JPS5826427B2 - Electroless copper plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroless copper plating method used for continuous operation of an electroless copper plating solution.

Conventionally, printed wiring boards used copper-clad laminates and removed unnecessary parts by etching to form wiring patterns, but in order to save resources and energy, copper is plated only on the necessary patterns on the board. This has become a requirement.

Electroless copper plating was developed to meet these demands.

Electroless copper plating is an alkaline copper ion complex solution that uses formalin as a reducing agent to deposit metallic copper on a plating catalyst (PD) or copper surface.

In order to operate electroless copper plating solution stably and continuously,
It is necessary to replenish the components consumed by copper precipitation with a new high-concentration replenisher to keep the composition constant.

1 to 3 show a conventional electroless copper plating apparatus (FIGS. 2 and 3 are enlarged views of section A in FIG. 1).

), In the figure, 1 is the plating tank, 2 is the circulation pipe, 3 is the circulation pump, 4 is the filter, 5 is the replenisher addition pump, 6 is the replenisher introduction pipe, 7 is the □ kisser 18 is the replenisher tank, 9 is the replenisher tank. In the controller, 1° is a replenisher, and 11 is a stationary interface between the replenisher and the plating solution.

Conventionally, such a device replenishes the required amount of replenisher intermittently, so that during the period when replenisher is not being discharged, the stationary contact interface 11 between the high concentration replenisher and plating solution as shown in FIG. is formed and a local runaway reaction occurs,
As shown in Figure 3, phenomena such as copper depositing at the tip of the replenisher inlet tube12, copper oxide adhering13, or copper hydroxide forming and clogging the replenisher inlet tube14. There has occurred.

Furthermore, when such copper oxides and copper hydroxides are brought into the plating bath, they trigger a runaway reaction known as steel plating.

The present invention has been made in view of the above points, and includes: A. A replenisher supply device having a circulation pipe for circulating the plating solution as necessary; B. A replenisher supplying device having a replenisher introduction pipe opened into the plating solution. In an electroless copper plating apparatus, a constant amount of replenisher smaller than the theoretical average consumption amount is continuously supplied to the replenisher inlet pipe, and a required amount of replenisher is intermittently supplied to the replenisher inlet pipe at a steady state. It is characterized in that it is added to the flow path of the replenisher that flows.

That is, in the electroless plating apparatus of the present invention, the replenisher is divided into continuous addition and intermittent addition, and the supply ports to the plating solution are the same.

FIG. 4 is a system diagram showing the piping of the replenisher supply device used in the electroless plating method of the present invention, where 2 is a circulation pipe, 5 is a replenisher addition pump, 6 is a replenisher introduction pipe, and 8 is a replenisher. A liquid tank, 9 a controller, and 15 a replenishment liquid addition pump.

The replenisher addition pump 15 is always on, and a fixed amount of replenisher smaller than the theoretical average consumption amount is always supplied to the replenisher introduction pipe.

The replenisher addition pump 5 is turned on as needed and operates so that the required amount of replenisher is added to the replenisher inlet pipe.

In the above explanation, the replenisher inlet pipe opened into the plating solution in the circulation pipe, that is, the replenisher was added into the circulation pipe, but the replenisher inlet pipe opened into the plating tank. The present invention can also be used when the replenisher is directly inserted into the plating solution in the plating tank and the replenisher is added directly to the plating tank.

EXAMPLE An electroless copper plating solution was continuously operated for 24 hours using the replenisher supply device shown in FIG.

The flow rate in the pipe is 100 Umin, the amount of replenisher constantly supplied is 10 d/l, and the amount of replenisher intermittently supplied is 1 d/l at most.
0077271! /m1ns The total amount of plating solution is 70ot, and the plating solution composition is PH120XCuSO4・5H2
°10? / 4 EDTA 30? /l, NaC
N307nf; 71/AGAFAC-RE-610 (trade name, surfactant manufactured by Toho Chemical Industry Co., Ltd.) 0.25td/l
, HCHO6d/l and the temperature is 72°C.

After the operation was completed, the tip of the replenisher inlet pipe was examined, and it was found that copper hydroxide, copper hydroxide,
No adhesion of copper oxide or precipitation of copper was observed, and no copper splatter occurred even with the entire old stamina solution.

In the conventional replenisher addition method, copper hydroxide or copper oxide adheres to the tip of the replenisher inlet tube, or copper precipitates, resulting in clogging of the replenisher outlet or fine particles of copper hydroxide or copper oxide. There were problems such as floating in the liquid and becoming the core of a runaway reaction, reducing the stability of the liquid.

If a high concentration replenisher is refilled for 2 minutes and then stopped for 10 minutes, the replenisher supply pipe will be damaged after 1.5 hours.
Precipitation of copper hydroxide and copper oxide was observed at the tip of the copper sulfate solution and alkali supply pipe.

However, according to the method of the present invention as explained above, there is no stationary interface between the replenisher and plating solution, and there is no local runaway reaction at the tip of the replenisher introducing tube, so clogging and clogging in this part can be prevented. This did not occur at all, and the stability of the liquid was also improved.

[Brief explanation of the drawing]

Figures 1 to 3 are cross-sectional views of conventional electroless copper plating equipment.
FIG. 4 is a system diagram of the replenisher supply system piping used in the electroless copper plating apparatus of the present invention. Explanation of symbols 1...Plating tank, 2...Circulation pipe,
3... Circulation pump, 4... Filter, 5... Replenisher addition pump, 6... Replenisher introduction pipe, 7... Kisser 18... Replenisher tank, 9... Controller ,1
0... Replenisher, 11... Replenisher-plating liquid stationary interface, 12... Precipitated copper, 13... Adhered copper oxide, 14
...Clogged copper hydroxide, 15...Replenisher addition pump.

Claims (1)

[Claims] 1. In an electroless copper plating method that operates continuously while supplying high-concentration replenisher into the plating solution through a replenisher inlet pipe opened into the plating solution, a fixed amount smaller than the theoretical average consumption is added to the replenisher inlet pipe. The high-concentration replenisher is supplied by continuing to flow the replenisher and adding a required amount of replenisher intermittently to the replenisher flow path that is constantly flowing through the replenisher introduction pipe. Electroless copper plating method.