JPS6112877A - Method for carrying out electroless copper plating - Google Patents

Abstract

PURPOSE:To improve the mechanical properties of a plated film as well as to increase the rate of plating by carrying out electroless copper plating under reduced pressure. CONSTITUTION:A body 9 to be plated is immersed in an electroless copper plating soln. 11 in a plating tank 10, and gaseous hydrogen 4 in the plating soln. 11 is exhausted with a vacuum pump 2. In the figure, 12 is a vacuum gauge. By the degassing, the mechanical properties of a copper film deposited by plating are improved, and the film is made free from defects such as blister and pits. An effect produced by raising the temp. of the plating soln. corresponds to that obtd. by reducing the pressure, so the rate of plating can be increased.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a method for electroless copper plating.

[Prior art and its problems]

Generally known copper plating methods include electroplating and electroless plating. For electroplating.

The cutting speed is very fast, which is why it is widely used industrially. However, in three-gas plating, it is not possible to directly plate an insulating material such as plastic, and it is necessary to perform electroplating after applying a thin electroless plating.

Furthermore, when electroplating a printed circuit that has many floating islands, electrodes must be provided on each floating island, which makes the work extremely troublesome.

” On the other hand, electroless plating does not require any electric field and can easily plate uniformly on printed circuits with many floating islands. However, electroless plating has an extremely slow plating speed compared to electroplating, and generally With commercially available plating solutions, the plating film formation rate is 1 μm per hour.
~3.5 μm. Therefore, 20 to 30 μm
If a thicker plate is required, the open plated item must be immersed in a plating solution for several to 30 hours. Further, hydrogen gas is generated as the chemical reaction progresses over time as the object to be plated immersed in the plating solution undergoes plating processing. This hydrogen gas has the disadvantage that the mechanical properties of the deposited copper plating film become brittle.

[Purpose of the invention]

The object of the present invention is to provide a method for electroless copper plating which eliminates the above-mentioned drawbacks and allows a fast plating rate and a plated film with good mechanical properties to be obtained.

[Summary of the invention]

The electroless copper plating method of the present invention performs electroless copper plating under reduced pressure, thereby deaerating the hydrogen gas contained in the electroless copper plating solution, thereby mechanically reducing the deposited copper plating film. In addition to improving properties and removing defects such as blisters and pits, reducing the pressure can achieve the same effect as increasing the plating temperature of the electroless copper plating solution. It is possible to increase the speed of attachment. This will be explained in more detail with reference to Examples below.

[Embodiments of the invention]

Table 1 shows the composition of the electroless plating solution used and the plating conditions. The following is Table 1: Electroless copper plating was performed using the above plating solution 51J under reduced pressure using the apparatus shown in FIG. 1, and the plating speed and mechanical properties were measured.

The apparatus used in the embodiments of the present invention will be explained based on the drawings.
Reference numeral 10 denotes an electroless copper plating bath, in which a banded object 9 is immersed in a plating solution 11. The plating solution 11 is supplied by a circulation pump l.
The plating solution is circulated by the th5Gt electroless copper plating controller, and in order to control the concentration and pH value of the solution consumed by the chemical reaction within the specified value range, the replenisher pump 6 pumps the replenisher solution 7. is injected into the circulating plating solution. 8 is a heat exchanger that adjusts the temperature to a predetermined temperature.

2 is a plating solution] A vacuum pump with a pumping speed of 307/min and an ultimate vacuum (Ton) of 5 x 10-' was used to release the hydrogen gas 4 contained in 1 to the outside air (the vacuum level was Macleord vacuum). 12 is a MacLeod vacuum gauge. 3 is a stirring device for promoting mixing of the plating solution. Also, the method for measuring mechanical properties is that the thickness is 0.
．． A 3 mm stainless steel plate was polished with a cleanser, immersed in a 10% concentrated sodium aqueous solution at 80°C for 5 minutes, taken out, washed with water, immersed in 10% hydrochloric acid for 5 minutes at room temperature, and washed with water. Cleaned the surface. The following is Table 2 of Kinpaku Table 3 Furthermore, the sample was immersed for 2 minutes in an aqueous solution of tin chloride acidified with hydrochloric acid shown in Table 2, and rinsed in running water for 1 minute.

Subsequently, the surface was catalyzed by immersing it in a palladium chloride solution acidified with hydrochloric acid shown in Table 3 for 1 minute and washing it in running water for 1 minute. Thereafter, various copper plating films having a plating film thickness of 20 to 50 μm were provided by immersing the test pieces in the plating solution shown in Table 1 under plating conditions of 60° C.% and pH 12.3. The resulting plating film was peeled off from the stainless steel plate, and a copper foil measuring 12.7 mm x 150 mm was accurately cut from it.

The mechanical properties (elongation rate (%) and tensile strength) of the plating film were measured using a tensile tester (manufactured by Takasu Seisakusho Co., Ltd., trade name, Autograph Model DBS-5000). The test conditions were a chuck interval of 109 mm for fixing the copper foil, and a pulling speed of 5 mm/min.

The results obtained are shown in Table 4.

Comparative Example The same treatment as in the example was carried out except that the pressure was not reduced, and the results obtained are also shown in Table 4.

Table 4 It can be seen from Table 4 that the mechanical properties of the electroless copper plating film can be significantly improved by reducing the pressure, and the plating speed can also be increased.

〔Effect of the invention〕

As mentioned above, the plating method of single-shot FIJl electroless copper plating increases the plating speed, and
The mechanical properties of the plating film can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a rear panel according to an embodiment of the present invention. l... Circulation pump, 2... Decompression pump, 3... Stirring device, 4... Hydrogen gas, 5... Electroless copper plating controller, 6... Replenisher pump %7... replenisher,
8... Heat exchanger, 9... To be plated, 10... Electroless plating tank, 11... Plating solution, 12... MacLeod vacuum gauge.

Claims (1)

[Claims] A plating method for electroless copper plating characterized by performing electroless copper plating while reducing pressure.