JPH01253293A - Printed wiring substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize the increase of a sectional area of a pattern, through which a large current is made to flow, without expanding the pattern in width so as to improve it in integration by a method wherein parts of the wiring pattern are formed of plating films different from each other in thickness respectively. CONSTITUTION:Wiring circuit sections 3 and 4 (region A) and a power circuit section 5 (region B) are formed on a rear 2a of a base board 2 through an electroplating. Through-holes 3a and 3b are provided to both the ends of the circuit sections 3 and 4. The plating thickness of the circuit section 5 provided inside the region B is nearly two times as large as those of the circuits 3 and 4 positioned inside the region A. Then, the sectional area of the pattern is made to increase without expanding it in width so much. By these processes, the pattern through which a large current is made to flow can be increased in a sectional area with expanding it in width, so that the pattern can be in creased in integration.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a printed wiring board in which metal wiring is patterned by plating on an insulating base substrate, and a method for manufacturing the same, and particularly relates to a printed wiring board in which a pattern of metal wiring is formed by plating on an insulating base substrate, and a method for manufacturing the same. The present invention relates to an improvement in the shape of a plating film that allows the pattern width of a relatively large wiring portion to be narrowed and a high degree of integration to be achieved.

[Conventional technology]

In the manufacture of printed wiring boards, there is a plating method as a method of patterning metal wiring on a base substrate. For example, a base substrate on which a plating resist film is attached according to the shape of the wiring pattern is immersed together with an electrode in a plating solution, the cathode of the V source is connected to the base substrate, the anode is connected to the electrode, and the gap between the two is connected. In this method, a plating film is formed on the portion exposed from the plating resist film by applying a predetermined voltage to the plating resist film.

By the way, in the wiring pattern of the printed wiring board, there is a part such as a power supply circuit part where a relatively large current needs to flow, and the cross-sectional area of the pattern needs to be increased accordingly in such a part. Conventionally, as a method for enlarging the cross-sectional area, it has been common to widen the pattern width of the portion.

[Problem that the invention seeks to solve]

However, as mentioned above, when expanding the pattern width to support large currents, the required area of the pattern in plan view naturally increases, which becomes a constraint on higher pattern integration, and ultimately leads to an increase in the size of the board. There is a problem with putting it away.

As a method to suppress such expansion of pattern area,
Conventionally, there was a method of depositing solder in layers on the plating film, but this method required floating the condensed liquid substrate with solder resist formed on the substrate on the solder bath surface, which increased the number of steps and reduced productivity. decreases. Since the solder-adhered area is exposed to the atmosphere, there is a risk of siltation due to the humidity of the atmosphere, and it is not possible to place the solder in close proximity with the adjacent pattern, resulting in the inability to improve the degree of integration.Furthermore, the conductivity of the solder is Cu. In comparison, it is about 1/3, which is not very good, and from this point of view as well, the effect of improving the degree of integration is low.

Therefore, the present invention was made in order to solve the above-mentioned conventional problems, and without increasing the manufacturing process too much,
Another object of the present invention is to provide a printed wiring board and a method for manufacturing the same, which can increase the cross-sectional area of the pattern without increasing the pattern width, achieve higher integration of the pattern, and reduce the size of the board.

[Means for solving problems]

The specific invention of the present application provides a printed wiring board in which a wiring pattern made of a plating film is formed on a base substrate,
It is characterized in that the plating film in some areas of the wiring pattern is formed thicker than the plating film in other areas.

Further, a related invention of the present application is a method for manufacturing a printed wiring board in which the plating film in some areas of the wiring pattern is thicker than the plating film in other areas, the base board and the electrodes being immersed in a plating solution, and electroplating. The related invention method is characterized in that electroplating is carried out in multiple stages, and in each stage a mask of a different shape is attached to the base substrate or electrode to perform electroplating. This includes both a method of attaching a mask to an electrode and a method of attaching a mask to an electrode, but when attaching a mask to an electrode, it is preferable to arrange the electrode and the base substrate so as to face each other.

In addition, another related invention of the present application is to attach a mask to the poles when performing the electroplating, and as this mask,
The feature is that a mask with a large aperture ratio is used in the area corresponding to the area where the plating film thickness is to be increased.

[Effect]

In the specific invention of the present application, the plating film thickness of the wiring pattern of the printed wiring board, for example, the power supply circuit part that connects the external power supply and the components mounted in the board, is made thicker than other parts, so that the pattern width can be reduced. The cross-sectional area of the pattern can be increased without increasing the width, therefore, it is possible to handle a large current without increasing the width of the pattern, the degree of integration of the wiring pattern can be improved, and the size of the substrate can be reduced.

In addition, in the related invention of the present application, for example, electroplating is divided into two stages, and a mask of a different shape is attached to the base substrate or electrode in each stage, so that in the first stage plating, the entire area is covered. The plating is deposited on the pattern, and in the second step, the plating is deposited only on the pattern in the region where the plating film thickness is to be increased, thereby making it possible to make the plating film thickness in the desired region thicker than in other parts. In this case, if a mask is attached to the substrate side, the film thickness can be clearly changed depending on the region. In addition, if a mask is attached to the electrode side, the first stage plating is performed on a number of substrates with the first mask attached, and each of the above substrates is plated again with the second mask attached. Often, a large number of substrates can be plated by changing the mask once, improving work efficiency.

In another related invention, a mask with a large aperture ratio is attached to the electrode in the region corresponding to the region where the film thickness is to be increased, so that the current density in the region is higher than in other regions, resulting in - In the plating process, the film thickness of the pattern can be partially increased, and the work efficiency is further improved compared to the related invention method described above.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 4 are diagrams for explaining a printed wiring board and a manufacturing method thereof according to an embodiment of the present invention.

In FIG. 1 schematically showing a printed wiring board according to this embodiment, 1 is a printed wiring board, which has a wiring circuit section 3° 4 (fil area A) on the back surface 2a of a base board 2.
and the power supply circuit section 5 (area B) are formed by electroplating. At both ends of the wiring circuit section 3.4,
Through holes 3a and 4a are formed, and although not shown, the surface 2 of the substrate 2 is formed in the through holes 3a and 4a.
The terminals of the electronic components mounted on the b side are inserted and the soldering connections are made. Although not shown, the terminal of an external connection socket mounted on the surface 2b is inserted into the through hole 5a of the power supply circuit section 5, and soldering is performed directly.

The plating film thickness of the power supply circuit section 5 located within the region B is approximately twice that of the wiring circuit section 3.4 located within the region A.

In FIGS. 3 and 4, reference numeral 24 denotes a plating device for forming the wiring circuit portion 3.4 and the power supply circuit portion 5 on the base substrate 2 by plating, and the plating device 24 is connected to the main body portion 25. , and a supply device 27 that supplies an acidic steel plating solution P such as copper sulfate in a plating solution tank 26 to this. This supply device 27 includes a supply pump 28 and a supply side header 29 . The first one connects the discharge side headers 30. Second supply passages 31, 32. 1st. 2nd discharge passage 33°34
and a first one disposed in each passage. Second on-off valve 35.36
, 1st. 2nd flow meter 37.38, 1st degree second solenoid valve 39
．． It consists of 40.

Further, the main body section 25 is constructed by disposing electrodes 44, 44 facing each other in a casing 43 constituting a plating chamber, and forming a holding bracket 45 between the two electrodes. The electrode 44 is connected to the anode of the power source, and the holding bracket 45 is connected to the cathode.

Note that when a base board as a member to be plated is attached to the holding bracket 45, the casing 43 is attached to the first base board by this board. It is divided into second plating chambers 46 and 47, and the first supply and discharge passages 31.33 and the second supply and discharge passages 32.34 communicate with each other via these two plating chambers 46 and 47.

Next, a case will be described in which the printed wiring board 1 shown in FIG. 1 is manufactured by a method according to an embodiment of the related invention of the present application.

For example, a base substrate 2 is prepared by laminating about 10 glass fiber-containing epoxy resin layers and press-molding them, and through-holes are formed at predetermined positions.
A base Cu plating layer with a thickness of 2 to 5 μm is formed on both surfaces of the base substrate and the inner circumferential surface of the through hole by electroless plating to impart conductivity to the base substrate 2.

(2) A photosensitive dry film is thermocompression bonded onto the base Cu plating layer, and a mask having a shape corresponding to each of the circuit parts 3 to 5 is closely attached to the upper surface of the film and exposed.

This is developed, thereby forming a plating resist substrate 18 (see FIG. 3) covered with a plating resist film.

(2) Next, a Cu plating layer is formed on the plating resist substrate 18 using the plating apparatus 24.

In this case, first, in order to perform the first stage plating, an ordinary titanium alloy electrode 44 without a mask attached to the surface is used.
a (FIG. 2(a)) is installed in the casing 43.

Then, the plating resist substrate 18 is mounted on the holding bracket 45 inside the casing 43, the circulation pump 28 is operated, and the plating power source is turned on. Then, plating solution P becomes the first plating solution. From the second supply passage 31.32 to the casing 43
The Cu plating layer is supplied to the plating resist substrate 18, flows along both surfaces of the plating resist substrate 18, and forms a Cu plating layer on the portion of the substrate 18 exposed from the pattern opening of the plating resist film.

Also, at this time, the opening degree of the first on-off valve 35 is changed to the second on-off valve 36.
If it is set larger, the flow velocity F1 in the first plating chamber 46 in the casing 43 becomes higher than the flow velocity F2 in the second plating chamber 47, and the pressure in the first plating chamber 46 becomes higher. Therefore, a part of the plating solution flows from the first plating chamber 46 through the through hole 13 into the second plating chamber 47 (arrow F3), and as a result, the plating layer is reliably formed on the base plating layer of the through hole. It will be formed.

■ Next, in order to perform the second stage plating, the electrode 4 is attached with a plating resist mask 45 made of an insulating sheet.
4b (FIG. 2(bl)) is attached to the plating apparatus 24. This mask 45 has an opening 45a formed in a portion corresponding to the region B, so that only the power supply circuit section 5 located across the region B is formed. The plating is deposited on the circuit portion 5, and the thickness of the plating film on the circuit portion 5 is approximately twice that of the wiring circuit portions 3 and 4.

■ The substrate on which the plating film is formed is thoroughly cleaned in a stripping solution consisting of an alkaline solution, the plating resist film is peeled off, and further immersed in an etching solution, and the connecting land portions of each of the circuit sections 3 to 5 are By forming a solder resist film except for the above, the printed wiring board 1 shown in FIG. 1 is manufactured.

As described above, according to the method of this embodiment, the first stage plating is performed using the electrode 44a without a mask as the electrode 44, and then the opening 45a is formed only in the portion facing the thick film wiring portion (region B). Electrode 44b equipped with a mask 45 having
Since the second stage plating is performed using a plating layer, the plating film thickness of the power supply circuit section 5 can be made twice as thick as that of the wiring circuit section 3.4. Therefore, pattern cutting can be performed without expanding the pattern width. It is possible to increase the area, achieve highly integrated changes in patterns, and reduce the size of the substrate.

FIG. 2 fc) shows an electrode for carrying out a method according to an embodiment of another related invention of the present application. The mask 45 attached to the electrode 44C of this embodiment is the same as that of the printed wiring board 1 of the above tm.
An opening 45a is formed in a portion corresponding to region B, and a large number of through holes 45b are formed in a portion corresponding to region A.

When the electrode 44C of this embodiment is attached to the plating apparatus 24 and electroplating is performed, the current density in the portion corresponding to the region B becomes higher than the current density in the portion corresponding to the region A, and as a result, the current density in the portion corresponding to the region A becomes higher. The plating film thickness is formed to be thicker than that of the wiring circuit portion 3.4. Furthermore, in this embodiment, there is no need to replace the mask 45 attached to the electrode 44c, so productivity can be greatly improved.

In the above embodiment, a mask was attached to the electrode, but the thickness of the plating film can also be partially changed by attaching a mask to the substrate side.

When attaching a mask to this substrate, the substrate and electrode do not necessarily have to face each other, and the thickness of the plating film can be partially changed even when using a static plating bath, which is conventionally used for boat fishing. .

Further, in the above embodiment, the current density was partially changed by attaching a mask to the electrode, but this partial change in current density can also be realized by changing the shape of the electrode itself.

〔Effect of the invention〕

As described above, according to the printed wiring board according to the specified invention, the wiring pattern is formed with a plating film having a different thickness for each part, so that the pattern width can be increased to increase the pattern cross-sectional area for passing a large current. This can be realized without any problems, and has the effect of improving the degree of pattern integration. Further, according to the related invention of the present application, the plating process is divided into multiple stages, and a mask with a different shape is attached to the electrode or substrate for each stage, or the aperture ratio is reduced in the area corresponding to the thick plating film. Since plating was performed by attaching a large mask to the electrode,
This has the effect of realizing changes in the plating film thickness for each region of the wiring pattern.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a perspective view of a printed wiring board according to an embodiment of the present invention, and FIG. 2 (C1 is a perspective view of an electrode for carrying out the method of an embodiment of another related invention of the present application, and FIGS. 3 and 4 are a plating apparatus for carrying out the method of the above embodiment) 1 is a cross-sectional view and an overall configuration diagram. In the figure, 1 is a printed wiring board, 2 is a base board,
3.4 is the wiring circuit section (wiring pattern), 44.44a
~44c is an electrode, 45 is a mask, and A is a wiring pattern? Area (3) and B are part of the wiring pattern. Patent jaw person Yamaha Motor Co., Ltd. agent Patent attorney Tsutomu Shimoichi

Claims (3)

[Claims] (1) A printed wiring board in which a wiring pattern made of a plating film is formed on a base substrate, wherein the plating film in some areas of the wiring pattern is formed thicker than in other areas. wiring board. (2) A method for manufacturing a printed wiring board in which, when forming a wiring pattern on a base substrate by plating, a plating film in some areas is formed thicker than in other areas, the method comprising: and electrodes are immersed in a plating solution and electroplated in multiple stages,
A method for manufacturing a printed wiring board, characterized in that masks of different shapes are attached to a base substrate or electrodes at each stage. (3) A method for manufacturing a printed wiring board, in which, when forming a wiring pattern on a base substrate by plating, a plating film in some areas is formed thicker than in other areas, the method comprising: is immersed in a plating solution so as to face the electrode, and electroplating is performed by attaching a mask to the electrode in which the aperture ratio of the portion corresponding to the above-mentioned partial area is larger than that of the other area. A method for manufacturing a printed wiring board.