Printed wiring board and method of manufacturing the same

Abstract

To enhance connection reliability between a via conductor formed in a via conductor opening and a via conductor pad.SOLUTION: A printed wiring board according to the present invention includes a via conductor pad, a resin insulating layer covering the via conductor pad, a via conductor opening formed in the resin insulating layer so that at least a part of the via conductor pad is exposed from the resin insulating layer, and a via conductor formed in the via conductor opening, wherein when an upper surface of the resin insulating layer is defined as a first surface and an upper surface of the via conductor pad is defined as a second surface, the via conductor opening is formed of a first opening on the first surface side and a second opening on the second surface side connected to the first opening, the first opening has a tapered shape from the first surface toward the second surface, the second opening has a tapered shape from the second surface toward the first surface, and the second opening is formed on at least the entire second surface. The size of the first opening on the first surface is smaller than the size of the second opening on the second surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printed wiring board including a via conductor pad, a resin insulating layer covering the via conductor pad, a via conductor opening formed in the resin insulating layer so that a portion of the via conductor pad is exposed, and a via conductor formed in the via conductor opening, and a method for manufacturing the same. [Background technology]

[0002] Fig. 6 is a diagram showing one embodiment of a conventional printed wiring board disclosed in Patent Document 1. In Fig. 6, a printed wiring board 51 includes via conductor pads 52, a resin insulating layer 53 covering the via conductor pads 52, and via conductor openings 54 formed in the resin insulating layer 53 so that a portion of the via conductor pads 52 is exposed. A via conductor (not shown) is formed in the via conductor openings 54. In the printed wiring board 51 shown in Fig. 6, in order to reduce the diameter of the via conductor openings 54, a laser is irradiated onto the resin insulating layer 53 through a support film, thereby forming via conductor openings 54 with side shapes that are nearly vertical. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-099649 Summary of the Invention [Problem to be solved by the invention]

[0004] 6, it is possible to reduce the diameter of the via conductor opening 54 by making the side surface of the via conductor opening 54 closer to vertical. However, since the opening diameter of the via conductor opening 54 on the via conductor pad 52 becomes smaller, the connection reliability between the via conductor formed in the via conductor opening 54 and the via conductor pad 52 tends to decrease. [Means for solving the problem]

[0005] The printed wiring board of the present invention includes a via conductor pad, a resin insulating layer covering the via conductor pad, a via conductor opening formed in the resin insulating layer so that at least a portion of the via conductor pad is exposed, and a via conductor formed in the via conductor opening, wherein when an upper surface of the resin insulating layer is defined as a first surface and an upper surface of the via conductor pad is defined as a second surface, the via conductor opening is formed by a first opening on the first surface side and a second opening on the second surface side connected to the first opening, the first opening is tapered from the first surface toward the second surface, the second opening is tapered from the second surface toward the first surface, the second opening is formed over at least the entire second surface, and a relationship exists in which the size of the first opening on the first surface is smaller than the size of the second opening on the second surface.

[0006] The method for manufacturing a printed wiring board of the present invention is a method for manufacturing the above-mentioned printed wiring board, which includes forming via conductor pads on a substrate, forming plating resists on side surfaces of the via conductor pads, forming Sn films on upper surfaces of the via conductor pads by electroless Sn plating, removing the plating resist, forming a resin insulating layer covering the via conductor pads, and laser processing the resin insulating layer to form via conductor openings formed so that at least a portion of the via conductor pads is exposed, performing an acid treatment to dissolve and remove the Sn film, and performing a desmear treatment to form via conductor openings having a first opening and a second opening.

[0007] Furthermore, the method for manufacturing a printed wiring board of the present invention is the method for manufacturing the printed wiring board described above, which includes forming via conductor pads on a substrate, forming a Sn film on the entire surface of the via conductor pad by electroless Sn plating, forming a resin insulating layer covering the via conductor pad, and laser processing the resin insulating layer to form a via conductor opening formed so that at least a part of the via conductor pad is exposed, performing an acid treatment to dissolve and remove the Sn film, and performing a desmear treatment to form a via conductor opening having a first opening and a second opening, wherein an end of the second opening on the via conductor pad extends beyond the end of the via conductor pad and reaches a side wall of the via conductor pad.

[0008] Furthermore, a method for manufacturing a printed wiring board of the present invention is the above-mentioned method for manufacturing a printed wiring board, comprising the steps of: forming via conductor pads on a substrate; forming plating resist on side surfaces of the via conductor pads; dissolving the via conductor pads to form gaps between the plating resist and the via conductor pads; forming an Sn film on the upper surfaces of the via conductor pads and in the gaps by electroless Sn plating; removing the plating resist; forming a resin insulating layer covering the via conductor pads; and laser processing the resin insulating layer to form via conductor openings formed so that at least a portion of the via conductor pads is exposed; performing an acid treatment to dissolve and remove the Sn film; and performing a desmear treatment to form a via conductor opening having a first opening and a second opening, wherein an end of the second opening on the via conductor pad extends beyond the end of the via conductor pad and reaches a side wall of the via conductor pad. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating a first embodiment of a printed wiring board according to the present invention. [Figure 2] 5A and 5B are diagrams illustrating a second embodiment of a printed wiring board according to the present invention. [Figure 3A]FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 3B] FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 3C] FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 3D] FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 3E] FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 3F] FIG. 2 is a diagram for explaining one step of the first embodiment of the printed wiring board according to the present invention. [Figure 4A] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 4B] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 4C] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 4D] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 4E] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 5A] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 5B] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 5C] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 5D] FIG. 4 is a diagram for explaining one step of the second embodiment of the printed wiring board according to the present invention. [Figure 6] 1A and 1B are diagrams illustrating an embodiment of a conventional printed wiring board. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a printed wiring board according to the present invention will be described with reference to the drawings. In the examples shown in Figures 1, 2, 3A-3F, 4A-4D, and 5A-5D, the dimensions of each component, particularly the height dimension, are depicted as dimensions different from the actual dimensions in order to better understand the features of the present invention. Furthermore, components typically found on printed wiring boards, such as wiring and bumps, are not depicted in order to better understand the features of the present invention.

[0011] <Printed wiring board according to the present invention> Fig. 1 is a diagram illustrating a first embodiment of a printed wiring board according to the present invention. In the first embodiment shown in Fig. 1, the printed wiring board 1 includes via conductor pads 2 on a substrate S, a resin insulating layer 3 covering the via conductor pads 2, and via conductor openings 4 formed in the resin insulating layer 3 so that at least a portion of the via conductor pads 2 is exposed. A via conductor (not shown) is formed in the via conductor opening 4.

[0012] 1 , the printed wiring board according to the present invention is characterized in that, when the upper surface of the resin insulating layer 3 is defined as the first surface F1 and the upper surface of the via conductor pad 2 is defined as the second surface F2, the via conductor opening 4 is formed of a first opening 4-1 on the first surface F1 side and a second opening 5-2 on the second surface F2 side that is connected to the first opening 4-1. The first opening 4-1 is tapered from the first surface F1 to the second surface F2, and the second opening 4-2 is tapered from the second surface F2 to the first surface F1. Furthermore, the second opening 4-2 is formed over the entire second surface F2, and the relationship is satisfied: (size O1 of the first opening 4-1 on the first surface F1 < size O2 of the second opening 4-2 on the second surface F2).

[0013] In the first embodiment of the printed wiring board 1 described above, it is preferable that the ratio (depth D1 of first opening 4-1 / depth D2 of second opening 4-2) is not less than 5 and not more than 30. If the ratio (depth D1 of first opening 4-1 / depth D2 of second opening 4-2) is less than 5 or exceeds 30, it may be difficult to satisfy the other requirements described above.

[0014] In the printed wiring board 1 of the present invention according to the first embodiment described above, the via conductor opening 4 is formed by the first opening 4-1 and the second opening 4-2, and has the relationship (size O1 of the first opening 4-1 on the first surface F1<size O2 of the second opening 4-2 on the second surface F2), so that even if the size O1 of the first opening 4-1 on the first surface F1 is small (for example, 30 μm or less), the contact area between the via conductor formed in the via conductor opening 4 and the via conductor pad 2 can be increased. Therefore, the connection reliability between the via conductor formed in the via conductor opening 4 and the via conductor pad 2 can be increased.

[0015] Fig. 2 is a diagram for explaining a second embodiment of a printed wiring board according to the present invention. In the second embodiment shown in Fig. 2, similar to the embodiment shown in Fig. 1, the printed wiring board 1 includes a via conductor pad 2, a resin insulating layer 3, and a via conductor opening 4 having a first opening 4-1 and a second opening 4-2. The other embodiment shown in Fig. 2 differs from the first embodiment shown in Fig. 1 in that an end 4-2a of the second opening 4-2 on the via conductor pad 2 extends beyond an end 2a of the via conductor pad 2 to reach a sidewall 2b of the via conductor pad 2.

[0016] In the printed wiring board 1 of the present invention according to the second embodiment described above, the end 4-2a of the second opening 4-2 on the via conductor pad 2 extends beyond the end 2a of the via conductor pad 2 to reach the side wall 2b of the via conductor pad 2, so that the via conductor formed in the via conductor opening 4 and the via conductor pad 2 are in contact not only on the top surface of the via conductor pad 2 but also on the side surface thereof, thereby making it possible to improve the connection reliability between the via conductor formed in the via conductor opening 4 and the via conductor pad 2 compared to the first embodiment.

[0017] The effect of the second embodiment can be obtained whether the end 4-2a of the second opening 4-2, which reaches onto the side wall 2b of the via conductor pad 2, is partially or entirely beyond the edge 4-2a. In this regard, if the entire edge 4-2a of the second opening 4-2 extends beyond the edge 4-2a, it is possible to easily determine whether the product is good or bad by observing a cross section. It is also preferable that the end 4-2a of the second opening 4-2 is closed at the middle of the side wall 2b of the via conductor pad 2. This is because, when a via conductor is formed in the second opening 4-2, a via conductor with no gaps or the like can be formed, compared to when the end 4-2a of the second opening 4-2 is formed over the entire side wall 2b of the via conductor pad 2.

[0018] <Regarding the manufacturing method of the printed wiring board according to the present invention> 3A to 3F are diagrams illustrating a step of the first embodiment of the printed wiring board according to the present invention. Hereinafter, a method for manufacturing the printed wiring board according to the first embodiment (second openings that do not extend to the sidewalls of the via conductor pads) shown in FIG. 1 will be described with reference to FIGS. 3A to 3F.

[0019] First, as shown in FIG. 3A, a via conductor pad 2 is formed on a substrate S, and a plating resist 11 is formed on the side surface of the via conductor pad 2. Next, as shown in FIG. 3B, a Sn film 12 is formed on the upper surface of the via conductor pad 2 by electroless Sn plating. For example, the technique disclosed in Japanese Patent Application Laid-Open No. 6-252536 can be used for electroless Sn plating. Next, as shown in FIG. 3C, the plating resist 11 is removed. Next, a resin insulating layer 3 is formed to cover the via conductor pad 2, and the resin insulating layer 3 is laser-processed to form a via conductor opening 4 that exposes at least a portion of the via conductor pad 2, as shown in FIG. 3D. Next, an acid treatment using, for example, HCl is performed to dissolve and remove the Sn film 12, as shown in FIG. 3E. Thereafter, a desmear treatment using, for example, KMnO4 is performed to form a via conductor opening 4 having a first opening 4-1 and a second opening 4-2, as shown in FIG. 3F.

[0020] 4A to 4E are diagrams illustrating a step of a second embodiment of a printed wiring board according to the present invention. Hereinafter, a method for manufacturing a printed wiring board according to the second embodiment (second openings extending halfway up the sidewalls of via conductor pads) shown in FIG. 2 will be described with reference to FIGS. 4A to 4E.

[0021] First, as shown in FIG. 4A, a via conductor pad 2 is formed on a substrate S. Next, a Sn film 12 is formed on the entire surface of the via conductor pad 2 by electroless Sn plating. For example, the technique disclosed in Japanese Patent Application Laid-Open No. 6-252536 can be used for electroless Sn plating. Next, a resin insulating layer 3 is formed to cover the via conductor pad 2, and the resin insulating layer 3 is laser-processed to form a via conductor opening 4 that exposes at least a portion of the via conductor pad 2, as shown in FIG. 4C. Next, an acid treatment using, for example, HCl is performed to dissolve and remove the Sn film 12, as shown in FIG. 4D. Thereafter, a desmear treatment using, for example, KMnO4 is performed to form a via conductor opening 4 having a first opening 4-1 and a second opening 4-2, where an end 4-2a of the second opening 4-2 on the via conductor pad 2 extends beyond the end 2a of the via conductor pad 2 and reaches the sidewall 2b of the via conductor pad 2, as shown in FIG. 4E.

[0022] 5A to 5D are diagrams illustrating a step of a second embodiment of a printed wiring board according to the present invention. Hereinafter, a method for manufacturing a printed wiring board according to the second embodiment (second openings extending halfway up the sidewalls of via conductor pads) shown in FIG. 2 will be described with reference to FIGS. 5A to 5D.

[0023] First, as shown in FIG. 5A, a via conductor pad 2 is formed on a substrate S, and a plating resist 11 is formed on the side surface of the via conductor pad 2. Next, in the case of a via conductor pad made of, for example, Cu, the Cu is dissolved to form a gap 13 between the plating resist 11 and the via conductor pad 2, as shown in FIG. 5B. In this example, the gap 13 extends partway between the plating resist 11 and the via conductor pad 2. Next, as shown in FIG. 5C, a Sn film 12 is formed on the upper surface of the via conductor pad 2 and in the gap 13 by electroless Sn plating. For example, the technique disclosed in Japanese Patent Laid-Open Publication No. 6-252536 can be used for electroless Sn plating. Next, the plating resist 11 is removed, as shown in FIG. 5D.

[0024] 4C to 4E described above are then performed. That is, a resin insulating layer 3 is formed to cover the via conductor pads 2, and the resin insulating layer 3 is laser-processed to form via conductor openings 4 that expose at least a portion of the via conductor pads 2, as shown in FIG. 4C. Next, an acid treatment using, for example, HCl is performed to dissolve and remove the Sn film 12, as shown in FIG. 4D. Thereafter, a desmear treatment using, for example, KMnO4 is performed to form the via conductor openings 4, as shown in FIG. 4E, which have a first opening 4-1 and a second opening 4-2, and the end 4-2a of the second opening 4-2 on the via conductor pad 2 extends beyond the end 2a of the via conductor pad 2 and reaches the sidewall 2b of the via conductor pad 2. [Explanation of symbols]

[0025] 1. Printed wiring board 2 Via conductor pads 2a End of via conductor pad 3 Resin insulation layer 4 Opening for via conductor 4-1 First opening 4-2 Second opening 4-2a End of the second opening 11 Plating resist 12 Sn film 13 Gap S board D1 Depth of first opening D2 Depth of second opening O1 Size of first opening O2 Size of the second opening

Claims

1. A printed wiring board comprising: a via conductor pad; a resin insulating layer covering the via conductor pad; a via conductor opening formed in the resin insulating layer so that at least a part of the via conductor pad is exposed; and a via conductor formed in the via conductor opening, When the upper surface of the resin insulating layer is defined as a first surface and the upper surface of the via conductor pad is defined as a second surface, the via conductor opening is formed by a first opening on the first surface side and a second opening on the second surface side connected to the first opening, the first opening has a tapered shape from the first surface toward the second surface, and the second opening has a tapered shape from the second surface toward the first surface; the second opening is formed over at least the entire second surface; There is a relationship that the size of the first opening on the first surface is smaller than the size of the second opening on the second surface.

2. 2. The printed wiring board according to claim 1, wherein an end of said second opening on said via conductor pad extends beyond an end of said via conductor pad and reaches a side wall of said via conductor pad.

3. 3. The printed wiring board according to claim 2, wherein the second opening that reaches the side wall of the via conductor pad is closed at the middle of the side wall.

4. 2. The printed wiring board according to claim 1, wherein the ratio of the depth of the first opening to the depth of the second opening is 5 or more and 30 or less.

5. 2. The method for manufacturing a printed wiring board according to claim 1, forming a via conductor pad on a substrate and forming a plating resist on a side surface of the via conductor pad; forming a Sn film on the upper surface of the via conductor pad by electroless Sn plating; removing the plating resist; forming a resin insulating layer covering the via conductor pads, and performing laser processing on the resin insulating layer to form via conductor openings formed so as to expose at least a portion of the via conductor pads; performing an acid treatment to dissolve and remove the Sn film; By performing the desmearing process, a via conductor opening having a first opening and a second opening is formed.

6. The method for manufacturing a printed wiring board according to claim 2, forming via conductor pads on a substrate; forming a Sn film on the entire surface of the via conductor pad by electroless Sn plating; forming a resin insulating layer covering the via conductor pads, and performing laser processing on the resin insulating layer to form via conductor openings formed so as to expose at least a portion of the via conductor pads; performing an acid treatment to dissolve and remove the Sn film; By performing the desmearing process, a via conductor opening is formed, which has a first opening and a second opening, and the end of the second opening on the via conductor pad extends beyond the end of the via conductor pad and reaches the side wall of the via conductor pad.

7. The method for manufacturing a printed wiring board according to claim 2, forming a via conductor pad on a substrate and forming a plating resist on a side surface of the via conductor pad; dissolving the via conductor pads to form gaps between the plating resist and the via conductor pads; forming a Sn film on the upper surface of the via conductor pad and in the gap by electroless Sn plating; removing the plating resist; forming a resin insulating layer covering the via conductor pads, and performing laser processing on the resin insulating layer to form via conductor openings formed so as to expose at least a portion of the via conductor pads; performing an acid treatment to dissolve and remove the Sn film; By performing the desmearing process, a via conductor opening is formed, which has a first opening and a second opening, and the end of the second opening on the via conductor pad extends beyond the end of the via conductor pad and reaches the side wall of the via conductor pad.

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