JP2006287251A - Wiring board and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board which enables very high density wiring in which the disconnection of a through conductor is not caused even if the diameter of a through hole is as small as 75 to 130 μm, and to provide a method for manufacturing the wiring board. <P>SOLUTION: The upper and lower surfaces of an insulating resin board 1 consist of a copper foil. Internal layer conductors 2A and 2B, which has an internal layer wiring conductor pattern W and a dummy conductor pattern D which is electrically independent from the internal layer wiring conductor pattern W, are deposited in the upper and lower surfaces of a double-sided copper clad board, and insulating resin layers 3A and 3B, in which decomposition degree by laser beam irradiation is higher than that of the insulating resin board 1, are deposited in the upper and lower surfaces of the double-sided copper clad board. A plurality of through holes 4, which penetrate vertically through the insulating resin board 1, the internal layer conductors 2A and 2B, and the insulating resin layers 3A and 3B, and expand outward in the insulating resin layers 3A and 3B, are formed by laser processing. A through conductor 5, which is connected to the internal layer conductors 2A and 2B, is deposited and formed in the inner wall of the through hole 4, and surface layer conductors 6A and 6B, which are connected to the surfaces of the insulating resin layers 3A and 3B are deposited and formed in the surfaces of the resin layers 3A and 3B by plating, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic material-based multilayer wiring board and a method for manufacturing the same.

  Conventionally, as an organic material-based wiring board for mounting a semiconductor element, for example, a plurality of insulating layers made of glass-epoxy plates having wiring conductors made of copper foil on both sides or one side are also adhesive layers made of glass-epoxy plates. A multilayer wiring board is used which is laminated through the two.

  In this organic material-based multilayer wiring board, a plurality of through holes are provided from the upper surface to the lower surface, and the wiring conductors positioned above and below are electrically connected to the inner wall of the through hole with each insulating layer interposed therebetween. For this reason, a through conductor made of a copper plating film is deposited to enable three-dimensional high-density wiring.

  In addition, such an organic material-based multilayer wiring board is formed from a glass-epoxy plate having a thickness of about 0.1 to 0.5 mm in which wiring conductors made of copper foil having a thickness of about 15 to 50 μm are deposited on both sides or one side. After laminating a plurality of insulating plates through an adhesive layer made of a glass-epoxy plate having a thickness of about 0.1 to 0.2 mm, a through hole having a diameter of about 200 to 500 μm is drilled from the upper surface to the lower surface by drilling, Thereafter, a through conductor made of a copper plating film having a thickness of about 15 to 50 μm is deposited on the inner wall of the through hole by an electroless plating method and an electrolytic plating method.

  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 laser drilling method is employed.

  However, in the conventional organic material-based multilayer wiring board, since the thickness of each insulating plate and the adhesive layer is as thick as about 0.1 to 0.5 mm, the diameter of the through-hole penetrating each insulating plate and the adhesive layer is, for example, 75 to If it is as small as about 130 μm, when depositing a through conductor made of a copper plating film on the inner wall of this through hole, the plating solution for depositing the through conductor is less likely to penetrate into the through hole. There has been a problem that the conductor is not satisfactorily deposited and breakage of the through conductor is likely to occur.

  The present invention has been devised in view of such conventional problems, and an object of the present invention is extremely high in that no breakage occurs in the through conductor even when the diameter of the through hole is small, for example, about 75 to 130 μm. It is an object of the present invention to provide a wiring board capable of high-density wiring and a manufacturing method thereof.

  The wiring board of the present invention comprises a double-sided copper-clad wire comprising copper foil on both upper and lower surfaces of an insulating resin plate, and an inner-layer wiring conductor pattern and an inner-layer conductor having a dummy conductor pattern electrically independent from the inner-layer wiring conductor pattern. The upper and lower surfaces of the plate are covered with an insulating resin layer having a higher degree of decomposition by laser light irradiation than the insulating resin plate, and penetrates the insulating resin plate, the inner layer conductor and the insulating resin layer vertically. And a plurality of through-holes that expand toward the outside in the insulating resin layer are formed by laser processing, a through-conductor connected to the inner-layer conductor on the inner wall of the through-hole, and the through-conductor on the surface of the insulating resin layer The surface layer conductors connected to each are formed by being deposited by plating.

  Also, the method for manufacturing a wiring board according to the present invention is such that an inner layer conductor having an inner layer wiring conductor pattern and a dummy conductor pattern electrically independent from the inner layer wiring conductor pattern is deposited on both upper and lower surfaces of the insulating resin plate. An insulating resin layer having a higher degree of decomposition due to laser light irradiation than the insulating resin plate is attached to the upper and lower surfaces of the double-sided copper-clad plate, and the insulating resin plate, the inner layer conductor, and the insulating resin layer are A plurality of through holes that extend through the insulating resin layer and expand toward the outside in the insulating resin layer by laser processing, and then the through conductor connected to the inner layer conductor on the inner wall of the through hole and the insulating resin layer A surface layer conductor connected to the through conductor is deposited on the surface by plating.

  According to the wiring board of the present invention, since the above-described configuration is employed, when the through conductor is deposited on the inner wall of the through hole, the plating solution for depositing the through conductor enters the through hole satisfactorily. The through conductor is formed well on the inner wall of the through hole.

  Further, according to the method for manufacturing a wiring board of the present invention, since the above-described configuration is adopted, when the through conductor is deposited on the inner wall of the through hole, the plating solution for depositing the through conductor is good in the through hole. As a result, it is possible to obtain a wiring board in which through conductors are well formed on the inner walls of the through holes.

  Next, the wiring board of the present invention will be described in detail. FIG. 1 is a partial cross-sectional view showing an example of an embodiment of a wiring board according to 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.

  The insulating resin plate 1 functions as a core member of the wiring board of the present invention. For example, a thickness made of an organic insulating material in which a glass cloth or an aramid cloth is impregnated with a resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin. Is a flat plate having a thickness of 0.35 to 0.45 mm, 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.

  The insulating resin plate 1 is made of an epoxy resin, bismaleimide triazine resin, polyphenylene ether resin or the like impregnated into glass cloth or aramid cloth. If the fiber portion and the resin portion are contained so that the laser beam transmittance 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.

  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.

  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.

  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.

  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. 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.

  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.

  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.

  Further, in the wiring board 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. The through conductor 5 is formed to be deposited.

  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 are decomposed more than the insulating resin plate 1 by the laser light irradiation, the insulating resin layers 3A and 3B are decomposed larger than the insulating substrate 1 during laser processing, so that the shape of the through hole 4 is reduced. The insulating resin layers 3A and 3B have a shape that increases in diameter toward the outside.

  Thus, according to the wiring board 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 perpendicular to the insulating resin layers 3A and 3B. The through conductor 5 and the surface layer conductors 6A and 6B can be arranged at a high density because the shape is inclined at an angle of 10 to 30 and expanded toward the outside. Can be obtained.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  Thus, according to the wiring board of the present invention, the through conductor 5 can be satisfactorily formed in the through hole 4, and thereby a wiring board having an extremely high density wiring that does not cause the breakage of the through conductor 5 can be obtained. Can be provided.

  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.

  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 a resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin has a thickness of 0.35. 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 an insulating resin plate 1 having a thickness of 0.45 mm.

  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.

  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.

  Further, when the thickness of the inner layer conductors 2A and 2B is less than 7 μm, the conductor pattern of the inner layer conductors 2A and 2B cannot give sufficient electric characteristics as a power supply layer or a ground layer, and on the other hand, the thickness exceeds 12 μm. In this case, 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 can be stably formed. It becomes difficult. Therefore, the thickness of the inner layer conductors 2A and 2B is preferably in the range of 7 to 12 μm.

  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.

  Furthermore, the inner layer conductors 2A and 2B are penetrated by the through holes 4 at positions where the through holes 4 are formed, and a conductor pattern in contact with the through conductors 5 to be described later is provided corresponding to all the through holes 4, so that the laser When the through holes 4 are formed by processing, 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 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.

  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 well-known photolithography technique to form an etching mask having the dry film resist at the conductive pattern forming position, and then the copper foil exposed from the etching mask is cupric chloride. Etching is removed using an etching solution composed of an aqueous solution or ferric chloride aqueous solution, and finally the etching mask is peeled off, and then the surface is etched using a roughening solution containing formic acid in a cupric chloride aqueous solution. Formed by roughening.

  Next, as shown in a partial cross-sectional view in FIG. 2B, the insulating resin layers 3A and 3B having a thickness of 25 to 45 μm are formed on the upper and lower surfaces of the double-sided copper-clad plate 11 on the inner conductors 2A and 2B. To do. 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.

  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. 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.

  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.

  Next, as shown in a partial cross-sectional view in FIG. 2C, a plurality of through holes 4 penetrating the insulating resin layers 3A and 3B, the inner layer conductors 2A and 2B, and the insulating resin plate 1 are drilled by laser processing.

The through-hole 4 has a diameter of 75 to 115 μm in the insulating resin plate 1 and an inner wall that is substantially vertical. In the insulating resin layers 3A and 3B, the inner wall is inclined outward at an angle of 10 to 30 degrees from the vertical direction. The shape is increased in diameter.

  In this case, since the degree of decomposition of the insulating resin layers 3A and 3B due to the laser light irradiation is greater than that of the insulating resin plate 1, the insulating resin layers 3A and 3B are decomposed to a greater extent than the insulating resin plate 1 by laser processing. The inner wall of the hole 4 can be formed into a shape that is substantially vertical in the insulating resin plate 1 and is inclined toward the outside by inclining at an angle of 10 to 30 degrees from the vertical direction in the insulating resin layers 3A and 3B.

  As described above, the diameter of the through hole 4 is made as small as 75 to 115 μm in the insulating resin plate 1 and the inner wall of the through hole 4 is inclined outward at an angle of 10 to 30 degrees from the vertical direction in the insulating resin layers 3A and 3B. Since the shape increases toward the surface, the through conductor 5 and the surface layer conductors 6A and 6B can be arranged at a high density when forming the through conductor 5 and the surface layer conductors 6A and 6B as described later. Thus, a high-density wiring board can be obtained.

  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.

  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. However, if the thickness exceeds 115 μm, it is difficult to dispose the through conductor 5 and the surface layer conductors 6A and 6B at a 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.

  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.

  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.

  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 resin having a color close to that of a laser beam is pasted, and a carbon dioxide laser with an output of 7 to 12 mJ is irradiated from above the laser processing sheet to a predetermined position with a pulse width of 50 to 500 μsec. A method of drilling the holes 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, the insulating resin plate 1 has a diameter of 75 to 115 μm and its inner wall is substantially vertical, and the inner walls of the insulating resin layers 3A and 3B are 10 It is possible to easily form the through-hole 4 having a shape that is inclined at an angle of ˜30 degrees and expands toward the outside.

  Next, as shown in a partial sectional view in FIG. 2D, a plating film 13A made of an electroless copper plating film having a thickness of 1 to 3 μm is deposited on the inner wall of the through hole 4 and the surfaces of the insulating resin layers 3A and 3B. Let In order to deposit the plating film 13A made of an electroless plating film, for example, a palladium catalyst is used on the inner walls of the through holes 4 and the surfaces of the insulating resin layers 3A and 3B by using a palladium active solution containing ammonium chloride-based palladium acetate. And an electroless copper plating film may be deposited thereon using a copper sulfate-based electroless copper plating solution.

  Although the diameter of the through hole 4 is as small as 75 to 115 μm in the insulating resin plate 1, the inner wall thereof is substantially vertical in the insulating resin plate 1 and outside at an angle of 10 to 30 from the vertical direction in the insulating resin layers 3A and 3B. Therefore, the electroless copper plating solution penetrates well into the through-hole 4, and as a result, the electroless copper is formed on the inner wall of the through-hole 4 and the surfaces of the insulating resin layers 3A and 3B. The plating film can be satisfactorily deposited to a substantially uniform thickness.

  Before the plating film 13A made of an electroless copper plating film is applied, the surface of the insulating resin layers 3A and 3B and the inner wall of the through hole 4 are made of a roughening solution made of, for example, a potassium permanganate solution or a sodium permanganate solution. If the surface roughness is made rough so that the center line average roughness Ra is about 0.2 to 2 μm, the plating film 13A made of an electroless copper plating film can be firmly applied.

  Therefore, before depositing the plating film 13A made of an electroless copper plating film, the surface of the insulating resin layers 3A and 3B and the inner wall of the through hole 4 are made of a roughening solution made of, for example, a potassium permanganate solution or a sodium permanganate solution. The center line average roughness Ra is preferably roughened to about 0.2 to 2 μm.

  Next, as shown in a partial cross-sectional view in FIG. 2E, a plating mask 14 is deposited on the electroless copper plating film on the insulating layers 3A and 3B, and the electroless exposed from the plating mask 14 is applied. Electroless copper plating film having a thickness of about 10 to 35 μm is deposited on the copper plating film, and the inner wall of the through hole 4 and the conductive pattern formation sites on the surfaces of the insulating resin layers 3A and 3B are selectively deposited thickly. A plating film 13B composed of a plating film and an electrolytic copper plating film is formed.

  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.

  Moreover, as an electrolytic copper plating solution for depositing an electrolytic copper plating film, for example, an electrolytic copper plating solution made of a copper sulfate system may be used. At this time, although the diameter of the through hole 4 is as small as 75 to 115 μm in the insulating resin plate 1, its inner wall is substantially vertical in the insulating resin plate 1 and 10 to 30 from the vertical direction in the insulating resin layers 3A and 3B. Since it has a shape that expands toward the outside at an angle, the electrolytic copper plating solution penetrates well into the through hole 4, and as a result, the inner wall of the through hole 4 and the surfaces of the insulating resin layers 3 </ b> A and 3 </ b> B are electrolyzed. The copper plating film is satisfactorily deposited to a substantially uniform thickness.

  Next, as shown in a partial cross-sectional view in FIG. 2 (f), the electroless copper plating film and the electrolytic copper plating are removed until the plating mask 14 is peeled off and the electroless copper plating film under the plating mask 14 disappears. The film is etched to form the through conductor 5 on the inner wall of the through hole 4 and the surface conductors 6A and 6B on the surfaces of the insulating resin layers 3A and 3B.

  In order to etch the electroless copper plating film and the electrolytic copper plating film, an etching solution made of a cupric chloride aqueous solution or a ferric chloride aqueous solution may be used.

  Finally, 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 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 in FIG.

  Note that the solder resist 7 is printed and applied with a photosensitive resin paste for the solder resist 7 by using a well-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, the through-hole 4 has a shape in which the inner wall of the insulating resin layers 3A and 3B is inclined at an angle of 10 to 30 degrees from the vertical direction and expands toward the outside. As a result, the through-hole 4 can be satisfactorily filled with the solder resist 7.

  Thus, according to the method for manufacturing a wiring board of the present invention, it is possible to obtain a wiring board capable of extremely high-density wiring without causing disconnection in the through conductor 5.

It is a fragmentary sectional view showing an example of an embodiment of a wiring board of the present invention. (A)-(f) is a fragmentary sectional view for every process for demonstrating the manufacturing method of the wiring board of this invention.

Explanation of symbols

1. Insulating resin plates 2A, 2B ... Inner layer conductors 3A, 3B ... Insulating resin layer 4 ... Through holes 5 ... Through conductors 6A 6B ... Surface conductor

Claims (2)

On both upper and lower surfaces of a double-sided copper-clad plate comprising copper foil on both upper and lower surfaces of an insulating resin plate, and an inner-layer wiring conductor pattern and an inner-layer conductor having a dummy conductor pattern electrically independent from the inner-layer wiring conductor pattern, An insulating resin layer having a higher degree of decomposition due to laser light irradiation than that of the insulating resin plate is applied, and penetrates the insulating resin plate, the inner layer conductor and the insulating resin layer vertically, and in the insulating resin layer A plurality of through-holes whose diameter increases toward the outside are formed by laser processing, a through-conductor connected to the inner-layer conductor on the inner wall of the through-hole, and a surface layer conductor connected to the through-conductor on the surface of the insulating resin layer A wiring board characterized by being formed by being deposited by plating. On both upper and lower surfaces of a double-sided copper-clad plate comprising copper foil on both upper and lower surfaces of an insulating resin plate, and an inner-layer wiring conductor pattern and an inner-layer conductor having a dummy conductor pattern electrically independent from the inner-layer wiring conductor pattern, An insulating resin layer having a higher degree of decomposition due to laser light irradiation than that of the insulating resin plate is applied, penetrates the insulating resin plate, the inner layer conductor, and the insulating resin layer vertically and outwards in the insulating resin layer. A plurality of through-holes that expand toward the surface are formed by laser processing, and then a through-conductor connected to the inner layer conductor on the inner wall of the through-hole and a surface layer conductor connected to the through-conductor on the surface of the insulating resin layer A method of manufacturing a wiring board, characterized in that each is deposited by plating.

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