JPH05211386A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To protect a copper layer located under a nickel layer against corrosion caused by a solder layer in a soldering process such at reflow soldering by a method wherein a front and a rear outer layer and a conductor formed on both the front and the rear outer layer and inside a through-hole are of three-layered structure composed of copper-nickel-copper. CONSTITUTION:A copper foil 2 is pasted on the surface of an insulating board 1 to form a copper plated board. A nickel electroplating layer 5 is provided to both the sides of the board 1 as thick as 2mum through watt bath. A through- hole 11 is selectively provided. A copper plating layer 3 is formed as thick as 24mum on all the surface of the inner wall of the through-hole 11 and the nickel layer 5 through an electroplating method with copper sulfate solution. An etching resist film 12 is selectively formed through a conventional tenting method with dry film. The copper plating layer 3, the nickel plating layer 5, and the copper foil 2 are successively etched with cupric chloride solution to obtain a pad 7, a circuit 8, and a through-hole 4. A solder resist film 9 is applied through a screen printing method.

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 and a manufacturing method thereof, and more particularly to a printed wiring board used for surface mounting and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a conventional printed wiring board, pads and circuits on the front and back outer layers are formed by using copper foil and copper of a copper plating layer, and through holes are formed by a copper plating layer.
In this way, all the conductor parts forming the front and back exterior surfaces of the printed wiring board and the through holes are made of copper which has excellent electrical conductivity, is inexpensive and easy to process, and has good solderability.

FIGS. 8A to 8F are cross-sectional views showing a method of manufacturing a conventional printed wiring board in the order of steps.

First, as shown in FIG. 8A, a copper foil 2 is laminated on the surface of an insulating substrate 1 by lamination.

Next, as shown in FIG. 8B, a through hole 11 is formed by selectively punching.

Next, as shown in FIG. 8C, a copper plating layer 3 is formed on the surface including the front and back copper foils 2 and the inner walls of the through holes 11 by a panel plating method.

Next, as shown in FIG. 8D, an etching resist film 12 is selectively formed using a dry film.

Next, as shown in FIG. 8E, the copper plating layer 3 and the copper foil 2 are sequentially etched using the etching resist film 12 as a mask, and then the etching resist 12 is peeled off to remove the desired pad 7, A circuit 8 and a through hole 4 are obtained.

Next, as shown in FIG. 8F, a solder resist film 9 is selectively formed to form a desired printed wiring board 10.

[0010]

In the above-mentioned conventional printed wiring board, when the soldering such as the flow soldering is performed a plurality of times, the copper layer in the through hole opening is diffused by the solder and the copper layer is thinned, resulting in the breakage of the through hole. The number of soldering operations is limited due to problems in connection reliability, such as
Also, when surface-mounted components are mounted, if repair work is performed again by a method such as reflow soldering or hand-mounting, the copper layer of the component mounting pads diffuses into the solder, and the copper layer becomes thin, or the worst case occurs. In this case, the reliability of the connection between the surface mount component and the pad is reduced, and the number of repair works is limited.

An object of the present invention is to prevent a thinned copper layer of a through hole opening and a copper layer of a component mounting pad from diffusing into solder, and to provide a printed wiring board having high connection reliability and a method of manufacturing the same. To provide.

[0012]

The printed wiring board of the present invention comprises:
It has a three-layer structure of a lower copper layer, an intermediate nickel layer, and an upper copper layer, which are formed by sequentially stacking conductor layers formed on an insulating substrate.

The printed wiring board according to the first aspect of the present invention comprises a lower copper layer, an intermediate nickel layer, and an upper copper layer formed by sequentially laminating the conductor layers formed on the front and back outer layers of the insulating substrate. It has a layered structure.

The method of manufacturing a printed wiring board according to the first aspect of the present invention comprises a step of forming a nickel layer on the entire front and back outer surface of the copper-clad laminate by plating, and selectively punching the copper-clad laminate to form through holes. Forming step, forming an inner surface of the through hole and a copper plating layer on the entire surface of the nickel layer, and forming a pattern of a three-layer structure of a lower copper layer, an intermediate nickel layer, and an upper copper layer And a process.

A printed wiring board according to a second aspect of the present invention comprises a lower copper layer, an intermediate nickel layer, and an upper layer formed by sequentially stacking the conductor layers formed on the entire front and back outer layers of the insulating substrate and the through hole inner surface. The copper layer has a three-layer structure.

A method of manufacturing a printed wiring board according to a second aspect of the present invention includes a step of selectively punching a copper-clad laminate to form a through hole, and plating the inner surface of the through hole with copper to form a through hole.
Forming a predetermined circuit by patterning a copper layer, forming a nickel layer on the copper layer on the circuit and on the inner surface of the through hole by nickel plating, and forming a nickel layer on the nickel layer by electroless thick copper plating A step of forming a copper layer,
And a step of selectively applying a solder resist.

[0017]

Next, a manufacturing method of a first embodiment of the first invention will be described with reference to the drawings.

FIGS. 1A to 1G are sectional views showing the manufacturing method of the first embodiment of the first invention in the order of steps for explaining the manufacturing method.

First, as shown in FIG. 1A, a copper-clad laminate is formed by laminating a copper foil 2 on the surface of an insulating substrate 1.

Next, as shown in FIG. 1B, a nickel plating layer 5 is formed by subjecting the entire front and back surfaces to electroplating with nickel of about 2 μm using a Watts bath.

Next, as shown in FIG. 1C, a through hole 1 is provided by selectively punching.

Next, as shown in FIG. 1D, the through hole 1
1. On the inner wall and the surface of the nickel layer 5, a copper plating layer 3 having a thickness of about 25 μm is formed on the entire surface by an electroplating method using a copper sulfate solution.

Next, as shown in FIG. 1E, an etching resist film 12 is selectively formed using a dry film according to a normal tenting method.

Next, as shown in FIG. 1 (f), the copper plating layer 3, the nickel plating layer 5 and the copper foil 2 are sequentially etched using a cupric chloride solution to form pads 7, circuits 8 and through holes. Get 4.

Next, as shown in FIG. 1G, a solder resist film 9 is applied to the exposed surface of the insulating substrate 1 and the surface of the wiring 7 by a screen printing method to form a printed wiring board.

2 (a)-(d) and FIG. 3 (a),
(B) It is sectional drawing shown in order of a process explaining the manufacturing method of the 2nd Example of 1st invention.

First, as shown in FIG. 2A, a nickel plating layer 5 and a through hole 11 were formed in a copper-clad laminate consisting of an insulating substrate 1 and a copper foil 2 by the same steps as in the first embodiment. After that, a copper plating layer 3 having a thickness of about 10 μm is formed by a panel plating method.

Next, as shown in FIG. 2B, a plating resist film 14 is selectively formed on the copper plating 3 by a dry film.

Next, as shown in FIG. 2C, about 15 copper plating layers 13 are formed on the copper plating layers 3 by electroplating with a copper sulfate solution using the plating resist film 14 as a mask.
Apply μm.

Next, as shown in FIG. 2D, a solder layer 16 is laminated on the copper plating layer 13 and provided.

Next, as shown in FIG. 3A, after removing the plating resist film 14, a copper plating layer 3, a nickel plating layer 5, and a nickel plating layer 5, which are laminated with a cupric chloride solution using the solder layer 16 as a mask. The copper foil 2 is etched to obtain pads 7, circuits 8 and through holes 4.

Next, as shown in FIG. 3B, a solder resist film 9 is selectively applied by a screen printing method to form a printed wiring board.

Next, a manufacturing method of the first embodiment of the second invention will be described with reference to the drawings.

4A to 4F and FIG. 5A,
(B) It is sectional drawing shown in order of a process explaining the manufacturing method of the 1st Example of 2nd invention.

First, as shown in FIG. 4 (a), a copper clad laminate is formed by laminating copper foils 2 on the surface of an insulating substrate 1 by laminating.

Next, as shown in FIG. 4B, the through holes 11 are provided by selectively punching.

Next, as shown in FIG. 4C, after applying thin electroless copper plating, a copper plating layer 3 of about 25 μm is formed on the entire surface including the inner wall of the through hole 11 by electroplating with a copper sulfate solution. To form.

Next, as shown in FIG. 4D, an etching resist film 12 is selectively formed by using a dry film in accordance with the usual tenting method.

Next, as shown in FIG. 4 (e), the copper plating layer 3 and the copper foil 2 are sequentially etched using a cupric chloride solution to obtain pads 7, circuits 8 and through holes 4.

Next, as shown in FIG. 4 (f), electroless nickel plating is performed and laminated on the copper plating layer 3 to form a nickel plating layer 5 of about 3 μm.

Next, as shown in FIG. 5A, an electroless copper plating layer 6 having a thickness of 5 μm is selectively formed on the nickel plating layer 5 by a thick electroless copper plating method.

Next, as shown in FIG. 5B, the photo SR
The printed wiring board 10 is formed by forming the solder resist film 9 by the above method.

Next, a manufacturing method of the second embodiment of the second invention will be described with reference to the drawings.

6A to 6E and 7A to 7A.
(C) It is sectional drawing shown in order of a process explaining the manufacturing method of the 2nd Example of 2nd invention.

First, as shown in FIG. 6A, a copper-clad laminate is formed by laminating a copper foil 2 on the surface of an insulating substrate 1.

Next, as shown in FIG. 6B, the through holes 11 are provided by selectively punching.

Next, as shown in FIG. 6C, a copper plating layer 3 having a thickness of about 10 μm is formed by a panel plating method.

Next, as shown in FIG. 6D, a plating resist film 14 is selectively formed on the copper plating layer 3 by a dry film.

Next, as shown in FIG. 6 (e), a copper plating layer 13 is formed on the copper plating layer 3 to a thickness of about 10 μm by electroplating with a copper sulfate solution using the plating resist film 14 as a mask.
m.

Next, as shown in FIG. 7A, an etching resist layer is formed by applying a solder layer 16 on the copper plating layer 13 using an electrolytic solder plating method.

Next, as shown in FIG. 7B, after removing the plating resist layer 14, the copper plating layers 13 and 3 and the copper foil 2 laminated with a cupric chloride solution are etched to form pads 7 and 8. A circuit 8 and a through hole 4 are obtained.

Next, as shown in FIG. 7C, the solder layer 16 is dissolved and removed.

4 (f) and 5 of the first embodiment.
A printed wiring board 10 is formed by forming a nickel plating layer 5, an electroless copper plating layer 6, and a solder resist film 9 in the same steps as in (a) and FIG. 5 (b).

[0054]

As described above, according to the present invention, since the front and back outer layer surfaces and the conductor portions formed on the front and back outer layer surfaces and the through holes have a three-layer structure of copper-nickel-copper, a flow solder, etc. During soldering, the nickel layer blocks the interdiffusion of copper in the surface layer of the through-hole opening and tin in the solder, preventing the copper layer directly under the nickel layer from being eroded by the solder layer. Can be done multiple times,
Through-hole connection reliability can be maintained even when soldering with flow solder, etc., and also during repair work after mounting surface mount components, the nickel layer blocks the interdiffusion of copper in the pad and tin in the solder. Therefore, it is possible to prevent the copper layer directly below the nickel layer from being eroded by the solder layer, and therefore, it is possible to maintain the connection reliability between the surface mount component and the pad even if repeated repair work is performed. effective.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the manufacturing method of a first embodiment of the first invention in the order of steps.

FIG. 2 is a cross-sectional view showing the manufacturing method of the second embodiment of the first invention in the order of steps.

3A to 3C are cross-sectional views showing the manufacturing method of the second embodiment of the first invention in the order of steps.

FIG. 4 is a cross-sectional view showing the manufacturing method of the first embodiment of the second invention in the order of steps.

5A to 5D are cross-sectional views showing the manufacturing method of the first embodiment of the second invention in the order of steps.

6A to 6D are cross-sectional views showing the manufacturing method of the second embodiment of the second invention in the order of steps.

FIG. 7 is a cross-sectional view showing the manufacturing method of the second embodiment of the second invention in the order of steps.

FIG. 8 is a cross-sectional view showing an example of a conventional method of manufacturing a printed wiring board in process order.

[Explanation of symbols]

 1 Insulating Substrate 2 Copper Foil 3,13 Copper Plating Layer 4 Through Hole 5 Nickel Plating Layer 6 Electroless Copper Plating Layer 7 Pad 8 Circuit 9 Solder Resist Film 10 Printed Wiring Board 11 Through Hole 12 Etching Resist Film 14 Plating Resist Film 16 Solder layer

Front page continued (72) Inventor Keisuke Okada 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation

Claims (5)

[Claims] 1. A printed wiring board having a three-layer structure of a lower copper layer, an intermediate nickel layer, and an upper copper layer, which are formed by sequentially laminating conductor layers formed on an insulating substrate. 2. A three-layer structure comprising a lower copper layer, an intermediate nickel layer, and an upper copper layer, which are formed by sequentially stacking the conductor layers formed on the front and back outer layers of an insulating substrate. The printed wiring board according to claim 1. 3. A step of forming a nickel layer on the entire front and back outer surface of the copper-clad laminate by plating, a step of selectively boring the copper-clad laminate to form a through hole, and an inner surface of the through hole. A step of forming a copper plating layer on the entire surface of the nickel layer, and a lower copper layer, an intermediate nickel layer, and an upper copper layer.
3. The method for manufacturing a printed wiring board according to claim 2, further comprising the step of forming a layered pattern. 4. A three-layer structure including a lower copper layer, an intermediate nickel layer, and an upper copper layer, which are formed by sequentially laminating the conductor layers formed on the front and back outer layer surfaces of an insulating substrate and the through hole inner surface, respectively. It has, The printed wiring board of Claim 1 characterized by the above-mentioned. 5. A step of selectively perforating a copper-clad laminate to form a through hole, plating the inner surface of the through hole with a copper to form a through hole, and patterning the copper layer to form a predetermined circuit. A step of forming a nickel layer on the circuit and the copper layer on the inner surface of the through hole by nickel plating, a step of forming a copper layer on the nickel layer by electroless thick copper plating, and selectively soldering The method of manufacturing a printed wiring board according to claim 4, comprising a step of applying a resist.