JP4640583B2 - Pretreatment liquid for electroless plating and electroless plating method using the same - Google Patents

Description

  The present invention relates to a pretreatment liquid for electroless plating and an electroless plating method using the same.

  When electroless plating is performed on an object to be plated made of a non-conductive material such as plastic or glass, it is necessary to provide a reaction field with a catalyst active in the reaction for promptly starting the electroless plating reaction. Therefore, conventionally, when performing electroless plating, as a pretreatment before putting the object to be plated into the plating solution, after degreasing and conditioning, the precursor of the catalyst (for example, when the catalyst is metallic palladium) The object to be plated is immersed in a liquid containing a palladium salt, etc., and then subjected to a treatment such as an activation treatment to give the catalyst to the surface of the object to be plated.

  For example, using a strongly acidic palladium-tin catalyst solution as a catalyst solution, immersing an object to be plated in this solution to give a catalyst nucleus, then performing an acid or alkali treatment to express the catalytic activity, There has been proposed a method in which an object to be plated is immersed in an autocatalytic electroless plating solution to generate a plating film (plating layer) (for example, see Patent Document 1 below).

  In the present specification, the “self-catalyzed electroless plating solution” is a solution used for “chemical reduction plating” using a reducing agent in a plating reaction in electroless plating, The metal ion which becomes a raw material of the metal (metal which forms a plating layer) which has a catalytic action is shown. That is, the above metal is a catalyst (autocatalyst) for the reaction between the reducing agent and the metal ion when the raw material metal ion is reduced by the reducing agent and deposited as a metal on the surface of the object to be plated. It has an action).

  As a typical application example of electroless plating, electroless plating is performed as an interlayer connection technique for electrically connecting through holes and via holes in a manufacturing process of a printed wiring board mounted on an electronic device. As electronic devices have become smaller and lighter in recent years, through holes and via holes have become smaller in diameter, especially when electroless plating is performed on holes opened by drills or lasers. Plating did not precipitate at the fracture surface of the glass fiber), and a phenomenon in which part of the surface of the object to be plated was exposed to the outside occurred frequently. This phenomenon is a concern that the reliability of the electrical connection between the layers is reduced. One reason for this is that the palladium-tin catalyst is not adsorbed on organic resins or inorganic materials.

  As a method for preventing this phenomenon, for example, a silane coupling agent having an active functional group that has hydrophilicity and easily forms a chelate in the molecule is present on the surface of the object to be plated, and then electroless A method of performing plating has been proposed (see, for example, Patent Document 2 below). Further, a method has been proposed in which an object to be plated is brought into contact with a copolymer aqueous solution of acrylamide and a quaternary ammonium compound or a fourth phosphonium compound, and then contacted with the palladium-tin catalyst solution (for example, , See Patent Document 3 below).

  In addition, as a plating pretreatment for increasing the cleaning power of an object to be plated and improving the adhesion of a plating film, a silane coupling agent, a nonionic surfactant, ethylenediaminetetraacetic acid or a salt thereof or a derivative thereof, And a method using a pretreatment liquid for electroless plating comprising an aqueous solution containing a quaternary ammonium salt has been proposed (see Patent Document 4 below).

In the printed wiring board manufacturing process, non-ionic surfactants, fluorine-containing surfactants, metal complexes, and polyacrylamide are used as pre-plating treatments to greatly improve the plating coverage in the through holes. There has been proposed a method using a pretreatment solution for electroless plating comprising an aqueous solution having a pH of 10 or more containing a surfactant having a skeleton (see Patent Document 5 below).
U.S. Pat. No. 3,119,920 Japanese Examined Patent Publication No.59-52701 Japanese Examined Patent Publication No. 63-21752 JP-A-4-56776 Japanese Patent Laid-Open No. 4-198486

  However, in the electroless plating method using the pretreatment described in Patent Documents 2 to 5, a small diameter through hole of a recent printed wiring board, specifically 0.3 mmφ or less, and an aspect ratio (through hole length / through hole) When electroless plating is performed on through-holes having a hole diameter of 5.0 or more or via holes having a small diameter, specifically 0.2 mmφ or less and an aspect ratio (via length / via diameter) of 2.0 or more. There are problems such as insufficient deposition of plating on organic resin and inorganic material (especially, the fracture surface of the glass fiber) in the holes, and sufficient reliability has not yet been obtained.

  The present invention has been made in view of the above-mentioned problems, and has an excellent degreasing and cleaning power and an active catalyst for plating reaction on the surface of an object to be plated, particularly an organic resin or an inorganic material, easily and reliably. An object of the present invention is to provide a pretreatment liquid for electroless plating for conditioning the surface of the object to be plated. Another object of the present invention is to provide an electroless plating method using such a pretreatment liquid for electroless plating.

As a result of intensive studies, the present inventors have found that the above object can be achieved by constituting a pretreatment liquid that satisfies the conditions of the specific component composition shown below, and have reached the present invention. That is, the present invention is as follows.
(1) A pretreatment liquid for electroless plating comprising at least one nonionic surfactant, at least one cationic resin, and at least one metal ion complexing agent, ionic resin, Ri Oh polyalkylene polyamine, further pre-treatment liquid electroless plating which comprises one or more alkali metal compounds.
(2) The pretreatment liquid for electroless plating according to item (1), further comprising one or more silane coupling agents .
(3) A pretreatment liquid for electroless plating comprising at least one nonionic surfactant, at least one cationic resin, and at least one metal ion complexing agent, The pretreatment liquid for electroless plating , wherein the ionic resin is a polyalkylene polyamine and further contains one or more silane coupling agents .
(4) The step of immersing the object to be plated in the pretreatment liquid for electroless plating according to any one of items (1) to (3) , the step of applying a catalyst to the object to be plated, the catalyst applied to the object of plating The electroless plating method which has the process of activating, and the process of electroless-plating to a to-be-plated object.

  By using this pretreatment liquid, the object to be plated can be efficiently washed, and the surface of the object to be plated can easily be adsorbed by the palladium-tin catalyst. Furthermore, it has the characteristic that the adhesiveness of the plating film formed after electroless plating is favorable. The above cationic resin (polyalkylene polyamine) has a group that forms a cation in the main chain in the molecule and has a cationic nitrogen atom in the group. When this is adsorbed to the object to be plated, the adsorption of the palladium-tin catalyst to the object to be plated can be promoted, and the adhesion of the plating film after electroless plating can be improved.

  Moreover, this invention provides the electroless-plating method characterized by immersing a to-be-plated object in the said pretreatment liquid, and performing electroless plating including a catalyst provision process and a catalyst activation process then. This plating method sufficiently prevents the occurrence of problems such as a part of the surface of the object to be plated after electroless plating being exposed to the outside or the formation of a plating film with a uniform thickness. A plating film can be uniformly formed on the surface of the film.

  Hereinafter, preferred embodiments of the present invention will be described in detail. First, a preferred embodiment of the pretreatment liquid for electroless plating of the present invention will be described.

The pretreatment liquid for electroless plating according to the present embodiment includes at least one nonionic surfactant, at least one cationic resin, at least one metal ion complexing agent, and at least one type. An aqueous solution containing an alkali metal compound , and the cationic resin is a polyalkylene polyamine.

  The nonionic surfactant lowers the surface tension of the liquid and promotes liquid circulation to a small diameter through hole or small diameter via hole, and also performs degreasing cleaning of the surface of the object to be plated. Examples include fatty acid monoglycerin ester, fatty acid polyglycol ester, fatty acid sorbitan ester, fatty acid monoethanolamide, fatty acid diethanolamide, fatty acid polyethylene glycol condensate, fatty acid amide / polyethylene glycol condensate, fatty alcohol / polyethylene glycol condensate, fat An aliphatic amine / polyethylene glycol condensate, an aliphatic mercaptan / polyethylene glycol condensate, an alkylphenol / polyethylene glycol condensate, a polypropylene glycol / polyethylene glycol condensate, and the like, but are not limited thereto.

  The concentration of the nonionic surfactant is preferably 0.01 to 100 g / L. Moreover, if considering the good cleaning effect, the effect of the liquid around the small-diameter hole, the economy and the load on the environment, 0.1 to 20 g / L is more preferable. If the concentration is less than 0.01 g / L, it is not preferable because the cleaning effect and the effect of flowing around the small-diameter hole cannot be obtained, and the effect of the invention cannot be obtained. In addition, if the concentration exceeds 100 g / L, it is not preferable because the economy and the load on the environment are large.

  The cationic resin promotes the adsorption of palladium-tin to the object to be plated and improves the adhesion of the plating film after electroless plating. The cationic resin is a polyalkylene polyamine, and specific examples thereof include polyethylene imine, polypropylene imine, polyalkylene imine and the like.

  The molecular weight of the cationic resin is preferably 300 to 300,000. When the molecular weight is less than 300, adsorption to the object to be plated is difficult to occur, and accordingly, adsorption of the palladium-tin catalyst is difficult to occur. On the other hand, if the molecular weight exceeds 300,000, the viscosity of the pretreatment liquid is increased, and the effect of liquid circulation to small-diameter holes cannot be obtained, which is not preferable.

  The concentration of the cationic resin is preferably 0.05 to 50 g / L. Moreover, if economic efficiency and environmental load are taken into consideration, 0.05 to 10 g / L is more preferable. When the concentration is less than 0.05 g / L, the amount of adsorption to the object to be plated is reduced, and the adsorption of the palladium-tin catalyst is less likely to occur. On the other hand, if the concentration exceeds 50 g / L or more, the economical efficiency and the load on the environment are large, which is not preferable.

The metal ion complexing agent is a metal ion eluted from the object to be plated in the cleaning process, such as Ni ²⁺ , Fe ²⁺ , Fe ³⁺ , Co ²⁺ , Sn ²⁺ , Pb ²⁺ , Pd ²⁺ , Cr ³⁺ , Zn ²⁺ , Cd. By capturing ²⁺ , Cu ²⁺ , Ag ^{+ and the} like, the cleaning effect is improved and the stability of the liquid is improved. The complexing agent is preferably a nitrogen-containing ligand, such as ammonia, monoethanolamine, diethanolamine, triethanolamine, glycine, alanine, dimethylamine, acetamide, formamide, N, N-dimethylformamide, acetonitrile, pyridine, 2-hydroxypyridine, 2-aminopyridine, 2-methylpyridine, urea, ethylenediamine, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid tetrasodium salt, hydroxyethylethylenediaminetriacetic acid, cyclohexanediaminetetraacetic acid, etc. However, it is not limited to these.

  The concentration of the complexing agent is preferably 0.01 to 100 g / L. Moreover, if economic load and environmental load are taken into consideration, 0.01 to 20 g / L is more preferable. If the concentration is less than 0.01 g / L, the stability of the liquid deteriorates due to repeated use, which is not preferable. On the other hand, if the concentration exceeds 100 g / L or more, the economic efficiency and the load on the environment are large, which is not preferable.

A alkali metal compounds, by adding this, degreasing and cleaning effects of the object to be plated becomes larger. Examples of alkali metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, trilithium phosphate, trisodium phosphate, tripotassium phosphate, lithium silicate, sodium silicate, And potassium silicate and the like, but are not limited thereto.

  The concentration of the alkali metal compound is preferably 0.01 to 200 g / L. Moreover, if considering the cleaning effect, economy, and environmental load, 0.05 to 50 g / L is more preferable. When the concentration exceeds 200 g / L, it is not preferable from the viewpoint of safety.

In addition, the pretreatment liquid for electroless plating of the present embodiment is in addition to one or more nonionic surfactants, one or more cationic resins, and one or more metal ion complexing agents, further seen contains one or more silane coupling agents, and cationic resin, characterized in that it is a polyalkylene polyamine. In addition, the pretreatment liquid for electroless plating of the present embodiment is in addition to one or more nonionic surfactants, one or more cationic resins, and one or more metal ion complexing agents, More preferably, it contains one or more alkali metal compounds and one or more silane coupling agents. The silane coupling agent can increase the adhesion between the plating film and the object to be plated, particularly an inorganic material, after electroless plating. As the silane coupling agent, an amino silane coupling agent is preferable, and examples thereof include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N- Examples include 2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldiethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, and the like. It is not limited to.

  The concentration of the silane coupling agent is preferably 0.01 to 100 g / L. Moreover, when economic efficiency and environmental load are taken into consideration, 0.01 to 10 g / L is more preferable. When the concentration is less than 0.01 g / L, the adhesion of the plating film is small and the effect of the invention cannot be obtained, which is not preferable. If the concentration exceeds 100 g / L, coupling agent aggregation occurs and the effects of the invention cannot be obtained.

  The electroless plating method of the present embodiment includes a step of immersing the object to be plated in the pretreatment liquid for electroless plating of the present embodiment, a step of applying a catalyst to the object of plating, and a catalyst applied to the object of plating. And a step of performing electroless plating on an object to be plated.

  The temperature of the pretreatment liquid for electroless plating of the present invention when performing electroless plating is preferably 30 to 90 ° C. If the temperature is less than 30 ° C., the degreasing power and conditioning effect cannot be obtained, which is not preferable. On the other hand, when the temperature exceeds 90 ° C., a large amount of water evaporates, the change in concentration becomes large, and it is not preferable from the viewpoint of safety.

  The time for immersing the object to be plated in the pretreatment liquid for electroless plating of the present invention is preferably 30 seconds to 30 minutes. Moreover, in order to improve work efficiency, obtaining the effect of this invention, 1 minute-15 minutes are more preferable. When the immersion time is less than 30 seconds, the effect of the present invention cannot be obtained, which is not preferable. Further, if the immersion time exceeds 30 minutes, the working efficiency is remarkably deteriorated, which is not preferable.

  The object to be plated obtained after being immersed in the pretreatment liquid for electroless plating of the present invention may be further washed with water. This operation is for removing the excess amount of the pretreatment liquid for electroless plating adhering to the surface of the object to be plated, and the liquid film of the pretreatment liquid for electroless plating adhering to the surface of the object to be plated Is not completely removed. By optimizing the cleaning conditions, it is possible to remove an excessive amount while leaving a liquid film of an aqueous solution adhering to the surface of the object to be plated in an optimal amount. The water used for washing is more preferably ion exchange water.

  After immersing the object to be plated in the pretreatment liquid for electroless plating of the present invention, a catalyst application step and a catalyst activation step are performed. A known acidic palladium-tin catalyst solution can be used in the catalyst application step, and an acidic or alkaline activation solution can be used in the catalyst activation step.

  In this invention, it is preferable to immerse the to-be-plated object obtained after a catalyst provision process and a catalyst activation process in an autocatalytic electroless plating solution. As the autocatalytic electroless plating solution to be used, a known autocatalytic electroless plating solution can be used. For example, electroless copper plating solution, electroless nickel-phosphorous plating solution, electroless nickel-boron plating solution, electroless palladium plating solution, electroless silver plating solution, electroless gold plating solution and the like.

  Examples of the object to be plated by the electroless plating method of the present invention include, but are not limited to, plastic materials such as PET resin, epoxy resin, and polyimide resin, and composite materials such as glass, ceramics, and printed circuit boards. The pretreatment liquid for electroless plating and the electroless plating method of the present invention are suitable for printed boards having through holes.

Hereinafter, preferred examples of the present invention will be described in more detail, but the present invention is not limited to these examples.
( Reference Example 1)
As shown in Table 1 below, in ion exchange water, 5.0 g / L of polyoxyethylene octyl phenyl ether (Nonion HS-210, manufactured by NOF Corporation) as a nonionic surfactant, as a complexing agent for metal ions Triethanolamine (manufactured by Kanto Chemical Co., Inc.) 3.0 g / L, polyethyleneimine as a cationic resin (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 10,000) 0.05 g / L, 0.5 g / L and 5 Dissolved at a concentration of 0.0 g / L. This aqueous solution was referred to as “ reference pretreatment liquid ” (pretreatment liquid for electroless plating: Reference- A to Reference- C).

  Form a through-hole with a hole diameter of 0.2 mm using a drill on MCL-E-679 (trade name, thickness 1.6 mm, manufactured by Hitachi Chemical Co., Ltd.), which is an epoxy-based copper-clad laminate, as an object to be plated And what was desmeared was used. And the electroless copper plating was performed at the following process.

First, the liquid temperature of the “ reference pretreatment liquid” was adjusted to 60 ° C., and the object to be plated was immersed in this liquid for 5 minutes to wash and condition the object to be plated. Next, it was washed with water at room temperature (25 ° C.) for 2 minutes. Next, the obtained object to be plated was immersed in “HET-100” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a soft etching solution, at room temperature (25 ° C.) for 2 minutes. Next, the obtained object to be plated was washed with water at room temperature for 2 minutes. Next, it was immersed for 2 minutes at room temperature (25 ° C.) in “PD-301” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a pretreatment liquid for a palladium-tin catalyst. Next, the obtained object to be plated was immersed in “HS-202B” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a palladium-tin catalyst solution, at room temperature (25 ° C.) for 5 minutes. Next, the obtained object to be plated was washed with water at room temperature (25 ° C.) for 2 minutes.

  Next, the obtained object to be plated was immersed in “ADP-601” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is an acidic treatment solution, at room temperature (25 ° C.) for 5 minutes. In this way, a palladium catalyst for electroless plating was deposited in the through hole of the object to be plated. Next, the obtained object to be plated was washed with water at room temperature (25 ° C.) for 2 minutes.

  Next, the obtained object to be plated was immersed in “CUST-201” (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is an autocatalytic electroless copper plating solution at a liquid temperature of 25 ° C. for 15 minutes (plating). Process). Next, the obtained object to be plated was washed with water at room temperature (25 ° C.) for 5 minutes. Next, the obtained object to be plated was dried at 80 ° C. for 10 minutes. In this way, an electroless copper plating film was formed in the through hole of the object to be plated.

Next, in order to evaluate the throwing power of the object to be plated to the through hole, the object to be plated after electroless copper plating is cut as shown in FIG. 1, and light is applied from below the inner wall surface of the plating. A backlight test was conducted to examine the presence or absence of light transmission. When there is an undeposited portion of electroless copper plating, light is transmitted, and an image as shown in FIG. 2A is observed, and when there is no undeposited portion of electroless copper plating, FIG. As shown in (b), no light transmission is observed. In Reference Example 1 , as a result of the backlight test, no light transmission was observed as shown in FIG.

(Example 1 )
As shown in Table 1 below, in ion-exchanged water, polyoxyethylene octylphenyl ether 5.0 g / L as a nonionic surfactant, triethanolamine 3.0 g / L as a metal ion complexing agent, cation Polyethyleneimine 0.5 g / L as a soluble resin, and sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) 1.0 g / L, 10 g / L and 50 g / L as an alkali metal compound were dissolved. This aqueous solution was designated as “pretreatment liquid 1 ” (pretreatment liquid for electroless plating: 1- A to 1- C).

As the object to be plated, a copper-clad laminate having through holes formed as in Reference Example 1 was used. Then, electroless copper plating was performed in the same process as Reference Example 1 except that the “ reference pretreatment liquid” was changed to “pretreatment liquid 1 ”. Next, a backlight test was performed in the same manner as in Reference Example 1 in order to evaluate the throwing power of the object to be plated on the through hole. As a result of the backlight test, no light transmission was observed as shown in FIG.

(Example 2 )
As shown in Table 1 below, in ion-exchanged water, polyoxyethylene octylphenyl ether 5.0 g / L as a nonionic surfactant, triethanolamine 3.0 g / L as a metal ion complexing agent, cation Polyethyleneimine 0.5 g / L as a conductive resin, sodium hydroxide 10 g / L as an alkali metal compound, “KBE-903” (3-aminopropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., trade name as a silane coupling agent ) Dissolved at concentrations of 0.05 g / L, 0.5 g / L and 5.0 g / L. This aqueous solution was designated as “pretreatment liquid 2 ” (pretreatment liquid for electroless plating: 2- A to 2- C).

As the object to be plated, a copper-clad laminate having through holes formed as in Reference Example 1 was used. Then, electroless copper plating was performed in the same process as Reference Example 1 except that the “ reference pretreatment liquid” was changed to “pretreatment liquid 2 ”. Next, a backlight test was performed in the same manner as in Reference Example 1 in order to evaluate the throwing power of the object to be plated on the through hole. As a result of the backlight test, no light transmission was observed as shown in FIG.

(Comparative Example 1)
As shown in Table 2 below, the concentration of polyethyleneimine (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 10,000), which is a cationic resin of the “ reference pretreatment liquid” , is 0 g / L (pretreatment for electroless plating). Solution: Performed in the same manner as in Reference Example 1 except that the solution was changed to 1-D). As a result of the backlight test, light transmission was observed as shown in FIG.

(Comparative Example 2)
As shown in Table 2 below, the concentration of polyethyleneimine (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 10,000), which is a cationic resin of “pretreatment liquid 1 ”, is 0 g / L (pretreatment for electroless plating). liquid: except that the 2-D~2-F), was carried out in the same manner as in reference example 1. As a result of the backlight test, light transmission was observed as shown in FIG.

(Comparative Example 3)
As shown in the following Table 2, the concentration of polyethyleneimine (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 10,000), which is a cationic resin of “pretreatment liquid 2 ”, is 0 g / L (pretreatment for electroless plating). liquid: except that the 3-D~3-F), was carried out in the same manner as in reference example 1. As a result of the backlight test, light transmission was observed as shown in FIG.

(Comparative Example 4)
As shown in Table 2 below, the concentration of triethanolamine (manufactured by Kanto Chemical Co., Ltd.), which is a metal ion complexing agent in the “ reference pretreatment liquid” ( reference- B), is 0 g / L (before electroless plating). Treatment liquid: It was carried out in the same manner as in Reference Example 1 except that it was changed to 1-E). As a result of the backlight test, light transmission was observed as shown in FIG.

(Comparative Example 5)
As shown in Table 2 below, the concentration of polyoxyethylene octylphenyl ether (Nonion HS-210, manufactured by NOF Corporation), which is a nonionic surfactant of “ Reference Pretreatment Solution” ( Reference- B), is 0 g / The same procedure as in Reference Example 1 was conducted except that L (pretreatment liquid for electroless plating: 1-F) was used. As a result of the backlight test, light transmission was observed as shown in FIG.

As is clear from the results of the backlight test, the pretreatment liquids 1 and 2 (1-A to 1-C, 2-A to 2- C) for electroless plating of the present invention have a cationic resin concentration. Pretreatment solution for electroless plating that is 0 g / L: Compared with (1-D, 2-D to 2-F, 3-D to 3-F), plating around the through-hole of the object to be plated It was confirmed that it was excellent in performance. Further, as shown in Comparative Example 4 and Comparative Example 5, it was confirmed that a nonionic surfactant and a complexing agent are necessary to obtain the effects of the present invention. As described above, according to the present invention, before electroless plating, which has an excellent degreasing and cleaning power and can easily and reliably adhere a catalyst active in a plating reaction to the surface of an object to be plated. A treatment liquid can be provided. Moreover, according to the present invention, by using such a pretreatment liquid for electroless plating, it is possible to provide an electroless plating method capable of performing plating with good adhesion between an object to be plated and a plating film. it can.

(A) is a top view which shows the cut location of a to-be-plated thing, (b) is a schematic surface showing the backlight test of the to-be-plated thing. (A) And (b) is an optical microscope photograph which shows the presence or absence of light transmission of the through hole in a backlight test.

Explanation of symbols

1: Through hole 2: Cut surface A
3: Cut surface B
4: Object to be plated (epoxy copper-clad laminate)
5: Optical microscope 6: Light (backlight)

Claims (4)

A pretreatment liquid for electroless plating comprising one or more nonionic surfactants, one or more cationic resins, and one or more metal ion complexing agents, wherein the cationic resins but Ri Oh polyalkylene polyamine, further pre-treatment liquid electroless plating which comprises one or more alkali metal compounds. The pretreatment liquid for electroless plating according to claim 1, further comprising one or more silane coupling agents . A pretreatment liquid for electroless plating comprising one or more nonionic surfactants, one or more cationic resins, and one or more metal ion complexing agents, wherein the cationic resins Is a polyalkylene polyamine, and further contains one or more silane coupling agents . A step of immersing the object to be plated in the pretreatment liquid for electroless plating according to any one of claims 1 to 3 , a step of imparting a catalyst to the object to be plated, a step of activating the catalyst imparted to the object of plating, An electroless plating method including a step of performing electroless plating on an object to be plated.

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