JP7032128B2 - Manufacturing method of printed wiring board and printed wiring board - Google Patents

Description

The present invention relates to a printed wiring board and a method for manufacturing a printed wiring board.

In recent years, the miniaturization of electronic devices has progressed, and there is a demand for high-density wiring of printed wiring boards used in electronic devices. In response to such a demand, a multilayer printed wiring board having a plurality of patterned conductive layers is often used. The multilayer printed wiring board often has a via hole that connects patterns of different conductive layers by forming a hole penetrating the base material layer and forming a metal layer by plating on the inner peripheral surface of the hole.

In order to further increase the wiring density of such a multilayer printed wiring board, it is also necessary to reduce the diameter of the via hole. However, if the diameter of the via hole is reduced, air bubbles are left behind in the holes formed in the base material layer and the plating solution cannot be introduced, which may cause poor connection between the conductive layers.

In particular, when a blind via hole that can reduce the installation area because it is not necessary to form a land on one side of the conductive layer is adopted, air bubbles are likely to be left behind in the hole of the base material layer, and the connection between the conductive layers is poor. Is likely to occur.

On the other hand, when forming a blind via hole, a technique has been proposed in which a tapered hole is formed by a drill having a diameter gradually expanding from the tip portion to promote defoaming and ensure plating. (See JP-A-5-82969).

Japanese Unexamined Patent Publication No. 5-82969

As disclosed in the above publication, the method using a drill cannot sufficiently reduce the diameter of the via hole, so that there is a limit to high-density wiring.

Further, as a result of verification by the inventors of the present application, when the diameter of the hole is as small as 100 μm or less, it is not possible to ensure the introduction of the plating solution only by making the hole tapered, and the connection between the conductive layers is poor. Was confirmed to occur.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a printed wiring board and a method for manufacturing a printed wiring board in which the connection between conductive layers by via holes is reliable.

The printed wiring board according to one aspect of the present invention, which has been made to solve the above-mentioned problems, has a first surface, which is laminated on one surface of an insulating base material layer and the base material layer, and has a connecting land. The conductive layer, the second conductive layer laminated on the other surface of the base material layer, the inner peripheral surface of the connection hole, the inner peripheral surface of the connection hole penetrating the base material layer in the thickness direction, and the connection land. It is provided with a via hole that is continuously laminated on the surface opposite to the base material layer and the surface of the second conductive layer to electrically connect the first conductive layer and the second conductive layer, and the connection of the via hole. The outer shape of the first laminated portion laminated on the surface of the land is irregular.

Further, in the method for manufacturing a printed wiring board according to another aspect of the present invention, a base material layer having an insulating property, a first conductive layer laminated on one surface of the base material layer and having a connecting land, and a first conductive layer. The second conductive layer laminated on the other surface of the base material layer, the inner peripheral surface of the connection land and the connection hole penetrating the base material layer in the thickness direction, and the base material layer of the connection land. A method for manufacturing a printed wiring board, which is continuously laminated on the surface opposite to the surface of the second conductive layer and the surface of the second conductive layer, and has a via hole for electrically connecting the first conductive layer and the second conductive layer. The step of forming a connection hole penetrating the first conductive layer and the base material layer in the thickness direction, and covering the first conductive layer to expose at least a portion of the first conductive layer adjacent to the connection hole. The present invention includes a step of forming a resist pattern having an irregularly shaped opening and a step of introducing a plating solution from the opening of the resist pattern into the connection hole.

The printed wiring board according to one aspect of the present invention and the printed wiring board obtained by the manufacturing method according to another aspect of the present invention are surely connected between conductive layers by via holes.

FIG. 1 is a schematic cross-sectional view showing a printed wiring board according to an embodiment of the present invention. FIG. 2 is a schematic plan view of the printed wiring board of FIG. FIG. 3 is a schematic plan view showing a printed wiring board different from that of FIG. FIG. 4 is a schematic plan view showing a printed wiring board different from FIGS. 2 and 3. FIG. 5 is a schematic plan view showing a printed wiring board different from FIGS. 2 to 4. FIG. 6 is a schematic plan view showing a printed wiring board different from FIGS. 2 to 5.

[Explanation of Embodiment of the present invention]
The printed wiring board according to one aspect of the present invention has an insulating base material layer, a first conductive layer laminated on one surface of the base material layer and having a connecting land, and the other of the base material layers. The second conductive layer laminated on the surface of the above, the inner peripheral surface of the connection hole penetrating the connection land and the base material layer in the thickness direction, the surface of the connection land opposite to the base material layer, and the surface of the connection land. A first that is continuously laminated on the surface of the second conductive layer, includes a via hole that electrically connects the first conductive layer and the second conductive layer, and is laminated on the surface of the connection land of the via hole. The outer shape of the laminated portion is an irregular shape.

The printed wiring board has an irregular outer shape of the first laminated portion laminated on the surface of the connecting land of the via hole, so that when the via hole is formed by plating, the printed wiring board is formed on the outer surface of the connecting land. The resist pattern having an opening having a shape corresponding to the outer shape of the first laminated portion is immersed in the plating solution in a laminated state. For this reason, the flow of the plating solution around the connection hole becomes irregular, and the plating solution flows irregularly into the connection hole, which disrupts the balance of the interface between the air and the plating solution in the connection hole. The air in the connection hole can be efficiently expelled by the plating solution. As a result, in the printed wiring board, the via holes in the connection holes have a uniform thickness, so that the electrical connection between the first conductive layer and the second conductive layer is reliable.

The printed wiring board may have an expansion portion in which the outer shape of the first laminated portion is partially extended outward. As described above, by having the expanded portion in which the outer shape of the first laminated portion is partially expanded outward, the flow velocity of the plating solution flowing into the opening of the resist pattern forming the first laminated portion is effectively applied. It can be scattered. Therefore, the flow of the plating solution flowing into the connection hole becomes more irregular, and the electrical connection between the first conductive layer and the second conductive layer by the via hole can be made more reliable.

In the printed wiring board, the planar shape of the expansion portion may be arcuate. As described above, since the planar shape of the extended portion is arcuate, it is possible to relatively easily form an opening of the resist pattern corresponding to the first laminated portion of the via hole.

In the printed wiring board, a plurality of the expansion portions may be formed at intervals in the circumferential direction. By forming a plurality of the expansion portions at intervals in the circumferential direction in this way, the air in the connection hole is effectively expelled and uniform regardless of the flow direction of the entire plating solution in the plating bath. Via holes of thickness can be formed.

In the printed wiring board, the outer shape of the first laminated portion may be a polygonal shape. As described above, since the outer shape of the first laminated portion is polygonal, the opening of the resist pattern corresponding to the first laminated portion of the via hole can be easily formed, and the area of the first laminated portion can be easily formed. The ratio of the land area of the first conductive layer can be made relatively small.

A method for manufacturing a printed wiring board according to another aspect of the present invention includes a base material layer having an insulating property, a first conductive layer laminated on one surface of the base material layer and having a connecting land, and the base material. The second conductive layer laminated on the other surface of the material layer, the inner peripheral surface of the connection hole penetrating the connection land and the base material layer in the thickness direction, and the opposite of the base material layer of the connection land. A method for manufacturing a printed wiring board, which is continuously laminated on a side surface and a surface of the second conductive layer, and has a via hole for electrically connecting the first conductive layer and the second conductive layer. 1 A step of forming a connection hole penetrating the conductive layer and the base material layer in the thickness direction, and a deformed shape that covers the first conductive layer and exposes at least a portion of the first conductive layer adjacent to the connection hole. The present invention includes a step of forming a resist pattern having an opening of the above, and a step of introducing a plating solution from the opening of the resist pattern into the connection hole.

In the method of manufacturing the printed wiring board, a resist pattern having an irregularly shaped opening that exposes at least a portion of the first conductive layer adjacent to the connection hole is formed, and a plating solution is formed from the opening of the resist pattern into the connection hole. Due to the irregular shape of the opening of the resist pattern, the plating solution flows irregularly into the connection hole. Therefore, in the method of manufacturing the printed wiring board, the equilibrium of the interface between the air in the connection hole and the plating solution is broken, and the air in the connection hole is efficiently expelled by the plating solution. Via holes of uniform thickness can be formed on the inner peripheral surface. Therefore, according to the method for manufacturing the printed wiring board, it is possible to obtain a printed wiring board in which the electrical connection between the first conductive layer and the second conductive layer by the via hole is reliable.

[Details of Embodiments of the present invention]
Hereinafter, each embodiment of the printed wiring board and the method for manufacturing the printed wiring board according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]
1 and 2 show a printed wiring board according to an embodiment of the present invention. The printed wiring board is a flexible printed wiring board having flexibility.

The printed wiring board has an insulating base material layer 1, a first conductive layer 2 laminated on one side surface of the base material layer 1, and a first layer laminated on the other side surface of the base material layer 1. 2 The conductive layer 3 is provided with a via hole 4 that penetrates the base material layer 1 and electrically connects the first conductive layer 2 and the second conductive layer 3.

The printed wiring board has a connection hole 5 formed so as to penetrate the base material layer 1 and the first conductive layer 2 in the thickness direction in order to dispose the via hole 4.

The first conductive layer 2 is connected to a first connection land 6 and a first connection land 6 in which a connection hole 5 is formed inside the connection hole 5 in a plan view and a via hole 4 is connected to a peripheral region of the connection hole 5. It has a strip-shaped first wiring pattern 7. Further, the first conductive layer 2 may have another configuration such as a land for mounting an electronic component.

The second conductive layer 3 has a second connection land 8 to which the via hole 4 is connected to the inside thereof in a plan view, and a strip-shaped second wiring pattern 9 connected to the second connection land 8. Further, the second conductive layer 3 may have another configuration such as a land for mounting an electronic component.

The via hole 4 is a blind via hole that does not penetrate the second conductive layer 3. The via hole 4 is formed in at least the connection hole 5 of the through portion 10 laminated on the inner peripheral surface of the connection hole 5 and the surface of the first conductive layer 2 on the opposite side of the base material layer 1 of the first connection land 6. It has a first laminated portion 11 laminated in an adjacent region and a second laminated portion 12 laminated in a portion exposed inside the connection hole 5 of the second conductive layer 3.

The outer shape of the first laminated portion 11 of the via hole 4 in a plan view is a deformed shape, that is, a shape different from a circular shape.

The printed wiring board has a deformed outer shape of the first laminated portion 11 laminated on the surface of the first connection land 6 of the via hole 4, so that the first connection is made when the via hole 4 is formed by plating. A resist pattern having an opening having a shape corresponding to the outer shape of the first laminated portion 11 is laminated on the outer surface of the land 6 and is immersed in the plating solution. For this reason, the flow of the plating solution around the connection hole 5 becomes irregular due to the irregular shape of the opening of the resist pattern, and the plating solution flows irregularly into the connection hole 5, so that the connection hole 5 is used. It breaks the balance of the interface between the air inside and the plating solution, prevents the air inside the connecting hole 5 from being left behind as dome-shaped bubbles, and makes the air inside the connecting hole 5 more efficient with the plating solution. You can get rid of it well. As a result, in the printed wiring board, the through portion 10 and the first laminated portion 11 of the via hole 4 laminated in the connection hole 5 have a uniform thickness, so that the first conductive layer 2 and the second conductive layer 3 are formed. The electrical connection is secure.

Hereinafter, each component of the printed wiring board will be described in detail.

<Base layer>
Examples of the material of the base material layer 1 include polyamide, polyimide, polyamideimide, and polyester. Among them, polyamide, polyimide and polyamide-imide are preferably used in terms of mechanical strength such as heat resistance.

As the lower limit of the average thickness of the base material layer 1, 5 μm is preferable, and 10 μm is more preferable. On the other hand, the upper limit of the average thickness of the base material layer 1 is preferably 500 μm, more preferably 150 μm. If the average thickness of the base material layer 1 is less than the above lower limit, the strength of the base material layer 1 may be insufficient. On the contrary, when the average thickness of the base material layer 1 exceeds the above upper limit, the flexibility may be insufficient.

<First conductive layer>
The first conductive layer 2 is formed by patterning a layered conductor laminated on one surface side of the base material layer 1.

The material forming the first conductive layer 2 is not particularly limited as long as it is a conductive material, and examples thereof include metals such as copper, aluminum, and nickel, which are generally relatively inexpensive and have high conductivity. Copper is used. Further, the surface of the first conductive layer 2 may be plated.

The lower limit of the average thickness of the first conductive layer 2 is preferably 2 μm, more preferably 5 μm. On the other hand, the upper limit of the average thickness of the first conductive layer 2 is preferably 500 μm, more preferably 100 nm. If the average thickness of the first conductive layer 2 is less than the above lower limit, the conductivity may be insufficient. On the other hand, if the average thickness of the first conductive layer 2 exceeds the above upper limit, the flexibility may be insufficient.

(Land for 1st connection)
The first connection land 6 of the first conductive layer 2 is usually formed in a circular shape in a plan view, and a connection hole 5 is formed in the center thereof.

The first connection land 6 is formed in a size that includes the first laminated portion 11 of the via hole 4, which will be described later, in a plan view.

(1st wiring pattern)
The first wiring pattern 7 of the first conductive layer 2 extends in a band shape from the first connection land 6.

The lower limit of the average width of the first wiring pattern 7 is preferably 10 μm, more preferably 15 μm. On the other hand, the upper limit of the average width of the first wiring pattern 7 is preferably 5000 μm, more preferably 1000 μm. If the average width of the first wiring pattern 7 is less than the above lower limit, the wiring pattern may be broken. On the contrary, when the average width of the first wiring pattern 7 exceeds the above upper limit, the connection hole 5 is enlarged to ensure the connection between the first conductive layer 2 and the second conductive layer 3 without applying the present invention. Therefore, the advantages of the present invention may be impaired.

<Second conductive layer>
The second conductive layer 3 is formed by patterning a layered conductor laminated on the side opposite to the first conductive layer 2 of the base material layer 1.

The material forming the second conductive layer 3 and the average thickness of the second conductive layer 3 can be the same as the material forming the first conductive layer 2 and the average thickness of the first conductive layer 2.

(Land for 2nd connection)
The second connection land 8 of the second conductive layer 3 is usually formed in a circular shape in a plan view concentric with the connection hole 5. When the connection hole 5 is relatively small, the second connection land 8 may be a part of the second wiring pattern 9 described later and may be indistinguishable in appearance.

(2nd wiring pattern)
The second wiring pattern 9 of the second conductive layer 3 extends in a band shape from the second connection land 8.

The average width of the second wiring pattern 9 can be the same as the average width of the first wiring pattern 7.

<Connection hole>
The connection hole 5 is formed so as to penetrate the base material layer 1, the first conductive layer 2, and the second conductive layer 3 described above in the thickness direction. The connection hole 5 can be formed so that the cross section has a constant circular shape.

As a method for forming the connection hole 5, for example, punching, drilling, laser machining, or the like can be adopted.

The lower limit of the average diameter (corresponding to a circle) of the connection hole 5 is preferably 20 μm, more preferably 50 μm. On the other hand, the upper limit of the average diameter of the connection hole 5 is preferably 300 μm, more preferably 150 μm. When the average diameter of the connection hole 5 is less than the above lower limit, the air in the connection hole 5 cannot be expelled by the plating solution when the via hole 4 is formed, and the inner surface of the connection hole 5 cannot be plated. There is a possibility that the conductive layer 2 and the second conductive layer 3 cannot be reliably connected. On the contrary, when the average diameter of the connection hole 5 exceeds the above upper limit, the plating solution can be introduced into the connection hole 5 without making the first laminated portion 11 a deformed shape, and therefore the present invention is applied. May not be advantageous.

<Beer hall>
The penetration portion 10, the first laminated portion 11, and the second laminated portion 12 of the via hole 4 are integrally formed by plating so as to have a substantially constant thickness.

(1st laminated part)
The outer shape of the first laminated portion 11 of the present embodiment is formed into a polygonal shape. By forming the first laminated portion 11 in a polygonal shape in this way, it becomes relatively easy to form an opening of the resist pattern provided when the via hole 4 is formed by plating. Further, since the first laminated portion 11 has a polygonal shape, the ratio of the area of the first connecting land 6 of the first conductive layer 2 to the area of the first laminated portion 11 can be made relatively small. 1 Contributes to high-density wiring of the conductive layer 2.

More specifically, the outer shape of the first laminated portion 11 can be a regular polygon. As the lower limit of the number of corners (or sides) of the first laminated portion 11 having a regular polygonal shape, 5 is preferable, and 6 is more preferable. On the other hand, as the upper limit of the number of corners of the first laminated portion 11 having a regular polygonal shape, 12 is preferable, and 10 is more preferable. If the number of corners of the first laminated portion 11 having a regular polygonal shape is less than the above lower limit, the area of the first connecting land 6 may not be reduced. On the contrary, when the number of corners of the first laminated portion 11 having a regular polygonal shape exceeds the above upper limit, the outer shape of the first laminated portion 11 becomes too close to a circle, and the effect of making the flow of the plating solution irregular is insufficient. The connection between the first conductive layer 2 and the second conductive layer 3 by the via hole 4 may be uncertain.

The lower limit of the average outer diameter (diameter equivalent to a circle) of the first laminated portion 11 is preferably twice the average diameter of the connection hole 5 and more preferably three times. On the other hand, the upper limit of the average outer diameter of the first laminated portion 11 is preferably 5 times, more preferably 4 times, the average diameter of the connection hole 5. If the average outer diameter of the first laminated portion 11 is less than the above lower limit, the first laminated portion 11 may easily peel off from the first conductive layer 2. On the contrary, when the average outer diameter of the first laminated portion 11 exceeds the above upper limit, there is a possibility that the high-density wiring of the first conductive layer 2 is hindered.

Further, the via hole 4 is laminated on the inner peripheral surface of the connection hole 5, the surface of the first conductive layer 2 opposite to the base material layer 1, and the surface exposed inside the connection hole 5 of the second conductive layer 3. It is possible to have a configuration having a base conductor layer and a main conductor layer further laminated on the base conductor layer.

(Underground conductor layer)
The base conductor layer is a thin layer having conductivity, and is used as an adherend when the main conductor layer is formed by electroplating. This base conductor layer can be formed of a metal laminated by electroless plating. Examples of the metal forming the underlying conductor layer include metals such as copper, silver, nickel, and palladium. Among them, copper has good flexibility, thickening possibility, adhesion to electrolytic copper plating, and low electrical resistance. Is preferable.

When the base conductor layer is formed by electroless plating of copper, the lower limit of the average thickness of the base conductor layer is preferably 0.01 μm, more preferably 0.2 μm. On the other hand, the upper limit of the average thickness of the underlying conductor layer is preferably 1 μm, more preferably 0.5 μm. If the average thickness of the base conductor layer is less than the above lower limit, the continuity of the base conductor layer cannot be ensured, and the main conductor layer may not be formed uniformly. Further, if the average thickness of the underlying conductor layer exceeds the above upper limit, the cost may increase unnecessarily.

(Main conductor layer)
The main conductor layer is formed of a metal laminated on the base conductor layer by electroplating. By forming the base conductor layer in this way and then providing the main conductor layer on the inner peripheral surface thereof, the via hole 4 having excellent conductivity can be easily and surely formed.

Examples of the metal forming the main conductor layer include copper and nickel, and among them, copper, which is inexpensive and has low electrical resistance, is preferably used.

As the lower limit of the average thickness of the main conductor layer, 1 μm is preferable, and 5 μm is more preferable. On the other hand, the upper limit of the average thickness of the main conductor layer is preferably 50 μm, more preferably 30 μm. When the average thickness of the main conductor layer is less than the above lower limit, the via hole 4 is broken due to bending or the like of the printed wiring board 1, and the electrical connection between the first conductive layer 2 and the second conductive layer 3 is cut off. There is a risk of Further, when the average thickness of the main conductor layer exceeds the above upper limit, the printed wiring board 1 may become excessively thick or the manufacturing cost may increase unnecessarily.

<Advantage>
As described above, the printed wiring board has a constant thickness due to the irregular shape of the first laminated portion 11 of the via hole 4, so that the plating solution expels the air in the connection hole 5 when the via hole 4 is formed. Since the via hole 4 can be formed, the electrical connection between the first conductive layer 2 and the second conductive layer 3 is reliable.

[Manufacturing method of printed wiring board]
The printed wiring board itself can be manufactured by a manufacturing method which is another embodiment of the present invention.

The method for manufacturing the printed wiring board includes a step of preparing a laminate having a base material layer 1, an unpatterned first conductive layer 2 and a second conductive layer 3, a <laminate preparation step>, and a first conductive layer 2. And the step of forming the connection hole 5 penetrating the base material layer 1 in the thickness direction <connection hole forming step>, and the portion of the first conductive layer 2 that covers at least the connection hole 5 and is adjacent to the connection hole 5. A step of forming a resist pattern having a deformed opening corresponding to the first laminated portion 11 of the via hole 4 by exposing the via hole <resist pattern forming step> and a via hole by introducing a plating solution into the connection hole 5 from the opening of the resist pattern. 4 is provided with a step of forming the via hole <via hole forming step> and a step of patterning the first conductive layer 2 and the second conductive layer 3 <patterning step>.

<Laminate preparation process>
In the laminate preparation step, a laminate in which the first conductive layer 2, the base material layer 1, and the second conductive layer 3 are laminated in this order is prepared.

The method of laminating the conductors constituting the first conductive layer 2 and the second conductive layer 3 on the base material layer 1 is not particularly limited, and for example, a bonding method in which a sheet-shaped conductor is bonded with an adhesive, a sheet-shaped conductor A metal by plating on a thin conductive layer (seed layer) having a thickness of several nm formed on the base material layer 1 by a casting method, a sputtering method or a vapor deposition method in which a resin composition which is a material of the base material layer 1 is applied onto the base material layer 1. A sputter / plating method for forming a conductor layer, a laminating method in which a sheet-shaped conductor is attached to the base material layer 1 by a hot press, or the like can be used.

<Connection hole forming process>
In the connection hole forming step, a connection hole 5 penetrating the base material layer 1 and the first conductive layer 2 is formed in the laminated body.

As a method for forming such a connection hole 5, known methods such as punching, laser processing, and drilling can be applied.

<Resist pattern forming process>
In the resist pattern forming step, a resist pattern having an irregularly shaped opening corresponding to the first laminated portion 11 is formed on the outer surface of the first conductive layer 2 (the surface opposite to the base material layer 1) by using photolithography technology. do. Further, the outer surface of the second conductive layer 3 (the surface opposite to the base material layer 1) also forms a resist pattern.

<Beer hall forming process>
A step of laminating the base conductor layer on the portion exposed from the resist pattern of the laminate (base conductor layer laminating step) and a step of laminating the main conductor layer on the surface of the base conductor layer (main conductor layer laminating step). Have.

(Underground conductor layer laminating process)
In the base conductor layer laminating step, the base conductor layer is formed on the inner peripheral surface of the connection hole 5 and the outer surface of the first conductive layer 2 (the surface opposite to the base material layer 1) by electroless plating.

The electroless plating for forming the underlying conductor layer is a process of precipitating a metal having catalytic activity by the reducing action of the catalyst, and can be performed by applying various commercially available electroless plating solutions. By forming the base conductor layer using electroless plating in this way, the base conductor layer can be easily laminated, and the main conductor layer can be further laminated.

(Main conductor layer laminating process)
In the main conductor layer laminating step, a main conductor layer is formed by laminating metal in the openings of the resist pattern by electroplating with the underlying conductor layer as an adherend, and a via hole 4 having a sufficient thickness is formed.

In the main conductor layer laminating step, it is assumed that a plurality of the laminated bodies having a resist pattern formed are held at intervals in the thickness direction and immersed in a plating bath to perform electroplating. Therefore, the plating solution is supplied from one direction along the surface of the laminated body to the opening of the resist pattern, and the plating solution is introduced into the connection hole 5 from the opening of the resist pattern.

<Patterning process>
In the patterning step, the first conductive layer 2 and the second conductive layer 3 are selectively removed to form a conductive pattern. As a method for selectively removing the first conductive layer 2 and the second conductive layer 3, for example, a resist pattern in which the portion where the first conductive layer 2 and the second conductive layer 3 should be removed is opened by photolithography is formed. A known method for dissolving the first conductive layer 2 and the second conductive layer 3 exposed in the opening of the resist pattern by etching can be applied.

In this patterning step, the outer peripheral portion of the irregularly shaped first laminated portion 11 formed in the via hole forming step may be removed together with the first conductive layer 2 to make the outer shape of the first laminated portion 11 circular. That is, the method for manufacturing the printed wiring board can also be used for manufacturing a printed wiring board other than the printed wiring board according to the present invention.

<Advantage>
In the method of manufacturing the printed wiring board, a resist pattern having an irregularly shaped opening is formed, and the plating solution is introduced into the connection hole 5 from the irregularly shaped opening. Therefore, when the plating solution flows into the opening of the resist pattern. Due to the irregular flow, the flow velocity of the plating solution flowing into the connection hole 5 varies. This prevents the air in the connection hole 5 from being left behind as dome-shaped bubbles, and the air in the connection hole 5 can be efficiently expelled by the plating solution. Therefore, in the method for manufacturing the printed wiring board, the via hole 4 having the through portion 10 and the first laminated portion 11 having a uniform thickness can be formed in the connection hole 5, so that the first conductive layer 2 and the second are formed. It is possible to manufacture a printed wiring board having a reliable electrical connection with the conductive layer 3.

[Second Embodiment]
FIG. 3 shows a printed wiring board according to an embodiment of the present invention. The printed wiring board is a flexible printed wiring board having flexibility.

The printed wiring board has an insulating base material layer 1, a first conductive layer 2 laminated on one side surface of the base material layer 1, and a first layer laminated on the other side surface of the base material layer 1. 2 The conductive layer 3 is provided with a via hole 4a that penetrates the base material layer 1 and electrically connects the first conductive layer 2 and the second conductive layer 3.

The configuration of the printed wiring board of FIG. 3 is the same as the configuration of the printed wiring board of FIG. 1 except for the shape of the via hole 4a. Therefore, with respect to the printed wiring board of FIG. 3, the same reference numerals are given to the components common to the printed wiring board of FIG. 1, and duplicate description will be omitted.

The via hole 4a is adjacent to at least the connection hole 5 among the through portion 10 laminated on the inner peripheral surface of the connection hole 5 and the surface of the first conductive layer 2 on the opposite side of the base material layer 1 of the first connection land 6. It has a first laminated portion 11a laminated in the region to be laminated, and a second laminated portion 12 laminated in a portion exposed inside the connection hole 5 of the second conductive layer 3.

The outer shape of the first laminated portion 11a of the via hole 4a in the present embodiment is a circular portion 13 concentric with the connection hole 5 and a plurality of expansion portions 14 in which the circular portion 13 is partially expanded outward. It has a deformed shape. That is, the circular portion 13 is composed of a plurality of arcs having the same concentricity and the same diameter, and the expansion portion 14 connects the plurality of arcs forming the circular portion 13 to form the radius of the first laminated portion 11a (distance from the center of gravity to the outer edge). ) Is partially increased. The expansion portions 14 in the present embodiment are each formed in a substantially semicircular shape so as to be easy to form.

The lower limit of the average diameter of the expansion portion 14 is preferably 0.1 times, more preferably 0.2 times, the average diameter of the circular portion 13. On the other hand, the upper limit of the average diameter of the expansion portion 14 is preferably 0.5 times, more preferably 0.4 times, the average diameter of the circular portion 13. When the average diameter of the expansion portion 14 is less than the above lower limit, the cross-sectional area of the expansion portion 14 becomes small, the effect of making the flow of the plating solution irregular becomes insufficient, and the air in the connection hole 5 is surely made. It may not be possible to expel it. On the contrary, when the average diameter of the expansion portion 14 exceeds the above upper limit, it is necessary to increase the area of the first connection land 6, which may hinder the high-density wiring of the first conductive layer 2.

The lower limit of the average distance between both ends of the expansion portion 14 is preferably 0.1 times, more preferably 0.2 times, the average diameter of the circular portion 13. On the other hand, the upper limit of the average distance between both ends of the expansion portion 14 is preferably 0.5 times, more preferably 0.4 times, the average diameter of the circular portion 13. When the average distance between both ends of the expansion portion 14 is less than the above lower limit, the cross-sectional area of the expansion portion 14 becomes small, the effect of making the flow of the plating solution irregular becomes insufficient, and the air in the connection hole 5 becomes insufficient. May not be able to be reliably expelled. On the contrary, when the average distance between both ends of the expansion portion 14 exceeds the above upper limit, the width of the expansion portion 14 becomes large and the difference in the flow velocity of the plating solution becomes small, so that the air in the connection hole 5 is surely removed. It may not be possible to expel it.

The number of the expansion portions 14 is preferably four or more so that the effect of expelling air from the connection hole 5 is unlikely to differ depending on the flow direction of the plating solution. Further, it is preferable that the expansion portions 14 are provided at equal intervals in the circumferential direction so that air can be efficiently expelled from the connection hole 5 regardless of the flow direction of the plating solution.

The printed wiring board has a deformed outer shape of the first laminated portion 11a laminated on the surface of the first connection land 6 of the via hole 4a, so that the first connection is made when the via hole 4a is formed by plating. A resist pattern having an opening having a shape corresponding to the outer shape of the first laminated portion 11a is laminated on the outer surface of the land 6 and is immersed in the plating solution.

Therefore, the flow of the plating solution around the connection hole 5 becomes irregular, and the plating solution flows irregularly into the connection hole 5, so that the balance of the interface between the air and the plating solution in the connection hole 5 is destroyed. Therefore, it is possible to prevent the air in the connection hole 5 from being left behind as dome-shaped bubbles, and to efficiently expel the air in the connection hole 5 by the plating solution. In particular, since the first laminated portion 11a has a circular portion 13 and a plurality of expansion portions 14 that partially expand the circular portion 13, it is possible to relatively easily and reliably make the flow of the plating solution non-uniform. can. As a result, in the printed wiring board, the through portion 10 and the first laminated portion 11a of the via hole 4a laminated in the connection hole 5 have a uniform thickness, so that the first conductive layer 2 and the second conductive layer 3 are formed. The electrical connection is secure.

[Third Embodiment]
FIG. 4 shows a printed wiring board according to an embodiment of the present invention. The printed wiring board is a flexible printed wiring board having flexibility.

The printed wiring board has an insulating base material layer 1, a first conductive layer 2 laminated on one side surface of the base material layer 1, and a first layer laminated on the other side surface of the base material layer 1. 2 The conductive layer 3 is provided with a via hole 4b that penetrates the base material layer 1 and electrically connects the first conductive layer 2 and the second conductive layer 3.

The configuration of the printed wiring board of FIG. 4 is the same as the configuration of the printed wiring board of FIG. 3, except for the shape of the via hole 4b. Therefore, with respect to the printed wiring board of FIG. 4, the same reference numerals are given to the components common to the printed wiring board of FIG. 3, and duplicate description will be omitted.

The via hole 4b is adjacent to at least the connection hole 5 among the through portion 10 laminated on the inner peripheral surface of the connection hole 5 and the surface of the first conductive layer 2 on the opposite side of the base material layer 1 of the first connection land 6. It has a first laminated portion 11b laminated in the region to be laminated, and a second laminated portion 12 laminated in a portion exposed inside the connection hole 5 of the second conductive layer 3.

The external shape of the first laminated portion 11b of the via hole 4b in the present embodiment is a circular portion 13 concentric with the connection hole 5 and one expansion portion 14 that partially extends the circular portion 13 outward. It has a deformed shape. That is, the first laminated portion 11b of the via hole 4b in FIG. 4 is obtained by reducing the number of the extended portions 14 of the first laminated portion 11a of the via hole 4a in FIG.

In this way, even when the first laminated portion 11b having only one expansion portion 14 is formed, the flow of the plating solution flowing into the opening of the resist pattern can be irregularly disturbed, and the connection hole 5 is not suitable. It is possible to regularly infiltrate the plating solution and expel the air in the connection hole 5. Therefore, also in the printed wiring board of the present embodiment, the electrical connection between the first conductive layer 2 and the second conductive layer 3 by the via hole 4b is reliable.

[Fourth Embodiment]
FIG. 5 shows a printed wiring board according to an embodiment of the present invention. The printed wiring board is a flexible printed wiring board having flexibility.

The printed wiring board has an insulating base material layer 1, a first conductive layer 2 laminated on one side surface of the base material layer 1, and a first layer laminated on the other side surface of the base material layer 1. 2 The conductive layer 3 is provided with a via hole 4c that penetrates the base material layer 1 and electrically connects the first conductive layer 2 and the second conductive layer 3.

The configuration of the printed wiring board of FIG. 5 is the same as the configuration of the printed wiring board of FIG. 3, except for the shape of the via hole 4c. Therefore, regarding the printed wiring board of FIG. 5, the same reference numerals are given to the components common to the printed wiring board of FIG. 3, and the duplicate description will be omitted.

The via hole 4c is adjacent to at least the connection hole 5 among the through portion 10 laminated on the inner peripheral surface of the connection hole 5 and the surface of the first conductive layer 2 on the opposite side of the base material layer 1 of the first connection land 6. It has a first laminated portion 11c laminated in the region to be laminated, and a second laminated portion 12 laminated in a portion exposed inside the connection hole 5 of the second conductive layer 3.

The external shape of the first laminated portion 11c of the via hole 4c in the present embodiment is a deformed shape having a connection hole 5 and four expansion portions 14c that partially extend concentric circular portions outward. The expansion portion 14c in the present embodiment is formed in a V shape that expands the circular portion 13 in a triangular shape.

Also in this embodiment, when the via hole 4c is formed, the plating solution can be irregularly infiltrated into the connection hole 5 to expel the air in the connection hole 5. Therefore, also in the printed wiring board of the present embodiment, the electrical connection between the first conductive layer 2 and the second conductive layer 3 by the via hole 4b is reliable.

As shown in the present embodiment, the shape of the expansion portion that makes the outer shape of the first laminated portion of the via hole in the present invention irregular is not particularly limited.

[Fifth Embodiment]
FIG. 6 shows a printed wiring board according to an embodiment of the present invention. The printed wiring board is a flexible printed wiring board having flexibility.

The printed wiring board has an insulating base material layer 1, a first conductive layer 2 laminated on one side surface of the base material layer 1, and a first layer laminated on the other side surface of the base material layer 1. 2 The conductive layer 3 is provided with a via hole 4d that penetrates the base material layer 1 and electrically connects the first conductive layer 2 and the second conductive layer 3.

The configuration of the printed wiring board of FIG. 6 is the same as the configuration of the printed wiring board of FIG. 3, except for the shape of the via hole 4d. Therefore, with respect to the printed wiring board of FIG. 6, the components common to the printed wiring board of FIG. 3 are designated by the same reference numerals, and duplicate description will be omitted.

The via hole 4d is adjacent to at least the connection hole 5 among the through portion 10 laminated on the inner peripheral surface of the connection hole 5 and the surface of the first conductive layer 2 on the opposite side of the base material layer 1 of the first connection land 6. It has a first laminated portion 11d laminated in the region to be laminated, and a second laminated portion 12 laminated in a portion exposed inside the connection hole 5 of the second conductive layer 3.

The external shape of the first laminated portion 11d of the via hole 4d in the present embodiment has a large number of expansion portions 14d that partially extend the virtual circle concentric with the connection hole 5 outward, and the adjacent expansion portions 14d. The shape is such that the spaces are smoothly connected by an arc.

Also in this embodiment, when the via hole 4d is formed, the plating solution can be irregularly infiltrated into the connection hole 5 to expel the air in the connection hole 5. Therefore, also in the printed wiring board of the present embodiment, the electrical connection between the first conductive layer 2 and the second conductive layer 3 by the via hole 4b is reliable.

[Other embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.

In the printed wiring board, when the outer shape of the first laminated portion of the via hole has an expansion portion, this expansion portion partially expands a part of a deformed shape such as a regular polygon to the outside to further roundness. (Difference between the radius of the inscribed circle and the radius of the circumscribed circle) may be increased.

In the printed wiring board, the first conductive layer and the second conductive layer are relative to each other, and even if the conductive layer to be the first conductive layer in one via hole is used as the second conductive layer in another via hole. good.

The printed wiring board may be a multilayer wiring board on which a further base material layer and a conductive layer are laminated. Further, the printed wiring board may include other layers such as a coverlay, a solder resist, and a shield film.

The via hole in the printed wiring board may be a through hole that penetrates all the conductive layers, or may be an interstitial via hole that connects the conductive layers inside the multilayer wiring board.

The printed wiring board according to one aspect of the present invention can be particularly preferably used as a flexible printed wiring board used in a small portable electronic device or the like.

1 Base material layer 2 First conductive layer 3 Second conductive layer 4, 4a, 4b, 4c, 4d Via hole 5 Connection hole 6 First connection land 7 First wiring pattern 8 Second connection land 9 Second wiring pattern 10 Penetration portions 11, 11a, 11b, 11c, 11d First laminated portion 12 Second laminated portion 13 Circular portion 14, 14c, 14d Expansion portion

Claims (6)

A base material layer that has insulating properties and has connection holes that penetrate in the thickness direction .
A first conductive layer having a connecting land laminated on one surface of the base material layer and formed in an annular shape at a position overlapping the connection hole in a plan view .
A second conductive layer laminated on the other surface of the base material layer and arranged so as to seal the connection hole ,
Formed by plating, it is continuously laminated on the inner peripheral surface of the connection hole, the surface of the connection land opposite to the base material layer, and the surface of the second conductive layer, and the first conductive layer and the first conductive layer. It is equipped with a via hole that electrically connects the second conductive layer.
A printed wiring board in which the outer shape of the first laminated portion laminated on the surface of the connecting land of the via hole is different from the circular shape in a plan view .
The printed wiring board according to claim 1, wherein the outer shape of the first laminated portion has an extended portion that is partially extended outward. The printed wiring board according to claim 2, wherein the planar shape of the expansion portion is an arc shape. The printed wiring board according to claim 2 or 3, wherein a plurality of the expansion portions are formed at intervals in the circumferential direction. The printed wiring board according to claim 1, wherein the outer shape of the first laminated portion is a polygonal shape. A base material layer that has insulating properties and has connection holes that penetrate in the thickness direction .
A first conductive layer having a connecting land laminated on one surface of the base material layer and formed in an annular shape at a position overlapping the connection hole in a plan view .
A second conductive layer laminated on the other surface of the base material layer and arranged so as to seal the connection hole ,
It is formed by plating and is continuously laminated on the inner peripheral surface of the connection hole, the surface of the connection land opposite to the base material layer, and the surface of the second conductive layer, and the first conductive layer and the first conductive layer. A method for manufacturing a printed wiring board including a via hole for electrically connecting the second conductive layers.
The process of forming the first conductive layer and the connection hole, and
A step of forming a resist pattern having an opening having a shape different from a circle in a plan view, which covers the first conductive layer and exposes at least a portion of the first conductive layer adjacent to the connection hole.
A method for manufacturing a printed wiring board, comprising a step of introducing a plating solution from an opening of the resist pattern into the connection hole.

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