JP7459492B2 - wiring board - Google Patents

Description

This disclosure relates to a wiring board.

The mainstream method for mounting electronic components is to surface-mount the electronic components on a wiring board (see, for example, Patent Documents 1 to 3).

BACKGROUND ART In recent years, as electronic devices have become smaller and more sophisticated, technological developments have been progressing to increase multilayering, higher density, and higher speed for wiring boards on which electronic components are mounted. Therefore, in wiring boards, there is a demand for narrower pitches in which the spacing (pitch) between connecting portions is narrower. Note that the connection portion is also referred to as a pad or a terminal portion.

Japanese Patent Application Publication No. 2018-22894 JP 2017-63226 A JP 2017-220659 A

However, if the pitch of the connecting portions is narrow, there is a problem in that adjacent connecting portions are electrically connected by solder.

The present disclosure is an invention made in consideration of the above problems, and its main objective is to provide a wiring board that can suppress electrical continuity between adjacent connections.

In narrow-pitch wiring boards, a known cause of short circuits due to solder is, for example, solder on adjacent connections coming into contact, known as a solder bridge. However, short circuits may occur even if a solder bridge does not occur. The inventors of the present disclosure have conducted intensive research to solve the above problem and have found that when mounting electronic components on a wiring board using solder, the solder or flux penetrates into the interface between the connection and the insulating layer, causing electrical continuity between adjacent connections. They have also found that by controlling the shape of the opening in the insulating layer of the wiring board and the shape of the wiring, it is possible to control the direction in which the solder or flux penetrates into the interface between the connection and the insulating layer, thereby preventing electrical continuity between adjacent connections. The present disclosure has been completed based on the above findings.

That is, the present disclosure provides a base material having a first surface and a second surface opposite to the first surface, one or more layers of wiring and one or more layers of insulation disposed on the first surface side of the base material. a wiring board, wherein the one or more layers of wiring have at least an outermost wiring located farthest from the base material, and the one or more insulating layers have at least one outermost wiring located farthest from the base material; at least an outermost insulating layer disposed on the side opposite to the base material side and having an opening located on the outermost wiring, and the wiring board is arranged in the opening of the outermost insulating layer. The opening of the outermost insulating layer is arranged from a surface of the outermost insulating layer opposite to the surface of the outermost wiring, the opening of the outermost insulating layer being electrically connected to the outermost wiring. The connecting portion has a tapered shape in which the horizontal cross-sectional area becomes smaller toward the outermost wiring side surface, and the inclination angle of the side surface of the opening of the outermost insulating layer is 10 degrees or more and 70 degrees or less, and the connecting portion Provided is a wiring board having a pitch of 50 μm or less.

According to the present disclosure, the opening of the outermost insulating layer has the above-mentioned tapered shape, and the inclination angle of the side of the opening of the outermost insulating layer is within a predetermined range. Therefore, even if solder or flux penetrates into the interface between the connection portion and the outermost insulating layer when mounting an electronic component on the wiring board of the present disclosure using solder, the direction in which the solder or flux penetrates can be controlled, and it is possible to prevent adjacent connection portions from becoming conductive. Therefore, even with a narrow pitch, short circuits can be prevented.

In the present disclosure, it is preferable that the outermost wiring has a concave shape in which a surface on the connection portion side within the opening of the outermost insulating layer is depressed. By having the outermost wiring having the above-mentioned concave shape, it is possible to further suppress conduction between adjacent connecting portions when electronic components are mounted on the wiring board of the present disclosure using solder.

The present disclosure also provides a wiring board having a substrate having a first surface and a second surface opposite to the first surface, and one or more layers of wiring and one or more insulating layers arranged on the first surface side of the substrate, wherein the one or more layers of wiring have at least an outermost wiring located farthest from the substrate, the one or more insulating layers have at least an outermost insulating layer arranged on a surface side opposite the substrate side of the outermost wiring and having an opening located on the outermost wiring, the wiring board further has a connection portion arranged in the opening of the outermost insulating layer and electrically connected to the outermost wiring, the outermost wiring has a concave shape with a surface on the connection portion side within the opening of the outermost insulating layer being concave, and the pitch of the connection portion is 50 μm or less.

According to the present disclosure, since the outermost wiring has the above-mentioned concave shape, when electronic components are mounted on the wiring board of the present disclosure using solder, the solder or flux is applied to the interface between the connection portion and the outermost insulating layer. Even if the solder or flux enters, the direction in which the solder or flux enters can be controlled, and it is possible to suppress conduction between adjacent connection parts. Therefore, even if the pitch is narrow, short circuits can be suppressed.

In the present disclosure, it is preferable that the height of the connection portion protruding from the surface of the outermost insulating layer opposite the surface on the outermost wiring side is 3 μm or less. This disclosure is useful when the height of the connection portion is within the above range.

In the present disclosure, it is preferable that the outermost insulating layer contains a cured product of a photosensitive resin composition. This is because the outermost insulating layer having an opening in a desired shape can be easily formed using the photolithography method.

The present disclosure has the effect of suppressing electrical continuity between adjacent connections.

1 is a schematic cross-sectional view illustrating a wiring board according to the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board of the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board according to the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board of the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board according to the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board according to the present disclosure. 1 is a schematic cross-sectional view illustrating a wiring board of the present disclosure.

Below, an embodiment of the present disclosure will be described with reference to the drawings. However, the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the description of the embodiment exemplified below. In addition, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each figure, elements similar to those described above with respect to the previous figures are given the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when describing a mode in which another component is placed on a certain component, the term "above" or "below" is used, unless otherwise specified, to include both cases in which another component is placed directly above or below a certain component so as to be in contact with the component, and cases in which another component is placed above or below a certain component with another component interposed between them. In addition, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the term "on the surface side" or "on the surface" is used, unless otherwise specified, to include both cases in which another component is placed directly above or below a certain component so as to be in contact with the component, and cases in which another component is placed above or below a certain component with another component interposed between them.

Hereinafter, the wiring board of the present disclosure will be described in detail. The wiring board of the present disclosure has two embodiments. Each embodiment will be described below.

I. First embodiment A first embodiment of the wiring board of the present disclosure is a wiring board having a substrate having a first surface and a second surface opposite to the first surface, and one or more layers of wiring and one or more insulating layers arranged on the first surface side of the substrate, wherein the one or more layers of wiring have at least an outermost wiring located farthest from the substrate, the one or more insulating layers are arranged on the surface side opposite to the substrate side of the outermost wiring, and have at least an outermost insulating layer having an opening located on the outermost wiring, the wiring board further has a connection portion arranged in the opening of the outermost insulating layer and electrically connected to the outermost wiring, the opening of the outermost insulating layer has a tapered shape in which the area of the horizontal cross section decreases from the surface opposite to the surface of the outermost wiring side of the outermost insulating layer toward the surface of the outermost wiring side, the inclination angle of the side of the opening of the outermost insulating layer is 10 degrees or more and 70 degrees or less, and the pitch of the connection portion is 50 μm or less.

The wiring board of this embodiment will be explained using the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of a wiring board according to this embodiment. As shown in FIG. 1, the wiring board 1 of this embodiment includes a base material 2 having a first surface 2a and a second surface 2b opposite to the first surface 2a, and a base material 1 disposed on the first surface 2a side. It has one or more layers of wiring 3a, 3b and one or more layers of insulating layers 4a, 4b. The one or more layers of wiring 3a, 3b have at least the outermost wiring 13 (3b) located farthest from the base material 2, and the one or more insulating layers 4a, 4b have the outermost wiring 13 (3b) located farthest from the base material 2. It has at least an outermost insulating layer 14 (4b) which is disposed on the surface opposite to the surface on the base material 2 side and has an opening 5b located on the outermost wiring 13 (3b), and the wiring board 1 further includes a connecting portion 8 arranged in the opening 5b of the outermost insulating layer 14 (4b) and electrically connected to the outermost wiring 13 (3b). The opening 5b of the outermost insulating layer 14 (4b) extends from the surface of the outermost insulating layer 14 (4b) opposite to the surface of the outermost wiring 13 (3b) to the surface of the outermost wiring 13 (3b). It has a tapered shape in which the area of the horizontal cross section becomes smaller toward the outermost insulating layer 14 (4b), and as shown in FIG. There is. Furthermore, the pitch P of the connecting portions 8 is within a predetermined range. Note that FIG. 2 is an enlarged view of FIG. 1.

The wiring board of this embodiment only needs to have one or more layers of wiring and one or more insulating layers arranged on the first surface side of the base material, and although not shown, one layer of wiring and one layer of As shown in FIG. 1, it may have two layers of wiring 3a, 3b and two layers of insulating layer 4a, 4b.Although not shown, it may have three or more layers. It may have wiring and three or more insulating layers.

The insulating layer has an opening for placing wiring or a connection part. When the wiring board of this embodiment has two or more insulating layers, each of the two or more insulating layers has an opening, but it is sufficient that the opening of the outermost insulating layer has the above-mentioned tapered shape, and the openings of the insulating layers other than the outermost insulating layer may or may not have the above-mentioned tapered shape. For example, in FIG. 1, the two insulating layers 4a and 4b have openings 5a and 5b, respectively, but the opening 5b of the outermost insulating layer 14 (4b) has the above-mentioned tapered shape, while the opening 5a of the insulating layer 4a other than the outermost insulating layer 14 (4b) does not have the above-mentioned tapered shape.

Further, the inclination angle of the side surface of the opening in the outermost insulating layer may be within a predetermined range, and the inclination angle of the opening in the insulating layer other than the outermost insulating layer is not particularly limited. For example, in FIG. 1, the inclination angle of the opening 5b of the outermost insulating layer 14 (4b) is within a predetermined range, whereas the inclination angle of the opening 5a of the insulating layer 4a other than the outermost insulating layer 14 (4b) is is not within a predetermined range.

In this embodiment, as shown in FIG. 1, the connection portion 8 may have a first connection layer 6 disposed in the opening 5b of the outermost insulating layer 14 (4b) and a second connection layer 7 disposed on the first connection layer 6.

According to this embodiment, the opening in the outermost insulating layer has a tapered shape in which the area of the horizontal cross section decreases from the surface opposite the surface on the outermost wiring side of the outermost insulating layer toward the surface on the outermost wiring side, and the inclination angle of the side of the opening in the outermost insulating layer is within a predetermined range, so that when mounting electronic components on the wiring board of this embodiment using solder, it is possible to prevent adjacent connections from becoming conductive due to solder or flux. The reason for this is unclear, but is presumed to be as follows.

That is, for example, as shown in FIG. 2, when an electronic component is mounted on the wiring board of this embodiment using solder, when the solder or flux penetrates the interface between the connection part 8 and the outermost insulating layer 14 and reaches the surface of the outermost wiring 13 (arrow a in FIG. 2), it is divided into two cases: when it penetrates the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 2) and when it penetrates the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 2). At this time, if the opening 5b of the outermost insulating layer 14 has the above-mentioned tapered shape and the inclination angle θ of the side of the opening 5b of the outermost insulating layer 14 is within a predetermined range, it is presumed that the solder or flux will easily penetrate the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 2) and will not easily penetrate the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 2). If solder or flux penetrates the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 2), it will cause electrical conduction with the adjacent connection parts. On the other hand, even if solder or flux penetrates the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 2), it is presumed that electrical conduction with the adjacent connection parts can be suppressed because there is a distance to the adjacent connection parts. Thus, in this embodiment, the opening of the outermost insulating layer has the above-mentioned tapered shape, and the inclination angle of the side of the opening of the outermost insulating layer is within a predetermined range, so that even if solder or flux penetrates into the interface between the connection part and the outermost insulating layer when mounting an electronic component on the wiring board of this embodiment using solder, it is considered that the direction in which the solder or flux penetrates can be controlled. Therefore, it is possible to suppress electrical conduction between adjacent connection parts. Therefore, even with a narrow pitch, electrical connection can be made without causing a short circuit.

Conventionally, lasers have been used primarily to form openings in the outermost insulating layer of wiring boards for locating connection parts. Lasers have excellent directivity (linearity), so when openings are formed in the outermost insulating layer with a laser, the opening in the outermost insulating layer does not have a tapered shape, and the inclination angle of the side of the opening in the outermost insulating layer is 90 degrees. Therefore, in this case, when mounting electronic components on a wiring board using solder, if solder or flux seeps into the interface between the connection part and the outermost insulating layer, the direction in which the solder or flux seeps in cannot be controlled, and adjacent connection parts will become conductive.

Hereinafter, each configuration of the wiring board of this embodiment will be explained.

1. Insulating Layer The insulating layer in this embodiment is a member that is disposed on the first surface side of the base material and has insulation properties. The wiring board of this embodiment has one or more insulating layers.

The insulating layer may be one or more layers, and may be one layer or two or more layers.

The one or more insulating layers include at least an outermost insulating layer that is disposed on the surface opposite to the base material side surface of the outermost wiring, which will be described later, and has an opening located on the outermost wiring.

The opening in the outermost insulating layer has a tapered shape in which the area of the horizontal cross section decreases from the surface opposite the surface of the outermost insulating layer facing the outermost wiring toward the surface facing the outermost wiring.

When the wiring board of this embodiment has two or more insulating layers, it is sufficient that the opening of the outermost insulating layer has the above-mentioned tapered shape, and the openings of insulating layers other than the outermost insulating layer may or may not have the above-mentioned tapered shape.

The inclination angle of the side of the opening in the outermost insulating layer is 10 degrees or more, preferably 12 degrees or more, and particularly preferably 15 degrees or more. The inclination angle is 70 degrees or less, and particularly preferably 60 degrees or less. By having the inclination angle within the above range, when mounting electronic components on the wiring board of this embodiment using solder, the direction in which the solder or flux penetrates can be controlled, and electrical continuity between adjacent connections can be suppressed.

Here, the "inclination angle of the side of the opening in the outermost insulating layer" refers to the smaller angle between the side of the opening in the outermost insulating layer and the surface on the connection side of the outermost wiring. For example, in Figure 2, it refers to the angle indicated by θ.

When the side of the opening of the outermost insulating layer is curved rather than flat, the "tilt angle of the side of the opening of the outermost insulating layer" refers to the smaller angle θ between the tangent 5 at the contact point between the center line of the thickness d of the outermost insulating layer 14 located on the outermost wiring 13 in the opening 5b of the outermost insulating layer 14 and the side of the opening 5b of the outermost insulating layer 14, and the surface of the outermost wiring 13 on the connection part 8 side, as shown in FIG. 3, for example.

The inclination angle of the side surface of the opening in the outermost insulating layer can be measured, for example, by observing a vertical cross section using a scanning electron microscope (SEM).

When the wiring board of this embodiment has two or more insulating layers, the inclination angle of the side of the opening of the outermost insulating layer may be within a predetermined range, and the inclination angle of the side of the opening of insulating layers other than the outermost insulating layer is not particularly limited.

The material for the insulating layer is not particularly limited as long as it is an insulating material, and insulating materials that are generally used for insulating layers of wiring boards can be used, and both organic and inorganic materials can be used.

Further, the material of the outermost insulating layer is not particularly limited as long as it is an insulating material capable of forming the above-mentioned tapered opening. Among these, the material of the outermost insulating layer is preferably a photosensitive resin. That is, the outermost insulating layer preferably contains a cured product of a photosensitive resin composition. This is because the opening having the tapered shape can be easily formed using the photolithography method.

The thickness of the insulating layer can be set to the thickness of an insulating layer in a general wiring board.

As the method for forming the insulating layer, a general method for forming an insulating layer can be used, and is appropriately selected depending on the material of the insulating layer and the like. Further, as a method for forming an opening in the insulating layer, a general method for forming an opening can be used, and is appropriately selected depending on the material of the insulating layer and the like. Examples of methods for forming the opening include laser irradiation, etching such as plasma etching and wet etching, mechanical processing methods such as sandblasting and ultrasonic drilling, and photolithography. Among these, the method for forming the outermost insulating layer is preferably a photolithography method. This is because the opening having the tapered shape can be easily formed using the photolithography method.

2. Wiring The wiring in this embodiment is a conductive member that is disposed on the first surface side of the base material. The wiring board in this embodiment has one or more layers of wiring.

The wiring may have one or more layers, may be one layer, or may have two or more layers.

The one or more layers of wiring have at least an outermost wiring located farthest from the base material.

As shown in FIG. 4, for example, the outermost wiring 13 preferably has a concave shape in which the surface on the connection portion 8 side within the opening 5b of the outermost insulating layer 14 (4b) is depressed. By having the outermost wiring having the above-mentioned concave shape, when electronic components are mounted on the wiring board of this embodiment using solder, it is possible to further suppress conduction between adjacent connection parts due to solder or flux. . Although the reason for this is not clear, it is inferred as follows.

That is, as described above, for example, as shown in FIG. 5, when an electronic component is mounted on the wiring board of this embodiment using solder, the solder or flux penetrates into the interface between the connection part 8 and the outermost insulating layer 14 and reaches the surface of the outermost wiring 13 (arrow a in FIG. 5), and then it is divided into two cases: when it penetrates into the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 5) and when it penetrates into the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 5). At this time, if the outermost wiring 13 has the above-mentioned concave shape, it is presumed that the solder or flux is more likely to penetrate into the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 5), and is less likely to penetrate into the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 5). In this way, it is considered that by having the outermost wiring have the above-mentioned concave shape, even if the solder or flux penetrates into the interface between the connection part and the outermost insulating layer when an electronic component is mounted on the wiring board of this embodiment using solder, the direction in which the solder or flux penetrates can be controlled. This makes it possible to prevent adjacent connection parts from becoming conductive. Therefore, even with a narrow pitch, electrical connections can be made without causing short circuits.

The cross-sectional shape of the concave recess may be, for example, a semi-ellipse.

The depth of the concave recess is not particularly limited as long as it is deep enough to obtain the above-mentioned effect, but can be, for example, 0.5 μm to 2.0 μm, and preferably 0.5 μm to 1.5 μm. The depth of the concave recess refers to the maximum depth of the concave recess. By having the depth of the concave recess within the above range, it is possible to control the direction in which solder or flux enters when mounting electronic components on the wiring board of this embodiment using solder, and to prevent adjacent connections from becoming conductive.

Note that the depth of the concave recess can be measured by observation using a scanning electron microscope (SEM) or the like.

In addition, the depth of the above-mentioned concave shape can be calculated using a stylus method, which calculates the thickness by tracing the surface with a stylus against the surface of the connection part inside the opening of the outermost insulating layer and detecting the unevenness. It can also be measured by a method. Specifically, it can be measured using a stylus-type film thickness meter P-15 manufactured by KLA-Tencor Co., Ltd. under conditions of a stylus pressure of 5 mg and a scanning speed of 50 μm/sec. Note that an average value of measurement results at multiple locations may be used.

When the wiring board of this embodiment has two or more layers of wiring, it is sufficient that the outermost wiring has the above-mentioned concave shape, and wiring other than the outermost wiring may or may not have the above-mentioned concave shape.

The material for the wiring is not particularly limited as long as it is conductive, and any conductive material used for general wiring can be used. Examples of the conductive material include metals such as copper, molybdenum, titanium, tungsten, tantalum, aluminum, gold, silver, nickel, and palladium, alloys containing at least one selected from these metals, or indium tin oxide ( Conductive oxides such as ITO) and indium zinc oxide (IZO) can be used. By using highly conductive copper or aluminum, it is possible to suppress an increase in resistance. Furthermore, by using copper, which has relatively low hardness, it is possible to provide a wiring board on which more reliable electrical connections can be established.

The wiring may be single-layered or multi-layered with multiple layers stacked on top of each other.

The thickness of the wiring can be the same as that of a typical wiring board. The thickness of the wiring can be, for example, 0.05 μm or more and 20 μm or less, or 0.1 μm or more and 15 μm or less, or 0.2 μm or more and 10 μm or less. This allows sufficient conductivity to be obtained.

The wiring can be formed using any common wiring formation method, such as CVD, sputtering, plating, etc.

Further, as a method for forming the recessed shape in the outermost wiring, for example, etching or the like can be used. When etching is performed when forming a connection portion, which will be described later, the above-mentioned concave shape can be formed in the outermost wiring during the etching.

3. Connection Portion The connection portion in this embodiment is a member that is disposed in the opening of the outermost insulating layer and electrically connected to the outermost wiring.

The pitch of the connecting portions is 50 μm or less, can be 10 μm or more and 50 μm or less, and is preferably 15 μm or more and 45 μm or less. In this embodiment, the pitch of the connecting portions is within the above range, and even if the pitch is narrow, electrical connection can be made without causing a short circuit.

Here, the pitch can be measured, for example, by observation using an optical microscope or observation using a scanning electron microscope (SEM).

The material of the connection part is not particularly limited as long as it is a conductive material, and can be the same as the material of the wiring described above.

The connection portion may be a single layer, or may be a multilayer structure in which a plurality of layers are laminated.

The thickness of the connection part is not particularly limited, and is appropriately set depending on the shape of the terminal part of the electronic component mounted on the wiring board of this embodiment. can do.

The connection portion 8 may protrude from the surface of the outermost insulating layer 14 opposite the surface on the outermost wiring 13 side, as shown in, for example, Figures 1 and 2. In this case, the height of the connection portion protruding from the surface of the outermost insulating layer opposite the surface on the outermost wiring side is preferably 3 μm or less. For example, in the CVD method, sputtering method, plating method, etc., film growth is usually isotropic. Therefore, for example, as shown in Figure 2, the height H1 of the connection portion 8 protruding from the surface opposite the surface on the outermost wiring 13 side of the outermost insulating layer 14 is approximately the same as the length H2 of the portion where the connection portion 8 and the outermost insulating layer 14 overlap on the surface opposite the surface on the outermost wiring 13 side of the outermost insulating layer 14. If the length H2 of the overlapping portion of the connection portion 8 and the outermost insulating layer 14 on the surface of the outermost insulating layer 14 opposite the surface on the outermost wiring 13 side is 3 μm or less, it is believed that when electronic components are mounted on the wiring board of this embodiment using solder, solder or flux will easily penetrate into the interface between the connection portion 8 and the outermost insulating layer 14. Therefore, it is preferable that the height of the connection portion protruding from the surface of the outermost insulating layer opposite the surface on the outermost wiring side is 3 μm or less.

The method for forming the connection portion can be the same as the method for forming the wiring described above.

4. Substrate The substrate in this embodiment has a first surface and a second surface opposite to the first surface, and is a member that supports the insulating layer, wiring, and connection portion.

The base material is not particularly limited as long as it has insulating properties, and insulating base materials commonly used for wiring boards can be used. Examples include glass substrates, glass epoxy substrates, glass composite substrates, ceramic substrates such as alumina substrates, resin substrates such as fluororesin substrates and polyimide substrates, and paper phenol substrates.

As described below, when the wiring board of this embodiment has a second wiring that electrically connects the first surface and the second surface of the substrate, the substrate may or may not have a through hole. When the substrate has a through hole, the second wiring becomes a through wiring arranged in the through hole.

The diameter of the through hole can be appropriately selected depending on the application of the wiring board and is not particularly limited, but may be, for example, 10 μm or more and 200 μm or less, or 20 μm or more and 100 μm or less.

Examples of methods for forming the through holes include etching such as plasma etching and wet etching, laser irradiation, and mechanical processing methods such as sandblasting and ultrasonic drilling.

The thickness of the substrate is not particularly limited as long as it can support the insulating layer, wiring, and connection parts, and can be appropriately selected depending on the application of the wiring board. The thickness of the substrate can be, for example, 10 μm or more and 800 μm or less, or 100 μm or more and 600 μm or less, or 300 μm or more and 400 μm or less.

II. Second Embodiment A second embodiment of the wiring board of the present disclosure includes a base material having a first surface and a second surface opposite to the first surface, and a first surface disposed on the first surface side of the base material. A wiring board having one or more layers of wiring and one or more insulating layers, wherein the one or more layers of wiring has at least an outermost wiring located farthest from the base material, an insulating layer is disposed on the side of the outermost wiring opposite to the surface on the base material side, and has at least an outermost insulating layer having an opening located on the outermost wiring, and the wiring board , further comprising a connection part disposed in the opening of the outermost insulating layer and electrically connected to the outermost wiring, wherein the outermost wiring is on the side of the connection part in the opening of the outermost insulating layer. The wiring board has a recessed surface, and the pitch of the connecting portions is 50 μm or less.

FIG. 6 is a schematic cross-sectional view showing an example of the wiring board of this embodiment. As shown in FIG. 6, the wiring board 1 of this embodiment includes a base material 2 having a first surface 2a and a second surface 2b opposite to the first surface 2a, and a base material 1 disposed on the first surface 2a side. It has one or more layers of wiring 3a, 3b and one or more layers of insulating layers 4a, 4b. The one or more layers of wiring 3a, 3b have at least the outermost wiring 13 (3b) located farthest from the base material 2, and the one or more insulating layers 4a, 4b have the outermost wiring 13 (3b) located farthest from the base material 2. It has at least an outermost insulating layer 14 (4b) which is disposed on the surface opposite to the surface on the base material 2 side and has an opening 5b located on the outermost wiring 13 (3b), and the wiring board 1 further includes a connecting portion 8 arranged in the opening 5b of the outermost insulating layer 14 (4b) and electrically connected to the outermost wiring 13 (3b). The outermost wiring 13 (3b) has a concave shape in which the surface on the connection portion 8 side within the opening 5b of the outermost insulating layer 14 (4b) is depressed. Furthermore, the pitch P of the connecting portions 8 is within a predetermined range.

The wiring board of this embodiment only needs to have one or more layers of wiring and one or more insulating layers arranged on the first surface side of the base material, and although not shown, one layer of wiring and one layer of As shown in FIG. 6, it may have two layers of wiring 3a, 3b and two layers of insulating layer 4a, 4b. Although not shown, it may have three or more layers. It may have wiring and three or more insulating layers.

When the wiring board of this embodiment has two or more layers of wiring, it is sufficient that the outermost wiring has the above-mentioned concave shape, and the wiring other than the outermost wiring may have the above-mentioned concave shape. You don't have to. For example, in FIG. 6, the outermost wiring 13 (3b) has the above-mentioned concave shape, whereas the wiring 3a other than the outermost wiring 13 (3b) does not have the above-mentioned concave shape.

In this embodiment, as shown in FIG. 6, the connection portion 8 may have a first connection layer 6 arranged in the opening 5b of the outermost insulating layer 14 (4b) and a second connection layer 7 arranged on the first connection layer 6.

According to this embodiment, the outermost wiring has a concave shape in which the surface on the upper connection part side inside the opening of the outermost insulating layer is concave, so that electronic components can be attached to the wiring board of this embodiment using solder. When mounting, it is possible to suppress conduction between adjacent connection parts due to solder or flux. Although the reason for this is not clear, it is inferred as follows.

That is, for example, as shown in FIG. 7, when an electronic component is mounted on the wiring board of this embodiment using solder, when the solder or flux penetrates into the interface between the connection part 8 and the outermost insulating layer 14 and reaches the surface of the outermost wiring 13 (arrow a in FIG. 7), it is divided into two cases: when it penetrates into the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 7) and when it penetrates into the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 7). At this time, if the outermost wiring 13 has the above-mentioned concave shape, it is presumed that the solder or flux is more likely to penetrate into the interface between the connection part 8 and the outermost wiring 13 (arrow b in FIG. 7) and is less likely to penetrate into the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 7). When the solder or flux penetrates into the interface between the outermost insulating layer 14 and the outermost wiring 13 (arrow c in FIG. 7), it becomes a cause of conduction with the adjacent connection part. On the other hand, even if solder or flux penetrates into the interface between the connection 8 and the outermost wiring 13 (arrow b in FIG. 7), it is presumed that since there is a distance to the adjacent connection, it is possible to prevent electrical continuity between the adjacent connection. In this embodiment, since the outermost wiring has the above-mentioned concave shape, it is believed that even if solder or flux penetrates into the interface between the connection and the outermost insulating layer when mounting an electronic component on the wiring board of this embodiment using solder, the direction in which the solder or flux penetrates can be controlled. Therefore, it is possible to prevent electrical continuity between adjacent connection parts. Therefore, even with a narrow pitch, electrical connection can be made without causing a short circuit.

Hereinafter, each configuration of the wiring board of this embodiment will be explained.

1. Insulating Layer The insulating layer in this embodiment is a member that is disposed on the first surface side of the base material and has insulation properties. The wiring board of this embodiment has one or more insulating layers.

The insulating layer may be one or more layers, may be one layer, or may be two or more layers.

The one or more insulating layers include at least an outermost insulating layer that is disposed on the surface opposite to the base material side surface of the outermost wiring, which will be described later, and has an opening located on the outermost wiring.

The material, thickness, formation method, etc. of the insulating layer can be the same as that of the insulating layer in the first embodiment described above.

2. Wiring The wiring in this embodiment is a member that is arranged on the first surface side of the base material and has conductivity. The wiring board of this embodiment has one or more layers of wiring.

The wiring may be one or more layers, and may be one layer or two or more layers.

The one or more layers of wiring have at least an outermost wiring located farthest from the base material.

The outermost wiring has a concave shape on the surface facing the connection part within the opening in the outermost insulating layer.

The cross-sectional shape, depth, etc. of the concave recess can be the same as that of the outermost wiring in the first embodiment.

When the wiring board of this embodiment has two or more layers of wiring, it is sufficient that the outermost wiring has the above-mentioned concave shape, and the wiring other than the outermost wiring may have the above-mentioned concave shape, It is not necessary to have one.

The wiring may be single-layered or multi-layered with multiple layers stacked on top of each other.

The material, thickness, and forming method of the wiring can be the same as that of the wiring in the first embodiment described above.

3. Connection Portion The connection portion in this embodiment is a member that is disposed in the opening of the outermost insulating layer and is electrically connected to the outermost wiring.
The connection portion may be the same as the connection portion in the first embodiment.

4. Base Material The base material in this embodiment has a first surface and a second surface opposite to the first surface, and is a member that supports the above-mentioned insulating layer, wiring, and connection portion.
The base material may be the same as the base material of the first embodiment.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

The following examples and comparative examples will explain this disclosure in more detail.

[Example 1]
(Formation of wiring and insulating layer)
A glass substrate (AN100, 300 mm x 400 mm, manufactured by AGC) was irradiated with ultraviolet light and washed. Then, the glass substrate was subjected to chromium sputtering and copper sputtering, and a resist pattern was formed thereon using a dry film resist (Sunfort AQ4038, manufactured by Asahi Kasei Electronics). Next, copper sulfate electrolytic plating (Top Lucina SF, manufactured by Okuno Pharmaceutical Co., Ltd.) was performed on the openings of the resist pattern to form a wiring layer with a thickness of 3 μm. Next, the dry film resist was peeled off with a sodium hydroxide solution at 50°C, and the exposed chromium layer and copper layer were removed with a chromium etching solution (Esclean S-24, manufactured by Sasaki Chemical Industry Co., Ltd.) and a copper etching solution (AD-331, manufactured by Meltec Co., Ltd.), respectively. This formed the wiring. Then, a photosensitive resist (Photoneece PW-1000, manufactured by Toray Industries, Inc.) was used to form an insulating layer with a thickness of 3 μm and an opening pitch of 45 μm so as to cover the wiring.

(Formation of connection part)
Next, electroless nickel plating was performed on the opening of the insulating layer to form a connection part. First, the surface of the wiring exposed in the opening of the insulating layer was degreased using an acid cleaner (ICP Clean S-135K, manufactured by Okuno Chemical Industries Co., Ltd.). Next, soft etching was performed by immersing for 5 seconds in a copper etching solution (AD-331, manufactured by Meltec Co., Ltd.) kept at 25 ° C. Next, Pd was applied to the surface of the wiring using an activator (ICP Accela, manufactured by Okuno Chemical Industries Co., Ltd.), and electroless nickel plating (ICP Nicoron GM-SE, manufactured by Okuno Chemical Industries Co., Ltd.) was performed to form a nickel-plated part. Then, electroless gold plating (Flash Gold NC, manufactured by Okuno Chemical Industries Co., Ltd.) was performed on the surface of the nickel-plated part to form a protective plating part with a thickness of 0.05 μm. This resulted in a wiring board having a connection part. The pitch of the connection part was 45 μm.

The vertical cross-section of the resulting wiring board was observed using a scanning electron microscope (SEM) to measure the inclination angle of the side of the opening in the insulating layer. The results are shown in Table 1.

[Examples 2 to 3 and Comparative Examples 1 to 2]
A wiring board was produced in the same manner as in Example 1, except that the insulating layer was formed so that the inclination angle of the side surface of the opening in the insulating layer was the angle shown in Table 1.

[Evaluation 1]
In the wiring boards of Examples 1 to 3 and Comparative Examples 1 to 2, solder paste was applied to adjacent unconnected connection parts, and after holding at 150°C for 2 minutes in a reflow oven, holding at 210°C for 10 seconds. After that, we checked to see if there was continuity between adjacent connections.

[Example 4]
(Formation of wiring and insulating layer)
A glass substrate (AN100, 300 mm x 400 mm, manufactured by AGC) was irradiated with ultraviolet light and washed. Then, the glass substrate was subjected to chromium sputtering and copper sputtering, and a resist pattern was formed thereon using a dry film resist (Sunfort AQ4038, manufactured by Asahi Kasei Electronics). Next, copper sulfate electrolytic plating (Top Lucina SF, manufactured by Okuno Pharmaceutical Co., Ltd.) was performed on the openings of the resist pattern to form a wiring layer with a thickness of 3 μm. Next, the dry film resist was peeled off with a sodium hydroxide solution at 50°C, and the exposed chromium layer and copper layer were removed with a chromium etching solution (Esclean S-24, manufactured by Sasaki Chemical Industry Co., Ltd.) and a copper etching solution (AD-331, manufactured by Meltec Co., Ltd.), respectively. This formed the wiring. Then, a photosensitive resist (Photoneece PW-1000, manufactured by Toray Industries, Inc.) was used to form an insulating layer with a thickness of 3 μm and an opening pitch of 45 μm so as to cover the wiring.

(Formation of connection part)
Next, electroless nickel plating was performed on the opening of the insulating layer to form a connection part. First, the surface of the wiring exposed in the opening of the insulating layer was degreased using an acidic cleaner (manufactured by Okuno Pharmaceutical Industries, Ltd., ICP Clean S-135K). Next, soft etching was performed by immersing it in a copper etching solution (AD-331, manufactured by Meltec Corporation) heated to 45° C. for 60 seconds. Next, Pd is applied to the surface of the wiring using an activator (manufactured by Okuno Pharmaceutical Industries, Ltd., ICP Accela), and electroless nickel plating (manufactured by Okuno Pharmaceutical Industries, Ltd., ICP Nicolon GM-SE) is applied to the surface of the wiring. A plated part was formed. Thereafter, electroless gold plating (manufactured by Okuno Pharmaceutical Co., Ltd., Flash Gold NC) was performed on the surface of the nickel plating part to form a protective plating part with a thickness of 0.05 μm. Thereby, a wiring board having a connection portion was obtained. The pitch of the connections was 45 μm.

When the vertical cross section of the obtained wiring board was observed using a scanning electron microscope (SEM), it was found that the wiring had a concave shape with a concave surface on the connection side within the opening of the insulating layer. In addition, by observing the vertical cross section of the obtained wiring board using a scanning electron microscope (SEM), the inclination angle of the side surface of the opening in the insulating layer and the depth of the concave recess were measured. . The inclination angle of the side surface of the opening in the insulating layer was 90 degrees, and the depth of the concave depression was 1.2 μm.

[Evaluation 2]
In the wiring board of Example 4, solder paste was applied to adjacent unconnected connection parts, and after holding at 150°C for 2 minutes in a reflow oven and then holding at 210°C for 10 seconds, the adjacent connection parts were The presence or absence of continuity was confirmed. In the wiring board of Example 4, there was no conduction between adjacent connection parts.

Further, when the vertical cross section of the wiring board of Comparative Example 1 was observed using a scanning electron microscope (SEM), it was found that the wiring had a concave shape with a concave surface on the connection side within the opening of the insulating layer. I hadn't. In the wiring board of Comparative Example 1, as shown in Table 1 above, adjacent connection parts were electrically connected.

REFERENCE SIGNS LIST 1 wiring board 2 substrate 2a first surface of substrate 2b second surface of substrate 3a, 3b wiring 4a, 4b insulating layer 5a, 5b opening 6 first connection layer 7 second connection layer 8 connection portion 13 outermost wiring 14 outermost insulating layer P pitch of connection portion

Claims (4)

A wiring board having a base material having a first surface and a second surface opposite to the first surface, and one or more layers of wiring and one or more insulating layers arranged on the first surface side of the base material. And,
The one or more layers of wiring have at least an outermost wiring located farthest from the base material,
the one or more insulating layers are arranged on the surface of the outermost wiring opposite to the surface on the base material side,
at least an outermost insulating layer having an opening located on the outermost wiring,
The wiring board further includes a connection part disposed in the opening of the outermost insulating layer, electrically connected to the outermost wiring , and on which an electronic component is mounted with solder ;
The outermost wiring has a concave shape in which a surface on the connection portion side within the opening of the outermost insulating layer is concave;
A surface of the connection portion that is in contact with the outermost wiring has a convex shape along the concave shape of the outermost wiring,
A wiring board, wherein the pitch of the connecting portions is 50 μm or less. The wiring board according to claim 1, wherein the inclination angle of the side of the opening in the outermost insulating layer is 10 degrees or more and 70 degrees or less. The wiring board according to claim 1 or 2, wherein the height of the connection portion protruding from the surface of the outermost insulating layer opposite the surface on the outermost wiring side is 3 μm or less. The wiring board according to any one of claims 1 to 3, wherein the outermost insulating layer contains a cured product of a photosensitive resin composition.

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