically, the laminate 13 from which the metal foil 12 had been removed was treated at a temperature of 100°C for 30 minutes using a heat treatment device.

[0046] <Electroless Plating Step (See FIG. 1(D))> After the heat treatment step, the laminate 13 from which the metal foil 12 had been removed was racked on a plating jig, and electroless copper plating was performed on the roughened surface of the insulating layer 11 using an apparatus manufactured by Almex Technologies Co., Ltd. that is capable of immersing and oscillating in an electroless copper plating bath, thereby forming an electroless plated layer 16 having a thickness of 0.4 μm.

[0047] <Electrolytic Plating Step (See FIG. 2(F))> After the electroless plating step, electrolytic copper plating was performed to form an electrolytic plated layer 18 having a thickness of 18 μm, thereby obtaining a test piece.

[0048] Example 2 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was performed at a temperature of 100° C. for 60 minutes.

[0049] Example 3 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was performed at a temperature of 100° C. for 360 minutes.

[0050] Example 4 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was performed at a temperature of 130° C. for 30 minutes.

[0051] Example 5 A test piece was obtained in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 130° C. for 60 minutes.

[0052] Example 6 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was performed at a temperature of 130° C. for 360 minutes.

[0053] Example 7 A test piece was obtained in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 130° C. for 600 minutes.

[0054] Example 8 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was performed at a temperature of 150° C. for 60 minutes.

[0055] Example 9 A test piece was obtained in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 180° C. for 60 minutes.

[0056] Example 10 A test piece was obtained in the same manner as in Example 1, except that the heat treatment was carried out at a temperature of 200° C. for 60 minutes.

[0057] Comparative Example 1 A test piece was obtained in the same manner as in Example 1, except that the heat treatment step was not carried out.

[0058] (Characteristics Evaluation) The characteristics of Examples 1 to 10 and Comparative Example 1 were measured by the following methods.

[0059] [Evaluation of Peel Strength] The peel strength of each test piece was measured to determine its strength. Peel strength was measured by fixing the lower layer of the test piece to a plate or the like, pulling the edge of the plating layer perpendicular to the fixing plate direction, and measuring the load required for peeling. The results are shown in Table 1.

[0060]

[0061] As shown in Table 1, in the evaluation of peel strength, Examples 1 to 10 had higher peel strength than Comparative Example 1. In other words, it was found that by performing a heat treatment step after the insulating layer exposing step and before the electroless plating step, it is possible to increase the wiring adhesion strength resulting from the peel strength, and improve the formability of a fine wiring pattern.

[0062] It can be used in the manufacture of printed wiring boards.

[0063] 11...insulating layer, 12...metal foil, 13...laminated board, 14...inner layer substrate, 14A...insulating board, 14B...inner layer circuit, 15...blind hole, 16...electroless plated layer, 17...resist pattern, 18...electrolytic plated layer, 19...wiring pattern, 21...insulating layer, 22...metal foil, 23...laminated board, 24...through hole, 25...electroless plated layer, 26...resist pattern, 27...electrolytic plated layer, 28...wiring pattern

Claims

1. A method for manufacturing a printed wiring board, comprising: a laminate formation step of laminating a metal foil having a roughened surface on at least one surface of an insulating layer, and applying heat and pressure to form a laminate; an insulating layer exposing step of removing the metal foil from the laminate using an etching solution to expose the insulating layer; a heat treatment step of applying heat treatment to the insulating layer after the insulating layer exposing step; an electroless plating step of applying electroless plating to the roughened surface of the insulating layer after the heat treatment step to form an electroless plated layer; a photoresist film laminating step of laminating a photoresist film on the surface of the electroless plated layer; a resist pattern formation step of exposing and developing the photoresist film to form a resist pattern; an electrolytic plating step of applying electrolytic plating to the electroless plated layer via the resist pattern to form an electrolytic plated layer; a resist pattern peeling step of peeling off the resist pattern; and a wiring pattern formation step of etching away the portion of the electroless plated layer exposed by peeling off the resist pattern to form a wiring pattern.

2. The method for manufacturing a printed wiring board according to claim 1, characterized in that in the heat treatment step, the heating temperature is 100°C or higher and 200°C or lower, and the heating time is 30 minutes or higher and 600 minutes or lower.

3. The method for manufacturing a printed wiring board according to claim 1 or 2, characterized in that the laminate formation process comprises: a curing process in which the insulating layer is made of a material containing a thermosetting resin, the insulating layer and the metal foil are arranged in this order on an inner layer substrate on which an inner layer circuit is formed, and heat and pressure are applied to harden the insulating layer; and a blind hole formation process in which blind holes are formed from the metal foil to reach the inner layer circuit.

4. The method for manufacturing a printed wiring board according to claim 1 or claim 2, characterized in that the laminate formation process comprises: a curing process in which the insulating layer is formed from a prepreg or a resin sheet in which a thermosetting resin composition is impregnated or applied to a base material, the metal foil is laminated on at least one surface of the insulating layer, and the insulating layer is cured by heating and pressurizing; and a through-hole formation process in which through-holes that penetrate the insulating layer and the metal foil are formed.

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