JPS5956793A - Method of forming nonpenetrating signal via hole - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention relates to a multilayer printed wiring board, and more particularly to a method for forming non-penetrating signal via holes.

Prior art multilayer printed circuit board Mat2:b-(,h), the signal connection between no is made through the via hole.If the mounting density is low, the signal via hole is formed by penetrating the top and bottom of the multilayer printed wiring board. However, with such a through hole, only one set of interlayer signal connections can be made.
As the packaging density increases, the number of signal via holes increases and the installation space becomes insufficient. Furthermore, wiring patterns in layers that are not connected through signal via holes must be run to avoid the signal via holes, and as the number of signal via holes increases, the area that can be effectively used for wiring decreases. In this way, the presence of through-holes is an important factor in increasing the density of multilayer printed wiring boards.
This has become a major bottleneck.

As a means of solving such problems, non-penetrating signal passage holes have been introduced2. If it is a non-penetrating signal via hole, two sets of 1-open signal connections can be made at the same location, the number of via holes can be halved, and this greatly contributes to higher density.

However, the non-penetrating signal via hole is more difficult to form than the penetrating signal via hole, and the improvement is poor, with a +% decline.

A conventional method for forming a non-penetrating signal via hole will be explained with reference to FIG.

FIG. 1 is a cross-sectional view showing a part of a conventional six-layer printed wiring board having non-penetrating signal via holes. Same figure (two points,
1 is a base material made of an insulator of each type.

After forming the wiring pattern 3, these eight base materials 1 are laminated in a sandwich shape with a prepreg (layer of insulating adhesive) 2 interposed therebetween and are bonded together. 4 is a through-signal via hole (-! or component mounting hole) that passes through the top and bottom (two holes). Formed by plating.

The hole 6 is a non-penetrating signal via hole. The non-penetrating signal via holes 5 and 6 are formed by drilling holes of a depth corresponding to the layers to which signals are to be connected from the upper and lower surfaces of the printed wiring board, and plating the inner surface of each hole.

Since the depth of the holes for forming the non-penetrating signal via holes 5 and 6 requires a high level of precision, the drilling process is extremely inefficient and requires expensive machinery. In addition, there are problems such as an increase in the number of man-hours for management and a decrease in step Vlip.

For this reason, there was a drawback that the multilayer printed wiring board became expensive.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an improved method for forming non-through signal via holes in a multilayer printed wiring board.

According to the present invention, through holes are first formed in the upper and lower surfaces of the multilayer printed wiring board. Next, an insulator member (separator) is inserted halfway into this through hole, and the through hole is substantially defined by the separator into two upper and lower non-through holes. and,
The inner surface of this non-penetrating hole is plated to form a non-penetrating signal via hole.

Embodiment of the Invention FIG. 2 is a partial cross-sectional view of an example of a six-layer printed wiring board in which non-penetrating signal via holes are formed according to the present invention. 2 in this figure, numerals 1, 2.8 are the same as the parts with the same numerals in FIG.

10 is a non-penetrating signal via hole for signal connection between the top layer and the second additional wiring pattern 81'J, and 11 is a fifth hole.
This is a non-penetrating signal via hole for making a signal connection between the layer and the wiring pattern 8 on the lowest layer. The pair of non-penetrating signal via holes 10.11 are formed by the following procedure.

First, the non-penetrating signal via hole 10. At the position where Ili is to be formed, a through hole 13 that vertically penetrates the 61-printed wiring board is formed.
to be drilled. This hole can be easily drilled using the same method as for forming a conventional through hole for forming a component attachment hole or a through hole for passing a signal.

Next, a separator 14 made of an insulating material such as cork or Branutik is inserted into the through hole 13 (to the required depth). Defined as a non-through hole.

(At Q, plating is performed from the upper surface side 9 and the lower surface side (
-1. Plated films 15 and 16 of conductive metal are formed inwardly of the upper and lower non-through holes defined by the separator 14.

This forms the non-penetrating signal via hole 1.0.11.

The length of the separator 14 and its insertion depth are appropriately determined depending on the position of the node to be connected. In this embodiment, male signals are connected between the top layer and the second layer, and between the fifth layer and the bottom layer. Therefore, the separator 14 is inserted to a depth such that the upper surface of the separator 14 is located below the second layer by a small distance.

After inserting the separator J4 to that depth, the length of the separator J4 is determined so that the lower surface of the separator 14 is positioned above the fifth layer by a slight distance, and the cuff is assembled. Said short distance''
is set to a value that ensures that the signal connection with the desired layer is not made due to errors in the insertion depth and length of the separator 14, and the signal connection is not made with an inappropriate layer. decide.

Effects of the Invention As mentioned above, 1, 4 [the invention] inserts an insulator member (separator) into a through hole, thereby defining the through hole into two upper and lower non-through holes. is much easier than directly forming non-through holes as in the past.
It can be carried out with good yield.

According to the present invention, it is possible to reduce the manufacturing cost of a multilayer printing distribution board with a low number, L1, and high visibility, including the cost of forming non-penetrating signal via holes.

[Brief explanation of the drawing]

Figure 1 is a partial FfT view of a conventional 6-layer printed wiring board;
The figure is a partial I@ side view of a 6-layer printed wiring board according to the present invention (2). ■... Base material, 2... Prepreg, 8... Wiring pattern, 10, 11... Non-penetrating signal Via hole, 13...
Through hole, 14... Serial L/-ta, 15. 16...
Plating film.

Claims (1)

[Claims] (1) In a multilayer wiring board, a through hole is bored that penetrates from the upper surface to the lower surface, and an insulating material member is inserted halfway into the through hole to define the through hole into two vertically non-through holes,
A method for forming a non-penetrating signal via hole, comprising forming a non-penetrating signal via hole by plating the inner surface of the non-penetrating hole.