JPH0791657B2 - Palladium activator and method for electroless plating of ceramic substrate - Google Patents

Description

The present invention relates to a palladium activator for forming a metal palladium nucleus on tungsten (W) or molybdenum (Mo) and a conductor pattern of these W and Mo. The present invention relates to a method of selectively performing electroless plating on the pattern of a formed ceramic substrate.

[Conventional technology]

In order to perform electroless plating on the conductor pattern on the ceramic substrate on which the conductor pattern of W or Mo (sintered circuit of W or Mo) is formed, it is necessary to first activate the conductor pattern. As a means, a palladium activation method has heretofore been adopted in which a metal palladium nucleus is deposited on a conductor pattern, and an electroless plating film is deposited on this metal palladium nucleus.

However, when such activation with palladium is performed, usually, after immersing the ceramic substrate in a sensitizing solution containing stannous ions and then immersing it in an activating solution containing palladium ions, or by activating it with stannous ions. Although it is immersed in an activating solution containing palladium ions, stannous ions and palladium ions have strong adsorptivity, so that metal palladium nuclei are easily deposited on the entire surface of the ceramic substrate.

For this reason, after masking the portions other than the conductor pattern of the ceramic substrate with a resist film having low adsorptivity, or after depositing the electroless plating film on the entire surface of the ceramic substrate, the electroless plating film on the portion other than the conductor pattern is appropriately formed. Although a method of dissolving and removing with an etching agent is adopted, these methods have many steps and are complicated, workability is deteriorated, and cost is increased.

In order to improve this point, a palladium activating solution containing a water-soluble palladium salt and an alkali metal hydroxide is conventionally provided with at least one complexing agent selected from ethylenediamine, propylenediamine and butylenediamine. A palladium activating liquid added has been proposed (Japanese Patent Laid-Open No. 58-185794). This activation liquid has a difference in the adsorption of palladium due to the addition of the above amine, but this liquid has a problem in stability, and the optimum range of use is relatively narrow, which causes problems in process control. is there.

The present invention has been made in view of the above-mentioned phenomenon, and metal palladium nuclei can be selectively deposited on W or Mo. Therefore, a conductor pattern of W or Mo is formed on a ceramic substrate. It is possible to selectively deposit an electroless plating film only on a pattern, the process control is easy, and a palladium activator and this palladium activator that effectively exhibit their function even if the palladium concentration is lowered. An object of the present invention is to provide a method for electroless plating of a used ceramic substrate.

[Means and Actions for Solving the Problems]

As a result of various studies to achieve the above object, the present inventors have found that for palladium activators containing an alkali-soluble palladium salt and an alkali metal hydroxide, lead, thallium, bismuth, and an alkali-soluble compound of antimony are used. If 1 or 2 or more of
When a ceramic substrate on which a Mo conductor pattern is formed is processed, metal palladium nuclei are generated only on this conductor pattern, and no metal palladium nuclei are formed on the ceramic base on which the conductor pattern is not formed. The inventors of the present invention have found that the effect is exhibited even when the palladium concentration of the agent is low, and such activation is achieved in a wide range, so that process control is facilitated, and the present invention has been accomplished.

The mechanism of action by which the addition of the alkali-soluble compound of Pb, Tl, Bi, Sb selectively produces metal palladium nuclei only on the conductor pattern of W or Mo is presumed as follows. That is, when the ceramic substrate on which the conductor pattern of W or Mo is formed is treated with the solution of the activator,
The oxide of Mo is dissolved in alkali, and fresh W and Mo appear at this time, and palladium ions are adsorbed on the W and Mo. At the same time, it also absorbs Pb, Tl, Bi or Sb ions,
The ions of Pb, Tl, Bi, Sb act as a catalyst for the reduction of palladium ion to metal colloidal palladium by the electrochemical action with W and Mo, and the metal colloidal palladium (on the W and Mo ( Metal palladium nuclei) are formed. on the other hand,
Palladium ions and Pb, Tl, Bi or Sb ions are simultaneously adsorbed on the ceramic substrate other than the conductor patterns of W and Mo. In this case, the Pb, Tl, Bi, and Sb ions are electrochemical on the ceramic substrate. Since the physical action does not occur, the palladium ion does not become a metal colloid and remains as the palladium ion. Here, the core of the electroless plating deposition is palladium in the form of a metal colloid, and palladium ions and palladium oxide (PdO) cannot be the core of the electroless plating deposition. Therefore, when the ceramic substrate treated in this way is immersed in the electroless plating solution, W or
It is presumed that plating is deposited only on the Mo conductor pattern and that plating is not deposited on other ceramic base materials.

Accordingly, the present invention is a palladium activator for forming a metallic palladium nucleus on tungsten or molybdenum, which is selected from alkali soluble palladium salts, alkali metal hydroxides, lead, thallium, bismuth and antimony. And a ceramic substrate having a conductor pattern of tungsten or molybdenum containing an alkali-soluble compound of one or more kinds of metals, and immersing it in a solution of the above palladium activator, Provided is an electroless plating method for a ceramic substrate, which comprises selectively forming a metal palladium nucleus on the pattern, and then performing electroless plating to selectively deposit an electroless plating film on the pattern. To do.

Hereinafter, the present invention will be described in more detail.

The alkali-soluble palladium salt used in the activator of the present invention may be any alkali-soluble palladium salt,
Although not particularly limited, ammonium, ethylenediamine, diethylenetriamine, glycine, EDTA,
Palladium complex salts such as ammonium such as tartaric acid and citric acid, organic amines and organic carboxylic acids are preferably used.
In this case, these palladium complex salts can be formed in the solution by adding ammonia, an organic amine, an organic carboxylic acid or the like to an inorganic palladium salt such as palladium chloride when preparing the activator solution.

The concentration of the alkali-soluble palladium salt is 10 as Pd.
~ 500 mg /, particularly preferably 20-70 mg /,
In the present invention, even a low palladium concentration can be sufficiently used.

Also, as alkali metal hydroxides, NaOH, KOH, LiOH
The concentration is 10 to 500 g /, particularly 40 to 120 g /
It is preferable that

Furthermore, as an alkali-soluble compound of Pb, Tl, Bi, Sb, oxides, chlorides, hydroxides, nitrates of these metals,
One kind or two or more kinds such as acetate can be used.
Its concentration is such that the weight ratio of the metal of these metal compounds to the Pd of the palladium salt is 0.05: 1 to 1: 1, particularly 0.1: 1.
It is preferable that the concentration is about 0.5: 1. If the concentration of these metal compounds is too low, the effect of addition is not sufficiently exhibited, and if it is too high, the deposition of electroless plating may be hindered, and uneven plating or no plating may occur.

The activator is used for forming a metal palladium nucleus on the surface of W or Mo, and is typically used as a pretreatment agent for electroless plating of W or Mo conductive pattern formed on a ceramic substrate. Used to form metallic palladium nuclei on the pattern.

As a method for electrolessly plating such a ceramic substrate using the above-mentioned activator, a conventional method can be adopted. For example, the ceramic substrate is subjected to appropriate pretreatment such as degreasing, alkali etching, and pickling, and then activated. After immersing in the agent solution and forming a metallic palladium nucleus on the W or Mo conductor pattern,
The electroless plating is performed by immersing in an electroless plating solution.

In this case, the activation treatment conditions are not particularly limited, but the treatment temperature is room temperature to 90 ° C, particularly 60 to 80 ° C,
A treatment time of 1 to 10 minutes, especially 5 to 8 minutes, is preferably adopted.

The type of electroless plating is not particularly limited and may be selected as desired, but electroless copper plating, electroless nickel plating, etc. are usually employed. Known compositions and conditions can be adopted as the composition and plating conditions of these plating solutions.

Thus, in the above electroless plating step, the ceramic substrate generates metallic palladium nuclei only on the W or Mo conductor pattern in the activation step, and does not generate metallic palladium nuclei on other ceramic substrates. An electroless plating film is formed only on the conductor pattern.

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples and comparative examples]

 A palladium activating liquid having the composition shown in Table 1 was prepared.

Next, the ceramic substrate on which the sintered conductive patterns of W and Mo were formed was subjected to electroless nickel plating in the following steps. The plating state at that time is also shown in Table 1.

Plating process 1. Degreasing Detergent for dishware 20ml / 50 ℃, 10 minutes 2. Washing with water Ion-exchanged water, room temperature, 5 minutes 4. Washing with water Ion-exchanged water at room temperature, 3 minutes 5. Pickling with hydrochloric acid (36%) 500 ml / room temperature, 1 minute 6. Washing with water Ion-exchanged water at room temperature, 3 minutes 7. Activation 5 minutes 8. Washing with water Ion-exchanged water at room temperature, 5 minutes 9. Electroless nickel plating Using BEL nickel manufactured by Uemura Kogyo Co., Ltd. 65 ° C, 10 minutes 10. From the results shown in Table 1, it is recognized that the electroless nickel plating method using the activator of the present invention can surely form the plating film only on the pattern without deposition outside the pattern.

For comparison, in the plating process described above, Step 8 is repeated except that the palladium activating liquid used is that of Comparative Example 1.
The same operation was performed until then, and electroless nickel plating was performed in the subsequent steps as described below.

Plating process 1-8 Same as above 8 ′ Heavy metal aqueous solution treatment Room temperature, 5 minutes Liquid used No.1 Lead acetate 78mg / pH 13.0 Liquid used No.2 Bi (NO ₃ ) ₃ 110mg / pH 13.0 Liquid used No.3 TINO ₃ 50mg / pH 13.0 8 ″ Washing with water Ion-exchanged water, room temperature, 3 minutes 9 Same as above 10 Same as above As a result, when any of the used liquids No.1 to No.3 is used, plating is applied to part of the pattern Was not deposited, and deposition outside the pattern was also partially seen.

〔The invention's effect〕

As described above, according to the present invention, metal palladium nuclei can be selectively deposited on W or Mo, and a ceramic substrate on which a conductor pattern of W or Mo is formed is selectively formed only on this conductor pattern. It is possible to deposit an electroless plating film on the aluminum alloy, and to effectively exhibit the function even when the palladium concentration decreases, and the process control is easy.

Front page continuation (72) Inventor Taichi Nakamura 1-5-1, Exit Hirakata, Osaka Prefecture Central Research Laboratory, Uemura Industrial Co., Ltd. (56) References JP-A-58-84964 (JP, A) JP-A-60 -56073 (JP, A) JP-A-58-202595 (JP, A) JP-A-60-224292 (JP, A)

Claims (2)

[Claims] 1. A palladium activator for forming a metallic palladium nucleus on tungsten or molybdenum, which is selected from alkali-soluble palladium salts, alkali metal hydroxides, lead, thallium, bismuth and antimony. A palladium activator comprising an alkali-soluble compound of one or more metals. 2. A ceramic substrate on which a conductor pattern of tungsten or molybdenum is formed is dipped in the solution of the palladium activator according to claim 1 to selectively form metal palladium nuclei on the pattern, and then to form a metal palladium nucleus. An electroless plating method for a ceramic substrate, comprising performing electrolytic plating to selectively deposit an electroless plating film on the pattern.