JPH0750476A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To increase the packaging density of components and facilitate the limination of component mounting position, by forming a plurality of through hole rows to be connected with. each pad of a plurality of pad rows corresponding with a plurality of lead terminal rows of a mounting components, in the vicinity of the pad rows in the manner in which at least one row of the through holes is arranged inside a plurality of the pad rows. CONSTITUTION:A plurality of pad rows constituted of a plurality of lead terminal rows of components and a plurality of pads 2 formed so as to correspond with the lead terminal rows are arranged at the mounting positions of components on a board 1. A plurality of through hole rows constituted of a plurality of through holes 3 and through hole lands 3a which correspond with a plurality of pads and are formed in the vicinity of the pads are arranged inside a plurality of the pad rows. A plurality of wires 4 connect a plurality of the pads 2 with a plurality of the through holes 3 and the through hole lands 3a. The occupied area of mounting components wherein the through hole rows are contained becomes the area surrouned by a line outside the pad row, so that the mounting density can be increased.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a multilayer printed wiring board,
In particular, the present invention relates to a multilayer printed wiring board including a plurality of pads for connecting a plurality of lead terminals of a mounted component and through holes connected to these pads and suitable for surface mounting.

[0002]

2. Description of the Related Art FIG. 3 shows an example (first example) of a very general conventional multilayer printed wiring board used for surface mounting.

This multilayer printed wiring board has a plurality of (two rows in this example) leads consisting of a substrate 1 formed of an insulating material and a plurality of lead terminals of the component at the mounting position of the component on the surface of the substrate 1. A plurality of pads 2 respectively formed corresponding to the terminal rows and corresponding to the plurality of lead terminals.
A plurality of (two rows) pad rows and a plurality of through holes 3 and through hole lands 3a connected to predetermined wirings formed on the back surface and inner layer surface of the substrate 1 corresponding to the predetermined pads 2 of these pad rows. And a plurality of wirings 4 respectively connecting the through holes 3 and the through hole lands 3a to the corresponding pads 2, and a wiring 4a other than the wiring 4 between the through holes 3 and the through hole lands 3a and the pads 2. It has a structure.

In this multilayer printed wiring board, the through holes 3 and the through hole lands 3a are formed at arbitrary positions in accordance with the mounting positions of components and the wiring positions of the back surface and inner layer surface. Further, the through hole 3 and the through hole land 3a are not provided for the pad 2 which is not connected to the wiring on the back surface or the inner layer surface.

Further, the through holes 3 and the through hole lands 3a corresponding to all of the plurality of buds 2, respectively.
(Hereinafter, simply referred to as through holes 3) are provided in the vicinity of each pad 2 to connect with a predetermined wiring on the back surface or the inner layer surface, and to judge whether the connection between the wiring and the corresponding pad 2 is good or bad. A second row of conventional multilayer printed wiring boards used is shown in FIG. In this example, all the through holes 3 are arranged outside the pad row.

In this second example, when the pitch of the pads 2 is narrowed due to the miniaturization of the components and the like, when the diameter of the through-hole lands 3a is larger than the width of the pads 2, when the components are mounted by solder reflow or the like. Since solder bridges are likely to occur between the through hole lands 3a adjacent to each other, as shown in FIG. 5, the through holes 3 are arranged in a zigzag pattern (third example), or as shown in FIG.
Of a through hole 3 having a diameter smaller than the width of the pad (in this case, the through hole land 3a is not included) is directly formed in the formation region of the pad 2 (fourth example, for example, JP-A-3-13).
2092).

Further, in the third example shown in FIG. 5, the area occupied by the mounted components is widened, and the inspection operation for judging the quality of the connection of the pad 2 and the wiring 4 is complicated and the like. Accordingly, as shown in FIG. 7, there is also an example (fifth example) in which the through holes 3 are alternately arranged inside and outside the pad row (for example, see Japanese Patent Laid-Open No. 3-44994).

[0008]

In these first conventional multilayer printed wiring boards, the through holes 3 are arranged at arbitrary positions in the first example, so that when the wiring is designed by the CAD system, It is difficult to limit the component mounting position and is unsuitable for CAD design. In the second to fifth examples, the through holes 3 are both on the outside of the pad row or on the lead terminal of the mounted component. Since the through holes 3 are arranged on the outer side and are used for inspection, the area occupied by the mounted components including the through hole array is large, and it is difficult to increase the mounting density of the components. In the case of double-sided mounting, it is necessary to arrange the mounting components so that the through holes 3 at the component mounting positions on one surface are not hidden under the mounting components on the other surface. It has a drawback that it is difficult to increase the packing density of the.

An object of the present invention is to increase the mounting density of components and to easily limit the mounting position of components, which makes CA
An object of the present invention is to provide a multilayer printed wiring board suitable for D design and capable of improving the efficiency of wiring design.

[0010]

A multi-layer printed wiring board according to the present invention comprises a substrate formed of an insulating material, and a plurality of lead terminals formed at a mounting position of the component on the surface of the substrate. A plurality of pad rows formed of a plurality of pads respectively corresponding to the plurality of lead terminals and corresponding to the plurality of lead terminals, and for each of the plurality of pad rows, of the inner side and the outer side of the plurality of pad rows A plurality of through-hole rows formed of a plurality of through-holes formed on one side and on the inner side with respect to at least one pad row, respectively corresponding to the plurality of pads and in close proximity; It has a plurality of wirings corresponding to and connecting with the plurality of through holes.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1A to 1C are plan views of a front surface side, an inner layer surface and a back surface side, respectively, showing a first embodiment of the present invention.

In this embodiment, a board 1 formed of an insulating material and a plurality of lead terminal rows each including a plurality of lead terminals of the part at the mounting position of the part on the surface of the board (in this embodiment, to the right side) A plurality (4) of QFP type components and a plurality of pads 2 (4) formed on the left side and corresponding to the plurality of lead terminals.
Rows and two rows of pad rows, and a plurality of through holes 3 and through hole lands corresponding to and adjacent to each of the plurality of pads inside the plurality of pad rows. A plurality of rows (4 rows and 2 rows) of through holes 3a, a plurality of pads 2, a plurality of through holes 3 and a through hole land 3
and a plurality of wirings 4 correspondingly connected to a (hereinafter simply referred to as through hole 3). In addition to the through hole 3 and the wiring 4 around the pad 2, the through hole 3 for relaying the other wiring 4a is also shown in FIG.

In this embodiment, since each row of through holes 3 is arranged inside the pad row, the area occupied by the mounting components including the through hole row is the area surrounded by the line outside the pad row. Therefore, it can be made smaller than the conventional example shown in FIGS. 4 to 7, and the mounting density can be increased. Although the conventional example shown in FIG. 6 also has an area surrounded by the outside of the pad row, since the position of the through hole is outside the lead terminal of the mounted component, the wiring up to the through hole 3 is put. Since it was only formed by extending
Substantially the same as FIG. 4, FIG. 5, and FIG. 7.

The inspection of the quality of the connection of the pad 2 and the wiring 4 etc. is conducted on the back side because the through hole 3 on the front side is hidden by the mounted components. In the case of double-sided mounting in which components are also mounted on the back surface side, it is necessary to prevent the through-hole row on the back surface side from being hidden under the mounted components. Even in this case, since the through hole array is arranged inside the pad array, the range in which the components cannot be mounted is small, and therefore the mounting density can be increased.

FIG. 2 is a plan view showing a second embodiment of the present invention.

This embodiment uses two of the four row pad examples.
The through hole rows corresponding to the rows are arranged inside the pad row, and the through hole rows corresponding to the other two rows are arranged outside.

When all the through-hole rows are arranged inside the pad row, the area occupied by the mounted components including the through-hole row is minimized, but it may not always be a good idea depending on the arrangement state of the surrounding mounted components. Occurs. In this case, the through hole row is arranged on either the inside or the outside according to the arrangement state of the surrounding mounted components. However, improvement of the mounting density cannot be expected unless at least one of the plurality of through hole rows is arranged inside the pad row.

In these embodiments, each through hole 3 is formed in the vicinity of the corresponding pad 2, that is, in the vicinity of the pad row. Therefore, when the wiring design is performed in the CAD system, the through hole row is formed. The hole mounting can limit the component mounting position, which facilitates the wiring design in the CAD system.

[0020]

As described above, according to the present invention, a plurality of through-hole rows, each of which has a plurality of through-holes connected to the pads of the plurality of pad rows corresponding to the plurality of lead terminal rows of the mounted component, are provided in the vicinity of the pad row. And at least one
By arranging the rows inside the plurality of pad rows, it is possible to reduce the occupied area of the mounting components including the through-hole rows when using the through-holes for connection inspection. In addition, since the through hole array facilitates limiting the component mounting position in the CAD system, the wiring design is facilitated and the efficiency of the wiring design can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a front surface side, an inner layer surface and a back surface side showing a first embodiment of the present invention.

FIG. 2 is a plan view showing a second embodiment of the present invention.

FIG. 3 is a plan view of a first example of a conventional multilayer printed wiring board.

FIG. 4 is a plan view of a second example of a conventional multilayer printed wiring board.

FIG. 5 is a plan view of a third example of a conventional multilayer printed wiring board.

FIG. 6 is a plan view of a fourth example of a conventional multilayer printed wiring board.

FIG. 7 is a plan view of a fifth example of a conventional multilayer printed wiring board.

[Explanation of symbols]

 1 substrate 2 pad 3 through hole 3a through hole land 4 and 4a wiring

Claims (2)

[Claims] 1. A substrate formed of an insulating material, and a plurality of lead terminal rows each composed of a plurality of lead terminals of the component at a mounting position of the component on the surface of the substrate, respectively corresponding to the plurality of lead terminals. A plurality of pad rows formed of a plurality of pads, and for each of the plurality of pad rows, one of the inner side and the outer side of the plurality of pad rows and at least one pad row Respectively connect the plurality of pads and the plurality of through holes to the plurality of through hole rows each including the plurality of through holes formed inside and corresponding to the plurality of pads, respectively. A multilayer printed wiring board having a plurality of wirings. 2. The multilayer printed wiring board according to claim 1, wherein all of the plurality of through hole rows are formed inside the plurality of pad rows.