JPH10280161A - Surface protective agent for copper-gold co-existence substrate and formation of surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form protective films only on the circuit parts consisting of copper based metals without forming insulating films on the surfaces of gold plating layers for contact and contact points of printed circuit boards by preparing an aq. soln. obtd. by incorporating EDTA.2Na compds. into an aq. soln. of specific pH contg. imidazole derivatives, benzimidazole derivatives, aq. acids, metallic compds., etc. SOLUTION: The aq. soln. is prepd. by adding an RNX2 type compd. (IDA deriv.), NX3 type compd. (NTA deriv.), RXNCH2 CH2 NXR type compd. (EDDA deriv.), RXNCH2 CH2 NX2 type compd. etc., as essential components to the aq. soln. of pH 1 to 6 contg. >=1 kinds of the compds. expressed by formula I (R1 is H, a lower alkyl, a halogen atom, R2 is an alkyl and may not be a straight chain (a) is an integer from 0 to 4, (b) is an integer from 0 to 10), formula II (R1 , R2 are each H, a lower alkyl, a halogen atom, R3 is an alkylene and may not be a straight chain, (a), (b) are each an integer from 0 to 4, (c) is an integer from 0 to 10), org. acids, metallic compds., etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a surface protective agent and a surface protective film on a printed wiring board or a metal, and more particularly, to forming an insulating film on the surface of a contact or a gold plating layer of a printed wiring board. A protective film can be formed only on the surface of the circuit part made of copper or copper alloy, and prevents oxidation under high temperature, and improves the wettability, spreadability, and solderability after reflow of the cream solder. The present invention relates to a surface protective agent for a printed wiring board and a method for forming a surface protective film.

[0002]

2. Description of the Related Art A resin coating method, a solder coating method, and the like are used as surface protection methods for forming a surface protection film on a circuit portion made of copper or a copper alloy of a printed wiring board and maintaining solderability. It is roughly divided into coating methods using chemicals. As the above resin coating method, generally, a solution obtained by dissolving a rosin, a synthetic resin, or the like in an organic solvent is applied by a roll coater, or is applied by spraying or dipping on the entire surface of the printed wiring board, and is dried and dried. It is used in a method of forming a film on the surface. Further, the solder coating method is a method of protecting the metal surface of the printed wiring board by coating the molten solder thinly with a leveler or the like. As a coating method using a chemical, a treatment method for forming a film on a metal surface of a printed wiring board using an imidazole derivative or a benzimidazole derivative is disclosed. (Japanese Patent Publication 46-170
No. 46, Japanese Patent Publication No. 46-34214,
-124395, JP-A-5-156475). However, the resin coating method,
In the solder coating method and the chemical coating method, the cumulative formation reaction of the insulating film occurs not only on the surface of the circuit part made of copper or copper alloy on the printed wiring board, but also on the contact of the printed wiring board and the surface of the gold plating layer for contact. In addition to the increase in resistance, the connection reliability is reduced, and the appearance is impaired due to discoloration of the surface of the gold plating layer.

[0003]

The imidazole derivative, the compound containing the benzimidazole derivative as an active ingredient, and the metal salt-containing surface protective agent provide an accumulation of an insulating film on the surface of a contact or a gold plating layer of a printed wiring board. The formation reaction occurs, the contact resistance increases, the connection reliability is reduced, and the appearance is impaired due to the discoloration of the surface of the gold plating layer. SUMMARY OF THE INVENTION An object of the present invention is to provide a printed circuit board with high reliability by forming a protective film only on the surface of a circuit portion made of copper or a copper alloy without forming an insulating film on the surface of a contact or a gold plating layer for contact. An object of the present invention is to provide a method for forming a surface protective agent and a surface protective film on a wiring board.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve such problems, and as a result, have found that the compounds represented by the formulas (1) and (2) have a weight of 0.01 to 10%. %
Into an aqueous solution of pH 1 to 6 containing an organic acid, a metal compound, etc.
0.001 to ETDA · 2Na compound as an essential component
A surface protective agent comprising an aqueous solution containing 30% by weight, preferably a compound having a metal ion concentration (copper ion concentration) of at least equimolar, is coated with an insulating film on the surface of the gold plating layer for contact and contact of a printed wiring board. It was found that a protective film was formed only on the surface of a circuit portion made of copper or a copper alloy without forming the solder, and the wettability and spreadability of the low-melting cream solder even after exposure to high temperatures. The present inventors have found that it is a heat-resistant surface protective agent having good solder removability and wettability after reflow, and have completed the present invention. The compound used as an essential component in the practice of the method of the present invention is an RNX type ₂ compound (IDA derivative), and typical examples of the compound include iminodiacetic acid, iminodipropionic acid, N-methyliminodiacetic acid, N- (3, 3-dimethylbutyl) iminodiacetic acid, phenyliminodiacetic acid, hydroxyethyliminodiacetic acid, mercaptoethyliminodiacetic acid, hydroxyethyliminodipropionic acid, hydroxypropyliminodiacetic acid, 2-hydroxycyclohexyliminodiacetic acid, methoxyethyliminodi Acetic acid, methylthioethyliminodiacetic acid, 2-hydroxybenzyliminodiacetic acid, N- (o
-Carboxyphenyl) iminodiacetic acid, N- (m-carboxyphenyl) iminodiacetic acid, N- (p-carboxyphenyl) iminodiacetic acid, N- (carbamoylmethyl)
Iminodiacetic acid, cyanomethyliminodiacetic acid, aminoethyliminodiacetic acid, β- (N-trimethylammoninium) ethyliminodiacetic acid cation, 2-ethoxycarbonylaminoethyliminodiacetic acid, phosphonomethyliminodiacetic acid, phosphonoethylimino Representative examples of NX type ₃ compounds (NTA derivatives) such as diacetic acid, sulfoethyliminodiacetic acid, o-sulfophenyliminodiacetic acid, m-sulfophenyliminodiacetic acid, and p-sulfophenyliminodiacetic acid Are RXNCH ₂ CH such as nitrilotriacetic acid, carboxyethyliminodiacetic acid, carboxymethyliminodipropionic acid, nitrilotripropionic acid, etc.
Examples of ₂ NXR type compounds (EDDA derivatives) include N, N′-ethylenediaminediacetic acid,
Ethylenediamine-N, N'-dipropionic acid, N,
Typical examples of RXNCH ₂ CH ₂ NX type ₂ compounds such as N′-di (hydroxyethyl) ethylenediaminediacetate include Nn-butylethylenediaminetriacetic acid, N-cyclohexylethylenediaminetriacetic acid,
N- (o-hydroxycyclohexyl) ethylenediaminetriacetic acid, N'-hydroxyethyl-N, N, N'-
NX such as triacetic acid, benzylethylenediaminetriacetic acid
Compounds having _two groups of two or more Examples of representative compounds of (EDTA related compounds), ethylenediaminetetraacetic acid, ethylenediamine -N, N'-diacetic acid N, N '
-Dipropionic acid, ethylenediamine-N, N'-diacetate N, N'-di (2-propionic acid), ethylenediaminetetrapropionic acid, 1,2-propylenediaminetetraacetic acid, trimethylenediaminetetraacetic acid, tetramethylenediamine Tetraacetic acid, pentamethylenediaminetetraacetic acid, hexamethylenedimethyltetraacetic acid, octamethylenediaminetetraacetic acid, 1,2-cyclopentanediaminetetraacetic acid, tran-cyclohexane-1,
2-diaminetetraacetic acid, cyclohexane-1,3-diaminetetraacetic acid, cyclohexane-1,4-diaminetetraacetic acid, 1,3,5-triaminocyclohexanehexaacetic acid, o-phenylenediaminetetraacetic acid, 2-hydroxytrimethylene Diaminetetraacetic acid, ethyletherdiaminetetraacetic acid, ethylthioetherdiaminetetraacetic acid, bis (iminodiacetate) methylamine, diethylenetriaminepentaacetic acid, glycoletherdiaminetetraacetic acid, thioglycolthioetherdiaminetetraacetic acid, trimethylenetetraaminehexaacetic acid, etc. is there. One or two kinds of the above compounds are added to an aqueous solution having a pH of 1 to 6 containing an organic acid, a metal compound and the like in an amount of 0.01 to 10% by weight of a compound represented by the formulas 1 to 8 as an active ingredient.
More than one kind may be added at a ratio of 0.001 to 30% by weight. Preferably, the above compound having an equivalent mole or more of the metal ion concentration (copper ion concentration) may be added. Representative compounds represented by Chemical Formulas 1 to 2 used in the practice of the present invention include 2-alkylbenzimidazole, 2-alkylalkylbenzimidazole, 2-phenylalkylbenzimidazole, 2-alkylphenylbenzimidazole, Alkylphenylalkylbenzimidazole and the like. Examples of organic acids used in the practice of the method of the present invention include acetic acid, iodoacetic acid, bromoacetic acid, dimethylacetic acid, diethylacetic acid, α-bromoacetic acid, paranitrobenzoic acid, paratoluenesulfonic acid, picric acid, oxalic acid, formic acid, Succinic acid, maleic acid, acrylic acid,
Fumaric acid, tartaric acid, adipic acid, lactic acid, oleic acid,
Organic acids such as citric acid, metasulfonic acid, and sulfamic acid; inorganic acids such as hydrochloric acid, sulfuric acid, phosphorous acid, and phosphoric acid; and other carboxylic acids, halogenated fatty acids, and halogenated aromatic carboxylic acids. It may be added at a rate of 0.01 to 20%. One or more of the compounds represented by (Chemical Formula 1) and (Chemical Formula 2) may be added as active ingredients at a ratio of 0.1 to 5% based on the aqueous acid solution. Representative examples of compounds as metal ions used in the practice of the method of the present invention include zinc acetate, zinc formate, zinc lactate,
Zinc citrate, zinc benzoate, zinc oxalate, zinc hydroxide,
Zinc bromide, zinc phosphate, zinc oxide, zinc chloride, lead acetate,
Lead hydroxide, lead bromide, lead iodide, lead oxalate, lead borate, ferrous chloride, ferric chloride, cuprous bromide, cupric bromide, cuprous iodide, copper formate, chloride Nickel, nickel acetate, cuprous chloride, cupric chloride, cuprous oxide, cupric oxide, copper hydroxide, copper phosphate, copper carbonate, copper acetate, copper sulfate, etc. It may be added at a ratio of 0.001 to 5%. In the practice of the present invention, (Chem. 1) to (Chem. 2)
When it is difficult to dissolve the compound represented by the formula and an organic acid, a metal compound, a halogenated aromatic carboxylic acid, or a halogenated fatty acid, emulsification or methanol, ethanol,
Water-soluble solvents such as isopropyl alcohol, butanol, and acetone can be used alone, or can be used in a mixture at an arbitrary ratio. For example, the above-mentioned water-soluble solvent can be used in combination with other organic acids or the like used alone. Particularly, it is difficult to dissolve the compounds represented by (Chemical Formula 1) and (Chemical Formula 2) or the derivatives thereof with the organic acid or the like alone. In such a case, it is preferable to add a water-soluble solvent, and in this case, the content is often appropriate to be 0.01 to 60%. The addition of a buffering substance such as aqueous ammonia or amines to the treatment liquid is effective not only to enhance the pH stability of the aqueous solution but also to increase the film formation rate. In order to apply a rust-proof conversion coating, a heat-resistant conversion coating, or a chemical-resistant conversion coating to the metal surface using the metal surface protective agent of the present invention, the metal is brought into contact with a treatment liquid. As a method of contacting, a method of dipping, spraying, or coating is used. The temperature of the treatment liquid to be contacted is 0 to 100
In a temperature range of preferably 30 to 50 ° C,
The immersion time is several seconds to several tens of minutes, preferably 20 to 12 minutes.
A process of 0 seconds is appropriate.

[0005]

With the compound containing a benzimidazole derivative as an active ingredient and a metal salt-containing surface protective agent, the metal salt contained in the aqueous solution is used for contacting a printed wiring board with a gold plating layer for contact (gold has a high oxidation-reduction potential). Therefore, it acts as a catalyst on the surface of the catalyst and generally does not form a complex), and a cumulative formation reaction involving the complex film occurs on the surface of the contact and contact gold plating layers to form an insulating film. The catalytic action is suppressed by adding an ETDA · 2Na compound to the aqueous solution. With respect to the concealing effect when metal ions (copper ions) are mixed, the same mole as the metal ion concentration (copper ion concentration) is not sufficient, and a film is formed on the gold plating. However, by further adding the ETDA · 2Na compound in excess of the mixed metal ion concentration (copper ion concentration), the film formation can be suppressed without discoloration on gold. From the above results, it is possible to suppress the formation of a film on gold by adding the ETDA · 2Na compound, and the addition amount needs to be equal to or more than the equivalent of the metal ion concentration (copper ion concentration).
A rust-proof chemical conversion coating, a heat-resistant chemical conversion coating, and a chemical-resistant chemical conversion coating are formed on the surface of a metal such as copper or copper alloy. These chemical conversion coatings are water repellent, have excellent rust prevention, moisture resistance, heat resistance, and chemical resistance, protect the metal surface for a long time, and have the wettability, spreadability, low solderability of low melting point cream solder, Good wettability.

[0006]

Example 1 ETDA · 2Na was added to an aqueous solution of PH1-6 containing 0.5% by weight of a compound represented by Chemical Formula 1 or 2 and formic acid, aqueous ammonia, cupric chloride, and ion-exchanged water.
Each type of aqueous solution to which the compound was added in an amount of 0.001 to 30% by weight was prepared, placed in a 100 ml container, and adjusted by heating the liquid temperature to 40 ° C. On the other hand, after performing copper sulfate plating on the glass epoxy double-sided laminated substrate, annealing at 120 ° C. for 1 hour,
2μm nickel plating on half the area of the substrate, 0.1μ
m, followed by degreasing, washing with water, soft etching, washing with water, pickling, washing with water, washing the surface, contacting with an aqueous solution for 60 seconds, washing with water, draining, and drying to prepare a test piece. The contact resistance due to the change in film formation of this test piece is measured. The measurement conditions were 25 gf, 50 gf,
100 gf, load change speed 100 gf / min, stage sliding range 1 mm, applied constant current 10 mA, contact resistance measurement range 20 mΩ, chart feed speed 1 mm / min
Measure with The test results are shown in Table 1.

[Table 1]

[0007]

Example 2 ETDA · 2Na was added to an aqueous solution of PH1-6 containing 0.5% by weight of a compound represented by Chemical Formula 1 or 2 and formic acid, aqueous ammonia, cupric chloride, and ion-exchanged water.
Each type of aqueous solution to which the compound was added in an amount of 0.001 to 30% by weight was prepared, placed in a 100 ml container, and adjusted by heating the liquid temperature to 40 ° C. On the other hand, after performing copper sulfate plating on the glass epoxy double-sided laminated substrate, annealing at 120 ° C. for 1 hour,
2μm nickel plating on half the area of the substrate, 0.1μ
m, followed by degreasing, washing with water, soft etching, washing with water, pickling, washing with water, washing the surface, contacting with an aqueous solution for 60 seconds, washing with water, draining, and drying.
When the film-forming ability on gold and copper and the copper ion increase with the addition amount of the A · 2Na compound, the change in film thickness of the film-forming ability on gold and copper is measured. The test results are shown in Tables 3 and 4 and FIG.

[Table 3]

[Table 4]

FIG.

[0008]

Example 3 ETDA · 2 described in Examples 1 and 2
RNX ₂ type compound, NX ₃ type compound, RXNCH ₂ CH ₂ NXR type compound, RXNCH ₂
A CH ₂ NX type ₂ compound, a compound having two or more NX ₂ groups, each of which was prepared by adding 0.001 to 30% by weight of an aqueous solution, and subjected to the same tests as in Examples 1 and 2,
Comparable results were obtained.

[0009]

COMPARATIVE EXAMPLE The compounds represented by the following formulas (1) to (8) were used in 0.1.
An aqueous solution of PH1 to PH6 containing 5% by weight of formic acid, ion-exchanged water, aqueous ammonia, and cupric chloride was prepared, and the same tests as in Examples 1 and 2 were performed. The test results are shown in Table 2, FIG.
It was shown to.

[Table 2]

[0010]

Industrial Applicability The present invention relates to RNX type ₂ compounds (IDA derivatives), NX type ₃ compounds (NTA derivatives), RXNCH
₂ CH ₂ NXR type compound (EDDA derivative), RXN
By adding a CH ₂ CH ₂ NX type ₂ compound and a compound having two or more NX ₂ groups (an EDTA-related compound), the catalytic action is suppressed, and there is no discoloration on the gold due to the masking effect when copper ions are mixed. The protective film can be formed only on the surface of the circuit part made of copper or copper alloy without forming an insulating film (complex film) on the surface of the contact and the gold plating layer of the printed wiring board, and it can prevent rust, moisture and heat. It has excellent resistance and chemical resistance to protect the metal surface for a long period of time, as well as the wettability, spreadability, and solder reflow properties of low melting point cream solder.
The effect of good wettability can exert a particularly remarkable effect in surface mounting electronic components.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 ETDA · 2N of an aqueous solution of a surface protective agent of the present invention
FIG. 4 is a characteristic diagram showing a relationship between a compound concentration and copper concentration and a thickness of a surface protective film formed on a gold plating layer surface.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideaki Yamaguchi 2-9-7 Wakamiya, Okegawa-shi, Saitama

Claims (2)

[Claims] (1) a compound represented by (Chem. 1) or (Chem. 2),
Or a printed wiring board characterized by being an aqueous solution containing at least one or two or more of these compounds and an organic acid, a metal compound, or the like and having an pH of 1 to 6 and an EDTA / 2Na compound as an essential component. A method for forming a surface protective film, comprising: a step of bringing a metal surface protective agent into contact with an aqueous solution of the surface protective agent; and a step of sequentially performing washing, draining, and drying. Embedded image Embedded image 2. An RNX type ₂ compound (IDA derivative) as an essential component in an aqueous solution of one or more of the compounds represented by the formulas (1) to (2) and pH 1 to 6 containing an organic acid, NX type ₃ compound (NTA derivative), RXNCH ₂
CH ₂ NXR type compound (EDDA derivative), RXNCH
_{2 A} CH ₂ NX type ₂ compound, an aqueous solution containing one or more types of compounds having two or more NX ₂ groups (EDTA-related compounds) or the like, or a print characterized in that the aqueous solution contains a metal compound or the like. A method for forming a surface protective film, comprising: a step of bringing a wiring board or metal into contact with a surface protective agent and an aqueous solution of the surface protective agent; and a step of sequentially performing washing, draining, and drying.