JPH08321666A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE: To realize a printed wiring board which is free from disconnection, high in reliability, and provided with an aluminum board that serves as a conductive path by a method wherein a copper circuit is connected to the aluminum board covered with a connection layer through the intermediary of a conductive path inside a through-hole and a second copper plating layer. CONSTITUTION: The surface of an aluminum board 1 is covered with a connection layer 6 composed of a zinc film 3, a first copper plating layer 5, and the like. The front 1a of the aluminum board 1 and the surface 6a of the connection layer 6 which covers the inside of a clearance hole 2 are subjected to a black oxide treatment, and an insulating layer 7 continuously connected to the aluminum board 1 through the intermediary of the treated connection layer 6 is provided. A through-hole 8 smaller than the clearance hole 2 in diameter and a copper circuit 9 formed on the surface 7a of the insulating layer 7 are provided. A second copper plating layer 10 is formed on the rear side 1b of the aluminum board 1, and a conductive path 11 is provided inside the through-hole 8 to connect the copper circuit 9 to the second copper plating layer 10. By this setup, the copper circuit 9 has a continuity part of large area to the aluminum board 1, so that it is hardly disconnected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board using an aluminum substrate as a conductive path and a method for manufacturing the same.

[0002]

2. Description of the Related Art A printed wiring board using an aluminum substrate is widely used in order to dissipate a large amount of heat generated from electronic parts. With the expansion of the range of use of printed wiring boards in recent years, printed wiring boards using the above-mentioned aluminum substrate as a conductive path for an earth circuit or the like are known. FIG. 3 shows a cross section of a printed wiring board using the aluminum substrate as a conductive path. An alumite layer 22 is formed on the surface of the aluminum substrate 21, and an insulating layer 23 formed by curing the prepreg is formed through the alumite layer 22. A through hole 24 is formed in the aluminum substrate 21 on which the insulating layer 23 is formed, and a zinc film 25 is formed on the inner wall of the aluminum substrate 21 exposed in the through hole 24. The zinc film 25 is formed by immersing the aluminum substrate 21 in a solution of dilute sulfuric acid and nitric acid and then immersing it in an alkaline solution containing zinc oxide. The copper circuit 26 formed on the outer surface 23a of the insulating layer 23 is connected to the conductive path 27 formed in the through hole 24, and the conductive path 27 is connected to the aluminum substrate 21 via the zinc film 25. . Usually, the conductive path 27 in the through hole 24 is formed by copper plating.

[0003]

However, since the zinc film 25 is very thin in the printed wiring board, the through hole 2
Due to the influence of cutting chips attached when opening 4,
The inside of the aluminum substrate 21 may not be sufficiently covered and a part may be exposed. When the aluminum substrate 21 and the copper of the conductive path 27 are in direct contact with each other, they react electrically and the copper plating is easily peeled off. Therefore, for example, when repeatedly subjected to thermal shock, disconnection is likely to occur, and sufficient reliability cannot be obtained.

The present invention has been made in view of the above facts, and it is an object of the present invention to provide a printed wiring board using an aluminum substrate as a conductive path, which is free from disconnection and has high reliability, and a manufacturing method thereof. To provide.

[0005]

A printed wiring board according to claim 1 of the present invention is a printed wiring board having an aluminum substrate 1 as a conductive path, the aluminum substrate 1 having a clearance hole 2 penetrating therethrough, and the above aluminum. A connection layer 6 that covers the surface of the substrate 1 and includes a zinc film 3, a nickel plating layer 4 and a first copper plating layer 5 from the inner layer, and a connection layer that covers the front surface side 1a of the aluminum substrate 1 and the clearance hole 2. The surface layer 6a of 6 is subjected to black oxide treatment, and is formed on the insulating layer 7 connected to the aluminum substrate 1 and the insulating layer 7 where the clearance hole 2 is located through the connecting layer 6 subjected to the black oxide treatment. Further, the through hole 8 having a smaller diameter than the clearance hole 2, the copper circuit 9 formed on the outer surface 7a of the insulating layer 7, and the rear surface side 1b of the aluminum substrate 1 are formed. 2 of the copper plating layer 1
0, and a conductive path 11 that connects the copper circuit 9 and the second copper plating layer 10 is provided in the through hole 8.

A method of manufacturing a printed wiring board according to a second aspect of the present invention is characterized in that a printed wiring board using the aluminum substrate 1 as a conductive path is manufactured by the following steps. In the above step, the aluminum substrate 1 having the clearance hole 2 penetrating is subjected to zinc substitution, nickel plating, and
A step of forming a connection layer 6 by copper plating, a step of subjecting the surface layer 6a of the connection layer 6 to a black oxide treatment,
The front side 1a of the aluminum substrate 1 and the clearance hole 2
A step of forming an insulating layer 7 formed by curing a resin therein, a step of exposing a copper oxide of the connection layer 6 by polishing a black oxide treated surface of the back surface side 1b of the aluminum substrate 1, a clearance hole of the insulating layer 7. 2 through which a through hole 8 having a diameter smaller than that of the clearance hole 2 is formed, and a copper circuit 9 is formed on the outer surface 7a of the insulating layer 7, and the back side of the aluminum substrate 1 where the connection layer 6 is exposed. The second copper plating layer 10 on 1b and the through hole 8
The process includes forming a conductive path 11 that connects the copper circuit 9 and the second copper plating layer 10 therein.

[0007]

According to the structure of the printed wiring board according to the first aspect of the present invention, the copper circuit 9 formed on the outer surface 7a of the insulating layer 7 is described.
Is the aluminum substrate 1 covered with the connection layer 6 via the conductive path 11 in the through hole 8 and the second copper plating layer 10.
Since it is connected to, it will surely conduct electricity.

According to the method of manufacturing a printed wiring board according to the second aspect of the present invention, the second copper plating layer 10 is formed on the connection layer 6 where the black oxide treated surface is polished and the copper is exposed. The copper circuit 9 formed on the outer surface 7a of the layer 7 and the aluminum substrate 1 are surely conducted.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged sectional view of a main part of a printed wiring board according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (c) are manufacturing methods of the printed wiring board according to an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of a main part showing step by step.

The printed wiring board of the present invention will be described with reference to FIG. The printed wiring board includes an aluminum substrate 1,
This aluminum substrate 1 has a clearance hole 2 penetrating therethrough. In the printed wiring board of the present invention, the aluminum substrate 1 itself functions as a conductive path for a ground circuit, a power supply circuit or the like.

The printed wiring board has a connection layer 6 covering the surface of the aluminum substrate 1. The 6-connection layer 6 covers not only the front and back surfaces of the aluminum substrate 1 but also the inner wall of the clearance hole 2. The connection layer 6 is composed of a zinc film 3, a nickel plating layer 4, and a first copper plating layer 5, which are inner layers. The zinc film 3 is formed by replacing the surface layer surface of the aluminum substrate 1 with zinc. Specifically, the aluminum substrate 1 is buffed, degreased, washed with water, and then dipped in an aqueous solution of dilute sulfuric acid having a temperature of 50 ° C. and a concentration of about 15% by weight for 2 to 5 minutes,
Further, it is immersed in an aqueous solution of nitric acid having a concentration of about 50% by weight at room temperature. After washing with water, zinc oxide 20 g / liter, sodium hydroxide 120 g / liter, ferric chloride 2 g / liter, Rochelle salt 50 g / liter, sodium nitrate 1 g
To a solution containing 15 liters / liter at a temperature of 15 to 30 ° C.
The zinc film 3 is formed by immersing for about 60 seconds. The nickel plating layer 4 is formed by an electrolytic nickel plating method or an electroless nickel plating method. The first copper plating layer 5
Is formed by, for example, copper sulfate plating. Since the connection layer 6 has the nickel plating layer 4 and covers the aluminum substrate 1 with the nickel plating layer 4, the connection between the aluminum substrate 1 and the first copper plating layer 5 is prevented even if the zinc film 3 is thin. It does not react electrically.

In the printed wiring board of the present invention, the surface layer 6a of the connection layer 6 covering the surface side 1a of the aluminum substrate 1 and the clearance hole 2 is subjected to black oxide treatment, and the black oxide treated connection layer 6 is formed. An insulating layer 7 is provided. The black oxide treatment is a copper oxidation treatment method that is generally used when producing a multilayer printed wiring board, and when the black oxide treatment is performed,
Adhesion between the first copper plating layer 5 and the insulating layer 7 becomes good.

The printed wiring board has a through hole 8 penetrating the insulating layer 7 where the clearance hole 2 is located and having a diameter smaller than that of the clearance hole 2. A conductive path 11 is formed in the through hole 8. The printed wiring board has a copper circuit 9 on the outer surface 7a of the insulating layer 7.
The second copper plating layer 10 is formed so as to be connected to the connection layer 6 on the back surface side 1b of the aluminum substrate 1. And
The copper circuit 9 and the second copper plating layer 10 are connected by the conductive path 11 in the through hole 8. The second copper plating layer 10 and the conductive paths 11 are formed by copper plating, and the copper circuit 9 is formed on the insulating layer 7 even if it is formed by etching a copper foil arranged on the insulating layer 7. The formed copper plating may be formed by etching.

With the above structure, the copper circuit 9 formed on the outer surface 7a of the insulating layer 7 has the conductive path 11 in the through hole 8,
Also, it is electrically connected to the aluminum substrate 1 through the second copper plating layer 10. In the printed wiring board of the present invention, the area of the conductive portion between the second copper plating layer 10 and the aluminum substrate 1 is large, and the conductive connection is ensured. Furthermore, the printed wiring board is an aluminum substrate 1
Since it is covered with nickel plating layer 4, aluminum substrate 1
Since there is no electrical reaction between the first copper plating layer 5 and the first copper plating layer 5, disconnection hardly occurs and reliability is excellent.

Next, a method for manufacturing a printed wiring board according to the present invention will be described with reference to FIGS.

As shown in FIG. 2A, an aluminum substrate 1 having a clearance hole 2 penetrating therethrough is used as a constituent material of the printed wiring board of the present invention. In the present invention, the aluminum substrate 1 is replaced with zinc, and then nickel plating and copper plating are performed. As a result, the connection layer 6 including the zinc film 3, the nickel plating layer 4, and the first copper plating layer 5 is formed on the aluminum substrate 1 from the inner layer.
The zinc film 3 is formed by replacing the surface of the aluminum substrate 1 described above with zinc. The nickel plating may be either electrolytic plating or electroless plating. By performing the nickel plating, even if the zinc film 3 is thin and partially missing, the aluminum substrate 1 and the first
There is no electrical reaction between the copper plating layers 5. The copper plating method is performed using, for example, a copper sulfate plating solution.

In the present invention, the surface layer 6a of the connection layer 6 is subjected to black oxide treatment. The black oxide treatment is a copper oxidation treatment method. For example, it is immersed in an aqueous solution containing sodium chlorite and sodium hydroxide as components to form a copper oxide film. By performing this black oxide treatment, the adhesion with the insulating layer 7 described later becomes good.

Next, an insulating layer 7 formed by hardening resin is formed on the front surface side 1a of the aluminum substrate 1 and in the clearance hole 2. As shown in FIG. 2B, the method of forming the insulating layer 7 is performed by the surface side 1a of the aluminum substrate 1 on which the connection layer 6 is formed.
A prepreg 13 semi-cured by impregnating a resin into a base material such as glass cloth is placed on the base material, and a copper foil 14 having a thickness of 9 to 70 μm is further provided.
To arrange. On the other hand, a release film 12 made of triacetate or the like is arranged on the back surface 1b of the aluminum substrate 1. afterwards,
When heated and pressed, the resin of the prepreg is completely cured and the insulating layer 7 is formed. Depending on the thickness of the insulating layer 7 to be obtained, the number of prepregs 13 arranged on the front surface side 1a of the aluminum substrate 1 is appropriately determined. The resin used for the prepreg 13 is a thermosetting resin, and examples thereof include epoxy resin, polyimide resin, and PPO resin.
At the time of heating and pressurization, a part of the resin in the prepreg 13 flows into the clearance hole 2 and the clearance hole 2
The insulating layer 7 is also formed inside. When the aluminum substrate 1 is thick, for example, 1.0 mm or more, it is preferable to insert a resin or a filler containing a resin into the clearance hole 2 and heat and pressurize.

In the present invention, after the heating and pressurization, the release film 12 is peeled off, and then the black oxide treated surface of the back surface 1b of the aluminum substrate 1 is polished to form the connecting layer 6
To expose. Further, by this polishing, the resin flowing out to the back surface side 1b of the aluminum substrate 1 can be removed. Further, as shown in FIG. 2C, a through hole 8 having a diameter smaller than that of the clearance hole 2 penetrating from the front surface to the back surface is opened at a position where the clearance hole 2 of the insulating layer 7 is located.

If necessary, desmear treatment is performed in order to remove the residual resin residue. This desmear treatment is appropriately selected depending on the type of resin. For example, when the prepreg 13 containing an epoxy resin is used, it is immersed in an aqueous solution of permanganate to remove resin residue.

Next, a copper circuit 9 is formed on the outer surface 7a of the insulating layer 7.
Is the back surface side 1b of the aluminum substrate 1 where the connection layer 6 is exposed.
Then, a second copper plating layer 10 is formed, and a conductive path 11 that connects the copper circuit 9 and the second copper plating layer 10 is formed in the through hole 8. The second copper plating layer 10 and the conductive path 1
1 is formed by copper plating, and the copper circuit 9 is formed by etching a copper foil 14 provided on the insulating layer 7. By the above method, as shown in FIG. 1, a printed wiring board in which the copper circuit 9 on the outer surface 7a of the insulating layer 7 and the aluminum substrate 1 are electrically connected to each other can be obtained.

According to the invention, the copper circuit 9 is connected to the conductive path 1.
Since it is connected to the aluminum substrate 1 covered with the connection layer 6 via the first and second copper plating layers 10, the area of the conductive portion with the aluminum substrate 1 is wide and a printed wiring board having reliable conduction can be obtained. To be The printed wiring board has an aluminum substrate 1 and a first
Since there is no possibility that the copper-plated layer 5 will directly contact, disconnection is unlikely to occur and reliability is excellent.

[0024]

According to the printed wiring board according to the first aspect of the present invention, the area of the conductive portion with the aluminum substrate 1 is large, and the conductive wiring is surely conducted, and between the aluminum substrate 1 and the first copper plating layer 5. Since it does not react electrically, it does not easily break and is highly reliable.

The printed wiring board obtained by the method for manufacturing a printed wiring board according to the second aspect of the present invention has a large area of a conductive portion with the aluminum substrate 1 so as to surely conduct electricity, and the aluminum substrate 1 and the first Since there is no electrical reaction between the copper plating layers 5, disconnection is unlikely to occur and reliability is excellent.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a printed wiring board according to an embodiment of the present invention.

2 (a) to 2 (c) are enlarged cross-sectional views of a main part showing, step by step, a method for manufacturing a printed wiring board according to an embodiment of the present invention.

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

[Explanation of symbols]

 1 Aluminum Substrate 1a Front Side 1b Back Side 2 Clearance Hole 3 Zinc Film 4 Nickel Plating Layer 5 First Copper Plating Layer 6 Connection Layer 6a Surface Layer 7 Insulating Layer 7a Outer Surface 8 Through Hole 9 Copper Circuit 10 Second Copper Plating Layer 11 Conductive path 12 Release film 13 Prepreg 14 Copper foil

Claims (2)

[Claims] 1. A printed wiring board having an aluminum substrate (1) as a conductive path, the clearance hole (2) penetrating therethrough.
An aluminum substrate (1) having: a connecting layer (a zinc film (3) from an inner layer, a nickel plating layer (4), and a first copper plating layer (5) covering the surface of the aluminum substrate (1). 6), the surface layer (6) of the connection layer (6) covering the surface side (1a) of the aluminum substrate (1) and the clearance hole (2).
a) is subjected to a black oxide treatment, and an insulating layer (7) connected to the aluminum substrate (1) through the black oxide treated connection layer (6) and a position where the clearance hole (2) is located. A through hole (8) having a smaller diameter than the clearance hole (2) formed in the insulating layer (7), a copper circuit (9) formed on the outer surface (7a) of the insulating layer (7), the aluminum substrate ( 1) Back side (1
The second copper plating layer (10) formed in b) and the conductive path (11) for communicating the copper circuit (9) with the second copper plating layer (10) are provided in the through hole (8). A printed wiring board characterized by being provided. 2. A method of manufacturing a printed wiring board, which comprises producing a printed wiring board using an aluminum substrate (1) as a conductive path by the following steps. In the above step, the aluminum substrate (1) having the penetrating clearance hole (2) is subjected to zinc substitution and nickel-plated and copper-plated to form a connection layer (6). A step of subjecting the surface layer (6a) to a black oxide treatment, a step of forming an insulating layer (7) formed by curing a resin on the surface side (1a) of the aluminum substrate (1) and in the clearance hole (2), A step of polishing the black oxide treated surface of the back surface side (1b) of the substrate (1) to expose copper of the connection layer (6), at the location of the clearance hole (2) of the insulating layer (7) described above. A step of opening a through hole (8) having a diameter smaller than that of the clearance hole (2), and a copper circuit (9) on the outer surface (7a) of the insulating layer (7),
The second copper plating layer (10) is provided on the rear surface side (1b) of the aluminum substrate (1) where the connection layer (6) is exposed, and the copper circuit (9) and the second copper plating layer (9) are provided in the through hole (8). Forming a conductive path (11) communicating with the copper plating layer (10).