JPH066043A - Printed wiring board - Google Patents

Abstract

(57) [Summary] [Object] To provide a printed wiring board in which the mounting area of chip components to be mounted is expanded and the density of an IC memory module board is increased without increasing the external dimensions of the board. [Structure] A counterbore hole is formed from the surface of the multilayer board to expose the inner layer circuit pattern, and the chip parts are housed and mounted in the counterbore hole to conduct with the inner layer circuit pattern and separate on the opening edge of the counterbore hole. The printed wiring board on which the chip parts of above are mounted and electrically connected to the surface layer circuit pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, and more particularly to various module boards typified by an IC memory module board having an improved component mounting density.

[0002]

2. Description of the Related Art Conventionally, chip components (TSOP (thin and small package), SOJ (small lead type J package), chip capacitors, etc.) mounted on an IC memory module substrate are densely arranged on the same substrate surface. It has been designed, but recently there is a strong demand for high-density thinning. The IC memory module substrate can meet the demand for higher density to some extent, but it is "JEDEC standard"
There are certain restrictions on the external dimensions of the substrate due to factors such as the above, and the surface area of the substrate is limited. Therefore, the mounting area of the chip components to be mounted is also limited.

[0003]

Therefore, the present invention aims to increase the mounting area of chip components to be mounted and increase the density of various module substrates such as IC memory module substrates without increasing the outer dimensions of the substrate. The present invention is intended to provide a printed wiring board.

[0004]

In the printed wiring board of the present invention for solving the above-mentioned problems, a counterbore is formed from the surface of a multilayer board to expose an inner layer circuit pattern, and a chip component is placed in the counterbore. It is accommodated and mounted to be electrically connected to the inner layer circuit pattern, and another chip component is mounted on the opening edge of the counterbore hole to electrically connect the surface layer circuit pattern.

[0005]

As described above, in the printed wiring board of the present invention, the inner layer circuit pattern is exposed by forming the counterbore from the surface of the multilayer board, so that the chip to be mounted can be mounted without increasing the outer dimension of the board. The circuit pattern area on which the parts are mounted is expanded. Then, the chip component is housed and mounted in the counterbore hole to conduct with the inner layer circuit pattern, and another chip component is mounted on the opening edge of the counterbore hole to conduct with the surface circuit pattern. Increase the density.

[0006]

EXAMPLE An example of a printed wiring board according to the present invention will be described with reference to the drawings. After the four-layer board 1 shown in FIG. 1 is laminated and formed by an ordinary subtractive method, the surface layer, that is, one layer and four layers are formed. Forming circuit patterns 2 and 3 of
(Solder resist) was applied. Next, a counterbore 4 is formed from the surface by drilling to form an inner layer, 3 in this example.
The circuit pattern 5 of the layer was exposed. And counterbore 4
After rust prevention treatment and pre-flux coating, the chip capacitor 6 was directly housed and mounted as shown in FIG. 2, and was soldered to the circuit pattern 5 of the third layer for electrical connection. Then, as shown in FIG. 3, another chip component, TSOP7 in this example, was mounted on the opening edge of the counterbore hole 4 and soldered to the circuit pattern 2 of the first layer for electrical conduction. It should be noted that the conduction between the layers is performed by forming a normal through hole.

In the printed wiring board 8 of the embodiment thus constructed, the counterbore hole 4 is formed from the surface of the four-layer board 1 and the circuit pattern 5 of the third layer is exposed. The area of the circuit pattern on which the chip components to be mounted is mounted is expanding without increasing the outer dimensions of the device. Then, the chip capacitor 6 is accommodated and mounted in the counterbore 4 and electrically connected to the circuit pattern 5 of the third layer, and the TSOP 7 is mounted on the opening edge of the counterbore 4 and electrically connected to the circuit pattern 2 of the first layer. Therefore, high density of the IC memory module substrate is achieved.

In the above embodiment, the counterbore 4 is formed from the surface of the four-layer substrate 1 to expose the circuit pattern 5 of the third layer, but a counterbore is separately formed to form the second layer. It is also possible to expose the circuit pattern of (1) and accommodate and mount an ultra-small chip component for electrical conduction. Further, although the above-mentioned embodiment is applied to the 4-layer substrate 1, a 6-layer substrate, an 8-layer substrate,
It can also be applied to a 10-layer substrate, etc., and even in that case, the inner layer circuit pattern to be exposed by forming the counterbore can be arbitrarily selected. Further, since the inner layer circuit pattern formed by forming the counterbore is exposed to the chip component, the inner layer circuit pattern is formed at the time of manufacturing the multilayer substrate with a predesigned pattern. It can also be applied to various module substrates other than the IC memory module.

[0009]

As described above, in the printed wiring board of the present invention, the mounting area of the chip components to be mounted is expanded without increasing the outer dimensions of the board, so that high density of various module boards such as IC memory module boards can be achieved. Can be achieved. It is also possible to reduce the overall thickness of the module when mounting chip components.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a state in which a counterbore is formed in the surface of a four-layer substrate to expose a circuit pattern of a third layer.

FIG. 2 is a cross-sectional view of essential parts showing a state in which a chip capacitor is housed and mounted in a counterbore hole of the four-layer substrate of FIG. 1 and is electrically connected to the circuit pattern of the third layer.

FIG. 3 shows TSO on the opening edge of the counterbore hole of the four-layer substrate of FIG.
It is a principal part sectional view which shows the state which mounted P and was made to conduct with the circuit pattern of the 1st layer.

[Explanation of symbols]

 1 4 layer board (multilayer board) 2 1st layer circuit pattern 3 4th layer circuit pattern 4 Counterbore hole 5 3rd layer circuit pattern 6 Chip capacitor 7 TSOP 8 Printed wiring board

Claims (1)

[Claims] 1. A counterbore hole is formed from the surface of a multi-layer substrate to expose an inner layer circuit pattern, and a chip component is housed and mounted in the counterbore hole so as to be electrically connected to the inner layer circuit pattern and on an opening edge of the counterbore hole. A printed wiring board that has another chip component mounted on it and is electrically connected to the surface circuit pattern.