JPWO2009142126A1 - Catalyst application liquid for solder plating - Google Patents

Abstract

When performing electroless reduction solder plating directly on a copper-based conductor circuit material, it is possible to obtain a uniform film without unevenness in film thickness, and to provide a catalyst that can form a solder plating film without bridges in fine wiring And a catalyst-providing solution for performing electroless reduction solder plating on a copper-based metal, which is a water-soluble solution. This problem has been solved by a catalyst-imparting solution containing a gold compound and a chelating agent. Also, a solder plating film on a copper-based metal obtained by electroless reduction solder plating using the catalyst-providing solution, and a gold of 3 × 10 −5 g / cm 2 or less on the copper-based metal This problem has been solved by a solder plating film formed thereon.

Description

  The present invention relates to a catalyst application liquid for solder plating, and more particularly to a catalyst application liquid having a specific composition used when performing electroless reduction solder plating on a copper-based metal.

  The solder joint of the electronic material is a pure tin film formed by performing electrolytic plating such as electrolytic tin plating, electrolytic tin-lead plating, electrolytic tin-silver plating, electrolytic tin-copper plating on the copper-based conductor circuit of the electronic material. Alternatively, a method for forming a tin alloy film has been industrialized as solder plating.

  In recent years, there has been an increasing demand for practical application of solder plating not only by electroplating but also by electroless plating in order to cope with the downsizing and high density of electronic materials. In fact, electroless displacement solder plating has been industrialized. Yes.

  However, this industrialized electroless displacement solder plating needs to dissolve a large amount of the underlying copper-based conductor circuit material in order to form a pure tin film or tin alloy film. There is a possibility that the conductor circuit is cut due to too much. Therefore, in order to cope with finer wiring, electroless reduction solder plating without dissolution of the underlying copper-based conductor circuit material is used instead of electroless replacement solder plating that involves dissolution of the underlying copper-based conductor circuit material. Is desired to be industrialized.

  As a plating bath for electroless reduction solder plating, Patent Literature 1 discloses a plating bath containing a divalent ion of tin, a divalent ion of lead, a complexing agent, and a trivalent titanium ion as a reducing agent. Since this electroless reducing solder plating bath is based on a film deposition mechanism by a reducing agent, there is no need to dissolve the underlying copper conductor circuit material to form a plating film, but the plating bath itself dissolves copper. Therefore, copper dissolution in the plating bath was confirmed during the electroless reduction solder plating, and the conductor circuit was sometimes cut.

  Accordingly, a plating bath that suppresses copper solubility in the plating bath itself and suppresses elution of copper during electroless reduction solder plating has been developed by the present inventor (International Application Number: PCT / JP 2007/70564). However, if these electroless reduction solder plating is performed directly on the copper-based conductor circuit, the start of the reduction reaction on the surface of the circuit becomes sparse, and the plating film thickness at the place where the reaction has progressed becomes thin. In some cases, it may cause unevenness, and a uniform film may not be obtained.

  Therefore, if the reaction activity of the electroless reducing solder plating bath is increased in order to make the start of the reduction reaction uniform, the liquid stability is impaired, precipitation between fine wires occurs, and liquid decomposition occurs. There was a case.

  On the other hand, as a method of activating only a copper-based conductor circuit, a method of providing a palladium catalyst in a pretreatment of electroless reduction plating is generally known (for example, Patent Documents 2 to 6). This is not a pretreatment for electroless reduction solder plating, and therefore cannot be applied to electroless reduction solder plating.

  In recent years, the miniaturization of wiring has progressed, and in order to respond to it, industrialization of electroless reduction solder plating without dissolving the underlying copper-based conductor circuit material is strongly desired, but the above-described known techniques are not sufficient. There was no industrialization.

Japanese Patent Laid-Open No. 6-101056 JP-A-4-365877 JP-A-7-011448 JP-A-8-269724 JP 2003-034876 A Japanese Patent Laid-Open No. 2003-082468

  The present invention has been made in view of the above-described background art, and the problem is that when performing electroless reduction solder plating directly on a copper-based conductor circuit material, it is possible to obtain a uniform film without film thickness unevenness. Another object of the present invention is to provide a catalyst-providing liquid that can form a solder plating film without a bridge of fine wiring.

  As a result of intensive studies to solve the above problems, the present inventor tried to increase the reaction activity of the electroless reduced solder plating bath itself in order to make the progress of the reduction reaction uniform. It has been found that the liquid stability of the substrate is impaired, and a substrate wiring defect called a bridge in which precipitation occurs on an insulator portion that is not originally desired to be plated between fine wirings occurs, or liquid decomposition occurs. Therefore, for practical use, without increasing the reaction activity of the electroless reducing solder plating bath itself, that is, while maintaining the liquid stability of the electroless reducing solder plating, It has been found that it is essential to perform electroless reduction solder plating after activating only the surface of the system conductor circuit.

  Therefore, as a method of activating only the copper-based conductor circuit, the above-described electroless displacement solder plating is performed to form a pure tin film or a tin alloy film, and electroless reduction solder plating is performed thereon using an autocatalytic mechanism. Although the method was attempted, in the case of fine wiring, there was a concern about disconnection of the conductor circuit due to dissolution of the copper-based circuit material during the electroless replacement solder plating, and thus the above-mentioned problem could not be solved.

  In addition, a method of applying a palladium catalyst, which is known as a method of activating only a copper-based conductor circuit in electroless reduction plating other than electroless reduction solder plating such as electroless reduction nickel plating and electroless reduction palladium plating Attempts have been made to find that electroless reduced solder plating is not activated by palladium catalyst nuclei.

  Therefore, the present inventor has conducted extensive studies on a catalyst imparting solution that activates only a copper-based conductor circuit in order to solve the above-described problems, and as a result, has obtained at least a water-soluble gold compound and a chelating agent. As a result, it was found that the obtained electroless reduction solder plating film had no fine wiring bridge and had a uniform film thickness, and the present invention was completed.

  That is, the present invention provides a catalyst providing liquid for performing electroless reduction solder plating on a copper-based metal, which contains a water-soluble gold compound and a chelating agent. Is.

  The present invention also provides a method for producing a solder plating film, characterized in that electroless reduction solder plating is performed on a copper-based metal using the catalyst-providing liquid, and the catalyst The present invention provides a solder plating film on a copper-based metal obtained by electroless reduction solder plating using an application liquid.

In addition, the present invention provides a solder plating film having gold of 3 × 10 ⁻⁵ g / cm ² or less on a copper-based metal and formed thereon.

  According to the present invention, a uniform electroless reduction solder plating film having no film thickness unevenness can be obtained on a copper-based metal, and the electroless reduction solder plating without a bridge even if the copper-based conductor circuit is a fine wiring. A film can be formed. Moreover, generation | occurrence | production of the void at the time of solder ball joining can be suppressed.

It is a top view of the evaluation board | substrate 1 which used this invention by the Example and the comparative example. It is sectional drawing of the evaluation board | substrate 1 which used this invention by the Example and the comparative example. It is a top view of the evaluation board | substrate 2 which used this invention by the Example and the comparative example. It is sectional drawing of the evaluation board | substrate 2 which used this invention by the Example and the comparative example. FIG. 2 is an SEM photograph (100 times) showing a judgment criterion judged as “good” in a bridge evaluation of a fine wiring, and an SEM photograph example (100 times) of Example 1. FIG. It is a SEM photograph (100 times) which shows the judgment standard judged as "bad" by bridge evaluation of fine wiring, and is a SEM photograph example (100 times) of comparative example 6. It is a SEM photograph (5000 times) which shows the judgment standard judged as "None" by void generation evaluation, and is a SEM photograph example (5000 times) of Example 4. It is a SEM photograph (5000 times) which shows the judgment standard judged with "existence" by void generation evaluation, and is a SEM photograph example (5000 times) of the comparative example 1.

  Hereinafter, the present invention will be described, but the present invention is not limited to the following specific embodiments, and can be arbitrarily modified within the scope of the technical idea.

  The present invention relates to a catalyst application liquid for performing electroless reduction solder plating on a copper-based metal. In the present invention, “copper-based metal” refers to copper alone or a copper alloy containing 60 mass% or more of copper. Preferably, it is a copper alloy containing copper alone or 80% by mass or more of copper. The copper or copper alloy to which the present invention can be applied is not particularly limited as long as it is usually used for forming a conductor circuit. That is, the metal other than copper in the copper alloy is not particularly limited as long as the above effects of the present invention can be obtained.

  In the present invention, “solder” in “electroless reduction solder plating” refers to tin alone or a tin alloy containing tin and having a melting point of 350 ° C. or lower. The metal other than tin (Sn) constituting the tin alloy is not particularly limited, but lead (Pb), bismuth (Bi), antimony (Sb), silver (Ag), copper (Cu), aluminum (Al), Examples thereof include cadmium (Cd), zinc (Zn), and indium (In). One or more metals other than tin are used to form a tin alloy together with tin. That is, the “solder” in the present invention is not limited to a tin-lead alloy, and includes lead-free solder. Further, “solder” in the present invention includes tin alone (melting point: 232 ° C.).

  The “solder” in the present invention is preferably “tin alone or a tin alloy” containing tin of preferably 60% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass. Is preferable because it is more obtained. Further, although there is no particular limitation, it is preferable that the solder does not substantially contain lead, because it has a low load on the environment and the effects of the present invention can be obtained more.

  It is essential that the catalyst-providing liquid of the present invention contains at least a water-soluble gold compound and a chelating agent. The “water-soluble gold compound” in the present invention is not particularly limited as long as it is a gold compound that is soluble in water so that the concentration in the catalyst-imparting solution is suitable. Specifically, For example, gold cyanide, gold chloride, gold sulfite, gold thiosulfate and the like can be mentioned. Preferred is a gold cyanide salt from the viewpoint of the stability of the gold compound and the availability of chemicals, and particularly preferred is a first gold cyanide salt or a second gold cyanide salt. The counter anion is not particularly limited, but an alkali metal salt is more preferable as a catalyst-adding solution, and a potassium salt is particularly preferable.

  By using a catalyst-providing liquid containing a water-soluble gold compound, a uniform electroless reduced solder plating film having no film thickness unevenness can be obtained on the copper-based metal.

  The concentration of the water-soluble gold compound is not particularly limited, but is preferably 10 ppm or more and 2000 ppm or less, and particularly preferably 20 ppm or more and 1000 ppm or less, in terms of gold relative to the entire catalyst-providing liquid. If the concentration of the water-soluble gold compound is too large, gold may precipitate in the catalyst-imparting solution, resulting in instability as a catalyst-imparting solution, and if too small, the catalytic ability is incomplete and electroless reduction Solder plating may not be precipitated.

  Although there is no particular limitation, it is preferable that the catalyst imparting solution of the present invention does not substantially contain a palladium compound. This is because the electroless reduction solder plating is not activated by the palladium catalyst core, and therefore the content is wasted. If a palladium compound is contained, the liquid stability of the catalyst application liquid is reduced, and the metal in the catalyst application liquid is reduced. Gold precipitation may occur.

  The chelating agent in the present invention is not particularly limited as long as it can dissolve the copper-based metal of the copper-based conductor circuit in the catalyst-providing liquid. By containing a chelating agent as an essential component, it is possible to promote uniform dissolution of the copper-based metal in the catalyst-providing liquid and to prevent reprecipitation of the copper-based metal. In addition, it is possible to reliably perform the process, and it is possible to prevent the fine wiring from being bridged due to metal adhesion to the insulator between the fine wirings.

  The chelating agent is preferably a chelating agent having an iminodiacetic acid structure or a methylenephosphonic acid structure. Specific examples of the chelating agent having such an iminodiacetic acid structure include, for example, ethylenediaminetetraacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetramine-6acetic acid, diethylene Examples thereof include carboxymethyl glutamic acid, propanediamine tetraacetic acid, 1,3-diamino-2-hydroxylpropane tetraacetic acid, and the like, or water-soluble salts thereof. Although there is no limitation in particular as water-soluble salt, Sodium salt, potassium salt, ammonium salt, etc. are mentioned. These are used alone or in combination of two or more.

  Examples of the chelating agent having a methylenephosphonic acid structure include aminotrimethylenephosphonic acid, hydroxyethylidenediphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, and the like, or their water-solubility. Salt. Although there is no limitation in particular as water-soluble salt, Sodium salt, potassium salt, ammonium salt, etc. are mentioned. These are used alone or in combination of two or more.

  Among these, a chelating agent having an iminodiacetic acid structure is particularly preferable in that it has a strong action of stably dissolving a copper-based metal.

  The chelating agent is preferably used in the range of 1 g / L to 100 g / L, more preferably 2 g / L to 60 g / L, and particularly preferably 3 g / L to 40 g / L with respect to the entire catalyst-providing liquid. When the concentration of the chelating agent is too high, it may be precipitated in the catalyst-providing solution, and when it is too low, the effect of suppressing the occurrence of bridging of the fine wiring may be insufficient.

  The catalyst-providing liquid of the present invention preferably further contains “a heterocyclic compound having two or more nitrogen atoms in the molecule”. The electroless reduced solder plating film formed using the catalyst-providing liquid containing the “heterocyclic compound having two or more nitrogen atoms in the molecule” is formed in the solder when the solder ball is bonded onto the film. There is no generation of voids and can be used as a good mounting terminal.

  “Heterocyclic compound having two or more nitrogen atoms in the molecule” is a compound having an aromatic ring having one or more elements other than carbon (hereinafter abbreviated as “heterocycle”). A compound in which the total number of nitrogen atoms forming a heterocycle and nitrogen atoms not forming a heterocycle is two or more in the compound molecule.

  The elements other than carbon constituting the heterocycle (hereinafter abbreviated as “heteroelement”) are not particularly limited, and examples thereof include nitrogen, oxygen, and sulfur. The hetero element is preferably nitrogen.

  The heterocyclic ring of the “heterocyclic compound having two or more nitrogen atoms in the molecule” is not particularly limited, and examples thereof include a pyrrole ring, a furan ring, a thiophene ring, an imidazole ring, an oxazole ring, a thiazole ring, a pyrazole ring, and a pyridine ring. , Pyrimidine ring, purine ring, quinoline ring, isoquinoline ring, carbazole ring, 1,2,3-triazole ring, 1,2,4-triazole ring, tetrazole ring, indole ring, benzimidazole ring, benzoxazole ring, benzthiazole Ring, benztriazole ring and the like. Among these, a heterocyclic ring having one or more nitrogen atoms in the heterocyclic ring is more preferable.

  The substituent bonded to the heterocycle is not particularly limited, but an amino group, an alkyl group, an alkylamino group, and the like are preferable. Of these, amino groups are particularly preferred.

  In the present invention, examples of the “heterocyclic compound having two or more nitrogen atoms in the molecule” include pyrazole, 3-aminopyrazole, 4-aminopyrazole, 5-aminopyrazole, imidazole, 2-aminoimidazole, 4-aminoimidazole, 5-aminoimidazole, 1,2,3-triazole, 4-amino-1,2,3-triazole, 5-amino-1,2,3-triazole, 1,2,4-triazole, 3-amino-1 , 2,4-triazole, 5-amino-1,2,4-triazole, tetrazole, 5-aminotetrazole, 2-aminobenzimidazole, heterocyclic compounds having a 5-membered ring such as benztriazole, or alkyl substituted products thereof And amino-substituted products are preferred. These are used alone or in combination.

  Among these, in order to obtain the effects of the present invention, imidazole, 2-aminoimidazole, 4-aminoimidazole, 5-aminoimidazole, 1,2,4-triazole, 3-amino-1,2,4 are particularly preferable. -Triazole, 5-aminotetrazole and the like.

  The concentration of the “heterocyclic compound having two or more nitrogen atoms in the molecule” is not particularly limited, but is preferably 10 ppm or more and 10,000 ppm or less, and particularly preferably 50 ppm or more and 5000 ppm or less with respect to the entire catalyst-providing liquid. If the concentration is too high, precipitates may be generated, and if it is too low, voids may easily occur during solder ball bonding.

  The catalyst-providing liquid of the present invention can contain a pH buffering agent or the like as appropriate, if necessary. The pH buffer is not particularly limited as long as it can alleviate fluctuations in pH without adversely affecting the properties of the catalyst-providing liquid. Regardless of whether it is an organic substance or an inorganic substance, an acid or a salt thereof may be added as appropriate. Specific examples include inorganic acids such as boric acid, phosphoric acid, and pyrophosphoric acid; organic acids such as citric acid, acetic acid, malic acid, succinic acid, and tartaric acid; or salts thereof.

  The catalyst imparting solution of the present invention preferably has a pH of 3 or more and a pH of 9 or less, particularly preferably a pH of 4 or more and a pH of 8 or less. If the pH is too low, gold may be deposited, resulting in instability as a catalyst-imparting solution, and if the pH is too high, the catalytic activity may be reduced and electroless reducing solder plating may not proceed easily.

  The treatment temperature of the catalyst application liquid of the present invention is preferably 10 ° C. or higher and 95 ° C. or lower, and particularly preferably 20 ° C. or higher and 90 ° C. or lower. Further, the treatment time of the catalyst applying liquid of the present invention is preferably from 5 seconds to 15 minutes, particularly preferably from 10 seconds to 10 minutes.

The supported amount of the catalyst core metal in the catalyst application liquid of the present invention, that is, the amount of gold applied on the copper-based metal is 0.05 to 3 mg / dm ² (0.05 × 10 ^{−5 to} 3 × 10 ^−5. g / cm ³ ) is preferable, and 0.1 to ² mg / dm ² (0.1 × 10 ⁻⁵ to 2 × 10 ⁻⁵ g / cm ³ ) is particularly preferable. Within this range, the effects of the present invention described above are easily obtained. That is, as another embodiment of the present invention, “a solder plating film having 3 mg / dm ² or less (3 × 10 ⁻⁵ g / cm ² or less) of gold on a copper-based metal and formed thereon. Is preferable because it has the above-mentioned effect.

In gold plating, in order to be able to confirm the color tone of the deposited metal visually, that is, to say “gold plating”, it is about 6 mg / dm ² (6 × 10 ⁻⁵ g / cm ³ , thickness 30 nm). The amount of precipitation described above is necessary, and normal displacement gold plating is deposited on the order of 12 mg / dm ² (12 × 10 ⁻⁵ g / cm ³ , thickness 60 nm) or more. That is, the catalyst-providing liquid of the present invention deposits a significantly smaller amount of gold on a copper-based metal compared to substitutional electroless gold plating. Therefore, “application of catalyst core metal” by the catalyst application liquid of the present invention is clearly distinguished from “electroless gold plating” in terms of the amount of adhesion. Moreover, the gold | metal | money provided with the catalyst provision liquid of this invention does not need to form the gold film.

  The catalyst-providing liquid of the present invention selectively activates a copper-based metal such as a copper-based conductor circuit formed on a printed circuit board, for example. It is used to selectively form only on a copper-based metal such as a conductor circuit. Here, the “copper-based conductor circuit” is formed by forming a circuit with a copper-based metal on a base material that is an insulator such as glass epoxy, ceramic, or polyimide. The method for forming a copper-based metal circuit is not particularly limited, and examples thereof include plating, vapor deposition, and lamination of a Cu plate.

  The pretreatment step in the case of using the catalyst application liquid of the present invention is not particularly limited, and may be performed according to a pretreatment method before applying the catalyst application liquid, which is performed by ordinary electroless plating.

  The electroless reducing solder plating solution is not particularly limited and can be used. For example, those containing at least a water-soluble tin compound, a water-soluble titanium compound and an organic complexing agent can be mentioned. Moreover, carboxylic acid (salt), such as a citric acid (salt), a pH adjuster, etc. may be included. Examples of the organic complexing agent include “organic complexing agents having an iminodiacetic acid structure” such as EDTA (Ethylenediamineacetic Acid) and NTA (Nitrotropicacetic Acid); And an organic complexing agent containing trivalent phosphorus. According to the definition of “solder” in the present invention described above, a metal compound other than tin can be contained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.

Examples 1-8
<Preparation of catalyst application liquid>
“Water-soluble gold compound” shown in Table 1 is 100 ppm by mass with respect to the whole catalyst-providing liquid in terms of metal gold, and “chelating agent” shown in Table 1 is 20 g / L with respect to the whole catalyst-providing liquid. In 4-7, the "heterocyclic compound having two or more nitrogen atoms in the molecule" shown in Table 1 was further dissolved in pure water so as to be 500 ppm by mass with respect to the entire catalyst-providing liquid. For Example 8, pyridine was dissolved in pure water at the same mass concentration. Subsequently, it adjusted so that it might become pH 5.0, and each catalyst provision liquid was prepared. For pH adjustment, a sodium hydroxide aqueous solution was used to raise the pH, and hydrochloric acid was used to lower the pH.

Comparative Examples 1-2
As Comparative Example 1, a commercially available palladium-containing electroless reduced nickel plating solution (KAT-450, manufactured by Uemura Kogyo Co., Ltd.) adjusted to a normal use state was used. Moreover, as Comparative Example 2, a commercially available palladium-containing catalyst application liquid for electroless reduction nickel plating (ICP Axela, manufactured by Okuno Pharmaceutical Co., Ltd.) adjusted to a normal use state was used.

Comparative Examples 3-6
The compound shown in the leftmost column of Table 1 is 100 ppm by mass with respect to the entire catalyst-giving liquid in terms of metal, and the chelating agent shown in Table 1 in pure water so as to be 20 g / L with respect to the entire catalyst-giving liquid. Each catalyst application liquid was prepared by dissolving and adjusting to pH 5.0. For pH adjustment, an aqueous sodium hydroxide solution was used to raise the pH, and hydrochloric acid was used to lower the pH.

[Evaluation]
Using the following electroless reducing solder plating solutions (a) and (b), the electroless reducing solders obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were used in the steps shown in Table 2. Plating was performed, and the obtained electroless reduced solder plating films were evaluated by the following methods.

<Preparation of electroless reducing solder plating solution>
Each component was dissolved in pure water to prepare the electroless reduced solder plating solutions (a) and (b) so as to have the ratio shown below with respect to the entire electroless reduced solder plating solution. In the case where water of crystallization is included, the amount is converted to “without water of crystallization”.

Electroless reduced solder plating solution (a)
Trisodium citrate 100g / L
Ethylenediaminetetraacetic acid disodium 30g / L
Nitrilotriacetic acid 38g / L
Stannous chloride 18g / L
Lead chloride 0.4g / L
Titanium trichloride 6g / L

Electroless reduced solder plating solution (b)
Tin methanesulfonate 10g / L
Nitrilotrimethylenephosphonic acid 50 g / L
Potassium citrate 30g / L
Titanium trichloride 5g / L

<Production of evaluation substrate>
Evaluation board 1
An evaluation substrate having the configuration shown in FIGS. 1 and 2 was produced. Circular copper pads with a diameter of 0.76 mm are arranged in a grid pattern on a polyimide resin substrate 40 mm long x 40 mm wide x 1.0 mm thick, and each copper pad is surrounded by a photo solder resist. The one coated with is used. Each copper pad is formed of copper having a thickness of 12 μm, the thickness of the photo solder resist is 20 μm, and the diameter of the opening of the solder ball pad is 0.62 mm.

Evaluation board 2
The evaluation board | substrate of the form shown in FIG.3 and FIG.4 was created. Copper wirings having a width of 80 μm and a thickness of 40 μm are arranged at intervals of 120 μm on a polyimide resin substrate having a length of 40 mm × width of 40 mm × thickness of 1.0 mm.

<Evaluation Method for Precipitation of Electroless Reduced Solder Plating>
Using the evaluation substrate 1 and the evaluation substrate 2 described above, using the catalyst application liquid obtained in Examples 1 to 8 and Comparative Examples 1 to 6, and the electroless reduction solder plating solution (a) or (b), Electroless reduction solder plating was performed under the processing conditions shown in Table 2 below. In addition, the processing conditions by each catalyst provision liquid were performed on the conditions from which the load of the metal gold which is a catalyst nucleus will be 0.6 mg / dm < ² > (0.6 * 10 < ^-5 > g / cm < ³ >).

The electroless reduced solder plating films obtained above were evaluated by the following methods.
<Evaluation method for deposition uniformity of electroless reduced solder plating>
The film thickness of the electroless reduced solder film formed on the copper of the solder ball pad of the evaluation board 1 was measured at 10 points using a fluorescent X-ray film thickness meter (SEA5120, manufactured by Seiko Instruments Inc.), and the average film By comparing the thickness, the maximum film thickness, and the minimum film thickness, the deposition uniformity of the electroless reduction solder plating was evaluated. Moreover, the extremely small measured value of the minimum film thickness was evaluated as “precipitation unevenness”.

<Evaluation method of bridge of fine wiring>
The copper wiring of the evaluation substrate 2 was observed with a scanning electron microscope (S-4300, manufactured by Hitachi, Ltd.) (hereinafter abbreviated as “SEM”) to evaluate the bridge of the fine wiring. When the electroless reduced solder plating is not deposited on the polyimide resin and the electroless reduced solder plating film is formed only on the copper wiring surface, it is judged as “good”, and the electroless reduced solder is deposited on the polyimide resin. The result was determined as “bad”. FIG. 5 shows an observation photograph in the case of Example 1 as a determination criterion (representative example) for “good” determination, and FIG. 6 shows an observation photograph in the case of comparative example 6 as a determination criterion (representative example) for “bad” determination. Shown in

<Void generation evaluation method>
Evaluation board 1 was used to evaluate the generation of voids during solder ball bonding. The evaluation substrate 1 in which the solder plating film was formed on the ball pad by the treatment shown in Table 2 was heated at 175 ° C. for 5 hours in the same manner as in the electroless reduction solder plating precipitation evaluation. This heating condition assumes a heat treatment applied in the substrate mounting process. Flux is applied to the ball pad of the substrate after the heat treatment, and a Sn-Ag-Cu lead-free solder ball having a diameter of 0.76 mm is mounted. This is used as a reflow furnace apparatus (RF-430-M2, Japan Pulse Technology Research Co., Ltd.). (Made by a company).

  The evaluation substrate 1 to which the solder balls are fused is cut into a size of about 15 mm × 15 mm so that the operation is easy, and is placed in a mold for cold embedding resin. (No. 105, manufactured by Marumoto Struers) and its curing agent were poured and cured. The cured sample was polished using a SiC polishing paper and a polishing machine, and the cross section was exposed so that the cross section of the joint between the solder ball and the ball pad could be seen.

  The exposed solder ball cross section is observed with a scanning electron microscope (S-4300, manufactured by Hitachi, Ltd.) for five balls. If no void is observed in the solder ball, “None”. If even one void is observed, it is judged as “Yes”. In addition, the diameters of the largest voids observed are shown in parentheses in Tables 3 and 4. As a representative example of “absence” determination, an observation photograph in the case of Example 4 is shown in FIG. 7, and as a representative example of “existence” determination, an observation photograph in the case of Comparative Example 1 is shown in FIG.

  As can be seen from the results of Tables 3 and 4, the catalyst-providing liquid containing the water-soluble gold compound and chelating agent of the present invention as essential components is sufficient to perform electroless reduction solder plating on a copper-based conductor circuit. It had a catalytic action, had no fine wiring bridge, and was able to form a uniform solder plating film.

  On the other hand, in Comparative Examples 1 to 5 which did not contain a water-soluble gold compound, the start of the reduction reaction was sparse, and thus a film thickness unevenness in which the plating film thickness was partially reduced occurred. Moreover, even if it contained a water-soluble gold compound, the comparative example 6 which does not contain a chelating agent caused solder deposition on the insulator portion, that is, a substrate wiring defect called a bridge.

  Furthermore, an electroless reduction solder plating film formed using a catalyst-providing liquid containing a heterocyclic compound having two or more nitrogen atoms in the molecule is not contained in the solder when solder ball bonding is performed on the film. It was found that no void was generated (Examples 4 to 7).

Evaluation with electroless reduced solder plating solution (a)

Evaluation with electroless reduced solder plating solution (b)

  The catalyst-providing liquid for electroless reduction solder plating of the present invention can provide an electroless reduction solder plating film having no film thickness unevenness and no bridge on a copper-based metal, and solder ball bonding Since generation of voids at the time can also be suppressed, it is widely used in all fields where solder joints of copper-based conductor circuits are used.

  This application is based on Japanese Patent Application No. 2008-133701 filed on May 21, 2008, the entire contents of which are hereby incorporated herein by reference. It is what

Claims (14)

  A catalyst imparting solution for performing electroless reduction solder plating on a copper-based metal, comprising a water-soluble gold compound and a chelating agent.   Furthermore, the catalyst provision liquid of Claim 1 containing the heterocyclic compound which has two or more nitrogen atoms in a molecule | numerator.   The catalyst-providing liquid according to claim 1, wherein the water-soluble gold compound is a gold cyanide salt.   The catalyst-providing liquid according to any one of claims 1 to 3, wherein the chelating agent is a chelating agent having an iminodiacetic acid structure.   The catalyst imparting solution according to any one of claims 1 to 3, which contains substantially no palladium compound.   The catalyst imparting solution according to claim 4, which contains substantially no palladium compound.   A method for producing a solder plating film, comprising performing electroless reduction solder plating on a copper-based metal using the catalyst-providing liquid according to any one of claims 1 to 3.   A method for producing a solder plating film, comprising using the catalyst application liquid according to claim 4 and performing electroless reduction solder plating on a copper-based metal.   A method for producing a solder plating film, comprising performing electroless reduction solder plating on a copper-based metal using the catalyst imparting solution according to claim 5.   A solder plating film on a copper-based metal obtained by electroless reduction solder plating using the catalyst-providing solution according to any one of claims 1 to 3.   A solder plating film on a copper-based metal obtained by electroless reduction solder plating using the catalyst-providing liquid according to claim 4.   A solder plating film on a copper-based metal obtained by performing electroless reduction solder plating using the catalyst-providing liquid according to claim 5.   A solder plating film on a copper-based metal obtained by electroless reduction solder plating using the catalyst-providing liquid according to claim 6. A solder plating film which has 3 × 10 ⁻⁵ g / cm ² or less of gold on a copper-based metal and is formed thereon.