JPH07316828A - Electroless plating method - Google Patents

Abstract

PURPOSE:To provide an electroless plating method by which an abnormal reaction in the plating soln. is suppressed and the stability of the soln. is improved. CONSTITUTION:A concd. replenishment liq. is supplied into a plating soln. from an inlet pipe, and electroless plating is continuously conducted. In this case, the replenishment is supplied from the inlet pipe while preventing the backflow and mixed with the plating soln. Consequently, the diffusion efficiency of the replenishment is enhanced, and the deposition of copper hydroxide, etc., is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has improved a replenisher solution mixing method for supplying and replenishing replenisher solution so that the solution composition in a chemical treatment tank such as a plating tank is always controlled and adjusted within a certain range. The present invention relates to an electrolytic plating method.

[0002]

2. Description of the Related Art Electroless plating is carried out as a method of attaching a conductive material to the surface of a printed wiring board and through holes or imparting conductivity to a plastic surface. In this case, the solution composition of the plating bath is: Copper sulfate, sodium hydroxide, formaldehyde, Rochelle salt, EDTA and water are mixed. In order to deposit a good metal for imparting conductivity, the liquid composition of the solution must be within a certain concentration range, and if it exceeds the range,
The deposition rate of the plated metal becomes slow, the adhesion strength of the adhered metal is weakened, and the plating with an uneven thickness is performed. Solution control of the plating bath is important for good plating. By the way, the composition of the plating solution in the plating bath changes from moment to moment because a metal is deposited on the substrate, and the concentration of each solution exceeds a predetermined concentration unless supplemented. Therefore, the solution is managed by an automatic controller.

FIG. 3 shows a conventional electroless copper plating apparatus.

Electroless copper plating solution 3 in plating bath 31
2 overflows into the overflow tank 33, where it is maintained at a predetermined temperature by the heat exchanger 34, and is circulated to the plating treatment tank 31 from the circulation pipe 35 through the circulation pump 37 and the filter 38. Various replenishing liquid introducing pipes 39a, 39b, 39c are provided on the upper portion of the overflow tank 33 so that the lower ends thereof are immersed in the plating liquid 32 in the overflow tank 33, and the replenishing liquid is appropriately supplied to the overflow tank 33. To be done.

[0005]

[Problems to be Solved by the Invention] However, in the past,
The replenisher introduced from the replenisher introducing pipes 39a, 39b, 39c was intermittently replenished to the mixer 36 in a necessary amount. When the contact interface is formed and copper is deposited, copper oxide is adhered, or copper hydroxide is formed on the lower end portions of the replenishment liquid introduction pipes 39a, 39b, 39c, the replenishment liquid introduction pipe is not visible. The phenomenon of clogging occurred. Further, since the replenishing liquid introducing pipe is installed in the same portion, the replenishing overflow tank 33 is replenished when the replenishing liquid is discharged.
Precipitation of copper oxide and copper hydroxide occurs inside and in the circulation pipe 35, and these are trapped by the filter 38 to cause the generation of copper nuclei that cause clogging or are brought into the plating treatment tank 31. In some cases, it triggered a runaway reaction known as copper pretend.

Therefore, an object of the present invention is to provide an electroless plating method which solves the above-mentioned drawbacks of the prior art, suppresses an abnormal reaction in the plating solution, and improves the stability of the plating solution. .

[0007]

In order to achieve the above object, the present invention provides an electroless plating method in which a high-concentration replenisher is supplied from a replenisher-introducing pipe into a plating solution and continuously operated. This is an electroless plating method in which a high-concentration replenisher is supplied from a pipe into the plating solution while preventing backflow and is mixed with the plating solution and supplied.

[0008]

According to the above construction, the replenishing solution from the replenishing solution introducing pipe is mixed with the plating solution through the mixer and supplied, thereby increasing the diffusion rate into the plating solution and, as a result, the stability of the plating solution. Can be increased. Further, since the backflow of the replenisher into the replenisher introducing pipe can be prevented, there is no problem even if the replenisher is intermittently supplied.

[0009]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, 1 is a plating tank,
The electroless plating solution 2 is filled. An overflow bath 3 is provided on one side of the plating bath 1, and the plating solution 2 overflowing from the plating bath 1 flows into the overflow bath 3.

A heat exchanger 4 for adjusting the temperature of the plating solution 2 is provided in the overflow tank 3. A circulation pipe 5 for returning the plating solution 2 in the overflow bath 3 to the plating bath 1 is connected to the bottom of the overflow bath 3, a circulation pump 7 is connected to the circulation pipe 5, and a filter 8 is connected to the discharge side. It

In the present invention, the circulation pipe 5 is
For example, the mixer 6 is connected to the suction side of the circulation pump 5,
The mixer 6 is provided with various replenisher introduction pipes 9a, 9b, 9
c is connected.

This mixer 6 and replenishing liquid introducing pipes 9a, 9
b and 9c may be connected to the circulation pipe on the discharge side or may be connected to the overflow tank 3.

This mixer 6 and replenishing liquid introducing pipes 9a, 9
Details of b and 9c will be described with reference to FIG.

First, the mixer 6, for example, the circulation pipe 5
A scree-shaped blade 6a is provided in the inside, and three systems of replenisher introducing pipes 9a, 9b, 9 are provided along the blade 6a.
c is connected and check valves 10a, 10b and 10c for preventing backflow are connected to the outlet sides of the introduction pipes 9a, 9b and 9c.

From these introducing pipes 9a, 9b, 9c, copper ions, formalin, consumed in the electroless copper plating reaction,
Components such as sodium hydroxide are supplied to the mixer 6.

Next, the operation of the embodiment will be described.

First, the excess plating solution 2 in the electroless plating tank 1 flows into the overflow tank 3 in which the heat exchanger 4 is installed, passes through the circulation pipe 5, and in the mixer 6 portion,
Plating solution replenisher is a three-system replenisher introduction pipe 9a, 9b, 9
It flows between the blades 6a of the mixer 6 by the c, is mixed with the plating solution there, and is then sent to the filter 8 by the circulation pump 7, where it is further mixed and supplied in a uniform state, and the plating is performed. The composition concentration of the plating solution in the bath is kept constant, which allows good electroless plating.

The present invention is not limited to the above-mentioned embodiment, and the mixer 6 to which the replenisher introducing pipes 9a, 9b, 9c connected to the circulation system of the plating solution 2 are connected is installed at Any part is fine. That is, it may be placed before or after the circulation pump 7 or before the filtration filter 8 for the plating solution. In this case, the diffusion of the replenisher can be further enhanced. Regarding the relationship between the replenisher introducing pipe and the mixer, one mixer may be provided for each replenisher introducing pipe, or a mixer may be provided corresponding to all the replenisher introducing pipes. Regarding the relationship between the mixer section and the plating solution circulation pipe, the circulation pipe is made into one circulation system, and a mixer is connected in series to this circulation pipe,
The circulation pipe in the circulation system may be branched midway and a mixer may be connected to each.

[0020]

In summary, according to the present invention, when the circulating plating solution is replenished with the replenishing solution, the replenishing solution is mixed and supplied to the plating solution through the mixer to improve the diffusion efficiency. It is possible to prevent the precipitation of copper hydroxide and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a detailed view showing a main part of FIG.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Plating tank 2 Plating solution 3 Overflow tank 5 Circulation pipe 6 Mixer 7 Circulation pump 9a, 9b, 9c Replenisher introduction pipe 10a, 10b, 10c Check valve

Front page continuation (72) Hideki Asano Inventor Hideki Asano 5-1-1 Hidakacho, Hitachi City, Ibaraki Hitachi Power Systems Laboratory

Claims (1)

[Claims] 1. In an electroless plating method in which a high-concentration replenisher is supplied into a plating solution from a replenisher-introducing pipe to continuously operate, a high-concentration replenisher is plated from the replenisher-introducing pipe while preventing backflow. An electroless plating method characterized in that it is supplied into a solution and is mixed with a plating solution before being supplied.