JPH11135942A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a printed wiring board, wherein a wiring top can be ensured of enough width without deteriorating the surface of a copper foil in adhesion to a solder resist. SOLUTION: A prepreg 2 and an outer copper foil 3 are laminated on both the sides of an inner board 1 where an inner circuit is provided and thermocompressed into one piece, a through-hole 4 is provided in the laminate so as to electrically connect the inner circuit to the outer copper foil, a thermosetting resin layer on the inner wall of the through-hole 4 is roughened, the inner wall of the through-hole and the surface of the outer copper foil are plated, the surface of the outer copper foil is turned smooth by mechanical polishing, and plating resists 5 are formed. The laminate is dipped into an acidic solution making air blow into the solution and subjected to solder plating 6, the plating resists 5 are removed, a part of the board 1 which is not plated with solder is selectively removed by etching with alkali etchant, the solder plating is removed, solder resists 8 are printed and cured, and then an Ni/Au plating 9 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a multilayer printed wiring board.

[0002]

2. Description of the Related Art With the development of electronic equipment, printed wiring boards are required to have a high wiring density, and miniaturization of wiring is one of the major technical problems. As a method of manufacturing such a printed wiring board, a subtractive method is used in which a copper-clad laminate in which a copper foil is bonded to an insulating base material is used as a starting material, and a portion of the copper foil that is not a circuit conductor is removed by etching to form a circuit. In general, the additive method of forming a circuit by performing electroless plating on the required circuit shape on the surface of the insulating base, the partial additive method of forming a part of the circuit conductor such as the inner wall of the through hole by electroless plating, etc. Are known.

[0003] Above all, the subtractive method has been used for a long time. In order to improve the wiring density, it is usually performed by reducing the thickness of the copper foil of the copper-clad laminate. The reason for this is that when an etching resist is formed in the required circuit shape on the surface of the copper foil, and the copper foil on which the etching resist is not formed is removed by etching with an etching solution, the circuit exposed from the etching resist as the etching progresses. A phenomenon called so-called side etch in which copper is corroded from the side of the copper foil to be formed occurs, and the copper foil on the side close to the etching resist is side-etched,
Since the side near the insulating substrate is hardly etched, the thicker the copper foil, the more the copper on the side to be removed by side etching must be increased, so the distance between the circuits on the insulating substrate side cannot be secured. This is because the width of the circuit conductor cannot be reduced and it is difficult to form a fine circuit.

After the wiring is formed, a solder resist is usually formed as a solder resist.
In order to obtain the adhesion between the copper surface and the solder resist, the surface is roughened by, for example, a jet scrub treatment, and the solder resist is formed on the surface.

[0005]

By the way, in the conventional manufacturing method, polishing such as jet scrubbing is performed after the wiring is formed, and therefore, the corner portion (top) of the outermost surface (hereinafter referred to as top) of the circuit conductor. Corner), the top width is reduced, the terminal width cannot be secured for component mounting, and there is a problem that a connection failure occurs during mounting.

If a roughening step such as a jet scrub treatment is omitted to secure the top width of the wiring, the adhesion between the copper foil surface and the solder resist is reduced due to the small unevenness of the copper surface, resulting in heat resistance. However, in the manufacturing process, the adhesive strength does not decrease. However, heating such as the subsequent semiconductor mounting process and soldering of electronic components and the product pressure cooker test (hereinafter, PCT)
That. ) Caused a problem that the adhesion between the solder resist and the circuit conductor was reduced.

Further, if the amount of etching is reduced to secure the top width in consideration of the reduction of the top width in a polishing process such as a jet scrub process, the amount of etching on the base material side is also reduced, resulting in a short circuit. However, when the conditions of the polishing step are relaxed, abrasive particles adhere to the copper foil, and there is a problem that insulation reliability decreases and plating failure occurs.

An object of the present invention is to provide a method of manufacturing a printed wiring board which can secure a top width of a wiring without lowering the adhesion between the surface of a copper foil and a solder resist.

[0009]

A method of manufacturing a multilayer printed wiring board according to the present invention is characterized in that the following steps are performed in this order. a. A step of laminating a prepreg on an inner layer plate on which an inner layer circuit has been formed in advance, laminating an outer layer copper foil on an outermost layer, and applying heat and pressure to laminate and integrate. b. A step of forming a through hole for connecting the inner layer circuit and the outer layer copper foil of the laminated and integrated substrate by a drill; c. The thermosetting resin layer on the wall surface of the formed through hole is roughened using a roughening agent, and the inner wall of the through hole and the surface of the outer layer copper foil are plated to electrically connect the inner layer circuit and the outer layer copper foil. Step of performing. d. A step of forming a plating resist by flattening the surface of the plated outer copper foil by mechanical polishing. e. A step of immersing the substrate on which the plating resist is formed while blowing air into an acidic solution. f. A process of performing solder plating on a substrate. g. Removing the plating resist from the substrate. h. A step of selectively etching away portions of the substrate that have not been solder plated with an alkaline etchant; i. Removing the solder plating from the substrate. j. A process of printing and curing a solder resist on a substrate. k. Forming Ni / Au plating on the substrate;

Step a can be replaced by the following steps. a1. The outer layer copper foil has a roughness suitable for adhesion to a resin, a copper layer having a thickness of 1 to 9 μm as a circuit, and a thickness of 10 to 150 μm having sufficient strength for handling as a whole metal layer. Using a composite metal foil in which two layers can be easily peeled off, using a composite metal foil that can easily be peeled off, stacking the copper layer to be a circuit so that the roughened surface is in contact with the prepreg, and heating and pressurizing to laminate and integrate. a2. Step of peeling and removing only carrier layer

Step a can be replaced by the following steps. a3. A first copper layer having a thickness of 1 to 9 μm which has a roughness suitable for bonding to a resin on the outer layer copper foil and a circuit having a thickness of 10 to 9 μm which has sufficient strength to be handled as a metal layer as a whole; Using a composite metal foil composed of a second copper layer having a thickness of 70 to 70 μm and a nickel-phosphorus alloy layer having a thickness of 0.04 to 1.5 μm provided between the two layers, heat-pressing and laminating and integrating Process. a4. Step of removing only second copper layer a5. Removing only the nickel-phosphorus alloy layer;

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Step a) To form an inner layer circuit in advance,
A copper-clad laminate, in which copper foil is attached to both sides of an insulating substrate used for ordinary printed wiring boards, such as an insulating substrate impregnated with epoxy resin in glass cloth or phenol resin in paper. Unnecessary portions of the copper foil are removed by etching. The etching solution used in this step may be a cupric chloride etching solution or a ferric chloride etching solution. On the inner layer plate on which the inner layer circuit is thus formed,
A prepreg of the same quality as that of the copper-clad laminate is laminated, an outer copper foil is laminated on the outermost layer, and the laminate is integrated by heating and pressing. The lamination conditions at this time vary depending on the type and thickness of the base material. Generally, if the epoxy resin is used, 160 to
190 ° C., 2.0 to 4.0 MPa, about 60 to 90 minutes, and 200 to 25 if a polyimide resin is used.
0 ° C., 2.0 to 4.0 MPa, about 60 to 90 minutes.

(Steps a1 and a2) The outer copper foil used in steps a1 and a2, which can be used in place of step a, has a roughness suitable for bonding to the resin on the outer layer copper foil and has a thickness of 1 to 9 μm to be a circuit. Copper layer having a thickness of 10 to 150 μm having sufficient strength for handling as a metal layer as a whole
m, a commercially available composite metal foil composed of a carrier layer having a carrier layer of 70 μm.
m, a double copper foil (made by Furukawa Circuit Foil Co., Ltd., trade name) having a circuit copper layer of 5 μm. If the copper foil handled in this process is very thin, it may break or wrinkle in the handling process, so use a composite metal foil consisting of a thin copper foil and a carrier to make handling easier, Forming a circuit by laminating the carrier and processing the thin copper foil after lamination on the inner circuit board enables finer processing of the circuit conductor.

(Steps a3, a4, a5) The outer copper foil used in steps a3, a4, and a5, which can be used in place of step a, has a roughness suitable for bonding to an outer layer copper foil and a circuit. A first copper layer having a thickness of 1 to 9 μm, a second copper layer having a thickness of 10 to 70 μm having sufficient strength for handling as a metal layer as a whole, and provided between the two layers. As a composite metal foil composed of a nickel-phosphorus alloy layer having a thickness of 0.04 to 1.5 μm, for example,
A nickel-phosphorus alloy layer is formed to a thickness of 0.2 μm on a roughened surface of a usual commercially available copper foil having a thickness of 15 μm (roughened surface roughness Ra: 0.3 μm) as a second copper layer. It is formed by plating, and the first is formed by electroplating on the nickel-phosphorus alloy layer.
Is formed with a thickness of 5 μm, and the surface of the first copper copper is roughened by electroplating with a surface roughness Ra: 0.6 μm suitable for bonding with a resin. By using such a composite metal foil, a metal layer having different etching conditions is sandwiched between intermediate layers in order to facilitate the handling of the above-described thin copper foil and to facilitate the chemical removal of carrier copper by etching. Also, in the case of a physically peelable carrier, in the handling process, scratches and foreign matter may be generated on the copper foil surface, and in order to prevent this, use a composite metal foil with high adhesion, For the removal, a metal layer having a chemical removal condition different from that of the circuit conductor is used. By the way, if such a metal layer is thick, it is not economical and the process becomes long. Therefore, an intermediate layer may be provided at a position where etching is to be stopped. As a solution for etching and removing only the second copper layer, a solution containing chlorine ions, ammonium ions, and copper ions (hereinafter, referred to as an alkali etchant) is used. The processing method is
It is carried out by contact with a solution such as dipping or spraying. Further, in the step of removing only the nickel-phosphorus alloy layer,
In a liquid containing nitric acid and hydrogen peroxide as main components, an organic acid having a carboxyl group as an additive, and -NH as a ring member
It is carried out by immersing in an aqueous solution containing a nitrogen-containing heterocyclic compound in the form of-, -N =, or by spraying such an aqueous solution.

(Step b) A through hole for connecting the inner layer circuit and the outer layer copper foil is formed at a predetermined position by using an NC drill machine used for a normal printed wiring board so as to connect the outer layer and the inner layer. .

(Step c) As the roughening agent for roughening the thermosetting resin layer on the wall surface of the through hole, any material can be used as long as it swells and dissolves the resin. It is preferred to use an aqueous acid solution. Thereafter, plating is performed to electrically connect the circuit conductor of the inner layer circuit board and the copper foil, and this plating uses the same technology as through-hole plating of a normal wiring board. That is, a plating nucleus substance such as palladium is attached to the roughened resin layer, and is brought into contact with an ionized plating metal and a complexing agent for the plating metal, and an electroless plating solution having a reducing agent for the plating metal. Then, plating is deposited on the nucleus, and plating metal is deposited on the entire wall to which the substance serving as the nucleus is attached. By performing plating in this manner, the copper foil of the outer layer, the side wall of the through hole, and the circuit conductor of the inner layer plate can be electrically connected.

(Step d) In this step, plating bumps and dents formed on the surface of the substrate are flattened by mechanical polishing, fine irregularities are uniformly formed, and the adhesion to the plating resist is improved. As the mechanical polishing method to be used, general buff polishing, belt polishing, brush polishing, jet scrub, and the like can be used, and these may be used in combination. Regarding the polishing roughness in each process, a particle having a grain size of # 200 to # 1500, which is suitable for the grain size or grain size of the tool to be used, is used alone or in combination. After mechanical polishing, the method of forming a plating resist can be a method of forming a plating resist of a normal wiring board, that is, a method of printing a peelable resist ink on the surface of a copper foil by a silk screen printing method. Alternatively, a method of laminating a peelable resist film on the surface of the copper foil, irradiating ultraviolet rays through a photomask so that plating can be deposited on the circuit portion, and developing and removing the circuit portion may be used. it can.

(Step e) In this step, in order to increase the adhesion between the solder resist formed in the later step j and the copper surface,
In order to form fine irregularities on the surface of the copper foil, soft etching is performed while blowing air into an acidic treatment liquid. The acidic treatment liquid may be any of an inorganic acid, an organic acid, or a mixed liquid of an organic acid and an inorganic acid, as long as it can blow copper to etch copper. Inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid and the like, and organic acids include acetic acid and the like. Among them, preferred is sulfuric acid which has no pungent odor and has relatively low corrosiveness of the apparatus. The concentration of sulfuric acid is the concentration that can etch copper,
Any concentration that does not attack the plating resist may be used. Specifically, 30 to 100 g / l is preferable. If it is less than 30 g / l, the etching power is low, and it is not possible to stably form the uneven shape. If it exceeds 100 g / l, the etching power is sufficient, but it is not appropriate because it attacks the plating resist. At this time, a copper sulfate plating solution or the like can also be used. For the supply of oxygen, pure oxygen may be supplied by bubbling, but it is preferable to supply oxygen in the air from the viewpoint of safety and economy. The supply amount of air changes depending on the size of the processing tank. In consideration of the etching rate, it is preferable that the processing is performed at an air flow rate of 0.05 to 0.5 liter / min for 1 liter of the processing liquid. At less than 0.05 liter / min, the etching power is low and the uneven shape cannot be formed stably. At more than 0.5 liter / min, the etching power is sufficient but the processing liquid is scattered greatly, which is a safety problem. Is generated.

(Step f) In the present invention, a common solder plating solution can be used in this step, for example, stannous borofluoride 130 g / l, lead borofluoride 50 g / l, borofluoric acid 125 g / l 1, 25 g / l of boric acid and an additive, and is treated at 20 to 30 ° C. at 1 to 4 A / dm ² . The thickness of the solder plating is preferably in the range of 5 to 10 μm.
If the thickness is less than 5 μm, a film having a uniform thickness cannot be obtained as a plating film, and the underlying copper may be etched when used as an etching resist. If the thickness exceeds 10 μm, a sufficient thickness for an etching resist is obtained. However, there is no merit and economical to make it thicker than that, and since the lines of electric force are concentrated at the end of the plating part, the overhanging shape that covers over the plating resist In some cases, plating may occur, and it may be difficult to remove and remove the plating resist.

(Step g) For removing the plating resist, a stripping solution for the plating resist on a normal printed wiring board, such as a 3 wt% aqueous solution of sodium hydroxide, can be used.

(Step h) Using an alkaline etchant, the copper foil other than the desired circuit is removed by etching using a solder as a resist to form a circuit pattern. As the alkaline etching solution composition, an alkaline etchant containing copper, ammonia, and chloride ions as main components as described above can be used.

(Step i) Solder plating used as an etching resist can be peeled off by using a liquid used for a solder peeling method in a normal method of manufacturing a printed wiring board, and does not damage a substrate or a copper surface. Can be used in any condition. The liquid composition includes a nitric acid / hydrogen peroxide type and an organic acid type.

(Step j) As a method of forming a solder resist in this step, a method of forming a normal solder resist for a printed wiring board can be used. That is, a method of printing the resist ink on the surface of the copper foil by a silk screen printing method, or a method of printing the resist ink on the surface of the copper foil, and forming a solder resist except a necessary circuit portion via a photomask. A method of forming a solder resist by irradiating ultraviolet rays and developing can be used.

(Step k) In the Ni / Au plating step of this step, ordinary Ni / Au plating can be applied.
Electroplating or electroless plating can be used.

[0026]

【Example】

Example 1 As shown in FIG. 1A, a glass cloth-epoxy resin-impregnated double-sided copper-clad laminate MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was used, and a normal etching method was used. An inner layer plate 1 was produced. The prepreg 2 and the copper foil 3 were overlaid on the inner layer plate, and were heated under pressure at 175 ° C. for 2.5 minutes at 2.5 MPa, and laminated and integrated as shown in FIG. 1B.
As shown in FIG. 1 (c), through holes 4 were formed in the substrate at desired positions using an NC drill machine. Using a 7 wt% aqueous alkali permanganate solution,
After roughening at a solution temperature of 70 ° C. for 5 minutes, a copper plating solution having the following composition was used as an electroless copper plating solution,
5 μm, and as shown in FIG. 1D, the inner layer circuit was electrically connected to the copper foils on both outer sides. (Plating solution composition) ・ CuSO ₄・ 5H ₂ O ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10g / l ・ EDTA ・ 4Na ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 40g / l ・ 37wt% HCHO ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 3ml / l ・ NaOH ・ ・ ・ ・ ・ ・ ・···································· In order to adjust the copper surface of the plated substrate at 70 ° C. before laminating the plating resist, mechanical polishing using a buff was performed in two stages of # 600 and # 1000. Thereafter, H-W425 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a dry film for plating resist, is laminated, and a photomask that allows light to pass therethrough is overlaid on a portion to be a circuit, and 85 mJ / cm.
² was exposed to ultraviolet light, and developed with a 1 wt% aqueous solution of sodium carbonate to form a plating resist 5 as shown in FIG. Then, into an aqueous solution of sulfuric acid 50 g / l,
The substrate was immersed for 60 minutes while bubbling air at a rate of 0.3 L / min with respect to 1 L of the treatment liquid. As shown in FIG. 1F, electrolytic solder plating 6 serving as an etching resist was applied to this substrate to a thickness of 8 μm. (Solder plating solution composition and conditions)-Stannous boron fluoride ... 130 g / l-Lead boron fluoride ... ········· 50 g / l · Borofluoric acid ······ 125 g / l Boric acid25g / lAdditives・ ・ Appropriate ・ Temperature ・ ・ ・ ・ ・ ・ ・ 20-30 ℃ ・ Current density ・ ・... 1.2 A / dm ^{2 From} this substrate, as shown in FIG. Using 40
C. for 2 minutes. Subsequently, the copper wiring portion exposed from the etching resist is removed by etching using an alkali etchant and an A process solution (trade name, manufactured by Meltex Co., Ltd.) to obtain a desired wiring circuit 7.
Was formed. Thereafter, as shown in FIG. 1 (h), electrolytic solder plating 6 as an etching resist was applied at 40 ° C. for 2 minutes using a release agent SD-666 solution (trade name, manufactured by Nippon Surface Chemical Co., Ltd.). Peeled and removed. As shown in FIG. 1 (i), PSR-4000AUS which is a liquid solder resist is
5 (manufactured by Taiyo Ink Manufacturing Co., Ltd., trade name) is printed on the entire surface by a silk screen printing method, and is formed by exposing and developing through a photomask penetrating a portion having a shape to be a solder resist. Electroless nickel plating having the following composition was performed at a liquid temperature of 90 ° C. for 12 minutes. The plating thickness was 5 μm. (Electroless nickel plating composition) Nickel sulfate 30 g / l Sodium hypophosphite ... 10g / l ・ Sodium acetate ・ ・ ・ ・ 10g / l ・ pH ・ ・ ・ ・ ・ ・············ 5 Next, electroless gold plating having the following composition was performed at a liquid temperature of 90 ° C for 7 minutes. As a result, the thickness of the plating was 0.3 μm. (Electroless gold plating solution composition)-Potassium gold cyanide-2 g / l-Ammonium chloride- ... 75g / l ・ Sodium citrate ・ ・ ・ ・ ・ ・ ・ ・ ・ 50g / l ・ Sodium hypophosphite ········· 10 g / l As described above, as shown in FIG.
A multilayer printed wiring board on which u plating 9 was formed was produced. As a result, the characteristics of the board were 2
Can withstand more than 5 minutes at 60 ° C.
T was good even after 72 hours, with no lifting of the solder resist observed.

Example 2 Surface Roughness Ra Suitable for Adhesion to Resin on External Copper Foil: 1.
A copper layer having a roughness of 0 μm and having a thickness of 5 μm as a circuit, and a carrier layer having a thickness of 70 μm having sufficient strength for handling as a metal layer as a whole;
Except that the composite metal foil from which the layer was easily peeled was used, the same procedure was performed as in Example 1.

Example 3 The outer layer copper foil has a roughness suitable for bonding to a resin, and has a 1 to 9 μm thick first copper layer to be a circuit, and a sufficient metal layer as a whole. A second copper layer having a thickness of 10 to 70 μm and a composite metal foil comprising a nickel-phosphorus alloy layer having a thickness of 0.04 to 1.5 μm provided between the two layers, Except that an ultra-thin copper foil layer was formed using the following selective etching solution, all the operations were performed in the same manner as in Example 1. Only the second copper layer was removed by etching with the following alkaline etchant. (Alkali etchant) ・ CuCl ₂・ ・ ・ ・ ・ ・ 175g / l ・ NH ₄ OH ·········· 154 g / l · NH ₄ Cl ····· 236 g / l · Liquid temperature ··· ... 50 ° C. Only the nickel-phosphorus alloy layer was removed by etching with an etching solution having the following composition. (Etching solution composition) ・ Nitric acid ・ ・ ・ ・ ・ ・ ・ 200g / l ・ Hydrogen peroxide solution (35%) ··· 10ml / l · Organic acid containing carboxyl group (DL malic acid) · · · 100g / l · Benzotriazole ·····・ ・ ・ 5g / l ・ Liquid temperature ・ ・ ・ ・ ・ ・ ・ ・ ・ 50 ℃

Example 4 A multilayer printed wiring board was manufactured in the same manner as in Example 1 except that the buffing was changed to belt sander polishing.

Example 5 A multilayer printed wiring board was manufactured in the same manner as in Example 1 except that an abrasive grain polishing step using jet scrub was added after buffing.

Comparative Example 1 A multilayer printed wiring board was manufactured in the same manner as in Example 1 except that the buffing was omitted. As a result, the adhesive strength with the solder resist was low, and the floating of the solder resist was observed after 24 hours of PCT.

Comparative Example 2 A multilayer printed wiring board was manufactured in the same manner as in Example 1 except that after buffing, the treatment with an acidic treatment solution into which air was blown was omitted.

Comparative Example 3 A multilayer printed wiring board was produced in the same manner as in Example 1 except that a jet scrub treatment was added to the solder resist pre-printing treatment.

The following test was performed on the substrate manufactured as described above. (Test)-Solder heat resistance test A float test was performed in which the substrate was floated on the solder surface heated to 260 ° C. The adhesion between the copper surface and the solder resist was evaluated. As a result, in Examples 1 to 5, the adhesion was good even after 180 seconds or more, whereas in Comparative Examples 1 and 2, 60 to 1
Blistering occurred in 20 seconds, and adhesion was low. Comparative Example 3
Was good even for 180 seconds or more, but the wiring top width was reduced, and it was not practical.

Solder Resist Adhesion The PCT was left in a constant temperature and high humidity bath at 121 ° C., 100% RH and 2 atm, and the adhesion between the solder resist and the copper surface was evaluated. As a result, in Examples 1-4, 48
h, there is no change in appearance.
h, there is no change in the appearance. In Comparative Examples 1 and 2, blistering occurs in less than 24 hours, and the appearance changes. In Comparative Example 3, there is no change in the appearance even at 48 hours or more. The mountability was low and there was no practicality.

[0036]

As described above, according to the present invention, a method for manufacturing a printed wiring board which can secure the adhesion between the solder resist and the copper surface while securing the top width and which is excellent in the mountability with the electronic component. Can be provided.

[Brief description of the drawings]

FIGS. 1A to 1J are cross-sectional views in each step for explaining an embodiment of the present invention.

[Explanation of symbols]

1. 1. inner layer plate Prepreg 3. Copper foil 4. Through hole 5. Plating resist 6. Electrolytic solder plating 7. Wiring circuit 8. Solder resist 9. Ni / Au plating

Continued on the front page (72) Inventor Kazuhisa Otsuka 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (72) Inventor ▲ Tsuru ▼ Yoshiyuki 1500 Ogawa Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. A method for manufacturing a multilayer printed wiring board, wherein the following steps are performed in this order. a. A step of laminating a prepreg on an inner layer plate on which an inner layer circuit has been formed in advance, laminating an outer layer copper foil on an outermost layer, and heating and pressing to laminate and integrate. b. A step of forming a through hole for connecting the inner layer circuit and the outer layer copper foil of the laminated and integrated substrate by a drill; c. The thermosetting resin layer on the wall surface of the formed through hole is roughened using a roughening agent, and the inner wall of the through hole and the surface of the outer layer copper foil are plated to electrically connect the inner layer circuit and the outer layer copper foil. Step of performing. d. A step of forming a plating resist by flattening the surface of the plated outer copper foil by mechanical polishing. e. A step of immersing the substrate on which the plating resist is formed while blowing air into an acidic solution. f. A process of performing solder plating on a substrate. g. Removing the plating resist from the substrate. h. A step of selectively etching away portions of the substrate that have not been solder plated with an alkaline etchant; i. Removing the solder plating from the substrate. j. A process of printing and curing a solder resist on a substrate. k. Forming Ni / Au plating on the substrate; 2. The method according to claim 1, wherein the acidic solution is a treatment solution containing sulfuric acid. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, further comprising the following steps instead of step a. a1. The outer layer copper foil has a roughness suitable for adhesion to a resin, a copper layer having a thickness of 1 to 9 μm as a circuit, and a thickness of 10 to 150 μm having sufficient strength for handling as a whole metal layer. Using a composite metal foil in which two layers can be easily peeled off, using a composite metal foil that can easily be peeled off, stacking the copper layer to be a circuit so that the roughened surface is in contact with the prepreg, and heating and pressurizing to laminate and integrate. a2. Step of peeling and removing only carrier layer 4. The method for manufacturing a multilayer printed wiring board according to claim 1, further comprising the following steps instead of the step a. a3. A first copper layer having a thickness of 1 to 9 μm which has a roughness suitable for bonding to a resin on the outer layer copper foil and a circuit having a thickness of 10 to 9 μm which has sufficient strength to be handled as a metal layer as a whole; Using a composite metal foil composed of a second copper layer having a thickness of 70 to 70 μm and a nickel-phosphorus alloy layer having a thickness of 0.04 to 1.5 μm provided between the two layers, heat-pressing and laminating and integrating Process. a4. Step of removing only second copper layer a5. Removing only the nickel-phosphorus alloy layer;