JP2003218490A - Printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board in which a plating agent for forming a conductive body in an internal wall of an end surface through hole can enter sufficiently into the end surface through hole. <P>SOLUTION: In a printed wiring board, an end surface through hole is formed on an end surface of a substrate forming a circuit pattern so as to perforate the end surface and one surface, respectively, and have a bottom to form a non-penetrating state in a thickness direction of the substrate. The closed-end hole is formed with a conductor electrically connected to the circuit pattern, and the closed-end hole is formed by either a sandblast processing or a photo-via method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board electrically connected to another printed wiring board and a method for manufacturing the printed wiring board.

[0002]

2. Description of the Related Art In order to electrically connect a printed wiring board to another printed wiring board such as a parent board, there is known a technique of forming an end surface through hole on an end surface of a printed circuit board constituting the printed wiring board. . The end surface through hole is also referred to as a half through hole.

FIG. 33 is a perspective view of a conventional printed wiring board 9 having an end face through hole formed on the end face. The printed wiring board 9 has a substrate 91, and a circuit pattern 92 is formed on the surface of the substrate 91. The end surface 93 of the substrate 91 is provided with a plurality of semi-cylindrical end surface through holes 94 at regular intervals. Each end surface through hole 94 is formed so as to penetrate the substrate 91 along the thickness direction of the substrate 91. A conductor 96 is formed on the inner surface of each end surface through hole 94 so as to be electrically connected to the circuit pattern 92 provided on the surface of the substrate 91.

FIG. 34 is a sectional view for explaining an example of mounting the conventional printed wiring board 9. The printed wiring board 9 in which the end surface through holes 94 are formed is mounted on, for example, the parent board 81. Lands 82 are provided on the parent board 81 at positions corresponding to the respective end surface through holes 94 formed on the printed wiring board 9. The printed wiring board 9 is arranged such that each end surface through hole 94 is located on the corresponding land 82, and solder for electrically connecting the conductor 96 formed on the inner surface of each end surface through hole 94 to the land 82. It is fixed on the parent board 81 by 83.

35 to 39 are explanatory views of a method of manufacturing the printed wiring board 9 in which the end face through holes 94 are formed. In this example, a simple double-sided substrate will be described as an example, but the procedure is the same for a multilayer substrate. Referring to FIG. 35, first, a copper-clad laminate 90 is prepared. Then, as shown in FIG. 36, through-holes 99 are formed in the copper-clad laminate 90 by drilling or laser processing. Further, through holes 94 are formed as end surface through holes 94 at positions corresponding to the respective lands 82 formed on the parent board 81.
Form A.

Next, as shown in FIG. 37, a conductor layer 96A is formed by plating so as to cover the entire copper-clad laminate 90 in which the through-holes 99 and the through-holes 94A to be the end surface through-holes are formed. This plating is usually performed in the order of electroless copper plating and electrolytic copper plating after appropriate pretreatment. After that, an etching resist is formed to form a circuit pattern 92, and a solder resist process and a silk printing process are performed to obtain the state shown in FIG. Then, as shown in FIG. 39, the copper-clad laminate 90 is cut along the end face 97 so as to divide each through hole 94A into halves to form the printed wiring board 9. The printed wiring board 9 has a through hole 94A on the end surface of the substrate 91.
Is divided into halves to form end face through holes 94.

Japanese Unexamined Patent Publication (Kokai) No. 10-242610 discloses another printed wiring board having an end face through hole formed on its end face. In the printed wiring board disclosed in the above publication, a bottomed hole having a hole depth of about half or less of the thickness of the substrate is formed as the end face through hole by a laser processing method.

[0008]

However, as shown in FIG.
The printed wiring board 9 described above with reference to FIG. 39 has the following problems.

First, in order to cope with the recent high-density and high-definition wiring pattern, when the hole diameter of the end face through hole 94 is made small and the hole pitch is made narrow, it is very close and small in the processing step. A through hole 94A having a hole diameter must be formed in the substrate. If it is attempted to open a through hole 94A having a small hole diameter that is extremely close to the substrate, the strength of the substrate decreases during the processing,
There is a problem that the substrate is not easy to handle.

Next, if the board is made multi-layered to cope with a wiring pattern having a high density and a high definition, the board becomes thicker, and the ratio of the depth of the through hole 94A to the hole diameter becomes larger. . Therefore, the plating liquid for forming the conductor on the inner wall of the through hole 94A is
There is a problem that defective plating occurs as a result of not being sufficiently filled in A, the inner wall not being completely covered with the plated metal, or the thickness of the metal plating formed on the inner wall being insufficient.

If the diameter of the through hole 94A is reduced, the area of the inner wall of the through hole 94A becomes smaller. Therefore, the end surface through hole 94 formed on the printed wiring board 9 is electrically connected to the land 82 formed on the parent board 81. The area where the solder 83, which is mechanically and mechanically connected, contacts the inner wall of the end face through hole 94 is reduced. Therefore, there is a problem that the physical connection strength between the printed wiring board 9 and the parent board 81 is reduced. Further, the printed wiring board 9 and the parent board 8
The physical connection strength with 1 is the strength of the solder 83 itself formed at the corner formed by the inner wall of the end surface through hole 94 formed on the printed wiring board 9 and the land 82 provided on the parent board 81. Depends on. Internal stress is most likely to remain in the corner portion when the solder 83 is cooled and solidified, and the stress is likely to be concentrated when a mechanical load acts on the printed wiring board 9 or the parent board 81.
As the amount of solder 83 decreases, the printed wiring board 9 and the parent board 8
There is a problem in that it is difficult to maintain the physical connection strength with No. 1.

Further, if the hole pitch of the end surface through-holes 94 is narrowed, there is a problem that solder bridges connecting the solders 94 supplied to the end surface through-holes 94 are likely to occur between the adjacent end surface through-holes 94.

Further, no component can be mounted in the area on the parent board 81 on which the printed wiring board 9 is mounted, and furthermore, the end face through hole 9 formed in the printed wiring board 9 is formed.
Since the land 82 provided on the parent board 81 corresponding to No. 4 occupies a large area, there is a problem that the density of the wiring pattern on the parent board 81 is significantly reduced.

The printed wiring board disclosed in Japanese Unexamined Patent Publication No. 10-242610 has the following problems.

First, since the end face through hole formed by the laser processing method has a small hole diameter and the formed end face through hole has a bottom, it is difficult for the plating solution to enter, and the inside of the end face through hole is uniformly plated. Difficult to do.

Further, since the end face through hole is formed by heating with a laser, the hole wall of the formed end face through hole is carbonized, and the strength of the hole wall is weak. Since the formed end face through hole has a small hole diameter and has a bottom, the strength is weakened by carbonization by the laser processing method so that the adhesion strength of the plated metal to the hole wall can be sufficiently secured. It is difficult to remove the carbonized layer on the hole wall. As described above, the strength of the hole wall of the end face through hole formed by the laser processing method is weak, so when the substrate is cut by a mold or the like so as to divide the end face through hole into halves, the hole wall of the end face through hole is plated. There is a problem that a large shearing force acts on the plated metal, and the plated plated metal cannot withstand this shearing force and may be peeled off.

Further, when the end face through hole is formed by the laser processing method, the hole diameter of the end face through hole is 0.05 mm to 0.2 due to restrictions such as time and time required for laser processing.
The hole diameter is as small as mm. If the hole diameter of the end face through hole is small in this way, the amount of solder that connects the printed wiring board to the parent board will be extremely small, and the contact area between the end face through hole and solder will also be small, resulting in poor solder wettability. However, there is a problem that the connection stability and the connection strength are deteriorated.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a printed wiring board and a method for manufacturing the same, which can increase the connection strength with a parent board.

Another object of the present invention is to provide a printed wiring board and a method for manufacturing the same, in which a plating solution for forming a conductor on the inner wall of the end face through hole can sufficiently enter into the end face through hole. is there.

Still another object of the present invention is to provide a printed wiring board and a method for manufacturing the same, which can increase the adhesion strength of the plated metal to the inner wall of the end face through hole.

Still another object of the present invention is to provide a printed wiring board and a method of manufacturing the printed wiring board capable of processing end face through holes while maintaining the strength of the substrate.

[0022]

In a printed wiring board according to the present invention, an end face of a substrate on which a circuit pattern is formed is opened in the end face and one surface of the end face and is not penetrated in the thickness direction of the substrate. An end face through hole having a bottom is formed so as to be in a state, and the end face through hole,
A conductor electrically connected to the circuit pattern is formed, and the end face through hole has a planar shape of any one of a semicircular shape, a semi-elliptical shape, a semi-elliptical shape, a rectangular shape, and a triangular shape. The above-mentioned object is achieved thereby.

The end face through holes may be formed by either sandblasting or photo via method.

A circuit pattern connected to the end face through hole may be formed on the surface of the substrate.

The substrate has a laminated structure of at least three layers, a circuit pattern connected to the end face through hole is formed in a layer provided inside the laminated structure, and the conductor is , And may be connected to a circuit pattern formed on a layer provided inside.

The circuit pattern is formed so as to be exposed at the bottom of the end face through hole, and may be connected to the conductor formed in the end face through hole.

The method of manufacturing a printed wiring board according to the present invention comprises a preparatory step of preparing a copper-clad laminate or a multilayer wiring board on which an outer layer pattern is not formed, and a through hole having a bottom along the thickness direction of the board. Forming a through hole; forming a conductor layer so as to cover the side wall and bottom surface of the through hole; and forming a conductor layer so as to cover the surface of the substrate; and etching the conductor layer formed on the surface of the substrate. Characterized by including an etching step of forming a circuit pattern, and after the etching step, a cutting step of forming an end face through hole by cutting the substrate along an end face intersecting the through hole, Thereby, the above object is achieved.

In the through hole forming step, the through hole may be formed by sandblasting.

Prior to the through hole forming step, the method further includes the step of forming a conductor pattern for controlling the working depth of the sandblasting at a predetermined depth position along the thickness direction of the substrate. In the through hole forming step, the end surface through hole may be formed at the predetermined depth so that the conductor pattern is exposed.

In the step of forming the conductor layer, electroless plating is performed on the entire surface of the substrate and the inner wall of the through hole, and then electroplating is performed to form a conductor layer. A plating voltage may be applied to the conductor pattern exposed at the bottom of the end face through hole.

In the through hole forming step, the through hole may be formed by a photo via method.

In the conductor layer forming step, the conductor layer may be formed by electroless plating.

In the conductor layer forming step, the conductor layer may be formed by either sputtering or vapor deposition.

Prior to the through hole forming step, the method further includes a step of forming an inner layer circuit pattern at a predetermined depth position along the thickness direction of the substrate, wherein the through hole forming step comprises the inner layer circuit. The through hole may be formed so that the pattern is exposed, and in the conductor forming step, the conductor may be formed so as to be connected to the inner layer circuit pattern exposed in the through hole.

The through-hole formed in the through-hole forming step has an elliptical planar shape,
The end surface through hole after the substrate is cut by the cutting step may have a semicircular planar shape.

The through hole formed in the through hole forming step has an elliptical shape, an elliptical shape,
It may have either a rectangular shape or a triangular shape.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION A printed wiring board according to an embodiment of the present invention will be described below. The printed wiring board according to the present embodiment can be stably connected to the parent board due to the high connection strength.

(First Embodiment) FIG. 1 is a perspective view of a printed wiring board 1 according to the first embodiment. The printed wiring board 1 has a substrate 11, and a circuit pattern 12 is formed on the front and back surfaces of the substrate 11. Board 11
On the end face 13, a plurality of bottomed holes 14 are formed as end face through holes so as to open to the end face 13 and one surface of the substrate 11, respectively. Each bottomed hole 14 is formed along the thickness direction of the substrate 11. Each bottomed hole 1
Reference numeral 4 has a bottom 15 and side walls, and is formed so as not to penetrate the substrate 11. The bottom 15 of each bottomed hole 14 has a semi-circular shape, and each bottomed hole 14 has a semi-cylindrical shape and opens toward the outside. Bottom 15 of each bottomed hole 14
A conductor 16 is formed on the side wall and electrically connected to the circuit pattern 12.

FIG. 2 is a sectional view for explaining an example of mounting the printed wiring board 1. The printed wiring board 1 in which the bottomed holes 14 are formed is mounted on, for example, the parent board 51. In this case, the printed wiring board 1 is arranged so that the opening side of each bottomed hole 14 faces the parent board 51. A land 52 is provided on the parent board 51 at a position corresponding to each bottomed hole 14 formed in the printed wiring board 1. Printed wiring board 1
Are arranged such that each bottomed hole 14 faces the corresponding land 52, and the solder 53 electrically connects the conductors 16 formed on the bottom 15 and the side walls of each bottomed hole 14 to the land 52. It is fixed to the parent board 51.

Since the solder 53 is in contact with both the bottom and the side wall of the conductor 16 formed in each bottomed hole 14, FIG.
The soldering area is remarkably larger than the structure in which the solder 83 is in contact only with the side wall of the conductor 96 formed in each end surface through hole 94 described above with reference to FIG. Therefore, the connection strength between the bottomed hole 14 as an end surface through hole formed in the printed wiring board 1 and the land 52 provided in the parent board 51 is dramatically improved.

Further, the conductor 1 formed in the bottomed hole 14
The amount of solder 53 required to connect 6 to the land 52 provided on the parent board 51 is substantially equal to the volume of the bottomed hole 14, and the board in the conventional technique described above with reference to FIG. The amount of solder required is smaller than that of the structure of the end surface through hole 94 penetrating through. Further, since the required amount of solder 53 is substantially equal to the volume of the bottomed hole 14, the required amount of solder 53 can be grasped more accurately than the configuration of the end face through hole 94 penetrating the substrate shown in FIG. can do.
Further, the bottomed hole 14 is opened only in the direction orthogonal to the adjacent end surface through hole, and even if the amount of solder is too large, it does not protrude in the adjacent end surface through hole direction.
The risk of a solder bridge occurring between the adjacent end surface through holes is significantly reduced as compared with the structure of the end surface through holes 94 penetrating the substrate shown in FIG.

3 to 7 are sectional views for explaining the method for manufacturing the printed wiring board 1. First, as shown in FIG.
A double-sided copper-clad laminate is prepared in which copper foils 18 are formed on both sides of a substrate 10 that is the printed wiring board 1. After that, FIG.
As shown in FIG. 5, a through hole 19 is formed along the thickness direction of the substrate 10 by penetrating the substrate 10 and the copper foil 18, and a bottomed hole 14 having a bottom is formed by a drill. The bottomed hole 14 is formed by controlling the feed amount of the drill and stopping the drill at an appropriate depth inside the substrate 10.

Then, as shown in FIG.
9 and the double-sided copper-clad laminate having the bottomed holes 14 washed with water and subjected to plating pretreatment, and then the bottomed holes 14, through holes 19 and double-sided copper-clad laminate formed in the double-sided copper-clad laminate A wet electroless copper plating as a conductor layer 16A so as to cover both surfaces of
Further, electrolytic copper plating is formed to a thickness of 25 μm.

Next, as shown in FIG. 6, the conductor layer 16A is etched to form the circuit pattern 12 on the front surface side and the back surface side of the substrate 10. The circuit pattern 12 has a bottomed hole 1
4 is formed so as to be electrically connected to the conductor layer 16A formed on the inner surface. Then, in the step of processing the outer shape of the printed wiring board 1, the end surface 17 intersecting the bottomed hole 14 is formed.
The printed circuit board 1 is obtained by cutting the substrate 10 along the line. As shown in FIG. 7, each printed wiring board 1 is a substrate 1
The bottomed hole 14 obtained by dividing the bottomed hole 14 in half is formed in the end face 13 of No. 1.

As described above, according to the first embodiment, the bottomed hole 14 is formed along the thickness direction of the substrate 11,
Since both the bottom and side wall of the conductor 16 formed in each bottomed hole 14 are in contact with the solder 53, the conductor 9 formed in each end surface through hole 94 described above with reference to FIG. 34.
The soldering area is remarkably larger than that of the prior art configuration in which the solder 83 is in contact with only the side wall of 6. Therefore, the connection strength between the bottomed hole 14 formed in the printed wiring board 1 and the land 52 provided in the parent board 51 can be dramatically increased.

An example in which the present invention is applied to a double-sided board in which the circuit pattern 12 is formed on both sides of the board 11 has been shown.
The present invention is not limited to this. The circuit pattern 12 may be formed on one surface of the substrate 11. Moreover, the present invention can be applied to a multilayer substrate. Furthermore, although an example in which copper is used as the plating metal has been shown, other metals may be used.

Further, although an example of using wet electroless copper plating has been shown, a method of performing metallization treatment in a vapor phase such as sputtering, vacuum deposition, or CVD may be used. This makes it possible to prevent bubbles and the like from remaining in the through hole because the through hole to be processed has a small diameter. Further, since the aspect ratio, which represents the ratio of the depth of the through hole to the diameter of the through hole, becomes large, it is possible to prevent the adhesion state of the plating from being deteriorated.

Further, although the example of forming the metal plating twice, such as forming the electroless copper plating after forming the electroless copper plating, the thin metal plating may be formed once. Alternatively, the metal plating may be formed to a sufficient thickness at once in one go.

FIG. 8 is a sectional view showing another printed wiring board 1A according to the first embodiment and its mounting example. Figure 2
The same components as those in the mounting example of the printed wiring board 1 described above with reference to FIG. Detailed description of these components will be omitted.

On the end surface of the printed wiring board 1A, a bottomed hole 14 having an opening on its front surface and a bottomed hole 14 having an opening on its back surface are formed. The printed wiring board 1A is
The printed wiring board 1 is mounted on the parent board 51, and the printed wiring board 1 is mounted on the printed wiring board 1A. In the printed wiring board 1A, each bottomed hole 14 having an opening on the surface of the main board 51 side is formed at a position corresponding to a land (not shown) provided on the main board 51. In the printed wiring board 1A, each bottomed hole 14 having an opening on the surface on the printed wiring board 1 side is formed at a position corresponding to each bottomed hole 14 formed in the printed wiring board 1. Each bottomed hole 14 formed on the surface of the parent board 51, a land (not shown) provided on the parent board 51, each bottomed hole 14 formed on the surface of the printed wiring board 1 side, and the printed wiring board 1 The bottomed holes 14 formed in the above are respectively connected by solder 53. An electronic component 21 is mounted on the printed wiring board 1.

In such a configuration, the circuit pattern connected to the conductor provided in the bottomed hole 14 formed in the surface of the printed wiring board 1A on the side of the printed wiring board 1 constitutes the printed wiring board 1A. A bottomed hole 14 formed on the surface of the parent substrate 51 side that is routed in the inner layer of the substrate
Connected to a conductor provided on the. Printed wiring board 1A
Bottomed hole 1 formed in the surface of the printed wiring board 1 side in
4 are arranged so as to correspond to the arrangement of the terminals on the printed wiring board 1, and the bottomed holes 14 formed on the surface of the mother board 51 side are arranged at positions corresponding to the arrangement of the terminals on the mother board 51. There is. Therefore, the printed wiring board 1A is
It functions to convert the arrangement of terminals on the printed wiring board 1 into the arrangement of terminals on the parent board 51. The printed wiring board that functions to convert the arrangement of terminals in this way is called a "getting board", a "converting board", or the like, and is a circuit board or integrated circuit that has a pin arrangement different from that of the parent board. Used when mounting on a board.

(Embodiment 2) FIGS. 9 to 12 are sectional views for explaining a method of manufacturing a printed wiring board according to Embodiment 2. The same components as those of the printed wiring board 1 according to the first embodiment are designated by the same reference numerals. Detailed description of these components will be omitted. The difference from the printed wiring board according to Embodiment 1 is that the bottomed holes are formed by sandblasting.

Referring to FIG. 9, as in the first embodiment, copper foil 18 is formed on both sides of substrate 10 which is a printed wiring board.
To form a double-sided copper-clad laminate. Referring to FIG. 10, by drilling along the thickness direction of the substrate 10,
Through holes 19 are formed so as to penetrate the substrate 10 and the copper foil 18.

Referring to FIG. 11, a resist 22 is applied on the copper foil 18 formed on one surface of the double-sided copper-clad laminate. For the resist 22, it is preferable to use a photo-curing resin that has flexibility and elasticity after photo-curing and is hard to be polished by sandblasting. In the second embodiment, a commercially available positive resist is used as the resist for sandblasting. A photomask is arranged in a region where a bottomed hole is to be formed, and light is irradiated to a region other than a region where a bottomed hole is to be formed to cure the resist 22. After that, development,
After the after-cure process, as shown in FIG. 11, the resist 22 formed in the region where the bottomed hole is to be formed is removed to form a resist opening 23.

Referring to FIG. 12, the copper foil 18 and the substrate 10 under the resist opening 23 are removed by sandblasting to form a bottomed hole 14D. Bottomed hole 14
The depth of D is controlled by the grinding speed and the processing time which are determined by the blast material, the blast pressure and the like. Then, the resist 22 is peeled off. After this, the first embodiment
5 to 7, the conductor layer 16A is formed so as to cover the entire double-sided copper-clad laminate, and the conductor layer 16A is etched to form the circuit pattern 12 on the substrate 10. Then, when the substrate 10 is cut along the end face intersecting the bottomed hole 14, the printed wiring board in which the bottomed hole 14D is formed in the substrate 11 is completed.

When the bottomed hole is formed by using sandblasting, unlike the case where the drill or laser processing is used as in the first embodiment, the plane of the bottomed hole is increased without increasing man-hours and costs. The shape can be any shape other than circular. The reason is that the photomask shape that determines the planar shape of the bottomed hole when using sandblasting is created in a normal photographic process,
This is because an arbitrary shape can be obtained without increasing man-hours and costs.

FIG. 13 is a schematic plan view for explaining another method for manufacturing a printed wiring board. FIG. 13 shows an example in which a bottomed hole 14A having an oval cross section is formed. As shown in FIG. 13, when the substrate 10 is cut along the end surface 17A orthogonal to the longitudinal direction of the ellipse which is the planar shape of the bottomed hole 14A, a bottomed hole having a semi-elliptic cylinder shape is formed. When the planar shape of the bottomed hole 14A is an ellipse, the opening area of the bottomed hole 14A becomes larger than the opening area of the bottomed hole having a circular cross-sectional shape, and the opening area with respect to the depth of the bottomed hole 14A. Since the aspect ratio, which represents the ratio of
Since the plating liquid for forming the conductor layer can sufficiently enter the bottomed hole, it is possible to reduce defective plating. Further, when the opening area of the bottomed hole is increased, the connection area of the solder is increased, so that the connection strength between the printed wiring board and the parent board can be further increased. Bottomed hole 14
The planar shape of A may be an ellipse.

FIG. 14 is a schematic plan view for explaining still another method for manufacturing a printed wiring board, and FIG. 15 is a schematic perspective view thereof. FIG. 14 shows that the substrate 10 having the bottomed hole 14A in the shape of an oval has an end surface 17 shown in FIG.
It shows an example of cutting by the end surface 17B located on the left side of A. The opening area of the bottomed hole after cutting shown in FIG. 14 is larger than the opening area of the bottomed hole after cutting shown in FIG. For this reason, the plating solution can more sufficiently enter the bottomed hole, so that defective plating can be further reduced. Further, since the opening area of the bottomed hole is increased, the connection area of the solder is increased, so that the connection strength between the printed wiring board and the parent board can be further increased. When it is attempted to obtain a connection area equivalent to the connection area of the solder by the bottomed hole shown in FIG. 14 by drilling,
Since the hole diameter becomes large, the pitch of the bottomed holes is significantly increased.

FIG. 16 is a schematic plan view for explaining another method for manufacturing a printed wiring board. FIG. 16 shows an example in which the longitudinal direction of an ellipse showing the cross-sectional shape of the bottomed hole 14A is along the end surface 17C. According to this configuration, FIG.
Also, the connection area of the solder can be increased similarly to the bottomed hole having the elliptical cross-sectional shape shown in FIG. The bottomed hole 14A whose longitudinal direction of this ellipse is along the end face 17C is
Since the pitch is wide, it is possible to obtain a bottomed hole that can obtain a solder connection area that is equal to or larger than the same even by drilling, but the bottomed hole formed by drilling has a large area occupied on the substrate. To become
This will reduce the wiring density and the degree of freedom of wiring of the printed wiring board. The present embodiment in which the bottomed hole is formed by sandblasting is excellent in that it does not occur.

FIG. 17 is a schematic plan view for explaining still another method for manufacturing a printed wiring board, and FIG. 18 is a perspective view thereof. 17 and 18 show an example in which a bottomed hole 14B having a triangular cross section is formed. The substrate 10 is cut along the end surface 17D parallel to the base of the triangle. The bottomed hole 14B has a triangular prism shape in which the side surface including the bottom of the triangle, which is the cross-sectional shape, and the end surface 17D of the substrate 11 coincide with each other, and the width increases from the end surface 17D of the substrate 11 toward the inside of the substrate 11. It has a narrow shape. According to this configuration, since the solder easily enters the bottomed hole 14B due to the capillary phenomenon, the size of the bottomed hole is so small that the solder is less likely to adhere to the conductor formed in the bottomed hole. Can be solved.

FIG. 19 is a schematic plan view illustrating a method for manufacturing a printed wiring board according to a comparative example, and FIG. 20 is a perspective view thereof. 19 and 20 show a bottomed hole 14C having a circular cross section formed by drilling. The mother substrate 10 is cut along the end surface 17E intersecting the bottomed hole 14C having a circular cross-sectional shape, and the end surface 17
The part on the left side of E is cut off. When a hole is formed by drilling, laser processing, or the like in this manner, the cross section of the formed hole becomes a circle with a small diameter, and the completed printed wiring board has a semicircular cross section. If the hole diameter becomes smaller, as described above, the plating solution for forming the conductor layer is less likely to enter the hole, and bubbles remain inside the hole, which may cause defective plating. Further, when the hole diameter is small, the area of the solder that connects the printed wiring board and the parent board is small, so that the connection strength cannot be secured. On the other hand, in the present embodiment, in order to form the bottomed hole by sandblasting, the cross-sectional shape of the bottomed hole may be a semi-oval larger than a semi-circle, a semi-ellipse, a rectangle, a triangle, or the like. Therefore, the plating solution can easily enter the bottomed hole, and the area of the solder connecting the printed wiring board and the parent board can be increased.

(Third Embodiment) FIGS. 21 and 22 show
FIG. 11 is a cross-sectional view illustrating the method for manufacturing the printed wiring board according to the third embodiment. The same components as those of the printed wiring board according to the second embodiment are designated by the same reference numerals. Detailed description of these components will be omitted. The printed wiring board according to the second embodiment is different from the printed wiring board in that a multilayer board is provided, an inner layer circuit pattern and a conductor pattern are formed on the multilayer board, and the conductor pattern is used to control the depth of a bottomed hole. That is the point.

Referring to FIG. 21, it has four layers,
A multilayer substrate 10A in which the inner layer circuit pattern 24 and the conductor pattern 25 are respectively formed on the inner two layers is prepared. The conductor pattern 25 is formed at the same depth as the bottomed hole to be formed. Then, the copper foil 18 is formed on both surfaces of the multilayer substrate 10A.

Referring to FIG. 22, the bottomed hole 14E is formed by sandblasting. A properly selected blast abrasive removes the copper foil 18 and allows the multi-layer substrate 10A
When the resin forming the is removed and reaches the conductor pattern 25, the processing speed of the sandblasting is drastically reduced. Therefore, when the sandblasting is completed and the sandblasting speed is drastically reduced, the bottomed hole having a predetermined depth can be easily formed.

(Embodiment 4) Embodiment 4 shows an example in which the present invention is applied to a method of manufacturing a photo-via method build-up substrate.

23 to 26 are sectional views for explaining a method for manufacturing a printed wiring board according to the fourth embodiment. Figure 2
3, the inner layer pattern 24A is formed on both surfaces of the core substrate 10B. Referring to FIG. 24, the core substrate 1
A photosensitive epoxy is formed as the photosensitive resin layer 26 so as to cover both sides of OB. Referring to FIG. 25, the developing process,
After the after-cure process, a via hole 27 is formed in the photosensitive resin layer 26 so that the inner layer pattern 24A is exposed. This process is the same as the normal photo via process. At the same time, the bottomed hole 14F is formed so that the core substrate 10B is exposed. Referring to FIG. 26, the conductor layer 16B is formed so as to cover the entire surface of the photosensitive resin layer 26 in which the photo via hole 27 and the bottomed hole 14F are formed. Then, the conductor layer 16B is etched to form a circuit pattern by the same steps as those described above with reference to FIGS. 6 to 7 in the first embodiment, and the core substrate 10B is formed along the end surface intersecting the bottomed hole 14F. When cut, the bottomed hole 14
The printed wiring board on which F is formed is completed.

The photosensitive resin layers 26 are formed on the opposite sides of the core substrate 10B with respect to the inner layer patterns 24A formed on both surfaces of the core substrate 10B and the inner layer circuit patterns 24A, respectively, and the conductor layer 16B is etched. It acts as an insulating resin layer that insulates the formed circuit pattern from each other. Each photo via hole 27 has an inner layer pattern 24.
A and the circuit patterns formed on the opposite side of the core mother substrate 10B with respect to each inner layer circuit pattern 24A and formed by etching the conductor layer 16B are electrically connected to each other.

Although the example in which the core substrate 10B is used is shown, a multilayer substrate having four or more layers may be used. In addition, the via hole, which will be the inner via hole, is formed by the photosensitive resin 2.
6 may be formed.

(Fifth Embodiment) In the printed wiring board according to the fifth embodiment, the adhesion state of the plated metal formed in the bottomed hole is improved.

FIG. 27 is a sectional view for explaining the method for manufacturing the printed wiring board according to the fifth embodiment. Embodiment 4
In FIG. 5, the same components as those of the printed wiring board described above are designated by the same reference numerals. Detailed description of these components will be omitted. FIG. 27 shows the fourth embodiment.
In the same manner as in FIG. 25 described above, the state in which the via hole and the bottomed hole are formed in the photosensitive resin layer 26 is shown. The difference from FIG. 25 is that the conductor pattern 25A is exposed at the bottom of the bottomed hole 14G.

FIG. 28 is a sectional view for explaining a bottomed hole 14G formed in the printed wiring board according to the fifth embodiment. Conductor pattern 25 exposed at the bottom of the bottomed hole 14G
When a plating current is applied to A, the electrolytic plating 29 formed on the electroless plating 28 completely covers the inner surface of the bottomed hole 14G. Therefore, there is no risk of defective plating.

29 and 30 are cross-sectional views for explaining a bottomed hole formed in the printed wiring board according to the comparative example. Since the conductor pattern 25A is not exposed at the bottom of the bottomed hole 14G and the plating current is not supplied, the hole diameter is small due to the high density and narrow pitch wiring. There is a risk that it will not enter 14G sufficiently. In this case, the electroless plating 28 is not completely deposited in the bottomed hole 14G.

When electrolytic copper plating is performed in this state,
A plating failure occurs in which the inner surface of the bottomed hole 14G is not completely covered by the electrolytic plating 29. In order to prevent such defective plating, a method of swinging the substrate during plating and a method of spraying a plating solution with a nozzle are known, but the bottom like the bottomed hole according to the present embodiment is used. For the relatively deep holes that it has, it is difficult to completely electrolytically coat the inner surface by such a method.

In the fifth embodiment, when a plating current is applied to the conductor pattern 25A exposed at the bottom of the bottomed hole 14G, even if the underlying electroless plating 28 is not completely formed. Since the electrolytic plating 29 completely covers the inner surface of the bottomed hole 14G, there is no risk of defective plating.

Japanese Unexamined Patent Publication No. 5-335712 discloses a structure in which a plating current is passed through a conductor pattern exposed at the bottom of a through hole. However, the structure disclosed in the above-mentioned publication is such that a plating current is passed through the conductor pattern. In contrast to the configuration in which the plated metal is formed so as to completely fill the inside of the through hole, the present invention is different in that the plated metal is formed so as to completely cover the inner surface of the bottomed hole.

FIG. 31 is a sectional view of another printed wiring board according to the fifth embodiment. The same components as those of the printed wiring board according to the fourth embodiment described above with reference to FIGS. 25 and 26 are designated by the same reference numerals.
Detailed description of these components will be omitted.

The printed wiring board has a core substrate 11B made of resin. Inner layer patterns 24B are formed on both surfaces of the core substrate 11B. A photosensitive epoxy is formed as a photosensitive resin layer 26 on both surfaces of the core substrate 11B so as to cover the inner layer pattern 24B. A circuit pattern is formed on the surface of each photosensitive resin layer 26. A via hole 27 is formed in each photosensitive resin layer 26 so that the inner layer pattern 24B is exposed. The bottomed hole 14 is formed on one end surface of the photosensitive resin layer 26.
H is formed. The inner layer pattern 24B is exposed at the bottom of the bottomed hole 14H. On the inner surface of the bottomed hole 14H,
The conductor 16C is formed. The conductor 16C is connected to the inner layer pattern 24B exposed at the bottom of the bottomed hole 14H.

As described above, since the conductor 16C formed on the inner surface of the bottomed hole 14H is directly connected to the inner layer pattern 24B, the inner layer pattern 24B is connected to the via hole 27.
It is not necessary to connect to the circuit pattern formed on the surface of the photosensitive resin layer 26 via the. Therefore, via hole 2
The number of 7 can be reduced, and the inner layer circuit pattern 24B
Further, it is possible to improve the wiring flexibility and wiring density of the circuit pattern formed on the surface of the photosensitive resin layer 26.

Since the conductor 16C formed on the inner surface of the bottomed hole 14H is directly connected to the inner layer circuit pattern 24B, the bottomed hole 14H is formed in the final contour processing step.
When the core substrate 11B is cut along the end surface intersecting with, the inner layer circuit pattern 24B presses the conductor 16C formed on the inner surface of the bottomed hole 14H. Therefore, the conductor 1
6C can be prevented from peeling from the inner surface of the bottomed hole 14H during cutting.

Japanese Unexamined Patent Publication No. 6-338670 discloses a structure in which a conductor formed on the inner surface of a through hole is connected to an inner layer copper foil (wedge). However, in the structure disclosed in the above-mentioned publication, While the end surface of the inner layer copper foil is connected to the conductor, the present embodiment is different in that the surface of the inner layer circuit pattern 24B is connected to the conductor 16C. Since the surface of the inner layer circuit pattern 24B is connected to the conductor 16C, the connection area is larger than that in the configuration described in the above publication in which the end face is connected to the conductor, so that the conductor 16C has the bottomed hole 14H. It is possible to prevent peeling from the inner surface of the.

FIG. 32 is a sectional view of still another printed wiring board according to the fifth embodiment. FIG. 32 shows another example in which the surface of the inner layer circuit pattern is connected to the conductor formed on the inner surface of the bottomed hole. The printed wiring board includes a multi-layer board 11C having four layers. The four layers forming the multilayer substrate 11C are formed stepwise on one end face of the multilayer substrate 11C and form a bottomed hole 14I. Inner layer circuit patterns 24C are respectively formed on the inner two layers, and the surface of each inner layer circuit pattern 24C is exposed at one end face of the multi-layer substrate 11C formed in a step shape. In this way, the inner layer circuit pattern 2
The surface of No. 4 is exposed stepwise in the bottomed hole 14I. A conductor layer 16D is formed in a step shape on the inner surface of the bottomed hole 14I and is connected to the surface of each inner layer circuit pattern 24 exposed in the step shape.

As described above, since the conductor layer 16D is connected to the surface of each inner layer circuit pattern 24 exposed in a stepwise manner, the connection area between the conductor layer and the inner layer circuit pattern can be further increased. it can.

The stepwise structure shown in FIG. 32 can be realized by the sandblast method described above, and can also be realized by the photovia method described above. When using the sandblast method, each inner layer circuit pattern 24
Are formed in a stepwise manner in advance, and each inner layer circuit pattern 24
The blasting may be performed from above toward the above, and the blasting may be finished based on the change in the polishing rate. When the photo via method is used, the photosensitive resin may be formed stepwise so that the inner layer circuit patterns 24 are exposed stepwise in the bottomed holes.

[0084]

As described above, according to the present invention, there is provided a printed wiring board and a method of manufacturing the same, in which the plating solution for forming the conductor on the inner wall of the end face through hole can sufficiently enter into the end face through hole. Can be provided.

Further, according to the present invention, it is possible to provide a printed wiring board capable of increasing the connection strength between the end face through hole and the parent board, and a method for manufacturing the same.

Further, according to the present invention, it is possible to provide a printed wiring board and a method for manufacturing the same, which can increase the adhesion strength of the plated metal to the inner wall of the end face through hole.

Further, according to the present invention, it is possible to provide a printed wiring board capable of processing the through-holes on the end face while maintaining the strength of the substrate, and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a perspective view of a printed wiring board according to a first embodiment.

FIG. 2 is a sectional view showing a mounting example of the printed wiring board according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating the method for manufacturing the printed wiring board according to the first embodiment.

FIG. 4 is a sectional view illustrating the method for manufacturing the printed wiring board according to the first embodiment.

FIG. 5 is a sectional view illustrating the method for manufacturing the printed wiring board according to the first embodiment.

FIG. 6 is a sectional view illustrating the method for manufacturing the printed wiring board according to the first embodiment.

FIG. 7 is a sectional view illustrating the method for manufacturing the printed wiring board according to the first embodiment.

FIG. 8 is a cross-sectional view showing another mounting example of the printed wiring board according to the first embodiment.

FIG. 9 is a sectional view illustrating the method for manufacturing the printed wiring board according to the second embodiment.

FIG. 10 is a sectional view illustrating a method for manufacturing a printed wiring board according to a second embodiment.

FIG. 11 is a sectional view illustrating the method for manufacturing the printed wiring board according to the second embodiment.

FIG. 12 is a cross-sectional view illustrating the method for manufacturing the printed wiring board according to the second embodiment.

FIG. 13 is a schematic plan view illustrating another method for manufacturing a printed wiring board according to the second embodiment.

FIG. 14 is a schematic plan view illustrating another method for manufacturing a printed wiring board according to the second embodiment.

FIG. 15 is a schematic perspective view of still another printed wiring board according to the second embodiment.

FIG. 16 is a schematic plan view illustrating another method for manufacturing a printed wiring board according to the second embodiment.

FIG. 17 is a schematic plan view illustrating another method for manufacturing a printed wiring board according to the second embodiment.

FIG. 18 is a schematic perspective view of still another printed wiring board according to Embodiment 2.

FIG. 19 is a schematic plan view illustrating a method for manufacturing a printed wiring board according to a comparative example.

FIG. 20 is a schematic perspective view of a printed wiring board according to a comparative example.

FIG. 21 is a sectional view illustrating the method for manufacturing the printed wiring board according to the third embodiment.

FIG. 22 is a sectional view illustrating the method for manufacturing the printed wiring board according to the third embodiment.

FIG. 23 is a sectional view illustrating the method for manufacturing the printed wiring board according to the fourth embodiment.

FIG. 24 is a sectional view illustrating the method for manufacturing the printed wiring board according to the fourth embodiment.

FIG. 25 is a sectional view illustrating the method for manufacturing the printed wiring board according to the fourth embodiment.

FIG. 26 is a sectional view illustrating the method for manufacturing the printed wiring board according to the fourth embodiment.

FIG. 27 is a sectional view of a printed wiring board according to a fifth embodiment.

FIG. 28 is a cross-sectional view illustrating a bottomed hole formed in a printed wiring board according to Embodiment 5.

FIG. 29 is a cross-sectional view illustrating a bottomed hole formed in a printed wiring board according to a comparative example.

FIG. 30 is a cross-sectional view illustrating a bottomed hole formed in a printed wiring board according to a comparative example.

FIG. 31 is a sectional view of another printed wiring board according to the fifth embodiment.

FIG. 32 is a sectional view of still another printed wiring board according to Embodiment 5;

FIG. 33 is a perspective view of a conventional printed wiring board.

FIG. 34 is a sectional view illustrating a mounting example of a conventional printed wiring board.

FIG. 35 is a sectional view illustrating a conventional method for manufacturing a printed wiring board.

FIG. 36 is a sectional view illustrating a conventional method for manufacturing a printed wiring board.

FIG. 37 is a cross-sectional view illustrating a conventional method for manufacturing a printed wiring board.

FIG. 38 is a cross-sectional view illustrating the conventional method for manufacturing a printed wiring board.

FIG. 39 is a perspective view illustrating a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

10 substrates 11 board 12 circuit patterns 13 End face 14 bottomed holes 15 bottom 16 conductor 16A conductor layer 17 cutting line 24 Inner layer circuit pattern 25 conductor pattern 28 Electroless plating 29 Electroplating

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E317 AA04 AA22 AA25 BB01 BB11                       CC32 CC33 CD32 GG07 GG20                 5E346 AA29 AA32 BB16 CC01 CC31                       CC57 CC58 DD25 DD32 FF15                       FF42 GG15 GG17 GG26 HH07                       HH11 HH33 HH40

Claims (15)

[Claims] 1. An end face through hole is formed on an end face of a substrate on which a circuit pattern is formed, the end face through hole having a bottom so as to be in a non-penetrating state in the thickness direction of the substrate. A conductor electrically connected to the circuit pattern is formed in the end-face through hole, and the plane shape of the end-face through hole is a semicircular shape, a semi-elliptical shape, a semi-elliptical shape, a rectangular shape, and A printed wiring board having a triangular shape. 2. The printed wiring board according to claim 1, wherein the end face through hole is formed by any one of sandblasting and photo via method. 3. The printed wiring board according to claim 1, wherein a circuit pattern connected to the end face through hole is formed on a surface of the substrate. 4. The substrate has a laminated structure of at least three layers, and the circuit pattern connected to the end face through hole is formed in a layer provided inside the laminated structure, The printed wiring board according to claim 1, wherein the body is connected to a circuit pattern formed on a layer provided inside the body. 5. The printed wiring board according to claim 1, wherein the circuit pattern is formed so as to be exposed at a bottom of the end face through hole and is connected to the conductor formed in the end face through hole. 6. A preparatory step of preparing a copper-clad laminate or a multilayer wiring board on which an outer layer pattern is not formed, a through-hole forming step of forming a through hole having a bottom along the thickness direction of the board, and a through hole forming step. A conductor layer forming step of forming a conductor layer so as to cover the side wall and the bottom surface and a surface of the substrate; and an etching step of etching the conductor layer formed on the surface of the substrate to form a circuit pattern. And a cutting step of forming an end face through hole by cutting the substrate along an end face intersecting with the through hole after the etching step. 7. The through-hole forming step forms the through-hole by sandblasting.
A method for manufacturing the printed wiring board described. 8. The method further comprises the step of forming a conductor pattern for controlling the working depth of the sandblasting at a predetermined depth position along the thickness direction of the substrate before the through hole forming step. The method of manufacturing a printed wiring board according to claim 7, wherein in the through hole forming step, the end surface through hole is formed at the predetermined depth so that the conductor pattern is exposed. 9. In the step of forming the conductor layer, electroless plating is performed on the entire surface of the substrate and the inner wall of the through hole, and then electroplating is performed to form the conductor layer. The method for manufacturing a printed wiring board according to claim 8, wherein a plating voltage is applied to the conductive layer and the conductor pattern exposed at the bottom of the end face through hole. 10. The method of manufacturing a printed wiring board according to claim 6, wherein the through hole is formed by a photo via method in the through hole forming step. 11. The method for manufacturing a printed wiring board according to claim 6, wherein in the conductor layer forming step, the conductor layer is formed by electroless plating. 12. The conductor layer forming step forms the conductor layer by either sputtering or vapor deposition.
The method for manufacturing a printed wiring board according to claim 6. 13. The method further comprises the step of forming an inner layer circuit pattern at a predetermined depth position along the thickness direction of the substrate before the through hole forming step. The through hole is formed so that the inner layer circuit pattern is exposed, and the conductor forming step forms the conductor so as to be connected to the inner layer circuit pattern exposed in the through hole.
The method for manufacturing a printed wiring board according to claim 6. 14. The through hole formed in the through hole forming step has an elliptical planar shape, and the end surface through hole after the substrate has been cut in the cutting step has a semicircular planar shape. The method for manufacturing a printed wiring board according to claim 6, which has a shape. 15. The printed wiring according to claim 6, wherein the through hole formed in the through hole forming step has a planar shape of any one of an elliptical shape, an elliptical shape, a rectangular shape, and a triangular shape. Method of manufacturing a plate.