JPS6259181B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electroless copper plating solution, that is, a chemical copper plating solution, used in the manufacture of printed circuit boards, etc., which eliminates self-decomposition of the solution, enables high-speed deposition, and improves the mechanical properties of the film. This relates to a chemical copper plating solution. A chemical copper plating solution having an autocatalytic action that can continuously deposit copper electrolessly without using electricity is already known. Such chemical copper plating solutions typically include a water-soluble copper salt, a reducing agent for copper ions, and a pH adjuster.
Known chemical copper plating solutions include an EDTA bath using ethylenediaminetetraacetate as a complexing agent for cupric acid, and a Rothsiel salt bath using Rothsiel salt as a complexing agent. Furthermore, it is known to add various additives to these baths in order to improve the mechanical properties of the plating film, such as elongation and tensile strength, and to stabilize the plating solution. Conventionally, it has been desired for these plating solutions to increase the plating speed and to improve the mechanical strength and elongation of the plating film. However, there was a conflict between the plating speed and the mechanical properties of the plating film. In other words, when additives used in conventional plating solutions are used with emphasis on improving the mechanical properties of the plating film, the plating speed slows down, and when the emphasis is placed on the plating speed, the plating speed decreases. The mechanical properties of the film deteriorate, and the stability of the glaze solution also deteriorates. One object of the present invention is to eliminate the above-mentioned drawbacks of the conventional electroless copper plating solution, and to provide an electroless copper plating solution without adversely affecting the deposition rate and the physical properties of the produced electroless copper film. The goal is to improve the stability of Another object of the present invention is to provide an electroless copper plating film with improved physical and mechanical properties such as elongation, tensile strength, and appearance such as gloss, including improved stability of the plating solution. Our objective is to provide an electroless copper plating solution that enables the production of Yet another object of the present invention is to provide a new and effective complexing agent for controlling the stability of electroless copper plating solutions. Although the present invention and the agents described herein can be used in metal plating solutions in general, they are particularly effective in electroless copper plating solutions. As mentioned above, an electroless copper plating solution usually consists of a water-soluble copper salt, a complexing agent for copper ions, a reducing agent for copper ions, and a pH adjuster or further stabilizers. There is. The functions of these components are as follows. That is, the copper salt serves as a supply source of copper ions, and the reducing agent supplies electrons that reduce the copper ions to a metallic state. The complexing agent also forms a stable complex with copper() ions and prevents the formation of cupric hydroxide (precipitate) in alkaline solutions. PH regulators adjust the optimal deposition potential of the bath. Furthermore, the stabilizer prevents self-decomposition of the plating solution, that is, autodeposition due to the formation of cuprous oxide, thereby extending the life of the solution and improving the mechanical properties of the plating film. All of these ingredients are important and essential. The present invention primarily relates to complexing agents and additives used in electroless copper plating solutions. In general, all complexing agents form sufficiently strong complexes with copper ions to prevent precipitation of copper hydroxide or its salts in alkaline solutions. Furthermore, the complexing agent must be soluble in the plating solution and must not react with the reducing agent in the solution, but only on the surface of the substrate. Furthermore, the additive prevents self-decomposition of the plating solution, that is, autodeposition due to the formation of cuprous oxide, thereby extending the life of the solution and improving the mechanical properties of the plating film. Also, the plating speed must be increased without degrading the mechanical properties of the film. As a result of various studies on plating solutions, the inventors of the present application found that in electroless copper plating solutions, the complexing agent has a very large influence on the plating speed. In other words, the copper ions and the complexing agent form a chelate, and the reducing agent precipitates copper on the surface of the substrate, but in that case, the copper ions release the chelating agent,
At the same time, copper metal is deposited by transferring and receiving electrons. It has been found that the plating speed depends on the ease with which the chelating agent is released. This is thought to be related to the steric effect and coordination properties of the chelate, and the most effective ones are those with the following structural formula that have an amine group, a carboxylic acid group, and a hydroxyl group. It became clear. (However, a to d in the formula are integers of 1 to 3, n is 2,
(3. It has been discovered that significant stabilization is possible and the mechanical properties of the plated film can be improved without slowing down the deposition rate. That is, the additive of the present invention is a polyoxyalkylene amine type nonionic surfactant in which an amine is added to a block polymer of polyethylene polypropylene and polybutylene oxide. The molecular weight is
500 or more, and holds a hydrophobic group of propylene oxide or butylene oxide and a hydrophilic group of ethylene oxide and amine. Its structural formula is (Here, m and n are integers of 1 to 100, R is an alkyl group having 1 to 3 carbon atoms, R' is -CH ₂ -, -(CH ₂ ) ₂
-, -(CH ₂ ) ₃ -), and is a nonionic water-soluble polymer resin. Such additives are sold as surfactants by Wine and Tsuto Chemical Co., Ltd. and Asahi Denka Co., Ltd. under the trade name Tetronik. A small amount of surfactant added to the plating solution is effective, and the appropriate concentration is 1 mg/ to 200 mg/. Furthermore, by using a cuprous ion complexing agent having the following structural formula in combination with the cupric complexing agent and additive of the present invention, stabilization of the plating bath, precipitation rate,
It has become clear that the mechanical properties of the coating can be further improved. In other words, the following general formula X is -N-, X is -NH-, -CH ₂ -, R, R' are -(CH ₂ ) ₂ -, -(CH ₂ ) ₃ -, -CH=CH-, -CH=
It was found that complexing agents of cuprous ions represented by aliphatic acids are effective for CH-CH ₂ -, -N=N-N=N-CH ₂ -, R''.These complexing agents is expected to have extremely large complexation constants and reaction rate constants,
It is believed that this prevents the generation of Cu ₂ O generated in the plating solution, and therefore contributes to stabilizing the deposition rate of the plating bath and improving the mechanical properties of the film. The appropriate amount of these complexing agents is 1 mg to 200 mg. Hereinafter, the present invention will be explained based on examples.
When performing electroless copper plating on a phenolic resin sample piece, the following treatments were performed: (1) Washing with water (2) Degreasing with water (3) Surface cleaning (immersed in 50 g of chromic anhydride, 500 ml of water, and 200 ml of sulfuric acid for 5 minutes) Soaking) (4) Washing with water (5) Sensitization (immersion in 50 g of tin chloride, 100 ml of hydrochloric acid, and 1 solution of water for 3 minutes), (6)
Water washing (7) Activation (palladium chloride 0.1g, 1 part water
(8) Washing with water After adjusting the electroless copper plating solution with the following composition to the specified pH and maintaining the solution temperature at 70℃,
The above treated sample was immersed in this plating solution. As a comparative example, a conventional electroless copper plating solution was used.
Plating was carried out in the same manner as in the example. Tables 1 to 4 show the composition of the plating solution used, the stability of the plating solution, the plating speed, and the mechanical properties of the film. The mechanical properties of the film were determined using a stainless steel plate (100×10×2
^t ) to a thickness of approximately 30 to 35 μm, then peel off the film and use it for measurement.

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[Table] A test piece was used in a tensile tester. As is clear from Tables 1 to 4, compared to conventional electroless copper plating, the plating speed of the present invention is 8μ
m/h or more, it is 3 to 4 times more than conventional, and the mechanical properties of the film, elongation and tensile strength, are each 6.5
% or more, and 40Kg/mm ² or more, which is significantly superior to conventional methods. Moreover, the stability of the liquid is also very good. As detailed above, the electroless copper plating solution according to the present invention increases the plating speed, significantly improves the mechanical properties of the plating film, and achieves a longer service life of the solution.

Claims (1)

[Claims] 1. Water, a water-soluble copper salt, a reducing agent, a PH adjuster, and at least one stabilizer selected from the group represented by the following general formulas (1) to (4) ( However, during the ceremony m and n are integers of 1 to 100, R is an alkyl group having 1 to 3 carbon atoms, R' is _-CH2- , -( _CH2 ) ₂ --( _CH2 ) ₃
- alkylene group), the following general formula (5),
at least one type of cupric ion complexing agent selected from the group of compounds shown in (6); (However, in the formula, a to d are integers of 1 to 3, n is 2, 3, and X is hydrogen or an alkali metal) selected from the group represented by the following general formulas (7) to (9). An electroless copper plating solution comprising at least one type of cuprous ion complexing agent. X is -N-, X' is -NH-, -CH ₂ -, R, R' are -(CH ₂ ) ₃ -, -CH=CH-, -CH=CH-CH ₂
−, −N=N−, −N=N−CH ₂ −, [Formula] R″ is an aliphatic acid. 2 Water-soluble copper salts include sulfates, nitrates, acetates, formates, carbonates, and hydroxides. at least one compound selected from the group of It is a type of compound selected from the group of metal hypophosphites, and the PH regulator is selected from the group of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide. The electroless copper plating solution according to claim 1, characterized in that the electroless copper plating solution is at least one type of compound, and is added in an amount necessary to adjust the pH of the plating solution to 11 to 13.5. .