Water-soluble preflux, printed circuit board and method for manufacturing printed circuit 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 Art

[0002] Printed wiring boards often circulate with a solder resist film formed. In such cases, most of the printed wiring board is covered with the solder resist film. However, for the electrode terminals (lands) for mounting electronic components, there is no solder resist film. Therefore, when the printed wiring board is circulated or stored, the surface of the electrode terminals is easily oxidized. Therefore, the surface of the electrode terminals of the printed wiring board may be subjected to a gold plating process to prevent oxidation of the surface of the electrode terminals. However, there is a problem that the cost is high because a noble metal is used for the gold plating process. Therefore, in printed wiring boards, instead of the gold plating process, a method of forming an organic film on the surface of the electrode terminals with a water-soluble preflux is adopted (for example, Patent Document 1).

[0003] Surface treatment steps for the purpose of protecting copper foil, such as water-soluble preflux (hereinafter sometimes referred to as OSP) and plating treatment, are in the final process of manufacturing a printed wiring board. In particular, for surface treatment including OSP, uniform appearance is required to protect from humidity during transportation of copper foil or to prevent reoxidation of copper foil from the heat treatment received in the mounting soldering process after delivery. However, OSP forms a very thin coating film of about 0.12 μm to 0.5 μm of an imidazole-based organic material on the copper foil. Also, OSP is treated by an immersion method in an OSP chemical solution whose temperature is adjusted to 40°C to 45°C, for example. Therefore, there is always a liquid draining step, and uneven appearance defects may occur due to variations in the contact time of the chemical solution remaining in the liquid draining step. Therefore, although the appearance uniformity was secondarily ensured by adding a halogen component, there was a problem that the repairability with respect to the release agent deteriorated due to the conflict. Thus, a material that can improve the appearance uniformity in addition to the halogen component is required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a water-soluble preflux, a printed wiring board, and a method for manufacturing a printed wiring board that can form an organic film excellent in appearance uniformity and repairability.

Means for Solving the Problems

[0006] According to the present invention, a water-soluble preflux, a printed wiring board, and a method for manufacturing a printed wiring board shown below are provided. [1] A water-soluble preflux containing (A) an imidazole compound, (B) a monocarboxylic acid, (C) a dicarboxylic acid, and (D) water. Water-soluble preflux. [2] The water-soluble preflux according to [1], wherein 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] The water-soluble preflux according to [1] or [2], wherein 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 component (C) 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] The water-soluble preflux according to any one of [1] to [3], which does not contain a halogen compound, Water-soluble preflux. [5] An organic film is formed on the electrode terminal by the water-soluble preflux according to any one of [1] to [4], Printed wiring board. [6] A method for manufacturing a printed wiring board, comprising a step of forming an organic film on an electrode terminal of the printed wiring board using the water-soluble preflux according to any one of [1] to [4]. 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, a printed wiring board, and a method for manufacturing a printed wiring board that can form an organic film excellent in appearance uniformity and repairability.

Modes for Carrying Out the Invention

[0008] [Water-soluble preflux] First, the water-soluble flux composition according to the present embodiment will be described. The water-soluble preflux according to the present 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)] Examples of the (A) imidazole compound used in the present embodiment include imidazoles and benzimidazoles. These 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 making the film thickness of the organic film thicker.

[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-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, among others.

[0011] The blending amount of component (A) is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.02% by mass or more and 3% by mass or less, still more preferably 0.05% by mass or more and 2% by mass or less, and particularly preferably 0.1% by mass or more and 1% by mass or less, based on 100% by mass of the water-soluble preflux. If the blending amount of component (A) is at least the above lower limit, an organic film such as a rust preventive film can be more easily formed. Also, if the blending amount of component (A) is at most the above upper limit, the amount of insoluble matter will not increase, which is also economically preferable.

[0012] [Component (B)] 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 solubilizing the (A) component, it is preferable to use formic acid or acetic acid, and it is particularly preferable to use acetic acid. Also, these may be used alone or in combination of two or more.

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

[0014] [(C) component] The (C) dicarboxylic acid used in this embodiment is a compound having two carboxy groups in one molecule. Although the reason why the (C) component can improve the appearance uniformity without reducing the reparability is not necessarily clear, the present inventors speculate as follows. That is, the present inventors speculate that it is because the surface tension of the obtained organic film is changed by the (C) component or there is an auxiliary effect during the film formation of the organic film. Of course, it is surprising that the (C) component can improve the appearance uniformity, and it is a finding first discovered by the present inventors. From the above viewpoint, the number of carbon atoms of the (C) component is preferably 2 or more and 12 or less, more preferably 4 or more and 8 or less, and particularly preferably 5 or more and 6 or less. Examples of the (C) component 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, from the viewpoint of appearance uniformity, succinic acid, glutaric acid, adipic acid, or malic acid is preferable, and glutaric acid or adipic acid is particularly preferable. Also, 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 or more and 5% by mass or less, more preferably 0.03% by mass or more and 3% by mass or less, still more preferably 0.05% by mass or more and 2% by mass or less, and particularly preferably 0.1% by mass or more and 1% by mass or less, based on 100% by mass of the water-soluble preflux. If the blending amount of component (C) is within the above range, the appearance uniformity can be further improved.

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

[0017] [Chelating agent] The water-soluble preflux according to this embodiment preferably further contains a chelating agent. According to this chelating agent, problems when using the water-soluble preflux according to this embodiment on a substrate on which different metals such as copper lands and gold lands are mixed can be suppressed. That is, in order to maintain the bondability of the printed wiring board, a substrate on which different metals such as copper lands and gold lands are mixed may be used for the bonding surface. When attempting to perform a water-soluble preflux treatment on such a substrate, a local battery reaction due to different metals occurs, and the water-soluble preflux is also treated on the gold land surface that is not originally necessary. In such a case, it may cause problems such as discoloration. According to this chelating agent, problems such as discoloration can be suppressed.

[0018] Examples of the chelating agent include iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), 1,2-diaminocyclohexanetetraacetic acid (CyDTA), glycol ether diamine tetraacetic acid (GEDTA), N,N-bis(2-hydroxybenzyl)ethylenediamine diacetic acid (HBED), ethylenediamine dipropionic acid (EDDP), ethylenediamine diacetic acid (EDDA), diaminopropanol tetraacetic acid (DPTA-OH), hexamethylenediamine tetraacetic acid (HDTA), hydroxyethyliminodiacetic acid (HIDA), diaminopropane tetraacetic acid (Methyl-EDTA), nitrilotripropionic acid (NTP), ethylenediamine tetrakis(methylenephosphonic acid) (EDTPO), and nitrilotris(methylenephosphonic acid) (NTPO), and metal salts thereof. Among these, from the viewpoint of suppressing problems such as discoloration, iminodiacetic acid, ethylenediaminetetraacetic acid, or metal salts thereof are preferred, and iminodiacetic acid or sodium iron ethylenediaminetetraacetate is more preferred.

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

[0020] [Other components] The water-soluble preflux according to the present embodiment may contain an organic solvent, a buffer solution, a pH adjuster, a complex film formation aid, etc., as long as the effects of the present invention are not inhibited. However, the water-soluble preflux according to the present embodiment preferably does not contain a halogen compound. This is because although the halogen compound improves the appearance uniformity, the reparability deteriorates. Examples of the organic solvent include methanol, ethanol, and acetone. Examples of bases 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 auxiliary agents 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 using these, the blending amount is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, based on 100% by mass of the water-soluble preflux.

[0021] [Printed Wiring Board and Method for Manufacturing the Same] Next, the printed wiring board and the method for manufacturing the same according to the present embodiment will be described. The method for manufacturing a printed wiring board according to the present embodiment is a method including a step of forming an organic film on an electrode terminal of a printed wiring board using the water-soluble preflux according to the present embodiment. Further, the printed wiring board according to the present embodiment is obtained by the above manufacturing method. The printed wiring board may be, in addition to a printed wiring board, a substrate for a semiconductor or the like. This printed wiring board may be a substrate on which different metals such as a copper land and a gold land are mixed-mounted. As a method for forming the organic film, for example, after performing a pretreatment step of degreasing, chemical polishing (soft etching), pickling, and water washing on the surface of the electrode terminal of the printed wiring board to be processed, and then performing pretreatment with a pretreatment liquid as necessary, the printed wiring board is immersed in the 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, more preferably at 20°C to 50°C for 10 seconds to 10 minutes). This method can be adopted. The pretreatment liquid may contain an amine compound. Examples of the amine compound include an imidazole compound and an alkanolamine. 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. Examples of the organic solvent include isopropanol. Examples of the ammonium salt include ammonium acetate. In this way, the imidazole compound adheres to the surface of the electrode terminal, and the amount of adhesion increases as the treatment temperature is increased and the treatment time is lengthened. At this time, it is more preferable to use ultrasonic waves. Note that an organic film may be formed by other coating means, such as a spraying method, a brush coating method, or a roller coating method. As described above, an organic film (such as a rust preventive film) can be formed on the printed wiring board. The film thickness of the organic film (film thickness according to the conversion formula) at this time is preferably 0.2 μm or more, more preferably 0.25 μm or more, and particularly preferably 0.35 μm or more.

Examples

[0022] Next, the present invention will 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 shown below. (Component (A)) Imidazole compound A: 2,4-diphenylimidazole Imidazole compound B: 2-(4-chlorobenzyl)benzimidazole Imidazole compound C: 2-(3,4-dichlorobenzyl)benzimidazole (Component (B)) Monocarboxylic acid: acetic acid (Component (C)) Dicarboxylic acid A: glutaric acid Dicarboxylic acid B: succinic acid Dicarboxylic acid C: adipic acid Dicarboxylic acid D: Malic acid (Component (D)) Water: Ion-exchanged water (Other components) Halogen compound A: Zinc chloride Halogen compound B: Sodium iodide pH adjuster: 25% by mass aqueous ammonia

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

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

[0025] [Evaluation of water-soluble preflux] The performance (film thickness, appearance after coating, reparability) of the water-soluble preflux was evaluated by the following method. The results obtained are shown in Table 1. (1) Film thickness A double-sided copper-clad laminate (size: 25 mm × 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 at 40 °C for 2 minutes to form a film, washed with water, and dried with warm air to obtain a test substrate. For the film thickness measurement, the film on the test substrate with a surface area of 25 cm 2 on both sides was extracted with 50 mL of 0.5% hydrochloric acid, and then the maximum absorbance due to the film active ingredient in the extract was measured, and the film thickness (unit: μm) was calculated from the conversion formula. (2) Appearance after coating A double-sided copper-clad laminate (size: 25 mm × 50 mm, thickness: 1.6 mm, substrate type: FR-4) and a pattern-forming substrate having land opening diameters of φ0.2 mm and φ1.0 mm were degreased, softly etched, and washed with water to clean the surface. Next, they were immersed in the obtained water-soluble preflux at 40°C for 2 minutes to form a film, then washed with water and dried with warm air to obtain a test substrate. Then, the appearance of the test substrate was magnified and observed with an optical microscope at 40 to 200 times to confirm the presence or absence of color unevenness, and the appearance after coating was evaluated according to the following criteria. ○: There is no color unevenness. △: There is slightly color unevenness, but there are no practical problems. ×: There is color unevenness. (3) Repairability A double-sided copper-clad laminate (size: 25 mm × 50 mm, thickness: 1.6 mm, substrate type: FR-4) and a pattern-forming substrate having land opening diameters of φ0.2 mm and φ1.0 mm were degreased, softly etched, and washed with water to clean the surface. Next, they were immersed in the obtained water-soluble preflux at 40°C for 2 minutes to form a film, then washed with water and dried with warm air to obtain a test substrate. 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 film. After that, again, in the same manner as the above steps, the test substrate was softly etched and washed with water to clean the surface. Next, it was immersed in the obtained water-soluble preflux at 40°C for 2 minutes to form a film, then washed with water and dried with warm air to obtain a test substrate. Then, the appearance of the test substrate was magnified and observed with an optical microscope at 40 to 200 times to confirm the presence or absence of color unevenness, and the repairability was evaluated according to the following criteria. Also, the film thickness of the test substrate was compared with that of the test substrate before repair to calculate the film recovery rate (unit: %). ○: There is no color unevenness. △: There is slightly color unevenness, but there are no practical problems. ×: There is color unevenness.

[0026]

Table 1

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

Industrial Applicability

[0028] The water-soluble preflux of the present invention is useful as a manufacturing technique for printed wiring boards or semiconductor substrates.

Claims

1. A water-soluble preflux 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 Claim 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 Claim 1 or Claim 2, the blending amount of the component (A) is 0.02% by mass or more and 1% by mass or less based on 100% by mass of the water-soluble preflux. the blending amount of the component (C) is 0.03% by mass or more and 1% by mass or less based on 100% by mass of the water-soluble preflux. Water-soluble preflux.

4. In the water-soluble preflux according to Claim 1 or Claim 2, not containing a halogen compound. Water-soluble preflux.

5. A printed wiring board having an organic film formed on an electrode terminal by the water-soluble preflux according to Claim 1 or Claim 2. Printed wiring board.

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

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