JPH04246200A - Method for electroplating substrate - Google Patents

Abstract

PURPOSE:To uniformize the thickness of a plating without wasting a part of a substrate and to electroplate the substrate. CONSTITUTION:An auxiliary electrode 13 is frame shaped and opposed to the surface 10a of a substrate 10 to be plated. A negative voltage is impressed on the auxiliary electrode 13 from an auxiliary power source 15. The current density of the auxiliary electrode 13 is controlled to several times that of the substrate 10. The auxiliary electrode 13 absorbs an electric current flowing toward the periphery of the substrate 10 in a plating soln., and the thickness of the plating on the periphery of the substrate 10 is not increased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming panel plating on a ceramic substrate by electrolytic plating.

[0002] The wiring pattern on the surface of the ceramic substrate is
A metal film is formed on the surface of the polished ceramic substrate by sputtering, and then a resist pattern is formed,
Next, panel plating of Cu, Ni, and Au is formed by electrolytic plating, the resist pattern is peeled off, and panel etching is performed.

[0003] If the wiring pattern becomes too thick, heat will be absorbed and the solder will not adhere well, whereas if it becomes too thin, the electrical resistance value will increase or wires will be easily broken.

Therefore, in order to improve the quality of the ceramic substrate, it is necessary that the wiring pattern has uniform electrical characteristics over the entire surface of the ceramic substrate.

[0005] For this purpose, it is necessary that the panel plating be formed with a uniform thickness over the entire surface of the ceramic substrate.

[0006]

2. Description of the Related Art FIG. 12 shows the basic structure of an electrolytic plating method for a substrate.

1 is a sputtered ceramic substrate;
2 is an anode, and 3 is a power supply. In the plating tank,
A current flows as indicated by reference numeral 4, and a panel plating film 5 is formed on the sputtered film of the ceramic substrate 1.

The thickness of the plating film 5 is proportional to the current density. The current 4 is more likely to concentrate on the periphery than the center of the substrate 1,
The current density in the peripheral portion of the substrate 1 is higher than that in the central portion. Therefore, the plating film 5 has a thickness t1 around the substrate 1.
becomes thicker than the thickness t2 of the central portion.

The configuration in FIG. 12 corresponds to (■) in FIG.
As shown in the figure, the thickness t2 of the central portion is 1.74 μm, while the thickness t1 of the peripheral portion is 3.58 μm, and the ratio of the peripheral portion being thicker than the central portion is 100%.

Therefore, in order to solve the above problem, conventionally, as shown in Japanese Patent Publication No. 58-58835, the substrate was
A method was used in which an outer frame was provided as a dummy space on the periphery via a connecting rib, and after electrolytic plating was performed, the connecting rib was broken and the outer frame was removed.

According to this method, the thickened portion of the plating film is removed, and the thickness of the plating film on the substrate is made uniform.

0012

However, according to the above method, the outer frame portion of each board is wasted, and the manufacturing cost increases accordingly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for electrolytic plating of a substrate, which makes it possible to make the plating thickness uniform without increasing manufacturing costs.

[0014]

[Means for Solving the Problems] The invention according to claim 1 provides a frame-shaped auxiliary electrode whose inner edge has substantially the same size as the substrate to be electrolytically plated, in the vicinity of the surface of the substrate facing the anode. The auxiliary electrode is arranged so as to surround the substrate when viewed from the anode side, and a negative voltage is applied to the auxiliary electrode.

[0015] According to a second aspect of the invention, a conductive tape is attached to the surface of the holding frame that holds the substrate to be electrolytically plated, facing the anode, so as to surround the substrate and to be able to peel it off. At the same time, a negative voltage is applied to the conductive tape.

According to the third aspect of the invention, a frame-shaped auxiliary electrode whose inner edge is substantially the same size as the substrate to be electrolytically plated is provided near the surface of the substrate facing the anode and on the anode side. The auxiliary electrode is arranged so as to surround the substrate when viewed from above, and a negative voltage is applied to the auxiliary electrode,
A conductive tape is attached to the surface of the holding frame that holds the substrate facing the anode so as to be able to bend and peel off the substrate, and a negative voltage is applied to the conductive tape. It is structured as follows.

[0017]

According to the first aspect of the invention, the auxiliary electrode absorbs the current flowing through the plating solution toward the periphery of the substrate.

In the second aspect of the invention, the conductive tape serves as a dummy pattern in the conventional example.

[0019] The conductive tape can always be replaced with a new one. In the invention according to claim 3, the auxiliary electrode absorbs the current flowing in the peripheral portion of the substrate. The conductive tape functions as a replaceable dummy pattern.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.

In the figure, 10 is a ceramic substrate, 11 is a holding frame, 12 is an anode, 13 is an auxiliary electrode, and 14 is a voltage V1.
, and 15 is an auxiliary power source with a voltage of V2.

The ceramic substrate 10 does not have an outer frame portion of the dummy pattern and has the same size as the finished ceramic printed wiring board.

The holding frame 11 consists of a pair of frames 16 and 17, as shown in FIG. The frames 16 and 17 are connected to the substrate 10.
The board 10 is fixed with screws 18 while sandwiching the
The periphery is sandwiched and fixed to the holding frame 11.

The frames 16 and 17 are covered with resin and insulated, except for the hook portions 16a and the like.

The auxiliary electrode 13 has a rectangular frame shape, and an inner edge 13a has substantially the same size as the substrate 10.

The auxiliary electrode 13 is arranged near the surface 10a of the substrate 10 facing the anode 12, and so as to surround the substrate 10 when viewed from the anode 12 side, as shown in FIG. be.

In FIG. 1, the ratio of the distance L1 between the substrate 10 and the auxiliary electrode 13 to the distance L2 between the auxiliary electrode 13 and the anode 12, L1:L2, is, for example, 1:3.

[0028] Also, the auxiliary power supply 1 connected to the auxiliary electrode 13
The voltage V2 of 5 is the current density A1 (A
/cm2) is the current density A2 (A/cm2) of the substrate 10
) is set to be approximately three times as large.

During electrolytic plating, as shown in FIG. 4, a current 19 flows through the plating solution, and a plating film 20 is formed on the surface 10a of the substrate 10.

If the auxiliary electrode 13 is not present in the current 19, the current 19a flowing into the periphery of the substrate 10 will be absorbed by the auxiliary electrode 15, as shown in FIG. Only the current 19b that has passed through the inside of the auxiliary electrode 13 flows into the substrate 10. Therefore, when looking at the current density distribution within the surface 10a of the substrate 10, the central portion is approximately the same as the conventional one;
The surrounding area can be kept lower than before.

As a result, the plating film 20 is formed as shown in FIGS. 5 and 6.
As shown in conjunction with (■), the thickness t2 of the central portion is 1.
It is 88μm, which is slightly larger than before, and the thickness of the peripheral part is t.
1 became 2.85, which is significantly lower than before.

[0032] As a result, the ratio of the peripheral portion being thicker than the central portion can be suppressed to about 51%.

FIG. 7 shows a second embodiment of the invention. In FIG. 1, the auxiliary electrode 13 is removed and the anode 1 of the holding frame 11 is removed.
A conductive tape 30 is attached to the surface 11a facing the substrate 10 so as to surround the substrate 10, and the main power source 14 is connected to the conductive tape 30.
This is a configuration in which a negative voltage V1 of V1 is applied in the same manner as in the substrate 10.

[0034] As shown in FIG. 8, the conductive tape 30 has
It is removably attached to the frame 16. Current 31 through the plating solution
flows as shown in FIG. 9, and the substrate 10 and the conductive tape 3
0, a plating film 32 is formed.

The current 31 flows through the conductive tape 30 located outside the substrate 10 as if it were the periphery of the substrate.
The plating film 32 on the conductive tape 30 is the thickest. After electrolytic plating, the peripheral portion of the substrate 10 appears to be closer to the center than the peripheral portion of the substrate.

Therefore, the plating film 32 on the substrate 10 is
As shown in FIGS. 5 and 6, the central portion thickness t
2 is 1.82 μm, which is almost the same as before, and the thickness t1 of the peripheral portion is 3.04 μm, which is considerably smaller than before.

The ratio of the thickness of the peripheral part compared to the central part is
It has been suppressed to around 67%. If a conductive tape with plating is used as is, the area to which the plating adheres will gradually change, and the plating conditions will change, so it must be peeled off and replaced with a new one after each plating. .

FIG. 10 shows a third embodiment of the invention. This embodiment is a combination of the first embodiment and the second embodiment, and in FIG. 10, the same reference numerals are given to the parts corresponding to those shown in FIGS. 1 and 7.

FIG. 11 shows the state of current flow in the plating solution. Of the current 40 output from the anode 12, the substrate 1
The current 40a directed toward the periphery of 0 is absorbed by the auxiliary electrode 13.

Current 40b passing inside the auxiliary electrode 13
spreads out and flows more into the electrically conductive tape 30 and less into the substrate 10, as if the electrically conductive tape 30 were at the periphery of the substrate.

As a result, the plating film 41 on the substrate 10 has a thickness t2 of 1.96 μm at the central portion and a thickness t1 of 2.0 μm at the peripheral portion, as shown in FIGS.
It became 46 μm. The ratio of the peripheral portion being thicker than the central portion is suppressed to about 25%.

[0042]

As described above, according to the invention of claim 1, it is possible to make the plating thickness of the substrate uniform without discarding a part of the substrate and wasting it.

[0043] According to the invention of claim 2, the plating thickness of the substrate can be made uniform more easily than in the case of using an auxiliary electrode without causing waste such as discarding a part of the substrate. I can do it.

According to the third aspect of the present invention, it is possible to effectively uniformize the plating thickness of the substrate without causing waste such as discarding a part of the substrate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the electrolytic plating method for a substrate according to the present invention.

FIG. 2 is a diagram showing the configuration of a holding frame in FIG. 1;

FIG. 3 is a diagram showing the positional relationship between an auxiliary electrode and a substrate viewed from the anode side in FIG. 1;

FIG. 4 is a diagram showing the flow of current in the plating solution in FIG. 1.

FIG. 5 is a diagram showing a combination of an auxiliary electrode and a conductive tape.

FIG. 6 is a diagram showing plating thicknesses corresponding to the combination of FIG. 5;

FIG. 7 is a diagram showing a second embodiment of the electrolytic plating method for a substrate according to the present invention.

8 is a diagram showing the configuration of the holding frame in FIG. 7. FIG.

9 is a diagram showing the flow of current in the plating solution in FIG. 7. FIG.

FIG. 10 is a diagram showing a third embodiment of the electrolytic plating method for a substrate according to the present invention.

11 is a diagram showing the flow of current in the plating solution in FIG. 10. FIG.

FIG. 12 is a diagram showing a general flow of current in a plating solution during electrolytic plating.

[Explanation of symbols]

10 Ceramic substrate 11 Holding frame 12 Anode 13 Auxiliary electrode 14 Main power supply 15 Auxiliary power supply 19, 31, 40 Current flowing in the plating solution 20, 3
2,41 Plated film 30 Conductive tape

Claims (3)

[Claims] 1. A frame-shaped auxiliary electrode (13) whose inner edge (13a) has substantially the same size as the substrate (10) to be electrolytically plated is attached to the anode (1) of the substrate (10).
The auxiliary electrode (13) is arranged near the surface (10a) facing the auxiliary electrode (10a) and surrounding the substrate when viewed from the anode side, and is configured to apply a negative voltage (V2) to the auxiliary electrode (13). A method for electrolytic plating of a substrate, characterized by: 2. A conductive tape (30) is placed on the side of the holding frame (11) that holds the substrate (10) to be electrolytically plated, which faces the anode (12).
A method for electrolytic plating of a substrate, characterized in that the conductive tape (30) is attached in a flexible and peelable manner, and a negative voltage (V1) is applied to the conductive tape (30). 3. A frame-shaped auxiliary electrode (13) whose inner edge (13a) has substantially the same size as the substrate (10) to be electrolytically plated is placed opposite to the anode (12) of the substrate (10). The auxiliary electrode (13) is provided with a negative voltage (V
A conductive tape (30) is placed on the surface facing the anode (12) of the holding frame (11) which holds the substrate (10) and which applies the voltage (2).
1. A method for electrolytic plating of a substrate, characterized in that the electrically conductive tape (30) is wrapped and removably adhered to the electrically conductive tape (30), and a negative voltage (V1) is applied to the electrically conductive tape (30).