JPH06302959A - Method for manufacturing multilayer printed wiring board - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a multilayer printed wiring board that exhibits excellent physical and electrical characteristics through a blind via hole and an access-like through via hole and is suitable for mass production. [Structure] A circular hole is previously removed by etching from a portion of a double-sided plate inner layer land 4 where a through-hole is formed, and then a copper clad insulating sheet is adhered to both surfaces of the inner layer plate 1 to form a multilayer plate. Then, the land portion of the multilayer board is removed by etching to form a hole, and the insulating layer exposed at that portion is dissolved and removed with an alkaline aqueous solution to expose the inner layer lands 4 and 5. A multilayer printed wiring board is completed by making a hole in the inner layer substrate 1 with a drill having a diameter smaller than the inner diameter of the inner layer land 4 in which the circular hole is removed by etching in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board, and in particular, it has excellent electrical connectivity and
The present invention relates to a manufacturing method suitable for mass production.

[0002]

2. Description of the Related Art A conventional method for manufacturing a multilayer printed wiring board will be described by taking a four-layer board as an example, as shown in FIG.
Circuits 55 are formed on both sides of the double-sided copper clad laminate to form the inner layer board 51.
In order to improve the adhesion of the prepreg 52 to the inner layer plate 51, after blackening the surface of the inner layer plate 51,
The copper foils 53 are laid on both sides of the prepreg 52 through a few sheets.

After that, pressure is applied under vacuum in a hot press to laminate and cure, thereby forming a four-layer laminate as shown in FIG.

A four-layer laminated plate is formed by drilling through holes 56 as shown in FIG. 10 and plating the inside of the holes 56 by panel plating, so that as shown in FIG. Are electrically connected via the plated layer 57. After that, the circuit 57 is formed on the outer layer board to complete the four-layer laminated board.

As another example of the method for manufacturing a multilayer printed wiring board, after forming circuits on both sides of an inner layer board, a copper clad insulating sheet is adhered to the inner layer board without forming a drill hole to form an outer layer, It is also possible to drill access-type through via holes and blind via holes from each side of the outer layer with a drill. It is also conceivable to process the through holes in advance and laminate the same insulating sheet on both sides by using an inner layer board having circuits formed on both sides.

[0006]

However, when holes are drilled from the outer layer side after forming the multilayer plate without forming holes in the lands of the inner layer plate, burrs are generated in the inner layer land portion. Further, when the outer layer plate is formed by drilling the inner layer plate in advance, the resin layer on the outer layer plate side will enter the hole when the outer layer is brought into close contact. And if you try to dissolve and remove the resin that has entered the hole,
The resin on the outer layer side is excessively dissolved and removed, and there is a drawback that insulation cannot be obtained.

When a conductive pattern is formed on the inner layer board and a copper clad insulating sheet is laminated without forming through holes,
Since the copper-clad insulating sheet has an interval corresponding to its thickness, burrs are formed in the through holes of the inner-layer copper foil land when drilling holes from the outer layer surface thereafter. Also,
The productivity of drilling holes is low.

It is difficult to remove the flash, and if the conductive paste or plating is applied to the part without removing the flash, cracks may be generated after the process is completed, which may cause disconnection. There's a problem.

Therefore, the present invention has been made in consideration of the above circumstances, and exhibits excellent physical and electrical characteristics through a blind via hole and an access-like through via hole, and is suitable for mass production. Another object of the present invention is to provide a method for manufacturing a multilayer printed wiring board.

[0010]

In order to achieve the above object, the present invention provides a multilayer printed wiring board obtained by laminating a copper clad insulating sheet on one or both sides of an inner layer board having a circuit formed on one or both sides. , Forming a conductor pattern on the inner layer board in advance and etching away the copper foil in the portion where the through via hole is formed with a required hole diameter,
Then, a copper clad insulating sheet is laminated on the surface of the inner layer plate to form the outer layer plate.

Next, the copper foil is selectively removed by etching with a required hole diameter at the portion where the through via hole and the blind via hole of the outer layer plate are formed, and the copper foil is positioned under the portion where the copper foil is removed. The circular land of the inner layer plate is exposed by dissolving and removing the insulating resin layer with an alkaline aqueous solution, and then the insulating resin layer is cured.

After the conductor pattern is formed on the outer layer, the exposed portion of the inner layer plate on which the through via holes are to be formed,
Drill a hole with a drill smaller than the hole diameter of the preformed copper foil. Then, a solder resist is applied except the electrically connected portions of the conductor pattern.

The through via holes and the blind via holes are filled with a conductive paste and cured. Finally, an overcoat for protecting the surface of the multilayer printed wiring board is applied to complete the multilayer printed wiring board.

The copper clad insulating sheet has an insulating resin layer soluble in an alkaline aqueous solution formed on the copper foil surface, and the inner diameter of the land of the through via hole is larger on the outer layer side than on the inner layer side. However, the outer shape of the inner layer land is formed larger than the inner diameter of the outer layer land.

[0014]

According to the method of manufacturing a multilayer printed wiring board of the present invention, since the copper clad insulating sheet having the insulating resin layer soluble in the alkaline aqueous solution formed on the copper foil surface is used as the outer layer board, the access-like through via hole is formed. The blind via hole can be processed by chemically dissolving and removing it without using a drill when processing the blind via hole from the outer layer side. The undercut on the back surface of the land when the insulating resin layer is melted is minute. Also, because of chemical dissolution, all holes can be processed at the same time.

At the position of the through-via hole, holes are formed in advance only on the copper foil portion of the inner layer plate by etching. Therefore, after forming the holes on the outer layer plate side, the holes on the inner layer plate that have been previously etched are formed. A hole with a diameter smaller than the hole diameter of the copper foil can be used to make holes in the inner layer board. Copper foil does not need to be drilled, so burrs do not occur.

Since the land inner diameter of the through via hole is larger on the outer layer side than on the inner layer side to increase the exposed area of the inner layer land, a wide connection area can be obtained not only by the conductive paste but also by plating. In addition, since the outer shape of the inner layer land is formed larger than the inner diameter of the outer layer land, the substrate surface on the inner layer side is not exposed when the insulating resin layer is dissolved and removed by the inner diameter of the outer layer side land. Therefore, in the case of a blind via hole, the entire bottom surface of the hole is the copper foil surface.

[0017]

1 to 7 show a manufacturing process in a method for manufacturing a multilayer printed wiring board according to the present invention. Hereinafter, the manufacturing steps will be described with reference to the drawings.

FIG. 1 shows an inner layer substrate 1 provided with copper foils on both sides, and FIG. 2 shows a copper pattern provided on both sides of the inner layer substrate 1 by etching to form conductor patterns 3 and lands 4 of access-type through via holes. In this state, the land 5 of the blind via hole is formed, and at this time, the hole 6 is formed in the central portion of the land 4 of the access through via hole by etching at the same time.

In FIG. 3, the insulating resin layer 9 side of the copper clad insulating sheet 7 having the insulating resin layer 9 formed on the surface of the copper foil 8 is applied to the front and back surfaces of the inner layer plate 1 shown in FIG. 1 shows a state in which a multi-layered plate constituted by the inner layer plate 1 and the outer layer plate 7 is formed by laminating at. The insulating resin layer 9 formed on the surface of the copper foil 8 is soluble in an alkaline aqueous solution.

FIG. 4 shows that holes 10 and 11 are formed in the copper foil 8 by selectively etching the portions of the copper foil 8 of the outer layer plate where the through via holes and the blind via holes 1 are formed. 1 shows a state in which the copper foil of the inner layer substrate 1 is exposed by chemically dissolving and removing a portion of the insulating resin layer 9 exposed by forming a hole in the copper foil 8 with an alkaline aqueous solution. After that, the insulating resin layer 9 is irradiated with an electron beam to be temporarily cured, and further treated at 160 ° C. for 25 minutes to be fully cured.

FIG. 5 shows a state in which a circuit is formed on the copper foil of the outer layer 7 by etching in a usual manner by etching.

FIG. 6 shows a hole 12 formed at the center of the inner-layer land 4 exposed in the previous step in the access-type through via hole portion by using a drill having a diameter smaller than the diameter of the hole 6 pre-etched. The processed state is shown. in this case,
Since the diameter of the land 4 is smaller than the hole diameter, the land 4 need not be drilled. Therefore, burrs do not occur on the inner diameter of the land 4.

Incidentally, the diameter of the blind via hole 11 is 0.5 mm, the diameter of the through via hole 10 is 0.8 mm, the hole diameter of the inner layer land 4 is 0.5 mm, and the through hole diameter of the substrate 1 is 0.4 mm. No burr was observed at all when processed in.

FIG. 7 shows an access type through via hole 1.
0 and the blind via hole 11 are coated with solder resist 15, and the required lands 4, 5, 1 of each layer are formed.
3 shows a state in which a multilayer printed wiring board is completed by filling conductive paste 16 into 3 and 14 and electrically connecting them. In this case, the conductive paste was filled and then treated at 160 ° C. for 20 minutes to be cured.

In the above process, the inner diameters of the lands of the access-like through via holes 10 and the blind via holes 11 are formed larger on the outer layer side than on the inner layer side. Secures the physical connection.

Since the outer shape of the inner layer land is larger than the inner diameter of the outer layer land, the inner layer substrate 1 is not exposed when the insulating resin layer 9 is dissolved and removed.

[0027]

As described above, according to the method for manufacturing a multilayer printed wiring board of the present invention, all the holes are simultaneously removed by chemical dissolution and removal without using a drill until the process of processing blind via holes. Since it can be formed, mass productivity is improved.

Further, since the holes in the inner layer lands of the access-like through via holes are formed by etching before lamination, they do not need to be drilled, so that burrs do not occur. This improves the conductivity and prevents the land from cracking.

Since the land inner diameter of the through via hole is larger on the outer layer side than on the inner layer side, the exposed area of the inner layer land is large, and electrical connection is ensured not only in the conductive paste but also in plating. Physical,
It is possible to exhibit excellent electric characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a multilayer printed wiring board according to the present invention.

FIG. 2 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 4 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 5 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 6 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 7 is a diagram showing a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 8 is a diagram showing a manufacturing process of a conventional multilayer printed wiring board.

FIG. 9 is a diagram showing a manufacturing process of a conventional multilayer printed wiring board.

FIG. 10 is a diagram showing a manufacturing process of a conventional multilayer printed wiring board.

FIG. 11 is a diagram showing a manufacturing process of a conventional multilayer printed wiring board.

[Explanation of symbols]

 1 inner layer board 2,8 copper foil 3 conductor pattern 4,5,13,14 land 6 land hole 7 outer layer board 9 insulating resin layer 10 access through via hole 11 blind via hole 12 drill hole 15 solder resist 16 conductive paste

Claims (3)

[Claims] 1. A multilayer printed wiring board obtained by laminating a copper clad insulating sheet on one side or both sides of an inner layer board having a circuit formed on one side or both sides, wherein a conductor pattern is formed on the inner layer board in advance and a through via hole is formed. The step of etching away the copper foil of the portion to be formed with a required hole diameter, the step of laminating a copper clad insulating sheet on the surface of the inner layer board to form the outer layer board, and the through via hole of the outer layer board and The process of selectively removing the copper foil by etching with a required hole diameter in the portion where the blind via hole is formed, and the insulating resin layer located below the copper foil removed portion is dissolved and removed with an alkaline aqueous solution. To expose the circular lands of the inner layer board, and then to cure the insulating resin layer, to form a conductor pattern on the outer layer, and to form the inner layer board. A step of forming a hole in the board portion where the through via hole is formed with a drill having a diameter smaller than the hole diameter of the copper foil formed in advance; and a step of applying a solder resist except for a portion electrically connected by a conductor pattern, A method for manufacturing a multilayer printed wiring board, comprising: a step of filling a conductive paste into a through via hole and a blind via hole and curing; and a step of applying an overcoat for protecting the surface of the multilayer printed wiring board. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the copper-clad insulating sheet has a copper foil surface on which an insulating resin layer soluble in an alkaline aqueous solution is formed. 3. The multilayer printed wiring according to claim 1, wherein the land inside diameter of the through via hole is formed larger on the outer layer side than on the inner layer side, and the outer diameter of the inner layer land is formed larger than the inner diameter of the outer layer land. Method of manufacturing a plate.