JP2007273667A - Electroplating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroplating method which forms fine pattern of high aspect ratio, that has been incapable of forming by electrolytic copper plating (e.g. subtractive (panel plating)) method. <P>SOLUTION: A printed board 5-1' is electroplated, by using shield plates 9' having holes 21-1 to 21-3, corresponding to holes 22-1 to 22-3 for through-holes of the printed board 5-1' by inhibiting the electroplating current from flowing to the printed board 5-1'. This plating method is effective, especially on a multilayer printed board that is to have a high aspect ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to, for example, a method for manufacturing a printed circuit board, and more particularly to electrolytic plating for through holes.

A conventional method for manufacturing a printed circuit board will be described with reference to FIGS.
FIG. 1 shows an example of a cross-section of a laminate when manufacturing a combination of a four-layer substrate and a six-layer substrate as an example of the state of manufacture in the multilayer press step of the printed circuit board.
First, as shown in FIG. 1 (a), core materials 1-1 and 1-2 with inner layer pattern 2 formed on both sides are prepared, and copper foil 4-1 prepreg 3-1, Core material 1-1, prepreg 3-2, core material 1-2, prepreg 3-3, and copper foil 4-2 are stacked in this order. Then, it heat-bonds with a lamination press machine, and produces one board | substrate (board | substrate after lamination | stacking).

Next, as shown in Fig. 1 (b), through-holes 90 are drilled on the laminated substrate with an NC drilling machine, desmeared, electroless copper plated, and electroless copper plated film 6 is formed. Form (Substrate 5-1).
Next, as shown in FIG. 1C, electrolytic copper plating is applied to the substrate 5-1 to form a thicker copper plating film 7 (substrate 5-2). In addition, the arrow drawn in FIG.1 (c) has shown the flow of the copper ion of electrolytic plating typically.
Next, as shown in FIG. 1 (d), an extra portion is removed from the copper plating layer 7 by etching or the like on the substrate 5-2 to form an outer layer pattern 8, and then a solder resist is printed, and further surface treatment is performed. To complete the substrate 5-3.

The electrolytic copper plating tank for performing the electrolytic copper plating of FIG. 1 (c) will be described with reference to FIG. Fig. 2 (a) is a top view of the electrolytic copper plating bath, and Fig. 2 (b) is a shield when the electrolytic copper plating bath is viewed from the right (in the direction of arrow A in Fig. 2 (a)). It is a diagram of plate 9.
In FIG. 2, a plating solution is put in an electrolytic copper plating tank, and a substrate 5, a shielding plate 9, and an anode ball (anode rod) 10 are immersed in the plating solution.
The shielding plate 9 has an opening (penetration) in the center so that copper ions can easily move.
The shielding plate 9 and the anode ball 10 are placed on the left and right sides of the substrate 5 at a predetermined distance. At this time, the shielding plate 9 and the anode ball 10 are fixed.

  In recent years, there has been a demand for downsizing and high functionality of electronic devices, and accordingly, printed boards are also required to be downsized and high in density. In the conventional method, in the case of a substrate with a high aspect ratio (base material 14 thickness t / drilling diameter Φ), the uniform electrodeposition (through the plating) in the through hole is poor, so ensure the plating thickness in the through hole. Then, the plating thickness of the surface becomes thick.

FIG. 4 is a diagram for explaining a problem in pattern formation when the plating thickness on the surface of the printed circuit board is large, and shows a partial cross-sectional structure of the substrate.
In order to perform electrolytic copper plating by a subtractive method (panel plating method) as shown in FIG. 1 (c), a plating method using an electrolytic copper plating tank as shown in FIG. 2 (for example, see Patent Document 1). When used, a thinner plating thickness is advantageous for pattern formation. For this reason, when the gap between the etching resists 11 is narrow as shown in FIG. 4 (a), the outer layer pattern 8 formed by removing the excess portion from the copper plating film 7 is etched after the etching as shown in FIG. 4 (b). A short circuit occurs on the side wall of the conductor pattern, making it difficult to form a fine pattern.
JP 2002-121694 A

The prior art described above has a drawback that it is difficult to form a fine pattern in the case of a high aspect ratio substrate.
An object of the present invention is to provide an electrolytic plating method that eliminates the above-described drawbacks and enables formation of a fine pattern that is impossible with conventional electrolytic copper plating methods (for example, subtractive method (panel plating method)). It is to provide.

In order to achieve the above object, the plating method of the present invention is to perform electrolytic plating using a shielding plate having a hole in a position corresponding to a through hole of a printed board.
Then, except for the portion where the hole is formed, the shielding plate prevents the electrolytic plating current from flowing on the surface of the printed board.

  According to the present invention, since electrolytic copper plating is performed using a shielding plate provided with a hole in a position corresponding to a hole (through hole) of a printed circuit board, a subtractive method (panel plating method) for a substrate having a high aspect ratio is performed. ) Makes it easy to form a fine pattern. Furthermore, since the electrodeposition in the hole can be improved, the through hole connection reliability of the high aspect ratio substrate is improved. Furthermore, the normal NC drilling machine and data can be used to create the shielding plate, which is efficient and can reduce development costs.

An embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram for explaining the relationship between the shielding plate and the printed board according to an embodiment of the present invention. FIG. 6 is a cross-sectional view of a part of the printed circuit board in the plating tank, and the movement of the electrolytically plated copper indicated by arrows. FIG. 7 is a diagram for explaining the plating and pattern formation on the surface of the printed board, and is a board showing an example of a six-layer board after electroless copper plating when using the shielding plate of the present invention. FIG.
FIG. 5 (a) is a perspective view showing an embodiment of the shielding plate 9 'of the present invention. In FIG. 5 (a), a vinyl chloride plate is prepared, and an NC drill 13 is used to drill a hole at a position corresponding to the through hole position of the substrate 5-1 'using an NC drilling machine. The hole diameter is, for example, a hole larger than the through-hole diameter of the substrate 5-1 ′. For example, it is n times the through-hole diameter of the substrate 5-1 ′ (n is a positive number and may be smaller than 1). Of course, this hole diameter may be a different ratio between the central portion and the end portion of the substrate. Moreover, the hole cross-section may not be constant, such as a tapered shape, such as the hole diameter being different between the front side and the back side of the shielding plate. FIG. 5 (b) is a plan view of the shielding plate 9 'after drilling.
If the position of the hole is the same as the hole position of the through hole, the hole position data for the through hole, that is, the data of the NC drilling machine can be used.

FIG. 5 (c) shows a printed circuit board before plating with a through hole for using the shielding plate 9 '. 5 (a) to 5 (c), since the description is complicated, only the relationship between some holes will be described.
The holes 21-1, 21-2, and 21-3 of the shielding plate 9 'shown in FIG. 5 (a) and the holes 21-1, 21-2, and 21- of the shielding plate 9' shown in FIG. 5 (b). 3 is the same hole, and the holes 22-1, 22-2, and 22-3 for the through hole in the substrate 5-1 ′ shown in FIG. 5 (c) are centered on the holes corresponding to the respective branch numbers. In the same position.

FIG. 5 (d) is a view for explaining an electrolytic copper plating tank for performing electrolytic copper plating of the present invention, and FIG. 5 (d) is a view (top view) of the electrolytic copper plating tank as viewed from above. is there.
In FIG. 5 (d), a plating solution is put in an electrolytic copper plating tank, and a substrate 5-1 ', a shielding plate 9', and an anode ball 10 are immersed in the plating solution. In this way, the shielding plate 9 ′ described in FIGS. 5 (a) and 5 (b) has a narrow space between the substrate 5-1 ′ and the anode ball 10 from the substrate 5-1 ′ (for example, 10 mm). Below) Install.
That is, the hole position of the shielding plate 9 'and the hole position of the substrate 5-1' are as follows: from the anode ball 10 through the hole 22-1 for the through hole of the substrate 5-1 'through the hole 21-1 of the shielding plate 9'. Is in a position where The relationship between the other hole for the substrate 5-1 'and the other hole for the shielding plate 9' is the same for the corresponding holes.

Next, as shown in FIG. 6, electrolytic copper plating is performed in the plating tank of one embodiment of the present invention shown in FIG. 5 (d) to form a thick copper plating film (through hole wall surface plating layer 12) on the through hole wall surface. To do. In addition, the arrow drawn in FIG. 6 has shown typically the flow of the copper ion of electroplating.
As shown in the figure, the flow of copper ions for electrolytic plating is blocked by the shielding plate 9 'on the surface of the substrate 5-1', and the plating thickness can be reduced, while the wall surface of the hole for the through hole has a plating thickness. Can be increased.
Furthermore, there is an effect of reducing the amount of current (current density) of electrolytic plating.

Next, as shown in FIG. 7, the excess portion is removed from the outer layer pattern 7 'of the substrate 5' (FIG. 7 (a)) by etching or the like, and after forming the outer layer pattern 8 ', a solder resist is printed. Further surface treatment is performed to complete the substrate 5 '(FIG. 7 (b)).
As described above, as shown in FIG. 5 (d), by installing the shielding plate 9 'in which holes are drilled corresponding to the positions of through holes, the current density on the surface of the substrate 5' is reduced, and the surface It is possible to prevent the plating from becoming thick.

  As described above, by reducing the variation in the plating thickness of the surface, there is no short circuit of the pattern side wall due to etching, and a fine pattern can be formed at the time of circuit pattern formation.

  Another embodiment of the present invention will be described with reference to FIG. FIG. 8 is used in combination with a copper plating method in which a plating solution such as a jet apparatus known to have a thick plating in a through hole is flowed in a plating tank.

  In the above-described embodiment, copper is used as the plating material. However, the plating material is not limited to copper, and may be nickel, solder, or the like. Further, the material of the shielding plate does not need to be vinyl chloride, and any material having an insulating property may be used.

  According to the above embodiment, using the shielding plate having the hole corresponding to the through hole hole of the printed circuit board, the hole of the shielding plate is arranged in a straight line connecting the through hole hole of the printed circuit board and the anode electrode. Since electrolytic copper plating is performed, formation of a fine pattern (for example, a line width of 75 μm or less) by a subtractive method (panel plating method) of a printed circuit board having an aspect ratio of 5 or more was easily realized.

Furthermore, since it is possible to improve the throwing power in the through hole, the connection reliability of the through hole of the high aspect ratio substrate is improved.
Furthermore, since data of a normal NC drilling machine can be used for drilling the shielding plate for producing the shielding plate of the present invention, it is efficient and the development cost can be reduced.
The present invention is particularly effective for a multilayer printed board having a high aspect ratio.

Sectional drawing for demonstrating the manufacture example of the 6 layer board using the conventional electrolytic copper plating method. The front view which showed the figure which looked at the electrolytic copper plating tank from the top, and the shielding board. Sectional drawing of a board | substrate at the time of a high aspect ratio. Sectional drawing for demonstrating the case where the plating thickness of the surface is thick. The figure for demonstrating one Example of this invention. The figure for demonstrating one Example of this invention. The figure for demonstrating one Example of this invention. The figure for demonstrating one Example of this invention.

Explanation of symbols

  1-1, 1-2: Core material, 2: Inner layer pattern, 3-1, 3-2, 3-3: Prepreg, 4-1, 4-2: Copper foil, 5, 5 ', 5-1, 5-1 ', 5-2, 5-3: substrate, 6: electroless copper plating film, 7, 7': copper plating film, 8, 8 ': outer layer pattern, 9, 9': shielding plate, 10: Anode ball, 11: etching resist, 12: through hole wall plating layer, 13: NC drill bit, 14: base material, 21: hole, 22: hole for through hole.

Claims (1)

An electrolytic plating method characterized by using a shielding plate having a hole in a position corresponding to a through hole of a printed board.

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