JPH0959780A - Electroless plating method and electroless plating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the abnormal deposition of plating and to maintain the dissolved oxygen in uniform and high concn. by agitating an electroless-plating soln. with air, generating fine air and increasing the concn. of dissolved oxygen. SOLUTION: A material to be plated is dipped in an electroless-plating soln. 12 contained in a plating tank 11 to form a metallic layer on the surface and in the through hole. The soln. 12 is agitated with air through an air agitating pipeline 16 perforated with many holes 17 during the plating to generate fine air in the soln. 12. The fine air is generated by installing a mixer 15 in the external circulating passage 13 furnished with a circulating pump 8, a filter F, etc., supplying air to the mixer from an air pump 14 and injecting the air into the bottom of the plating tank along with the soln. Further, a dissolved oxygen measuring device is arranged and the supply of air is preferably controlled based on the measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating method and apparatus, and more particularly to an electroless plating method and an electroless plating apparatus for forming a metal layer on a surface of a plastic molded product, a through hole of a printed wiring board or the like. is there.

[0002]

2. Description of the Related Art Conventionally, there is known an electroless plating method in which an object to be plated is dipped in an electroless plating solution to form a metal layer on the surface of the object to be plated or through holes. It is used for manufacturing a printed wiring board having the above and a plastic molded product having a patterned metal layer.

In electroless plating, there is known a method for stabilizing the plating solution by blowing oxygen-containing gas such as air into the plating solution for the purpose of preventing self-decomposition of the plating solution. As shown in FIG. 4, there is known a plating apparatus in which an electroless plating solution 12 is contained in a dipping bath 11, a small hole 17 is provided in an air stirring pipe 16 at the bottom of the bath, and bubbles are supplied through the small hole 17.

[0004]

However, when the apparatus as described above is used, the concentration of dissolved oxygen in the plating solution varies greatly. For example, if the oxygen concentration is low,
Abnormal precipitation occurs in areas other than the wiring pattern area where plating wiring density is high, or precipitation occurs in areas below the piping at the bottom of the plating tank, the bottom of the plating tank, sidewall recesses, etc. where air bubbles do not come into direct contact with the piping. Cheap. On the contrary, when the oxygen concentration is high, there is a problem that the plating reaction of the independent fine land portion is stopped especially in a printed circuit board having a fine wiring. Further, in the case of a plating apparatus having such a structure, since the bubble diameter is large, the plating solution is vigorously agitated, the substrate to be plated is touched with the jig or the adjacent substrate, and non-precipitation of plating or other than the pattern part is caused. There was also a problem of causing abnormal precipitation in the.

In view of the above problems, an object of the present invention is to provide an electroless plating method and an electroless plating apparatus capable of preventing abnormal deposition of plating and maintaining a high concentration and a constant dissolved oxygen concentration.

[0006]

In order to achieve the above object,
The electroless plating method according to the present invention is an electroless plating method of immersing an object to be plated in an electroless plating solution to form a metal layer on the surface or through holes of the object to be plated,
During the electroless plating treatment, the dissolved oxygen concentration in the electroless plating solution is increased by agitating the electroless plating solution contained in the dipping tank by air agitation and generating fine air. is there. Further, it is preferable to control so that the dissolved oxygen concentration becomes constant.

In the electroless plating apparatus according to the present invention, a small hole is provided in the air agitation pipe at the bottom of the dipping tank, and an air pump and a mixer are provided in the circulation passage returning from the external circulation passage to the electroless plating apparatus. It is a thing.

The electroless plating apparatus is provided with a dissolved oxygen measuring device, and the dissolved oxygen concentration measured by the dissolved oxygen measuring device is converted into an electric signal to control the concentration, and the opening degree is adjusted. It is preferable to provide a solenoid valve that adjusts to control the amount of air.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electroless plating method and an electroless plating apparatus according to the present invention will be described below with reference to FIGS. 4 shows a conventional electroless plating apparatus as a comparative example.

(Embodiment 1) The electroless plating method of Embodiment 1 is performed by the following electroless plating apparatus. FIG.
Shows an electroless plating apparatus of the present embodiment. The electroless plating apparatus 1 is provided with a dipping bath 11, and the dipping bath 11 contains components for forming a desired metal layer. The electroless plating solution 12 included therein is accommodated, and an air stirring pipe 16 is provided at the bottom of the tank.

External circulation channel 13 of electroless plating apparatus 1
Is provided with a circulation pump 6, a filter 7, and a mixer 15. The air sent from the air pump 14 is atomized by the mixer 15, mixed with the electroless plating solution 12 in the external circulation channel 13, and immersed again. It is discharged from the bottom of the tank 11. Further, a large number of holes 17 are provided in the air agitation pipe 16 at the bottom of the tank, and a bubble flow composed of a large number of bubbles is generated from this hole 17.

(Embodiment 2) The electroless plating method of Embodiment 2 uses an electroless plating apparatus in which a dissolved oxygen measuring device 21 is provided in the electroless plating apparatus of FIG. 1 as shown in FIG.

(Embodiment 3) In the electroless plating method of Embodiment 3, as shown in FIG. 3, in the electroless plating apparatus of FIG. 2, the dissolved oxygen concentration measured by the dissolved oxygen measuring device 21 is converted into an electric signal. The electroless plating apparatus provided with the control device 22 for controlling the concentration and the solenoid valve 23 for controlling the air amount by adjusting the opening degree is used.

Experiments were conducted using the electroless plating apparatus shown in the above Examples 1 to 3 and the conventional electroless plating apparatus (FIG. 4) as a comparative example. The experimental method is as follows.

As the object to be plated, a plastic molded product is obtained by first molding a liquid crystal polymer in which a catalyst for electroless copper plating is kneaded and then secondary molding with a difficult-to-plate resin (polyphenylene sulfide) so as to leave a pattern portion (see FIG. 5) was used. Then, a wet treatment step of chemically roughening the surface of this plastic molded product was performed. In particular,
After degreasing with an alkaline cleaner, this was etched by immersing it in a mixed liquid of 98% sulfuric acid: 300 ml / l and 36% hydrochloric acid: 130 ml / l at 30 ° C. for 15 minutes. After that, wash with water, alkali treatment,
Washing with water, neutralization and washing were carried out in sequence.

Next, a plating step of forming a metal layer on the surface of the plastic molded article after the wet treatment by electroless plating is performed. For this electroless plating, electroless copper plating is adopted, and the plating bath uses an aqueous solution of copper sulfate, formaldehyde, sodium hydroxide, ethylenediamine tetraacetate (EDTA) and 2-2 'dipyridyl, polyethylene glycol, etc. Then, it was heated to 72 ° C. and adjusted to PH: 12.3. A pretreated plastic molded product was dipped in this plating bath through a wet treatment process, and electroless copper having a thickness of 40 μm was deposited on the surface thereof.

The results obtained by the above method are shown in Table 1.

[0018]

[Table 1]

As described above, in the comparative example, the abnormal deposition was extremely large in both the plating apparatus and the molded product, while in Examples 1 to 1
In No. 3, abnormal deposition of plating did not occur, and the effect of the present invention was remarkable. In Example 2, the dissolved oxygen concentration tended to decrease with the lapse of plating time, but in Example 3, the concentration was measured by the dissolved oxygen measuring instrument, and the control device and the solenoid valve were controlled based on the result. By doing so, it was possible to maintain a consistently high concentration from the start to the end of plating.

[0020]

EFFECTS OF THE INVENTION According to the present invention, the electroless plating solution is agitated by air agitation, and fine air is generated to increase the dissolved oxygen concentration, thereby preventing abnormal deposition of plating on the plating apparatus and the molded product. You can hold it down.

Further, by providing a dissolved oxygen measuring device, a control device and a solenoid valve in the electroless plating apparatus, a high concentration and a constant dissolved oxygen concentration can be maintained.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an electroless plating apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing an electroless plating apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic explanatory view showing an electroless plating apparatus according to a third embodiment of the present invention.

FIG. 4 is a schematic explanatory view showing a conventional electroless plating apparatus.

FIG. 5 is a schematic view showing a plastic molded product used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating apparatus 6 Circulation pump 7 Filter 11 Plating tank 12 Electroless copper plating solution 13 External circulation flow path 14 Air pump 15 Mixer 16 Air stirring pipe 17 Hole 21 Dissolved oxygen measuring instrument 22 Control device 23 Solenoid valve 31 Plastic molded product 32 Difficult-to-plate resin 33 Catalyst-containing resin

Claims (5)

[Claims] 1. An electroless plating method in which an object to be plated is dipped in an electroless plating solution to form a metal layer on the surface of the object to be plated or through holes, and the object is placed in a dipping tank when the electroless plating treatment is performed. The above electroless plating solution is agitated by air agitation, and fine air is generated to increase the dissolved oxygen concentration in the electroless plating solution. 2. The electroless plating method according to claim 1, wherein the dissolved oxygen concentration is controlled to be constant in the electroless plating method. 3. An electroless plating apparatus for forming a metal layer on the surface or through holes of an object to be plated by immersing the object to be plated in an electroless plating solution contained in an immersion tank, and stirring the air at the bottom of the immersion tank. An electroless plating apparatus, characterized in that a small hole is provided in a pipe for use, and an air pump and a mixer are provided in a circulation channel returning from an external circulation channel to the electroless plating apparatus. 4. The electroless plating apparatus according to claim 3, wherein a dissolved oxygen measuring device is provided in the electroless plating apparatus. 5. In the electroless plating apparatus, a controller for converting the dissolved oxygen concentration measured by the dissolved oxygen measuring device into an electric signal to control the concentration, and a solenoid valve for adjusting the opening to control the air amount. The electroless plating apparatus according to claim 3, wherein the electroless plating apparatus is provided.