JP5018226B2 - Conductive film forming ink - Google Patents

Description

  The present invention relates to a conductive film forming ink and a method for producing a printed wiring board.

  In recent years, with the development of electronic products, the demand for printed wiring boards impregnated with an insulating resin continues to increase. Above all, the increase in demand for flexible printed wiring boards is remarkable. The printed wiring board is obtained by forming a conductive film having a desired wiring pattern on an electrical insulator layer. As the electrical insulator layer, a resin base material such as phenol resin, epoxy resin, polyester, polyimide, or a glass cloth or paper base material impregnated with any of them, a metal base material, a ceramic base material Is used.

A printed wiring board is usually manufactured by a manufacturing method having the following steps.
(I) A step of forming a conductive film on the entire surface of the electrical insulator layer.
(Ii) A step of applying a resist solution to the entire surface of the conductive layer to form a resist film.
(Iii) A step of exposing the resist film through a photomask having a desired wiring pattern.
(Iv) A step of developing the resist film to form a resist having a desired wiring pattern.
(V) A step of etching the conductive film with an etching solution.
(Vi) A step of removing the resist.

However, this method has the following problems.
There are many processes.
There is a lot of waste.
An expensive photomask is required for each pattern.

As a method for solving the problem, a method of forming a conductive film having a desired wiring pattern by applying a metal fine particle dispersion in a desired wiring pattern on the surface of an electrical insulator layer has been proposed (for example, Patent Document 1). However, since the conductive film formed by this method has insufficient adhesion to the electric insulator layer, an intermediate material layer must be formed between the electric insulator layer and the conductive film. Therefore, there are problems such as an increase in the number of processes and an increase in cost.
JP 2006-7135 A

  The present invention provides a conductive film forming ink capable of forming a conductive film excellent in adhesion with an electrical insulator layer containing polyimide, a printed wiring board having a conductive film excellent in adhesion with an electrical insulator layer containing polyimide, Provided is a method for producing a printed wiring board which can be produced with a small number of processes.

The ink for forming a conductive film of the present invention is a conductive film forming ink for forming a conductive film on the surface of an electrical insulator layer containing polyimide, and has a boiling point of 150 to 350 ° C. at a pressure of 0.1 MPa. a water-insoluble organic solvent is, seen containing metal particles and / or metal hydride fine particles dispersed in the organic solvent, an amino compound is an amine value prescribed in JIS K7237 is 40 ~ 120 mg KOH / g, The amount of the amino compound is 1 to 50 parts by mass with respect to 100 parts by mass in total of the metal fine particles and metal hydride fine particles .

According to the conductive film forming ink of the present invention, it is possible to form a conductive film that is excellent in adhesion to an electrical insulator layer containing polyimide.
According to the method for producing a printed wiring board of the present invention, a printed wiring board having a conductive film excellent in adhesion to an electrical insulator layer containing polyimide can be produced in a small number of steps.

<Ink for forming conductive film>
The ink for forming a conductive film of the present invention includes a water-insoluble organic solvent (hereinafter referred to as an organic solvent) having a boiling point of 150 to 350 ° C. under a pressure of 0.1 MPa, and a metal dispersed in the organic solvent. Fine particles and / or metal hydride fine particles (hereinafter, metal fine particles and metal hydride fine particles are collectively referred to as “fine particles”) and an amino compound having an amine value of 10 to 190 mgKOH / g according to JIS K7237. .

(Organic solvent)
The organic solvent needs to be water-insoluble. Water-insoluble means that the solubility in 100 g of water at room temperature (20 ° C.) is 0.5 g or less.
As an organic solvent, a thing with little polarity is preferable. An organic solvent having a small polarity has good affinity with an amino compound used as a dispersant in the present invention.
As the organic solvent, those which do not cause thermal decomposition by heating when the conductive film is formed are preferable.

  The boiling point of the organic solvent is 150 to 350 ° C. and preferably 200 to 280 ° C. at a pressure of 0.1 MPa. If the boiling point of the organic solvent is 150 ° C. or higher, the reaction between the amino compound of the conductive film forming ink and the polyimide of the electrical insulator layer is caused by the organic solvent remaining in the coating film for a relatively long time when the conductive film is formed. Occurs sufficiently, and as a result, the adhesion between the conductive film and the electrical insulator layer is improved. If the boiling point of the organic solvent is 350 ° C. or lower, the firing time for forming the conductive film can be shortened.

  Organic solvents include decane (boiling point 174 ° C., insoluble in water), dodecane (boiling point 216 ° C., insoluble in water), tetradecane (boiling point 253 ° C., insoluble in water), decene (boiling point 171 ° C., insoluble in water). ), Dodecene (boiling point 216 ° C., insoluble in water), tetradecene (boiling point 234 ° C., insoluble in water), dipentene (boiling point 177 ° C., solubility in 100 g of water 0.001 g (20 ° C.)), terpineol ( One or more selected from the group consisting of a boiling point of 219 ° C., a solubility of 0.5 g (20 ° C.) in 100 g of water, and mesitylene (boiling point of 165 ° C., insoluble in water). The boiling point is a value at a pressure of 0.1 MPa.

  The amount of the organic solvent is such that the concentration of the fine particles in the conductive film forming ink does not deviate from the range described below, and is preferably 65 to 500 parts by weight, and 125 to 500 parts by weight with respect to 100 parts by weight of the metal fine particles. Is more preferable. When the amount of the organic solvent is 65 parts by mass or more with respect to 100 parts by mass of the fine particles, ink characteristics such as viscosity and surface tension of the conductive film forming ink are improved, and handling properties are improved. When the amount of the organic solvent is 500 parts by mass or less with respect to 100 parts by mass of the fine particles, a sufficiently thick conductive film can be formed.

(Fine particles)
As the fine particles, metal fine particles and / or metal hydride fine particles can be appropriately used depending on the intended use, but metal hydride fine particles are preferable from the viewpoint of stability and storage stability.
Examples of the metal fine particles include metal copper fine particles, metal nickel fine particles, and metal palladium fine particles. From the viewpoint that a conductive film having excellent conductivity can be formed, metal copper fine particles or metal nickel fine particles are preferable, and metal copper fine particles are more preferable.
The metal fine particles are preferably produced by a wet reduction method described later.

  The metal hydride fine particles are metal hydride fine particles in which metal atoms and hydrogen atoms are bonded. The metal hydride fine particles are less oxidized in the air atmosphere than the metal fine particles, are stable, and have excellent storage stability. Since metal hydride fine particles have the property of decomposing into metal and hydrogen at 60 to 100 ° C., when forming a conductive film, a metal oxide film is hardly formed on the surface of the fine particles by heating. The generated metal fine particles are immediately melted and bonded by the property of the surface melting phenomenon to form a conductive film having excellent conductivity.

Examples of the metal hydride fine particles include copper hydride fine particles, nickel hydride fine particles, and palladium hydride fine particles. From the viewpoint that a conductive film having excellent conductivity can be formed, copper hydride fine particles or nickel hydride fine particles are preferable. Copper hydride fine particles are more preferable.
The metal hydride fine particles are preferably produced by a wet reduction method described later.

The average particle size of the fine particles is preferably 50 nm or less, and more preferably 5 to 30 nm. If the average particle diameter of the fine particles is 50 nm or less, a fine wiring pattern can be formed. Further, since the surface melting temperature is lowered, surface fusion is likely to occur. In addition, a dense conductive film can be formed, and conductivity is improved.
The average particle size of the fine particles was determined by measuring the particle size of 100 randomly extracted fine particles using a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and averaging the particle sizes. Value.

  The concentration of the fine particles is preferably 5 to 60% by mass and more preferably 10 to 50% by mass in 100% by mass of the conductive film forming ink. When the concentration of the fine particles is 5% by mass or more, a conductive film having a sufficient thickness can be formed, and the conductive film is improved. When the concentration of the fine particles is 60% by mass or less, ink properties such as viscosity and surface tension of the conductive film forming ink are improved, and handling properties are improved.

(Amino compound)
The amino compound is an organic compound having an amino group or a salt thereof. The amino compound is a primary amine or a secondary amine, and a primary amine is preferable from the viewpoint that a reaction with the polyimide of the electrical insulator layer easily occurs.

As the amino compound, a high molecular amino compound is preferable. As the polymer amino compound, the following commercially available products are preferable.
Big Chemie Japan, Inc .: Anti-Terra-U (a salt of a long-chain polyaminoamide and an acid polymer, amine value 19 mgKOH / g), Anti-Terra-204 (polyaminoamide polycarboxylate, amine value 36 mgKOH / g) Disperbyk-101 (salt of long-chain polyaminoamide and polar acid ester, amine value 14 mgKOH / g), Disperbyk-106 (polymer salt having an acidic group, amine value 74 mgKOH / g), Disperbyk-108 (hydroxyl group-containing carboxylic acid) Ester, amine value 71 mgKOH / g), Disperbyk-109 (alkylol aminoamide, amine value 140 mgKOH / g), Disperbyk-112 (acrylic copolymer having affinity for pigment, amine value 36 gKOH / g), Disperbyk-116 (acrylic copolymer having an affinity for pigment, amine value 65 mgKOH / g), Disperbyk-130 (unsaturated polycarboxylic acid polyaminoamide, amine value 190 mgKOH / g), Disperbyk-140 (Ammonium salt of acidic polymer, amine value 76 mgKOH / g), Disperbyk-142 (phosphate ester salt of copolymer having affinity for pigment, amine value 43 mgKOH / g), Disperbyk-145 (affinity to pigment) Phosphate ester salt of a certain copolymer, amine value 71 mgKOH / g), Disperbyk-161 (block copolymer having affinity for pigment, amine value 11 mgKOH / g), Disperbyk-162 (block having affinity for pigment) Polymer, amine value 13 mgKOH / g), Disperbyk-164 (block copolymer having affinity for pigment, amine value 18 mgKOH / g), Disperbyk-166 (block copolymer having affinity for pigment, amine value 20 mgKOH / G), Disperbyk-167 (block copolymer having affinity for pigment, amine value 13 mgKOH / g), Disperbyk-168 (block copolymer having affinity for pigment, amine value 10 mgKOH / g), Disperbyk- 2000 (modified acrylic block copolymer, amine value 4 mgKOH / g), Disperbyk-2001 (modified acrylic block copolymer, amine value 29 mgKOH / g), Disperbyk-2020 (modified acrylic block copolymer, amine value) 38 mgKOH / g), Disperbyk-2050 (acrylic copolymer having affinity for pigment, amine value 30 mgKOH / g), Disperbyk-2070 (acrylic copolymer having affinity for pigment, amine value 20 mgKOH / g) Disperbyk-2150 (block copolymer having affinity for pigment, amine value 57 mgKOH / g).

Kawaken Fine Chemicals: Hinoact KF1500 (cationic surfactant single anchor type, amine value 7 mgKOH / g), Hinoact KF1700 (cationic surfactant single anchor type, amine value 2 mgKOH / g).
Ajinomoto Fine Techno Co., Ltd .: Ajisper PB821 (basic polymer dispersant, amine value 9 mgKOH / g), Azisper PB822 (basic polymer dispersant, amine value 13 mgKOH / g), Azisper PB711 (basic polymer dispersant, Amine value 45 mg KOH / g).
Made by Enomoto Kasei Co., Ltd .: Disparon 1860 (Salt of long-chain polyaminoamide and high molecular polyester acid; amine value 11 mgKOH / g), Disparon KS873N (Amine salt of polyester, amine value 120 mgKOH / g), Disparon DA703-50 (high molecular weight) Polyamide acid amide amine salt, amine value 40 mgKOH / g), Disparon DA7400 (high molecular weight polyester acid amide amine salt, amine value 40 mgKOH / g).
Ciba Specialty Chemicals: EFKA-4401 (modified polyacrylic polymer dispersant, amine value 50 mgKOH / g), EFKA-5044 (unsaturated polyester polyamide, amine value 16 mgKOH / g), EFKA-5207 (hydroxyl group) Unsaturated carboxylic acid containing, amine value 85 mgKOH / g), EFKA-6225 (fatty acid-modified polyester, amine value 47 mgKOH / g), EFKA-4330 (acrylic block copolymer polymer dispersant, amine value 28 mgKOH / g), EFKA- 4047 (modified polyurethane polymer dispersant, amine value 17 mgKOH / g), EFKA-4060 (modified polyurethane polymer dispersant, amine value 8 mgKOH / g).

The amine value of the amino compound is 10 to 190 mgKOH / g, preferably 40 to 120 mgKOH / g. When the amine value of the amino compound is 10 mgKOH / g or more, sufficient reaction between the amino compound of the conductive film forming ink and the polyimide of the electrical insulator layer occurs. When the amine value of the amino compound is 190 mgKOH / g or less, there is no reduction in mechanical strength of the electrical insulator layer, and a conductive film having excellent adhesion to the electrical insulator layer can be formed.
The amine value is measured based on JIS K7237 as follows.
An amino compound is dissolved in a mixed solvent of o-nitrotoluene and acetic acid, and titrated with a 0.1 mol / L perchloric acid acetic acid solution using crystal violet as an indicator. The total amine number is calculated by the amount of 0.1 mol / L perchloric acid acetic acid solution consumed.

  The amount of the amino compound is such that the concentration of the fine particles in the conductive film forming ink does not deviate from the above range, and is preferably 1 to 50 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the fine particles. preferable. When the amount of the amino compound is 1 part by mass or more with respect to 100 parts by mass of the fine particles, a conductive film having excellent adhesion can be formed. When the amount of the amino compound is 50 parts by mass or less with respect to 100 parts by mass of the fine particles, a conductive film having good conductivity can be formed.

(Other ingredients)
The ink for forming a conductive film may contain a known additive, an organic binder, or the like as necessary.

(Method for producing conductive film forming ink)
The conductive film forming ink includes, for example, (α) a method of preparing commercially available fine particles and dispersing the fine particles in an organic solvent in the presence of an amino compound, and (β) a wet reduction method that includes an amino compound. It can be produced by a method for producing a dispersion of the fine particles. Examples of the method (β) include a method having the following steps.
(A) A step of preparing an aqueous solution containing metal ions by dissolving a water-soluble metal compound in water.
(B) A step of adjusting the pH to 3 or less by adding an acid to the aqueous solution.
(C) A step of adding an organic solvent and an amino compound to the aqueous solution and then stirring them to obtain a suspension.
(D) While stirring the suspension, a step of adding a reducing agent to the suspension to reduce metal ions to produce metal hydride fine particles (wet reduction method).
(E) A step of separating the suspension into an aqueous layer and an oil layer, and then collecting the oil layer as a dispersion of metal hydride fine particles.
(F) A step of using a dispersion of metal hydride fine particles as a dispersion of metal fine particles as necessary.

(A) Process:
Examples of the water-soluble metal copper compound include sulfates, nitrates, acetates, chlorides, bromides, iodides of metals (copper, nickel, palladium).
The concentration of the water-soluble metal compound is preferably 0.1 to 30% by mass in 100% by mass of the aqueous solution. When the concentration of the water-soluble metal compound in the aqueous solution is 0.1% by mass or more, the amount of water can be suppressed, and the production efficiency of the fine particles can be improved. When the concentration of the water-soluble metal compound in the aqueous solution is 30% by mass or less, the aggregation stability of the fine particles is good.

(B) Process:
Examples of acids include citric acid, maleic acid, malonic acid, acetic acid, propionic acid, sulfuric acid, nitric acid, hydrochloric acid, etc., and form a stable complex with metal ions to prevent adsorption of hydration water to metal ions. From the viewpoint, citric acid, maleic acid, and malonic acid are preferable.
By adjusting the pH of the aqueous solution to 3 or less, metal ions in the aqueous solution are easily reduced by the reducing agent, and metal hydride fine particles are easily generated. That is, it becomes difficult to produce fine metal particles. The pH of the aqueous solution is preferably adjusted to 1 to 2 because metal hydride fine particles can be generated in a short time.

(C) Process:
(B) An organic solvent and an amino compound are added to the aqueous solution obtained in the step. A suspension is obtained by stirring an aqueous layer composed of an aqueous solution containing metal ions and an oil layer composed of an organic solvent containing an amino compound.

(D) Process:
By adding a reducing agent to the suspension obtained in step (c), metal ions are reduced by the reducing agent under acidic conditions in the aqueous layer, and metal hydride fine particles grow gradually. The metal hydride fine particles are immediately covered with an amino compound dissolved in the oil layer, and taken into the oil layer and stabilized. That is, the amino compound is coordinated on the surface of the generated metal hydride fine particles, and the metal hydride fine particles are coated with the amino compound. As a result, the metal hydride fine particles in the conductive film forming ink are hardly oxidized, and aggregation of the metal hydride fine particles is suppressed.

  As the reducing agent, a metal hydride is preferable because it has a large reducing action. Examples of metal hydrides include lithium aluminum hydride, lithium borohydride, sodium borohydride, lithium hydride, potassium hydride, calcium hydride, and the like. Lithium aluminum hydride, lithium borohydride, borohydride Sodium is preferred.

The amount of the reducing agent added is preferably 1.5 to 10 times the number of metal ions. If the addition amount of the reducing agent is 1.5 times the number of equivalents or more with respect to the metal ions, the reducing action is sufficient. When the addition amount of the reducing agent is 10 times or less, the aggregation stability of the metal hydride fine particles becomes good.
5-60 degreeC is preferable and, as for the temperature at the time of adding a reducing agent to suspension, 10-40 degreeC is especially preferable. When the temperature is 60 ° C. or lower, decomposition of the metal hydride fine particles can be suppressed.

(E) Process:
After the metal hydride fine particles are generated, if the suspension is allowed to stand, it is separated into an aqueous layer and an oil layer. By collecting the oil layer, a dispersion liquid in which metal hydride fine particles are dispersed in an organic solvent is obtained. The dispersion may be used as it is as an ink for forming a conductive film, or may be used as an ink for forming a conductive film after adding an additive or the like.

(F) Process:
When the dispersion of metal hydride fine particles obtained in the step (e) is refluxed with nitrogen at 60 to 200 ° C. for 10 minutes to 2 hours, a dispersion of metal fine particles is obtained. The dispersion may be used as it is as an ink for forming a conductive film, or may be used as an ink for forming a conductive film after adding an additive or the like.

<Printed wiring board>
FIG. 1 is a cross-sectional view showing an example of a printed wiring board. The printed wiring board 10 includes an electrical insulator layer 12 and a conductive film 14 that is in direct contact with the electrical insulator layer 12.

The electrical insulator layer 12 is a layer containing polyimide. The electrical insulator layer 12 includes a polyimide film, a polyimide layer formed as the outermost layer of the laminated film, a polyimide layer formed as the outermost layer of the laminated substrate, a glass fiber reinforced composite material in which the matrix resin is polyimide, and a matrix resin. Examples thereof include a silica composite film that is polyimide. When a flexible polyimide film is used as the electrical insulator layer 12, the printed wiring board 10 is a flexible printed wiring board.
10-300 micrometers is preferable and, as for the thickness of the electrical insulator layer 12, 10-200 micrometers is more preferable.

Examples of the polyimide include a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine. Examples of the aromatic tetracarboxylic dianhydride include 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride. Examples of the aromatic diamine include paraphenylene diamine and 4,4′-diaminodiphenyl ether.
The polyimide may contain known additives such as inorganic fillers, inorganic phosphors, and organic phosphors.

The conductive film 14 is a metal film formed using the conductive film forming ink of the present invention. The conductive film 14 may be a continuous film covering the entire surface of the electrical insulator layer 12 or a film having a desired wiring pattern.
The volume resistivity of the conductive film 14 is preferably 500 μΩcm or less, and more preferably 100 μΩcm or less.
0.5-10 micrometers is preferable and, as for the thickness of the electrically conductive film 14, 0.5-5 micrometers is more preferable.

  The printed wiring board is not limited to a single-sided printed wiring board in which a conductive film is provided only on one side of the electrical insulator layer, as shown in FIG. 1, and double-sided printing in which a conductive film is provided on both sides of the electrical insulator layer. A wiring board may be sufficient and the multilayer printed wiring board which laminated | stacked the single-sided printed wiring board may be sufficient.

The printed wiring board 10 is manufactured through the following steps.
(I) A step of applying the ink for forming a conductive film of the present invention to the surface of the electrical insulator layer 12 to form a coating film.
(II) A step of baking the coating film to form the conductive film 14.
(III) A step of plating on the conductive film as necessary.

(I) Process:
In this step, the conductive film forming ink of the present invention may be applied so as to cover the entire surface of the electrical insulator layer 12, and the conductive film forming ink of the present invention is applied to the surface of the electrical insulator layer 12 as desired. It may be applied in a wiring pattern.

  As the coating method, known methods such as inkjet printing method, dispensing method, screen printing method, roll coating method, air knife coating method, blade coating method, bar coating method, gravure coating method, die coating method, spray coating method, slide coating method, etc. In view of easy application to a desired wiring pattern, inkjet printing is preferred.

The ink jet printing method is a method using an ink jet printer. The ink discharge hole in the ink jet printer is usually 1 to 50 μm.
The ink droplet diameter is changed when flying in space after being ejected from the ink ejection holes, and is spread on the surface of the electrical insulator layer 12 after adhering to the surface of the electrical insulator layer 12. The diameter of the ink immediately after ejection is about the same as the diameter of the ink ejection hole, and after adhering to the electrical insulator layer 12, the diameter of the ink expands to 5 to 100 μm. Therefore, the fine particles in the conductive film forming ink may be aggregated as long as the ink viscosity is not affected, and the aggregate diameter is preferably 2 μm or less.

(II) Process:
The electrical insulator layer 12 on which the coating film is formed is placed in a firing furnace, and the temperature in the firing furnace is increased to a firing temperature at a rate of 10 ° C./min in an inert gas atmosphere such as nitrogen gas. Firing is carried out while holding the temperature for a predetermined time (hereinafter referred to as holding time). By the firing, fusion of the fine particles proceeds, and a conductive film made of metal is formed.

  The firing temperature is preferably 250 to 450 ° C, more preferably 300 to 400 ° C, and particularly preferably 300 to 350 ° C. When the firing temperature is 250 ° C. or higher, the reaction between the amino compound of the conductive film forming ink and the polyimide of the electrical insulator layer occurs sufficiently, and as a result, the adhesion between the conductive film and the electrical insulator layer is good. Become. When the firing temperature is 450 ° C. or lower, unnecessary ring-opening reaction of the polyimide imide ring is suppressed, deterioration of the polyimide is suppressed, and a decrease in mechanical strength of the printed wiring board is suppressed.

  The holding time is preferably 0.5 to 4 hours, and more preferably 0.5 to 2 hours. If the holding time is 0.5 hours or more, the reaction between the amino compound of the conductive film forming ink and the polyimide of the electrical insulator layer occurs sufficiently, and as a result, the adhesion between the conductive film and the electrical insulator layer is improved. It becomes good. If holding time is 4 hours or less, the unnecessary ring-opening reaction of the imide ring of a polyimide is suppressed, the deterioration of a polyimide is suppressed, and the fall of the mechanical strength of a printed wiring board is suppressed.

(III) Process:
When plating is performed on the conductive film, a known method may be used. For example, in the aqueous solution (plating bath) in which the metal is melted and ionized, the treatment object is immersed as the cathode, and the same metal as the plating is immersed as the anode, and a current flows between both electrodes. As a result, the metal ions in the plating bath move to the cathode, exchange electrons on the surface of the treatment object, are reduced to the original metal, and are deposited to form a plating layer.

In the ink for forming a conductive film of the present invention described above, a water-insoluble organic solvent having a boiling point of 150 to 350 ° C. at a pressure of 0.1 MPa, the fine particles dispersed in the organic solvent, Since it contains an amino compound having an amine value of 10 to 190 mgKOH / g according to JIS K7237, a conductive film having excellent adhesion to an electrical insulator layer containing polyimide can be formed.
In the method for producing a printed wiring board of the present invention, the conductive film-forming ink of the present invention is applied to the surface of the electrical insulator layer to form a coating film, and the coating film is baked to form a conductive film. Therefore, a printed wiring board having a conductive film with excellent adhesion to an electrical insulator layer containing polyimide can be manufactured with a small number of steps.
The reason is as follows.

  When the amino compound is a primary amine, as shown in the following reaction formula (A), in the presence of an organic solvent, a part of the polyimide imide ring present in the surface layer of the electrical insulator layer and the amino group of the amino compound are: Reaction occurs at the calcination temperature, and two amide bonds are formed. Next, as shown in the following reaction formula (B), when the imide ring is formed again, the main chain of the polyimide is divided, and the molecular weight of the polyimide is lowered. Since the low molecular weight polyimide has a lower glass transition point than the polyimide before the low molecular weight reduction, softening easily occurs. Therefore, the fine particles can sink into the polyimide softened in the surface layer of the electrical insulator layer. Thus, since the fine particles sink into the surface layer of the electrical insulator layer, the adhesion between the conductive film and the electrical insulator layer is improved by the anchoring effect.

  When the amino compound is a secondary amine, as shown in the following reaction formula (A), in the presence of an organic solvent, a part of the polyimide imide ring present in the surface layer of the electrical insulator layer and the amino group of the amino compound are The reaction occurs at the firing temperature to form two amide bonds. A polyimide in which a part of the imide ring is an amide bond also has a low glass transition point because the imide bond is reduced as compared with the polyimide before the reaction, and thus is easily softened. Therefore, the fine particles can sink into the polyimide softened in the surface layer of the electrical insulator layer. Thus, since the fine particles sink into the surface layer of the electrical insulator layer, the adhesion between the conductive film and the electrical insulator layer is improved by the anchoring effect.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
Example 3 is an example, and examples 1, 2, 4 to 8 are comparative examples.

(Identification of the fine particles)
The identification of the fine particles was performed using RINT2500 manufactured by Rigaku Equipment Co., Ltd.

(Average particle size of the fine particles)
The average particle size of the present fine particles is the same as the particle size of 100 randomly extracted fine particles, a transmission electron microscope (Hitachi Ltd., H-9000) or a scanning electron microscope (Hitachi Ltd., S-). 900), and the average particle size was determined.

(Thickness of conductive film and copper plating)
The thickness of the conductive film was measured by using DEKTAK3 (manufactured by Veeco metrology group).
Moreover, when measuring peeling strength, the thickness of the copper plating formed on the electrically conductive film was measured using the Digimatic standard outside micrometer (made by Mitutoyo Corporation).

(Volume resistivity of conductive film)
The volume resistivity of the conductive film was measured using a four-probe resistance meter (model: lorestaIP MCP-T250, manufactured by Mitsubishi Yuka Co., Ltd.).

(Adhesion)
The adhesion between the conductive film and the polyimide film was determined by the peel strength.
The peel strength was measured by a method specified in JIS C6471 using a small tabletop testing machine EZTest series manufactured by Shimadzu Corporation.

[Example 1]
In a glass container, 5 g of copper (II) chloride dihydrate was dissolved with 150 g of distilled water to obtain an aqueous solution containing copper ions. The pH of the aqueous solution was 3.4.
To this aqueous solution, 90 g of 40% by mass citric acid aqueous solution was added and stirred for a while to adjust the pH of the aqueous solution to 1.7.
A solution prepared by mixing 5 g of an amino compound (manufactured by Enomoto Kasei Co., Ltd., Disparon 1860, amine value 11 mgKOH / g) and 10 g of terpineol (boiling point 219 ° C., solubility 0.5 g (20 ° C.) in 100 g of water) with the aqueous solution. In addition, they were vigorously stirred to form a suspension.

While stirring the suspension, 150 g of a 3% by mass aqueous sodium borohydride solution was slowly added dropwise to the suspension.
After completion of dropping, the suspension was allowed to stand for 1 hour to separate into an aqueous layer and an oil layer, and then only the oil layer was recovered. A black conductive film forming ink in which fine particles were dispersed in terpineol was obtained. When the ink was left for 1 day, the ink remained black.

When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles.
The particle diameter of the fine particle powder obtained by drying the ink was measured. The average particle size was 10 nm.
The concentration of copper hydride fine particles in the ink was 20% by mass.

Using a SHOTMASTER 300 manufactured by Musashi Engineering Co., Ltd., 0.5 g of ink left for one day was applied to the surface of a polyimide film having a thickness of 125 μm in a desired wiring pattern by a dispensing method to form a coating film.
A printed wiring board on which a conductive film having a desired wiring pattern is formed by placing a polyimide film with a coating film in a baking furnace and baking at 350 ° C. for 1 hour in a nitrogen gas atmosphere having an oxygen concentration of 40 ppm. Got. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.

Copper plating was performed on the conductive film of the printed wiring board using a copper sulfate plating solution. Plating conditions, voltage 1.1V, it was a current density of 3.5A / dm ^2. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 2]
The ink for forming a conductive film obtained in Example 1 was refluxed with nitrogen at 150 ° C. for about 1 hour. After 1 hour, the dispersion was cooled and recovered when the temperature reached 25 ° C. or lower. When the fine particles in the dispersion were collected and identified by X-ray diffraction, it was confirmed to be metallic copper fine particles.
The particle diameter of the fine particle powder obtained by drying the ink was measured. The average particle size was 11 nm.
The concentration of metal copper fine particles in the ink was 22% by mass.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 3]
The ink for forming a conductive film was prepared in the same manner as in Example 1 except that Disparon KS873N (amine value 120 mgKOH / g) manufactured by Enomoto Kasei was used instead of Disparon 1860 (amine value 11 mgKOH / g) manufactured by Enomoto Chemical. Obtained. When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average particle diameter of the copper hydride fine particles was 11 nm.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 4]
Example 1 except that Disperbyk-130 (unsaturated polycarboxylic acid polyaminoamide, amine value 190 mgKOH / g) manufactured by Big Chemie Japan was used in place of Disparon 1860 (amine value 11 mgKOH / g) manufactured by Enomoto Kasei Co., Ltd. In the same manner, an ink for forming a conductive film was obtained. When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average particle diameter of the copper hydride fine particles was 11 nm.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 5]
For forming a conductive film in the same manner as in Example 1 except that tetradecane (boiling point 253 ° C., insoluble in water) was used instead of terpineol (boiling point 219 ° C., solubility in water 100 g (20 ° C.)). Ink was obtained. When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average particle diameter of the copper hydride fine particles was 10 nm.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 6 (comparative example)]
Ink for forming a conductive film in the same manner as in Example 1 except that Hinoact KF1000 (amine value 0 mgKOH / g) manufactured by Kawaken Fine Chemical Co., Ltd. was used instead of Disparon 1860 (amine value 11 mgKOH / g) manufactured by Enomoto Kasei Co., Ltd. Got. When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average particle diameter of the fine particles was 10 nm.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 7 (comparative example)]
Instead of terpineol (boiling point 219 ° C., solubility 0.5 g (20 ° C.) in 100 g of water), xylene (boiling point 139 ° C. (m-xylene), solubility in 100 g of water 0.02 g (20 ° C.)) was used. Except for the above, an ink for forming a conductive film was obtained in the same manner as in Example 1. When the fine particles in the ink were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average particle diameter of the copper hydride fine particles was 10 nm.

A printed wiring board was obtained in the same manner as in Example 1 except that the ink was used. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the conductive film with plating and the peel strength between the conductive film with plating and the polyimide film were measured. The results are shown in Table 1.

[Example 8]
A printed wiring board was obtained in the same manner as in Example 1 except that a glass substrate was used instead of the polyimide film. The thickness of the conductive film was 1 μm. The volume resistivity of the conductive film was measured. The results are shown in Table 1.
Copper plating was performed on the conductive film of the printed wiring board in the same manner as in Example 1. The thickness of the copper plating was 20 μm. The volume resistivity of the plated conductive film and the peel strength between the plated conductive film and the glass substrate were measured. The results are shown in Table 1.

  According to the conductive film forming ink of the present invention, a conductive film having a desired wiring pattern can be formed without using a mask film, and a printed wiring board can be manufactured with few steps. Moreover, according to the ink for forming a conductive film of the present invention, a printed wiring board having a conductive film excellent in adhesion to an electrical insulator layer containing polyimide can be produced.

It is sectional drawing which shows an example of a printed wiring board.

Explanation of symbols

10 Printed Wiring Board 12 Electrical Insulator Layer 14 Conductive Film

Claims (1)

A conductive film forming ink for forming a conductive film on the surface of an electrical insulator layer containing polyimide,
A water-insoluble organic solvent having a boiling point of 150 to 350 ° C. at a pressure of 0.1 MPa;
Metal fine particles and / or metal hydride fine particles dispersed in the organic solvent;
An amino compound amine value according to the provisions of JIS K7237 is 40 ~ 120 mgKOH / g seen including,
The ink for forming a conductive film, wherein the amount of the amino compound is 1 to 50 parts by mass with respect to 100 parts by mass of the total of metal fine particles and metal hydride fine particles .

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