JP5344416B2 - Bending resistance improver for self-catalyzed electroless nickel plating solution and self-catalyzed electroless nickel plating solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroless nickel plating liquid capable of depositing a nickel plating film having excellent foldability resistance. <P>SOLUTION: A self catalyst type electroless nickel plating liquid contains alkylene diamine compound which is expressed by general formula (I). In the formula, R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are identical to or different from one another, and each is a hydrogen atom or a hydrogen group. In formula (A) (R<SP>5</SP>is a straight-chain or branched-chain alkylene group of the carbon number of 1-5, and m denotes an integer of 1-10), and n is 2 or 3. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electroless nickel plating solution and an electroless nickel plating method.

  Conventionally, in an electronic component, particularly a printed wiring board, a portion subjected to soldering, bonding or the like is often subjected to gold plating after forming an electroless nickel plating film as a surface treatment. In this case, usually, after forming an electroless nickel plating film having a thickness of about 1 to 5 μm, a gold film of about 0.03 to 0.1 μm is formed by a displacement plating method. In order to impart excellent heat resistance in gold wire bonding, a gold film having a thickness of about 0.2 to 0.7 μm may be formed by a displacement gold plating method or a reduction gold plating method.

  Substrate materials for the printed wiring board described above are roughly classified into so-called rigid substrates mainly using glass epoxy resin and flexible substrates mainly using polyimide or the like. Among these, in the flexible substrate, flexibility is required for the plating film in order to cope with the shape change. However, when the above nickel plating / gold substitution treatment is performed, the nickel plating film has poor flexibility. There is a drawback that it is inferior in bending resistance compared to copper forming the pattern portion of the substrate. For example, Patent Document 1 below describes a method in which palladium is reduced and deposited on a nickel-based underlayer to form a palladium barrier layer, and a solder joint is formed on the palladium barrier layer by displacement gold plating. However, in this method, it is desirable that the thickness of the nickel-based underlayer is 0.5 μm or less, and if it exceeds 0.5 μm, it is described that cracks are likely to occur when bent on a flexible substrate. Yes.

In addition, the rigid and thin substrates have been used due to the miniaturization of portable devices, and there has been a strong demand for nickel plating films with excellent bending resistance.
JP 2006-49589 A

  The present invention has been made in view of the current state of the prior art described above, and its main purpose is to provide a novel electroless nickel plating solution capable of forming a nickel plating film having excellent bending resistance. .

  As a result of intensive studies to achieve the above-described object, the present inventor has used an alkylenediamine compound represented by a specific general formula as an additive for an electroless nickel plating solution, whereby bending resistance of a nickel plating film can be achieved. It has been found that the properties can be greatly improved, and further, the fine pattern properties of the deposited film and the adhesion to the copper substrate can be improved. Further, when the alkylenediamine compound is used in combination with at least one compound selected from the group consisting of phosphonic acids and amino acids, in addition to improving the bending resistance, the stability of the plating bath is also greatly improved. I found out. The present invention has been completed as a result of further research based on these findings.

That is, the present invention provides the following electroless nickel plating solution and electroless nickel plating method.
1. The following general formula (I)

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or the following group:

(Wherein R ⁵ is a linear or branched alkylene group having 1 to 5 carbon atoms, m is an integer of 1 to 10), and n is 2 or 3. ] The self-catalyzed electroless nickel plating solution characterized by containing the alkylenediamine compound represented by this.
2. Item 2. The electroless nickel plating solution according to Item 1, which is an aqueous solution containing a water-soluble nickel compound, a reducing agent, and a complexing agent as essential components.
3. ^{3. The} electroless nickel plating according to item 1 or 2, wherein in the alkylenediamine compound represented by the general formula (I), at least one of the groups represented by R ¹ , R ² , R ³ and R ⁴ is a hydrogen atom. liquid.
4). In the alkylenediamine compound represented by the general formula (I), any one of the above items 1 to 3, wherein 1 to 3 of the groups represented by R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms. An electroless nickel plating solution according to any one of the above.
5. Any of the above items 1 to 4 containing 0.01 to 10 mol of at least one compound selected from the group consisting of phosphonic acids and amino acids with respect to 1 mol of the alkylenediamine compound represented by the general formula (I) An electroless nickel plating solution according to any one of the above.
6). 6. An electroless nickel plating method comprising contacting an object to be plated with the electroless nickel plating solution according to any one of items 1 to 5.

  Hereinafter, the electroless nickel plating solution of the present invention will be described in detail.

Additive Component The electroless nickel plating solution of the present invention is a self-catalyzed electroless nickel plating solution containing a reducing agent, and the additive has the following general formula (I)

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or the following group:

(Wherein R ⁵ is a linear or branched alkylene group having 1 to 5 carbon atoms, m is an integer of 1 to 10), and n is 2 or 3. The alkylenediamine compound represented by this is contained, It is characterized by the above-mentioned.

  According to the electroless nickel plating solution of the present invention, by using the above-described alkylenediamine compound as an additive, it has excellent bending resistance as compared with a nickel plating film formed from a conventional electroless nickel plating solution. A nickel plating film can be formed.

In the above general formula (I), R ⁵ is a linear or branched alkylene group having 1 to 5 carbon atoms. Specific examples thereof include straight chain such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene and the like. Examples include branched chain methylene such as chain methylene, isopropylene, and isobutylene. Moreover, m is an integer of 1-10. Specific examples of m = 1 include linear or branched hydroxyalkyl groups having about 1 to 4 carbon atoms such as hydroxymethyl, hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, and hydroxybutyl. Can be mentioned. Hereinafter, in the present specification, it may be referred to as a hydroxyalkyl group including a case where m is 2 or more.

Specific examples of the compound having an ethylenediamine skeleton in which n = 2 among the above-described alkylenediamine compounds are as follows.
(1) Compounds in which R ¹ , R ² , R ³ and R ⁴ are all hydrogen atoms:
Ethylenediamine (2) A compound in which ^{three of} R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms:
N-hydroxymethylethylenediamine N-hydroxyethylethylenediamine N-hydroxypropylethylenediamine N-hydroxyisopropylethylenediamine N-hydroxybutylethylenediamine (3) Compound in which ^{two of} R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms :
N, N′-dihydroxymethylethylenediamine N, N′-dihydroxyethylethylenediamine N, N′-dihydroxypropylethylenediamine N, N′-dihydroxyisopropylethylenediamine N, N′-dihydroxybutylethylenediamine (4) R ¹ , R ² , R ^A compound in which one of ³ and R ⁴ is a hydrogen atom:
N, N, N′-trihydroxymethylethylenediamine N, N, N′-trihydroxyethylethylenediamine N, N, N′-trihydroxypropylethylenediamine N, N, N′-trihydroxyisopropylethylenediamine N, N, N ′ -Trihydroxybutylethylenediamine (5) Compound in which all of R ¹ , R ² , R ³ and R ⁴ are hydroxyalkyl groups:
N, N, N ′, N′-tetrahydroxymethylethylenediamine N, N, N ′, N′-tetrahydroxyethylethylenediamine N, N, N ′, N′-tetrahydroxypropylethylenediamine N, N, N ′, N '-Tetrahydroxyisopropylethylenediamine N, N, N', N'-tetrapolyhydroxypropyleneethylenediamine represented by the following formula (preferably having a molecular weight of about 764 to 770)

Moreover, the specific example of the compound which has a propanediamine skeleton which is n = 3 among the above-mentioned alkylenediamine compounds is as follows.
(1) Compounds in which R ¹ , R ² , R ³ and R ⁴ are all hydrogen atoms:
Propanediamine (2) A compound in which ^{three of} R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms:
Two of the N- hydroxymethyl-propane diamine N- hydroxyethyl-propane diamine N- hydroxypropyl propanediamine N- hydroxyisopropyl propanediamine N- hydroxybutyl propanediamine ^{(3) R 1, R 2} , R 3 and ^{R 4} Compounds that are hydrogen atoms:
N, N′-dihydroxymethylpropanediamine N, N′-dihydroxyethylpropanediamine N, N′-dihydroxypropylpropanediamine N, N′-dihydroxyisopropylpropanediamine N, N′-dihydroxybutylpropanediamine (4) R ¹ , R ² , R ³ and R ⁴ , one of which is a hydrogen atom:
N, N, N′-trihydroxymethylpropanediamine N, N, N′-trihydroxyethylpropanediamine N, N, N′-trihydroxypropylpropanediamine N, N, N′-trihydroxyisopropylpropanediamine N, N, N′-trihydroxybutylpropanediamine (5) Compound in which all of R ¹ , R ² , R ³ and R ⁴ are hydroxyalkyl groups:
N, N, N ′, N′-tetrahydroxymethylpropanediamine N, N, N ′, N′-tetrahydroxyethylpropanediamine N, N, N ′, N′-tetrahydroxypropylpropanediamine N, N, N ', N'-tetrahydroxyisopropylpropanediamine N, N, N', N'-tetrapolyhydroxypropylenepropanediamine represented by the following formula (preferably having a molecular weight of about 770 to 780)

  The above-mentioned alkylene diamine compounds can be used singly or in combination of two or more.

Among the alkylenediamine compounds represented by the above general formula (I), particularly when an alkylenediamine compound in which at least one of the groups represented by R ¹ , R ² , R ³ and R ⁴ is a hydrogen atom is used. In addition, the nickel film to be formed has not only good bending resistance but also a property that can form a good plating film only on the pattern even for an object to be plated having a fine pattern, that is, Fine pattern properties are improved.

In addition, in the case where an alkylenediamine compound in which 1 to 3 hydrogen atoms are used among the groups represented by R ¹ , R ² , R ³ and R ⁴ is used, in addition to the above performance, the base is made of copper. In the case of a metal, it is possible to form a nickel film having particularly excellent adhesion.

  In the electroless nickel plating solution of the present invention, the concentration of the alkylenediamine compound represented by the general formula (I) is preferably about 0.1 to 100 g / L, and preferably about 1 to 50 g / L. More preferred.

Composition of Electroless Nickel Plating Solution The electroless nickel plating solution of the present invention is an autocatalytic plating solution and contains a water-soluble nickel compound, a reducing agent and a complexing agent as essential components.

  The water-soluble nickel compound can be used without particular limitation as long as it is soluble in the plating solution and can obtain an aqueous solution having a predetermined concentration. For example, nickel sulfate, nickel chloride, nickel sulfamate, nickel hypophosphite, or the like can be used. In particular, nickel sulfate is preferable in terms of good solubility. A water-soluble nickel compound can be used individually by 1 type or in mixture of 2 or more types. The concentration of the water-soluble nickel compound is preferably about 0.5 to 50 g / L, and more preferably about 2 to 10 g / L.

  There is no limitation in particular also about a reducing agent, The well-known reducing agent used with the electroless nickel plating liquid can be used. Examples of such a reducing agent include hypophosphorous acid, hypophosphite (sodium salt, potassium salt, ammonium salt), dimethylamine borane, hydrazine, and the like. A reducing agent can be used individually by 1 type or in mixture of 2 or more types. The concentration of the reducing agent is preferably about 0.01 to 100 g / L, and more preferably about 0.1 to 50 g / L.

  The complexing agent is not particularly limited, and a known complexing agent used in an electroless nickel plating solution can be used. Examples of such complexing agents include monocarboxylic acids such as acetic acid and formic acid, ammonium salts, potassium salts and sodium salts thereof; dicarboxylic acids such as malonic acid, succinic acid, adipic acid, maleic acid and fumaric acid, and the like. Ammonium salts, potassium salts, sodium salts, etc .; hydroxycarboxylic acids such as malic acid, lactic acid, glycolic acid, gluconic acid, citric acid, their ammonium salts, potassium salts, sodium salts, etc .; ethylenediaminediacetic acid, 1-hydroxyethylidene Examples include -1,1-diphosphonic acid, ammonium salts, potassium salts and sodium salts thereof, aminopolycarboxylic acids such as ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid, and sodium salts, potassium salts and ammonium salts thereof. Furthermore, phosphonic acids and amino acids can also be used as complexing agents. These complexing agents can be used alone or in combination of two or more.

  The compounding amount of the complexing agent is preferably about 5 to 180 g / L, and more preferably about 10 to 120 g / L.

  Of the alkylenediamine compounds represented by the general formula (I), ethylenediamine, propanediamine and the like are components that also act as a complexing agent. Accordingly, when an alkylene diamine compound that also acts as a complexing agent is included, only the alkylene diamine compound may be used without using any other complexing agent, or may be used in combination with other complexing agents. In this case, the total amount of the alkylenediamine compound and the other complexing agent may be within the above range.

  In the electroless nickel plating solution of the present invention, particularly when the complexing agent includes at least one component selected from the group consisting of phosphonic acids and amino acids, the effect of the alkylenediamine compound is obtained. The stability of the plating bath can be greatly improved without hindering. In particular, when phosphonic acids are used, the fine pattern property can be further improved.

  As the phosphones, various phosphonic acids and salts thereof can be used. Specific examples of such phosphonic acids include aminotrimethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, dimethylenetriaminepentamethylenephosphonic acid. , Diethylenetriaminepentamethylenephosphonic acid, nitrilotrimethylenephosphonic acid, phenylphosphonic acid, 2-phosphonobutane-1,2,4tricarboxylic acid, N-hydroxyalkylaminomethylphosphonic acid represented by the following formula

(Wherein n is an integer of 2 to 6), N-phosphonomethylaminocarboxylic acid represented by the following formula

(Wherein n is an integer of 2 to 6), and salts of these phosphonic acids (metal salts such as sodium salts and potassium salts, ammonium salts and the like) and the like.

  Specific examples of amino acids include glycine, alanine, iminodiacetic acid, nitrilotriacetic acid, L-glutamic acid, L-glutamic acid diacetic acid, L-aspartic acid, taurine and the like.

  About the above-mentioned phosphonic acids and amino acids, it is also possible to use 2 or more types together, respectively. In order to exert the effect of improving the stability of the plating bath, the concentration of at least one compound selected from the group consisting of phosphonic acids and amino acids is 1 mole of alkylenediamine compound represented by the general formula (I). It is preferable to set it as about 0.01-10 mol with respect to it.

  The electroless nickel plating solution of the present invention may contain various commonly used additives as necessary. For example, as a stabilizer, lead salts such as lead nitrate and lead acetate; bismuth salts such as bismuth nitrate and bismuth acetate; sulfur compounds such as thiodiglycolic acid may be added singly or in combination of two or more. it can. Although the addition amount of a stabilizer is not specifically limited, For example, it can be set as about 0.01-100 mg / L.

  Further, boric acid, phosphoric acid, phosphorous acid, carbonic acid, sodium salts, potassium salts, ammonium salts and the like thereof can be blended as pH buffering agents. Although the compounding quantity of a buffering agent is not specifically limited, For example, it can be set as about 0.1-200 g / L.

  Furthermore, in order to improve the permeability of the plating solution, a surfactant can be blended. The surfactant is not particularly limited, and various surfactants such as nonionic, cationic, anionic, and amphoteric can be added singly or in combination of two or more. The amount added may be, for example, about 0.1 to 100 mg / L.

  The pH of the electroless nickel plating solution of the present invention is usually about 2 to 9, and preferably about 3 to 8. For pH adjustment, inorganic acids such as sulfuric acid and phosphoric acid, sodium hydroxide, aqueous ammonia and the like can be used.

Electroless Plating Method In order to perform electroless nickel plating using the electroless nickel plating solution of the present invention, the electroless plating solution may be brought into contact with the object to be plated according to a conventional method. Usually, a nickel plating film can be efficiently formed by immersing an object to be plated in the electroless nickel plating solution.

  The liquid temperature of the electroless nickel plating solution is usually about 40 to 98 ° C, and preferably about 60 to 95 ° C. If necessary, the plating solution can be stirred and the object to be plated can be swung.

  There is no particular limitation on the material of the object to be plated. For example, metals such as iron, cobalt, nickel, and palladium, and alloys thereof have catalytic properties for reduction deposition of electroless nickel plating. Therefore, after pretreatment according to a conventional method, direct electroless nickel plating film Can be formed. For non-catalytic metals such as copper, glass, ceramics, and the like, electroless nickel plating may be performed after attaching metal catalyst nuclei such as palladium nuclei according to a conventional method.

  In particular, the electroless nickel plating solution of the present invention is excellent in bending resistance when used as a plating solution for surface treatment in a part to be soldered, bonded, etc., using a flexible substrate using polyimide or the like as an object to be plated. Thus, it is possible to form a nickel plating film that is less prone to cracking and excellent in reliability. In this case, the thickness of the nickel plating film is usually about 0.2 to 10 μm. Further, a gold plating film is often formed on the nickel plating film according to a conventional method. For example, a gold film having a thickness of about 0.03 to 0.1 μm can be formed by displacement plating. Further, for heat-resistant gold wire bonding, the thickness is reduced to 0 by displacement gold plating or reduction gold plating. In some cases, a gold film of about 2 to 0.7 μm may be formed. The nickel plating film formed by using the electroless nickel plating solution of the present invention can exhibit good adhesion even when these gold plating films are formed, and has good bending resistance, Good properties such as solderability and wire bonding can be exhibited.

  According to the electroless nickel plating solution of the present invention, an electroless nickel plating film excellent in bending resistance can be formed. Furthermore, by selecting the type of the alkylenediamine compound, it is possible to further improve the fine pattern property, the adhesion to the copper material, and the like.

  Further, when the alkylenediamine compound is used in combination with at least one component selected from the group consisting of phosphonic acids and amino acids, the stability of the plating bath can be greatly improved.

  Therefore, by using the electroless nickel plating solution of the present invention, for example, when a printed wiring board or the like is to be plated, it is possible to form a highly reliable nickel plating film having excellent bending resistance. Become.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
Bath No. 1 shown in Table 1 below. 1-16 (invention plating bath) and bath no. Each electroless nickel plating solution of A (comparative bath) was prepared.

  A plating test was performed by the following method using each of the above electroless nickel plating solutions.

  As an object to be plated, 40 copper patterns (copper thickness 18 μm) having a line width of 75 μm and a slit width of 75 μm were formed on a 2 × 7 cm polyimide resin (thickness 25 μm) and a 1 × 4 cm copper pad. A thing was used.

  About this to-be-plated thing, after performing a degreasing process, it etches about 0.5 micrometer with a persulfuric-acid Na solution, The catalyst liquid containing 200 ml / L of ICP Axela (Okuno Pharmaceutical Co., Ltd. product, Pd containing catalyst liquid). After applying the catalyst for 1 minute at room temperature, the object to be plated was immersed in 1 liter of the above plating bath, and the electroless nickel plating with a thickness of about 3 μm at the bath temperature and plating treatment time shown in Table 1 A film was formed.

About each obtained sample, the bending resistance (film | membrane flexibility), fine pattern property (presence of the spreading of plating), and the adhesiveness with respect to a copper raw material were evaluated by the following method. The results are shown in Table 2 below.
* Bending resistance:
A wire pattern part with a line width of 75 μm is subjected to a bending resistance test of an electroless nickel plating film by winding it around a stainless steel rod having a diameter of 0.8 mm to an angle of about 180 degrees with the plating surface being the surface. It was. About each sample after a test, the microscope observation (1000 times) was performed and the presence or absence of the crack of a plating film was investigated. As for the results, a case where no crack is observed is indicated by a mark ◯, and a case where a crack is observed is indicated by a mark X.
* Fine pattern property About the wiring pattern part with a line | wire width of 75 micrometers of each sample after plating, the presence or absence of the plating spreading out of a copper pattern was investigated by microscopic observation (1000 times). As for the results, the case where there is no plating spread is indicated by ◎, the case where slight plating spread is observed is indicated by ○, and the case where many plating spreads are indicated by Δ.
* Adhesion with copper material:
A pad portion having an area of 1 × 4 cm was cut into the surface of the nickel plating film using a cutter knife to form 100 1 mm square cells, and an adhesive tape was attached thereto, which was peeled off in the vertical direction. The adhesion of the nickel plating film was evaluated by measuring the number of squares peeled at this time. The case where the peeled square is 0 is indicated by a mark ◯, and the case where the number is 10 is indicated by a mark △.

  As is apparent from the above results, bath No. 1 containing an alkylenediamine compound as an additive was used. It was confirmed that the nickel plating film formed from 1 to 16 electroless nickel plating baths was a flexible plating film excellent in bending resistance because no crack was generated in the bending resistance test.

  Furthermore, for an electroless nickel plating bath (bath Nos. 1 to 6 and 9 to 14) containing an alkylenediamine compound in which at least one hydrogen atom is bonded to a nitrogen atom as an additive, the fine pattern property is particularly good. Among these, a nickel plating film formed from an electroless nickel plating bath (bath Nos. 2 to 6 and 10 to 14) containing an alkylenediamine compound having at least one hydroxyalkyl group as a substituent includes a copper material, The adhesion was also very good.

Example 2
Bath No. shown in Table 3 below. Each electroless nickel plating solution of 17-23 (present invention plating bath) was prepared.

 As the object to be plated, 40 copper patterns (copper thickness 18 μm) with a line width of 40 μm and a slit width of 40 μm are formed on a 2 × 7 cm polyimide resin (thickness 25 μm), and a 1 × 4 cm copper pad is formed. After the treatment up to the application of the catalyst in the same manner as in Example 1, the object to be plated was immersed in 1 liter of the plating bath described above, and the thickness was determined at the bath temperature and plating treatment time shown in Table 3. An electroless nickel plating film having a thickness of about 3 μm was formed. In addition, the to-be-plated object used in Example 2 has a narrow pitch width of a copper pattern compared with the to-be-plated object used in Example 1, and can perform more precise evaluation about fine pattern property.

  About the nickel plating film formed by the above-mentioned method, it carried out similarly to Example 1, and evaluated bending resistance, fine pattern property, and the adhesiveness with respect to a copper raw material. Further, as an evaluation of the bath stability of each electroless nickel plating solution, the plating solution was placed in a glass beaker and heated at 90 ° C. for 2 days to determine whether nickel was deposited on the bottom of the beaker. As for the results of the bath stability test, the symbol ◎ indicates that there is no Ni deposition on the beaker bottom, the symbol ○ indicates that there is a trace of Ni nuclei on the beaker bottom, and Δ indicates that nickel deposition is clearly observed on the beaker bottom. Shown with a mark. The above results are shown in Table 4 below.

  As is apparent from the above results, bath No. 1 containing an alkylenediamine compound as an additive was used. The nickel plating film formed from the electroless nickel plating bath of No. 17 was good in all the characteristics of bending resistance, fine pattern property and adhesion, but further, bath No. 1 containing phosphonic acids or amino acids. 18-23 electroless plating baths were more excellent in bath stability. In particular, bath no. With respect to the electroless nickel plating solution of 18 to 20, the occurrence of plating spread was not observed even on the object to be plated with a narrow pitch width of the copper circuit, and the fine pattern property was also very good.

Claims (4)

The following general formula (I)

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or the following group:

(Wherein R ⁵ is a linear or branched alkylene group having 1 to 5 carbon atoms, m is an integer of 1 to 10), and n is 2 or 3. ] To contain alkylenediamine compound represented by a autocatalytic electroless nickel plating solution for a bending resistance improving agent characterized,
The alkylenediamine compound represented by the general formula (I) is:
(A) Compound in which ^{two of} R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms
(B) A compound in which one of R ¹ , R ² , R ³ and R ⁴ is a hydrogen atom
A bending resistance improver for an electrocatalytic electroless nickel plating solution for a flexible substrate, which is at least one of the above . Containing autocatalytic electroless nickel plating solution for a bending resistance improving agent according to claim 1, autocatalytic electroless nickel plating solution for a flexible substrate. An autocatalytic electroless nickel plating solution containing the bending resistance improver for an autocatalytic electroless nickel plating solution according to claim 1 , further comprising an alkylenediamine compound 1 represented by the general formula (I) An autocatalytic electroless nickel plating solution for a flexible substrate containing 0.01 to 10 mol of phosphonic acid with respect to mol. The electroless nickel plating solution according to claim 2 or 3 , which is an aqueous solution containing a water-soluble nickel compound, a reducing agent and a complexing agent as essential components.