JP2019041031A - Wiring board - Google Patents

Abstract

To provide a wiring board capable of stably activating an electronic component.SOLUTION: A wiring board comprises: an insulation layer 3; a plurality of wiring conductors 4 which are located on a surface of the insulation layer 3 and have linear shapes and planar shapes; and a solder resist 5 which is located on the surface of the insulation layer 3 exposed among the wiring conductors 4 and on the surfaces of the wiring conductors 4 and has openings 8 which expose entire upper surfaces and entire side faces of some wiring conductors 4 out of the plurality of wiring conductors 4 and recesses 10 which expose entire upper surfaces and part of side faces of other wiring conductors 4 out of the plurality of wiring conductors 4. In each opening 8, a first electrode 9 composed of part of the linear-shape wiring conductor 4a with both ends being connected to the planar-shape wiring conductors 4b is located; and in each recess 10, a second electrode 11 composed of one end part of the linear-shape wiring conductor 4a is located.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a wiring board on which an electronic component such as a semiconductor element is mounted.

  Currently, a wiring board is developed in which fine wiring conductors are located at a high density on the surface of an insulating layer. A solder resist is located on the surface of the insulating layer and the surface of the wiring conductor located on the surface layer of such a wiring board. The solder resist has a recess that exposes a part of the wiring conductor as an electrode. The electrode is used for connection with an electronic component such as a semiconductor element. In the recess, the side surface of the wiring conductor is covered with the solder resist from the insulating layer side to the middle in the thickness direction.

JP 2009-33084 A

  The wiring board has been miniaturized. Correspondingly, a fine recess may be required in the solder resist. However, since the solder resist has poor processability for fine recesses, the wiring conductor may be covered with the solder resist not only on the side surfaces but also on a part of the upper surface in the recesses. As a result, the electrical connection between the electronic component and the electrode may be hindered by the solder resist, and the electronic component may not operate stably.

  The wiring board of the present disclosure is located on the surface of the insulating layer, the insulating layer, a plurality of wiring conductors having a linear shape and a surface shape, and the surface of the insulating layer and the surface of the wiring conductor exposed between the wiring conductors. An opening that exposes the entire upper surface and side surfaces of some of the plurality of wiring conductors, and the entire upper surface and side surfaces of other wiring conductors of the plurality of wiring conductors. A solder resist having a concave portion exposing a part thereof, and a first electrode comprising a part of a linear wiring conductor having both ends connected to a planar wiring conductor is located in the opening. In addition, a second electrode formed by one end portion of a linear wiring conductor is located in the recess.

  According to the wiring board of the present disclosure, it is possible to provide a wiring board capable of stably operating electronic components such as semiconductor elements.

FIG. 1 is a schematic cross-sectional view illustrating an embodiment of a wiring board according to the present disclosure. FIG. 2 is a schematic top view illustrating an exemplary embodiment of a wiring board according to the present disclosure. FIG. 3 is a first main part perspective view showing an embodiment of a wiring board according to the present disclosure. FIG. 4 is a second main part perspective view illustrating an embodiment of the wiring board according to the present disclosure. FIG. 5 is a third principal part perspective view illustrating an embodiment of the wiring board according to the present disclosure. FIG. 6 is a fourth essential part perspective view illustrating an embodiment of a wiring board according to the present disclosure.

  Next, the wiring board 1 according to the embodiment of the present disclosure will be described with reference to FIGS. 1 is a cross-sectional view taken along the line XX shown in FIG. FIG. 2 is a top view illustrating an exemplary embodiment of the wiring board 1 of the present disclosure. 3 and 4 are perspective views of the main part of the wiring board 1. FIG.

  The wiring board 1 has an insulating plate 2, an insulating layer 3, a wiring conductor 4, and a solder resist 5. The wiring board 1 includes a central region C and a peripheral region S located outside the central region C in plan view. The central region C and the surrounding region S are regions included in the insulating layer 3. Further, the central region C and the surrounding region S can be regarded as regions corresponding respectively to the central portion and the outer peripheral portion of the upper surface of the uppermost insulating layer 3.

  The insulating plate 2 includes, for example, an insulating material obtained by impregnating glass fiber with an insulating material such as an epoxy resin or a bismaleimide triazine resin. The insulating plate 2 has a plurality of through holes 6 penetrating the upper surface and the lower surface. The insulating plate 2 is a part that ensures the mechanical strength of the wiring board 1. The insulating plate 2 is formed into a flat plate shape by laminating a plurality of prepregs obtained by impregnating reinforcing glass fibers with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin, and performing pressing under heating. The through hole 6 is formed by performing processing such as drilling, laser processing, or blasting on the insulating plate 2.

  The insulating layer 3 is located on the upper surface and the lower surface of the insulating plate 2. The insulating layer 3 includes an insulating material such as polyimide resin, epoxy resin or bismaleimide triazine resin, and insulating particles such as silicon oxide or alumina dispersed in the insulating material. The insulating layer 3 has a plurality of via holes 7 whose bottom surfaces are the wiring conductors 4 located on the upper and lower surfaces of the insulating plate 2. The insulating layer 3 is a part that secures an arrangement region of the wiring conductor 4. The insulating layer 3 is formed by depositing a film for an insulating layer containing a thermosetting resin such as a polyimide resin, an epoxy resin, or a bismaleimide triazine resin on the upper and lower surfaces of the insulating plate 2 under a vacuum and thermosetting the film. It is formed. Insulating particles such as silicon oxide or alumina may be dispersed in the thermosetting resin. The via hole 7 is formed by laser processing, for example.

  The wiring conductor 4 is located in the upper and lower surfaces of the insulating plate 2, in the through hole 6, the upper surface of the insulating layer 3 on the upper surface side, the lower surface of the insulating layer 3 on the lower surface side, and the via hole 7. The wiring conductor 4 is made of, for example, an electroless copper plating metal and an electrolytic copper plating metal. The wiring conductor 4 constitutes a conductive path in the wiring board 1. The wiring conductors 4 in the through holes 6 electrically connect the wiring conductors 4 positioned on the upper surface and the lower surface of the insulating plate 2. The wiring conductor 4 in the via hole 7 electrically connects the wiring conductor 4 located on the surface of the insulating plate 2 and the wiring conductor 4 located on the surface of the insulating layer 3.

  The wiring conductor 4 includes a plurality of linear wiring conductors 4a and a plurality of planar wiring conductors 4b. Of the wiring conductors 4, the linear wiring conductor 4 a constitutes an electrode used for connection with an electronic component such as a semiconductor element. Of the linear wiring conductor 4a, the portion exposed from the solder resist 5 is connected to the electronic component. Details of this connection will be described later. Of the wiring conductors 4, the planar wiring conductor 4 b has a function of reducing the conduction resistance of the entire wiring conductor 4.

  Both ends of the linear wiring conductor 4a located in the central region C are connected to the planar wiring conductor 4b. The thickness of the wiring conductor 4 is set to 10 to 30 μm, for example. The width of the linear wiring conductor 4a is set to 10 to 30 μm, for example. The surface of the wiring conductor 4 is roughened. Thereby, a solder resist 5 described later can be firmly adhered to the surface of the wiring conductor 4. The arithmetic average roughness Ra of the surface of the wiring conductor 4 is set to 0.3 to 0.7 μm, for example. For the roughening treatment, for example, an organic acid etching solution is used. The wiring conductor 4 is formed by a plating technique such as a semi-additive method.

  The solder resist 5 is located on the upper surface of the insulating layer 3 on the upper surface side of the insulating plate 2 and on the lower surface of the insulating layer 3 on the lower surface side of the insulating plate 2. The solder resist 5 includes an insulating material such as an epoxy resin or a polyimide resin. The solder resist 5 mainly has a function of protecting the wiring conductor 4 from the external environment. The solder resist 5 also has a function of exposing a part of the wiring conductor 4 at a predetermined position and providing an electrode for connecting an electronic component at the predetermined position. Details of this will be described next.

  The solder resist 5 located on the upper surface side has, in the central region C, a plurality of openings 8 that individually expose a part of the plurality of linear wiring conductors 4a. The opening 8 has, for example, a circular shape when viewed from above. In the opening 8, the first electrode 9 is located, in which the entire upper surface and side surfaces of the linear wiring conductor 4 a are exposed. The first electrode 9 is connected to an electrode of an electronic component such as a semiconductor element via solder, for example. The diameter of the opening 8 is set to 50 to 150 μm, for example.

  The solder resist 5 located on the upper surface side has, in the surrounding area S, a recess 10 that exposes at least one end portion of a plurality of linear wiring conductors 4a. The concave portion 10 is a portion having a smaller thickness than the other portions of the solder resist 5. The recess 10 has, for example, a frame shape in plan view. In the recess 10, the second electrode 11 formed by exposing the entire upper surface and a part of the side surface of the linear wiring conductor 4 a is located. In other words, the side surface of the linear wiring conductor 4a is covered with the solder resist 5 from the insulating layer 3 side to the middle in the thickness direction in the recess 10, and the side and upper surfaces not covered with the solder resist 5 are first. Two electrodes 11 are formed. For this reason, the second electrode 11 protrudes from the upper surface of the solder resist 5 in the recess 10. The protrusion amount of the second electrode 11 is set to 2 to 20 μm, for example. The second electrode 11 is connected to an electrode of an electronic component such as a semiconductor element via solder, for example. In addition, the recessed part 10 may be the same depth in the whole region, and may differ in part from other parts.

  The central region C and the surrounding region S are, for example, the external dimensions of the electronic component to be mounted in a plan view, the region where the electrode of the electronic component is located (the area of the region in the plan view), or the solder resist 5 It may be appropriately set according to conditions such as ease of forming the opening 8 or the recess 10. For example, about half of the distance from the center to the outer periphery of the part of the wiring board 1 (the upper surface of the uppermost insulating layer 3) where the electrodes of the electronic component face each other can be set as the central region C. The outside can be set as the surrounding area S.

  Such first electrode 9 and second electrode 11 are required to have solder wettability. For this reason, the first electrode 9 and the second electrode 11 have a top surface and side surfaces from which foreign substances are effectively removed by performing a cleaning process with, for example, a sulfuric acid-based etching solution. In this case, the cleaning process is relatively difficult for the first electrode 9 because the opening 8 is small, but the solder resist 5 in the opening 8 can be removed, so that no foreign matter remains. Further, regarding the second electrode 11, it is necessary to leave a portion covered with the solder resist 5 on a part of the side surface. However, since the recess 10 is relatively large, the cleaning process is relatively easy. The possibility that an unnecessary solder resist 5 may remain on the upper surface of 11 can be reduced.

  The solder resist 5 on the upper surface side is formed as follows, for example. First, a film of a thermosetting resin having photosensitivity such as an acrylic-modified epoxy resin is attached to the surfaces of the insulating layer 3 and the wiring conductor 4 on the upper surface side. Then, the film is cured by exposing a region other than the region corresponding to the opening 8 and the recess 10. Then, the entire upper surface and the entire side surface of the linear wiring conductor 4a are exposed by developing a region corresponding to the uncured opening 8. Further, by developing a region corresponding to the recess 10, the entire upper surface and a part of the side surface of the linear wiring conductor 4 a are exposed. And the soldering resist 5 is formed by exposing the area | region corresponding to the recessed part 10 and hardening the film in the recessed part 10. FIG. In addition, since the surface of the wiring conductor 4 is roughened, the solder resist 5 can be firmly attached to the wiring conductor 4.

  The solder resist 5 located on the lower surface side exposes a part of the wiring conductor 4 as the third electrode 12. The third electrode 12 is electrically connected to an electrode on an external electric substrate via, for example, solder. Thereby, the electronic component connected to the first electrode 9 and the second electrode 11 can be electrically connected to the external electric substrate via the wiring conductor 4.

  As described above, the wiring board 1 of the present example has the first electrode 9 in the central region C, in which the entire upper surface and the entire side surface of the linear wiring conductor 4 a are exposed in the opening 8. Thereby, even when it is necessary to reduce the opening diameter of the opening 8 in response to the miniaturization of the wiring, since the structure is easy to process, the solder resist 5 is attached to the surface of the first electrode 9. The functionality of the first electrode 9 can be improved.

  Further, both ends of the linear wiring conductor 4a constituting the first electrode 9 are connected to the planar wiring conductor 4b. For this reason, even if the miniaturization of wiring advances and the adhesion strength between the linear wiring conductor 4a and the insulating layer 3 decreases, the adhesion strength can be supplemented by the planar wiring conductor 4b. Thereby, it can suppress that the linear wiring conductor 4a (namely, 1st electrode 9) peels from the insulating layer 3. FIG.

  In addition, the wiring substrate 1 of the present example includes the second electrode 11 in which the entire upper surface and a part of the side surface of one end portion of the linear wiring conductor 4a are exposed in the recess 10 in the peripheral region S. Yes. For this reason, even when the miniaturization of the wiring is advanced and the adhesion strength between the one end portion of the linear wiring conductor 4a and the insulating layer 3 is reduced, the side surface of the one end portion of the linear wiring conductor 4a is in the recess 10. In this case, since the solder resist 5 is coated from the insulating layer 3 side to the middle in the thickness direction, the adhesion strength can be supplemented. This is effective when the end portion is not connected to the planar wiring conductor 4b as in the linear wiring conductor 4a constituting the second electrode 11. Thereby, it can suppress that the linear wiring conductor 4a (namely, 2nd electrode 11) peels from the insulating layer 3. FIG.

  Thus, the first electrode 9 whose adhesion strength with the insulating layer 3 is supplemented by the planar wiring conductor 4b and the second electrode 11 whose adhesion strength with the insulating layer 3 is supplemented by the solder resist 5 coexist. As a result, it is possible to provide a wiring board capable of improving the electrode function of the wiring board where the miniaturization of the wiring is advanced and enabling electronic components such as semiconductor elements to operate stably.

  Note that the present disclosure is not limited to the above-described exemplary embodiment, and various modifications can be made without departing from the gist of the present disclosure. For example, in the example of the above-described embodiment, the example in which the surfaces of the first electrode 9 and the second electrode 11 are not covered with other conductors has been shown, but both the first electrode 9 and the second electrode 11, or Either one of the surfaces may be coated with a conductor having excellent solder wettability. Thereby, it becomes easy to electrically connect the first electrode 9 and the second electrode 11 and the electrode of the electronic component via the solder. Examples of such a conductor include a conductor in which electroless gold plating is deposited on the surface of electroless nickel plating.

  Further, for example, in the example of the above-described embodiment, an example in which the shape of the opening 8 in a plan view is a circular shape is shown, but an elliptical shape or an oval shape may be used. Such a shape is advantageous when the openings 8 need to be arranged more densely.

  In addition, for example, in the example of the above-described embodiment, the first electrode 9 and the second electrode 11 in plan view include a right-angled portion between the thin portion and the thick portion, but FIG. 5 and FIG. As shown in FIG. 6, it may include a gentle curve shape. Such a shape having no right-angled portion is advantageous in that the cleaning process becomes easier and foreign matters are effectively removed.

DESCRIPTION OF SYMBOLS 1 Wiring board 3 Insulation layer 4 Wiring conductor 4a Line-shaped wiring conductor 4b Surface-shaped wiring conductor 5 Solder resist 8 Opening 9 First electrode 10 Recess 11 Second electrode

Claims (2)

An insulating layer;
A plurality of wiring conductors located on the surface of the insulating layer and having a linear shape and a planar shape;
An opening that is located on the surface of the insulating layer and the surface of the wiring conductor exposed between the wiring conductors, and exposes the entire upper surface and side surfaces of some of the wiring conductors of the plurality of wiring conductors; And a solder resist having a recess exposing the entire upper surface and a part of the side surface of the other wiring conductor among the plurality of wiring conductors,
In the opening is located a first electrode consisting of a part of the line-shaped wiring conductor whose both ends are connected to the planar wiring conductor,
A wiring board, wherein a second electrode comprising one end portion of the linear wiring conductor is located in the recess.   In plan view, the plurality of first electrodes are located in a central region of the insulating layer, and the plurality of second electrodes are located in a surrounding region located outside the central region. The wiring board according to claim 1, characterized in that:

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