JPH0974276A - Surface-mounting printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a bypass capacitor in mounting area to an irreducible minimum by a method wherein the bypass capacitor is built inside a surface- mounting printed wiring board body. SOLUTION: A copper foil layer 2 is provided to both the sides of a board 1, and an insulating layer or a board 3 is provided to each outer side of the copper foil layers 2. Furthermore, a signal wire 4 is provided to each outer side of the boards 3. The insulating layer 3 formed on the outer surface of the copper foil pattern 2 can be easily photoetched if it is formed of ultraviolet, curing resin or the like, whereby a space where a capacitor is housed can be formed, so that a space which communicates with the outside and inside is provided to the insulating layer 3, and a bypass capacitor 6 is provided in the space. That is, a bypass capacitor can be built inside a board body, so that it can be reduced to an irreducible minimum in mounting area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of printed wiring boards, and more particularly, it relates to a multilayer printed wiring board on which surface-mounted components having a high operating frequency above the HF band are mounted at high density.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventionally proposed printed wiring board. As can be seen from the figure, the conventional printed wiring board itself has a solid surface whose inner layer is a power line or a ground line. Since the copper foil of No. 2 is used and the substrate (prepreg) 1 which is an insulator is arranged between the layers, the dielectric constant is about 5 and the electrostatic capacitance between the power supply and ground layers is small. It cannot happen.

FIG. 4 shows a part of a conventional printed wiring board; L
It shows the operating status by implementing SI5, etc.
In order to reduce noise such as I5, a bypass capacitor 6 for noise reduction is arranged around the power source end of the LSI 5.

FIG. 7 shows an example of a power bus designed for reinforcing the power supply line of a conventional printed wiring board, in which a noise reducing bypass capacitor is arranged in the power bus 8.

[0005]

The surface mount printed wiring board shown in FIG. 4 is becoming smaller and lighter and the mounting density of components is becoming higher. However, it is possible to prevent noise due to electrostatic induction or electromagnetic induction. Therefore, for the purpose of reducing the high frequency impedance, the bypass capacitor 6 is used as a mounting component L.
Although it is additionally mounted around the power supply terminal of SI5, it becomes difficult to easily secure the component mounting area such as the bypass capacitor 6.

Further, in the case of the printed wiring board on which the power bus 8 is mounted as shown in FIG. 7, the current path of the bypass capacitor is from the lead of the surface mount component to the power wiring pattern of the printed wiring board, and further the bypass capacitor in the power bus 8. After that, since the route is from the power bus ground line to the wiring pattern of the printed wiring board, the current route becomes long. Also, in order to shorten the current route, if the shape of the power bus is matched with the shape of the surface mount component and the bypass capacitor is placed in the power bus so as to match the power pin and the ground pin, the power bus product type configuration will be large. It becomes so expensive that it becomes impractical.

In addition, the operating frequency has become relatively high at several tens of MHz, and it is important to shorten the current path in order to reduce the impedance. However, the printed wiring board flowing through the mounting bypass capacitor 6 is required. Could not shorten the current route 7. When the power bus is used, the current path becomes longer and the effect of the bypass capacitor cannot be expected.

Therefore, the problem to be solved by the present invention is to minimize the mounting area of the bypass capacitor mounted on the surface mount printed wiring board and to minimize the route of the high frequency current which may become noise flowing through the bypass capacitor. Another object of the present invention is to provide a surface mount printed wiring board that minimizes the current path area.

[0009]

The surface mount printed wiring board provided by the present invention has a bypass capacitor incorporated in the body of the surface mount printed wiring board.

The specific arrangement of the bypass capacitor component is as follows: Insert the high-frequency power source by inserting it between the solid surface copper foil conductor of the inner layer to be the power source line or the ground line in the printed wiring board body and the pad for the surface mount component. It would be nice to be in control of the route. In that case, the bypass capacitor component may be provided in the insulating layer between the solid surface copper foil conductor of the inner layer to be the power supply line or the ground line in the printed wiring board body and the surface mount component pad.

[0011]

1 shows an embodiment of a surface mount printed wiring board according to the present invention, and FIG. 3 shows a surface mount example using the same printed wiring board. The printed wiring board body in this embodiment has a four-layer structure. That is, a solid surface copper foil layer 2 to be a power line or a ground line is provided on both surfaces of a substrate (prepreg) 1, and an insulating layer or substrates 3 and 3 (including the substrate or prepreg are also included on each copper foil layer 2). Is provided, and signal line layers 4 and 4 such as copper foil are further formed on the outer surface side thereof. The signal line layer 4 such as the copper foil includes a pad for surface mount component.

However, the insulating layer 3 (substrate or prepreg) formed on the outside of the copper foil pattern layer 2 can be easily photo-etched by using an ultraviolet curable resin or the like, whereby a bypass capacitor can be formed. A sandwiching space can also be formed. Therefore, the insulating layer 3 is provided with a space communicating with the inside and outside, and the bypass capacitor 6 is provided in this space portion.

The bypass capacitor 6 is fixed to the copper foil pattern layer 2 by soldering or the like and is incorporated in a predetermined space of the insulating layer 3. After this, a signal line layer (pads for surface mount components) such as copper foil by electroless plating etc.
4 is formed. This allows the bypass condenser 6
Was inserted between the solid surface-shaped copper foil layer 2 to be the power supply line or the ground line and the layer 4 of the surface mount component pad, and served as a literal bypass capacitor.

FIG. 3 shows an example in which the LSI 5 is mounted on the printed wiring board body constructed as described above. According to this mounting example, the current path is, as shown by reference numeral 7, from the lead of the LSI 5 which is a mounting component, through the mounting component pad 4 of the printed wiring board main body, through the internal bypass capacitor 6, and Since it flows to the other lead of the LSI 5 through the solid copper foil layer 2 of the inner layer, it is not necessary to externally attach the bypass capacitor 6 in the vicinity of the LSI 5 which is a mounting component, as shown in FIG.
The shortest current route can be secured, and the loop cross-sectional area can be minimized to reduce the radiation noise.

In the above-described embodiment, the bypass capacitor 6 is incorporated in the insulating layer 3 on one side of the intermediate substrate (prepreg) 1, but the present invention is not limited to this, and the structure shown in FIG.
As in the second embodiment, the bypass capacitors 6 and 6 are provided in both insulating layers 3 and 3 to enable surface mounting on both surfaces. In FIG. 5, the same parts as those of the embodiment of FIGS. 1 and 3 are referred to by the same reference numerals, and therefore the above description should also be referred to.

FIG. 6 shows a third embodiment of the surface mount printed wiring board according to the present invention, which is composed of an example of 6 layers, which is more than 4 layers of FIG. The same parts as those in the embodiments of FIGS. 1 and 3 are referred to by the same reference numerals, and therefore the above description should also be referred to.

[0017]

According to the present invention as described above, since the bypass capacitor is incorporated in the main body of the surface mount printed wiring board, it is necessary to externally mount the bypass capacitor on the printed board. Is eliminated, and the current path can be set within the range of the thickness of the printed wiring board. Therefore, the mounting area of the bypass capacitor mounted on the surface mount printed wiring board is minimized, and the route of high-frequency current that may cause noise flowing through the bypass capacitor is minimized to minimize the current path area, The intended purpose of providing a surface mount printed wiring board can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a surface mount printed wiring board according to the present invention.

FIG. 2 is a sectional view of an essential part showing an example of a conventional printed wiring board.

FIG. 3 is an explanatory diagram showing surface mounting and operating conditions of the printed wiring board shown in FIG.

FIG. 4 is an explanatory diagram showing surface mounting and operating conditions of the printed wiring board shown in FIG.

FIG. 5 is a sectional view of an essential part showing another embodiment of the surface mount printed wiring board according to the present invention.

FIG. 6 is a sectional view of an essential part showing still another embodiment of the surface mount printed wiring board according to the present invention.

FIG. 7 is an explanatory diagram showing another mounting and operating state of the conventional surface mount printed wiring board.

[Explanation of symbols]

 1 board (prepreg) 2 surface pattern layer of power supply or ground wire 3 insulating layer or board 4 signal line layer such as copper foil (including pads for surface mount parts) 5 LSI 6 bypass capacitor 7 high frequency power current

Claims (3)

[Claims] 1. A surface mount printed wiring board, wherein a bypass capacitor is incorporated in the body of the surface mount printed wiring board. 2. A bypass capacitor part is inserted between a solid surface copper foil conductor of an inner layer to be a power supply line or a ground line in a printed wiring board main body and a surface mount component pad to control a route of a high frequency power supply. The surface-mounted printed wiring board according to claim 1, wherein 3. The bypass capacitor component is provided in an insulating layer between a solid surface copper foil conductor of an inner layer which becomes a power supply line or a ground line in a printed wiring board body and a pad for surface mounting component. The surface mount printed wiring board according to claim 1.