JPH05110259A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a multilayer printed wiring board having high density and having the excellent reliability of the connection of an inter-layer circuit conductor layer while having the superior performance of an inter-layer insulating layer by solving the controversial point of the reliability of the electrical connection of the inter-layer wiring circuit conductor layer in the multilayer printed wiring board used for various electronic equipments. CONSTITUTION:Projecting conductor layers 8 are formed at specified positions, where first wiring circuit conductor layers 7 shaped onto the main surface of an insulating substrate 6 must be connected, an insulating resin layer 9 is constituted to the first wiring circuit conductor layers 7 and part of the conductor layers 8 are exposed onto the surface of the layer 9, and second wiring circuit conductor layers 10 are formed onto the surface of the layer 9 in a multilayer printed wiring board, and the first and second wiring circuit conductor layers 7, 10 are interconnected electrically through the projecting conductor layers 8 exposed onto the surface of the insulating resin layer 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board used in a wide variety of electronic devices and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the demand for multilayer printed wiring boards has increased remarkably as the needs for miniaturization, weight reduction and higher performance of electronic equipment have increased.

A conventional multilayer printed wiring board is manufactured by various methods, and a typical example thereof is shown in FIG.
There is a manufacturing method by a build-up method as shown in.

In FIG. 3, 1 is an insulating substrate, 2 is a first wiring circuit conductor layer, 3 is an insulating resin layer between layers, 4 is a fine hole (blind hole) provided in the insulating resin layer, and 5 is a second hole. It is a wiring circuit conductor layer.

The multilayer printed wiring board having the above-mentioned structure uses a so-called copper-clad laminate in which a metal copper foil is bonded to the entire surface of a synthetic resin type insulating substrate 1 usually made of glass epoxy resin or the like, and a photoetching method or the like is used. A first wiring circuit conductor layer 2 made of a metal copper foil is formed on the main surface of the insulating substrate 1 by a known method, and, for example, a photosensitive epoxy resin is applied as the insulating resin layer 3 on the surface thereof. Ultraviolet rays are radiated to necessary positions of the insulating resin layer 3 to form fine holes, that is, blind holes 4, in the insulating resin layer 3 so that a part of the first wiring circuit conductor layer 2 is exposed. After the surface layer of the insulating resin layer 3 is chemically roughened, electroless copper plating and electrolytic copper plating are used together on the entire surface to form a conductive metal layer made of metallic copper, and then a photoetching method or the like is performed. The desired second wiring circuit conductor layer 5 is formed on the main surface of the insulating resin layer 3 by the above-mentioned known method. At the same time, the blind hole 4 provided in the insulating resin layer 3 is made conductive to electrically connect the wiring circuit conductor layers 2 and 5 between the layers.

[0006]

However, in such a multilayer printed wiring board according to the conventional example, the electrical connection between the wiring circuit conductor layers between layers is conducted through the blind hole 4 which is not penetrated provided in the insulating resin layer 3 between layers. In such a connection structure, it is extremely difficult to deposit copper in the blind hole 4 of a fine diameter that does not penetrate to make it conductive in this connection structure. However, there is a problem in that the electrical connection failure between the wiring circuit conductor layers 2 and 5 between layers is likely to occur and the reliability of the connection is lacking.

Further, in the conventional multilayer printed wiring board, the insulating resin material used for forming the insulating resin layer 3 between layers is generally an ultraviolet curable resin, but the ultraviolet curable insulating resin is usually an electric resin. In addition to insulating properties, heat resistance, and chemical resistance, the adhesiveness to electroless copper-plated metal is particularly poor, so that it has been difficult to improve the performance of a multilayer printed wiring board.

Furthermore, in the multilayer printed wiring board according to the conventional example, since the interlayer connection portion is formed by the fine hole, that is, the blind hole 4 provided in the insulating resin layer 3, the conductor layer of the connection portion requires a relatively large area. However, this has a problem that it hinders high density of the wiring circuit.

The multi-layer printed wiring board according to the present invention solves the above-mentioned problems of the conventional example and improves the reliability of the electrical connection between the wiring circuit conductor layers between the layers, and the high density of the interlayer insulating layers is excellent. It is intended to provide a multilayer printed wiring board.

[0010]

In order to achieve the above object, a multilayer printed wiring board according to the present invention comprises a desired first printed circuit conductor layer provided on at least one main surface of an insulating substrate, A projecting conductor layer locally formed at a predetermined position of the first wiring circuit conductor layer and the entire surface of the first wiring circuit conductor layer and exposing a part of the projecting conductor layer. And the second wiring circuit conductor layer formed on the main surface of the insulating resin layer so as to electrically connect the first wiring circuit conductor layer through the projecting conductor layer. And a wiring circuit conductor layer.

[0011]

According to the present invention, the wiring circuit conductor layers between the layers are electrically connected to each other by the conductor layers which are two-dimensionally exposed on the surface of the insulating resin layer between the layers. The electrical connection between the wiring circuit conductor layers is stabilized, and the connection reliability is improved. Further, since it is not necessary to use a photosensitive resin as the interlayer insulating resin material, a wide range of insulating resin materials having excellent performance can be selectively used, and high performance of the multilayer printed wiring board can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multilayer printed wiring board according to an embodiment of the present invention and a method of manufacturing the same will be described below with reference to the drawings. FIG. 1 is a sectional view of an essential part of a multilayer printed wiring board for explaining a first embodiment of the present invention. In FIG. 1, 6
Is an insulating substrate, 7 is a first wiring circuit conductor layer, 8 is a protruding conductor layer, 9 is an insulating resin layer between layers, and 10 is a second wiring circuit conductor layer.

The multilayer printed wiring board having the above structure is manufactured through the manufacturing steps shown in FIGS.

In this embodiment, first, as shown in FIG. 2A, a so-called copper-clad laminated substrate in which a metallic copper foil is adhered to the entire surface of a synthetic resin type insulating substrate 6 such as a glass epoxy laminated plate is used as a starting material for photoetching. A desired first wiring circuit conductor layer 7 is formed on the main surface of the insulating substrate 6 by a known method such as a method, and the first wiring circuit conductor layer 7 is projected at a predetermined position where connection is required. The conductor layer 8 having a strip shape was locally formed.

In this case, various methods are conceivable as a method of forming the protruding conductor layer 8 formed at the position where the connection of the first wiring circuit conductor layer 7 is required. In this embodiment, gold is used. Wire, copper wire, etc., thermal compression welding method, plating method, method using conductive resin, and further, cylindrical metal wire having conductivity is formed by conductive resin into the first wiring circuit conductor layer. I tried to fix it to 7.

These methods will be described in detail below.
First, regarding the heat pressure welding method of the metal wire, for example, the first wiring circuit conductor layer 7 formed on the main surface of the insulating substrate 6 is formed by the same principle as the wire bonding method known as a connection method of a semiconductor IC chip and a lead frame. The tip of a metal wire such as a gold wire or a copper wire is heated to a high temperature at a predetermined position requiring connection to form a ball, and the metal ball is pressed into contact with a predetermined position of the first wiring circuit conductor layer 7 to project. The conductor layer 8 having a shape of a circle was formed.

On the other hand, as another method of forming the protruding conductor layer 8, a plating method was tried in another embodiment.

As a method of forming the protruding conductor layer 8 by this plating method, first, the electroless copper plating method or the like is applied to the first wiring circuit conductor layer 7 formed on the main surface of the insulating substrate 6 made of a glass epoxy laminate. To form a thin conductor layer on the whole surface, and apply a photoresist to this surface to provide an opening portion in the resist layer so that a part of the first wiring circuit conductor layer 7 requiring connection is exposed, Then, electrolytic copper plating is performed to thicken metallic copper on the exposed first wiring circuit conductor layer 7, and if necessary, a metal having corrosion resistance to copper may be formed on the surface of the thickened metallic copper, for example. A different metal such as gold, silver, palladium, nickel, solder or tin is plated to coat the metal copper layer, and then the resist layer is peeled off to remove the exposed electroless copper plating thin layer by etching to remove the first layer. Wiring circuit conductor layer 7 Projecting conductor layer to the required position 8
Formed.

Further, as another embodiment of the method for forming the protruding conductor layer 8, a so-called conductive resin made into a paste by kneading fine powder of silver or copper with an epoxy resin is used in a dispenser or a metal mask. A method of forming the projecting conductor layer 8 by applying it to a predetermined position of the first wiring circuit conductor layer by a provided screen printing method and heating and curing, or a metal wire such as a copper wire having a relatively large wire diameter. Was processed into a cylindrical shape, and one end thereof was fixed with a conductive paste made of silver, copper, gold or the like at a predetermined position requiring connection of the first wiring circuit conductor layer.

It is not necessary to strictly define the thickness of any of the projecting conductor layers 8 described above, but in the present embodiment, the thickness of the projecting conductor layers 8 is in the range of 50 to 100 μm. did.

Then, as shown in FIG. 2B, a resin having an insulating property is applied to the entire surfaces of the projecting conductor layer 8 and the first wiring circuit conductor layer 7 formed in each of these embodiments, and this resin is applied. The insulating resin layer 9 was formed by curing. In this case, the insulating resin material not only has excellent electrical insulation characteristics, heat resistance, and chemical resistance, but also has excellent adhesion characteristics for electroless copper plating on its surface. In this embodiment, as an insulating resin satisfying such characteristics, an insulating resin obtained by modifying an epoxy resin cured with an acid anhydride or a copolymer of acrylonitrile and butadiene with an epoxy resin or a phenol resin is used. Further, these insulating resins were kneaded with an inorganic filler such as alumina, calcium carbonate or silica.

Then, the surface layer of the insulating resin layer 9 is lightly ground by a sand blast method or the like, and the protruding conductor layer 8 for connection formed at a predetermined position of the first wiring circuit conductor layer 7 is formed on the surface thereof. A part of the insulating resin layer 9 was exposed, and the surface of the insulating resin layer 9 was immersed in a solution of manganese dioxide or potassium dichromate and lightly etched to roughen it.

Thereafter, the surface-treated substrate is dipped in an activation treatment liquid containing a hydrochloric acid acidic solution of tin chloride and palladium chloride, and the surface of the insulating resin layer 9 is coated with metallic palladium serving as a catalyst nucleus for electroless copper plating. After depositing the fine particles, the substrate is immersed in an electroless copper plating solution of pH 12 to 13 consisting of an alkaline solution of copper complex salt and formalin to deposit a thin layer of metallic copper on the entire surface, and if necessary, this electroless copper plating solution is deposited. After electrolytic copper plating is applied to the surface of the copper-plated layer to thicken the metallic copper, it is finally formed on the main surface of the insulating resin layer 9 by a known method such as a photoetching method as shown in FIG. 2C. To form a second wired circuit conductor layer 10
A multilayer printed wiring board was produced in which the second wiring circuit conductor layers 7 and 10 were electrically interconnected by the protruding conductor layers 8 exposed on the surface of the insulating resin layer 9.

In the multilayer printed wiring board obtained by such a method, the inter-layer wiring circuit conductor layers are electrically interconnected by the projecting conductor layers which are planarly exposed on a part of the surface of the insulating resin layer 9. Not only can the connection of the interlayer conductor layers be made more reliable in the electroless copper plating method because of the configuration, but since the interlayer insulating resin does not require photosensitivity, a wide range of insulating resin materials can be selected, An insulating resin that has excellent electrical insulation properties, heat resistance, and chemical resistance, and that has excellent adhesion to electroless copper plating can be used, so that the performance of multilayer printed wiring boards can be improved. Is.

In this embodiment, synthetic resin such as a glass epoxy laminated plate is mainly used as the insulating substrate 6, but the insulating substrate 6 is not limited to the resin substrate, and alumina or low temperature sintered alumina glass ceramics is used. The insulating substrate 6 may be used, and the required first wiring circuit conductor layer 7 may be directly formed on the main surface thereof by the electroless copper plating method.

Further, in the present embodiment, the wiring circuit conductor layers are multi-layered only on one main surface of the insulating substrate 6, but the wiring circuit conductor layers are multi-layered on the front and back both sides of the insulating substrate 6 by the above-mentioned method. It goes without saying that the multilayer wiring circuit conductor layers on the front and back sides of the insulating substrate 6 may be those in which holes penetrating the insulating substrate are made conductive by through-hole plating.

[0027]

As described above, according to the multilayer printed wiring board of the present invention, the circuit conductor layer between layers can be more reliably provided as compared with the conventional method of connecting through the fine holes which do not penetrate the interlayer insulating layer. It is connected and its connection state is stabilized, and the reliability of the connection is remarkably improved, and since it is not necessary to use a photosensitive resin as the insulating resin material, the interlayer insulating resin material has heat resistance, chemical resistance, and electrical insulation. Since it is possible to select not only the characteristics but also the adhesion of electroless copper plating,
The performance of the multilayer printed wiring board will be improved.

On the other hand, the multi-layer printed wiring board according to the present invention has a structure in which the portions for connecting the wiring circuit conductor layers between layers do not have the recesses due to the blind holes and are connected smoothly, so that the accommodation capacity of the wiring circuit is increased. Along with
The feature is that the effective mounting area of the component in the component mounting is increased and the density of the entire electronic circuit is increased.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a multilayer printed wiring board according to an embodiment of the present invention.

2 (A) to (C) are cross-sectional views of manufacturing steps illustrating a method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of a conventional multilayer printed wiring board.

[Explanation of symbols]

 6 Insulating Substrate 7 First Wiring Circuit Conductor Layer 8 Protruding Conductor Layer 9 Insulating Resin Layer 10 Second Wiring Circuit Conductor Layer

Claims (6)

[Claims] 1. A desired first wiring circuit conductor layer provided on at least one main surface of an insulating substrate, and a protrusion-shaped locally formed at a predetermined position of the first wiring circuit conductor layer. A conductor layer, an insulating resin layer formed so as to cover the entire surface of the first wiring circuit conductor layer and expose a part of the projecting conductor layer, and the first surface on the main surface of the insulating resin layer. And a second printed circuit conductor layer formed so as to electrically interconnect the wired circuit conductor layer via the projecting conductor layer. 2. A desired first wiring circuit conductor layer is provided on at least one main surface of an insulating substrate, and a projecting conductor layer is formed at a predetermined position of the first wiring circuit conductor layer. After that, an insulating resin layer is provided on the entire surface of the wiring circuit conductor layer, and the surface of the insulating resin layer is ground to expose a part of the projecting conductor layer on the surface of the insulating resin layer. A method for manufacturing a multilayer printed wiring board, wherein a second wiring circuit conductor layer is provided on a main surface and is electrically connected to the first wiring circuit conductor layer via the projecting conductor layer. 3. The method for manufacturing a multilayer printed wiring board according to claim 2, wherein the protruding conductor layer is provided with a metal wire by a thermal compression bonding method. 4. The method for manufacturing a multilayer printed wiring board according to claim 2, wherein the protruding conductor layer is provided by a plating method. 5. The multilayer printed wiring board according to claim 1, wherein the protruding conductor layer is made of a conductive resin. 6. The multilayer structure according to claim 2, wherein the protruding conductor layer is provided by fixing one end of a cylindrical metal wire having conductivity to a predetermined position of the first wiring circuit conductor layer with a conductive resin. Manufacturing method of printed wiring board.