JPS58120774A - Electroless plating method - Google Patents

Abstract

PURPOSE:To form uniform plating layers even when there is a time between sticking of catalysts and electroless plating in the stage of forming conductive layers on insulation substrates by elecroless plating by sticking the plating catalysts on the substrates then heat treating the substrates and applying electroless plating thereon. CONSTITUTION:In the stage of forming conductive layers of circuit patterns on insulating substrates by an electroless plating method, first the substrates are treated with solns. contg. Sn and Pd compds. in order to form plating catalysts along circuit patterns, whereby the plating catalysts of metallic Pd are formed on the circuit patterns. Thereafter, the substrates are dipped in electroless plating solns. of Cu, Ni, etc., whereby plating layers of Cu and Ni are formed. If there is a considerable time between the stage for sticking the plating catalysts and the stage for electroless plating, the substrates are heated to >=80-90 deg.C after sticking of the plating catalysts to reactivate the activity of the plating catalysts degraded with time; thereafter, the substrates are subjected to the electroless plating to allow the plating metal to deposit uniformly.

Description

[Detailed Description of the Invention] Formation of a conductive layer by electroless plating is used to form a circuit pattern on an insulating substrate surface or to make an insulating substrate surface conductive (
It is widely practiced.

Electroless plating is generally performed after depositing a plating catalyst on the surface of an insulating substrate as a pretreatment.

By the way, in the past, there was no problem if electroless plating was performed immediately after depositing the plating catalyst, but if electroless plating was performed after a considerable amount of time had passed after the plating catalyst was deposited, problems often occurred. A phenomenon occurs in which metal is not deposited uniformly on the part where the plating catalyst is attached.

The main object of the present invention is to solve this problem and provide an electroless plating method in which metal is deposited uniformly on the plating catalyst adhesion area even if the plating catalyst adhesion process and the electroless plating process are performed at a certain time. purpose.

The electroless plating method according to the present invention includes a step of attaching a plating catalyst to the surface of an insulating substrate, a step of performing heat treatment before the electroless plating step, and a step of forming a conductive layer on the part to which the plating catalyst is attached by electroless plating. It is characterized by this.

That is, the present invention accomplishes the intended purpose of the present invention by performing heat treatment before the electroless plating process.

During electroless plating by heat treatment, metal can be uniformly deposited on the plating catalyst attachment area because the activity of the plating catalyst, which has decreased over time after the plating catalyst has been attached, is reduced by heat treatment. It is thought that this is because the state 1M#'c of the plating catalyst adhesion can be recovered.

The temperature conditions for heat treatment are determined as appropriate, but are usually 80°C.
The above temperature is particularly preferably 90°C or higher. In addition, from the point of view of restoring the activity of the plating catalyst, the heat treatment should be carried out at a time when the interval between the plating catalyst adhesion process and the electroless plating process, or the interval between the drying process of the metal resist pattern and the electroless plating process is 2.
It is suitable for processes lasting more than 8 hours, especially 8 hours or more.

Various conventionally known methods can be used for the plating catalyst adhesion treatment and electroless plating treatment. These methods are described in detail, for example, in the literature, "Electroless Plating" by Satoshi Ishibashi (published by Asakura Shoten), pages 151-164. Here, we will introduce a typical method (to explain a short method), which is immersed in a tinny chloride solution that is evenly distributed over the insulating substrate surface as a plating catalyst to facilitate metal deposition by electroless plating on the insulating substrate surface. Then, reducing Sn is adsorbed onto the surface of the substrate, and then it is immersed in a palladium chloride solution, whereby metallic palladium is distributed on the surface due to the reducing action of the previously adsorbed Sn. Mixed solution of tin 101 and hydrochloric acid 40 mj/l and palladium chloride 0.51 and hydrochloric acid 10 x
It is treated with a mixed solution of ne/l. After that, electroless plating is performed in a plating bath. The components contained in the plating bath vary depending on the type of plating, but generally include nickel sulfate, sodium citrate, sodium hypophosphite, and sodium acetate as main components. For example, one of the compositions of a plating solution for depositing copper is shown below.

Sulfuric acid steel 29 t/1 Sodium carbonate 25 Potassium sodium tartrate 140 #EDTA) Reethanolamine 17-Kanaiso soda
40 〃57b formalin solution 166 #
Further, one of the compositions of a plating solution for depositing nickel is shown below.

Nickel sulfate 35 tel Sodium citrate 10 # Sodium acetate
10 Sodium hypophosphite
15 g/l magnesium sulfate
20.

The type of metal to be deposited is not particularly limited, but
In practice, copper, nickel, @, gold 9, etc. are often used. The thickness of the conductive film is usually set to about 0.2 to 05 μm.

When forming a conductive layer on the entire surface of an insulating substrate by the electroless plating method according to the present invention, it is sufficient to deposit a plating catalyst on the entire surface, but it is also possible to form the conductive layer in a pattern to form printed circuits or patterned electrodes. In this case, it is necessary to also attach or expose the plating catalyst in a pattern.

The method for depositing this pattern is to form a patterned plating resist layer on the surface of the substrate, and to selectively form the plating catalyst on the areas where the plating resist layer is not formed due to the water repellent action of the plating resist. Plating catalyst can be attached.

In other methods, a plating catalyst is deposited on the entire surface of the substrate, and then a patterned plating resist layer is formed on top of the plating catalyst, so that the plating catalyst is exposed in areas not masked by the plating resist layer. The plating catalyst can be formed in a pattern. In particular, the latter method
Since the plating catalyst in areas where metal deposition is not required is masked with a metal resist, a highly accurate conductive pattern can be formed by electroless plating.

Example paper phenol laminate (manufactured by Toshiba Chemical Co., Ltd., trade name: T
LB-332) <Phenol-modified nitrile rubber was applied and cured by heating at 180°C for 60 minutes to form a subbing resin layer. Next, chromic acid-sulfuric acid mixture (Crys is 10
0 g/l, 98-sulfuric acid in 100 ml/l)
After roughening the undercoat resin layer by immersion treatment at 0°C for 6 minutes,
After washing with water, add 20% of gold to hydrochloric acid (35% HCl 2 times ml/l).
It was immersed at ℃ for 5 minutes and washed with water.

Next, palladium-tin colloid solution (product name: MK
-220, manufactured by Muromachi Kagaku Co., Ltd.) K Soaked at 20°C for 6 minutes, washed with water, and further immersed in hydrochloric acid solution (trade name: MK-330, manufactured by Muromachi Kagaku Co., Ltd.) at 20°C for 6 minutes to remove tin. After washing with water, the plate was dried at 100° C. for 10 minutes to adhere the palladium metal plating catalyst to the surface of the undercoat resin layer.

Next, Metsuki Resist Ink (trade name: 8B-60G).

(manufactured by Tamura Seisakusho) was applied in the form of a printed circuit pattern by a screen printing method, and dried at 160° C. for 30 minutes to form a mesh resist ink layer.

After that, stay indoors for a specified period of time (5 minutes, 2 hours, 8 hours.

After leaving for 16 hours, 40 hours), heat treatment (100℃ 15 hours)
After 2 minutes (15 minutes at 150°C), electroless steel plating was performed at 70°C for 10 hours in a plating bath with the following composition to form a printed circuit.

Copper sulfate 1211EDTA
) Reethanolamine 40 #NaOH61 37% Formalin 8-〃NaCN
20 ppm Regarding the printed circuits manufactured in this way, we investigated the effects of changing the indoor standing time and changing the heat treatment conditions before electroless plating, and the results shown in the following table were obtained. In this table, the percentage of appearance of non-deposited areas is the incidence of defective products having areas where copper was not partially plated per 100 printed circuits manufactured.

Table 1 As is clear from the table above, the effect of heat treatment was remarkable, and no local precipitation was observed in the circuit forming area, regardless of the time elapsed after the Metsukiresist ink dried. .

Further, in this example, even when electroless nickel plating was performed instead of electroless steel plating, the non-precipitated area could be eliminated by heat treatment.

Applicant Canon Co., Ltd. toni 2 and -1

Claims (1)

[Claims] 1. An insulating substrate characterized by comprising the steps of attaching a plating catalyst to the surface of an insulating substrate, performing heat treatment before the electroless plating step, and forming a conductive layer on the part to which the plating catalyst is attached by electroless plating. Electrolytic plating method.