JP5495002B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a printed wiring board on which IVH and filled via can be easily formed, and a method for manufacturing the same.

  Conventionally, when an interlayer conductor such as an IVH (interstitial via hole) or filled via is formed, an etching hole is provided in an upper metal wiring layer by a photo process, and then a laser beam larger than the diameter of the etching hole is irradiated. Then, only the resin layer part under the etching hole is removed to form a hole that connects the upper and lower layers, and after the desmear process that removes smear, which is an organic substance in the laser processing residual, is performed, interlayer conduction in this hole Formed a body. A filled via is an interlayer connection formed by filling a hole provided for interlayer connection with plating.

  By the way, since the inner layer copper which is the bottom of the hole for interlayer conduction has a large thermal conductivity coefficient, it cannot be smear pyrolyzed with a laser and tends to remain on the surface of the inner layer copper at the bottom of the hole for interlayer conduction. If the desmear treatment is reinforced to remove the smear in the hole, the resin on the side wall is eroded and the entrance of the hole becomes a narrow tall shape. It becomes difficult to fill with.

Therefore, in order to perform desmear treatment more completely, according to the technique disclosed in Patent Document 1, it is described that after desmear treatment, electrolytic treatment is further performed in an alkaline solution.
In order to perform the desmear process more effectively, according to the technique disclosed in Patent Document 2, the desmear process is performed by plasma cleaning.
Japanese Patent Laid-Open No. 2-241082 JP 2001-168498 A

  However, when a submerged process such as an electrolytic process in an alkaline solution is further performed after the desmear process as in the above-described prior art, another problem such as foreign matters entering the interlayer conduction hole is likely to occur. Also, the desmear process such as plasma cleaning increases the equipment cost.

  The present invention solves the above-described problem, and suppresses the generation of smears, which are organic substances of laser processing residues in the hole for interlayer conduction, thereby facilitating the formation of IVH and filled vias, and its An object is to provide a manufacturing method.

The present invention relates to the following.
(1) Inner layer copper, an insulating layer provided on the inner layer copper, an interlayer connection hole formed by laser irradiation penetrating the insulating layer and reaching the inner layer copper surface, and formed in the interlayer connection hole A printed wiring board having a conductor, wherein the surface roughness of the inner layer copper surface subjected to the laser irradiation and desmear treatment is 3 μm to 20 μm, and the surface area is equal to or greater than the area of the recesses of the unevenness . A printed wiring board in which copper grains are concentrated near the top of the convex portion rather than the concave portion.
(2) A printed wiring board in which a thin film of copper plating is formed so as to fill the copper grains provided on the convex portion in (1) above.
(3) In the above (1) or (2), the area of the projection of surface roughness provided on the inner layer copper surface has a flat tip of 20μm of irregularities from 3μm is the area of the recess equal to or higher than the print Wiring board.
(4) Inner layer copper, an insulating layer provided on the inner layer copper, an interlayer connection hole formed by laser irradiation and desmearing that penetrates the insulating layer and reaches the inner layer copper surface, and in the interlayer connection hole A printed wiring board having a formed conductor, a step of providing irregularities having a surface roughness of 3 μm to 20 μm on the surface of the inner layer copper, and an area equal to or greater than the area of the concave portions of the irregularities ; A method of manufacturing a printed wiring board, comprising: a step of providing copper grains concentrated near the top of the convex portion than a concave portion; and a step of forming a thin film of copper plating so as to fill the copper grains provided on the convex portion .

  According to the present invention, it is possible to provide a printed wiring board that facilitates the formation of IVH and filled vias, and a method for manufacturing the same, by suppressing the generation of smears, which are organic substances of laser processing residues in interlayer connection holes. Become.

  The printed wiring board which is the subject of the present invention is a printed wiring board having IVH and filled vias as interlayer connection holes.

  The inner layer copper in this invention means the copper conductor provided in the inner layer of the printed wiring board. As a method for forming the inner layer copper, for example, a copper foil is laminated and integrated on the upper surface and / or the lower surface of a required number of resin-impregnated base materials in which a reinforcing base material is impregnated with a resin composition, and this copper foil is etched. Can be used to form a circuit. The material of the copper foil is not particularly limited as long as it is used as the inner layer copper of the printed wiring board.

  The insulating layer in the present invention refers to an electrical insulation between the inner layer copper and another inner layer copper, or between the inner layer copper and the surface copper conductor. The material for the insulating layer is not particularly limited as long as it is used as an insulating layer for a printed wiring board. As a method for forming the insulating layer, for example, the copper foil is laminated and integrated on the upper surface and / or the lower surface of the required number of the resin-impregnated base materials in which the resin composition is impregnated into the reinforcing base material. Formed between.

Examples of the laser used in the present invention include gas lasers such as CO ₂ , CO, and excimer, and solid lasers such as YAG. Since the CO ₂ laser can easily obtain a large output, it is suitable for processing IVH of φ50 μm or more. When processing a fine IVH of φ50 μm or less, a YAG laser with a shorter wavelength and good condensing property is suitable.

Laser irradiation in the present invention is means for forming a hole for interlayer connection (interlayer connection hole). For example, when interlayer connection such as IVH or filled via is performed by plating, a necessary interlayer connection hole is formed. It is a means for forming. The laser to be used is not particularly limited as long as it is a general one used for printed wiring boards such as a CO ₂ laser drilling machine. Irradiation conditions are set in consideration of the material, thickness, etc. of what constitutes the printed wiring board. If the laser irradiation energy is increased or the pulse width is increased, the inner layer copper will generate a large amount of heat and smear will be easily removed. However, excessive heat will cause holes in the inner layer copper and the IVH shape will be barrel-shaped. Therefore, it is desirable to suppress at least the pulse width to 20 to 30 μsec or less.

  The interlayer connection hole in the present invention refers to a hole that obtains electrical continuity between the inner layer copper and another inner layer copper, or between the inner layer copper and the surface copper conductor. This interlayer connection hole is formed by irradiating a laser so as to penetrate the insulating layer and reach the inner layer copper surface. As an example, in the case of a printed wiring board having an inner layer copper and a surface layer copper conductor with an insulating layer in between, the surface layer copper conductor is partially removed by a photo process or the like to provide an opening in the copper conductor. Aim at the opening and irradiate with laser light. Since the insulating layer is exposed in the opening, a laser is directly applied to the insulating layer, and a hole is easily formed. When this hole reaches the inner layer copper surface, an interlayer connection hole that penetrates the insulating layer and reaches the inner layer copper is formed. At this time, the laser is irradiated so as to reach the inner layer copper surface. That is, an interlayer connection hole from the surface layer to the inner layer copper is formed by irradiating the laser so as to reach the inner layer copper surface. At the same time, smear, which is an organic substance of laser processing residual, is generated on the inner layer copper surface, but as described later, the inner surface of the inner layer copper to be irradiated with laser is provided with irregularities having a surface roughness of 3 μm to 20 μm. Thus, the smear is thermally decomposed. Depending on the type of laser used and the laser irradiation conditions, it is not necessary to provide an opening in the surface copper conductor so that it can reach the inner copper surface from above the surface copper conductor through the insulating layer below it. In addition, it is possible to form an interlayer connection hole by irradiating a laser.

  The conductive body in the present invention is an electrical connection between the upper and lower layers using interlayer connection holes for connecting the upper and lower layers of the printed wiring board, and is generally called a printed wiring board called IVH or filled via. The conductor formed in the interlayer connection hole used in the above. As a method of forming a conductor in the interlayer connection hole, electroless plating, electroplating, or the like generally used for printed wiring boards can be used.

  The unevenness provided on the surface of the inner layer copper used in the present invention has a surface roughness of 3 μm to 20 μm. This surface roughness refers to the surface roughness indicated by the ten-point average height Rz. Thus, by providing unevenness with a surface roughness of 3 μm to 20 μm on the inner copper surface to be irradiated with laser, the lateral heat conduction of copper having a large heat conductivity is divided, and the heat of laser irradiation is reduced. A heat storage effect can be realized. This facilitates thermal decomposition of the smear with a laser. When the surface roughness is 3 μm or less on the inner layer copper surface, the heat storage effect of laser irradiation heat is weak, and when the surface roughness is 20 μm or more on the inner layer copper surface, it is easy to break if the convex shape is thin, The pitch between the protrusions tends to be wide, and is not suitable for a hole connecting the layers of the high-density printed wiring board.

  There are no particular restrictions on the method for forming the irregularities, such as chemical treatment such as chemical etching, electrochemical treatment such as electrolytic etching, physical treatment such as shot blasting, etc., but since it becomes an inner layer conductor, adhesion to various laminated materials is required. For this reason, it is not desirable that the oxide film after the treatment remains, or an organic residue such as an organic residue that remains on the surface has poor adhesion to the laminated material.

As the chemical etching, an inorganic acid such as hydrochloric acid or sulfuric acid, an organic acid or the like can be used alone or mixed, or hydrogen peroxide, triazole, halide, glue or the like added to the inorganic acid can be used.
As the electrolytic etching, an acidic bath such as sulfuric acid, hydrochloric acid or sulfamic acid, or an alkaline bath such as sodium hydroxide, potassium hydroxide, pyrophosphoric acid or cyanogen bath can be used.
Moreover, an additive is added to these acid or alkaline solutions as necessary. As the additive, those similar to those used for chemical etching, commercially available additives usually used for bright plating solutions, and the like can be used.
As the shot blasting, a general one in which metal or ceramic fine particles and compressed air are mixed and sprayed can be used.
A copper clad laminate using a double-sided roughened foil may be used for the inner layer substrate, and the roughened surface shape of the copper foil may be used as the unevenness of the inner layer copper surface as it is.

  It is desirable to provide copper grains on the convex and concave portions having a surface roughness of 3 μm to 20 μm provided on the surface of the inner layer copper used in the present invention. The copper grain in this invention refers to the copper fine particle which produces the roughened surface formed by copper plating. Thus, in addition to the unevenness of the surface roughness of 3 μm to 20 μm on the inner layer copper surface, by providing copper grains on the unevenness of the unevenness, the tips of the thin protrusions are thickened and divided, and the copper foil surface Therefore, the heat storage effect of the laser irradiation heat can be realized. When laser light irradiation is started, the copper foil surface with a predetermined roughness starts to melt by heat, and when the copper component on the initial irradiation surface melts and evaporates, a smooth mirror-surface copper surface is formed below it. The Rukoto. The reflectivity of the mirror-finished copper foil surface is a surface having a high reflectivity. As a result, under the general laser power and processing conditions used in laser drilling for forming conformal vias, it is difficult to laser-process a copper foil layer with a certain depth or more. Absent.

  For example, the following method can be used as a method of providing copper grains on the uneven protrusions having a surface roughness of 3 μm to 20 μm provided on the inner layer copper surface. That is, an inner layer copper having irregularities with a surface roughness of 3 μm to 20 μm is prepared, and the first copper plating is performed on the inner layer copper surface. In the case of the surface having such irregularities, copper is concentrated in the vicinity of the top of the convex portion and does not deposit so much in the valley portion. For this reason, a copper grain is formed in the uneven part provided in the inner layer copper surface.

  In the first plating for precipitating the copper particles, for example, the condition of burnt plating can be adopted. The burn plating conditions are not particularly limited, and are determined in consideration of the characteristics of the production line. For example, if a copper sulfate-based solution is used, the concentration is 5 to 30 g / l copper, 10 to 200 g / l sulfuric acid, and other additives as necessary (α-naphthoquinoline, dextrin, glue, thiourea, molybdenum, iron , Nickel, selenium, tellurium, etc.), the liquid temperature is 10 to 40 ° C., and the current density is a condition near the limit current density of the electrolytic solution. The apparent film thickness is about 0.2 to 10 μm.

  As described above, when copper particles are provided on the inner layer copper surface, in the case of an uneven surface, electrodeposition is concentrated near the top of the protrusion. For this reason, in order to prevent the copper grains from desorbing from the inner layer copper surface, a thin film of copper plating is formed so as to bury the copper grains provided in the convex portions on the inner layer copper surface having the copper grains. desirable. By doing so, the tip of the convex portion becomes too hot due to the laser irradiation and does not easily evaporate and scatter, and only smear can be selected and evaporated and scattered.

  As a method of forming a thin film of copper plating so as to fill the copper layer provided on the convex portion on the inner layer copper surface having copper particles, the second copper plating is performed on the inner layer copper surface having copper particles. . In the second copper plating, a thin film of copper plating is provided so as to fill the copper grains provided on the convex portions by filling the gap between the copper grains between the inner layer copper surface and the grains.

  The second plating for forming a copper plating thin film is a step for uniformly depositing copper so as to fill fine copper grains under smooth plating conditions. The smooth plating conditions are not particularly limited and are determined in consideration of the characteristics of the production line. For example, if a copper sulfate-based solution is used, the conditions are copper 50 to 80 g / l, sulfuric acid 50 to 150 g / l, liquid temperature 40 to 50 ° C., and current density 10 to 50 A / dm 2. The apparent film thickness is about 0.1 to 3 μm. Preferably, it is about 1 to 3 μm.

  In the unevenness provided on the inner layer copper surface of the present invention, the area of the convex part is preferably equal to or greater than the concave part. Thus, if the surface of the inner layer copper has irregularities with a surface roughness of 3 μm to 20 μm and the area of the convex part is equal to or greater than the concave part, the tip of the convex part of the inner layer copper becomes high temperature by laser irradiation. It is too easy to evaporate and scatter, and only smear can be selectively evaporated and scatter. The area of the convex portion in the present invention refers to the area occupied by the convex portion when the concave and convex portion is viewed in cross section. That is, in the sectional view of the concavo-convex portion, it means the area of the convex portion above the straight line connecting the bottoms of the adjacent concave portions. Moreover, the area of the recessed part in this invention means the area which a recessed part occupies when an uneven | corrugated | grooved part is seen in a cross section. That is, in the cross-sectional view of the concavo-convex portion, it means the area of the blank portion below the straight line connecting the tops of the adjacent convex portions.

  The method of forming the unevenness provided on the inner layer copper surface so that the area of the convex part is equal to or more than the concave part is etched with the roughening liquid, depending on the type when using the roughening liquid. Thereafter, a method of expanding the top of the convex portion by slightly crushing the sharp convex portion on the surface with a rolling roll or the like is preferable because it is simple. If the inner copper surface is not plated with copper, use a copper-clad laminate with a double-sided roughened foil for the inner substrate, crush the sharp convex part of the surface with a rolling roll, etc., and widen the top of the convex part. Also good.

  Hereinafter, the printed wiring board of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic view of a printed wiring board of the present invention. In order to obtain the configuration of FIG. 1, first, an inner layer base material 1 with a copper foil is prepared, and a copper foil that becomes the inner layer copper 4 is processed into a circuit shape. Next, unevenness 10 having a surface roughness of 3 μm to 20 μm is provided on the surface of the inner layer copper 4. The copper foil that forms the inner layer copper 4 may be processed into a circuit shape after providing the surface roughness of the inner layer copper 4 with the irregularities 10 having a surface roughness of 3 μm to 20 μm.

  FIG. 2 is a schematic cross-sectional view of the unevenness 10 provided on the surface of the inner layer copper of the present invention. Fig.2 (a) has shown the state of the unevenness | corrugation 10 before a process. The unevenness 10 is formed by roughening by etching in the same manner as so-called copper foil mat surface treatment, and then plating the surface to 0.5 μm to 1.0 μm or 3.0 μm or less to make the surface uniform. Is suitable. FIG. 2B shows a state in which fine copper particles (copper grains 6) are provided on the surface of the concavo-convex 10. FIG. 2C shows a state in which the thin film 7 is formed by uniformly depositing copper so as to fill the fine copper particles (copper grains 6).

  FIG. 3 shows a schematic sectional view of another example of the unevenness 10 provided on the surface of the inner layer copper of the present invention. Fig.3 (a) has shown the state of the unevenness | corrugation 10 before a process. FIG. 3B shows a state after the surface of the convex portion 11 having a sharp angle is crushed with a rolling roll or the like.

  In order to obtain the configuration of FIG. 1, next, the insulating layer 2 and a copper foil that becomes the upper surface copper 3 are laminated and integrated on the surface of the inner layer copper 4 formed with a circuit. As a method of laminating and integrating, a method of laminating and pressing the prepreg that becomes the inner layer base material 1 and the insulating layer 2 and the copper foil that becomes the surface layer copper 3, and the insulating layer 2 and the surface layer copper 3 on the inner layer base material 1. A method of laminating an integrated resin with a single-sided copper foil can be used. The thickness of the insulating layer 2 is about 10 to 100 μm, preferably 20 to 60 μm, and the thickness of the copper foil to be the surface copper 3 is about 1 to 18 μm.

  The resin with a single-sided copper foil is formed by applying a resin varnish to the copper foil using a kiss coater, a roll coater, a comma coater or the like, or laminating a film-like resin on the copper foil. When the resin varnish is applied to the copper foil, it is then heated and dried, but the conditions are 30 to 180 minutes at a temperature of 100 to 200 ° C., and the amount of residual solvent in the resin composition after this heating and drying is About 0.2 to 10% is appropriate. When laminating a film-like resin on a copper foil, a vacuum or atmospheric pressure condition is suitable under the conditions of 50 to 150 ° C. and 0.1 to 5 MPa.

  Next, after patterning the opening of the shape of the interlayer connection hole 5 on the copper foil to be the upper surface copper layer 3, the interlayer connection hole 5 is formed by a laser at the position where the opening is provided.

Example 1
A copper clad laminate (MCL-E-679FG, manufactured by Hitachi Chemical Co., Ltd.) obtained by bonding a glass epoxy material with a copper foil having a thickness of 18 μm was patterned by etching to form an inner layer copper.
Next, as a method for forming irregularities on the inner layer copper surface, irregularities having a surface roughness of 3 to 5 μm were provided by CZ treatment (MEC etch bond CZ-8100, MEC etch bond is a registered trademark of MEC Co., Ltd.). .
A prepreg (GEA-679FG manufactured by Hitachi Chemical Co., Ltd.) is laminated on the inner layer material, and a copper foil for outer layer wiring (MT18S5DH manufactured by Mitsui Mining & Mining Co., Ltd.) is laminated and integrated on the upper layer, and the copper foil for outer layer wiring is etched. By removing the copper foil, a conformal mask for laser drilling was formed.
Next, to the conformal mask portion from which the copper foil is removed and the resin is exposed, a carbon dioxide gas laser (Hitachi Via Mechanics Co., Ltd. laser processing conditions: frequency 1000 Hz, pulse width 10 to 30 μsec, cycle number 5 to 10) And a plurality of non-through holes were formed by removing the resin by combustion decomposition.
In the desmear treatment, swolling dip securigant P (manufactured by Atotech Japan Co., Ltd., securigant is a registered trademark of Atotech Co., Germany) of about 500 ml / l and caustic soda (manufactured by Shin-Etsu Chemical Co., Ltd.) pH 9. 5 to 11.8 is used, NaMnO4 about 60 g / l is used in the etching part, and reduction securigant P (manufactured by Atotech Japan Co., Ltd. is a registered trademark of Atotech Co., Germany) is used in the reduction part. l and 98% H2SO4 (Furukawa Machine Metal Co., Ltd.) using a Desmear horizontal line made by Atotech in Germany using a line speed of 1.0 m / min. Thus, in general, the process of 2 pass processing (twice processing) was performed only for 1 pass (processing once).
Next, after applying catalyst core using HS201B (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a palladium colloid catalyst, on the metal foil and inside the via hole, CUST2000 (trade name, manufactured by Hitachi Chemical Co., Ltd.) is used. An underlayer electroless plating layer having a thickness of 0.5 to 1.0 μm was formed in the hole and on the surface copper body layer.
Next, plating with a thickness of about 20 μm was performed in the holes and on the surface copper body layer by electrolytic field plating (Meltex Co., Ltd.).
Thereafter, using a dry film H-9040 (Hitachi Chemical Co., Ltd., trade name), lamination is performed on the entire surface of the substrate on which plating has been completed to form a resist having a thickness of 40 μm. Circuits were printed on the resist by a direct drawing machine, and outer layer circuits were formed by a photo method in which development, etching with iron chloride, and stripping of the resist with an alkaline stripping solution were performed.
Table 1 shows the connection failure rate of the conductive body vias manufactured by this method (hot oil test 260 ° C., 5 seconds of flowing water 5 seconds, 30 cycles after passing resistance change rate ± 10% or less).

(Example 2)
The unevenness of the inner layer copper foil is formed in the same manner as in Example 1 except that a double-sided roughened foil is used for the conductive laminate of the inner layer substrate, and the unevenness with a surface roughness of 5 to 7 μm is provided. Table 1 shows the connection failure rate of the substrate.

(Example 3)
After forming the unevenness of the inner layer copper foil, it was manufactured in the same manner as in Example 1 except that the sharp convex portion of the surface was crushed by 0.7 to 1.2 μm with a rolling roll to widen the top of the convex portion, and the substrate was poorly connected The rates are shown in Table 1.

(Example 4)
After forming the irregularities of the inner layer copper foil, copper grains are provided on the irregularities of the irregularities, and the others are manufactured in the same manner as in Example 1, and the connection failure rate of the substrate is shown in Table 1.
The copper grains were added at a concentration of 10 g / l copper, 100 g / l sulfuric acid, dextrin and glue, a liquid temperature of 25 ° C., and a current density near the limit current density of the electrolyte. The apparent film thickness was about 0.5 to 2 μm.

(Example 5)
After the unevenness of the inner layer copper foil was formed, a copper grain was provided on the convex part of the unevenness, and a copper-plated thin film was formed so as to fill the copper grain. Other than that, it manufactured similarly to Example 1, and shows the connection failure rate of the board | substrate in Table 1.
The copper grains were added at a concentration of 10 g / l copper, 100 g / l sulfuric acid, dextrin and glue, a liquid temperature of 25 ° C., and a current density near the limit current density of the electrolyte. The apparent film thickness was about 0.5 to 2 μm.
Next, smooth plating conditions for filling the concave and convex portions between the copper grains without any gap and forming a thin film of copper plating are as follows: concentration is 70 g / l copper, sulfuric acid 100 g / l, liquid temperature 40 ° C., and the condition of a current density of 30A / dm ^2. The apparent film thickness was 0.5 to 1.0 μm.

(Comparative Example 1)
The surface of the inner layer copper foil was not particularly roughened, and was manufactured in the same manner as in Example 1, and the connection failure rate of the substrate is shown in Table 1.

(Comparative Example 2)
The surface roughness of the unevenness provided on the inner layer copper foil was set to 1 to 2 μm, and the other parts were manufactured in the same manner as in Example 1, and the connection failure rate of the substrate is shown in Table 1.

  As shown in Table 1, it can be seen that the smear removability is reliably improved by providing the inner layer copper foil with irregularities having a surface roughness of 3 μm or more.

1 shows a schematic cross-sectional view of the present invention. The schematic sectional drawing of the unevenness | corrugation provided in the surface of the inner layer copper foil of this invention is shown. The schematic sectional drawing of another unevenness | corrugation provided in the surface of the inner layer copper foil of this invention is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inner layer base material, 2 ... Insulating layer, 3 ... Surface copper conductor (surface layer copper), 4 ... Inner layer copper, 5 ... Interlayer connection hole, 6 ... Copper grain, 7 ... Thin film, 8 ... Conductor, 9 ... Print Wiring board, 10 ... unevenness (inner layer copper surface), 11 ... convex portion, 12 ... concave portion

Claims (4)

Inner layer copper, an insulating layer provided on the inner layer copper, an interlayer connection hole formed by laser irradiation that penetrates the insulating layer and reaches the surface of the inner layer copper, and a conductor formed in the interlayer connection hole The top surface of the convex portion having a surface roughness of 3 μm to 20 μm and an area equal to or greater than the concave area of the concave and convex portions on the inner layer copper surface subjected to the laser irradiation and desmear treatment A printed wiring board with copper grains concentrated near the recesses.   2. The printed wiring board according to claim 1, wherein a copper-plated thin film is formed so as to fill the copper grains provided on the convex portion. According to claim 1 or 2, the area of the projection of surface roughness provided on the inner layer copper surface has a flat tip of 20μm of irregularities from 3μm is, the printed wiring board is the area of the recess equal to or greater than. Inner layer copper, an insulating layer provided on the inner layer copper, an interlayer connection hole formed by laser irradiation and desmear processing that penetrates the insulating layer and reaches the surface of the inner layer copper, and is formed in the interlayer connection hole And a conductor having a surface roughness of 3 μm to 20 μm on the surface of the inner layer copper , and a protrusion having an area equal to or greater than the area of the recess of the unevenness. A method of manufacturing a printed wiring board, comprising: a step of providing copper grains concentrated near the top than the concave portion; and a step of forming a copper plating thin film so as to fill the copper grains provided on the convex portion.

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