JP3792544B2 - Wiring board manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an organic material-based multilayer wiring board.
[0002]
[Prior art]
Conventionally, as an organic material-based wiring board for mounting a semiconductor element, for example, on both upper and lower surfaces of a double-sided copper-clad plate in which inner layer conductors made of copper foil are attached to upper and lower surfaces of an insulating resin plate made of glass-epoxy plate, for example. An insulating resin layer mainly composed of an epoxy resin is attached and has a plurality of through holes penetrating up and down the insulating resin plate and the insulating resin layer. A multilayer wiring board is used in which surface conductors are deposited by electroless plating and electrolytic copper plating, respectively. In this wiring board, three-dimensional high-density wiring is possible by electrically connecting an inner layer conductor and a surface layer conductor positioned above and below via a through conductor attached to the inner wall of the through hole.
[0003]
Such an organic material-based multilayer wiring board has, for example, inner layer conductors made of copper foil having a thickness of about 7 to 12 μm on both upper and lower surfaces of an insulating resin plate made of a glass-epoxy plate having a thickness of about 0.35 to 0.45 mm. An insulating resin layer having a thickness of 25 to 45 μm is deposited on both upper and lower surfaces of the double-sided copper-clad plate thus formed, and through holes having a diameter of about 200 to 500 μm are drilled from the upper surface to the lower surface by drilling. Thereafter, the surface conductor is manufactured by electroless plating and electrolytic plating on the surface of the through conductor and the insulating resin layer made of a copper plating layer having a thickness of about 15 to 50 μm on the inner wall of the through hole.
[0004]
[Problems to be solved by the invention]
By the way, in such an organic material-based multilayer wiring board, an attempt has been made to make the diameter of the through hole as small as about 75 to 130 μm in order to further increase the wiring density. In order to form such a small through hole having a diameter of about 75 to 130 μm, for example, a carbon dioxide laser drilling method is employed.
[0005]
However, when drilled with a carbon dioxide laser, a brittle carbonized layer is formed on the inner wall of the through hole, and a through conductor made of a copper plating layer is deposited on the inner wall of the through hole, and then the carbonized layer on the wall surface of the through hole is the starting point. As a result, there is a problem that peeling occurs in the through conductor, resulting in poor conduction between the through conductor and the inner layer conductor.
[0006]
The present invention has been devised in view of such conventional problems, and an object of the present invention is to provide an extremely high density in which peeling does not occur in the through conductor and the through conductor and the inner layer conductor are always well connected. It is an object of the present invention to provide a wiring board capable of wiring and a manufacturing method thereof.
[0007]
[Means for Solving the Problems]
The method for manufacturing a wiring board according to the present invention includes a step of drilling a plurality of through holes each having a carbonized layer formed on an inner wall by laser processing an insulating resin plate, and then a pretreatment plating on the carbonized layer. A step of depositing a metal layer, a step of etching and removing the pretreatment plating metal layer together with the carbonized layer, and a plating method on the inner wall of the through hole from which the pretreatment plating metal layer and the carbonized layer have been removed. And the step of depositing the through conductor.
[0008]
According to the method for manufacturing a wiring board of the present invention, after depositing a pretreatment plating metal layer on the carbonized layer of the inner wall of the through hole formed by laser processing, this is removed by etching together with the carbonized layer. Since the through conductor is deposited by plating on the inner wall of the through hole from which the pretreatment plating metal layer and the carbonized layer have been removed, the through conductor does not peel off starting from the carbonized layer.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, the manufacturing method of the wiring board of this invention is demonstrated in detail.
[0010]
FIG. 1 is a partial cross-sectional view showing an example of an embodiment of a wiring board manufactured by the manufacturing method of the present invention. In FIG. 1, 1 is an insulating resin plate, 2A and 2B are inner layer conductors, 3A and 3B are insulating resin layers, 4 is a through hole, 5 is a through conductor, and 6A and 6B are surface layer conductors. Inner layer conductors 2A and 2B and insulating resin layers 3A and 3B are attached to both upper and lower surfaces, and a plurality of through holes 4 are provided through insulating resin plate 1, inner layer conductors 2A and 2B, and insulating resin layers 3A and 3B. Furthermore, the through conductor 5 is formed on the inner wall of the through hole 4, and the surface layer conductors 6A and 6B are formed on the surfaces of the insulating resin layers 3A and 3B, whereby the wiring board of the present invention is configured. . In this embodiment, a solder resist 7 is provided in the through hole 4 and on the insulating resin layers 3A and 3B.
[0011]
The insulating resin plate 1 functions as a core member of a wiring board. For example, a glass cloth or an aramid cloth made of an organic insulating material impregnated with a resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin has a thickness of 0.35 to It is a 0.45 mm flat plate, and constitutes a so-called double-sided copper-clad plate in which inner layer conductors 2A and 2B made of copper foil having a thickness of 7 to 12 μm are deposited on both upper and lower surfaces. If the thickness of the insulating resin plate 1 is less than 0.35 mm, the insulating resin layers 3A and 3B are attached to the upper and lower surfaces thereof, or the insulating resin plate 1, the inner layer conductors 2A and 2B, and the insulating resin layers 3A and 3B are penetrated. When the plurality of through holes 4 are formed, the wiring board is warped or deformed due to the influence of heat, external force, etc., and the flatness required for the wiring board cannot be secured. On the other hand, if the thickness exceeds 0.45 mm, when the through conductor 5 is formed on the inner wall of the through hole 4 as will be described later, the plating solution is less likely to enter the through hole 4 and the through conductor 5 is formed well. It becomes difficult. Therefore, the thickness of the insulating resin plate 1 is preferably in the range of 0.35 to 0.45 mm.
[0012]
The insulating resin plate 1 is made of a glass cloth, an aramid cloth, or the like made of silica, alumina, an aramid resin or the like in an epoxy resin, bismaleimide triazine resin, polyphenylene ether resin, or the like impregnated into a glass cloth or an aramid cloth. If the fiber portion and the resin portion are contained so that the transmittance of the laser beam is substantially equal, the through-hole 4 is formed when the through-hole 4 is drilled in the insulating resin plate 1 with the laser beam as described later. It is possible to satisfactorily form the insulating resin plate 1 with a substantially uniform size. Therefore, a filler made of silica, alumina, aramid resin, or the like is added to a glass cloth, aramid cloth, or the like in an epoxy resin, bismaleimide triazine resin, or polyphenylene ether resin impregnated in the glass cloth or aramid cloth of the insulating resin plate 1. It is preferable that the fiber portion and the resin portion are contained so that the transmittance of the laser beam is substantially equal.
[0013]
The inner layer conductors 2A and 2B attached to the upper and lower surfaces of the insulating resin plate 1 are made of copper foil, and are electrically connected to the inner layer wiring conductor pattern W mainly functioning as a power supply layer and a ground layer and the inner layer wiring conductor pattern W. And an independent dummy conductor pattern D, having a thickness of 7 to 12 μm and a center line average roughness Ra of the surface of about 0.2 to 2 μm. When the thickness of the inner layer conductors 2A and 2B is less than 7 μm, sufficient electrical characteristics cannot be imparted to the inner layer wiring conductor pattern W as the power supply layer or the ground layer, and when the thickness exceeds 12 μm, As described above, when the through hole 4 penetrating the insulating resin plate 1 and the inner layer conductors 2A and 2B and the insulating resin layers 3A and 3B is drilled by laser processing, it is difficult to stably form the through hole 4. . Therefore, the thickness of the inner layer conductors 2A and 2B is preferably in the range of 7 to 12 μm.
[0014]
The inner layer conductors 2A and 2B are formed so as to have inner layer wiring conductor patterns W or dummy conductor patterns D penetrating through the through holes 4 and in contact with the later described through conductors 5 corresponding to all the through holes 4. In this case, when the through holes 4 are drilled by laser processing, the absorption and reflection of the laser beam can be made substantially the same in all the through holes 4 so that all the through holes 4 can be formed in a substantially uniform size and shape. Therefore, the inner layer conductors 2 </ b> A and 2 </ b> B are preferably formed so as to have the inner layer wiring conductor pattern W or the dummy conductor pattern D penetrating through the through holes 4 corresponding to all the through holes 4. In this case, the dummy conductor pattern D may be a substantially circular pattern whose diameter is approximately 40-100 μm larger than the diameter of the through-hole 4, and an interval with a width of approximately 30-60 μm between the inner conductor pattern W. May be provided. When the diameter of the dummy conductor pattern D is larger than the diameter of the through-hole 4 by less than 40 μm, it becomes difficult to accurately penetrate the dummy conductor pattern D when the through-hole 4 is drilled by laser processing. If it is too large, it is difficult to increase the area of the inner layer wiring conductor pattern W. In addition, when the distance between the dummy conductor pattern D and the inner layer wiring conductor pattern W is less than 30 μm, there is a tendency that electrical insulation between the dummy conductor pattern D and the inner layer wiring conductor pattern W cannot be maintained well. On the other hand, if it exceeds 60 μm, it is difficult to increase the area of the inner layer wiring conductor pattern W.
[0015]
Further, when the inner-layer conductors 2A and 2B have a center line average roughness Ra of less than 0.2 μm, the inner-layer conductors 2A and 2B do not firmly adhere to the inner-layer conductors 2A and 2B and the inner-layer conductors 2A and 2B. And the insulating resin layers 3A and 3B tend to be peeled off. On the other hand, when the thickness exceeds 2 μm, it tends to be difficult to form such a rough surface stably and efficiently. Accordingly, the center line average roughness Ra of the inner layer conductors 2A and 2B is preferably in the range of 0.2 to 2 μm.
[0016]
The insulating resin layers 3A and 3B attached to the upper and lower surfaces of the insulating resin plate 1 are made of a thermosetting resin such as epoxy resin, bismaleimide triazine resin or polyphenylene ether resin, and the degree of decomposition with respect to laser light is the insulating resin plate. The surface conductors 6A and 6B are deposited on the surface thereof. The insulating resin layers 3A and 3B are provided to provide an insulating interval for electrically insulating the inner layer conductors 2A and 2B and the surface layer conductors 6A and 6B to be insulated from each other. 25-45 μm on 2B. When the thickness of the insulating resin layers 3A and 3B is less than 25 μm on the inner layer conductors 2A and 2B, the inner layer conductors 2A and 2B and the surface layer conductors 6A and 6B to be insulated from each other can be electrically well insulated. On the other hand, if the thickness exceeds 45 μm, the through hole 4 is formed well when the through hole 4 penetrating the insulating resin plate 1 and the inner layer conductors 2A and 2B and the insulating resin layers 3A and 3B is drilled by laser processing. It becomes difficult. Therefore, the thickness of the insulating layers 3A and 3B is preferably in the range of 25 to 45 μm on the inner layer conductors 2A and 2B.
[0017]
The surface conductors 6A and 6B are made of a copper plating film having a thickness of 8 to 30 μm, and form a surface layer wiring pattern including a power supply wiring, a ground wiring, and a signal wiring. For example, an electrode of an electronic component (not shown) is connected to an exposed part of the surface layer conductor 6A on the upper surface side via solder, and an exposed part of the surface layer conductor 6B on the lower surface side is connected to another wiring board (not shown). Connected via solder.
[0018]
If the thickness of the surface conductors 6A and 6B is less than 8 μm, the electrical resistance of the surface layer wiring pattern is high. On the other hand, if the thickness exceeds 30 μm, it is difficult to form the surface layer wiring pattern at a high density. . Therefore, the thickness of the surface conductors 6A and 6B is preferably in the range of 8 to 30 μm.
[0019]
Furthermore, in the wiring board manufactured by the manufacturing method of the present invention, the through-hole 4 is formed by laser processing through the insulating resin plate 1, the inner layer conductors 2A and 2B, and the insulating resin layers 3A and 3B. A through conductor 5 is deposited on the inner wall of the through hole 4. The through hole 4 is for providing a lead-out path for leading the through conductor 5 from the upper surface of the insulating resin layer 3A to the lower surface of the insulating resin layer 3B. The through holes 4 are formed by laser processing, so that the diameter of the insulating resin plate 1 is 75 to 115 μm and the inner walls thereof are substantially vertical, and the inner walls of the insulating resin layers 3A and 3B are 10 It has a shape that is inclined at an angle of ˜30 and expands toward the outside. In this case, since the insulating resin layers 3A and 3B have a higher degree of decomposition with respect to the laser light than the insulating resin plate 1, the insulating resin layers 3A and 3B are decomposed larger than the insulating substrate 1 during laser processing, so the shape of the through hole 4 is the insulating resin. The layers 3A and 3B have a shape that expands toward the outside.
[0020]
Thus, according to the wiring board manufactured by the manufacturing method of the present invention, the through hole 4 is formed by laser processing, the diameter thereof is as small as 75 to 115 μm in the insulating resin plate 1, and the inner wall thereof is the insulating resin layer. In 3A and 3B, the through conductor 5 and the surface layer conductors 6A and 6B can be arranged at a high density because it has a shape that inclines at an angle of 10 to 30 from the vertical direction and expands toward the outside. Thus, a wiring board having extremely high density wiring can be obtained.
[0021]
The through-hole 4 has a small diameter of 75 to 115 μm in the insulating resin plate 1 but has an inner wall that is substantially vertical in the insulating resin plate 1 and 10 to 30 degrees from the vertical direction in the insulating resin layers 3A and 3B. The plating solution for forming the through conductor 5 penetrates when the through conductor 5 is deposited on the inner wall of the through hole 4 as described later. As a result, the through conductor 5 can be formed well in the through hole 4.
[0022]
When the diameter of the through hole 4 in the insulating resin plate 1 is less than 75 μm, the plating solution for forming the through conductor 5 is formed inside the through hole 4 when the through conductor 5 is deposited on the inner wall of the through hole 4. It is difficult to form the through conductor 5 on the inner wall of the through hole 4 without entering the through hole 4 on the other hand. On the other hand, if it exceeds 115 μm, it is difficult to arrange the through conductor 5 and the surface layer conductors 6A and 6B at high density. Become. Therefore, the diameter of the through hole 4 in the insulating resin plate 1 is preferably in the range of 75 to 115 μm.
[0023]
In addition, when the inner wall of the through hole 4 in the insulating resin plate 1 is not substantially vertical, bubbles are likely to be left inside the through hole 4 when the through conductor 5 is deposited on the inner wall of the through hole 4. It is difficult to form the through conductor 5 on the inner wall of the through hole 4 without the plating solution for forming well reaching the part where the bubbles are left. Therefore, it is preferable that the inner wall of the through hole 4 in the insulating resin plate 1 is substantially vertical.
[0024]
Further, when the angle at which the inner wall of the through hole 4 is inclined outward in the insulating resin layers 3A and 3B is less than 10 degrees from the vertical direction, the through conductor 5 is formed when the through conductor 5 is deposited on the inner wall of the through hole 4. The plating solution for forming the metal does not enter the inside of the through-hole 4 well, and it becomes difficult to form the through-conductor 5 on the inner wall of the through-hole 4 on the other hand. It is difficult to stably and efficiently form the through-hole 4 in which the swell spreads. Therefore, the angle at which the inner wall of the through hole 4 is inclined outward in the insulating resin layers 3A and 3B is preferably in the range of 10 to 30 degrees from the vertical direction.
[0025]
The through conductor 5 deposited on the inner wall of the through hole 4 is made of a copper plating film having a thickness of about 8 to 25 μm, and the inner layer conductor 2A is positioned above and below the insulating resin plate 1 and the insulating resin layers 3A and 3B. 2B and surface layer conductors 6A and 6B function as connecting conductors that electrically connect each other.
[0026]
When the thickness of the through conductor 5 is less than 8 μm, the electrical resistance of the through conductor 5 tends to be too high. On the other hand, when the thickness exceeds 25 μm, the through conductor 5 is disposed inside the through hole 4 to which the through conductor 5 is attached. It becomes difficult to fill the solder resist 7 to be satisfactorily. Therefore, the thickness of the through conductor 5 is preferably in the range of 8 to 25 μm.
[0027]
Further, a solder resist 7 made of a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin is deposited and filled in the surfaces of the insulating resin layers 3A and 3B and the inside of the through holes 4. The solder resist 7 functions as a protective layer for protecting the through conductor 5 and the surface layer conductors 6A and 6B and electrically insulating the surface layer wiring patterns in the surface layer conductors 6A and 6B. It is formed in a predetermined pattern that exposes a part.
[0028]
When the thickness of the solder resist 7 on the surface conductors 6A and 6B is less than 10 μm, the surface conductor 6 cannot be protected well and the surface wiring patterns in the surface conductors 6A and 6B are electrically connected to each other. On the other hand, when it exceeds 40 μm, it tends to be difficult to form the solder resist 7 in a predetermined pattern. Therefore, the thickness of the solder resist on the surface conductors 6A and 6B is preferably in the range of 10 to 40 μm.
[0029]
Next, a method for manufacturing the wiring board shown in FIG. 1 by the manufacturing method of the present invention will be described with reference to FIGS.
[0030]
First, as shown in a partial cross-sectional view in FIG. 2A, for example, a glass cloth or an aramid cloth made of an organic insulating material impregnated with an epoxy resin, a resin such as a bismaleimide triazine resin or a polyphenylene ether resin has a thickness of 0.35 to A double-sided copper-clad plate is prepared in which inner layer conductors 2A and 2B made of copper foil having a thickness of 7 to 12 μm are deposited on the upper and lower surfaces of a 0.45 mm insulating resin plate 1. The inner layer conductors 2A and 2B have their surfaces roughened so that the center line average roughness Ra of the surfaces is about 0.2 to 2 μm.
[0031]
If the thickness of the insulating resin plate 1 is less than 0.35 mm, the insulating resin layers 3A and 3B are attached to the upper and lower surfaces of the insulating resin plate 1 or penetrate the insulating resin plate 1, the inner layer conductors 2A and 2B, and the insulating resin layers 3A and 3B. When the plurality of through holes 4 are formed, the wiring board is warped or deformed due to the influence of heat or external force, and the flatness required for the wiring board cannot be secured. On the other hand, when the thickness exceeds 0.45 mm, when the through conductor 5 is formed on the inner wall of the through hole 4 as will be described later, the plating solution is less likely to enter the through hole 4, and disconnection is likely to occur in the through conductor 5. Therefore, the thickness of the insulating resin plate 1 is preferably in the range of 0.35 to 0.45 mm.
[0032]
In addition, when the thickness of the inner layer conductors 2A and 2B is less than 7 μm, the pattern of the inner layer conductors 2A and 2B cannot give sufficient electrical characteristics as a power supply layer or a ground layer, and on the other hand, when the thickness exceeds 12 μm As will be described later, when the through hole 4 penetrating the insulating resin plate 1 and the inner layer conductors 2A and 2B and the insulating resin layers 3A and 3B is drilled by laser processing, the through hole 4 having a diameter of 75 to 130 μm is stabilized. It becomes difficult to form. Therefore, the thickness of the inner layer conductors 2A and 2B is preferably in the range of 7 to 12 μm.
[0033]
Further, when the center line average roughness Ra of the inner layer conductors 2A and 2B is less than 0.2 μm, the insulating resin layers 3A and 3B are deposited on the upper and lower surfaces of the insulating resin plate 1 as described later. The inner layer conductors 2A and 2B and the insulating resin layers 3A and 3B are not firmly adhered to each other, and the inner layer conductors 2A and 2B and the insulating resin layers 3A and 3B tend to be peeled off, and the other exceeds 2 μm. And it tends to be difficult to form such a rough surface stably and efficiently. Accordingly, the center line average roughness Ra of the inner layer conductors 2A and 2B is preferably in the range of 0.2 to 2 μm.
[0034]
Further, if the inner layer conductors 2A and 2B are provided with a conductor pattern penetrating through the through holes 4 at positions where the through holes 4 are formed corresponding to all the through holes 4, the through holes 4 are formed by laser processing. At this time, the absorption and reflection of the laser light is uniform in all the through holes 4, and all the through holes 4 can be formed substantially uniformly. Therefore, the inner layer conductors 2 </ b> A and 2 </ b> B are preferably provided with conductor patterns penetrating through the through holes 4 at positions where the through holes 4 are formed corresponding to all the through holes 4.
[0035]
Such inner layer conductors 2A and 2B have a copper foil having a thickness of about 8 to 16 μm adhered to the entire upper and lower surfaces of the insulating resin plate 1, and a photosensitive dry film resist is deposited on the copper foil. Then, this photosensitive dry film resist is exposed and developed by a conventionally well-known photolithography technique to form an etching mask having the dry film resist at a pattern forming position, and then the copper foil exposed from the etching mask is used as a cupric chloride aqueous solution. Alternatively, etching is removed using an etching solution made of a ferric chloride aqueous solution, and finally the etching mask is peeled off, and then the surface is etched and roughened using a roughening solution containing formic acid in a cupric chloride aqueous solution. Formed.
[0036]
Next, as shown in a partial cross-sectional view in FIG. 2 (b), the upper and lower surfaces of the double-sided copper clad plate composed of the insulating resin plate 1 and the inner layer conductors 2A and 2B have a thickness of 25 to 45 μm on the inner layer conductors 2A and 2B. The insulating resin layers 3A and 3B are deposited. The insulating resin layers 3A and 3B are made of a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin, and the degree of decomposition with respect to a laser beam such as a carbon dioxide laser is larger than that of the insulating resin plate 1.
[0037]
When the thickness of the insulating resin layers 3A and 3B is less than 25 μm on the inner layer conductors 2A and 2B, the inner layer conductors 2A and 2B and the surface layer conductors 6A and 6B to be insulated from each other can be electrically well insulated. On the other hand, if the thickness exceeds 45 μm, the through-hole 4 having a diameter of 75 to 130 μm when the through-hole 4 penetrating the insulating resin plate 1 and the inner conductors 2A and 2B and the insulating resin layers 3A and 3B is drilled by laser processing. It becomes difficult to form the film well. Therefore, the thickness of the insulating layers 3A and 3B is preferably in the range of 25 to 45 μm on the inner layer conductors 2A and 2B.
[0038]
In order to deposit and form the insulating resin layers 3A and 3B on the upper and lower surfaces of the double-sided copper clad plate formed by coating the inner layer conductors 2A and 2B on the upper and lower surfaces of the insulating resin plate 1, the thermosetting property in a semi-cured state is used. A method is adopted in which a resin film is temporarily press-bonded on both upper and lower surfaces of a double-sided copper-clad plate with a vacuum laminator and then heat-treated to be cured.
[0039]
Next, as shown in a partial cross-sectional view in FIG. 2C, a plurality of through-holes 4 having a diameter of 75 to 130 μm that penetrate the insulating resin layers 3A and 3B, the inner conductors 2A and 2B, and the insulating resin plate 1 by laser processing. Perforate. At this time, since the degree of decomposition of the insulating resin layers 3A and 3B with respect to the laser beam is larger than that of the insulating resin plate 1, the through hole 4 has a shape that expands outward in the insulating resin layers 3A and 3B.
[0040]
As described above, since the diameter of the through hole 4 is as small as 75 to 130 μm, the through conductor 5 and the surface layer conductors 6A and 6B are made high when forming the through conductor 5 and the surface layer conductors 6A and 6B as described later. It can arrange | position with a density and, thereby, a high-density wiring board can be obtained. Further, since the hole diameter of the through hole 4 is widened outward at the portions of the insulating resin layers 3A and 3B, the through conductor 5 is formed when the through conductor 5 is deposited on the inner wall of the through hole 4 as will be described later. The plating solution for forming the metal penetrates into the through holes 4 favorably, and as a result, the through conductors 5 can be satisfactorily formed in the through holes 4.
[0041]
When the diameter of the through hole 4 is less than 75 μm, the plating solution for forming the through conductor 5 does not enter the inside of the through hole 4 when the through conductor 5 is deposited on the inner wall of the through hole 4. The through conductors 5 cannot be satisfactorily formed on the inner walls of the through holes 4, and on the other hand, when the thickness exceeds 130 μm, it is difficult to arrange the through conductors 5 and the surface layer conductors 6A and 6B at high density. Therefore, the diameter of the through hole 4 is preferably in the range of 75 to 130 μm.
[0042]
When the diameter of the opening of the through hole 4 is smaller than the diameter of the insulating resin plate 1 by less than 10 μm, the through conductor 5 is formed when the through conductor 5 is deposited on the inner wall of the through hole 4. If the plating solution does not enter the inside of the through-hole 4 and it is difficult to form the through-conductor 5 on the inner wall of the through-hole 4, it is difficult to form the through-conductor 5 on the inner wall. It becomes difficult to form the holes 4 stably. Therefore, it is preferable that the diameter of the opening of the through hole 4 is 10 to 50 μm larger than the diameter of the insulating resin plate 1.
[0043]
In order to form the through holes 4 in the insulating resin layers 3A and 3B, the inner layer conductors 2A and 2B, and the insulating resin plate 1, for example, black or black that absorbs energy of laser light satisfactorily on the insulating resin layers 3A and 3B. A laser processing sheet made of a resin having a color close to 1 is stuck, and a carbon dioxide laser beam with an output of 7 to 12 mJ is irradiated on a predetermined position with a pulse width of 50 to 500 μsec from the top of the laser processing sheet. A method of drilling the through hole 4 is employed. At this time, if the output of the carbon dioxide laser beam is less than 7 mJ, it tends to be difficult to drill the through-hole 4 to a sufficient size. On the other hand, if the output exceeds 12 mJ, the through-hole 4 of the insulating resin layers 3A and 3B The pore diameter tends to be too large. Therefore, it is preferable that the carbon dioxide laser light to be irradiated has an output of 7 to 12 mJ and a pulse width of 50 to 500 μsec. The laser processing sheet is peeled off after the through holes 4 are formed. By forming the through hole 4 by laser processing in this way, it is possible to easily form the through hole 4 having a diameter of 75 to 130 μm and a shape that expands outward in the insulating resin layers 3A and 3B. In this case, a carbonized layer 8 having a thickness of about several μm or less is formed on the inner wall of the through hole 4 due to laser processing.
[0044]
Next, as shown in a partial cross-sectional view in FIG. 2 (d), a pretreatment consisting of an electroless copper plating layer having a thickness of 1 to 3 μm on the surfaces of the carbonized layer 8 and the insulating resin layers 3A and 3B on the inner wall of the through hole 4 A plating metal layer 13A is deposited. In order to deposit the pretreatment plating metal layer 13A, a palladium catalyst is attached to the inner walls of the through holes 4 and the surfaces of the insulating resin layers 3A and 3B using, for example, a palladium active liquid containing ammonium chloride-based palladium acetate. In addition, a pretreatment plating metal layer 13A may be deposited thereon using a copper sulfate-based electroless copper plating solution. At this time, since the diameter of the through-hole 4 is increased outward in the insulating resin layers 3A and 3B, the electroless copper plating solution satisfactorily enters the through-hole 4, and as a result, the inner wall of the through-hole 4 The pretreatment plating metal layer 13A can be satisfactorily deposited on the surfaces of the carbonized layer 8 and the insulating resin layers 3A and 3B with a substantially uniform thickness. Before applying the pretreatment plating metal layer 13A, the surfaces of the insulating resin layers 3A and 3B and the inner walls of the through holes 4 are roughened by using a roughening solution made of, for example, a potassium permanganate solution or a sodium permanganate solution. If this is done, the pretreatment plating metal layer 13A can be firmly applied. Therefore, before depositing the pretreatment plating metal layer 13A, the surfaces of the insulating resin layers 3A and 3B and the inner walls of the through holes 4 are roughened using a roughening solution made of, for example, a potassium permanganate solution or a sodium permanganate solution. It is preferable to keep it.
[0045]
Next, as shown in a partial cross-sectional view in FIG. 2 (e), the pretreatment plating metal layer 13 </ b> A deposited on the carbonized layer 8 on the inner wall of the through hole 4 is removed by etching together with the carbonized layer 8. As an etchant used for this etching, an etchant composed of a mixed solution of sulfuric acid and hydrogen peroxide solution, or a cupric chloride aqueous solution or a ferric chloride aqueous solution may be used. In this case, when the pretreatment plating metal layer 13A is formed, the pretreatment plating metal layer 13A enters the microscopic irregularities of the carbonized layer 8, and the stress during the deposition of the pretreatment plating metal layer 13A is applied to the carbonization layer 8. It acts well and the carbonized layer 8 is easily peeled off. Therefore, when the pretreatment plating metal layer 13A is removed by etching, the carbonized layer 8 is well removed together with the pretreatment plating metal layer 13A.
[0046]
Next, as shown in FIG. 2 (f), the electroless metal having a thickness of 1 to 3 μm is formed on the inner wall of the through hole 4 from which the pretreatment plating metal layer 13A and the carbonized layer 8 have been removed and the surfaces of the insulating resin layers 3A and 3B. An electroless plating metal layer 13B made of copper plating is applied. In order to deposit the electroless plated metal layer 13B made of electroless copper plating, for example, a palladium active solution containing ammonium chloride-based palladium acetate is used to form the inner walls of the through holes 4 and the surfaces of the insulating resin layers 3A and 3B. A palladium catalyst may be attached to the electrode, and an electroless copper plating layer may be deposited thereon using a copper sulfate-based electroless copper plating solution. At this time, since the diameter of the through-hole 4 is increased outward in the insulating resin layers 3A and 3B, the electroless copper plating solution satisfactorily enters the through-hole 4, and as a result, the inner wall of the through-hole 4 In addition, the electroless plated metal layer 13B can be satisfactorily deposited on the surfaces of the insulating resin layers 3A and 3B with a substantially uniform thickness. The surface of the insulating resin layers 3A and 3B and the inner walls of the through holes 4 are roughened with, for example, a potassium permanganate solution or a sodium permanganate solution before the electroless plated metal layer 13B made of an electroless copper plating film is deposited. If the liquid is roughened so that the center line average roughness Ra is about 0.2 to 2 μm, the electroless plating metal film 13B can be firmly attached. Therefore, before depositing the electroless plating metal layer 13B, the surface of the insulating resin layers 3A and 3B and the inner walls of the through holes 4 are centered by using a roughening solution made of, for example, a potassium permanganate solution or a sodium permanganate solution. Roughening is preferably performed so that the average roughness Ra is about 0.2 to 2 μm. At this time, since the carbonized layer 8 is removed from the inner wall of the through hole 4, the inner wall of the through hole 4 does not peel off the electroless plating metal layer 13 </ b> B starting from the carbonized layer 8. On the other hand, the electroless plating metal layer 13B can be firmly applied.
[0047]
Next, as shown in FIG. 2G, a plating mask 14 is deposited on the electroless copper plating on the insulating layers 3A and 3B, and the thickness is formed on the electroless copper plating exposed from the plating mask 14. Electrolytic copper plating of about 10 to 35 μm is deposited, and the plating consists of electroless plating and electrolytic copper plating in which the inner wall of the through-hole 4 and the pattern formation sites on the surfaces of the insulating resin layers 3A and 3B are selectively deposited thickly A film 13C is formed.
[0048]
The plating mask 14 is formed by, for example, depositing a photosensitive dry film resist on the electroless copper plating film on the insulating resin layers 3A and 3B, and exposing and developing the dry film resist by a photolithography technique. It is formed by processing into a pattern.
[0049]
Moreover, as an electrolytic copper plating solution for depositing electrolytic copper plating, for example, an electrolytic copper plating solution made of a copper sulfate system may be used. At this time, since the diameter of the through-hole 4 is increased outward in the insulating resin layers 3A and 3B, the electrolytic copper plating solution satisfactorily penetrates into the through-hole 4, and as a result, the inner wall of the through-hole 4 and An electrolytic copper plating film is satisfactorily deposited on the surfaces of the insulating resin layers 3A and 3B with a substantially uniform thickness.
[0050]
Next, as shown in the partial cross-sectional view in FIG. 2 (h), the plating mask 14 is peeled off, and the electroless copper plating and the electrolytic copper plating are etched until the electroless copper plating under the plating mask 14 disappears. Then, the through conductor 5 is formed on the inner wall of the through hole 4 and the surface layer conductors 6A and 6B are formed on the surfaces of the insulating resin layers 3A and 3B.
[0051]
In order to etch the electroless copper plating film and the electrolytic copper plating film, an etching solution composed of a mixed solution of sulfuric acid and hydrogen peroxide solution, a cupric chloride aqueous solution or a ferric chloride aqueous solution may be used.
[0052]
At this time, since the carbonized layer 8 is removed from the inner wall of the through conductor 4, the through conductor 5 does not peel off starting from the carbonized layer 8. Therefore, according to the manufacturing method of the present invention, it is possible to obtain a highly reliable high-density wiring board in which the through conductor 5 and the inner layer conductors 2A and 2B are always well connected.
[0053]
Finally, a solder resist 7 made of a thermosetting resin such as epoxy resin, bismaleimide triazine resin, or polyphenylene ether is deposited and filled on the surfaces of the insulating resin layers 3A and 3B and the inside of the through holes 4 as shown in FIG. The wiring board of the present invention shown is completed.
[0054]
The solder resist 7 is printed and applied with a photosensitive resin paste for the solder resist 7 by using a conventionally known screen printing method so as to fill the through holes 4 from the insulating layer 3A side and the 3B side. It is formed by exposing and developing into a predetermined pattern using a well-known photolithography technique. At this time, since the diameter of the through-hole 4 is expanded outward in the insulating resin layers 3A and 3B, the resin paste for the solder resist 7 is satisfactorily infiltrated into the through-hole 4, and as a result, the through-hole 4 can be satisfactorily filled with the solder resist 7.
[0055]
【The invention's effect】
According to the method for manufacturing a wiring board of the present invention, after depositing a pretreatment plating metal layer on the carbonized layer of the inner wall of the through hole formed by laser processing, this is removed by etching together with the carbonized layer. Since the through conductor is deposited by plating on the inner wall of the through hole from which the pretreatment plating metal layer and the carbonized layer have been removed, the through conductor does not peel off starting from the carbonized layer on the inner wall of the through hole, A conduction failure does not occur between the through conductor and the inner layer conductor. Accordingly, it is possible to obtain a wiring board with high density wiring excellent in connection reliability between the through conductor and the inner layer conductor.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an example of an embodiment of a wiring board manufactured by a manufacturing method of the present invention.
FIGS. 2A to 2H are partial cross-sectional views for each process for explaining a method of manufacturing a wiring board according to the present invention. FIGS.
[Explanation of symbols]
1. Insulating resin plate
2A ・ 2B ・ ・ ・ Inner layer conductor
3A ・ 3B ・ ・ ・ Insulating resin layer
4 .... Through hole
5 .... Penetration conductor
6A ・ 6B ・ ・ ・ Surface conductor
8 .... carbonized layer
13A ・ ・ ・ ・ ・ ・ Plating metal layer for pretreatment

Claims (1)

A step of drilling a plurality of through holes each having a carbonized layer formed on the inner wall by applying laser processing to the insulating resin plate; and a step of depositing a pretreatment plating metal layer on the carbonized layer; and Removing the pretreatment plating metal layer together with the carbonized layer, and then depositing a through conductor on the inner wall of the through hole from which the pretreatment plating metal layer and the carbonized layer have been removed by plating. A method for manufacturing a wiring board, comprising:

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