Printed wiring board

Abstract

To reduce warpage of a printed wiring board and improve connection reliability between the printed wiring board and an electronic component.SOLUTION: A printed wiring board according to the present invention includes a first reinforcing conductor formed on the top layer of the printed wiring board in correspondence with the areas directly below the four corners of a mounted electronic component, a second reinforcing conductor formed on an inner layer of the printed wiring board in correspondence with the first reinforcing conductor, and a plurality of via conductors connecting the first reinforcing conductor and the second reinforcing conductor. In a preferred embodiment, the planar shape of the first reinforcing conductor and the planar shape of the second reinforcing conductor are substantially the same. Furthermore, the first reinforcing conductor, the second reinforcing conductor, and the via conductor are each independent and not connected to other circuits.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printed wiring board having conductor portions directly below the four corners of an electronic component mounted thereon. [Background technology]

[0002] Conventionally, printed wiring boards having conductor portions directly below the four corners of mounted electronic components have been known (for example, Patent Document 1). FIGS. 3(a) and 3(b) are diagrams illustrating an embodiment of a conventional printed wiring board. FIG. 3(a) is a plan view of a top layer 52 of a printed wiring board 51, and FIG. 3(b) is a cross-sectional view of part A of the printed wiring board 51 shown in FIG. 3(a). In FIGS. 3(a) and 3(b), conductor portions 55 are formed at each of the four corners 54 of a C4 area 53 on which electronic components (not shown) are mounted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-179409 Summary of the Invention [Problem to be solved by the invention]

[0004] 3(a) and 3(b), warpage can be prevented to some extent by forming conductor portions 55 at each of the four corners 54 of C4 area 53 on top layer 52. However, with the increasing sophistication of electronic components in recent years, it has become necessary to enlarge C4 area 53, and there has been a problem that warpage of printed wiring board 51 cannot be sufficiently prevented by conductor portions 55 on top layer 52 alone. [Means for solving the problem]

[0005] The printed wiring board of the present invention includes a first reinforcing conductor formed on the top layer of the printed wiring board in correspondence with the areas directly below the four corners of a mounted electronic component, a second reinforcing conductor formed on an inner layer of the printed wiring board in correspondence with the first reinforcing conductor, and a plurality of via conductors connecting the first reinforcing conductor and the second reinforcing conductor. [Brief explanation of the drawings]

[0006] [Figure 1] 1A and 1B are diagrams illustrating an embodiment of a printed wiring board according to the present invention. [Figure 2] 1A and 1B are diagrams for explaining a technology that is a premise of a printed wiring board according to the present invention; [Figure 3] 1A and 1B are diagrams illustrating an embodiment of a conventional printed wiring board. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of a printed wiring board according to the present invention will be described with reference to the drawings. In the example shown in Figures 1(a), 1(b), and 2, the dimensions of each component, particularly the height dimension, are shown 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 shown in order to better understand the features of the present invention.

[0008] <Technology underlying the printed wiring board according to the present invention> FIG. 2 is a diagram illustrating a technology underlying the printed wiring board according to the present invention. In FIG. 2, a C4 area 22 for mounting electronic components (not shown) is located approximately in the center of a printed wiring board 21. A plurality of C4 pads 23 for mounting the electronic components are formed within the C4 area 22. Wiring 24 is formed extending from the C4 pads 23 to the outside of the C4 area 22. As shown in FIG. 2, the wiring 24 extends vertically and horizontally from the C4 pads 23. Therefore, on the top layer of the printed wiring board 21, no wiring 24 is present in regions directly below the four corners of the mounted electronic components. In the underlying technology, in order to prevent warping of the printed wiring board 1 due to differences in the density of the wiring 24, reinforcing conductors 25 are formed in regions directly below the four corners of the mounted electronic components on the top layer of the printed wiring board 21.

[0009] <One embodiment of the printed wiring board according to the present invention> 1(a) and 1(b) are diagrams illustrating an embodiment of a printed wiring board according to the present invention. Fig. 1(a) is a plan view of the top layer of the printed wiring board, and Fig. 1(b) is a cross-sectional view of part A of the printed wiring board shown in Fig. 1(a). Note that in the embodiment of the printed wiring board according to the present invention shown in Figs. 1(a) and 1(b), descriptions of components typically present on printed wiring boards, such as wiring and bumps, which were explained in the prerequisite technology, are omitted to allow a better understanding of the features of the present invention.

[0010] 1(a) and 1(b), a printed wiring board 1 according to one embodiment of the present invention includes a first reinforcing conductor 5-1 formed at each of the four corners 4 of the C4 area 3 on the top layer 2 of the printed wiring board 1, corresponding to the areas directly below the four corners of an electronic component (not shown) mounted thereon, a second reinforcing conductor 5-2 formed on an inner layer 6 of the printed wiring board 1, corresponding to the first reinforcing conductor 5-1, and a plurality of via conductors 7 connecting the first reinforcing conductor 5-1 and the second reinforcing conductor 5-2.

[0011] 1(a) and 1(b) according to one embodiment of the present invention, in addition to the first reinforcing conductor 5-1 corresponding to the reinforcing conductor 25 described in the prerequisite technology, the second reinforcing conductor 5-2 is formed in the inner layer 6. Furthermore, a plurality of via conductors 7 are formed between the first reinforcing conductor 5-1 and the second reinforcing conductor 5-2. Therefore, compared to the prerequisite technology, deformation of the reinforcing conductor can be eliminated, increasing the rigidity of the printed wiring board 1, thereby further reducing warpage of the printed wiring board 1. As a result, the connection reliability between the printed wiring board 1 and electronic components can be improved.

[0012] In the printed wiring board 1 according to one embodiment of the present invention, it is preferable that the planar shape of the first reinforcing conductor 5-1 and the planar shape of the second reinforcing conductor 5-2 are substantially the same, and that the first reinforcing conductor 5-1, the second reinforcing conductor 5-2, and the via conductor 7 are each independent and not connected to other circuits. Either case is preferable because it can more suitably reduce warpage of the printed wiring board 1 and further improve the connection reliability between the printed wiring board 1 and electronic components.

[0013] 1(b) shows two via conductors 7, the number of via conductors 7 is not limited to two, and it goes without saying that it is possible to form two or more via conductors 7. Furthermore, in FIGS. 1(a) and 1(b), the first reinforcing conductor 5-1 and the second reinforcing conductor 5-2 are shown as having a rectangular planar shape, but it goes without saying that the planar shapes of the first reinforcing conductor 5-1 and the second reinforcing conductor 5-2 are not limited to a rectangular shape, and may be other shapes.

[0014] <Regarding the manufacturing method of the printed wiring board according to the present invention> In the printed wiring board 1 according to one embodiment of the present invention, the first reinforcing conductor 5-1, the second reinforcing conductor 5-2, and the via conductor 7 can be manufactured when manufacturing the wiring and pads of the layers in which they are located. Specifically, the first reinforcing conductor 5-1 can be formed when forming the wiring and pads of the uppermost layer 2, the second reinforcing conductor 5-2 can be formed when forming the wiring and pads of the inner layer 6, and the via conductor 7 can be formed when forming the interlayer insulating layer of the uppermost layer 2. [Explanation of symbols]

[0015] 1, 21 Printed wiring board 2. Top floor 3, 22 C4 Area 4 Corner 5-1 First reinforcing conductor 5-2 Second reinforcing conductor 6 Inner layer 7 Via conductor 23 C4 pad 24 Wiring 25 Reinforcing conductor

Claims

1. A printed wiring board, first reinforcing conductors formed on the top layer of the printed wiring board in positions directly below the four corners of the mounted electronic component; a second reinforcing conductor formed on an inner layer of the printed wiring board in correspondence with the first reinforcing conductor; a plurality of via conductors connecting the first reinforcing conductor and the second reinforcing conductor; Includes.

2. 2. The printed wiring board according to claim 1, wherein the first reinforcing conductor and the second reinforcing conductor have substantially the same planar shape.

3. 3. The printed wiring board according to claim 1, wherein each of the first reinforcing conductor, the second reinforcing conductor, and the via conductor is independent and not connected to other circuits.

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