Circuit board for mounting electronic parts

Abstract

A board for mounting electronic circuit parts includes a first connection terminal group including a plurality of connection terminals densely formed on the top surface of a substrate having through holes formed therein, and a second connection terminal group including a plurality of connection terminals formed at at least the peripheral portion of a back surface of the substrate. The first connection terminal group is connected to the second connection terminal group by way of the through holes. A build-up multilayer interconnection layer having via holes is formed on the top surface of the substrate, so that the first connection terminal group is connected to the second connection terminal group through the build-up multilayer interconnection layer and the through holes. According to another aspect, each signal line on the top surface of the build-up multilayer interconnection layer comprises a plurality of wiring patterns having different widths and a taper-shaped pattern that connects those wiring patterns together and whose width continuously changes. Each signal line has a smaller width at an area having a relatively high wiring density than at an area having a relatively low wiring density.

Description

[0001]This appln is a cont of PCT / JP96 / 02608 filed Sep. 12, 1996 and a cont of Ser. No. 09 / 068,481 filed May 11, 1998 abn.TECHNICAL FIELD[0002]The present invention relates to a board that has connection terminals formed on both the top and back surfaces thereof and on which electronic circuit parts are to be mounted.BACKGROUND ART[0003]A wiring board 21 for mounting electronic circuit parts, as shown in FIG. 8, for example, is known as one conventional printed circuit board for mounting a bare chip like a flip chip or a package like a BGA (Bump Grid Array).[0004]This type of wiring board 21 has a substrate 22 that has conductor layers formed on both the top and back surfaces by mainly a subtractive method. A parts mounting area is provided in the center of the top surface of the substrate 22. Formed densely in this area are multiple pads 23 which constitute a first pad group. The individual pads 23 correspond to bumps BP positioned on the bottom of a bare chip C1.[0005]Multiple pad...

AI Technical Summary

Benefits of technology

The present invention improves wiring efficiency while avoiding enlarging the entire board and avoiding an increase in wiring resistance or cracks in a permanent resist. By densely forming connection terminals and utilizing via holes and through holes, wires can be shortened and the efficiency of the wiring pattern improved. Signal lines are designed with narrow widths in high wiring density areas and wide widths in low wiring density areas to prevent line disconnection and secure insulation between patterns. The use of taper-shaped patterns also ensures insulation between signal lines without causing cracks in the permanent resist and wiring resistance is not increased. Overall, this invention increases processing speed and device performance.

Problems solved by technology

The wires for connecting the pads 23 to the pads 24 therefore are longer than necessary, resulting in a poor wiring efficiency.

The use of this wiring board 21 makes it difficult to increase the speed of signal transmission between electronic circuit parts to be mounted and the mother board.

In this case, however, dead space where wiring is not possible is formed in the portion where the through holes 26 are formed.

Thus, to secure wiring space, the board itself would inevitably become larger.

This reduces the reliability of the wiring board 60.

Stress is apt to concentrate on those corners, which raises another problem that cracks 64 are easily formed in a permanent resist 63 near the corners as shown in FIG. 10.

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