JPH0542158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer printed wiring board and a method for manufacturing the same, and more particularly to a high-density multilayer printed wiring board in which a through-hole conductor layer has divided through-holes in some parts. .

[Conventional technology]

In conventional printed wiring boards, not only holes for inserting components but also via holes are formed by drilling through holes and providing a conductive layer on the hole wall by means such as electroless plating. It is true.

Additionally, as multilayer printed wiring boards (hereinafter abbreviated as multilayer boards) become more multilayered, designs in which embedded via holes (inner layer via holes) are provided in some of the inner layers are also being adopted.

In recent years, attempts have been made to increase the packaging density of electronic devices due to performance and economical needs. For this reason, not only are electronic devices such as ICs and LSIs becoming more highly integrated and faster, but printed wiring boards on which these devices are mounted are also becoming more dense.

Two attempts have been made to increase the density of printed wiring boards. That is, the first attempt was to increase the number of conductor layers, increasing the number of layers.
The second attempt is to pass many wires between the grid patterns. However, the first attempt results in an increase in via holes connecting the interlayer conductor layers. Particularly, when the via hole 5 is provided as a through hole in the printed wiring board as shown in FIG. 2, the wiring performance of the above-mentioned second attempt is significantly impaired. This has been addressed by reducing the diameter of the via hole 5, but as the number of layers increases, the thickness of the plate also increases, and the ratio of plate thickness/hole diameter (aspect ratio) increases.
This significantly impedes the productivity of printed wiring boards. In addition, in fields that require ultra-high density, multi-layers of 10 or more are used, and so-called buried via holes with via holes in the inner layers are used.
Although it was satisfactory in terms of performance, it did not satisfy all needs economically.

Furthermore, there is a need to solve the above-mentioned problems in multilayer boards, especially in multilayer boards with 5 to 10 layers, whose demand is expected to increase in office automation equipment (OA equipment) and the like.

As an attempt to achieve this goal, “Making”
100000 Circuits Fastest Where Most
6000 Foot Bifor (Making100000 Circuits
fit where at most 6000 fit before;
Electronic, August 2, 1979)" The blind via hole shown in FIG. 3C, that is, the non-through hole improves the ability to accommodate wiring.

[Problem that the invention seeks to solve]

However, from a manufacturing perspective, “Lasers in Electronics”
Circuit Manufacturing, July, 1981)” or “Copper Plating Advanced
Mutltilayer Boards; IPC, Fall 1976
Blind buyer holes 5-- as shown in FIG. 3-C are formed in the multilayer board 1 as shown in FIG.
This involves the inefficiency of drilling holes 1 and 5-2 on each side.

Furthermore, in laser drilling, as shown in FIG. 3B, after etching and removing the outermost copper foil at the position P-2 where the via hole is to be drilled in the multilayer board 1,
This method has the disadvantage that the number of steps increases because a via hole is drilled.

In addition, after drilling a via hole, a conductive layer is formed on the entire surface including the inner wall by electroless plating.
Between the outermost insulation layers 1a-1 and 1a-2 in Figure 3D
If it is thick, it is difficult to form a uniform conductor layer, which is unfavorable in terms of reliability.

An object of the present invention is to provide a multilayer printed wiring and a method for manufacturing the same, which eliminates such drawbacks in manufacturing conventional multilayer boards.

[Means for solving problems]

According to the present invention, a set of insulating substrates with conductor circuit patterns provided on both the front and back surfaces is placed on the outermost side, a prepreg layer is placed on the inside of the insulating substrates, and a prepreg layer is placed on the inside of the insulating substrates, and the front and back conductors of the multilayer printed wiring board are further placed on the inside. A hydrophobic insulating film with a hole hollowed out in a concentric circle larger than the diameter of the through hole is placed at the position of the general through hole, and heated and pressurized to form a hole in the hydrophobic insulating film. forming a multilayered substrate by filling the portion with resin that has flowed out from the prepreg layer; and providing a through hole for front and back conduction in the multilayered substrate;
a step of drilling a through hole for connecting an inner layer circuit pattern; a step of immersing the multilayer substrate in a liquid that has a catalytic action for electroless plating to activate the catalyst; A step of providing a certain clearance at the position of the through hole and depositing a permanent mask layer having insulating properties on a desired portion; and electroless plating of the multilayer substrate to expose the permanent mask layer on both the front and back surfaces. A multilayer printed wiring board comprising: the inner wall of the through hole for front and back conduction; and the step of forming a conductive layer on the inner wall excluding the exposed wall surface of the hydrophobic film on the inner wall of the through hole for connecting the inner layer circuit pattern. A manufacturing method is obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1F shows a multilayer board obtained according to this example, in which the via holes (through holes) 5 are filled with insulating substrates 1a-1, 1a-
2 and the prepreg layer 1b are vertically separated by a hydrophobic insulating film (for example, tetrafluoroethylene resin film, etc.) 3, and the conductor layer is removed in a ring shape to form conductor layers 7-1 and 7-2. The structure is as follows.

Next, the method for manufacturing the multilayer board of the present invention will be explained in detail with reference to FIGS. 1A to 1F.

FIG. 1A shows a laminated structure, with 1-2 layers of a multilayer board having a desired circuit pattern formed on both the front and back surfaces of the glass cloth base epoxy resin laminates 1a-1 and 1a-2 by a known printing/etching method. (1a-1)
and 3-4 layers (1a-2) are arranged on the outermost side, prepreg layers 1b-1 and 1b-2 are arranged on the inner side, and holes 6 for inserting parts of the multilayer board are bored inside. A hydrophobic ethylene tetrafluoride resin film 3 having a concentric hole larger than the diameter of the hole 6 for inserting the component is combined at the desired position P-1, and integrally molded by heating and pressurizing. A multilayer laminate 1 is obtained (FIG. 1B).

Next, a through hole 6 for inserting the component and a through hole 5 for connecting the inner layer are drilled (FIG. 1C).

Next, in order to make the through holes 5 and 6 conductive, a catalyst such as palladium is adsorbed onto the inner walls of the through holes 5 and 6 and the surface of the multilayer laminate 1 to form a catalyst layer 10. Since only the end face of the tetrafluoroethylene resin film is hydrophobic, no catalyst layer 10 is formed (FIG. 1D).

Next, a permanent mask layer 4 having insulating properties and chemical resistance is deposited on desired portions so that unnecessary conductor layers are not formed on the surface of the laminate 1 (FIG. 1E).

Next, when electroless copper plating is applied to the entire surface, the catalyst layer 10 on the exposed conductor layer and on the inner walls of the through holes 5 and 6
A copper-plated conductor layer 7 is formed in the through hole 5, and the copper-plated conductor layer 7 connects layers 1-2 by the tetrafluoroethylene resin film 3, especially in the through hole 5.
A multilayer printed wiring board of the present invention is obtained in which 7-2 is connected to 3-4 (FIG. 1F).

〔Effect of the invention〕

As explained above, according to the present invention, productivity can be significantly improved since holes can be formed without using special means such as a laser or conventional means that are not suitable for mass production, such as forming non-through holes one surface at a time. Furthermore, the reliability of inner layer connections can be improved, and high-density multilayer printed wiring with significantly improved wiring capacity can be obtained.

[Brief explanation of the drawing]

Figures 1A, B, C, D, E, and F are sectional views showing the positional embodiment of the present invention in the order of steps, Figure 2 is a sectional view of one of the conventional examples, and Figure 3 A, B, C, and D. FIG. 2 is a sectional view showing another conventional example in the order of steps. 1... Multilayered laminate, 1a-1... A laminate forming 1-2 layers, 1a-2... A laminate forming 3-4 layers, 1b, 1b-1, 1b-2... Prepreg Layers, 2-1 to 2-4... conductor patterns of 1 to 4 layers, 3... hydrophobic insulating film, 4...
...Permanent mask layer, 5,6...Through hole, 5-1,5
-2...Blind via hole connecting layers 1-2 and 5-6, 7, 7-1, 7-2...
Copper-plated conductor layer by electroless copper plating, 10...
Catalyst layer, P-1...Position where a through hole for component insertion is formed, P-2...Position where a via hole is formed.

Claims (1)

[Claims] 1. A set of insulating substrates on which conductive circuit patterns are provided on both the front and back sides is placed on the outermost side, a prepreg layer is placed on the inside of the insulating substrates, and further inside the set, the front and back sides of a multilayer printed wiring board are placed in advance. At the location of the through hole for continuity,
A hydrophobic insulating film having a hole hollowed out in a concentric circle larger than the diameter of the through hole was placed, and heated and pressurized to cause the hollowed out hole part of the hydrophobic insulating film to flow out from the prepreg layer. a step of filling with resin to form a multilayered substrate; providing the through-hole for front and back conduction in the multilayered substrate;
a step of drilling a through hole for connecting an inner layer circuit pattern; a step of immersing the multilayer substrate in a liquid that has a catalytic action for electroless plating to activate the catalyst; A step of providing a certain clearance at the position of the through hole and depositing a permanent mask layer having insulating properties on a desired portion; and electroless plating of the multilayer substrate to expose the permanent mask layer on both the front and back surfaces. A multilayer printed wiring board comprising: the inner wall of the through hole for front and back conduction; and the step of forming a conductive layer on the inner wall excluding the exposed wall surface of the hydrophobic film on the inner wall of the through hole for connecting the inner layer circuit pattern. manufacturing method.