Water-soluble preflux, printed wiring board, and method for manufacturing printed wiring board

Abstract

To provide water-soluble preflux capable of forming an organic coating excellent in appearance uniformity and repairability.SOLUTION: Water-soluble preflux contains (A) an imidazole compound, (B) monocarboxylic acid, (C) dicarboxylic acid and (D) water.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-soluble preflux, a printed wiring board, and a method for manufacturing a printed wiring board. [Background technology]

[0002] Printed wiring boards are often distributed with a solder resist coating formed on them. In such cases, most of the printed wiring board is covered with the solder resist coating. However, the solder resist coating is not present on the electrode terminals (lands) where electronic components are mounted. Therefore, the surfaces of the electrode terminals are easily oxidized during distribution and storage of printed wiring boards. Therefore, the surfaces of the electrode terminals of printed wiring boards are sometimes gold-plated to prevent oxidation of the surfaces of the electrode terminals. However, gold plating has the problem of being costly because it uses precious metals. Therefore, for printed wiring boards, a method of forming an organic coating on the surfaces of the electrode terminals using a water-soluble preflux has been adopted instead of gold plating (e.g., Patent Document 1).

[0003] Surface treatment processes for protecting copper foil, such as water-soluble preflux (hereinafter sometimes referred to as OSP) and plating, are the final steps in the manufacture of printed wiring boards. Surface treatments, including OSP, require uniform appearance to protect the copper foil from humidity during transportation and to prevent reoxidation of the copper foil from heat treatment during the soldering process after delivery. However, OSP is an imidazole-based organic material that is applied to copper foil as a very thin coating of approximately 0.12 μm to 0.5 μm. Furthermore, OSP is processed by immersion in an OSP solution whose temperature is controlled at, for example, 40 to 45°C. Therefore, a draining process is always required, and variations in the contact time of the remaining solution during the draining process can result in defects such as uneven appearance. Therefore, adding halogen components has been used to ensure uniformity in appearance, but this has the trade-off of making it difficult to repair with a release agent. Thus, there is a demand for materials other than halogen components that can improve uniformity in appearance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-322551 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a water-soluble preflux capable of forming an organic coating having excellent appearance uniformity and repairability, a printed wiring board, and a method for manufacturing a printed wiring board. [Means for solving the problem]

[0006] According to the present invention, there are provided the following water-soluble preflux, printed wiring board, and method for producing a printed wiring board. [1] A composition containing (A) an imidazole compound, (B) a monocarboxylic acid, (C) a dicarboxylic acid, and (D) water, Water-soluble preflux. [2] In the water-soluble preflux according to [1], The component (C) is at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, and malic acid. Water-soluble preflux. [3] In the water-soluble preflux according to [1] or [2], The blending amount of the (A) component is 0.02% by mass or more and 1% by mass or less with respect to 100% by mass of the water-soluble preflux. The blending amount of the (C) component is 0.03% by mass or more and 1% by mass or less with respect to 100% by mass of the water-soluble preflux. Water-soluble preflux. [4] In the water-soluble preflux according to any one of [1] to [3], Contains no halogen compounds Water-soluble preflux. [5] An organic coating is formed on an electrode terminal using the water-soluble preflux according to any one of [1] to [4]. Printed wiring board. [6] A process for forming an organic coating on an electrode terminal of a printed wiring board using the water-soluble preflux according to any one of [1] to [4]. A method for manufacturing a printed wiring board. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a water-soluble preflux capable of forming an organic coating having excellent appearance uniformity and repairability, a printed wiring board, and a method for manufacturing a printed wiring board. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Water-soluble preflux] First, the water-soluble flux composition according to this embodiment will be described. The water-soluble preflux according to this embodiment contains (A) an imidazole compound, (B) a monocarboxylic acid, (C) a dicarboxylic acid, and (D) water, which will be described below.

[0009] [Component (A)] The imidazole compound (A) used in this embodiment includes imidazoles and benzimidazoles, which may be used alone or in combination of two or more. Examples of imidazoles include 2-pentylimidazole, 2-undecyl-4-methylimidazole, 2,4-dimethylimidazole, 2-phenylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-benzylimidazole, 2-phenyl-4-methyl-5-benzylimidazole, 2,4-diphenylimidazole, 2,4,5-triphenylimidazole, 2-benzylimidazole, 2-benzyl-4-methylimidazole, 2-phenylethylimidazole, 2-(2-phenylethyl)imidazole, and 2-(2-phenylpentyl)imidazole. Among these, 2,4-diphenylimidazole is preferred from the viewpoint of increasing the thickness of the organic coating.

[0010] Examples of benzimidazoles include 2-propylbenzimidazole, 2-pentylbenzimidazole, 2-octylbenzimidazole, 2-nonylbenzimidazole, 2-hexyl-5-methylbenzimidazole, 2-(2-methylpropyl)benzimidazole, 2-(1-ethylpropyl)benzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-cyclohexylbenzimidazole, 2-(2-cyclohexylethyl)benzimidazole, 2-(5-cyclohexylpentyl), 2-phenylbenzimidazole, 2-phenyl-5-methylbenzimidazole, 2-benzylbenzimidazole, 2-(2-phenylethyl)benzimidazole, 2-(5- 2-(phenylpentyl)benzimidazole, 2-(3-phenylpropyl)-5-methylbenzimidazole, 2-(4-chlorobenzyl)benzimidazole, 2-(3,4-dichlorobenzyl)benzimidazole, 2-(2,4-dichlorobenzyl)benzimidazole, 2-(mercaptomethyl)benzimidazole, 2-(2-aminoethyl)benzimidazole, 2,2'-ethylenedibenzimidazole, 2-(1-naphthylmethyl)benzimidazole, 2-(2-pyridyl)benzimidazole, 2-(2-phenylvinyl)benzimidazole, 2-(phenoxymethyl)benzimidazole, and 2-(phenoxymethyl)-5-methylbenzimidazole.

[0011] The blending amount of component (A) is preferably 0.01% by mass to 5% by mass, more preferably 0.02% by mass to 3% by mass, even more preferably 0.05% by mass to 2% by mass, and particularly preferably 0.1% by mass to 1% by mass, based on 100% by mass of the water-soluble preflux. If the blending amount of component (A) is equal to or greater than the lower limit, it becomes easier to form an organic coating such as a rust-preventive film. Furthermore, if the blending amount of component (A) is equal to or less than the upper limit, the amount of insoluble matter does not increase, which is economically preferable.

[0012] [(B) Component] Examples of the (B) monocarboxylic acid used in this embodiment include formic acid, acetic acid, propionic acid, butanoic acid, glycolic acid, lactic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, and methoxyacetic acid. Among these, from the viewpoint of water-solubilizing the (A) component, formic acid or acetic acid is preferred, and acetic acid is particularly preferred. These may be used alone or in combination of two or more.

[0013] The blending amount of component (B) is preferably 1% by mass or more and 40% by mass or less, and more preferably 2% by mass or more and 30% by mass or less, relative to 100% by mass of the water-soluble preflux. If the blending amount of component (B) is within this range, component (A) can be sufficiently water-soluble.

[0014] [(C) component] The dicarboxylic acid (C) used in this embodiment is a compound having two carboxy groups per molecule. While the reason why component (C) can improve appearance uniformity without reducing repairability is not entirely clear, the present inventors speculate as follows: That is, the present inventors speculate that component (C) changes the surface tension of the resulting organic coating or provides an auxiliary effect during the formation of the organic coating. Of course, the fact that component (C) can improve appearance uniformity is surprising and was discovered for the first time by the present inventors. From the above perspective, the number of carbon atoms in component (C) is preferably 2 to 12, more preferably 4 to 8, and particularly preferably 5 to 6. Examples of component (C) include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, maleic acid, phenylsuccinic acid, tartaric acid, malic acid, and diglycolic acid. Among these, succinic acid, glutaric acid, adipic acid, and malic acid are preferred from the viewpoint of uniformity of appearance, with glutaric acid and adipic acid being particularly preferred. These may be used alone or in combination of two or more.

[0015] The blending amount of component (C) is preferably 0.01% by mass to 5% by mass, more preferably 0.03% by mass to 3% by mass, even more preferably 0.05% by mass to 2% by mass, and particularly preferably 0.1% by mass to 1% by mass, relative to 100% by mass of the water-soluble preflux. When the blending amount of component (C) is within the above range, the appearance uniformity can be further improved.

[0016] [(D) component] The water (D) used in this embodiment is the remainder of the water-soluble preflux other than the components (A), (B), and (C) and the other components described below.

[0017] [Chelating agent] The water-soluble preflux according to this embodiment preferably further contains a chelating agent. This chelating agent can suppress defects when the water-soluble preflux according to this embodiment is used on a substrate containing a mixture of dissimilar metals, such as copper lands and gold lands. That is, to maintain the bondability of a printed wiring board, a substrate containing a mixture of dissimilar metals, such as copper lands and gold lands, is sometimes used. When attempting to treat such a substrate with water-soluble preflux, a local cell reaction occurs due to the dissimilar metals, resulting in the water-soluble preflux being applied to the gold land surface, where it is not actually required. In such cases, this can cause defects such as discoloration. This chelating agent can suppress defects such as discoloration.

[0018] Examples of chelating agents include iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), 1,2-diaminocyclohexanetetraacetic acid (CyDTA), glycol ether diaminetetraacetic acid (GEDTA), N,N-bis(2-hydroxybenzyl)ethylenediaminediacetic acid (HBED), ethylenediaminedipropionic acid (EDDP), ethylenediaminediacetic acid (EDDA), diaminopropanoltetraacetic acid (DPTA-OH), hexamethylenediaminetetraacetic acid (HDTA), hydroxyethyliminodiacetic acid (HIDA), diaminopropanetetraacetic acid (Methyl-EDTA), nitrilotripropionic acid (NTP), ethylenediaminetetrakismethylenephosphonic acid (EDTPO), and nitrilotrismethylenephosphonic acid (NTPO), as well as metal salts thereof. Among these, iminodiacetic acid, ethylenediaminetetraacetic acid, or metal salts thereof are preferred from the viewpoint of suppressing defects such as discoloration, and iminodiacetic acid or sodium iron ethylenediaminetetraacetate is more preferred.

[0019] The amount of the chelating agent is preferably 0.01% by mass to 2% by mass, more preferably 0.05% by mass to 1% by mass, and particularly preferably 0.1% by mass to 0.5% by mass, relative to 100% by mass of the water-soluble preflux. If the amount of the chelating agent is within the above range, problems such as discoloration can be more reliably prevented.

[0020] [Other ingredients] The water-soluble preflux according to this embodiment may contain an organic solvent, a buffer solution, a pH adjuster, a complex film forming aid, and the like, as long as the effects of the present invention are not impaired. However, it is preferable that the water-soluble preflux according to this embodiment does not contain a halogen compound, because although the halogen compound improves the uniformity of the appearance, it reduces the repairability. The organic solvent includes methanol, ethanol, and acetone. Examples of the base in the buffer or pH adjuster include ammonia, diethylamine, triethylamine, diethanolamine, triethanolamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, isopropylethanolamine, sodium hydroxide, and potassium hydroxide. Examples of the complex film-forming aid include metal compounds such as copper formate, copper oxalate, copper acetate, copper hydroxide, copper carbonate, copper phosphate, copper sulfate, manganese formate, manganese oxalate, manganese sulfate, zinc acetate, lead acetate, nickel acetate, barium acetate, zinc hydride, ferrous oxide, and ferric oxide. When these are used, the blending amount is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less, relative to 100% by mass of the water-soluble preflux.

[0021] [Printed wiring board and its manufacturing method] Next, a printed wiring board according to this embodiment and a method for manufacturing the same will be described. The method for manufacturing a printed wiring board according to the present embodiment includes a step of forming an organic coating on electrode terminals of the printed wiring board using the water-soluble preflux according to the present embodiment. The printed wiring board according to the present embodiment is obtained by the manufacturing method. The printed wiring board may be a semiconductor substrate, etc. The printed wiring board may be a substrate on which different metals such as copper lands and gold lands are mixed. As a method for forming the organic coating, for example, a method can be employed in which the surface of the electrode terminal of the printed wiring board to be treated is subjected to a pretreatment process of degreasing, chemical polishing (soft etching), pickling, and rinsing with water, and then pretreatment with a pretreatment liquid as necessary, and then the printed wiring board is immersed in a water-soluble preflux at 10°C to 60°C for 1 second to 100 minutes (preferably at 20°C to 50°C for 5 seconds to 60 minutes, and more preferably at 20°C to 50°C for 10 seconds to 10 minutes). The pretreatment liquid may contain an amine compound. Examples of the amine compound include imidazole compounds and alkanolamines. Examples of the imidazole compound include imidazoles and benzimidazoles. Examples of the alkanolamine include triisopropanolamine. The pretreatment liquid may further contain an organic solvent and an ammonium salt. The organic solvent may be isopropanol, etc. The ammonium salt may be ammonium acetate, etc. In this way, the imidazole compound adheres to the surface of the electrode terminal, and the amount of adhesion increases as the treatment temperature increases and the treatment time increases. It is more preferable to use ultrasonic waves in this process. The organic coating may also be formed by other application methods, such as spraying, brush coating, or roller coating. In this manner, an organic coating (such as an anti-rust film) can be formed on a printed wiring board. In this case, the coating thickness of the organic coating (coating thickness according to the conversion formula) is preferably 0.2 μm or more, more preferably 0.25 μm or more, and particularly preferably 0.35 μm or more. [Example]

[0022] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are listed below. (Component (A)) Imidazole compound A: 2,4-diphenylimidazole Imidazole compound B: 2-(4-chlorobenzyl)benzimidazole Imidazole compound C: 2-(3,4-dichlorobenzyl)benzimidazole ((B) component) Monocarboxylic acid: acetic acid ((C) component) Dicarboxylic acid A: Glutaric acid Dicarboxylic acid B: succinic acid Dicarboxylic acid C: Adipic acid Dicarboxylic acid D: Malic acid ((D) component) Water: Ion-exchanged water (Other ingredients) Halogen compound A: Zinc chloride Halogen compound B: Sodium iodide pH adjuster: 25% ammonia water

[0023] [Example 1] A water-soluble preflux was obtained by dissolving 0.5% by mass of imidazole compound A and 0.3% by mass of dicarboxylic acid A in 74.2% by mass of water, 20% by mass of monocarboxylic acid, and 5% by mass of pH adjuster. The pH of the obtained water-soluble preflux was adjusted with the pH adjuster to obtain a water-soluble preflux treatment solution capable of forming a coating.

[0024] [Examples 2 to 8] A water-soluble preflux and a water-soluble preflux treatment solution were obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1. [Comparative Examples 1 to 3] A water-soluble preflux and a water-soluble preflux treatment solution were obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.

[0025] <Evaluation of water-soluble preflux> The performance of the water-soluble preflux (film thickness, appearance after application, repairability) was evaluated by the following methods. The results are shown in Table 1. (1) Coating thickness A double-sided copper-clad laminate (size: 25 mm x 50 mm, thickness: 1.6 mm, substrate type: FR-4) was degreased, soft-etched, and washed with water to clean the surface. Then, it was immersed in the obtained water-soluble preflux for 2 minutes at 40°C to form a coating, which was then washed with water and dried with hot air to prepare a test substrate. The coating thickness was measured on a surface area of ​​25cm on both sides. 2 The coating on the test substrate was extracted with 50 mL of 0.5% hydrochloric acid, and the maximum absorbance due to the active ingredient of the coating in the extract was measured, and the coating thickness (unit: μm) was calculated using a conversion formula. (2) Appearance after application A double-sided copper-clad laminate (size: 25mm x 50mm, thickness: 1.6mm, substrate type: FR-4) and a pattern-formed substrate with land opening diameters of φ0.2mm and φ1.0mm were degreased, soft-etched, and washed with water to clean their surfaces. Next, they were immersed in the obtained water-soluble preflux for 2 minutes at 40°C to form a coating, which was then washed with water and dried with hot air to prepare test substrates. The appearance of the test substrate was then observed under an optical microscope at a magnification of 40 to 200 times to check for color unevenness, and the appearance after coating was evaluated according to the following criteria. ○: No color unevenness. △: There is slight color unevenness, but this does not pose a problem in practical use. ×: Color unevenness is observed. (3) Repairability A double-sided copper-clad laminate (size: 25mm x 50mm, thickness: 1.6mm, substrate type: FR-4) and a pattern-formed substrate with land opening diameters of φ0.2mm and φ1.0mm were degreased, soft-etched, and washed with water to clean their surfaces. Next, they were immersed in the obtained water-soluble preflux for 2 minutes at 40°C to form a coating, which was then washed with water and dried with hot air to prepare test substrates. Next, the test substrate was immersed and shaken in a degreasing agent containing 3% sulfuric acid at room temperature for 2 to 3 minutes to dissolve and peel off the water-soluble preflux coating. The test substrate was then soft-etched and washed with water again in the same manner as above to clean the surface, then immersed in the obtained water-soluble preflux for 2 minutes at 40°C to form a coating, washed with water, and dried with hot air to obtain a test substrate. The appearance of the test substrate was then observed under an optical microscope at 40 to 200 magnifications to check for color unevenness, and the repairability was evaluated according to the following criteria: The coating thickness of the test substrate was compared with that of the test substrate before repair, and the coating recovery rate (unit: %) was calculated. ○: No color unevenness. △: There is slight color unevenness, but this does not pose a problem in practical use. ×: Color unevenness is observed.

[0026] [Table 1]

[0027] As is clear from the results shown in Table 1, it was confirmed that the water-soluble prefluxes of the present invention (Examples 1 to 8) were good in all evaluation results of coating thickness, appearance after application, and repairability. Therefore, it was confirmed that the present invention can form an organic coating with excellent appearance uniformity and repairability. [Industrial Applicability]

[0028] The water-soluble preflux of the present invention is useful in the production of printed wiring boards or semiconductor substrates.

Claims

1. (A) an imidazole compound, (B) a monocarboxylic acid, (C) a dicarboxylic acid, and (D) water; the component (C) is at least one selected from the group consisting of glutaric acid and adipic acid, does not contain any halogen compounds other than the component (A); Water-soluble preflux.

2. The water-soluble preflux according to claim 1, The blending amount of the component (A) is 0.02% by mass or more and 1% by mass or less with respect to 100% by mass of the water-soluble preflux. The blending amount of the (C) component is 0.03% by mass or more and 1% by mass or less with respect to 100% by mass of the water-soluble preflux. Water-soluble preflux.

3. An organic coating is formed on an electrode terminal using the water-soluble preflux according to claim 1 or 2. Printed wiring board.

4. A method for manufacturing a printed wiring board, comprising the step of forming an organic coating on an electrode terminal of the printed wiring board using the water-soluble preflux according to claim 1 or 2. A method for manufacturing a printed wiring board.

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