JP2652803B2 - Palladium activator and electroless plating method - Google Patents

Description

The present invention relates to a palladium activator for forming a metal palladium nucleus on tungsten (W), molybdenum (Mo) or copper (Cu), and these palladium activators. The present invention relates to a method for selectively performing electroless plating on a non-conductive substrate on which a conductive pattern of Mo or Cu is formed.

[Problems to be solved by conventional technology and invention]

Conductive patterns such as ceramic substrates on which W, Mo or Cu conductor patterns are formed, or printed wiring boards in which Cu conductor (wiring) patterns are formed on synthetic resin substrates such as glass epoxy resin, paper phenol resin, and polyimide resin In order to perform electroless plating on the conductive pattern, it is necessary to first activate the conductive pattern. As such an activating means, a palladium activating method of depositing a metal palladium nucleus on the conductive pattern has been adopted. Then, the electroless plating film is deposited on the metal palladium nucleus.

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

For this reason, after masking a portion of the substrate other than the conductor pattern with a resist film having a low adsorptivity or depositing an electroless plating film on the entire surface of the substrate, the electroless plating film on the portion other than the conductor pattern is appropriately etched. However, these methods involve many steps and are complicated, resulting in poor work efficiency and high cost.

In order to improve this point, a palladium activating solution obtained by adding an inorganic acid such as HCl, HNO ₃ , H ₂ SO ₄ to a water-soluble palladium salt without performing sensitizing treatment with stannous ions. Only using the method has been proposed.

This activation method utilizes the difference in the adsorption of palladium between a metal (conductor) and a non-conductive substrate. In this method, the amount of Pd adsorbed on the non-conductive substrate is reduced. It can not be almost zero, so on the substrate
Pd protrudes and jumps easily, and has a problem in stability. Further, this method has a relatively narrow range of the optimum use condition of the activator, which may cause a problem in process control.

The present invention has been made in view of the above circumstances, W, Mo and Cu
A metal palladium nucleus can be selectively deposited on the non-conductive substrate on which the conductor pattern of W, Mo or Cu is formed, so that an electroless plating film is selectively formed only on the conductor pattern. A palladium activator that can be deposited, and the process control is easy, and effectively exhibits its function even when the palladium concentration is lowered, and a method for electroless plating a non-conductive substrate using the palladium activator. The purpose is to provide.

[Means and actions for solving the problem]

The present inventor conducted various studies to achieve the above object, and found that a water-soluble palladium salt and HCl, HF, HNO ₃ , H ₃ BF ₄ , H ₂
SO palladium activator comprising an inorganic acid such as ₄ to,
When one or more of the water-soluble compounds of lead, thallium, bismuth, and antimony are added, a non-conductive pattern in which a conductor pattern of W, Mo or Cu is formed on a ceramic plate or a synthetic resin substrate with this activator When a conductive substrate is treated, a metal palladium nucleus is generated only on this conductor pattern, and no metal palladium nucleus is generated on a non-conductive substrate body on which the conductor pattern is not formed. It has been found that the effect is exhibited even if the amount is low, and that such activation is achieved in a wide range, so that the process control becomes easy, and the present invention has been accomplished.

The mechanism by which the addition of the water-soluble compounds of Pb, Tl, Bi, and Sb selectively forms metal palladium nuclei only on the conductor patterns of W, Mo, and Cu is presumed as follows. You. That is, when the non-conductive substrate on which the conductor pattern of W, Mo or Cu is formed is treated with the solution of the activator, ions of Pb, Tl, Bi or Sb are preferentially adsorbed on W, Mo or Cu. However, these Pb, Tl, Bi, and Sb ions act as catalysts for the reduction of palladium ions to metal colloidal palladium by electrochemical action with W, Mo, or Cu. A metal colloidal palladium (metal palladium nucleus) is formed on the surface.

On the other hand, palladium ions and Pb, Tl, Bi or Sb ions are simultaneously adsorbed to a small extent on the substrate substrate other than the W, Mo and Cu conductor patterns. However, in this case, Pb, Tl, Bi, Sb
The palladium ions do not undergo an electrochemical action on the substrate surface, so that the palladium ions do not become colloidal metal and remain as palladium ions. Here, the core of electroless plating deposition is palladium in the form of metal colloid, and palladium ions and palladium oxide (Pd
O) cannot be the nucleus of electroless plating deposition. Therefore, when the non-conductive substrate treated in this way is immersed in an electroless plating solution, plating deposits only on the W, Mo or Cu conductor pattern, and plating deposition occurs on the other non-conductive substrate substrates. It is presumed that there is no such thing.

Accordingly, the present invention comprises a water-soluble palladium salt, an inorganic acid, and a water-soluble compound of one or more metals selected from lead, thallium, bismuth and antimony,
Palladium for forming a metal palladium nucleus on tungsten, molybdenum or copper, wherein the weight ratio of the metal of the metal compound to the Pd of the water-soluble palladium salt is 0.05: 1 to 1: 1. A non-conductive substrate on which an activator and a conductive pattern of tungsten, molybdenum or copper are formed is immersed in a solution of the above-described palladium activator to selectively form metal palladium nuclei on the pattern. Provided is an electroless plating method characterized by performing electroplating to selectively deposit an electroless plating film on the pattern.

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

Examples of the water-soluble palladium salt used in the activator of the present invention include palladium chloride, palladium nitrate, palladium nitrate and the like. The concentration of this water-soluble palladium salt is preferably 10 to 200 mg / Pd, particularly preferably 20 to 60 mg / Pd, and the present invention can be used satisfactorily even at a low palladium concentration.

As the inorganic acid, one or more of HCl, HF, HNO ₃ , H ₂ SO ₄ , H ₃ BF _{4 and the} like can be used, and the concentration is 5 to 200 g.
/, Particularly preferably 10 to 40 g /.

Further, as the water-soluble compounds of Pb, Tl, Bi, and Sb, one or more of these metals, such as chlorides, nitrates, and acetates, can be used. The concentration is preferably 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 to 0.5: 1. If the concentration of these metal compounds is too low, the effect of the addition is not sufficiently exhibited, and if it is too high, the deposition of electroless plating may be hindered.
No plating may occur.

The activator is used to form a metal palladium nucleus on the W, Mo or Cu surface, typically a W, Mo or Cu conductor pattern formed on a ceramic substrate or a printed wiring board Cu pattern Is used as a pretreatment agent for forming electroless palladium nuclei on these patterns.

As a method for electrolessly plating the conductive pattern on such a non-conductive substrate using the above-described activator, an ordinary method can be adopted, for example, an appropriate pretreatment such as degreasing, alkali etching, or pickling the substrate. After immersion, the substrate is immersed in the above-mentioned activator solution to form a metal palladium nucleus on the W, Mo or Cu conductor pattern, and then immersed in an electroless plating solution to perform electroless plating.

In this case, the activation treatment conditions are not particularly limited, but the treatment temperature is 10 to 60 ° C, particularly 20 to 30 ° C,
The processing time is preferably 0.5 to 3 minutes, particularly preferably 1 to 2 minutes.

The type of electroless plating is not limited at all, and is selected as desired. Usually, electroless copper plating, electroless nickel plating, or the like is used. Known compositions and conditions can be adopted for the composition and plating conditions of these plating solutions.

Thus, in the above electroless plating step, the non-conductive substrate generates metal palladium nuclei only on the W, Mo or Cu conductor patterns in the activation step, and the substrate substrate on which these patterns are not formed. Since no metallic palladium nucleus is formed on the substrate, an electroless plating film is formed only on the nuclear 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, Comparative Examples)

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

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

From the results in Table 1, it was confirmed that the electroless nickel plating method using the activator of the present invention did not cause deposition outside the pattern, and could reliably form a plating film without plating only on the pattern. Can be

〔The invention's effect〕

As described above, according to the present invention, metal palladium nuclei can be selectively deposited on W, Cu or Cu,
The electroless plating film can be selectively deposited only on this conductor pattern on the non-conductive substrate on which the W, Mo or Cu conductor pattern is formed, and the function is effectively exhibited even if the palladium concentration is reduced. The process control is also easy.

Continuation of the front page (72) Inventor Taichi Nakamura 1-5-1, Hirakata Exit, Hirakata City, Osaka Uemura Industries, Ltd. Central Research Laboratory (56) References JP-A-49-57371 (JP, A) JP-A-58- 84964 (JP, A)

Claims (2)

(57) [Claims] 1. A water-soluble palladium salt, an inorganic acid, and a water-soluble compound of one or more metals selected from the group consisting of lead, thallium, bismuth and antimony. A palladium activator for forming a metal palladium nucleus on tungsten, molybdenum or copper, wherein the ratio of the neutral palladium to Pd is 0.05: 1 to 1: 1 by weight. 2. A non-conductive substrate on which a conductive pattern of tungsten, molybdenum or copper is formed is immersed in the solution of the palladium activator according to claim 1 to selectively form metal palladium nuclei on said pattern. And electroless plating is then performed to selectively deposit an electroless plating film on the pattern.