JP3038876B2 - Electroless copper plating bath stirring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electroless copper plating bath which activates an electric insulating material with a catalyst solution and coats the surface of the electric insulating material with metal by electroless copper plating. It relates to a stirring method.

[Conventional technology]

Generally, in the electronics industry, the surface of a plastic material is widely covered with metal by electroless plating to make it conductive. For example, in the production of a printed wiring board, after forming a through hole at a desired position on the surface of a copper-clad epoxy resin laminate, a catalyst solution is adsorbed on the through hole wall, and then the through hole wall is formed by electroless copper plating. Apply metal coating,
Making the wall surface of the through hole conductive has been performed.

Conventionally, air stirring has been widely used as a stirring method for an electroless copper plating bath. In this air stirring method, as shown in FIG. 3 (a), mutually connected pipes 6, 6,... Are arranged in parallel on the inner bottom of the plating tank 4, and each pipe 6 is opened on the upper peripheral surface. Air is blown out from the air outlet into the plating tank 4 to stir the catalyst solution. According to this air stirring method, air stirring during plating in the plating tank 4 stabilizes the dissolved oxygen concentration in the bath. Thus, there is an advantage that the bath can be kept stable without being decomposed, and a normal plating reaction can proceed.

[Problems to be solved by the invention]

The conventional electroless copper plating bath stirring method described above has the following disadvantages because the dissolved oxygen concentration must be maintained in a stable state that does not render the bath inactive. (1) Immediately after the bathing of the plating solution, the dissolved oxygen concentration has reached saturation, and the electroless copper plating solution is inactive. Therefore, as shown in FIG. By introducing the dummy plate 5 in a state where the plating is not performed, the concentration of dissolved oxygen must be reduced over several hours to activate the plating solution. For this reason, in a thin electroless copper plating line in which products are sequentially supplied according to the cycle time, several cycles of dummy input are required, and wasteful costs are generated.

(2) When the air flow rate of the air stirring is set to be constant, in order to stabilize the dissolved oxygen concentration at a constant amount, the load factor of the object to be plated must be constant.

And the like.

An object of the present invention is to provide an electroless copper plating bath stirring method for controlling the concentration of dissolved oxygen in a plating tank.

[Means for solving the problem]

In order to achieve the above object, an electroless copper plating bath stirring method according to the present invention includes a gas blowing step and a concentration control step, and is an electroless copper plating bath stirring method for stirring a plating solution in a plating tank. The gas blowing step is performed in a region above each of a nitrogen gas pipe disposed at the center of the inner bottom surface in one plating tank and an air pipe disposed to surround the outer periphery.
Nitrogen gas is blown out of the nitrogen gas pipe, air is blown out of the air pipe, and the gas is stirred in the plating solution using the nitrogen gas and the air together. The concentration control step is performed by the nitrogen gas pipe and the air pipe. Two different regions corresponding to the upper region of each of the above, corresponding to a dissolved oxygen low concentration region by nitrogen gas in the center part of the plating tank and a dissolved oxygen high concentration region by air in contact with the inner surface of the plating tank. Is formed in one plating tank.

[Action]

Gas stirring is performed with air and nitrogen gas to control the dissolved oxygen concentration in the plating tank, and by this control, a region having a high and low dissolved oxygen concentration is created in the plating tank.

〔Example〕

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

(Example 1) Fig. 1 is a perspective view showing a plating tank using an electroless copper plating bath stirring method according to one example of the present invention.

In the figure, a nitrogen gas pipe 1 is a combination of horizontal pipes 1a, 1a ... arranged in parallel and vertical pipes 1b, 1b communicating both ends of a plurality of pipes 1a, 1a ... The pipe 1 is provided at the center of the inner bottom surface of the plating tank 3.

The air pipe 2 is provided between a horizontal pipe 2a installed between the horizontal pipe 1a of the nitrogen gas pipe 1 and the inner surface of the plating tank 3 and an inner surface of the plating tank 3 of the vertical pipe 1b of the nitrogen gas pipe 1. The air pipe 2 surrounds the outside of the nitrogen gas pipe 1 existing at the center of the inner bottom surface of the plating tank 3. It is arranged as follows.

Each pipe 1a, 1 used for nitrogen gas pipe 1 and air pipe 2
For b, 2a, 2b, for example, use a thing made of vinyl chloride having a diameter of 8 mm, and in each pipe 1a, 1b, 2a, 2b, an outlet for blowing nitrogen and air opens downward at an angle of 45 °. The interval between the pipes 1a, 1b, 2a, 2b at the inner bottom of the plating tank 3 is set to 5 cm.

The dissolved oxygen concentration was 2 mgdm ^-3 at a height of 20 cm in the height direction of the plating tank 3 from the outlet of the nitrogen gas pipe 1, and a height of 20 cm from the outlet of the air pipe 2 in the height of the plating tank 3. 5 mgdm ^{-3 at the} position.

Here, nitrogen gas is supplied from the nitrogen gas pipe 1 to the air pipe 2
When air is blown into the plating solution in the plating tank 3 from above, the nitrogen gas pipe 1 is arranged at the center of the bottom of the tank and the air pipe 2 is arranged outside the nitrogen gas pipe 1. As shown in FIG. 2 (a), the flow is regulated mutually, and as shown in FIG. 2 (a), the outer square of the nitrogen gas pipe 1 at the center of the plating tank 3 has a bottom surface, and is within a rectangular shape in the height direction. Region A where nitrogen gas is blown out and dissolved oxygen concentration is low during stirring
On the other hand, as shown in FIG. 2 (b), air is blown out between the outer peripheral side of the rectangular shaped region A having a low dissolved oxygen concentration and the inner surface of the plating tank 3 and dissolved during stirring. A region B having a relatively high oxygen concentration is formed.

When the stirring was performed under the above conditions, as shown in FIG. 4, the distribution of the dissolved oxygen index in the plating tank 3 was, assuming that the area at the tank end, that is, the area where air was blown out from the air pipe 2 was 100%, the tank central part, In the region where the nitrogen gas is blown out from the nitrogen gas pipe 1, the ratio becomes about 40%.

 Next, the present stirring method will be described with reference to FIG.

Nitrogen gas is blown out from the nitrogen gas pipe 1 to the center of the plating tank 3 to agitate the plating solution with the nitrogen gas, and air is blown out from the air pipe 2 around the nitrogen gas pipe 1 to remove By controlling the dissolved oxygen concentration in the plating tank 3 to form a dissolved oxygen high concentration region B in contact with the inner surface of the plating tank 3,
A dissolved oxygen low concentration region A is formed in the center of the plating tank 3.

Since the area A in FIG. 2A is an area on the nitrogen gas pipe 1, the concentration of dissolved oxygen is reduced during stirring, and the electroless copper plating solution is kept active. Since the region B in FIG. 2B is a region on the air pipe 2, the concentration of dissolved oxygen is relatively high during stirring, and the electroless copper plating solution is inactive compared to FIG. 2A. Keep in.

As described above, by using the present stirring device, two regions having different dissolved oxygen concentrations can be provided in one tank.

When performing the electroless copper plating by the stirring method of the present invention, after the pretreatment step, a jig is put into the low-concentration dissolved oxygen region A shown in FIG. And electroless copper plating.

(Example 2) In this example, the nitrogen gas pipe 1 and the air pipe 2 are made of 100 mmφ made of vinyl chloride, and nitrogen gas and air outlets are provided in the horizontal direction of 90 °. 10cm. Further, the dissolved oxygen concentration, nitrogen gas 2.5Mgdm ^-3 through the outlet of the pipe 1 at a height of 20cm, is obtained by a 4Mgdm ^-3 in height likewise 20cm from the air outlet of the air pipe 2.

According to this embodiment, the same effects as those of the first embodiment can be obtained.

〔The invention's effect〕

As described above, the present invention performs gas agitation having two regions of a dissolved oxygen low concentration (active) region by nitrogen gas and a dissolved oxygen high concentration (inactive) region by air in one tank, It has the following effects: That is, (1) Since the bath has a stirring region by nitrogen gas, even if the dissolved oxygen concentration of the bath has reached saturation immediately after the bath is built, the concentration can be reduced and the bath can be activated. This gives 1
It is possible to omit the dummy activity of the 1st bath.

(2) Since the stirring is performed with the two regions of the nitrogen gas and the air, the activation with only the nitrogen gas proceeds, and the bath is not decomposed, and the bath is kept stable as a whole.

(3) Since the area in which the jig is inserted always maintains its activity, there is no need to adjust the input amount by the load factor.

(4) Since the dissolved oxygen high concentration (inactive) area is in contact with the tank, there is no deposition of metallic copper in the tank, and the etching frequency of the tank after plating is once / one bath to once / five times. Can be reduced with bath.

It has the effect of.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a plating tank using an electroless copper plating bath stirring method according to one embodiment of the present invention.
(B) is a diagram showing two regions having different dissolved oxygen concentrations when the inside of the tank is agitated by the piping of FIG.
FIGS. (A) and (b) are diagrams showing a conventional stirring method, and FIG. 4 is a distribution diagram showing a dissolved oxygen index in a plating tank. 1 ... Nitrogen gas piping, 2 ... Air piping 3 ... Plating tank A ... Dissolved oxygen low concentration region B ... Dissolved oxygen high concentration region

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 18/16-18/52

Claims (1)

(57) [Claims] 1. A method according to claim 1, further comprising a gas blowing step and a concentration controlling step.
A method of stirring an electroless copper plating bath for stirring a plating solution in a plating tank, wherein the gas blowing step surrounds a nitrogen gas pipe disposed in a central portion of an inner bottom surface in one plating tank and an outer periphery thereof. A step of blowing nitrogen gas from a nitrogen gas pipe and air from an air pipe into a region above each of the air pipes disposed in the gas pipe and performing gas agitation of the plating solution using the nitrogen gas and the air together. The concentration control step corresponds to a region above each of the nitrogen gas pipe and the air pipe, and a dissolved oxygen low-concentration region due to nitrogen gas in a central portion of the plating tank and the plating tank. A method for agitating an electroless copper plating bath, comprising a step of forming two regions in contact with a side surface, which are different from a region of high concentration of dissolved oxygen due to air, in one plating tank.