WO2002008491A1

WO2002008491A1 - Palladium removing solution and method for removing palladium

Info

Publication number: WO2002008491A1
Application number: PCT/JP2001/006334
Authority: WO
Inventors: Osamu Kondo; Yoshihiro Watanabe; Fukusaburo Ishihara; Teruhiko Imai
Original assignee: Mitsubishi Gas Chemical Company, Inc.
Priority date: 2000-07-26
Filing date: 2001-07-23
Publication date: 2002-01-31
Also published as: TW539773B; KR100761608B1; JP4649817B2; KR20030015392A

Abstract

A palladium removing solution, characterized in that it comprises (a) a salt of nitric acid, (b) an agent making palladium oxides soluble in water and (c) water. The palladium removing solution may further comprises (d) a wetting solution and/or (e) a chelating agent. The palladium removing solution can be used for removing the palladium remaining on the surface of an insulating substrate and thereby improving the insulating performance of a circuit pattern, without eroding a copper wiring or roughening the surface of the insulating substrate.

Description

Description Palladium removal solution and palladium removal method

The present invention relates to a palladium removing solution and a method for removing palladium using the removing solution, and more particularly, to removing palladium present on the surface of a substrate to be treated without damaging the substrate to be treated. It concerns liquids and removal methods. Background technology ''

An additive method is one of the circuit pattern forming methods. In this additive method, after palladium is applied to the entire surface of the insulating and green substrate, a copper plating layer is formed on the palladium layer by an electroless copper plating method. Only the portion of the copper-plated layer that will become the circuit pattern is covered with an etching resist, and then the copper that is not covered with the resist is removed by etching. After that, the etching resist is removed to form a circuit pattern.

According to this conventional method, the surface of the insulating substrate appears after the circuit pattern is formed, but the palladium remains on the surface of the insulating substrate. Palladium acts as a catalyst during electroless plating, and is effective in easily forming a conductor layer.However, since it is difficult to dissolve in an ordinary etching solution, it remains after the above-described copper etching, and the circuit pattern is reduced. Decreases insulation.

In addition, the entire surface of the circuit pattern or the pad portion for joining the components may be subjected to electroless plating such as electroless plating or electroless plating.However, if palladium remains on the surface of the insulating substrate, However, this palladium acts as a catalyst, and nickel and gold adhere to unneeded portions, thereby deteriorating the insulation of the circuit pattern.

Therefore, removing this residual palladium is extremely important for obtaining high quality circuit boards. Therefore, in the conventional additive method, unnecessary palladium on the substrate surface is removed by the following method after the etching resist is removed. (1) A method in which a substrate is immersed in an iodine-ammonia-iodide solution to dissolve palladium.

(2) A method in which a substrate is immersed in a potassium permanganate solution to dissolve palladium.

(3) Using a vacuum exhaust device such as RIE (reactive ion etching). A method of releasing radium from the substrate surface.

However, the conventional palladium removal method described above has the following problems.

(1) Iodine In the method of immersion in Z-ammonium iodide solution, copper dissolves simultaneously with the dissolution of palladium, so that thinning and disconnection of the wiring are likely to occur.

(2) In the method of dipping in a permanganic acid-based realm solution, the surface of the resin substrate is oxidized, and the surface becomes a fine uneven shape. Since the resin oxidation proceeds faster than the dissolution of palladium, the treatment liquid hardly comes into contact with the palladium present in the concave portions of the resin oxide layer, and palladium residue is partially generated.

(3) The method of using a vacuum pumping device requires a higher cost for manufacturing a wiring board because the device is more expensive than the above wet processing and the number of substrates that can be processed is easily limited.

Also, in Japanese Patent Application Laid-Open Nos. 3-254179 and 419,191, etc., a substrate is immersed in a potassium permanganate solution, and then ultrasonically washed as required. Further, there is disclosed a method of removing palladium by immersion in a solution containing an aromatic nitro compound, an amine compound, an aminocarboxylic acid, a carboxylic acid, sodium hydroxide, and hydroxyammonium sulfate. However, since these removal solutions remove the palladium together with the resin oxide layer on the substrate surface, not only the surface of the substrate is roughened by the permanganic acid-based realm solution, but also the interface between the copper circuit pattern and the substrate is eroded. Have various disadvantages. Disclosure of the invention

An object of the present invention is to provide a removing solution and a removing method for removing palladium present on a surface of a substrate to be processed, which solves the above-mentioned problem, without damaging the substrate to be processed. More specifically, an object of the present invention is to easily remove palladium remaining on the surface of an insulating substrate after forming a circuit pattern in a circuit board manufacturing process. It is an object of the present invention to provide a palladium removing solution that does not corrode a wiring material, an insulating substrate, and the like, and a removing method using the removing solution.

The present inventors have conducted intensive studies to achieve the above object, and have found that (a) nitrate, (b) a solubilizing agent for solubilizing palladium oxide, (c) water, and if necessary, (d) The solution comprising the wetting agent and / or the chelating agent can easily remove palladium remaining on the surface of the insulating substrate after the circuit pattern is formed by the additive method in a short time, improving the insulation of the circuit pattern, They found that a highly reliable printed wiring board could be manufactured, and based on this finding, completed the present invention.

That is, a first aspect of the present invention is a palladium removing solution comprising (a) a nitrate, (b) a solubilizing agent for solubilizing palladium oxide, and (c) water. The removal solution may contain, if necessary, (d) a wetting agent and Z or (e) a printing agent.

According to a second aspect of the present invention, a palladium layer is formed by attaching palladium to the surface of an insulating substrate, a copper plating layer is formed on the palladium layer, a resist is applied to the plating layer, and then etching is performed. This is a palladium removal method in which palladium remaining on the substrate surface is removed using the palladium removal solution after a pattern is formed and the resist is stripped. BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A to 1D are schematic views showing a manufacturing process up to a circuit pattern forming substrate treated with the palladium removing solution of the present invention in manufacturing a printed wiring board. BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the (a) nitrate include ammonium nitrate, lithium nitrate, zinc nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, sodium nitrate, and potassium nitrate, with ammonium nitrate being particularly preferred. Nitrates have the effect of oxidizing palladium. The concentration of the nitrate in the palladium removing solution is from 0.001 to 40% by weight, preferably from 0.005 to 30% by weight.

The substance (water-solubilizing agent) for solubilizing palladium oxide (b) includes inorganic acids and salts thereof, and is preferably hydrochloric acid, nitric acid, sulfuric acid, ammonium chloride, chloride, or the like. Hydrochloride such as aluminum, sulfate such as ammonium sulfate, aluminum sulfate and the like can be mentioned. The concentration of the solubilizer in the palladium-removing solution is from 0.01 to 50% by weight, preferably from 0.05 to 30% by weight.

As long as the effects of the present invention are not impaired, other palladium oxidizing substances are mixed to increase the oxidizing power, or other palladium oxide is solubilized to increase the ability to solubilize palladium oxide. The substances may be mixed.

The palladium removing solution of the present invention may further contain a wetting agent (d) in addition to the components (a) to (c). Examples of the wetting agent (d) include surfactants, alcohols, and ethers. Examples of surfactants include cationic, non-ionic, and anionic surfactants. Examples of alcohols include ethyl alcohol, isopropyl alcohol, butanol, ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. As ethers, ethylene glycolone monoethylene glycol, ethylene glycolone monobutylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ethyl ether, propylene glycol monomethyl alcohol, propylene glycol alcohol Monoethynoleate propylene, propylene glycol-uremonobutyl ethenolate, dipropyleneglycore monomethinole 1-tenore, dipropyrene nicole / lemonoethynooleatenore, dipropylene darico oleno monobutynolate Diethylene glycolo resin methyl ether, dipropylene glycol resin methyl ether, polyoxyethylene methyl phenyl ether, polyoxyethylene etino Hue Nino Les ether Honoré, polyoxyethylene O Chi Roh reflex Eni Honoré ether Honoré, poly Okishiechiren'no phenyl ether and the like.

The above wetting agents can be used alone or in combination of two or more. The concentration of palladium removing solution in the wetting agent 0s. 0 0 1-1 0 weight ^_0/0, preferably 0.0 0 5-5 wt%, particularly preferably 0.0 0 5 to 1 wt% .

The palladium removing solution of the present invention may further contain a chelating agent (e) in addition to the components ( _a ) to ( _c ) or the components ( _a ) to (d). A chelating agent is a compound that forms a complex with palladium, such as dimethyldalioxime, thiourea, thioxin (8-mercaptoquinoline), dithizone, 2-nitrosone naphthol, and p-trosodimethyla-line. Is mentioned. Dimethyl daroxime Urea is particularly preferred.

The chelating agent (e) not only acts as a water-solubilizing agent for the palladium oxide, but also forms a complex with a small amount of palladium that remains in the roughened surface of the insulating substrate, forming a palladium after the circuit pattern is formed. Inactive against electroless nickel plating, electroless gold plating, etc., to prevent nickel and gold from adhering to unnecessary parts and deteriorating circuit pattern insulation.

The concentration of the chelating agent in the palladium-removing solution is 0.01 to 5% by weight, preferably 0.01 to 2% by weight, particularly preferably 0.05 to 2% by weight. / ₀ .

The palladium-removing solution of the present invention is an aqueous solution comprising the above-mentioned nitrate, a solubilizing agent, an optional wetting agent and Z or a chelating agent, and the balance of water. May be suspended overnight, but is usually an aqueous solution.

The palladium-removing solution of the present invention is produced by dissolving, dispersing, or suspending the components (a) to (b) and the optional components (d) and Z or (e) in water. The order of adding each component is not particularly limited.

The method for removing palladium of the present invention is usually carried out by immersing the substrate to be treated in a palladium removing solution at room temperature to 80 ° C. for 1 to 10 minutes. The pH of the palladium removing solution is usually used in the range of 0 to 5. The pH is adjusted by changing the amount of the inorganic acid used as the component (b). The used amount of the palladium removing liquid is an amount that effectively removes palladium from the substrate to be processed, and can be easily determined by those skilled in the art. According to the palladium removal method of the present invention, palladium remaining after the formation of a circuit pattern can be substantially completely removed (the concentration of palladium remaining on the circuit board is 5 ppm or less).

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited by these examples.

Fig. 1 shows the steps up to the formation of a circuit pattern in the manufacture of a circuit board. FIG. 1a shows a state in which a palladium catalyst layer 2 is formed on an insulating substrate 1. This palladium usually exists in an extremely thin layer in a state of being adsorbed on an insulating substrate, and functions as a catalyst in the case of electroless plating.

On the palladium catalyst layer 2 on the surface of the insulating 1 "raw substrate, a conductor layer 3 consisting of a copper plating layer by electroless plating is formed as shown in Fig. 1b. It may be a conductor layer formed by applying electric plating to the attached surface as necessary.

Next, as shown in FIG. 1c, the portion of the conductor layer 3 that is to be a circuit is covered with a photoresist layer 4, and then the uncovered portion of the conductor layer 3 is dissolved and removed with an etchant. In this case, as the resist, for example, a dry photo film, a photoresist ink, a screen printing resist, or the like can be used. As the etching solution, a mixed solution of sulfuric acid and hydrogen peroxide, a cupric chloride-containing solution, a ferric chloride Liquids and the like can be used.

After the etching, by removing the photoresist, a conductive circuit 3a is formed on the surface of the insulating substrate 1 as shown in FIG. 1d. After etching the copper plating layer, the palladium 2a attached to the surface of the insulating substrate 1 is not removed and remains as it is adsorbed on the insulating resin.

Examples 1 to 7

The above-mentioned palladium residual circuit board was immersed in a predetermined condition using a palladium removing solution shown in Table 1, then rinsed with pure water and dried. After that, measure the insulation resistance value of the circuit part where the circuit interval is 20 microns, measure the residual amount of palladium on the surface of the insulating substrate by X-ray fluorescence analysis and X-ray microanalyzer, and electroless nickel plating on the circuit pattern part In the test, the presence or absence of nickel on the surface of the insulating substrate and the corrosiveness of copper in the circuit pattern were observed. The measurement results and the observation results were evaluated according to the following criteria. Table 1 shows the results.

1 Insulation

A: Number of insulation resistance before treatment 数 Ω → Insulation resistance after treatment ∞

C: Number of insulation resistance before treatment Μ Ω → Number of insulation resistance after treatment Μ Ω 2 Palladium removal property

Α: Completely removed.

B: Partially remained.

C: Mostly remained.

3 Nickel deposition

A +: No precipitation was observed at all.

A: Almost no precipitation was observed.

B: Partial precipitation was observed. c: Precipitation was observed.

4 Copper corrosion

A No corrosion was observed

B—Corrosion was observed.

C Corrosion was observed on the entire surface

Palladium removal solution set Jt

Solubilizing agent Combination agent 7 kinds concentration concentration concentration concentration concentration concentration

(Wt ^_0/0) (wt ^_0/0) (wt ^_0/0) (wt%) Example

1 Ammonic nitrate 2 Hydrochloric acid 5 Remaining nickel

2 Ammonate nitrate 5 Hydrochloric acid 5 Remaining nickel

3 Ammonium nitrate 0.5 Hydrochloric acid 5 Remaining nickel

4 Ammonium nitrate 2 Hydrochloric acid 1 a 氺 3 Remaining nickel

5 Ammonate nitrate 2 Hydrochloric acid 1 b * 0.1

Nimu

6 2 sulfuric acid 3

Nimu

7 Ammonium nitrate 2 Nitric acid 5 Remaining nickel

a * =: isopropino 'arco' —

b * =: Polyoxynoyurfe-Ninoreethenore

(Continued)

Removal conditions Evaluation results

Temperature Time

Insulation Pd removal Ni precipitation Cu corrosion

CO (min)

Example

60 5 A A A A

2 60 5 AAAA 3 70 5 AAAA 4 50 3 AAAA 5 50 3 AAAA 6 60 5 AAAA 7 60 5 AAAA Comparative Examples 1 to 8

Example 7 was carried out in the same manner as in Example 7 except that a palladium removing solution having the composition shown in Table 3 was used. The experimental results are shown in Table 2. Table 2

組成 Composition of radium removal solution

Nitrate solubilizer wetting agent water concentration concentration

(Wt%) (wt%) (wt ^_0/0) (wt ^_0/0) Comparative Example

1 Ammonate nitrate 5 Remaining nickel

2 Hydrochloric acid 5 balance

3 Sulfuric acid 3 balance

4 Ammonium chloride 5 Balance Monium

5 Ammonate nitrate 5 a * 3 Remaining nickel

6 Ammonate nitrate 5 b * 0.1 balance Yuum

7 5 a 氺 3 balance

8 Ammonium chloride 5 a * 3 Balance monium

a * = isopropyl alcohol

b * = polyoxyethylene noninolefe-norethene Table 2 (continued)

Removal conditions Evaluation results

Temperature Time

Insulation Pd removal Ni precipitation Cu corrosion

CO (min)

Comparative example

60 5 CCCA 60 5 BBCA 3 60 5 CCCA 4 60 5 CCCA 5 60 5 CCCA 6 60 5 CCCA 7 60 5 BBCA 8 60 5 CCCA

Examples 8 to 9

Example 7 was carried out in the same manner as in Example 7, except that a palladium removing solution containing a chelating agent was used. Table 3 shows the results. Table 3

組成 Composition of radium removal solution

Door salt water solubilizer chelating agent water concentration

(Weight ^_0/0) (weight ^_0/0) (wt.%)

Example

8 Ammonate nitrate 2 c *

Nimu

9 Ammonate nitrate 2 d 氺 0.1 Remaining nickel

c * = dimethinoregrioxime

d Thiourea Table 3 (continued)

Removal conditions Evaluation results

Temperature Time

Insulation Pd removal Ni precipitation Cu corrosion (.C) (min)

Example

8 50 3 AAA ⁺ A

9 50 3 A A A A + A Industrial potential

By immersing in the palladium removing solution of the present invention, palladium present on the surface of the substrate to be processed can be removed. The palladium removing solution of the present invention is particularly It is suitable for removing palladium remaining on the surface of a flexible substrate, does not erode copper wiring, and does not roughen the surface of an insulating substrate, thereby improving the insulation of a circuit pattern. be able to.

In addition, even when the circuit pattern is subjected to plating treatment such as electroless nickel plating or electroless gold plating, the palladium on the surface is removed, so that the deterioration of insulation due to the adherence to the surface of the insulating substrate is reduced. It can be prevented beforehand.

Claims

The scope of the claims

1 A palladium removing solution comprising (a) a nitrate, (b) a solubilizing agent for solubilizing palladium oxide, and (c) water.

2. The palladium removing solution according to claim 1, wherein the concentration of the nitrate is 0.01 to 40% by weight, the concentration of the solubilizing agent is 0.01 to 50% by weight, and the balance is water.

3. The method according to claim 1, wherein the nitrate is at least one compound selected from the group consisting of ammonium nitrate, lithium nitrate, zinc nitrate, manganese nitrate, Eckel nitrate, cobalt nitrate, sodium nitrate, and potassium nitrate. 4. Palladium removal solution. 4 The method according to any one of claims 1 to 3, wherein the solubilizer is at least one compound selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, ammonium chloride, aluminum chloride, ammonium sulfate, and aluminum sulfate. The described palladium removal solution.

5 (d) The palladium removing solution according to any one of claims 1 to 4, further comprising a wetting agent.

6. The palladium removing solution according to claim 5, wherein the concentration of the wetting agent is 0.0001 to 10 parts by weight.

7. The palladium removing solution according to claim 5, wherein the wetting agent is a surfactant, an alcohol, or an ether.

8. The palladium removing liquid according to claim 7, wherein the surfactant is a cationic, non-on, or anionic surfactant.

9. The alcohol is at least one alcohol selected from the group consisting of ethyl alcohol, isopropyl alcohol, butanol, ethylene glycolone, diethylene glycolone, propylene glycolone, and dipropylenedaricol. The palladium removal solution described.

10 The above ethers are ethylene glycol monomethyl ether ether, ethylene glycol ethylene glycol monomethyl alcohol, ethylene glycol glycol monomethyl alcohol, polyethylene glycol monoethyl alcohol, ethylene glycol glycol monoethyl alcohol Ether, propylene glycol monomethinoleate, propylene glycol monoleate, propylene glycolone monobutyrate, dipropylene daricole monomethyoleate, dipropylene glycolone methylate Ter, Dipropi Polyethylene glycol dimethinoleate, Polyethylene glycol dimethinoleate, Polyoxyethylene methylenoate, Polyoxyethylene ethizolephenoleate, Polyoxyethylene 8. The palladium removing solution according to claim 7, which is at least one ether selected from the group consisting of cutinole fenoleate zolet, and polyoxyethylene nonolenofenote oleate / re.

The palladium removing solution according to any one of claims 1 to 10, further comprising 11 (e) a chelating agent.

12. The palladium-removing solution according to claim 11, wherein the concentration of the chelating agent ranges from 0.01 to 5% by weight.

13 The chelating agent is at least one selected from the group consisting of dimethyldalioxime, thiourea, thioxine (8-mercaptoquinoline), dithizone, 2_-trossou 1-naphthol / re, and p--trosodimethylaniline The palladium removal solution according to claim 11 or 12, which is one compound.

14. The palladium removing liquid according to any one of claims 1 to 13, which is used in the manufacture of a circuit board by an additive method of forming a circuit pattern by a copper plating layer formed on a surface of an insulating substrate.

15 Palladium is adhered to the surface of the insulating substrate to form a palladium layer, a copper plating layer is formed on the palladium layer, a resist is applied to the plating layer, and then the resist is peeled off. A palladium removal method for removing palladium remaining on the surface of an insulating substrate using the palladium removal solution according to any one of claims 1 to 13 after forming the palladium.